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This book gathers together papers presented at the 26th IAVSD Symposium on Dynamics of Vehicles on Roads and Tracks, held on August 12 – 16, 2019, at the Lindholmen Conference Centre in Gothenburg, Sweden. It covers cutting-edge issues related to vehicle systems, including vehicle design, condition monitoring, wheel and rail contact, automated driving systems, suspension and ride analysis, and many more topics. Written by researchers and practitioners, the book offers a timely reference guide to the field of vehicle systems dynamics, and a source of inspiration for future research and collaborations.

### Correction to: Analysis on Operation Safety of Express Freight Trains in Subgrade-Bridge Transition in Crosswind Environment

The original version of this chapter was published with an incorrect Acknowledgment number, which has now been corrected to “2017YFB1201302-12A”.

Jingcheng Wen, Zhenggang Lu, Qi Huang

### The ‘FORESEE’ Prototype, Fully Active, Steered Two Axle Railway Vehicle

This paper reports on a novel project to develop a fully active, two axle railway vehicle which could provide reduced track forces and noise and improved ride comfort compared with existing vehicles. Computer simulations have been used to tune the suspension components and control systems to ensure good passenger comfort and safe operation even in failed control cases. A prototype of the vehicle has been constructed and tested on a full size roller rig. The test results confirm the computer simulations and demonstrate that for speeds up to 200 km/h and in all failure modes the vehicle was stable and with low track forces and high stability and passenger comfort.

Simon Iwnicki, Per-Anders Jönsson, Jörgen Gustafsson, Johan Englund, Sebastian Stichel, Martin Pemberton

### Control of Railway Wheelsets – A Semi-active Approach

This paper presents a detailed study of semi-active approach for railway wheelsets. A number of control strategies for active primary suspensions for both solid axle wheelset and independently rotating wheelsets are examined in detail and the key requirements of energy flows on both curved and straight tracks are investigated. A semi-active control scheme is then proposed for the independently rotating wheels and a comprehensive performance evaluation is provided to demonstrate that the proposed semi active control system can be used to continuously and reliably provide the necessary steering control without the need for the energy injection of full active control.

T. X. Mei, Atousa Zaeim, Hong Li

### A Direct Control Approach for Automatic Steering and Stability of Motorized Independently-Rotating Wheels

A simple control solution to realize the automatic steering and stability of the motorized independently-rotating wheel (IRW) configuration is proposed in this paper. Associated with a prototype of a two-axle vehicle, an active control strategy is developed to improve the dynamic behavior of the IRW system, especially the steering performances in curve negotiation. The simulation results demonstrate a significant reduction in the wheel/rail interaction without leading to instability issues owing to the proposed control approach.

Xiaoyuan Liu, Roger Goodall, Simon Iwnicki

### Controlling a Rail Vehicle with Independently-Rotating Wheels

A conventional rail vehicle has a purely mechanical suspension consisting of springs and dampers. Their performance is determined mainly by spring stiffnesses, damper coefficients and the sprung and unsprung masses. As a result, the guidance forces generated at the wheel-rail contact are not optimised for a particular track curvature or profile. This leads to a contradictory requirement for a stiff suspension for guidance and a softer suspension for steering, and conventional vehicles have to be designed for a wide range of operating regimes. Active suspensions to influence the running gear of a rail vehicle have been studied widely [1] and proposed as a solution to overcoming the inherent suspension design conflict between stability and guidance. Some of this research has suggested that an active vehicle with independently-rotating wheels (IRWs) will provide the best solution in terms of vehicle performance and lower actuation requirements [2]. This paper takes this research further by designing and implementing a robust controller for IRWs on a multi-body physics simulation (MBS) model of a British Rail Class 230 D-train with modified bogies.

Nabilah Farhat, Christopher Ward, Omar Shaebi, David Crosbee, Julian Stow, Ruichen Wang, Roger Goodall, Martin Whitley

### Research on Railway Vehicle Stability Control Utilizing Mass Inertia Method

A new control method is proposed to enhance the stability of railway vehicles with additional mass without modification of the bogies. Two mass are set on the bogie and controlled by actuators. Each of the mass has a lateral degree of freedom relative to the bogie. The motion of two mass used to suppress the lateral and yaw vibration of the bogie respectively. The control algorithm is designed based on full-state feedback control theory and optimal control theory. A dynamic model is established and analyzed on MATLAB/Simulink. The control method is analyzed in both time-domain and frequency-domain. The results show that the critical speed of the bogie is enhanced. The dynamic performances of the vehicle are also improved in all speed range.

Gang Shen, Qin Li

### Application of State Estimators in Active Control of Railway Wheelsets

This paper presents the development of a state observer for the estimation of output torque of an electromechanical actuator in the application of active wheelset control for railway vehicles. The output from the state estimator is essential to ensure that actuator responds appropriately and deliver accurate and fast control effort as demanded to maintain the stability of wheelsets. The formulation and design of the observer is based on the use of the actuator model only, so that it reduces substantially the complexity and difficult uncertainties related to the model of a full rail vehicle. The performance and robustness assessments of the state estimator integrated active control system are carried out with the use of a full bogie vehicle model.

Lushan Weerasooriya, T. X. Mei, Hong Li, Y. Luo

### Gain Scaling for Active Wheelset Steering on Innovative Two-Axle Vehicle

Within the Shift2Rail project Run2Rail, an innovative single axle running gear with only one suspension step is proposed. A composite material frame shall be used both as structural and as suspension element. To improve curving performance active wheelset steering control is introduced. The selected control aims to minimize the longitudinal creepage by controlling the lateral wheelset position on the track. A two-axle vehicle is created in the MBS program SIMPACK and co-simulation is established with Simulink. The control strategy used is a simple PID control. A set of run cases with different curves and speeds is selected to verify the performance. The control gain optimal for high non-compensated lateral acceleration (NLA) tends to produce unstable results for low speeds. Control gain scaling is introduced based on vehicle speed and online estimation of the curvature. The proposed gain scheduling approach maintains the simple control formulation still solving the instability problem. Gain scheduling allows use of optimal control gains for all combinations of curve radii and vehicle speed and thereby taking the full advantage that the active wheelset steering brings to a vehicle with single axle running gears.

Rocco Libero Giossi, Rickard Persson, Sebastian Stichel

### The Development of Stiffness-Adjustable Anti-yaw Damper

It has been known that the high speed passenger car is likely subjected to the carbody hunting and the bogie instability owing to the different wheel/rail conditions. Carbody hunting always be occurred in low wheel/rail conicity after wheel re-profiling procedure and the bogie hunting can be occurred in the increased wheel/rail conicity in the service. These could impose highly adverse influence on the ride comfort of passengers and wheel/rail safety. A stiffness-adjustable anti-yaw damper integrating a FSS (Frequency Selective Stiffness) valve has thus been developed to enhance the adaptive of vehicle to both the low and high wheel/rail conicity service conditions. The damper laboratory test is undertaken to obtain its characteristic curve, which is further used in the vehicle dynamic model to investigate the influences of stiffness-adjustable anti-yaw damper. To better characterize the influence of the stiffness-adjustable anti-yaw damper, a roller rig test is further performed to compare the FSS yaw damper with other two conventional yaw dampers. The numerical and experimental results suggested that the FSS damper can achieve better adaptive to both low and high wheel/rail conicity with respect to other two conventional yaw dampers. In the low frequency range, the FSS yaw damper can yield relatively low stiffness so as to suppress the car body hunting for the low wheel/rail conicity condition, while it can also provide high stiffness in the high frequency range to improve the bogie stability for the high wheel/rail conicity condition.

Wenbiao Huo, Bingshen Yue, Xuegang Liu, Nan Jia, Feng Zhao, Shuo Zhang

### A Dedicated Control Design Methodology for Improved Tilting Train Performance

The development of detailed multibody models of railway vehicles is essential to address industrial problems through computational tools. The assessment of vehicle dynamic performance is one of the studies that can be performed with a multibody software. But when tilting trains are considered, which comprise active suspension elements, control engineering theories are required to estimate the forces developed by the actuators. Despite its importance, in general the details about the tilting control algorithm are unknown. In this work, a dedicated control design methodology is proposed to estimate the control algorithm of a tilting system in order to assure a proper vehicle performance. For this purpose, a detailed multibody model of a tilting train is used to perform a batch of simulations in order to develop an accurate linear model of the tilting system and to study its performance in realistic operation conditions. Thus, the traditional control techniques can be used to assess the tilting system dynamics and to design the control algorithm so that proper tilting performance is ensured. The control algorithm and the tilting performance are tested on a curved and tangent track with track irregularities. The comfort indexes PCT and RMS are used here to assess the tilting system.

Hugo Magalhães, Pedro Antunes, João Pombo, Jorge Ambrósio

### Scaled Roller Rig to Assess the Influence of Active Wheelset Steering on Wheel-Rail Contact Forces

The CTU roller rig is 1:3.5 scaled test rig that serves mainly as a tool for experimental verification of mathematical simulations and demonstration of the possible benefits of using active controlled elements in railway bogies. Currently it is involved in the development of a system of active wheelset steering for an electric locomotive. The goal of this system is to reduce forces in the contact of wheels and rails in a curved track. This project necessitated the further development of the CTU roller rig, particularly needed were the capability to apply the centrifugal force on the test bogie, and the capability to measure forces in the wheel-roller contacts and forces transmitted between the bogie-frame and axle-boxes. These requirements led to the design of a new rig mainframe that tilts around the longitudinal axis and instrumentation of the rollers and test bogie components by strain gauge bridges. The systems of measuring the forces in the wheel-roller contacts and the axle-box forces have been calibrated, implemented on the rollers and the experimental bogie and successfully tested. The new roller rig mainframe and components of the tilting mechanism are currently in the production. The paper describes in detail recent design changes of CTU roller rig, their implementation and testing.

Jan Kalivoda, Petr Bauer

### Fault-Tolerant Analysis for Active Steering Actuation System Applied on Conventional Bogie Vehicle

Active steering system can drastically improve dynamic behaviors of the railway vehicle but will also introduce safety-critical issues. The fault-tolerant analysis therefore is essential for the design and implementation of this technology. In this work, an approach based on Risk Priority Number from Failure Mode and Effect Analysis is established to present quantitative assessment for fault tolerance of actuation system. This method is adopted to compare proposed nine different active steering schemes where two different hydraulic actuators are considered, and additional passive spring or redundant structure is implemented as back-up to ensure the safety. In case studies, the impacts of typical failure modes are investigated through multi-body simulation and quantified by Severity factor. Finally, the fault tolerance of different actuation schemes is compared by RPN values.

Bin Fu, Stefano Bruni

### Track Condition Monitoring Based on Car-Body Acceleration Using Time-Frequency Analysis

A track condition monitoring system that uses a compact on-board sensing device has developed and applied for track condition monitoring of regional railway lines in Japan. This study describes the application of time-frequency analysis for condition monitoring of railway tracks from car-body acceleration measured in in-service train. Simulation studies and field test results showed that Hilbert-Huang transform (HHT) gives good time-frequency resolution and intrinsic mode functions give the detail information of track faults.

Hitoshi Tsunashima

### On-Board Wheel Profile Classification Based on Vehicle Dynamics - From Physical Effects to Machine Learning

Composite brake blocks often cause hollow worn wheel profiles of freight wagons. The resulting shorter maintenance inspection intervals could be elongated if the wheel profile conditions can be estimated via on-board monitoring systems in service. On the one hand such on-board monitoring algorithms must be very accurate and on the other hand very robust against unknown influencing effects. This paper shows the process from understanding the physical effects by studying the wheel rail contact conditions of new and worn profiles under several operating conditions up to the application of machine learning algorithms for a robust classification of the wheel profile states. In the first step, the physical effects are investigated by varying different operating conditions with a multi body dynamics model of a freight wagon. In the second step, this generated knowledge is used to find suitable features of measured vehicle response quantities to classify new and worn wheel profiles with machine learning algorithms. In the third step, the accuracy of classification results is analysed for different states of available track information like track irregularities or rail profile conditions.These investigations show very promising results due to a high accuracy of the developed methodology based on machine learning algorithms. Based on the knowledge of the physical effects, these pre-trained algorithms will be verified with measurement data collected in the Shift2Rail project FR8RAIL II.

Bernd Luber, Felix Sorribes-Palmer, Gabor Müller, Lorenz Pietsch, Klaus Six

### Condition Monitoring of Rail Vehicle Suspension Elements: A Machine Learning Approach

With an increasing demand for safe and efficient rail transportations with high availability, there is an interest to apply condition based maintenance on railway systems to increase the total system reliability. A condition based maintenance system utilizes data collecting, data processing and decision making to schedule maintenance based on the actual condition of components. In this paper a rail vehicle is simulated at varying operational conditions, and with degraded dampers in the primary and secondary suspension. A large database of simulations is generated and is used to train and test classification algorithms to detect upcoming damper faults, introduced as a fault factor multiplied with the damper coefficients. Frequency response functions between accelerometer signals in the carbody, bogieframes and axles are used as fault indicators, predictors, fed to the classification algorithms. The algorithms are evaluated for a varying number of included frequency response functions, as well as varying operational conditions in the training datasets. The linear Support Vector Machine and 1-Nearest-Neighbour classifier both indicate high capability of correctly classifying damper degradations.

Henrik Karlsson, Alireza Qazizadeh, Sebastian Stichel, Mats Berg

### Parameter Identification for Railway Suspension Systems Using Cubature Kalman Filter

Predictive maintenance is one of the technology enablers in the railway industry to get rid of fixed service intervals and switch to maintenance on demand to reduce life cycle costs. Until now inspection intervals on regular basis lead to high costs to ensure the overall goal of high availability. To strengthen the condition-triggered maintenance this work presents a cubature Kalman filter approach for parameter identification of complex railway suspension systems. In detail, the approach is designed for the identification of the spring stiffness and damping coefficient of the secondary suspension system using measurements from real world operation. The parametrization of the filter is performed in a way that the filter shows a so called consistency property which ensures a statistical correct behaviour. Furthermore the cubature Kalman filter approach shows promising properties regards computational complexity in combination with the achievable accuracy.

Selma Zoljic-Beglerovic, Bernd Luber, Georg Stettinger, Gabor Müller, Martin Horn

### A Novel Method for Railway Crossing Monitoring Based on Ambient Vibration Caused by Train-Track Interaction

Railway crossings are critical components in the rail network. They usually degrade faster than the other components. It is therefore vital to monitor their conditions using appropriate methods. This paper proposes to use the ambient vibration caused by the train-track interaction from a distance to monitor the condition of railway crossings. Both impact tests and pass-by measurements were performed on an instrumented crossing. The eigenfrequencies and mode shapes in the frequency range of 10–2000 Hz are first identified by impact tests using three different devices, i.e. a falling weight device, a big hammer and a small hammer. For the pass-by measurement, the dynamic features of both the wheel-crossing impact and ambient vibration are analyzed using time-frequency representations. It is shown that the ambient vibration signals are stationary and contain several characteristic frequencies. Then a method based on the frequency domain decomposition is applied to the ambient vibration signals to further identify the frequency components. It is found that the frequencies identified from the pass-by measurement agree well with the eigenfrequencies identified from the impact test. The proposed method can be further developed to continuously monitor the condition of railway crossings without interrupting train operations.

Chen Shen, Zili Li, Rolf Dollovoet

### Integrated Tool for Assessment of Performance of Railway Crossings

The paper presents an integrated (experimental and numerical) tool for analysis of crossing performance in railway turnouts.

Jeroen J. J. Wegdam, Xiangming Liu, Valeri L. Markine

### Damage Detection of Rail Fastening System Through Deep Learning and Vehicle-Track Coupled Dynamics

Owing to the rapid development of the rail transportation, the health monitoring of the track structure becomes a challenging problem. This article presents a novel approach to carry out damage detection and localization of fastening systems along the rail based on deep learning and vehicle-track coupled dynamics analysis. A convolutional neural network (CNN) is designed to learn optimal damage-sensitive features from the rail acceleration response automatically and identify the damage location of fastening systems, leading to a high detecting accuracy. The vehicle-track coupled dynamics model incorporating different damage level of fastening systems is adopted to generate labeled dataset to train the proposed network. The advantage of this approach is that CNN learns to extract the optimal damage-sensitive features from the raw dynamical response data automatically without the need of computing and selecting hand-crafted features manually. T-SNE is applied to manifest the super feature extraction capability of CNN. Thereafter, the trained network is estimated on the testing dataset to validate its generation capability. The results reveal a good performance of the proposed method.

Zhandong Yuan, Shengyang Zhu, Wanming Zhai

### A Study on the Correlation Between Measured Track Irregularities and Vehicle Responses in High-Speed Lines

In this study, a correlation analysis is conducted between measured track irregularities and vehicle responses. For this purpose, four track irregularity types, namely track gauge, longitudinal level, super-elevation and track alignment, and the vertical/lateral acceleration of carbody are recorded using high-speed comprehensive inspection train. The results indicates that vertical carbody acceleration is dominated by the irregularity of longitudinal level, and can be affected by the irregularity of super-elevation (with the wavelengths above 50 m). The lateral carbody acceleration is largely influenced by the irregularity of track alignment (with the wavelength above 30 m) and super-elevation (with the wavelength above 10 m). Yet, vehicle responses are seldom influenced by the irregularity of track gauge. Using transfer function, VCA can be well predicted at the wavelengths above 10 m, and LCA can be well predicted at the wavelengths above 50 m.

Xiubo Liu, Shuai Ma, Zilong Wei, Bo Zhang

### Diagnostics of Freight Cars Using On-Track Measurements

The paper considers the possibilities of freight car diagnostics using wheel-rail forces measured on the track. The proposed method of spring suspension sufficient damping detection uses the data on vertical and lateral track force that are measured on track section with specific irregularities. The sensor arrangement system for such measurements is theoretically justified and gives the additional advantage of detecting defects over the entire wheel tread length.

Yuri P. Boronenko, Galina A. Povolotskaia, Rustam V. Rahimov, Yurii B. Zhitkov

### Condition Stages Identification for Railway Crossing Monitoring System

In the structural health monitoring for railway crossings, identifying the condition stages of the crossing elements is an important step for the crossing condition assessment. This paper presents the condition stages identification procedure using the multi-body system method. This study is carried out on the 1:9 crossings that are most commonly used in the Dutch railway and suffering a lot from damages. By introducing different types of damage into the vehicle-crossing model and compare the dynamic responses with the measurement results, the condition stages of the monitored crossing can be identified. The simulation results show that the development of vertical irregularity and clip damage are clearly reflected on the change of wheel-rail contact force and the rail vertical acceleration. The findings of this study can be further applied in the structural health monitoring (SHM) system for railway crossings developed by TU Delft.

Xiangming Liu, Valeri L. Markine

### Sensitivity Analysis of Flexible Upper Frame of Pantograph with a Novel Simplified Method

Optimization design for pantograph-catenary system is of great significance to keep the good current collecting quality. As the main parameters of pantograph’s upper frame, stiffness and damping need to be well designed, especially in the high speed operation condition. Based on the relative coordinate theory in multibody dynamics, this paper proposed a new simplified method to simulate the flexible characteristic of the upper frame in pantograph-catenary interaction. In this method the upper frame is divided into several segments, which are articulated with torsion springs. The flexibility change of the upper frame is described by the key parameter variation of these torsion springs. In the pantograph-catenary coupling system, finite element method (FEM) is applied to establish the model of catenary, Hertz contact theory is adopted and the standard deviation (STD) of the contact force is used as an evaluation index. Sensitivity of the upper frame’s flexibility to current collecting quality is given, which will effectively support for the structural design and material selection of the upper frame of pantograph adapting to different train operation speeds.

Jiangwen Wang, Guiming Mei, Weihua Zhang

### Study on Simulation Method of Pantograph-Catenary System Considering Ice Coating

The icing problem of catenary is becoming more and more prominent with the expansion of the distribution range of rail transit lines. Ice coating on catenary will affect the sliding of pantograph and the power supply quality of train. In serious cases, the phenomenon of arc tension between catenary and pantograph will also occur, which threatens the normal operation of trains. The equivalent density method and the uniform load method of icing are studied to analyze the icing problem of pantograph-catenary system. The similarities and differences between the two simulation methods are compared. The pantograph-catenary dynamics simulation analysis is carried out based on the multi-rigid body model of pantograph. The results show that the icing of catenary will affect the current collecting quality of pantograph-catenary system. The difference between the two models in calculating the dynamic response of pantograph-catenary system after icing becomes obvious with the increase of icing thickness, and the mechanism of the difference is analyzed.

Yongming Yao, Dong Zou, Jiangwen Wang, Ning Zhou, Weihua Zhang

### Analysis of the Current Collection Quality of the Variable Speed Zone of the Pantograph-Catenary System

There are many variable speed zone during train operation. Meanwhile, the curved zone also is an important zone when the train passing by and the train will slow down. However, rarely research on quality of the current collection in variable speed zone. This paper based on Multi-body dynamics and Optimal Energy saving theory, establishing a rigid catenary model and Multi-rigid body of pantograph, studying the influence of the acceleration on the variable speed zones and the optimal quality of current collection as the target function, seeking a set of optimal accelerations.

Jiangyang Qiu, Guiming Mei, Weihua Zhang, Jiangwen Wang, Mengying Tan, Zhong Huang, Wei Qiao

### Influence of Key Parameters on High Speed Overhead Conductor Rail and Pantograph System

The Sichuan-Tibet railway line, where overhead conductor rail (OCR) system is considered to be utilized in tunnels, has a design speed of up to 200 km/h, which is much higher than conventional OCR lines, whereas literature related to the high speed OCR system is limited. Finite element model of OCR is developed based on absolute nodal coordinate formulation, and a linearization process is applied on the model to reduce computational time. Then influence of key parameters on OCR system when operating at 220 km/h (10% for design margin) is analyzed based on the linearized model. Span length, bending stiffness and linear density are revealed to be sensitive parameters when designing a high speed OCR with better performace. Some special span length configurations which leads to worse performance are pointed out. Then influence of contact wire irregularities is analyzed and it is found that irregularities of specific wavelengths result in worse performance than others. Some suggestions about design and maintenance of OCR system are given in the end of this paper.

Long Chen, Zhigang Liu, Jing Zhang, Zeyao Hu

### Study on the Characterization of Degraded Catenary in Sweden to Enhance Safety and Reliability

Sweden has many catenary systems designed to be used for 40–60 years. Normally they can meet basic operational requirement within this period, but after a long time in service the catenary structures get weakened. Today there are about 40 incidents on catenary breaking each year, which leads to disastrous consequences to the railway network. The significant dynamic interaction of the pantograph-catenary system, together with mechanical wear, chemical corrosion, thermal softening, environmental disturbances, multiple-pantograph operation and increased traffic volume, can significantly weaken the physical strength of the catenaries and result in fatigue and structural damage. To reflect the catenary degradation, a study on the catenary dynamic-fatigue is performed with some factors considered, e.g. material softening due to high temperature and annealing, and cross-section losses due to wear, structural defects and small damages. This study finds that among all Swedish catenary systems the soft catenary system SYT 7.0/9.8 is relatively weak and its messenger wire is the most vulnerable component. The results show that the dynamic tensile load is dependent on position and operational speed. The weakened material strength due to high temperature and annealing have the main responsibility for the system failures. In the end, this paper suggests that, besides the regular visual inspections to the catenary structure, it is necessary to measure and control the degradation of physical strength of the key components to ensure safety and reliability in operation and also to extend the catenary service life.

Zhendong Liu, Sebastian Stichel, Peter Larsson, Jan Hjort

### Semi-active Dampers for Multiple Pantograph Operation

Multiple pantograph operation is an unfavourable condition for current collection, since the trailing pantograph is subjected to high vibrations and elevated contact force variations, due to the perturbation induced on the overhead line by the leading pantograph. In a previous work it was shown that a diversification of preloads of front and rear pantographs, achievable using pressure regulation systems driven by electronic units, can have beneficial effects on current collection quality of the trailing pantograph. This paper investigates the concepts of differentiating the leading and trailing pantograph damping, and of varying the pantograph damping as a function of speed. A plan of numerical simulations is first performed considering a number of permutations of leading and trailing pantograph damping values, obtaining a map of optimal damping values for different train speeds. The numerical model of an electro-hydraulic damper, able to adapt its damping parameter is then proposed and integrated in the PCaDA model for the simulation of the dynamic interaction between pantograph and catenary. The numerical results corroborate the idea that the regulation of damping values as a function of train speed and orientation would allow improving the system performances and extending the operating speeds.

Stefano Bruni, Marco Carnevale, Alan Facchinetti

### A Galerkin Approach for Modelling the Pantograph-Catenary Interaction

The pantograph-catenary interaction was modelled for high-speed electric and hybrid trains. A lumped-mass pantograph model was used and the overhead wires were modelled as Euler-Bernoulli beams. Each vertical and horizontal wire deflection was decomposed into an infinite series of spatial basis functions, which were chosen to be the eigenmodes of the Euler-Bernoulli PDE, and corresponding time functions. The boundary conditions were used to evaluate the spatial basis functions and reduce the PDEs to ODEs in terms of the time functions. Elimination of variables was used to remove the algebraic contact constraints and reduce the overall index-three DAE to an ODE. This linear, time-varying ODE was solved by integration and the elimination process was reversed in order to recover the original states. The Simulink model was validated against the 2002 and 2018 European Standards, BS:EN 50318:2002 and BS:EN 50318:2018 respectively. In both cases, the model produced accurate results with exceptional simulation speeds.

John Martin, Stephen Duncan

### Influence of Rail Corrugation on Fatigue Life of Bogie Frame of High-Speed EMU

In order to evaluate the influence of rail corrugation on the fatigue life of bogie frame of high-speed EMU, a vehicle system dynamics model considering rigid-flexible coupling was established considering flexibility of bogie frame. The dynamic stress of the key part of bogie frame was obtained on the measured track irregularities in the presence of rail corrugation. Fatigue life of key parts of bogie frame was predicted according to modal superposition method and nominal stress method. The results show that the rail corrugation will increase the fatigue cumulative damage of the key parts of bogie frame and shorten its overall service life. Structural fatigue damage due to rail corrugation should be taken into consideration when designing bogie frame structure of high-speed EMU. Structural optimization design of key parts of bogie frame should be conducted based on vibration fatigue life prediction.

Baoan Zhang, Jing Zheng, Dalian Yu, Jimin Zhang, Hechao Zhou, Xin Liang, Wenqiang Qu

### Investigation of Relationship Between Initial Setting of Leveling Valves and Air Spring Pressure of a Railway Vehicle When Assuming the Centrifugal Force Action

The wheel load balance of a railway vehicle could vary according to whether it is before or after the curve passage. The variation is influenced by the leveling valve (LV) that has a dead zone of air supply and exhaust. The purpose of this research is to clarify the mechanism of the wheel load variation due to the dead zone of the LVs. In this paper, we assume the situation where the lateral force is loaded and unloaded on the car body. The simulation and experimental results show that the diagonal difference in LV rod lengths and the maximum lateral force are related to the air spring pressure variation.

Takatoshi Hondo, Takayuki Tanaka

### An Experimental Study on the Performance of Guard Angle of Meter-Gauge Track During an Earthquake

In this paper, the characteristics of the guard angle at earthquakes are clarified through the actual bogie oscillation test, which is generally placed in sharp curves for meter-gauge railways. It is confirmed that the plastic deformation of the guard angle can occur when the contact force acting between the wheel and the guard angle exceeds about 50 kN. In addition, it is clarified that the guard angle maintains its performance designed for preventing derailment even if it receives the short-time impact force which is observed during an earthquake. Furthermore, the positive effects of the guard angles on the derailment prevention of the meter-gauge trains during earthquakes are clarified using numerical simulations.

Kohei Iida, Masahito Kuzuta, Yukio Nishiyama, Takayuki Tanaka, Takatoshi Hondo

### Influences of Infrastructure Property on the Train-Track Interaction Due to Track Irregularities

The paper presents a study of the dynamic behavior of a high-speed train-track-bridge system during the train crossing multi-span concrete box girder bridges due to track irregularities. A coupled finite element–multibody dynamics (FE-MBS) model including the train sub-model, the ballastless track sub-model, the wheel-rail contact sub-model and the bridge sub-system are formulated. This model can predict the behavior of the train running on tracks supported by bridge and embankment, as well as the dynamic response of track and bridge structures under train passage. The effects of the wavelengths of track defects on the running quality of train travelling on bridge and embankment are reported. The simulation results show that severe track irregularities such as track vertical profile and alignment defects can arouse the resonance of the vehicle-track-bridge system, and the safety limits for the track defects on bridge should be stricter than that on embankment.

Chao Chang, Liang Ling, Wanming Zhai, Kaiyun Wang

### Analysis on Operation Safety of Express Freight Trains in Subgrade-Bridge Transition in Crosswind Environment

Nowadays, the express freight trains develop rapidly, and their load capacity is large and the running speed is high. Due to the bad aerodynamic performance of the car body, operational safety accidents are prone to occur under strong crosswind environments. At present, there is less analysis on the operation safety of express freight trains entering the subgrade-bridge transition under the crosswind. This paper establishes the dynamic model of the express freight trains entering the bridge-subgrade transition under the crosswind environment, and analyzes the influence rule of the crosswind speed, the operating speed of the train, the variation of the stiffness of the subgrade-bridge transition, and the bending deformation of the rail caused by the post-construction settlement of the road and bridge structure. The results show that under the crosswind environment, the vertical force of the wheel and rail increases obviously when the train enters the bridge-subgrade transition. The crosswind speed and the deformation of the rail caused by the cross the post-construction settlement of the bridge structure is the main factor affecting the operation safety of the train.

Jingcheng Wen, Zhenggang Lu, Qi Huang

### Investigation on Running Safety of Empty Wagons in Long Freight Train Passing a Worn Switch Rail

According to the field investigation of a climb derailment accident occurred at a switch rail area, the measured switch rail profiles are employed to establish a wagon-switch rail interaction model. Based on the numerical simulations, the characteristics of the wagon-switch rail interaction were studied. Meanwhile, the influences of the train speed, the coupler force and the coupler yaw angle on the running safety of the middle wagon of the 3-pack freight train were investigated. The simulation results indicate that fierce impacts occur in the transitional area between the stock rail and the switch rail accompanied with instantaneous wheel-rail separation. The wheel-rail interactive forces increase rapidly with an increase in the train speed, and the vertical interaction is fiercer than that in the lateral direction under the coasting condition. The synthetic effect of large lateral component of coupler force and variable cross-sections of switch rail can intensify the lateral wheel-rail interaction, and increases the operating risks of wagons. To enhance the running safety of the empty wagons in switch area, the train operation regulation should be optimized to reduce the longitudinal impulse, and the maintenances of the track structure and wagons should be strengthened to improve the running stability of the wagons.

Xin Ge, Kaiyun Wang, Liang Ling, Lirong Guo, Kun Zhou

### Scenario Substructure Method (SSM) for Simulation of Long Trains

The simulation of long trains is a great challenge, especially if all vehicle and infrastructural properties are to be considered in detail. As part of a derailment investigation, a method was developed which uses the principle of superposition of mechanics to separate the longitudinal dynamics from vertical and lateral dynamics in train simulations, the so-called Scenario Substructure Method (SSM). In the first phase, the longitudinal dynamics of the entire train is calculated using simple models, while in the second phase the superposition of the vertical and lateral dynamics is carried out with complex models. Thus, the simulation of the accident (until the derailment occurs) can be split into two phases. The presented Scenario Substructure Method describes a procedure in which the computational effort can be substantially minimized and variant calculations with a few detailed models are possible. The starting point for the development of the Scenario Substructure Method is the task of simulating the derailment of a long freight train consisting of 48 single wagons in a switch due to an initiated emergency braking. This paper uses the example of the freight train accident to apply the Scenario Substructure Method. The different possibilities of the superposition are compared and evaluated. Furthermore, an estimation of the effort reduction for the simulation calculations is carried out and compared to a detailed modelling.

Sönke Lück, Rolf Naumann

### Dynamic Behavior of a High-Speed Train Subjected to Earthquake and Emergency Braking

The running safety of high-speed trains during earthquakes is an issue of great research interest. But the effects of emergency braking action on the dynamic behavior of high-speed trains under earthquakes is still unknown. This paper presents a study of the running safety of a high-speed train under the combined effects of a strong earthquake and the train emergency braking. A numerical model considering the earthquake impacts, the train braking action and the train-track interaction is formulated. The dynamic response and derailment behavior of a high-speed train subjected to a strong earthquake and an emergency braking is investigated. The effects of the seismic load, the braking force, and the wheel-rail interface condition are reported. The results show that an excessive braking torque could decrease the lateral stability and increase the derailment potential of the high-speed trains under large earthquake. This study is shown to enhance the understanding of the combined effects of earthquake and emergency braking on the running safety of high-speed trains.

Liang Ling, Kaiyun Wang, Wanming Zhai

### Safety to Crosswind of Railway Vehicles in Presence of Wind Barriers: Numerical-Experimental Approach

When a high-speed vehicle is subjected to cross wind action, one of the most critical problem connected with running safety is the risk of overturning. To prevent this risk a possible solution is the installation, sideway to railway, of windbreak barriers against cross wind. To evaluate the new level of overturning risk associated to the line sector equipped with wind barriers or, otherwise, to evaluate the level of shielding required to the wind barrier to obtain a pre-defined level of risk, a stochastic methodology for the calculation of the new Characteristic Wind Curves associated to a rail-way vehicle in presence of windbreak barriers has been setup. According to the developed experimental-numerical methodology, first of all wind tunnel tests are performed for the evaluation of the admittance function in presence of barrier and then, by a multi-body model, the vehicle dynamics subjected to cross wind in presence of barrier is evaluated.

Gisella Tomasini, Elia Brambilla, Stefano Cii

### Hunting Phenomenon Evolution of HSRS and Anti-hunting Absorbing Wide-Band Mechanism Solution

High-Speed Rolling Stock (HSRS) has the stability properties of closed-loop system dynamics, and the wear and abrasion of High-Speed Rails (HSR) are the sensitive factors to their evolution patterns. When considering the correlativity between the wear intensity of wheel-rail contact and the general mass of instability hunting oscillation, e.g. the primary/secondary hunting phenomena, the dialectical relations should be held within the track window for near-linear wheel-rail contacts so as to maintain hard the normal wear of wheel treads. Combined with some typical case studies, the full-vehicle stability properties and evolution patterns show that the self-stability of wheelset positioning under elastic constraints and the anti-hunting effectiveness of rotational resisting moments are the two important technical problems to cause the wear and abrasion of HSR. For some high-speed bogie configurations, the carbody yaw over-damped characteristics force the primary hunting phenomenon formed by both modes of rear bogie hunting and carbody rolling. Under the perturbations, like sidewind disturbances to carbodies or matching parameter variation of actual wheel-rail profiles, the primary hunting phenomenon is evolved to the secondary hunting one. As a result the high-speed carbody shaking phenomenon becomes one of important associated factors to the worn wheel-rail bad contacts. The anti-hunting absorbing wide-band mechanism solution was therefore proposed to instruct rightly the safe and comfortable design of high-speed bogies. With the improved high-speed bogies, Vlim = 480 km/h under λeN = (0.10–0.30), Max. 0.35 recommended, HSRS can be running on the extended routing crossover the different-graded lines.

Wei Du, Ming-wei Piao, Guo-dong Li, Jing Yang

### Reliability Analysis of Rail Fastening System When a Heavy Haul Locomotive Passing Through a Small Radius Curve

In this work, a stochastic dynamics model is proposed to achieve the reliability assessment of the rail fastening system when a heavy haul locomotive passing through a small radius curve. The stochastic dynamics model consists of a locomotive model and a track model, in which the rail fastening system is modeled in detail. Under the assumed extreme condition, the two-point contact wheel/rail forces of the locomotive during passing the curve are obtained through the locomotive model, and then are exported to the track model to compute the screw spike pullout force of the rail fastening system. The vertical and lateral stiffness of the rail fastening system and the friction coefficient between gauge apron bearing and sleeper shoulder are selected as random variables, which are assumed to obey the Gaussian distribution. To perform the reliability analysis, totally 100 combinations of the random variables are generated by the Number Theoretical Method (NTM). The Probability Density Evolution Method (PDEM) is adopted to compute the probability density functions as well as the failure probability of the rail fastening system. The result indicates that the rail fastening systems on the transition curve are generally reliable while some of those on the curve section have a certain risk of the screw spike being pulled out. The rail fastening system located between the transition curve and the curve section is more liable to fail than the others, and the maximum failure probability is about 4.2%.

Xuancheng Yuan, Jianzheng Jiang, Shengyang Zhu, Wanming Zhai, Huibin Lou

### Risk Analysis of Vehicle/Track Interaction Related Derailment for Dangerous Goods Transportation by Rail

A vehicle/track interaction related derailment model for a tank car with liquid cargo was developed which takes into consideration grade, curvature, track geometries, car trailing tonnage, car length dimensions and coupler lengths of adjoining cars, speed, superelevation, density and fill ratio of liquid cargo, etc. The model can be used to improve the derailment risk analysis of dangerous goods transportation by rail. Derailment risk is a product of the probability of a derailment and the consequence of that derailment. The vehicle/track interaction related derailment model is an important part of the probability analysis to determine how risk would be affected by improving track geometry, optimizing cant deficiency, controlling friction, grinding more often, optimizing train marshalling, etc. Consequence analysis models were developed based on a GIS database of the railway network, population, waterways in Canada. Safety risk analysis was conducted based on the potential impact of a dangerous goods release due to a derailment on the population in close proximity to the track. Environmental risk was based on the potential impact of dangerous goods release due to a derailment on the local environment. Such risk analysis can be used to assist in train marshalling, route planning and risk mapping.

Wei Huang, Yan Liu, Luke Steiginga, Zach Schenk, Elton Toma

### A Parameterized Turnout Model for Simulation of Dynamic Vehicle-Turnout Interaction with an Application to Crossing Geometry Assessment

This paper presents a parameterized structural track model for the simulation of dynamic vehicle-turnout interaction in a multi body simulation environment. The model is demonstrated by performing simulations for different vehicle speeds, crossing geometries and fixations between crossing rail and sleepers with different stiffness. Results are presented for dynamic wheel-rail contact forces, bending moments in crossing rail and sleepers and sleeper-ballast contact pressure. The main conclusions are that (a) the peak dynamic bending moment in the sleeper under the crossing transition is significantly higher with a stiff direct fixing compared to a softer indirect fixing and (b) the structural loading in terms of bending moment in the crossing rail, bending moment in the underlaying sleeper and sleeper-ballast contact pressure increases proportionally and significantly with increased impact angle and vehicle speed for wheels passing over the crossing transition.

Björn A. Pålsson

### Modelling Track Flexibility in Turnouts Using MBS Approach

A discretely supported track model was built in multibody dynamic software VI-Rail. The model was first compared against the default continuously supported track model and an in-house built finite element model. A plain line case with a short wavelength irregularity was used and a good agreement between the three models was achieved. A full turnout model including both through and divergent routes was then built. A detailed model of a UK passenger coach was used for the vehicle-track interaction simulations. The main focus of this paper is to compare different approaches to model the track, highlighting the capabilities of the selected methodology and give an insight into the influence of model approaches in the S&C panels.

Pedro Jorge, Yann Bezin, Ilaria Grossoni, Sergio Neves

### Relative Movement of Switch/Stock Rails and the Wheel/Rail Interaction Interface

Developing resilient and reliable switches and crossings is one of the key challenges of the railways for the future. Understanding the detailed interaction between the railway vehicle and the track is paramount in order to develop sustainable railway track components. In this paper, an investigation is carried out on the relative movement between the switch and stock rails under dynamics loading and the effect of their relative connection on the wheel/rail interface and the vehicle-track response. To do this, a multibody dynamics software track model is modified and compared to the default approach of using one solid rail profile throughout the switch-stock rail assembly. The results show that significant differences are present when the relative motion between switch and stock rail is accounted for. A sensitivity analysis on the modelling approach and rail-pad stiffness properties is also considered, showing that in comparison there is relatively much less variation based on track support properties. It is concluded that to accurately predict the dynamic behaviour of vehicle and track in switches it is crucial to account for the relative connection between the switch and stock rail and model them as two independent rail bodies.

Yann Bezin, Dimitrios Kostovasilis, Bello Sambo

### Prediction of Long-Term Damage in Railway Crossings Accounting for Variability in Dynamic Traffic Loads

A multidisciplinary methodology for the prediction of long-term damage in a railway crossing is demonstrated by simulating the plastic deformation and wear after 1.5 MGT of traffic. The results are compared with field measurements, and a good qualitative agreement is observed. Potential reasons for discrepancies are discussed. Additionally, a parameter study is performed, where the results suggest that assuming the vehicle–track dynamics is constant in the short term for a number of wheel passages is a reasonable approach to reduce the computational effort.

Rostyslav Skrypnyk, Jens Nielsen, Björn Pålsson, Magnus Ekh

### A Model for Evaluating Long-Term Support Degradation at Railway Switches

A railway switch is characterised by movable parts, discontinuities in rail geometry and non-uniformities in trackbed stiffness. This work aims to assess the performance of railway switches considering long-term degradation of trackbed support with trafficking. A vehicle-track interaction model capable of reproducing the longitudinal variation in support stiffness and changes in contact condition through the switch panel is used. Site measurements of bearer deflection at a selected S&C are used to back-calculate a trackbed stiffness and initialise dynamic simulations to determine wheel-rail and trackbed contact forces. The calculated trackbed forces are used as an input in an iterative process to estimate the evolution of long-term rail top level and irregularity growth. The model results are compared with measured rail irregularity growth and the model is shown to predict similar trends. Model results and measurements show that higher rates of track geometry degradation occur around the load transfer area. The use of Under Sleeper Pads is found to decrease differential settlement within the panel.

Ilaria Grossoni, Yann Bezin, Louis Le Pen, Geoff Watson, Dimitrios Kostovasilis

### Reducing Impact Loads at Railway Crossings Using Tuned Resilient Elements

Yann Bezin, Dimitrios Kostovasilis, Bello Sambo

### Prediction of Vertical Dynamic Vehicle–Track Interaction and Sleeper–Ballast Contact Pressure in a Railway Crossing

The vertical dynamic vehicle–track interaction in a railway crossing is simulated in the time domain based on a moving Green’s function approach in combination with an implementation of Kalker’s variational method to solve the non-Hertzian, and potentially multiple, wheel–rail contact. The method is demonstrated by calculating the wheel–rail impact load and the sleeper–ballast contact pressure for a hollow-worn wheel profile passing over a nominal crossing geometry.

Xin Li, Jens C. O. Nielsen, Peter T. Torstensson

### Validation of a Finite Element Multibody System Model for Vehicle-Slab Track Application

In this paper, we present a finite element multibody system model for the dynamics of vehicle-slab track application, and the preliminary validation is introduced of the track response. The model includes the multibody system model for vehicle, the finite element model for slab track, and the interaction part for the wheel-rail contact. Preliminary results on the track dynamic response from simulations and experiments are compared. The results show good agreement on the response of the track system, and the model can be applied for further co-simulation for vehicle track interaction investigations.

Zhiyong Shi, Martina Meacci, Enrico Meli, Kaiyun Wang, Andrea Rindi

### Simulation of Vertical Dynamic Vehicle–Track Interaction – Comparison of Two- and Three-Dimensional Models

By using an extended state-space vector approach, the vertical dynamic vehicle–track interaction between a railway vehicle and a slab track is simulated in the time domain. Both two- and three-dimensional track and vehicle models are considered. In the two-dimensional track model, the rail, panel and roadbed are modelled using Rayleigh–Timoshenko beam elements. In the three-dimensional track model, the rails are modelled using Rayleigh–Timoshenko beam elements, whereas the panel and roadbed are modelled by 3D brick elements. Based on Python scripts, the parameterised three-dimensional track model is developed in Abaqus, from which the system matrices are exported to Matlab where the dynamic analysis is performed. In the presented numerical examples, similarities and differences between the two models are discussed, and it is highlighted in what scenarios the different models are feasible to employ.

Emil Aggestam, Jens C. O. Nielsen, Niklas Sved

### Analysis of Vibration Characteristics and Isolation Measures of Railway Underpassing Airport Terminal

With the rapid development of urbanization and industrialization in modern society, the large-scale integrated hub must meet the seamless connection of various modes of transportation, thus the railway undepassing the airport terminal has become the main choice for engineering construction scheme. When the train under passes the airport, the vibration due to the wheel-rail excitation will affect the airport office area, commercial area and passenger waiting room in the terminal. With consideration of vibration source system, transmission process and vibration receiving body, this paper established the vehicle-track coupled model and the tunnel-soil-surface building integrated coupled model respectively to analyze the vibration characteristics of railway underpassing airport terminal as well as the effect of the corresponding vibration isolation measures.

Feng Dai, Jizhong Yang, Su Wang, Xuwei Jin

### Locomotive Adhesion Control + Rail Friction Field Measurements = ?

The design and validation of a locomotive adhesion control system is a very complex multi-disciplinary engineering problem that not only requires consideration of the electrical system but also requires to go very deeply into mechanical and material engineering as well as tribology. The typical approach for advanced locomotive traction studies focuses on the development of the following models and algorithms: train dynamics modelling, multibody locomotive model, traction power system model, adhesion control algorithms, wheel-rail contact modelling and track models. These are required to cover all the physical processes present in the system. One of the complicated parts of this system is how to represent the creep force characteristics at the wheel-rail interface properly without measurements being performed on existing or modified/upgraded locomotives under traction or braking because any locomotive field measurements involve high testing costs. This paper discusses how this can be avoided using friction measurement data obtained in the field with an experimental tribometer and how that data should be interpreted for locomotive studies, and how it might affect locomotive performance outcomes considering locomotive adhesion control strategies. Numerical experiments have been performed by the co-simulation of two full traction control systems developed in Simulink, and two locomotive mechanical models developed in Gensys multibody software, representing two standard gauge heavy haul locomotives running under traction operational scenarios. All possible limitations and results observed during the development and implementation studies have been discussed.

Maksym Spiryagin, Harold Harrison, Qing Wu, Dwayne Nielsen, Colin Cole, Peter Wolfs, Chris Bosomworth, Mark Hayman

### Analysis of Self-excited Vibrations of an Electromagnetic Track Brake

Electromagnetic track brakes in commuter and main-line trains work independently of the wheel-rail contact. Therefore, they play an important role especially in low adhesion conditions. Today’s demands on braking performance require that track brakes stay active until the train comes to a full stop. Measurements during field tests have shown that under these conditions severe self-excited vibrations may occur. In order to analyse these vibrations, a coupled electromagnetic and mechanical model is developed. From this model, two different mechanisms have been identified that may lead to self-excitation. Results show how design parameters may be used to reduce or mitigate self-excited vibrations that may damage the structure or increase stopping distance.

Daniel Tippelt, Johannes Edelmann, Manfred Plöchl, Michael Jirout

### Dynamics of Wagon System Containing Out-of-Round Wheels Subject to Brake Torque

Effect of out-of-round (OOR) wheels to the vertical and longitudinal accelerations of wagons subject to braking is reported. A multibody dynamic model that enables application of braking torque naturally with no need to specifying speed profile as a priori was formulated for this purpose. OOR was considered as a periodic defect of six orders around the wheel tread with an amplitude of deviation from design radius of 0.5 mm. Magnitude of the braking torque was limited below the level of skid risk; brake torque was applied gradually in 4 s. OOR was found to dominate (masking the effect of braking) the accelerations of the wheelsets and bogie frames. Longitudinal accelerations were much larger than the vertical accelerations. Accelerations in wagon body were well damped with no significant difference between defect-free and OOR wheels with and without braking.

Qingqun Lan, Manicka Dhanasekar, Yunendar Handoko

### Curving Performance of High-Speed Trains Running on Steep Grades

China has been constructing a large high-speed railway network, which covers the high-speed railways including a large number of steep grades and curves in the mountain area. For example, there are 24 steep grades with gradient larger than 1.5% in Xi’an-Chengdu high-speed railway, in which the longest steep grade (2.5%) has a length of 45 km. Therefore, the high-speed trains have to suffer large traction forces or dynamic braking forces for a long period when they pass through these severe grades. This paper presents a study of the effects of traction and braking on the curving performance of high-speed railway vehicles when the train passes through severe grades. A numerical model considering the track grade, the train traction and braking, and the train-track interaction is formulated. The dynamic curving performance of a high-speed train subjected to heavy traction and braking is investigated. The effects of tractive/braking force, the track gradient, and the train speed are reported. This study is shown to enhance the understanding of the combined effects of curving and traction/braking on the dynamics performances of high-speed trains.

Yanlin Hu, Liang Ling, Kaiyun Wang, Wanming Zhai

### Simulation of Long Train Dynamics with the Consideration of Wheel-Rail Contact

Classical train simulation is the domain of low Degree-of-Freedom simulators such as Longitudinal Train Simulators. These systems execute quickly, at faster than real-time rates and provide accurate results for a limited application space. For the computationally fast computer reason they are not only used in engineering analysis but have also been integrated into onboard vehicle computers for live train state information. With computer power ever increasing, most recently from the explosion of multi-core computing, the constraints of the past are no longer as restrictive. Through the use of parallel computing, multibody vehicle simulation modelling of wheel-rail contact has been introduced into the train simulation field. Current implementations of this hybridized approach still run significantly slower than real-time. This paper investigates the issues surrounding the use of this simulation methodology in hard real-time systems such as those required for real-time train simulation in onboard vehicle computers and provides some approaches for further computational enhancement. The initial findings demonstrate the benefit of a parallel scheme for multi-body train simulation.

Chris Bosomworth, Qing Wu, Maksym Spiryagin, Colin Cole

### Proposal and Test Run of Wheel Slip Stabilizing Control

This paper proposes and demonstrates a novel slip stabilizing control method for electric railway vehicles to achieve both high acceleration and riding comfort. The control method squeezes the torque command of traction motors generated by a feed-forward slip acceleration control in order to stabilize wheel slips. The controller stabilizes wheel velocity during wheel slips and avoids diverging of wheel slipping that can cause vibrations, noises or wheel and rail damage. The method also achieves slower re-adhesion with less longitudinal shock. The test run results show that the method achieves both higher acceleration and better riding comfort than the conventional re-adhesion control method.

Shingo Makishima, Michiyasu Okubo, Masashi Takagi

### Which Parameters Determine the Type of Bogie Hunting Bifurcation?

An important question of railway vehicle dynamics is to understand which parameters affect the transformation between sub- and supercritical bifurcation in the stability assessment. Recent studies report effects of the equivalent conicity, the wheelset guidance stiffness and other parameters. Performing parameter variations using a typical bogie model with linear suspension components but considering all nonlinearities of wheel/rail contact geometry, this paper shows that the type of bifurcation depends predominantly on the nonlinearity of the wheel/rail contact geometry, while the effects of the equivalent conicity, the creep forces and the wheelset guidance stiffness are less important.

Oldrich Polach, Jonas Vuitton

### Determination of Aerodynamic Drag of a Train Consisting of Gondola Cars

The paper considers the development of the simulation models of trains and making calculation of their aerodynamic drag at various speed, load and number of cars in the train. For simulation the finite-volume method in Ansys software was used. The finite-volume method calculation results were compared to analytical calculations and the experimental results. Methodology has been proposed for determining aerodynamic drag of several train consists formed out of gondola cars.

B. O. Poliakov, Iu. P. Boronenko

### Contrastive Studies on Non-linearity Vibration Influences to Rigid-Flex Coupling System of Rolling Stock for Light Freight Rails

Some key techniques should be constituted focusing on the difficult problems in the rolling stock developments and operations for light freight rails, by which the commercial velocity can be raised respectively to 160/250 km/h when running crossover the three main lines of present normal-speed rails or the permissible ballast tracks of newly-built high-speed rails with the cargo distribution capacity promotion and the considerable profit expectation from medium/long-distance transportations. By applying the traction-rod inner design with both bogie cradle and mono traction-rod device, the rapid freight bogies have been evolved to bolsterless ones from bolster ones. To take the secondary rubber stacks instead of the airspring suspensions, $$K_{2} \gg K_{1}$$, the simulation analyses of rigid-flex coupling vibrations indicate that the current technical condition is not sufficient, in which the non-linearity influences of bogies to carbody interface can be caused therefore, and the non-linearity effects of mono traction-rods can also be introduced to the longitudinal and lateral stiffness of secondary suspensions. As a result the carbody shaking phenomenon will be produced with the dramatic impacts to wheel-rail contact wear and light-weight carbody elastic vibrations. If changing to the use of Japanese airsprings, the optimal configuration of bolsterless bogie was formulated with actively sharing the technical achievements from the economical operations of rapid passenger rails, by which the rolling stock for light freight rails can be running on the extended routing crossover different-graded lines, so as to increase the availability of mobile equipments and to decrease the depreciate rate.

Te-te Li, Ming-wei Piao, Hua Li, Mao-sheng He, Shi-feng Xu

### Effect of Constant Contact Side Bearing Design on Dynamic Performances of Wagon with Two Conventional Three-Piece Bogies

Dynamic performance - hunting stability and dynamic curving of a freight container wagon with two conventional three-piece bogies has been compared with the same wagon with improved bogies through the simulations. A typical wagon popularly used in Australia is modelled for simulations using the Gensys software. The improvement on the conventional three-piece bogie is only focused on side bearings, which are replaced with the long-travel constant contact side bearings. The simulation results show that the improved bogies significantly increase the wagon dynamic hunting stability performance.

Yanquan Sun, Maksym Spiryagin, Colin Cole

### The Structure Design and Dynamic Performance Analysis for Articulated Urban Electric Multiple Unit

A kind of Articulated Urban Electric Multiple Unit and bogies with a maximum operating speed of 160 km/h are developed for Suburban and satellite city railway. And through the dynamic simulation and dynamic test, it is shown that the dynamic performance indexes of the AU-EMU meet the requirements of relevant international standards.

Wen Li, Junchen Han, Chunyou Gao, Lihui Ren, Wengen Xue, Nuo Li

### Critical Offset Distance of Center Plate Based on Wheelset Lateral Force Factor

The center plate is the rotation center of the car body and the bogie. The center plate offset means a certain longitudinal distance exists between the center plate and the geometric center of the bogie, which significantly affects the lateral force distribution of the front and rear wheelsets when the vehicle passes curve. This study proposed the concept of the wheelset lateral force factor according to the specification of the wheelset lateral force limit axle in EN14363. The formula for calculating the wheelset lateral force of a tram with independently rotating wheelset bogie and offset center plate was deduced, and its accuracy was verified by dynamic simulation. On this basis, the calculation formula of the wheelset lateral force factor of the tram was derived, and the relationship between the wheelset lateral force factor and the center plate offset distance was discussed. Based on the principle of minimum wheelset lateral force factor, the critical offset distance of the center plate was obtained. The dynamics simulation results showed that the curving performance of the tram improved when the center plate was at the critical offset distance.

Gang Wang, Lihui Ren, Yuanjin Ji, Youpei Huang

### Investigation of the Performance and Potential of a Novel Trackless Train with Pneumatic Tires

With the acceleration of China’s urbanization process, second and third tier cities have gradually joined the planning and construction of urban rail transit. Second and third tier cities are more suitable for the development of medium-traffic rail transit systems. This paper proposes a novel type of medium-traffic urban traffic system, which combines the advantages of rail transit and public buses. It adopts pure electric drive and applies multi-axle active steering technology to provide a fast and flexible way for public transportation in small and medium-sized cities in China. It’s designed to relieve the problem of travel in cities that are increasingly prominent in China.

Ning Zhang, Xi Wang, Zi-qian Zhao, Wei-chao Zhuang, Guo-dong Yin

### Curving Performance Evaluation of EEF Bogie with Inclined Wheel Axles Using Scale Model Vehicle

The EEF bogie proposed by Frederich realizes excellent curving performance making use of gravity restoring forces generated by the tread gradient of independently rotating wheels. However, the bogie gives rise to a kind of hunting motion due to slight longitudinal creep forces of wheels as the vehicle running speed increases. In the previous study, an effective modification of the EEF bogie which solves the hunting motion is mentioned. The solution is to incline both wheel axles while using nearly cylindrical tread. In this paper, the EEF bogie with inclined wheel axles is designed while performing running experiment with scale model vehicle on a sharp curve. From the result of experiment, the proposed bogie has excellent curving performance in tight curve.

Yohei Michitsuji, Kohei Mizuno, Yoshihiro Suda, Shihpin Lin, Shingo Makishima

### A Newly Designed Coupled-Bogie for the Straddle-Type Monorail Vehicle: Calculation Method for the Key Parameter and Dynamic Performance

Han Leng, Lihui Ren, Yuanjin Ji, Youpei Huang

### Study on the Mechanism and Influencing Factors of Hydraulic Anti-kink System of Low-Floor Tram

The hydraulic anti-kink system is an important safety system for low-floor trams, which is used to prevent unnecessary displacement and motion of a single carbody tram. According to the structure and working principle of the hydraulic anti-kink system, the mechanism of the hydraulic anti-kink system is studied and the mathematical model of the hydraulic anti-kink system is derived. Meanwhile, the influencing factors of the stiffness and damping characteristics of the system are analyzed. A 4 modular 100% low-floor tram simulation model was established by SIMPACK/SIMULINK, the influence of the hydraulic anti-kink system on the dynamic performance of the tram in the small radius curve passing is studied. The effects of the anti-kink system on typical vehicle traction/brake fault and push rescue conditions are investigated. The result shows that: the anti-kink system can well constrain the motion posture of the tram during the small radius curving, so that the trajectory of each carbody is consistent, and the lateral offset of the vehicle body is reduced; and in typical vehicle traction/brake fault and push rescue conditions, the Z-shaped bending caused by the mutual squeezing between the modules of the vehicle can be prevented, and the derailment of the vehicle can be effectively prevented when a tram with anti-kink system installed. The dynamic simulation model of the anti-kink system is verified by experiment.

Youpei Huang, Yuanjin Ji, Dao Gong, Lihui Ren

### Coil Springs in Suspensions of Railway Vehicles

Coil springs are the basis of many suspensions and determine safety of operating the railway vehicle by structural strength, buckling resistance and durability. There are various analytical expressions used to determine structural strength and durability of springs under the action of combined loads (vertical and horizontal), that are widely used in calculations [2, 6, 7]. These expressions were obtained empirically and are not applicable to a wide range of springs with different geometry and operating in different conditions. Spring durability is usually evaluated by calculation or by experimental method using the Wöhler curve and comparison of durability limit and maximum or equivalent stress amplitude [5]. The paper proposes finite element approach (boundary conditions and shear stress criterion) to simulation of spring structural strength and to determine stress in durability calculations. Finite element approach (boundary conditions and reserve coefficient) is also proposed to determine spring buckling resistance under compression load.

Anna M. Orlova, Aleksei M. Sokolov, Ekaterina A. Rudakova, Denis V. Shevchenko, Artem V. Gusev, Stanislav I. Popovich

### Inertance-Integrated Primary Suspension Optimisation on an Industrial Railway Vehicle Model

Improving the track friendliness of a railway vehicle is highly beneficial to the rail industry, as it substantially increases its cost effectiveness. Rail surface damage under curving conditions can be reduced by using vehicles with a reduced Primary Yaw Stiffness (PYS); however, a lower PYS often leads to a reduction in high-speed stability and can negatively impact ride comfort. Previous studies have suggested that this trade-off, between track friendliness and passenger comfort, can be successfully improved by using an inerter in the primary suspension; however, these studies used simplified two-axle vehicles and simplified contact models, and track inputs. Considering a more realistic four-axle passenger vehicle model, this paper investigates the extent to which the PYS can be reduced using inertance-integrated primary lateral suspensions without increasing Root Mean Square (RMS) lateral carbody accelerations when running over a 5 km example track (with a number of vertical, lateral and longitudinal irregularities, and gauge variations). The vehicle, with inertance-integrated primary lateral suspensions, has been modelled in $$\mathrm{VAMPIRE}^{\textregistered }$$, and the vehicle dynamics are captured over a range of different velocities and wheel-rail equivalent conicities. Several inertance-integrated suspensions are optimised, leading to permissible PYS reductions of up to 47% compared to the original vehicle, whilst lateral carbody accelerations remain at acceptable levels. This level of PYS reduction would result in a potential Network Rail Variable Usage Charge saving of 26%.

Timothy Lewis, Yuan Li, Gareth Tucker, Jason Zheng Jiang, Simon Neild, Malcolm C. Smith, Roger Goodall, Simon Iwnicki, Neil Dinmore

### A Simplified Yaw Damper Model for Use in Dynamics Simulation

A simplified physical model of a high-speed train yaw damper is developed which has the ability to reproduce its dynamic performance with less computational efforts. It is then suitably validated with experimental results considering static and dynamic conditions. At last, comparisons of vehicle dynamics relevant to vehicle stability are carried out, by integrating the proposed model and conventional Maxwell model into a three dimensional MBS model of a high-speed railway vehicle. In the case of low conicity, the proposed model and Maxwell model show good consistency. This is because the F-D characteristics of the proposed model approximately follow an elliptical and symmetry shape in low excitation frequencies, like the Maxwell model. However, in the case of high conicity, vehicle dynamics are quite different comparing the two damper models. This is because the F-D characteristics of the damper studied in this paper are nonlinear and asymmetrical in high excitation frequencies, and cannot be described by the elliptical and symmetry characteristics of the Maxwell model. It is concluded that the proposed model could be used to study the dynamics of railway vehicle under various operating conditions.

Caihong Huang, Jing Zeng

### Modelling Complex Series Combinations of Draft Gear Springs

A new approach to wagon connection modelling is proposed that allows each stiffness-damper component of each coupler system to be modelled separately instead of being combined into a single inter-wagon connection. Two passenger draft gear types were modelled and evaluated and compared to single inter-wagon connection modelling. The effect of a very different draft gear characteristic at the locomotive was also introduced by adding a friction type draft gear and a larger free slack. The results show significant differences in the acceleration response from the different modelling approaches for the train with single pack draft gears. The results for the balanced type draft gear were almost unchanged.

Colin Cole, Maksym Spiryagin, Qing Wu

### Novel Automated Urban Maglev Transport System: A Validated Multibody Simulation

In the design phase of a completely new transportation system the knowledge of the dimensioning loads acting on the vehicle and the track is very important. For a new urban maglev people mover system called Transport System Bögl (TSB, developed by the company Max Bögl) no empirical values are available. To obtain design loads for this new system the loads are calculated using a multi body simulation. Simulation of maglev vehicles have a long history. However, the displacements between magnet and guideway are less important for quasistatic loads for instance at the suspension elements because the nominal value of the vertical gap between magnet and guideway amounts only 7 mm. Therefore, in the simulation, the levitation magnets are reduced to linear springs with a high stiffness and viscose damping. Measurements from a full-scale test track have been used to validate the model and its assumptions.

Bernhard Kurzeck, Simon Fink

### Study on the Non-linear Parametric Model of Hydraulic Dampers Before Relieving for Railway Vehicles

The objective of this work is to establish an accurate non-linear parametric model which relates the physical parameters with the damping characteristics of the hydraulic damper before relieving. A new non-linear parametric model including the sub-models of the orifice, hydraulic fluid, pressure chambers, reservoir chamber, etc. is established based on the theory of the fluid mechanics. Subsequently, a new force element of the hydraulic damper based on the new non-linear model is developed with Fortran language in the secondary development environment of the multi-body dynamics software SIMPACK. Used the force element, the force-displacement and force-velocity characteristics of the modified yaw damper with the base diameter of 0.4 and 0.6 mm are calculated under different amplitudes and frequencies of the sinusoidal excitation. Comparing with the experimental results obtained under the same condition, it shows that the new model can accurately model the nonlinear static and dynamic characteristics. Furthermore, the leakages for the high frequency, the air release and cavitation for the modelling of the fluid shortage, the non-constant flow coefficient of the orifice and the dynamic states of the fluid should be included in the modelling of the hydraulic damper before relieving. The non-linear parametric model proposed in this paper is more applicable to the railway vehicle system dynamics simulation and individual system description of the hydraulic damper.

Hongxing Gao, Maoru Chi, Xuesong Jin, Shulin Liang, Changxin Chi, Xiaozhi Zhou

### Estimation of Dynamic Properties for the Validation of Driven Railway Vehicle Models

Validated and reliable models are becoming increasingly important for vehicle development. In order to ensure a sufficient model quality, the models are validated based on on-track tests. Here, the European Standard EN14363 proposes a method for validation considering the vehicle/track interaction. A high influence on the vehicle/track interaction is caused by varying or unknown operating conditions (e.g. friction conditions, condition of the rail profiles, superstructure condition), which are dominated at the time of the measurement. These influences make the estimation of vehicle parameters difficult. In this paper, an approach to estimate the dynamic parameters of railway vehicle models by means of the so called shaker test is presented. The shaker test is a pragmatic and cost-efficient way to determine the dynamic properties of a driven railway vehicle independently of the vehicle/track interaction. The vehicle is equipped with acceleration sensors and a frequency dependent excitation is applied via the drive train. A methodology is shown to determine the model parameters with regard to the linear system component by using numerical optimisations in order to achieve an improvement of the model quality.

Josef Fuchs, Bernd Luber, Gabor Müller, Wolfgang Rulka

### Using Saint Venant’s Elements in Multibody Archeological Studies

In 2015 different IAVSD colleagues received the George Stephenson gold medal for a paper [1] dedicated to the study of interaction between railway multibody models and track structures with the help of modern dynamic softwares. This has been an occasion to have a look at the life of George Stephenson and his contribution to railways.A set of questions appear: how did he manage stability? How did the engineers for all the different models developed during the steam century? The stability theory has been established only by authors like Rocard during the beginning of the 20th century: could it be possible today to design quickly, as did the ancients, a new locomotive from scratch? And consequently, are we more efficient with our multibody simulation tools than the ancient engineers? Or simply, can we estimate today the stability or curve behavior of these vehicles?The studies of different old vehicles led to the remark that unsymmetric and non-linear mechanisms, particularly dry friction elements, were key points of theses mechanisms, step by step replaced by symmetric and smoothed linear design. Fortunately, the use of Saint Venant’s elements, defined a little later but during the 19th century, is still efficient to represent and simulate the early railway age vehicles.

Hugues Chollet

### Nonlinear Observer Design for Guidance and Traction of Railway Vehicles

State observer design turned out to be crucial in several recent railway vehicles projects on active control and condition monitoring at DLR, but may also be useful for emerging technologies like the cyber physical system and the digital twin approach or the realization of predictive maintenance concepts. With this background and motivation the paper presents a process in three steps: (i) an initial analysis results in a physical model, (ii) the subsequent transfer to state space representation facilitates the prove of observability and (iii) the observer synthesis supports the design of the observer feedback law. Results from two projects, one related to longitudinal or traction dynamics, the other associated to the guidance task of independently rotating wheels, demonstrate the application of the observer design process and offers a comparison of observer estimates with measurements.

Andreas Heckmann, Christoph Schwarz, Alexander Keck, Tilman Bünte

### Estimation of Friction Coefficient Between Outside Wheel Flange and Rail Considering Influence of Wheel/Rail Wear

The running safety of a railway vehicle against flange-climb derailment is evaluated with the derailment coefficient. A monitoring bogie, which can measure the derailment coefficient during commercial operations, has been developed and condition monitoring of derailment coefficient has been realized. However, the critical derailment coefficient is determined by the friction coefficient between the leading outside wheel flange and rail, which changes due to wayside rail lubrications. In order to evaluate the running safety more accurately, the present paper proposes an estimation method of the friction coefficient of the leading outside wheel flange utilizing the multibody dynamics simulation. By changing the friction condition and repeating simulation in sharp curves, relationship between the given friction coefficients and the calculated wheel/rail contact forces is derived, and look-up table is created from the results. The friction coefficient of the outside wheel can be regressively estimated by inputting the measured contact forces collected with the monitoring bogie into the look-up table. This paper also considers the influence of wheel/rail profiles on the proposed method and presents a modified look-up table made from simulations with the measured wheel/rail worn profiles.

Yosuke Ichiyanagi, Yohei Michitsuji, Akira Matsumoto, Yasuhiro Sato, Hiroyuki Ohno, Daisuke Yamaguchi, Masuhisa Tanimoto, Takuya Matsuda, Takanori Matsumi

### Wheel/Rail Contact Creep Curve Measurement and Low Speed Wheel Climb Derailment Investigation

This paper presents wheel/rail (W/R) contact friction coefficients and creep curves measured by using the Rolling Contact Fatigue Simulator (RCFS). Measurements showed W/R contact friction coefficients and slopes of the creep curves during the transition from partial slip to full slip increase with the decrease of contact stresses under dry contact conditions. Even though the friction coefficient is smaller due to water lubrication, it has little effect on the creep curve transition slope. NUCARS® (NUCARS® is a registered trademark of TTCI) turnout simulations showed that friction coefficient variation with wheel loads may have detrimental effect on flange climb derailment for the case of new wheels running on new rails. Measured W/R contact creep curves under different wheel load conditions are recommended for flange climb derailment investigations.

Xinggao Shu, Yuqing Zeng, Nicholas Wilson, Randy Thompson, Ali Tajaddini

### Wheel/Rail Creep Force Model for Wayside Application of Top-of-Rail Products Incorporating Carry-On and Consumption Effects

With the current lack of a wheel/rail creep force model that simulates the performance of a top-of-rail (TOR) product as a third body layer, this study aims to develop a model for a friction modifier. Pick-up, carry-on and consumption behaviours of the TOR-friction modifier product were thoroughly studied using a full-scale rig (FSR) and a twin disc machine. Results show that the amount of application affects the pick-up, carry-on and consumption behaviours in a FSR setting. In the twin disc setting, the normal pressure affects the consumption behaviour. The experimental data provided the basis for development of a model that allows predictions of the friction behaviour for wayside application of top-of-rail products as a function of distance to the application site and the number of wheel passes.

Zing S. Lee, Gerald Trummer, Klaus Six, Roger Lewis

### Research and Verification on the Nonlinear Characteristics of Wheel/Rail Equivalent Conicity

This paper aims at the influence of nonlinear equivalent conicity with the same nominal equivalent conicity on EMU (Electric Multiple Units) motion attitude based on the wheel/rail nonlinear contact theory. Four worn wheels were considered in this paper, it was found that wheels with same normal equivalent conicity had significant differences on wheel/rail interactions. A new evaluation method was proposed: based on statistics data, the wheel/rail contact condition was identified with “nonlinear factor” and “nonlinear equivalent conicity” derived by equivalent conicity range from 1 mm to 6 mm. Both field tests and simulations indicated that the normal equivalent conicity couldn’t accurately reflect the wear condition of wheel/rail contact. The proposed new indexes based on nominal equivalent conicity and the slope of equivalent conicity curve would reflect the nonlinear characteristics of wheel/rail contact more accurately. It is an effective method to evaluate the relationship between wheel/rail nonlinear contact condition and vehicle dynamic performance.

Ziqiang Xu, Xiaoqing Dong

### On the Double-Point Wheel-Rail Contact Situation Using Simplified Constraints. A Preliminary Study

In this work a smoothed computation of the two-point wheel-rail contact scenario using the simplified Knife-edge Equivalent Contact constraint method (KEC-method) is presented. The procedure that considers the continuous KEC solution of the wheel-rail contact with equivalent profiles (equivalent wheel and single-point rail) proposes a smoothed transition between tread and flange contact in order to reduce the numerical instabilities that abrupt forces in flange may produce when flange contact occurs. This smoothed transition considers a small region in the wheel close to the two-point contact scenario. When contact happens in this region, tread normal contact force is transformed into two normal contact forces: one acting on the wheel tread and the other one acting on the wheel flange where different algorithms for this force transformation are proposed. However, in order to maintain the dynamics of the vehicle, the resultant normal force acting on the wheelsets, which is obtained as a reaction force of the constraint KEC-method, is kept after the force transformation. This procedure is applied to the numerical simulation of a single wheelset and results show that numerical instabilities of the two-point contact scenario using constraints are avoided.

Javier F. Aceituno, José L. Escalona

### Comparison of Wheel-Rail Contact Modelling in Multibody System Online Simulation

The wheel-rail contact modelling is always an interesting topic in rail vehicle system dynamics simulation. Many contact models have been developed for different purposes, and each model has its own pros and cons for different applications. In multibody system (MBS) simulation of rail vehicles, the efficiency and accuracy of the wheel-rail contact model are of importance. It is the aim of this paper to compare in MBS online simulation one classical approach (Hertz theory+FASTSIM), one approximated non-Hertzian approach and the ‘exact’ solver CONTACT and show the influences of the contact modelling on the results of vehicle dynamics simulations.

Binbin Liu, Stefano Bruni

### The Formation Mechanism of High-Order Polygonal Wear of Metro Train Wheels

Wheel polygonisation is a wavy wear on wheel’s circumference, which aggravates the wheel-rail interaction and prematurely invalidates or damages the components of vehicle-track system. This paper presents an investigation into the formation mechanism of high-order polygonal wear of metro train wheels through field experiments and numerical simulations. Some necessary field experiments are conducted to obtain the characteristics of the irregular wear of the wheels and the dynamics responses of the vehicle components. The numerical modal analysis of vehicle’s key components is performed. Furthermore, a long-term wheel wear model is built including a vehicle-track dynamics model coupled with a local wear model. The metro vehicle-track coupled dynamics model considers the flexibilities of the wheelset and track, where the wheelset and track are modelled using finite element method. The effects of elastic deformation of the wheelsets and rails on creepages, creep forces and wheel wear can be considered in the model. The investigation results indicate that the dominating order of wheel polygonal wear is 11–16, corresponding to wavelengths of 165–240 mm. The formation mechanism of high-order wheel polygonal wear is the P2 resonance of some types of track structure, and the first bending resonance of the wheelset can accelerate the development of wheel polygonal wear.

Xiaoxuan Yang, Wei Li, Gongquan Tao, Zefeng Wen

### Suppression Measures for High-Order Polygon Wear Wheels Based on Resonance Theory

Through the track mode calculation theory, it is found that the resonance with the 3rd order mode of the track is the main reason for the formation of the 20th order wheel polygon, and the theory is verified by experiments. Finally, the anti-resonance wheel polygon wear suppression measures are proposed, including changing the support damping of the rail, optimizing the structure of the wheelset and bogie frame to avoid the 580 Hz high-frequency resonance. The existing polygon wear can be avoided by changing the vehicle operation speed and operation line.

Huanyun Dai, Yayun Qi, Junjie Shi, Dadi Li

### New Methodology to Estimate Costs Caused by Rail Wear and RCF Depending on the Type of Running Gear

A new methodology to estimate costs for wear and Rolling Contact Fatigue (RCF) on rails that cause a major portion of track maintenance costs is presented. It is demonstrated for a standard UIC-Y25 bogie and a FR8RAIL bogie, a softer and cross-braced iteration of the former. The rail profile evolution and the surface-initiated fatigue on the rail surface for different track radii with progressive tonnage are calculated using multi-body simulations. ‘Fastrip’ is used to calculate tangential stresses on the contact patch. Various non-linearities in the vehicle and track models have been considered, based on running conditions on the Swedish Iron-ore line. A cyclic rail grinding procedure at fixed tonnage intervals based on recommendations from EN13231-5 is implemented, to also account for the effect of track maintenance on the rate of rail surface damage. The wear depths (W), worn cross-sectional areas (A) and the number of axle passes that carry a risk for RCF initiation ($$N_r$$) are presented and discussed for 100 Mega Gross Tonnes passage. In doing so, the methodology addresses ‘track-friendliness’ of the running gear considering both its design and the track maintenance strategies.

Visakh V. Krishna, Saeed Hossein-Nia, Sebastian Stichel

### Effect of the Influence Factors on Rail Head Checks Initiation and Wear Growth Under Wheel-Rail Stick-Slip Contact

Based on the prediction method of the coexistence of rolling contact fatigue (RCF) crack initiation and wear growth, three kinds of influence factors on head check (HC) initiation and wear growth in rail of heavy-haul railway, including radius of curve, hardness of rail and friction of coefficient between rail and wheel (COF), were analyzed by orthogonal experiment method. The influence degree of different factors on HC initiation and wear growth were discussed. It can be seen from the result that if the COF kept in 0.2–0.4, three influence factors influenced on HC initiation life and wear growth from serious to minor were the radius of curve, hardness of rails and COF. When COF kept in 0.2–0.4, the rail with high hardness, 395 HBW for instance, was recommended for the curve radius less than 1000 m and all the three kinds of rails were recommended for the curve radius beyond 1000 m.

Yu Zhou, Congcong Zhang, Xuwei Huang, Dingren Sun

### Study on the Initiation of Fatigue Cracks Due to Wheel-Rail Impact at Insulated Rail Joints

In this study, we present a method for predicting the initiation of fatigue cracks at insulated rail joints (IRJs). The method includes (1) FE simulation of dynamic wheel/rail interaction at IRJs; (2) analysis on the evolution of wheel/rail contact behavior, and (3) numerical prediction on the initiation life and position of fatigue cracks. To demonstrate the method, we analyzed the crack initiation for a series of rail end intervals. The results indicate that shear loads in the material affects more on the initiation of fatigue cracks at both the surface and subsurface of rail head. Fatigue cracks have a higher likelihood to take place at 0–2 mm below the rail surface of IRJs, with the most dangerous region being at 1 mm below the rail surface. The variation of the rail end interval seldom affects the crack initiation life at the leading rail end of IRJs, whereas it can significantly influence the crack initiation life at the rear rail end.

Zilong Wei, Xiubo Liu, Yu Zhou, Xinyu Jia, Guoqing Li

### An Innovative Tool for Simultaneous Wheel and Rail Damage Evaluation

Two of the main problems in railway systems, both dynamically (safety, comfort, etc.) and economically (planning of maintenance interventions maintenance, reduction of wheel and rail lifetime, etc.) are represented by the wear of wheel and rail profiles and by the rolling contact fatigue. For these reasons, nowadays the prediction of wear and crack growth at the wheel-rail interface is a fundamental problem in the railway field, directly correlated to the maintenance planning. Hence, the authors present the development of an efficient and innovative modelling approach, suitable to different scenarios, that combines a wear model to evaluate the wheel and rail profile evolution and a RCF crack prediction model based on experimental relationship validated through experimental tests carried out in the Tribology Research Institute of the Southwest Jiaotong University in Chengdu.

Butini Elisa, Marini Lorenzo, Meacci Martina, Meli Enrico, Rindi Andrea, Zhiyong Shi, X. J. Zhao, W. J. Wang

### Impact of Track Health on Vehicle-Track Interaction Loads

Dynamic loads exchanged between the rolling stock and the operated track are intrinsic to the railway operation environment. The purpose of the authors is to trace a path towards a realistic definition of a load mission profile for the structural fatigue dimensioning of the vehicle components. In former works, the methodology to study how the varying characteristics of vehicle components, in normal and degraded conditions, can impact on the vehicle/track interaction loads and on the track damage, was widely dealt with. In this paper, the same methodology is applied to study the impact of modified track conditions on the vehicle/track interaction loads. The focus of this paper is therefore on the characterization of the track and its maintenance status, necessary to simulate the real loads experienced by the vehicle and by the track itself. The aim is to highlight what “indexes of health of the track” weight more on the dynamic loads exchanged between the vehicle and the track, and shall therefore be kept under control, to minimize safety risks and operational costs. The assessment criteria are defined according to the EN14363 regulation.

Caterina Ariaudo, Naim Kuka, Riccardo Verardi

### Simulation of Track-Locomotive Interactions in the Longitudinal Direction

Interest has been expressed from industry regarding the investigation of longitudinal interactions of tracks and locomotives. The majority of railway track dynamics models focus on vertical and lateral directions; railway track longitudinal force models are rarely published. This paper developed a three-dimensional railway track model which considers four structure layers: rails, sleepers, ballast and subballast. The rails are modelled using the Finite Element Method (FEM) and each node has six Degrees of Freedom (DoFs). Sleepers are modelled as rigid bodies and each also has six DoFs. Ballast and subballast are modelled as blocks and each has three translational DoFs. Frictional behaviour is considered in the longitudinal direction of the fastening models as well as in the longitudinal and lateral directions of the sleeper-ballast force connections. Locomotive-track interaction simulations are conducted using a parallel co-simulation technique to combine the track model to a locomotive model developed in GENSYS.

Qing Wu, Yan Sun, Maksym Spiryagin, Colin Cole

### Rail Vehicle Dynamics Simulation-Based Decision Support for Novel Block Brake Material Implementation in Sweden

The application of TSI Noise in Sweden needs decision support that can objectively state system-wide benefits and disadvantages, as there are issues with the introduction of novel block brakes: reduced braking performance and increased equivalent conicity. The Roll2Rail Universal Cost Model (UCM) is used to analyse Life Cycle Cost (LCC), as it was also conceived so that it could be used within the decision making processes of infrastructure managers. The simulated characteristics are mainly track Rolling Contact Fatigue (RCF) due to the worsened dynamic train-track interaction.

Carlos Casanueva, Babette Dirks, Tohmmy Bustad

### Assessment of Curve Passing Performance and Active Steering Control of Railway Vehicle with Independently Rotating Wheels Using Negative Tread Conicity

As an alternative of solid axle wheelset, the independently rotating wheel is widely used in the light rail transit. In order to improve curve passing ability of railway vehicle with independently rotating wheels, a special structure namely independently rotating wheels using negative tread conicity was proposed by the author of this paper. Since the propose of this structure, dynamics analysis based on simplified model has been implemented by means of simulation and scale model experiment. But the precise numerical analysis of railway vehicle with such construction hasn’t been handled under the framework of multibody dynamics analysis to date. Moreover, the active steering control which is expected to improve the curve passing performance further of such kind of railway vehicle has also been rarely reported. To this end, this paper aims at assessing the curve passing performance of both types of railway vehicle with independently rotating wheels, and subsequently the effect of active steering control on railway vehicle with independently rotating wheels using negative tread conicity to serve as the guiding research of full scale vehicle experiment and other expanded studies.

Yu Wang, Shihpin Lin, Hiroshi Tajima, Yoshihiro Suda

### Research on the Vibration and Matching Characteristics of the Typical Wheel-Rail Profiles of High-Speed Railway in China

In order to research on the vibration and matching characteristics of typical wheel-rail profiles, a long-term experimental test on the line A and line B lasting one year was conducted to record the wheel wear. The wheel wear, worn distribution and wheelset conicity is investigated for one continuous reprofiling cycle on high-speed line A and B in the China. The simulation model of a high-speed train is established using the Simpack multi-body dynamics software package, and the simulation results agree very well with field test in time-domain. Typical results of simulation are illustrated for the vibration characteristics. The conicity of line A remains stable with the increase of operation distance, and the corresponding carbody and bogie frame vibration acceleration frequency is basically stable. The conicity of line B increases with the increase of operation distance, and the corresponding carbody and bogie frame vibration acceleration frequency is higher.

Maorui Hou, Xiaoyi Hu, Di Cheng, Lan Li

### Integration of a Wear Model into Wheel Profile Optimisation on Metro Vehicles to Mitigate Flange Wear

Wheel flange wear often occurs on metro trains when they negotiate sharp curves, especially for the poor matching of wheel and rail profiles or lack of lubrication, which evidently increases the maintenance and replacement costs of the wheelsets and rails. The reason for severe flange wear of the original wheel profile on one metro line in China is investigated through field experiments and numerical simulations. An optimal wheel profile is presented based on the rolling radius difference (RRD) to improve curving performance of the vehicle and mitigate flange wear. A wheel wear prediction model, coupling a metro vehicle dynamics model considering multipoint contact with a long-term wear simulation model, is developed, which is validated using field measurement results. The capability of the optimal wheel profile is numerically evaluated. The results show that the improper wheel-rail profile matching of the original wheel profile is responsible for wheel flange wear. The large proportion of sharp curves and the abnormal rail cant also contribute to flange wear. The optimal wheel profile proves to work fine in terms of wheel/rail contact geometry and wear performance. The wheel flange wear of the optimal wheel profile is decreased by over 60% compared with that of S1002 profile.

Dexiang Ren, Gongquan Tao, Zefeng Wen, Shulin Liang, Hongqin Liang, Xuesong Jin

### Optimization of a Tram Wheel Profile to Reduce Flange Wear on Sharp Curves

Owing to the existing of many sharp curves, the fast wear of wheel flanges has become a big problem in a Chinese tramway. To reduce the wheel flange wear rate and increase the lifetime of tram wheels, the authors have conducted extensive experimental measurements and numerical analyses. The long-term tracking measurement concentrating on the natural wear process of the tram wheels have been carried out. This paper reports the flange wear characteristics and developing law of the tram wheels based on measured data. An optimal wheel profile for the tram vehicle was proposed based on a large number of multi-body dynamics simulations. The wear and curving performances of the original and optimal wheel profiles were compared through dynamics simulation. The results show that the optimal profile can improve both the wear and dynamic curving performances of the tram vehicle.

Zhang Chen, Liang Ling, Yu Sun, Yichang Zhou, Kaiyun Wang, Wanming Zhai

### Torsional Vibration as a Method of Diagnostic Tool for Wheel Flatness

Wheel flat frequently occur during the operation of high-speed train, which will deteriorate the vibration condition of the components of vehicle and track system. Besides, it is likely to threaten the running safety of high-speed train. Hence, deep insight into the fault features of the wheel flat is urgently necessary for prevention of the induced disastrous consequences. This paper aims to investigate the effectiveness of using the torsional vibration signal as a diagnostic tool for wheel flatness of high-speed train. The vehicle-track spatial coupled dynamics model considering the dynamic effects of traction transmission system is employed. The nonlinear factors, such as time-varying mesh stiffness, fraction forces, gear backlash, track geometry irregularities and wheel-rail interactions, are considered in detail. Besides, the wheel flat model is incorporated into the dynamics model to obtain the vibration responses. Some signal processing techniques were utilized to analysis the fault diagnostic results from the torsional vibration. It was found that the torsional vibration of traction transmission system successfully detected the wheel flat. As a result, the torsional vibration can be considered an effective approach for wheel flat condition monitoring.

Zhiwei Wang, Paul Allen, Jiangwen Wang, Guanhua Huang, Sisi Xu, Weihua Zhang

### Dynamic Responses of Gear Transmission System of High-Speed Train Due to Wheel Polygonal Wear

As a key component of high-speed train, service conditions of gear transmission system become worse caused by the intended wheel-rail interaction due to the higher speed and wheel failures. To investigate the dynamic responses of gear transmission system, a novel vehicle dynamics model is established based on vehicle and gear dynamic theory. This comprehensive model enables detailed investigation on the system dynamic responses in the vehicle vibration environment induced by track irregularity, wheel polygonal wear and the internal mesh process of gear pair (time-varying mesh stiffness, gear errors, et al.). Moreover, the flexible deformation of gearbox housing is considered using modal superposition methods. The proposed model is validated by comparing the results obtained by simulation and field tests. Besides, the realistic wheel polygonal wear obtained via long term field tests is adopted in the dynamics model. And then, the gear transmission system responses are investigated and assessed in terms of dynamic transmission errors, meshing force and gear pair contact stress under the excitations: track irregularities, wheel polygonal wear. Furthermore, the proposed methods can be used for failure assessment of gear transmission system for any rail vehicle, which is useful to condition monitoring and maintenance.

Zhonghui Yin, Jiye Zhang

### Research on Wear of Locomotive Wheel Considering Traction

With the development of heavy-load locomotives, the wheel wear increases remarkable due to the excessive dynamic force in wheel and rail. For locomotives, the wheel-axle traction is relative large and has significant effect on the rail wheel creepages, which have a direct influence on wheel rail wear. To research the influence on wheel rail wear by traction, a model has been built to calculate the wear of an electric locomotive when running at a constant speed and starting condition, which considers the transmission system based on Archard wear model. The wheel wear is calculated according to a certain actual line, and compared with the measured data, in order to research the abnormal wear on wheel flange during the condition of normal operation by the calculation model of tread wear of the locomotive. The results show that when the locomotive runs at a constant speed of 260 thousand km, the traction increase by 80 kN on the basis of 40 kN and 120 kN, the account of wear increase by 0.74 mm and 1.74 mm respectively; and with the comparison to the measured data, the calculated results are in good agreement with the experimental results, the accuracy of the model has been proved; reducing the lateral displacement of the intermediate wheelset and the side lubrication of rail can greatly reduce tread wear, when the lateral displacement of the intermediate wheelset is changed from 15 mm to 10 mm, its cumulative wear reduce by 15.4%; and the maximum cumulative wear of first, second, and third wheelsets are decreased by 13.40%, 21.32% and 6.46% after side lubrication of rail respectively.

Yang Yang, Maofan Zhang, Kongming Wang, Yan Li

### Wheel Profile Evolution Analyses Based on Measured Field Data

The evolution of three different types of initial wheel profiles in a train with motor and trailer bogies has been investigated. Therefore, wheel profile measurements have been carried out regularly within a wheel re-profiling interval. The wear volume develops in average linearly as a function of mileage. The analysis show, that the initial profile shape and the position where the wheels are located along the train does not significantly influence how the wear volume develops. Furthermore, only little differences were observed when comparing motor and trailer bogies. The same is true for the wear distribution along the profile at the end of the re-profiling interval, although the flange wear of the wheels in the motor bogies is slightly higher. In contrast to this findings the equivalent conicity behaves different. Its development as a function of mileage depends highly on the initial profile shape. Furthermore, it always shows a non-linear s-shaped characteristic. The results of this work are an important basis to develop an advanced methodology which is able to predict the evolution of wheel profiles in an accurate but still efficient way.

K. Six, C. Bernsteiner, G. Müller, B. Kämpfer, M. Rosenberger, C. Marte

### Investigation on the Secondary Quasi-Zero-Stiffness Suspension System of High-Speed Railway Vehicle

The vibration isolation characteristic of a secondary suspension system is a crucial factor influencing the running safety and riding comfort of railway vehicles. This paper put an emphasis on the exploration of the dynamic characteristics of the secondary quasi-zero-stiffness suspension system. Based on the theory of multi-body dynamics, the vertical system model of railway vehicles was established. On this basis, vehicle vibration analysis and calculation program were compiled, and the vibration isolation characteristics of secondary suspension with quasi-zero-stiffness system and traditional linear stiffness system were compared and analyzed.

Zhen Liao, Bing Yang, Shoune Xiao, Guangwu Yang, Tao Zhu

### Lateral Guidance Control Using Information of Preceding Wheel Pairs

The proceeding enhancement of sensor technology, data processing and communication opens a broad field to improve the dynamics of railway vehicles by controlled systems targeting e.g. passenger comfort and wear reduction. In terms of an integrated control structure, information of leading bogies can be used for an advanced control of the trailing ones, like it is recently applied in tilting trains. Such an approach has not yet been investigated for the lateral guidance of driven independently rotating wheels (DIRW). To evaluate the potential of a control using preview information, an integrated control structure is introduced in this work. The control is based on the concept of feedback linearization and considers characteristics of track trajectory and irregularity, which are obtained at a leading wheel pair. The control performance is optimized with the help of software-in-the-loop simulations and the results show a significant improvement of the running dynamics.

Gustav Grether, Andreas Heckmann, Gertjan Looye

### Analysis of Ride Comfort of a High-Speed Train Based on a Coupled Track-Train-Seat-Human Model with Lateral, Vertical and Roll Vibrations

To study the ride comfort of a high-speed train running at a constant speed on a tangent track, a 3D rigid-flexible coupled track-train-seat-human model was developed. The flexible carbody model consisted of six plates with out-of-plane and in-plane vibrations interconnected by artificial springs, and was calibrated using a modal test available in a published paper. The ride comfort was evaluated by total equivalent acceleration calculated by the weighted root-sum-of-square of the weighted root-mean-square of lateral, vertical and roll accelerations at the feet, seat-buttock and human-backrest interfaces. It was concluded the track rigidity had the most influence on lateral, vertical and roll vibrations of the floor above 16 Hz, but had no obvious influence on ride comfort. The flexible carbody model showed intensified floor vibration in lateral, vertical and roll directions above 8 Hz compared with the rigid one, so rigid carbody model caused great underestimation of total equivalent acceleration. The total equivalent acceleration showed increasing tendency as increasing speed. For symmetrical seat positions, the equivalent accelerations showed analogous tendency as the speed. The ride comfort at the carbody center and close to the ends was the worst. Regardless of the seat position and speed, vertical acceleration on the seat pan was the most severe, followed by the vertical acceleration at the feet. The neighbouring subject usually resulted in reduced total equivalent acceleration. The damping of the carbody effectively reduced the total equivalent acceleration for every speed. The effect of the suspension stiffness and damping on ride comfort was also studied.

Jun Wu, Yi Qiu

### Study on Control Method of Maglev Vehicle-Guideway Coupling System Based on Robust Control Theory

A new control method based on robust control theory was investigated to solve the stability problem of the maglev vehicle-guideway coupling system. The track beam’s irregularity was analyzed and considered as disturbance in this system. The vibration requirement of the maglev vehicle was also considered when the controller was designed. The new designed control method was tested on a MATLAB/Simulink modal. The result shows that the new control method can make the vehicle-guideway coupling system stable and the robustness of the system was much better than the traditional control method based on optimal control theory. When there is disturbance in the system, the maximum overshoot is much smaller and with less oscillation.

Qin Li, Gang Shen

### Study on the Dynamics of Gear Transmission System of High Speed Vehicle

Based on the parameters of a certain type of CRH, a rigid-flexible coupling dynamics model of railway vehicle is established. A flexible transmission system dynamics model is setup and it is included in the vehicle system dynamics model. With numerical method, the dynamics of the transmission system is obtained. The simulation results show that the forces acted on the gears get larger when the operation speed of the vehicle increases. The vibration of the transmission system affect the vibrations of the bogie frame, motor and gearbox, but has hardly effects on the vibration of the carbody because of the secondary suspension system and the huge mass of the carbody. The railway vehicle-gear transmission coupling dynamics model is useful to investigate the dynamic characteristics of the gear transmission system of the high-speed train.

Zunsong Ren, Gang Sun, Xue Wei

### Innovative Methodology for Heavy Haul Train-Track Interaction Dynamics Issues

With the introduction of higher axleload wagons and higher traction locomotives in Australia, more rail damage can be observed. To investigate rail damage due to wheel-rail dynamic interactions, a new method is introduced which uses a two-way co-simulation technique to link a detailed infinitely long track model that is written in FORTRAN and a detailed locomotive or wagon model that is developed using the GENSYS software package. The original finite length track model has been evolved into an infinite one by using the method described in [1], considering rails, fasteners, sleepers, ballast, and subgrade. The locomotive or wagon model considers the carbody, bogie frames and wheelsets. Traction motors and gear boxes are considered in the locomotive model. As the track model and vehicle model can run mostly independently, a parallel computing technique is applied to improve the simulation speed as well as to simplify the model integration process. The co-simulation method can be applied to understand the dynamic performance characteristics of high axleload wagons and high adhesion locomotives to give an accurate evaluation and assessment of rail damage based on simulation results. One simulation case is used to demonstrate the method’s effectiveness.

Yanquan Sun, Qing Wu, Wubin Cai, Maksym Spiryagin

### Evaluation Methods of Carbody Hunting Instability of Railway Vehicles

In order to analyze and make the criterion of carbody primary hunting instability, the relationship among equivalent conicity, vehicle speed and hunting frequency has been analyzed firstly. To simulate different vehicles’ carbody hunting instability, this article analyzed the lateral acceleration signals of a simulated full-scale vehicle under several conditions. Through these data, an amendatory method for calculating centroid frequency of vehicle lateral vibration is presented and an index named power concentration ratio (PCR) is presented for distinguishing carbody primary hunting and the data with larger amplitude is screened under the ride index. According to the statistical law, the criterion of carbody primary hunting instability is summarized. Research result shows that the there is a vehicle carbody hunting instability while the lateral acceleration with filtered 0.5–3 Hz exceeds 0.5 m/s2 for six times serially in 15 s. The criterion is shown to be valid through the field test data.

Yi Wu, Jing Zeng, Qunsheng Wang, Ren Luo, Bin Zhu

### The Research of Traction Inverter Fault Diagnosis Based on the Analysis of Motor Vibration Signals

The main circuit simulation model of three-level traction inverter based on SVPWM strategy is established. Taking the power switch elements as the object, the structural fault modes of the inverter are simulated, and the analysis results show that the inverter faults have a great influence on the harmonic content of the output current of the AC side, the content 5, 7, 11 and 13 octave of the fundamental frequency of current increases greatly. After the current harmonic inputting the traction motor, 5, 7 octave and 11, 13 octave harmonics are converted into 6 octave and 12 octave ripple torque acting on the motor respectively, making the motor output vibration contain 6P(1 − s) and 12P(1 − s) current harmonic frequency, which is determined by the logarithm of the magnetic pole P and slip rate s. The vibration signals on the actual operation of the high-speed EMU traction motor were analyzed, and the results show that in the normal mode of inverter, the motor vibration contains current harmonic frequency not obviously, while in the fault mode, it is obviously. It is verified that the main influence of inverter fault on traction motor vibration is current harmonic frequency, therefore, the traction inverter can be fault diagnosed by monitoring and analyzing the motor vibration signal.

Yixuan Shi, Huanyun Dai

### Dynamic Modeling and Coupled Vibration Analysis of Middle-Low Speed Maglev Vehicle-Bridge-Controller System

In order to explore the middle-speed adaptability of the rail beams including 25 m Changsha maglev simply-supported girder, the finite element dynamic analysis models for maglev rail beams was established firstly based on the finite element theory, of which the self-oscillation characteristics are analyzed. The dynamic model of middle-speed maglev train with 120 degrees of freedom is set up based on multi-body dynamics theory. Then the maglev train-bridge-controller coupled model is established considering the PID active suspension control as levitation force. Based on the vehicle-bridge-controller coupled model, the vibration responses of the vehicle-bridge system are further studied at middle speed with track beams which are taken as the structure under the rail. The simulation speed ranges from 100 km/h to 180 km/h. Then the vertical vibration responses of bridge and car body are calculated and analyzed.

Zhihui Chen, Jun Yin, Jizhong Yang, Dubei Feng

### Vibration of Straight and Curved Beam Coupled Systems

Proposal of a Simple Model for Side Structures of Railway Vehicle Carbodies to Analyse Their Elastic Vibrations

This paper presents an analytical method for in-plane and out-of-plane coupled vibration in thin curved panels which are commonly seen in the side structure of railway vehicle carbodies. To treat such coupled vibrations simply, a structure consist of combination of straight and curved beams is introduced. The analytical procedure to derive the equation of motion is described in this paper. Numerical result shows that the straight and curved beam coupled system (SCBS) can successfully express the coupling effect between roof-floor relative vertical displacement and side panel’s lateral deformation. The effect of lateral deformation of cantrail and side beam and curvature of the curved beams on the forced response are discussed.

Takahiro Tomioka

### High Speed Railway Vehicle Comfort. The Influence of Pneumatic Flow Restrictor Diameter, Rail Irregularities, Speed and Structural Damping and Stiffness

The work presented in this paper assesses the influence of flow restrictor diameter, rail irregularities, speed, structural damping, and structural stiffness on comfort indexes. The pneumatic suspension models that the authors have developed are succinctly abridged, and on board tests that support the models are shown. The models are used in conjunction with synthesized rail profiles in order to determine comfort indexes and assess the influence of suspension parameters. The results suggest the use of variable diameter configurations. However, comfort is also affected by the structural response of the vehicle frame. Low stiffness and low structural damping greatly reduce comfort. To assess the influence of structural damping and stiffness, the frame is represented as a uniform Euler-Bernoulli beam with complex elastic modulus and is analyzed in the frequency domain. The increase of comfort indexes as a consequence of stiffness reduction can be mitigated with the use of viscoelastic materials to increase structural damping.

Publio Pintado, Carmen Ramiro, Angel Luis Morales, Antonio Javier Nieto, Jose Manuel Chicharro

### Investigation of the Vibration-Attenuating Effect of Different Damping Measures on Upper Cover Buildings of Railway Lines

When the train runs along the railway line, the vehicle-track system vibrates due to the wheel-rail dynamic load excited by the track irregularity. The vibration propagates in a radiative manner to the distance of the earth through the ballasts and the subgrade, which makes the buildings near the railway vibrate. This kind of vibration will have a great impact on the normal work and health of people, the safety of building structures and the use of some precise instruments and equipment. Therefore, in order to control the negative impact of rail transit on the environment, it is urgent to study the occurrence mechanism of environmental vibration caused by rail transit, the magnitude of wheel-rail interaction force and the law of vibration propagation and attenuation, and put forward corresponding vibration isolation measures. In this paper, the vibration control effect of surface structures is studied on rail transit under different vibration reduction measures.

Jizhong Yang, Xuwei Jin, Dubei Feng, Jinfang Huang

### On the Influence of Track Excitations, Horizontal Curvature and Longitudinal Velocity on the Ride Comfort of Trams

In this study the influence of track excitations, horizontal curvature and longitudinal velocity on the ride comfort in trams is analysed using the continuous comfort method according to EN 12299. The main effect on the ride comfort in the light rail operation is the track layout. All serious values for discomfort were observed in sections with a high horizontal curvature. Track excitations increase the band width and overall magnitude of discomfort but seem to be negligible in tram operation.

Tobias Bettinger, Paul Schönhuber, Christian Schindler

### Analysis of Vibration Propagation Law of Rail Transit Underpassing Large-Span Building Structure

Based on the vehicle-track coupling dynamics theory and finite element analysis method, the coupled vibration analysis model of the railway transit underpass the terminal structure is established, and the vibration propagation law of the soil and the upper terminal structure under the condition of the subway train underpass is analyzed. The results show that, compared with the low-frequency vibration, the vibration attenuation of the medium-high frequency around 63 Hz is more significant; The common column-net between tunnel structure and superstructure will lead to direct vibration transmission, and the structural design of rail transit underpass buildings should consider avoiding the common column-net. In the transmission of train vibration to superstructure and surrounding soils, the attenuation of floor vibration and soil vibration shows periodic attenuation regularity with the increase of distance from the line, and the attenuation of building vibration is obvious. The attenuation speed of soil is obviously less than that of soil. The isolation of building structure and vibration source should be given priority in vibration isolation design.

Feng Dubei, Jin Xuwei, Ge Jinrong, Yang Jizhong

### Prediction of Maximum Torsional Wheel-Set Axle Vibrations Considering Non-linear Adhesion Characteristics

Self-excited torsional wheel-set axle vibrations can lead to polygonization of wheels, cause discomfort for the passengers, and can lead to issues with the stability of the press-fit between wheel and wheel-set. To predict their amplitude, three different methods were investigated: a time-simulation for reference, an energy-method, and the 2cx-hypothesis. It was found that the 2cx-hypothesis shows significant deviations. The energy-method is very accurate (deviations smaller than 0.5%) while still significantly faster than the time-simulation. Thus, the energy method is a viable alternative to predict the amplitude of these vibrations.

Alexander Meierhofer, Christof Bernsteiner, Gabor Müller, Florian Semrad, Franz-Josef Weber, Martin Rosenberger, Klaus Six

### The Influence of the Dynamic Properties of the Primary Suspension on Metro Vehicle-Track Coupled Vertical Vibration

Metal coil springs within primary suspensions in particular exhibit strong internal resonances, which can lead to high vibration amplitudes within the spring itself. A dynamic model of the metro vehicle-track coupled system is established, including the dynamic stiffness of the coil spring set. Two variants of the primary suspension are compared: one with the springset above the axlebox and the other with it offset on a radial arm. The effect of the primary suspension design on the random vibration response is analysed. From the results, it is shown that the internal resonances of the coil springs result in different vibration responses of the vehicle for the two cases. Although the dynamic stiffening effect of coil springs is expected to degrade the vibration isolation, for metro vehicles with a radial arm pivot bushing installation, this does not occur. Due to the rotation degree of freedom of the radial arm, the forces acting through the pivot bushing and coil spring set are out of phase, which decreases the bogie vibration at the spring resonances.

Wenjing Sun, David Thompson, Jinsong Zhou

### Designing and Evaluating Active Safety Systems for Rollover Prevention of All-Terrain Vehicles

The sales of all-terrain vehicles (ATVs) are increasing year by year, especially in countries like Sweden, Australia and New Zealand. With the increase in sales, a proportional rise in the number of accidents involving all-terrain vehicles is also evident. Of these accidents, the major cause was identified as rollover occurrence. While there are some passive safety devices available in the market for ATVs, there is a lack of rollover prevention devices available. In this paper, two active safety systems to prevent rollover have been evaluated. Lateral Load Transfer Ratio (LLTR) is used as the primary parameter to analyse and signify rollover. First, an alarm-based rollover warning system has been analysed premised on the prediction of LLTR and roll angle, with the alarm predicting these two parameters in advance. Second, to further improve the rollover prevention system, by assisting the driver in case of an impending rollover, an active braking system has been studied. The simulation results show that the prediction-based alarm has the potential to give the driver more time to avoid a rollover, but at the same time there is an increased risk of false alarms. Regarding the brake activation system, the results show that even with small brake force applications, it can lead to a significant reduction of the rollover risk.

Erfan Nikyar, Vishal Venkatachalam, Lars Drugge

### A Feedforward Controller Design for Lane Keep Assist Through Differential Braking Force

This paper proposes a control design method for Lane Keep Assist (LKA) systems though differential braking force. By obtaining the time response to equation of motion for a two-wheeled model and simplifying the exponential term, it was determined that yaw rate and yaw moment are proportional to each other. Subject to the ignored terms in order to simplify the equation, we cover an unfollowed handling as well. As the result of the simplification, it demonstrates a control method to achieve any target trajectory. The results of simulations and experiments also verify the effectiveness of this method. Within the vehicle parameters we also focus on tire cornering power to examine the differences between steering control and braking control.

Hironori Ito, Akira Nagae, Masayuki Ikeda, Ryo Inomata

### Corner Test Cases for ADAS and HAVs: A Computational Study on the Influence of Road Irregularities on Vehicle Vision Systems

Automated Vehicles and next generation ADAS hold the promise of disrupting mobility. However, public field trials have recently highlighted road anomalies, such as potholes and bumps, as a source of autopilot disengagements. In this paper, we research the influence of road anomalies on the performance of Artificial Intelligence-based vision systems. To this end, we conducted controlled real-world experiments and developed a validated vehicle system computational model using IPG Carmaker. The vehicle detection, tracking and distance estimation performance have been investigated by undertaking a thorough sensitivity analysis. The results indicate the system limitations in performing adequately for a range of bump sizes and vehicle speeds. With our findings we put emphasis on the importance of vehicle dynamics in the development of automated driving systems.

Yannik Weber, Stratis Kanarachos

### An Adapted Evasive Manoeuvre Assist Function for Over-Reactive and Under-Reactive Drivers

In the present paper, an Evasive Manoeuvre Assist (EMA) function is designed to adapt to different types of drivers, by an optimised steering torque overlay. The existing EMA function amplifies the driver steering inputs using a feed-forward controller which might not necessarily help an over-reactive driver. There exists a need for an EMA which adapts to different drivers as it minimises the risk of collision and gives the driver an experience of good control. The focus of this paper is to identify and define a proper steering sequence reference model for closed-loop feedback control design. A simple single-point preview model is designed first to calculate the reference steering angle. A few test scenarios are set-up using the IPG CarMaker$$^\text {TM}$$simulation tool. The reference model is then calibrated with respect to the amplitude and frequency of the steering sequence by offline optimisation to obtain the optimal steering profile. A feedback controller is then designed using this reference model. The robustness of the function is verified in real-time, using a Volvo rapid-prototype test vehicle.

Preetham Harinath, Santusht Vasuki Kittane, Derong Yang, Lars Drugge, Mats Jonasson

### Review on Tire-Road-Friction Potential Estimation Technologies

Tire-road friction potential is essential information for many active safety systems, autonomous driving functions, road maintenance and liability purposes.

Ari J. Tuononen, Markus Ovaska, Arto Niskanen

### Single Wheel Braking - A New Method to Measure Friction Potential on Public Roads

Knowledge about the friction potential could improve several advanced driver-assistance systems. The true friction potential, needed to validate every friction potential estimation method, is normally measured by full braking tests. These are limited to proving grounds and cannot measure the friction potential on public roads due to their potential impact on surrounding traffic. In order to measure the friction potential under real conditions, a new method, which only brakes one wheel for a short time, is developed. By the means of force measurement wheels all forces acting on the wheel are measured. The vehicle reaction is analyzed and it is shown, that the method can be used without endangering other traffic participants. Measurements of the new method are validated by comparing measurement results to full braking tests and first results of measurements on public roads are presented.

Thorsten Lajewski, Jochen Rauh, Steffen Müller

### Classification of Road Surface and Weather-Related Condition Using Deep Convolutional Neural Networks

In order to achieve the goal of autonomous driving, a precise perception of the vehicle’s environment is required. In particular, the weather-related road condition has a major influence on vehicle dynamics and thus on driving safety.In this paper, we compare Deep Convolutional Neural Networks of different computational effort, namely Inception-v3, GoogLeNet and the much smaller SqueezeNet, for classification of road surface and its weather-related condition. Previously, different regions of interest were compared in order to provide the networks with optimal input data.

Alexander Busch, Daniel Fink, Max-Heinrich Laves, Zygimantas Ziaukas, Mark Wielitzka, Tobias Ortmaier

### Adaptive Control and Robust MPC for Linearising Longitudinal Vehicle Dynamics for Platooning Applications

Vehicle platooning is a promising cooperative driving vision where a group of consecutive connected autonomous vehicles (CAVs) travel at the same speed with the aim of improving fuel efficiency, road safety, and road usage. To achieve the benefits promised through platooning, platoon control algorithms must coordinate the dynamics of CAVs such that the closed-loop system is stable, errors between consecutive vehicles do not amplify along the string, and the time for re-establish the platoon formation to changes in the operating conditions does not diverge when the number of CAVs increases. Linear longitudinal vehicle dynamics are often assumed in the literature to guarantee such stringent platoon control requirements and they can be attained by equipping vehicles in the fleet with mid-level control systems. However, model uncertainties and disturbances can jeopardise the tracking of the reference linear behaviour. Hence, this paper presents for the first time, at the best of the authors’ knowledge, the design and the performance of an adaptive control strategy and a robust model predictive control method as possible solutions for the mid-level control problem. Numerical results confirm that both control techniques are effective at imposing the dynamics of a linear time-invariant system to the longitudinal vehicle motion and they outperform model-based feedback linearisation methods when the parameters of the nonlinear longitudinal vehicle model are affected by uncertainties.

Umberto Montanaro, Shilp Dixit, Saber Fallah

### Investigation of Vehicle and Driver Behaviour During Tyre Burst Using Driving Simulator

This paper deals with a vehicle motion and driver’s behaviour under a tyre burst situation. Phenomenon of a burst of tyre causes a severe accident. However, there are only few researches of the burst of tyre in the past. In this research, it is aimed for driver assist systems at the time of the tyre burst considering drivers’ behavior. As the first step for this purpose, this paper deals with drivers’ test using reactions of drivers’ at the burst on CarSim DS only with screen motions, not real shaking. Drivers’ steering behaviours and vehicle motions were investigated by the reactions of drivers’ at the burst on CarSim DS.

Masahiko Aki

### Vehicle Localization with Vehicle Dynamics During GNSS Outages

Vehicle localization system is one of the most important systems of autonomous vehicles. To improve the localization accuracy during Global Navigation Satellite System (GNSS) outages, this paper presents a GNSS/Inertial Measurement System (IMU)/Wheel speed sensor (WSS) integrated localization system considering vehicle dynamics. The vehicle dynamics model and kinematics model are applied to estimate sideslip angle, which is used to calculate course angle of the vehicle so that the accurate vehicle speed in navigation coordinates could be obtained. When the GNSS measurements are available, the position measurements and heading angle measurements are fed back to the system, and all the sensor information is fused in a Kalman filter. Experiments were conducted to verify the proposed fusion method, and the results show that the consideration of vehicle dynamic characteristics is helpful to improve the localization accuracy during GNSS outages.

Letian Gao, Lu Xiong, Xin Xia, Yishi Lu, Zhuoping Yu

### Dynamic Multiobjective Control Performance Assessment for an Autonomous Vehicle

Control performance monitoring and assessment has been explored as a research topic by the control community during the last decades. Nevertheless most methods are not ideal for identifying controller performance issues in different scenarios with multiple control objectives. The relatively new field of autonomous driving demands such a measure for evaluating controller performance. In this paper we therefore suggest a method for motion control performance assessment of autonomous vehicles independent of a specific driving situation.

André Kempf, Elias Weber, Steffen Müller

### Path Control in Limits of Vehicle Handling: A Sensitivity Analysis

Sensitivity analysis of a feedback-feedforward steering controller for lateral path tracking whilst the vehicle operates in limit handling is the main objective of this paper. The sensitivity analysis is executed by simulation and the effectiveness of the controller is evaluated in a test vehicle on a low friction skid pad. The results demonstrate that the controller is capable to achieve robust path tracking in limit handling condition for the variety of driving conditions with sufficient stability.

Erik Wachter, Antoine Schmeitz, Fredrik Bruzelius, Mohsen Alirezaei

### Design of Steering Controller of Automated Driving Bus

In this paper, steering control methods of automated driving bus using Real-time kinematic GPS for localization are proposed. Firstly, root locus method indicates considering transfer lag from a steering motor to front tires is needed to explain unstable movement of the actual vehicle. Experimental results show that the transfer lag from the tire angle to the handle angle is approximately expressed as the second-order delay system. Secondly, the method and experimental results show that yaw angle and lateral position feedback with look-ahead model is more stable than that without it or single lateral position feedback control. Thirdly, the root locus method explains that feedback gains tuned through vehicle experiments are reasonable because using those gains make a vehicle’s motion more stable and highly responsive. Finally, it is necessary to consider nonlinearity near zero point of steering angle when the vehicle velocity is high since steering angle needed for lane keeping becomes lower.

Takayuki Ando, Kimihiko Nakano

### All-Weather Autonomous Vehicle: Performance Analysis of an Automated Heavy Quadricycle in Non-snow and Snowstorm Conditions Using Single Map

Bad weather (e.g. snowstorm, tropical rain) still brings issues to the automated vehicle (AV) performance due to several factors, such as limited visibility of the environment and bad positioning. As such, most of the testing and study of AV has been done in optimal condition weather. However, for a fully automated vehicle experience, a reliable AV is required to be able to maneuver in all type of weather and environment condition. In this work, an experimental series has been held in the Arctic Circle to evaluate the positioning performance of a driverless vehicle system in the rural area and harsh weather condition. The experiment’s aim is to enable an all-weather AV performance using a single map which can endure harsh northern environment weather. This work briefly reports the experiment finding as well as concisely analyzing the effects of the positioning strategy in the varied weather conditions towards the automated vehicle dynamics and controller performance. A sudden snowstorm during the test sessions allows the system reliability to be validated in both non-snow and snowstorm conditions. The computed average lateral positioning error value of the automated driving is 18.7 cm in non-snow weather, and 22.0 cm for the snow condition. The results show that the inclusion of our solution into the AV system helps to provide reliable localization in all-weather condition, thus providing dependable tracking performance by the motion control. This work is important as it is the first public test of the automated road vehicle in the Arctic Circle ever done .

Umar Zakir Abdul Hamid, Aku Kyyhkynen, José Luis Peralta-Cabezas, Jari Saarinen, Harri Santamala

### Achieving Driving Comfort of AVs by Combined Longitudinal and Lateral Motion Control

As automated vehicles (AVs) are moving closer to practical reality, one of the problems that needs to be resolved is how to achieve an acceptable and natural risk management behaviour for the on-board users. Cautious automated driving behaviour is normally demonstrated during the AV testing, by which the safety issue between the AV and other road users or other static risk elements can be guaranteed. However, excessive cautiousness of the AVs may lead to traffic congestion and strange behaviour that will not be accepted by drivers and other road users. Human-like automated driving, as an emerging technique, has been concentrated on mimicking a human driver’s behaviour in order that the behaviour of the AVs can provide an acceptable behaviour for both the drivers (and passengers) and the other road users. The human drivers’ behaviour was obtained through simulator based driving and this study developed a nonlinear model predictive control to optimise risk management behaviour of AVs by taking into account human-driven vehicles’ behaviour, in both longitudinal and lateral directions.

Chongfeng Wei, Richard Romano, Natasha Merat, Foroogh Hajiseyedjavadi, Albert Solernou, Evangelos Paschalidis, Erwin R. Boer

### Combined Lateral and Longitudinal Control with Variable Reference Path for Automated Driving

This paper presents combined lateral and longitudinal trajectory control with variable reference path for autonomous vehicle. A longitudinal velocity controller is designed to determine whether the current velocity is appropriate for the real-time or planned path. A steering control algorithm has been constructed using Ackermann steering geometry based path tracking controller known as pure pursuit method. The pure pursuit algorithm calculates the steering angle using the characteristics of the Ackerman steering geometry of the vehicle. This algorithm is not suitable at high speed but robust against disturbance and is a good method to apply in normal autonomous driving situations. The risk of the current speed is analyzed through the predicted lateral acceleration. However, the predicted lateral acceleration will vary depending on the vehicle. Therefore, the accuracy of the predicted lateral acceleration is improved using an adaptive neural network algorithm. The proposed algorithm has been verified by computer simulation with two consecutive curvature roads in city driving. The verification results were quite satisfactory.

Dongpil Lee, Kyoungsu Yi, Matthijs Klomp

### Control of a Scaled Vehicle in and Beyond Stable Limit Handling

In this research a controller is developed that can control path-tracking both within and beyond stable limit handling. A controller is developed, based on the equations of motion of the nonlinear bicycle model. The performance of the controller is evaluated in both simulation and on a 1/10 scale radio controlled car. The controller is able to track a path in typical cornering conditions and let the vehicle enter and maintain a drift while remaining close to the desired path.

Mart Baars, Hans Hellendoorn, Mohsen Alirezaei

### Flow Field and Neural Network Guided Steering Control for Rigid Autonomous Vehicles

This paper studies the steering control for low-speed manoeuvring of autonomous ground vehicles. A guidance method combining flow analogy and a neural network model is proposed to produce the proper angular velocity for the vehicle, which can be used as a reference for the control of the steering wheel. In a previous study, fluid flow itself has shown outstanding global search capabilities in guiding the vehicle through complicated environments. But the vehicle is not always able to follow the motion of the flow due to the difference of their nature. In this paper, the heat flow analogy is used instead of fluid flow, and a neural network model is added upon the flow layer in order to produce a steering reference more suitable for a rigid vehicle. Simulated results demonstrate that, except for the branching situations, the proposed method is able to guide the vehicle towards its desired destination.

Mengxuan Song, Timothy Gordon, Yinqi Liu, Jun Wang

### Lateral Control Design for Autonomous Vehicles Using a Big Data-Based Approach

In the paper an improved Model Predictive Control (MPC) design is presented for autonomous vehicles. The improvement of the control design is based on big data analysis of the lateral vehicle dynamics. In the big data analysis, the decision tree algorithm, C4.5 is used to determine the stable regions of the vehicle. Moreover, C4.5 is extended with the MetaCost algorithm, which is able to weight the percentages of certain misclassifications. In this way, the safe motion of the vehicle can be guaranteed. The results of the big data analysis are states-sets, which are used as constraints in the MPC control design.

Dániel Fényes, Balázs Németh, Péter Gáspár

### Search-Based Motion Planning for Performance Autonomous Driving

Driving on the limits of vehicle dynamics requires predictive planning of future vehicle states. In this work, a search-based motion planning is used to generate suitable reference trajectories of dynamic vehicle states with the goal to achieve the minimum lap time on slippery roads. The search-based approach enables to explicitly consider a nonlinear vehicle dynamics model as well as constraints on states and inputs so that even challenging scenarios can be achieved in a safe and optimal way. The algorithm performance is evaluated in simulated driving on a track with segments of different curvatures. Our code is available at https://git.io/JenvB .

Zlatan Ajanovic, Enrico Regolin, Georg Stettinger, Martin Horn, Antonella Ferrara

### Driver Interventions in Critical Situations During Automated Driving

Highly automated vehicles control the lateral and longitudinal movement of the vehicle in defined use cases, without being monitored by the human driver. The amendment of the Vienna Convention on Road Traffic [1] allows such self-driving vehicles, but requires that the driver is able to switch off or to overwrite the automated system at any time. However, interventions by the driver can lead to critical situations, especially in highly dynamic driving situations. Therefore, this paper investigates at which point driver interventions during highly automated driving can be critical and how the driver can be assisted in order to avoid dangerous driver inputs. To answer these questions, this paper presents test group studies conducted in a driving simulator and a concept for an intervention assistance system.

Thang Nguyen, Steffen Müller

### Handling Dynamics of a Lightweight Solar-Electric Vehicle with Direct Yaw Moment Control

Electric vehicles are commercially becoming more popular due to their high efficiency and low emission capabilities. The electrification of the powertrain allows for more efficient layouts compared to conventional vehicles, such as the use of in-wheel motors. These motors present new opportunities when it comes to vehicle stability control as they can be driven and controlled individually. This paper investigates the vehicle handling dynamics of a lightweight solar-electric vehicle in comparison to a standard sized commercial vehicle with direct yaw moment control. The research is based on the Australian Technology Networks’ Bridgestone World Solar Challenge vehicle that will participate in the 2019 competition. The vehicle is rear wheel drive, with room for a driver and one passenger. To allow for space for the solar arrays the vehicle is considerably large compared to its weight. Conventional yaw controls commonly use yaw and/or sideslip as a control variable, this paper employs dynamic curvature as a control variable. The main goal to improve the yaw rate and sideslip as a result of improving the dynamic curvature variable was achieved. The dynamic properties and control response of the two vehicles are studied via co-simulation of Simcenter Amesim™ and MATLAB Simulink.

Anna Lidfors Lindqvist, Paul D. Walker

### A Reinforcement Learning Enhanced Fuzzy Control for Real-Time Off-Road Traction System

In deformable terrain conditions, the tire-surface gripping may be characterized by drastic, rapid, and frequent changes, and, thus, the response time of traction control systems (TCS) of off-road vehicles is crucial for real-time mobility improvements. To advance TCS performance, the time boundaries for the TCS response time is established in the paper based on a physical property of the transient tire traction force, which is the tire relaxation time constant. A Q-learning (QL) algorithm is synthesized to ensure the established time boundaries and to provide real-time TCS response. Then, the reinforcement learning algorithm is proposed to adjust parameters of a fuzzy logic controller (FLC). The proposed control method outperforms the straightforward reinforcement learning in terms of the smoothness of the output signal and control action while also ensuring the established time boundaries. The mathematical modeling and simulation study is applied to an open-link locomotion module described in the paper.

Vladimir Vantsevich, David Gorsich, Andriy Lozynskyy, Lyubomyr Demkiv, Sviatoslav Klos

### Trajectory Tracking of a Four-Wheel-Steering Vehicle on Harsh Road

Along with the development of technology, an increasing number of special unmanned vehicles are required to achieve complex mission. Trajectory tracking, as one of the key factors of unmanned technology, has emerged into engineer’s vision. Four-wheel-steering (4WS) is more flexible than front steering vehicle in many conditions. This study is focusing on achieving higher accurate trajectory tracking on complex ground with 4WS vehicle. The control of trajectory tracking can be obtained by using MPC method, adjusting front wheel angle and rear wheel angle independently. Computer simulations with 4WS dynamic model were used to support the analysis in this study. MATLAB/Simulink was also used to verify the reliability of the results. Finally, the control law of 4WS vehicle was tested on complex ground. By solving the problem of 4WS trajectory tracking, the backstepping algorithm exhibited higher efficiency and accuracy than traditional genetic algorithm. By solving the problem of 4WS trajectory tracking, the backstepping algorithm exhibited higher efficiency and accuracy than traditional algorithm. The process of 4WS vehicle trajectory tracking provides reference for relevant applications.

Fangwu Ma, Jiahong Nie, Liang Wu, Liwei Ni, Guangjian Xu, Weiwei Jia

### Dynamics, Control and Stability of Motion of Electric Scooters

Recently we are witnessing a boom in electric single-passenger vehicles for urban micro-mobility, and more and more companies are joining this business. However, this type of means of transport is not subject to regulations in many countries, what generates uncertainty and lack of protection of citizens, both users of these vehicles and possible third parties who might be involved in an accident. This type of single-person vehicles are usually based on the use of small diameter wheels as a rolling element. The modeling and computational analysis of its dynamic characteristics, as well as the study of its stability and, therefore, of the physical parameters that decisively influence it, are the object of this project. In particular, an scooter benchmark is presented.Single-track vehicles like bicycles and motorbikes are important subjects of research in vehicle dynamics. Therefore, the theoretical results for bicycles will be used for escooters, too. However, the parameters of bicycles and escooters are very different: The bicyclists are sitting on their vehicles while the scooters are standing. Moreover, the bicycles have big wheels with tires generating gyroscopic forces and escooters have only small often rigid wheels. The knowledge of how the main parameters of the model affect its stability and maneuverability will allow design modifications that may lead to safer vehicles and will result in the reduction of accidents in urban mobility through these vehicles.

Daniel García-Vallejo, Werner Schiehlen, Alfonso García-Agúndez

### Parameter Sensitivity Analysis of the Anti-rolling Performance of Straddling Type Monorail Vehicle

The straddling monorail transit is a novel rail transit and is employed as the primary urban rail transit in many cities. Because of the unique structure of straddling type monorail vehicle (STMV), the anti-rolling capacity should be designed specially and the key influence parameters should be analyzed. In this study, 13 influence parameters were obtained from the evaluation methods: height of buoyancy center, flexibility coefficient, and critical roll angle. Based on the factor analysis method, the influence weights of each parameter are calculated, and the comprehensive score is obtained. The results show: The anti-rolling stability of the STMV is closely related to the stability wheels. What’s more, the key influence parameters are vertical location of stabilizing wheels, lateral span of secondary suspension and pre-loads; negative correlation factors include the car body centroid and bogie centroid. Finally, the comprehensive score can numerically evaluate the anti-rolling stability of the monorail.

Chaoran Wang, Yuanjin Ji, Youpei Huang, Liuhui Ren

### Stochastic Sensitivity of External Impact Factors on the Straight-Line Performance of a Generic Motorbike

A race bike is made for the competition against others. The crucial criteria for success are the fastest time or the crossing of the finish line in front of the competitors. For technical development, we need more information than time or race position to improve the performance of a bike. The aim of the present work is to close the missing link between the racing world and the engineering world. For this, the model must be able to replicate the movement in the real environment including the right reaction to all external influences like different upstream flow conditions and road uncertainties. The present paper points out the most important impact factors for straight line performance. It is shown that variations in the upstream flow conditions as well as variations in the drag coefficient, can have the same effect on the top speed. The paper highlights the need for a better understanding of the upstream flow conditions directly on the test object.

Christoph Feichtinger, Peter Fischer

### The Construction of Risk Potential Driver Model for Obstacle Avoidance of Dynamics Subject

It is important to clarify the driver’s avoidance behavior regarding irregularly moving obstacles such as pedestrians, bicycles and so on. In driver support systems or the autonomous driving vehicles, it is considered that the driver model using risk potential is effective. However, it is not considering the dynamic characteristics of the object at obstacle avoidance. We have already clarified the control of the driver at obstacle avoidance and constructed the driver model using the risk potential. We remodeled into the driver model that can be calculated in real time. This driver model could describe the driving behavior for the static obstacle avoidance. However, at the moving obstacle avoidance, the driver model could only describe the driver to a certain level. It is necessary to clarify the driving behavior and describe in more detail. Therefore, we constructed the risk potential algorithm considering the dynamics or state of obstacles using Kalman filter. As the result, the constructed driver model expresses the driving behavior, and we proposed a new control algorithm using the risk potential considering the dynamic of obstacles.

Yuto Kobayashi, Ichiro Kageyama, Tetsuya Kaneko

### Lateral Vehicle Dynamics on Rutted Roads

A vehicle may experience lowly damped oscillations and stability issues when driving through a rut. The tire response to camber variations plays a decisive role in this phenomenon, which is known as wandering. Realistic ranges for the cornering, camber and other stiffnesses have been determined using a database with Magic Formula parameters for a large number of passenger car tires. A linear model is developed for a single wheel in a rut to analyze the parameters governing its stability. As a next step the stability of the single track vehicle model in a rut is evaluated. With this model the lowly damped wandering motion can be captured well. It is shown that the normalized camber stiffness of both the front an rear tire are decisive for vehicle stability. An analytical expression has been obtained to describe one of the stability boundaries.

I. J. M. Besselink, S. Achrifi, H. Nijmeijer

### Model Predictive Control for Evasive Steering of Autonomous Vehicle

For an autonomous vehicle, a steering controller is essential. Model Predictive Control (MPC) is frequently used for steering control because the performance is sub-optimal and it can take constraints into account. The usual model embedded in MPC for steering control is vehicle body dynamics without steering system dynamics because the response of steering system is fast enough to ignore in usual maneuvers. However, the dynamics of the steering system is not ignorable when a maneuver requires higher torque than a limit of an actuator of the steering system, such as evasive steering maneuvers. To handle this problem, the model embedded in MPC should consider the limit of the actuator with a simple structure for a low computational load. Therefore, this paper proposes a simple model of steering system dynamics that can provide information on the actuator without adding too many states. The proposed MPC is implemented with the steering model with usual vehicle body dynamics as in linear form. It shows better performance than a regular MPC in evasive maneuvers, which is confirmed in simulation and experiments with a scaled vehicle.

Wansik Choi, Hyun-Sik Nam, Byungjoo Kim, Changsun Ahn

### The Role of Human Sensory Dynamics in Car Driving

This paper presents some of the results of an extensive parameter study performed on a recently developed and validated driver-vehicle model incorporating human sensory dynamics. The study included examination of the role of the motion senses and visual senses, and how the contribution of each sensory channel depends on the nature of the driver’s steering task (disturbance rejection or target following). The results demonstrate significant potential for a driver model with sensory dynamics to provide a better understanding of human driving behaviour.

Christopher Nash, David Cole

### A Free-Trajectory Quasi-steady-state Optimal-Control Method for Minimum-Time Problems of Cars and Motorcycles

Minimum-lap-time problems are commonly solved employing quasi-steady-state models on a predetermined trajectory or dynamic models on a free (non-predetermined) trajectory. The current work deals with a third approach, that combines a free-trajectory minimum-lap-time method, together with a quasi-steady-state description of the vehicle. The method is based on the computation of the well known g-g diagrams, which summarise the quasi-steady-state performance of the vehicle. This information is employed for the solution of an optimal-control problem, that allows to determine the optimal trajectory. Numerical models of high complexity can be employed, since all their features (e.g. tyre limits, power limits, aerodynamic drag and downforce, suspensions, etc.) are included in the related g-g diagrams, and do not affect the complexity of the optimal control problem that need be solved. The method allows to employ even experimental g-g diagrams in place of numerical ones, and is suitable for application to both cars and motorcycles.

Matteo Veneri, Matteo Massaro

### Directional Stability of a Front Wheel Drive Passenger Car with Preemptive Use of the Direction Sensitive Locking Differential (DSLD)

The topic of this paper is the bigger picture of vehicle dynamics and handling characteristics of cars, with a focus on driving safety. More specifically, the directional stability gain obtained using the semi-active differential (DSLD) is experimentally verified in transient steering maneuvers using a prototype in a FWD Saab 9-3 Aero.Stemming from the obvious need to enable low speed maneuvering, the open differential was developed already in the beginning of the automotive era and it has ever since maintained a position as the unquestioned solution almost irrespective of the driving situation. However, due to the inherent compromise between low speed maneuverability and high speed stability in road vehicle design, there are fundamental benefits of locking the differential more or less preemptively during for example expressway driving.In recent decades electronic stability control (ESC) has become the go-to solution to improve driving safety by increasing the directional stability in transient maneuvers. However, similar but significantly greater stability gains can be accomplished by utilizing controllable differentials. All in all this means that the mentioned inherent compromise between maneuverability and stability can be circumvented and the overall handling characteristics of cars can be fundamentally improved.

Mathias Lidberg, Jonas Alfredson

### Dolly Steering Controller for Enhancing Low- and High-Speed Performance of High Capacity Vehicles

The adaptation of high capacity vehicles (HCVs) into existing commercial vehicle fleets have been considered a potential solution for reducing emissions, operational costs and infrastructure damages. However, due to increased length and number of articulations, there are challenges associated with HCVs with regard to their manoeuvrability at low-speeds and stability at high-speeds. This paper presents a Virtual Rigid Axle Command Steering control strategy for dolly steering, due to which both low- and high-speed performance of HCVs may be improved significantly compared to their conventional version with non-steered dolly. To demonstrate this, two HCVs, namely, A-double (tractor-semitrailer-dolly-semitrailer) and LHV-D (truck-dolly-semitrailer) are considered in this work.

Abhishek Singh Tomar, Abhishek Kalose, Karel Kural, Joop Pauwelussen

### Scaled Experiment with Dimensional Analysis for Vehicle Lateral Dynamics Maneuver

Scaled experiment with dimensional analysis is frequently used when large scaled experiment is limited due to the cost or high risk. Vehicle lateral dynamics tests require a lot of effort and resources. In particular, experiments of vehicles with possible accidents or excessive maneuvering have a high risk and thus require lots of resources. Therefore, those vehicle dynamics tests are frequently performed virtually using computer software. Nevertheless, experiments are much more appealing to prove the performance or efficacy of newly developed system or algorithms. Scaled vehicle experiments are a good alternative way to evaluate the developed system with a low risk and cost. For consistency between real sized experiments and scaled experiments, many parameters should be scaled but some natural parameters are cannot be scaled. The gravitational acceleration, which is an important factor for tire lateral slip, cannot be scaled down as the vehicle size is reduced and thus the usual scaled vehicles such as RC cars show non-slipping tire motions. We suggest some remedies to avoid such unrealistic behaviors in scaled vehicle tests.

Yeayoung Park, Byungjoo Kim, Changsun Ahn

### Validation of Driver Model Based Handling Quality Evaluation by Cerebral Blood Flow

The objective evaluation indexes are required for the development of ever better handling quality cars. The authors have proposed the identified first order lag time constant, $$\tau_{L}$$ in the driver model as a candidate of the indexes. This paper reports the result which shows the quantification possibility of the sensory evaluation by $$\tau_{L}$$ closely examining the correlation of $$\tau_{L}$$ with the brain activity estimated by driver’s cerebral blood flow measurement during vehicle control.

Hiromi Arisaka, Yuya Hirota, Yusuke Tanaka, Takatoshi Tsukano, Makoto Yamakado, Yoshio Kano, Masato Abe

### Vehicle Handling Indexes Mining and Consistency of Subjective and Objective Evaluation

Automobile becomes more and more personalized and humanized on the promise of safety, comfort, energy saving, environmental protection. This trend requires the OEM grasp the consumers’ functional demands and psychological needs clearly, cascade and predict the developing automobile’s performance accurately during the automobile design and development phase, and realize the top down design with modular, digital and intelligent technology. The handling is one of the key performance for vehicle dynamics, and the establishment of vehicle handling evaluation system is essentially a non-linear classification problem with big data, many-to-many and tight coupling. This paper is intended to explore a simple handling objective-index-mining method and establish a good-consistency of handling subjective and objective evaluation. The 12 core handling objective indexes are extracted and the consistency of the handling subjective and objective evaluation is up to 80% once the sample size is over 120 via the proposed mothed, and the reduced order model are derived with consistency of 70%.

Xinjie Zhang, Shuai Tang, Konghui Guo, Dong Chen, Wentao Li, Ke He

### Yaw Center Control of a Vehicle Using Rear Wheel Steering

Conventional rear wheel steering control strategies prioritize vehicle handling and stability using yaw rate control based on side slip angle. This paper presents a new method of determining a yaw rate target for a rear wheel steering system by shifting the yaw center of a target model reference vehicle. The linear bicycle car model reference is paired with a basic PI feedback controller to determine the target rear wheel angle. Analyses show that this simple controller that uses a single tunable value can have a large impact on yaw rate response. Advantages and applications of this yaw center control are discussed.

Mahmoud Mohsen Abdelfatah

### Development of Velocity Dependent Front Wheel Angle Relation Based on Tire Workload Distribution

During a cornering manoeuvre, in a vehicle equipped with Ackerman steering geometry, the inner tire operates at a higher slip angle relative to the outer tire. As lateral load transfer occurs, the potential of the inner tires to produce the lateral force reduces and with systems like active steering, the saturation of lateral force occurs even earlier. In order to have an ideal steering geometry, at low speeds the system should follow Ackerman geometry closely and at higher speeds it should follow anti-Ackerman geometry. The tire workload (TW) distribution is a critical variable to be analyzed to prevent tire force saturation. The present paper aims to formulate the wheel angle relation for front wheel steering based on tire workload distribution. The tire workload difference (TWD) between the steered wheels is chosen as the active variable to arrive at the wheel angle relation. To study the transient behavior of the vehicle with tire workload redistribution (TWR), the Mimuro plot is used. The developed wheel angle relation utilizes the tire forces effectively and the results show improved cornering performance of the vehicle. This type of study which accounts for balancing tire workload for both lower and higher cornering speeds based on wheel angle relation has not been reported earlier in literature.

G. Arjunbarath, P. V. Manivannan, C. Sujatha

### Integrated Control for Four-Wheel-Independent-Drive EVs’ Lateral Stability and Rollover Prevention

In order to improve the maneuverability of Four-Wheel-Independent-Drive (4WID) EVs with high center of gravity while guaranteeing rollover stability, a coordinated stability control system is proposed to maximize driving velocity and enhance vehicle stability in cornering. A nonlinear vehicle model is used in the supervisor controller to determine the control target and then model predictive control (MPC) is designed to mitigate the delay effect of vehicle dynamics and also take the combined slip effect into account. Numerical simulations have been conducted to evaluate the proposed stability control system, which show that vehicle maneuverability, lateral stability and rollover mitigation performance can be significantly improved.

Yuye Hou, Lu Xiong, Bo Leng, Zhuoping Yu

### On the Enhancement of Vehicle Handling and Energy Efficiency of Electric Vehicles with Multiple Motors: The iCOMPOSE Project

Electric vehicles with multiple motors allow torque-vectoring, i.e., the individual control of each powertrain torque. Torque-vectoring (TV) can provide: (i) enhancement of vehicle safety and handling, via the generation of a direct yaw moment to shape the understeer characteristics and increase yaw and sideslip damping; and (ii) energy consumption reductions, via appropriate torque allocation to each motor. The FP7 European project iCOMPOSE thoroughly addressed (i) and (ii). Theoretical analyses were carried out to design state-of-the-art TV controllers, which were validated through: (a) vehicle simulations; and (b) extensive experimental tests, which were performed at rolling road facilities and proving grounds, using a Range Rover Evoque prototype equipped with four identical on-board electric powertrains. This paper provides an overview of the TV-related contributions of iCOMPOSE.

Basilio Lenzo, Patrick Gruber, Aldo Sorniotti

### Virtual Tire Design/Assessment in the Early Vehicle Development Process

The choice of the optimal tire setup for a given vehicle is not a trivial task. Nowadays car manufacturers often collaborate with the tire manufacturers during the development phase of new vehicles in order to improve the quality of their final products. At the beginning of a new development project, vehicle engineers define the so called vehicle key performance indicators (KPIs) and respective targets that the vehicle has to achieve. Regarding tires, the most crucial point is to answer the following key questions:

Francesco Calabrese, Manfred Bäcker, Axel Gallrein, Shenhai Ran

### Roll Mode Change Due to Vehicle Speed and Its Effect on Yaw Natural Frequency

This paper classifies roll resonance into two kinds, and points out symbolic solutions of yaw natural frequency at each roll resonance. Firstly, this paper consider change of roll natural frequency ωx due to change of vehicle speed V. This paper points out that ωx is a roll mode around the roll axis on the low speed side, and a roll mode around the center of gravity on the high speed side. Furthermore, we define V of this boundary as Vb; Vb is a V where ωx and yaw resonance frequency ωn coincide. In addition, Vb of passenger cars is estimated to be about 90 [km/h]. Furthermore, this paper considers an influence of ωx change on ωn. As the reference for this consideration, we use the yaw resonance frequency ωn0 of well-known planar 2 DOF model. In the domain of V < Vb, this paper points out that ωn is about 1.3 times ωn0 and derives a symbolic solution of this ωn. On the other hand, this paper also points out that ωn is almost equal to w0 in the region of V > Vb. Strictly speaking, this ωn is slightly larger than ωn0, which corresponds to the symbolic solution that the author pointed out in the past.

Hideki Sakai

### The Effect of Suspensions and Racetrack Three-Dimensionality on the Minimum Lap Time of Motorcycles

The aim of this work is to analyse the effect of suspensions and racetrack three-dimensional features on the minimum-time performance of a full dynamic multibody model of a sports motorcycle. The optimal-control minimum-lap-time problem is solved with indirect methods on both a two-dimensional and a three-dimensional track model, and the results are compared. The effect of suspensions is also analysed.

Edoardo Marconi, Matteo Massaro

### Drift Control for Path Tracking Without Prior Knowledge of Drift Equilibria

This paper presents drift control for path tracking without prior knowledge of drift equilibria. Keeping the vehicle on the desired path while maintaining high side slip angle is a challenging task for not only professional drivers but also control systems. There are two issues which make path tracking with high side slip angle difficult. First, the driver or control system must maintain the vehicle states on the drift equilibrium. Second, the control inputs to maintain drifting must also stabilize the path tracking error dynamics. In the previous researches, pre-calculated drift equilibrium was utilized to design the path and maintain the drifting. However, an accurate tire model is needed to calculate drift equilibrium. The novelty of this work lies in the path tracking algorithm without knowledge of drift equilibria. The proposed algorithm consists of three consecutive parts. First, the supervisor determines desired yaw rate to stabilize the path tracking error dynamics considering path tracking error state constraints. Second, the upper level controller determines desired lateral force to track desired yaw rate and desired longitudinal force to keep rear wheels spinning. Third, lower level controller converts desired forces to actuator inputs, steering wheel angle and accelerator pedal input. The performance overall control algorithm has been investigated via simulations while the performance of upper and lower level controller has been investigated via vehicle tests. It can be shown that the proposed algorithm is capable of tracking basic desired path without any prior knowledge of drift equilibrium. Furthermore, the vehicle test results for upper and lower level controller show that the part of algorithm is capable of tracking yaw rate while maintaining high side slip angle.

Eunhyek Joa, Kyongsu Yi

### The Significance of Roll on the Dynamics of Ground Vehicles Subjected to Crosswind Gusts by Two-Way Coupled Simulation of Aero- and Vehicle Dynamics

Improvements in vehicle technologies in recent decades enable the use of lighter materials and the development of control systems for autonomous vehicles. However, these improvements lead to a need for better understanding of how flow phenomena affect crosswind stability of ground vehicles which will enable the design of the less wind-sensitive vehicles. Therefore, the present study investigates the significance of roll on the dynamics of ground vehicles subjected to crosswind gusts. It includes a multidisciplinary approach in which there is a two-way coupled simulation between aerodynamics and vehicle dynamics equations. As a result of the investigations, significant differences have been found between the computations considering no-roll and roll motions.

Tural Tunay, Ciarán J. O’Reilly, Lars Drugge

### Evaluation of Frequency Response Characteristics on “g-g” Planes by Using Quasi-steady State Analysis

This study investigates a methodology to visualize the representative motion characteristics with consideration of running conditions, as well as the quantitative effects of the fundamental specifications for the vehicle dynamics. Frequency response is a method of evaluating the dynamic characteristics of a vehicle by examining the vehicle-motion response to steering input. Additionally, the proposed methodology considers running conditions which are represented by longitudinal and lateral accelerations, the response characteristics are visualized on “g-g” planes. Quasi-steady state cornering is assumed so as to calculate the characteristics with consideration of horizontal acceleration. Moreover, sensitivity is defined to evaluate the quantitative effect of a design parameter on a characteristic value which is the gain or phase of the frequency response, and the design parameters indicate the vehicle fundamental specifications in this study. It is also possible to visualize the sensitivities on “g-g” planes. The proposed methodology indicates relationships between the characteristics and the design parameters of a vehicle. This contributes to exploring a good design solution efficiently without many design iterations.

Takatoshi Tsukano, Yoshio Kano, Makoto Yamakado, Masato Abe

### Design of an Improved Robust Active Trailer Steering Controller for Multi-trailer Articulated Heavy Vehicles Using Software/Hardware-in-the-Loop Real-Time Simulations

This paper presents a robust active trailer steering (ATS) system for Multi-Trailer Articulated Heavy Vehicles (MTAHVs) using Software/Hardware-In-the-Loop (SHIL) Real-Time (RT) simulations. The Linear Quadratic Regulator (LQR) technique was applied to ATS controller designs. In the designs, vehicle parameters are assumed to be constant. In reality, these parameters may vary. Thus, the robustness of the LQR-based controllers is questioned. To address the problem, a robust controller was designed using a Linear Matrix Inequality (LMI) based LQR method. To evaluate the robustness of the LMI+LQR-based controller, the directional performance of an A-train Double was simulated [1]. However, the ATS actuator model is not realistic, and trailer payload variation was not considered. In the current research, an improved LMI+LQR-based controller is designed considering the uncertainty of a hydraulic ATS actuator and trailer payload variation. The robustness of the improved controller is demonstrated by evaluating the directional performance of a B-Train Double.

Mutaz Keldani, Yuping He

### Effect of Floating Bridge Motion on Vehicle Ride Comfort and Road Grip

The aim of this paper is to investigate the influence of floating bridge motion on bus driver’s ride comfort and road grip for the straight concept solution across Bjørnafjorden. For this investigation 3 degrees of freedom (DOF) bus model is defined for numerical simulation. Bus model has been excited by vertical motion of the bridge for four different bus speeds. Ride comfort has been assessed according to method and criteria proposed by International ISO 2631/1997 standard. For road grip assessing Dynamic Load Coefficient (DLC) has been used. It has been concluded that on floating bridge ‘little uncomfortable’ ISO 2631 criteria is reached at lower bus speed comparing to stationary ground road. Higher values of DLC for the case of floating bridge points out higher variation in vertical tyre forces (worse road grip). For bus speed at 90 km/h, DLC for floating bridge is approximately 0.08 which is 7% higher value comparing it to the case of stationary road.

Dragan Sekulic, Bengt Jacobson, Stian Johannesen Moe, Erik Svangstu

### Quarter Car Test Rig for Extended Dynamics Research in Laboratory Conditions

In the research of vehicle dynamics various specialized test rigs are designed for specific elements or systems analysis. Expecting the reliable results all possible uncertainties and side effects should be known in advance. In this paper the analysis of special designed quarter car test rig is presented before its further use in wheel/tire, suspension or its complex research. After explaining the construction, its operation and application an experimental modal analysis and validation of test rig with on-road driving was done in order to find out any uncertainties. Different performance in separate frequency ranges of specific construction locations is identified. This is explained by the influence of unsymmetrical inner frame, suspension side mounting and wheel rotation dynamics. Finally further research possibilities using designed test rig and its options for vehicle components and separate systems including control strategies are presented proving the importance of reliable dynamic tests in laboratory conditions before on-road driving.

Vidas Žuraulis, Artūras Kilikevičius

### The Mechanism Research of Body Sway of Car-Trailer Combinations Considering Steering System Characteristics

Body sway is a common dynamic instability phenomenon in automotive engineering. It is more likely to occur in car-trailer combinations than in the passenger cars because of the coupling between the towing car and the trailer. The corresponding theoretical studies have been carried out to find the mechanism of body sway. Most theoretical studies mainly focus on the suspension subsystem and wheel subsystem, but the influence of steering system characteristics is often neglected. In this paper, a theoretical model with 6 DOFs of CTCs is established by Lagrange equation. The stiffness, damping and dry friction of the steering system are considered in this model. The dynamic stability of CTCs is indicated by the system dynamic critical speed. The dynamic analysis becomes more complex because of the introduction of the nonlinearities of tire and dry friction. The steering characteristics have different influences on the dynamic critical speed. Especially, the excessive dry friction does harm to the dynamic stability of CTCs. The effect chain between the steering system characteristics and body sway of CTCs could be revealed through theoretical analyses and the simulation study.

Ning Zhang, Tian Li, Jian Ma, Guo-dong Yin

### An Architecture of Hardware and Driver in the Loop Simulation for Electric Power Assisted Steering System

This paper introduces an architecture for virtual development of electric power assisted steering (EPAS) system, which is implemented at Volvo Cars. The architecture involves an EPAS power pack rig and driver in the loop, so engineers can test both the ECU software and electric motor on a virtual prototype vehicle. Effective results are shown for tests in low-mid frequency and at mid-high vehicle speed. Currently, the high frequency and low speed test is still challenging due to vibration and instability, which should be addressed by the control improvement.

Weitao Chen, Matthijs Klomp, Utsav Khan, Andrea Bianchi, Shenhai Ran, Bengt Jacobson

### Real-Time Minimum-Time Lane Change Using the Modified Hamiltonian Algorithm

A minimum-time lane change maneuver is executed under friction-limited conditions using (1) the Modified Hamiltonian Algorithm (MHA) suitable for real-time control and (2) numerical optimization for comparison. A key variable is the switching time of the acceleration reference in MHA. Considering that MHA is based on an approximate vehicle model to target real-time control, it cannot exactly match the ideal reference as obtained from offline optimization; this paper shows that incorporation of a limited-jerk condition successfully predicts the switching time and that the desired lane position is reached in near minimum time.

Victor Fors, Yangyan Gao, Björn Olofsson, Timothy Gordon, Lars Nielsen

### Real-Time Capable Nonlinear Model Predictive Wheel Slip Control for Combined Driving and Cornering

This paper presents a traction controller for combined driving and cornering conditions, based on explicit nonlinear model predictive control. The prediction model includes a nonlinear tire force model using a simplified version of the Pacejka Magic Formula, incorporating the effect of combined longitudinal and lateral slips. Simulations of a front-wheel-drive electric vehicle with multiple motors highlight the benefits of the proposed formulation with respect to a controller with a tire model for pure longitudinal slip. Objective performance indicators provide a performance assessment in traction control scenarios.

Mathias Metzler, Alessandro Scamarcio, Patrick Gruber, Aldo Sorniotti

### Cooperative Game Based Obstacle Avoidance Control by Integrating the Steering and Braking Systems

This paper proposes a novel cooperative control strategy based on the game theory for the emergency obstacle avoidance (EOA) by integrating the steering and braking based chassis subsystems. The aim is to deal with the interaction conflicts between the two action subsystems which have asymmetric control power, when tracking the target trajectory for the obstacle avoidance. The cooperative game theory is adopted to model the interaction between the steering and braking based subsystems, which are treated as two players in the game. A cost normalization method is proposed to handle the big difference of the cost function defined in the framework of cooperative game between the two players. Then, an improved Nash bargaining solution concept is used to determine the optimal control authority of the two subsystems. Co-simulation is performed under a double lane change maneuver to verify the effectiveness of the proposed control strategy. The results show that a more reasonable control authority is assigned by the proposed method, the vehicle can well track the desired trajectory for EOA with the cooperative game-based control strategy.

Kaixing Xiao, Shaobo Lu

### Integrated Chassis Control for Improved Braking Performance on Rough Roads

The deterioration of ABS braking performance on rough roads is well established in the literature. Large variations in tyre normal force during braking is one of the main contributors to this deterioration. Reducing the tyre normal force variation by controlling the suspension characteristics may thus improve the braking performance on rough roads. This paper proposes a novel algorithm that can be used to reduce tyre normal force variation through semi-active suspension control. The algorithm consists of three stages, firstly estimating the road input, secondly predicting the suspension force, and thirdly identifying suspension settings that may reduce suspension force variation and hence tyre normal force variation. The effect of the algorithm is investigated by using an experimentally validated vehicle simulation model on experimentally measured road profiles. Simulation results show that the stopping distance from 80 km/h on a Belgian paving can be reduced on average by 1.3 m.

Herman A. Hamersma, P. Schalk Els

### Exploring Active Camber for Path Following and Yaw Stability of Autonomous Vehicles

This paper explores active camber for path following and yaw stability control of over-actuated autonomous electric vehicles (AEVs). The camber effect on tyre force is modelled with a modified Dugoff tyre model, where the influence of tyre slip on camber stiffness is considered. Additionally, a nonlinear vehicle model including the longitudinal, lateral and yaw motion of the vehicle and the rotational motion of the wheels is utilised. The control problem of the AEVs is formulated with model predictive control, where both actuator- and safety-related constraints are considered. Comparative studies show that with four-wheel camber control the path following and yaw stability performance of the AEV can be considerably improved.

Wenliang Zhang, Lars Drugge, Mikael Nybacka, Zhenpo Wang

### Coordinated Control of Slip Prevention and Energy Management for Four-Wheel-Drive Hybrid Electric Vehicles

For a hybrid electric vehicle (HEV), traction control ensures vehicle safety while energy management improves the fuel efficiency. Since the two strategies both control the torque distribution, the coordination between them is necessary. Therefore, a multi-objective optimization strategy is proposed to concurrently optimize the dynamic performance, slip rate and energy consumption of an HEV. First, an improved vehicle speed estimation method based on the characteristics of the adhesion curves is proposed to accurately estimate the vehicle speed and slip rate. Second, the Gaussian process regression is introduced to identify the tire model and extract the global features of the adhesion curve. Finally, the multi-objective optimization problem is proposed and solved by the technique for order preference by similarity to ideal solution. The strategy outputs torque distribution between the engine, the motor and the brakes. The simulation results show that the proposed strategy can reduce the slip times compared with sliding mode control. Meanwhile, the energy economy is improved because the additional energy consumption caused by slip control is reduced.

Jingni Yuan, Lin Yang, Yixin Yang

### Researches on 4WIS-4WID Stability with LQR Coordinated 4WS and DYC

Four-wheel independent steering and four-wheel independent driving electric vehicle (4WIS-4WID EV) has more control degrees of freedom (DOF). It benefits to realize torque allocation and differential steering control. Therefore, four wheel steering technology (4WS) and direct yaw control (DYC) are important research direction of vehicle stability. This paper designed a kind of novel adaptive linear quadratic optimal regulator (LQR) as a coordination controller for 4WIS-4WID EV stability control with 4WS and DYC. The deviation between the real value and ideal value is obtained and delivered to LQR controller. According to different speed and road surface conditions, sideslip angle β and stable area are calculated using phase plane method. The weight matrix Q and R of LQR controller is adaptive to velocity, adhesion coefficient and the $$\beta - \dot{\beta }$$ phase plane. The performance of adaptive LQR is simulated in MATLAB/Simulink and Carsim platform. Compared with no control, 4WS, DYC, and fixed LQR strategies, the results show that the adaptive LQR controller with weight matrix adaption has better performance than the outputs form DYC, 4WS and fixed LQR in stability.

Xinbo Chen, Yanqun Han, Peng Hang

### Robust Adaptive Anti-lock Braking Controller Design

To ensure steering ability and maximize tire-road friction, a robust wheel slip controller is developed for antilock braking system, which is also adaptive to different road conditions. Aiming at the problem of vehicle velocity estimation, a dynamic and kinematic fusion method is proposed. Meanwhile, a non-affine parameter estimator is adopted to estimate road condition using improved Burckhardt model, the optimal target slip ratio is adaptive adjusted according to the estimate road condition. Then conditional integration method is used to make the wheel slip ratio converge to the desired value considering the uncertainty of parameters and constraints of actuators. Finally, simulation results under multi working conditions show that the proposed control approach is adaptive to road change and good performance is achieved that can prevent wheels from locking effectively.

Lu Xiong, Xing Yang, Bo Leng, Guirong Zhuo

### Recent Advancements in Continuous Wheel Slip Control

The paper presents an overview of continuous wheel slip control (WSC) methods as the part of anti-lock braking system (ABS) for the several vehicles configurations with friction brakes and electric motors. Performance of proposed WSC design variants using several control techniques has been experimentally evaluated for three different test vehicles: Sport Utility Vehicle (SUV) with decoupled electro-hydraulic brake (DEHB) system, SUV with four individual on-board electric motors (OBM), and compact vehicle with four individual in-wheel motors (IWM). Obtained results demonstrated that proposed continuous WSC variants provide a simultaneous effect on braking efficiency and ride quality as well as robust operation in various road conditions. Presented summary provides outlook on future perspectives of the continuous WSC and compares its status with conventional rule-based ABS systems.

Dzmitry Savitski, Valentin Ivanov, Klaus Augsburg, Barys Shyrokau, Hiroshi Fujimoto

### The Influence of Tyre Lateral Force for Control Allocation of Yaw Torque

The present paper provides a thorough analysis and reveals the yaw torque generated by tyre lateral forces, due to the well-known combined slip effect. The indirect yaw torque here is captured by a tyre model simplification designed for the real-time control allocation purpose. Experiments were carried out by a driving robot, controlling steering wheel, gas and brake pedal at various manoeuvres. The test vehicle is equipped with high precision measurement-wheel mounted at each wheel. It was found that the simplified model correlates with the experimental results, where the relation between the wheel torque distribution of front/rear axles and the yaw torque generated by tyre lateral forces are highly dependent on the vehicle lateral acceleration and drive torque request.

Derong Yang, Mats Jonasson

### Torque Vectoring Control on Ice for Electric Vehicles with Individually Actuated Wheels

Recent studies on torque vectoring control for electric vehicles proposed various efficient solutions demonstrating improvement of vehicle stability for evasive manoeuvres. However, the torque vectoring on very low friction surfaces such as black ice or wet snow is rarely investigated, especially for the electric vehicles with off-road capability. The presented study contributes to this topic by laying the groundwork for further advanced torque vectoring designs. Within the framework of this paper, the target vehicle is a sport utility vehicle equipped with four on-board electric motors controlling each wheel separately. The functionality of the developed controllers is tested under hardware-in-the-loop simulations for icy road conditions. For this purpose, the tyre model has been parameterized and validated based on the experimental data conducted on a unique terramechanics test rig at Virginia Polytechnic Institute and State University. The test results confirm very good functionality of the developed controllers and demonstrate an improvement of the electric vehicle driving performance.

Timur Agliullin, Valentin Ivanov, Vincenzo Ricciardi, Manuel Acosta, Klaus Augsburg, Corina Sandu, Barys Shyrokau, Dzmitry Savitski

### Influence of System Dynamics in Brake Blending Strategies for Electric Vehicles

Regenerative and friction braking blending strategies need to consider both system dynamics in order to optimize their performance. Usually, the priority in electric vehicles is battery regeneration through electric braking instead of friction braking. This work studies the dynamics of both systems and proposes an optimized brake-blending strategy. The goal is to maximize regeneration without affecting safety. Both dynamics are studied separately with commercial systems: electric drivetrain and friction brake-by-wire. The proposed strategy takes into account temporary response as well as the physical limitations of the systems. Therefore, this strategy limits the influence of the slowest system, in our case, the electric one, during the braking process while maximizing battery regeneration.

Javier Pérez Fernández, Juan María Velasco García, Manuel Gonzalo Alcázar Vargas, Juan Jesús Castillo Aguilar, Juan Antonio Cabrera Carrillo

### Evaluation of Combined Energy-Efficient and Stability Strategies Utilising Direct Yaw Moment Control

For sustainability reasons it is important to reduce energy consumption during driving. One contribution to energy savings is by using proper wheel torque distributions during manoeuvring. An active energy-efficient direct yaw moment control (DYC) for electric vehicles has previously been proposed by the authors, taking the motor efficiency map into consideration. The results show a potential for reduced energy losses during driving, but it might result in stability problems during safety-critical maneuvres. In this work, consequences on stability due to this proposed energy efficient DYC is explored. Also an approach combining DYC both energy-efficiency and stability is proposed. The simulation results show that for the studied case the combination of DYC for energy-efficiency and stability can have an potential to both keep the vehicle safe and save considerable percentage of energy during both non safety-critical and safety-critical driving manoeuvres.

Peikun Sun, Annika Stensson Trigell, Lars Drugge, Jenny Jerrelind

### Towards the Limits of Vibration Attenuation in Drivetrain System by Torsional Dynamics Absorber

Automotive industry drives development towards down-sized and down-speeded engines and higher cylinder pressure. This leads to increased torsional vibrations and therefore puts higher demands on the drivetrain vibration capabilities. The paper presents the results on the study of the limits of torsional dynamics absorbers for vibration attenuation in drivetrain systems obtained by using global sensitivity analysis and multiobjective optimization. The global sensitivity analysis comes with a mapping between the total sensitivity indices of the vibration attenuation measures of a drivetrain system and mass-inertia, stiffness and damping parameters of a torsional dynamics absorber. The multiobjective optimization is resulted in Pareto fronts showing the trade-off between the measures of vibration attenuation and energy losses making possible to identify the limits of the quality of performance of a torsional vibration absorber for a drivetrain system operating on a set of engine input loads. Detailed numerical results are presented on study of application of a dual mass flywheel for heavy-duty truck drivetrain systems in operating engine speed range up to 2000 rpm. The third engine order vibration harmonic is in focus of analysis as one of the most significant contribution to the oscillatory response in drivetrains of heavy-duty trucks.

Viktor Berbyuk

### Vehicle Sideslip Angle Estimation Using Disturbance Observer

Vehicle sideslip angle is an important signal related to lateral stability and essential for active safety control systems. Since direct measurement of sideslip angle requires expensive equipment, it should be estimated in a feasible way for implementation. This paper describes a novel cost-effective strategy of sideslip angle estimation using a disturbance observer. In this approach, modeling errors of a linear vehicle model are treated as unknown lumped disturbance, which is estimated by the disturbance observer. Simultaneously, a Luenberger observer estimates the sideslip angle and yaw rate. This method requires only simplified tire model and currently-available sensor measurements such as yaw rate, lateral acceleration, steering angle and longitudinal speed. The estimation performance of the proposed observers has been verified by comparing with an interacting multiple-models (IMM) approach via computer simulation studies using vehicle experimental data. The simulation results show effective and robust estimation performance of the proposed observer under various road surfaces.

Baek-soon Kwon, Kyongsu Yi

### Influence of the Prediction Model Complexity on the Performance of Model Predictive Anti-jerk Control for On-board Electric Powertrains

Anti-jerk controllers compensate for the torsional oscillations of automotive drivetrains, caused by swift variations of the traction torque. In the literature model predictive control (MPC) technology has been applied to anti-jerk control problems, by using a variety of prediction models. However, an analysis of the influence of the prediction model complexity on anti-jerk control performance is still missing. To cover the gap, this study proposes six anti-jerk MPC formulations, which are based on different prediction models and are fine-tuned through a unified optimization routine. Their performance is assessed over multiple tip-in and tip-out maneuvers by means of an objective indicator. Results show that: (i) low number of prediction steps and short discretization time provide the best performance in the considered nominal tip-in test; (ii) the consideration of the drivetrain backlash in the prediction model is beneficial in all test cases; (iii) the inclusion of tire slip formulations makes the system more robust with respect to vehicle speed variations and enhances the vehicle behavior in tip-out tests; however, it deteriorates performance in the other scenarios; and (iv) the inclusion of a simplified tire relaxation formulation does not bring any particular benefit.

Alessandro Scamarcio, Mathias Metzler, Patrick Gruber, Aldo Sorniotti

### An Investigation of Longitudinal Tyre Force Observation for Slip Control System Development

Longitudinal tyre force is needed in the feedback control systems for enhancing the decelerating and accelerating properties of road vehicles. There lacks means for its direct measurement. This paper presents a longitudinal tyre force observer, designed on wheel rotating dynamics using the conventional linear control systems theory with wheel speed and drive/brake torque. The observer is formulated firstly in continuous-time and then converted to an implementable form in discrete-time for compatibility with digital electronic control units (ECUs). The effectiveness and applicability of the observer are investigated using numerical simulations and road testing of an 8 × 4 Volvo truck with each wheel equipped with an ECU consisting of, in C-code, a robust slip control system, a tyre-road friction estimator, a brake pressure observer and the longitudinal tyre force observer for application in an intelligent brake system. The robustness of the observer to parametric uncertainties, e.g., the inertia of moment, effective radius, and brake gain of the wheel, is also examined.

Shenjin Zhu, Leon Henderson, Edo Drenth, Fredrik Bruzelius, Bengt Jacobson

### Estimation of States and Parameters with Dual Extended Kalman Filters for Active Roll Control

This paper presents a method that designs dual extended Kalman filters (EKFs) for active roll control. There are two Kalman filters: state and parameter estimators. The roll angle of a vehicle is estimated by the state estimator with roll rate measurement. It has been well known that the recursive least square (RLS) or parameter estimation scheme can be represented with Kalman filter. Using the fact, the parameters of a vehicle model are estimated by the parameter estimator using the estimated roll angle. Simulation and experiments are done to validate the proposed dual EKFs for active roll control.

Seongjin Yim, Jaewon Nah, Manbok Park

### Vehicle Sideslip Estimation for Four-Wheel-Steering Vehicles Using a Particle Filter

The availability of the most relevant vehicle states is crucial for the development of advanced vehicle control systems and driver assistance systems. Specifically the vehicle sideslip angle plays a key role, yet this state is unpractical to measure and still not straightforward to estimate. This paper investigates a particle filter approach to estimate the chassis sideslip angle of road vehicles. The filter relies on a physical model of the vehicle and on measurements available from cheap and widespread sensors including inertial measurement unit and steering wheel angle sensor(s). The approach is validated using experimental data collected with the research platform RoboMobil (RoMo), a by-wire electric vehicle with wheel-individual traction and steering actuators. Results show that the performance of the proposed particle filter is satisfactory, and indicate directions for further improvement.

Basilio Lenzo, Ricardo De Castro

### Sideslip Angle Estimation Using a Kinematics Based Unscented Kalman Filter and Digital Image Correlation

Vehicle sideslip is an important input parameter that can be used to improve vehicle stability control. The sideslip angle is seen as a measure of vehicle lateral stability. This paper presents an inexpensive sideslip angle measurement algorithm which incorporates direct measurements and a kinematics-based model for sideslip estimation. The estimation algorithm uses Digital Image Correlation (DIC), to directly measure sideslip with a real-time sparse optical flow algorithm, and an Unscented Kalman Filter (UKF) to remove drift from the kinematics-based estimator. The method smooths the direct measurements from the DIC and other sensors while being independent of vehicle geometry.

Wian Botes, Theunis R. Botha, P. Schalk Els

### An Investigation on the Effect of Lateral Motion on Normal Forces Acting on Each Tires for Nonholonomic Electric Vehicle: Experimental Results Validation

Electric vehicles are gaining popularity among people since it is environmentally friendly and carves a path for a better autonomous vehicle. Furthermore, EVs with in-wheel motors tend to provide better torque control since the current for each motor can be defined precisely. The torque of each wheel is controlled to ensure effective traction to ensure vehicle stability. The traction of the wheels is closely related to the vehicle mass. The previous study shows that lateral motion exerts more normal force on the inner wheels of the vehicle. An experimental study is done using a small scale EV fitted with accelerometers to detect the acceleration experienced at each tire. The longitudinal and lateral acceleration is used with the load transfer equation to estimate the normal force exerted at each tire. The results show that increasing vehicle velocity at the same road curvature induces more load transfer towards the inner tire. Furthermore, the experimental results show that the simulation model is accurate and valid.

K. Baarath, Muhammad Aizzat Zakaria, Mohamad Heerwan Bin Peeie, Umar Zakir Abdul Hamid, A. Fakhri A. Nasir

### A Novel Vehicle Localization System Using Vision Module for Heading Feedback

Traditional vehicle localization systems use GNSS signals for global localization or Lidar or vision based systems for Simultaneous Mapping and Localization (SLAM). However, the signals of GNSS might be contaminated or even blocked in areas where there are tall buildings or trees, especially for autonomous sweeper vehicles that usually work along the road. There are additional information that can be used to improve the accuracy and robustness of vehicle localization system when applied in autonomous sweeper vehicles. Thus, a novel vehicle localization system based on GNSS, vision, wheel speed and Inertial Measurement Unit (IMU) is proposed. When the vehicle works in areas where GNSS signals are good, accurate position information from GNSS is used. Besides, wheel speed and IMU information is fused to improve the output rate of position information. When the vehicle enters areas where GNSS signals are unavailable, the heading information from vision is used as measurement to estimate the heading angle of vehicle and then fused with wheel speed and IMU to estimate the position. Real vehicle experiments are conducted to validate the effectiveness of the proposed system.

Yishi Lu, Lu Xiong, Yanqun Han, Letian Gao

### Model Based Vehicle Localization via an Iterative Parameter Estimation

This paper proposes a novel method for the estimation of the wheel circumferences, which have significant effects on a vehicle model based localization. One of the advantages of the method is that only cost effective onboard sensors, such as GPS, magnetometer, IMU and wheel encoders are used. Moreover, the estimation methods based on pure vehicle models can result in suitable localization, when other solutions are not effective i.e. the GPS signals are not available or other sensors are inaccurate, such as IMU measurements with low, constant velocity. The presented off-line algorithm has three main layers connecting the Kalman-filter and Least Squares based estimation processes in an iterative way. During the procedure the side-slip is estimated, which has a significant impact on the dynamics of the vehicle and the further estimations. Since in the method all of the measurements are used at once and the side-slip is also calculated, a highly accurate identification with low sensitivity on the noise can be reached. The efficiency of the vehicle model calibration is presented through CarSim simulations.

Máté Fazekas, Balázs Németh, Péter Gáspár

### Payload Estimation in Excavators Using a Machine Learning Based Parameter Identification Method

This paper documents a part aspect of a broader work, where the goal is to develop a self-sufficient method for continuous and dynamic payload estimation for hydraulic excavators. Self-sufficiency here implies that the required unknowns are either measurable or can be identified using simple sensors. Results from field tests have showed that the approach for identification in its basic form is easy to implement which comes at the cost of diminished estimation accuracy, especially concerning the moment of inertia and friction behavior. Specifically, this paper covers the work done regarding application of machine learning methods to improve the accuracy and reliability of the identification approach, thereby consequently improving the accuracy of the payload estimation.

Ashwin Walawalkar, Steffen Heep, Martin Frank, Christian Schindler

### A Comparison of Different Mathematical Bus Dynamics Models to Evaluate Road Roughness and Ride Comfort

Improving ride comfort for bus passengers experiencing vibrations under the excitation of road roughness is a meaningful solution to attract more public transport ridership. While many research studies have been conducted to simulate car and truck dynamics, few studies have studied bus dynamics. This study developed multi-degrees-of-freedom (3-DOF quarter, 5-DOF half and 9-DOF full) mathematical bus models in Matlab/Simulink and compared these models in calculating passenger ride comfort on buses operating along urban bus lanes. The comparison results have shown that the 9-DOF full bus model is the best alternative to measure passenger ride comfort within the error of 2%, as compared to 5-DOF half and 3-DOF quarter bus model with 7% and 20% error, respectively. However, the modelling complexity is much higher in cases of half and full bus models. The widely used quarter vehicle model for designing vehicle suspension and for evaluating road roughness are reasonable and pragmatic to minimise the complexity.

Teron Nguyen, Patrick Swolana, Bernhard Lechner, Yiik Diew Wong

### Design of a Multi-link Suspension for Motorcycles with a Sidecar

For motorcycles, various suspension concepts for the front steerable wheel have been developed over decades. Even if the telescopic front fork has been eventually established as a common design, other alternative designs are still being evolved. A design of such an alternative - a multi-link suspension, particularly utilised for motorcycles with a sidecar, is discussed in the present paper. Beside some modelling aspects, optimisation of suspension’s kinematics and benefits of an asymmetric layout for left and right cornering are elaborated.

Jakub Tobolář

### Quantification of Infant Car Seat Vibration over a Mission Profile

Little is known about the effect of vibration associated with vehicle travel on the comfort and health of infants. Variations in vehicle speed associated with travelling under typical suburban driving conditions influence the vibrational response of the vehicle body, which affects the vibration transferred to an infant. The aim of this investigation is to quantify the vibration of an infant car seat over a mission profile. The translational and rotational acceleration of the car seat was measured during 15 repeated runs and weighted according to BS 6841(1987). The mission profile resulted in a range of different translational and rotational vibrations of the infant car seat for the various sections of the mission profile. Vertical acceleration was the largest of the accelerations encountered along the mission profile. The variations in the infant car seat vibrations were quantified by the relative difference. The sections of the mission profile have a median relative difference of 15.59%, with an interquartile range of 17.49% ($$IQR = 75^{\text{th}} \;{\text{percentile}} - 25^{\text{th}} \;{\text{percentile}} = 27.38\% - 9.89\%$$), with large relative differences (>80%) observed for traffic lights. Approximately 58% of the sections of the mission profile indicated relative differences greater than the relative difference threshold of the 75th percentile adult occupant. Therefore, these variations are most likely large enough for certain sections of the mission profile to subject participants to different stimuli and, in turn, result in different cardiorespiratory responses.

Moniqué van der Westhuizen, Cor-Jacques Kat, Schalk Els

### Realization of Adjustable Damping Characteristic Based on a Magnetorheological Damper

In order to improve the efficiency of damping characteristic adjustment for vehicle suspension shock absorber, the control system with a magnetorheological (MR) damper was proposed to realize the adjustable damping characteristic. The Bingham model of a MR damper was establish based on the damping force of the MR damper under different sinusoidal excitations and different currents. The force-velocity curves of dampers were described with a mathematics model. The whole slope and the curvature of the damping force-velocity curves were represented by separate parameters and could be adjusted independently. An embedded control system was developed to adjust damping characteristic with a speed sensor, a microprocessor, a damping characteristic adjustment module, a MR damper and a current driver. The current driver was designed by taking the voltage Pulse Width Modulation (PWM) as the excitation signal. The verification experiment shows that the overall slope and the rate of curvature change for the peak damping force-velocity curve could be adjusted in a little time delay by this control system.

Zhifei Zhang, Hongwei Lu, Zhongming Xu, Yansong He

### Preliminary Selection and Parameter Optimization of Nonlinear Parallel Suspension Based on Vehicle Ride Comfort

In this paper, a novel method for preliminary selection and optimization of nonlinear parallel suspension is proposed. The research object of this paper is an auto-guided container transfer vehicle (AGV), which needs to meet the demand of lifting a short distance of the container. A new parallel suspension with rubber spring and hydro-pneumatic spring in parallel is designed to realize the lifting function, aiming at the problem of the poor ride comfort of the original vehicle. According to the vehicle parameters and suspension requirements, the rubber springs, whose mathematical model is difficult to establish, is selected firstly, and then the mathematical model of the rubber spring is obtained by fitting its experimental data. Next, the parameters of the hydro-pneumatic springs are initially selected. In MATLAB/SIMULINK, the half-car mathematical model of the vehicle is established, and the parameters of hydro-pneumatic springs was optimized by Genetic algorithm (GA). The result of simulations suggest that proposed method is promising for improving the ride comfort of the vehicle on the basis of satisfying the vehicle lifting function.

Zhiwei Zhang, Tongli Lu, Hua Jiang

### Effect of Tyre Pressure on Ride Comfort from an Integrated Chassis Control Perspective

Ride comfort is one of the aspects that may be improved through integrated chassis control. The effect of tyre pressure on the ride comfort of a SUV with low profile tyres is investigated to quantify its contribution as a system within integrated chassis control. A SUV was subjected to two road profiles on a 4-poster test rig. Ride comfort was objectively evaluated for ten repeat runs at three inflation pressures over two roads. The largest relative percentage improvement in ride comfort of 1.5% was seen between the lowest and highest pressures over the rougher road. This improvement is below the relative difference threshold for ride comfort. Furthermore, no significant difference between the median combined point ride values across the three tyre pressures on the two roads were found. Therefore, a perceptible change in ride comfort may not result from inflation pressure alone. However, in combination with other system changes within integrated chassis control, perceptible change may be achieved.

Cor-Jacques Kat, Pieter Schalk Els

### Sensitivity Analysis of Vehicle Handling and Ride Comfort with Respect to Roll Centers Height

The role of the roll center on vehicle dynamics has been the subject of several works in the literature. However, the majority of them has been based on low-fidelity models and on roll center’s effect on the vehicle roll dynamics, because of the importance of predicting accurately the time of rollover. In this paper, we aim to conduct an sensitivity analysis of the impact of varying roll center height on vehicle’s performance, while varying also other K&C characteristics. More specifically, the roll centers are varied at the same time with the anti-roll bars. In this respect, we use a vehicle model of 14DOFs, which includes non-equal jacking forces and is validated with CarMaker Software. The vehicle model is excited at the same time with appropriate steer inputs and road profiles in order to focus on handling and ride comfort. The sensitivity analysis provides a fundamental understanding of the exchange between the K&C characteristics to vehicle performance metrics, which represent the transient and steady state handling and the passenger’s ride comfort. ...

Georgios Papaioannou, Christian Gauci, Efstathios Velenis, Dimitrios Koulocheris

### Influence of Driver Muscle Tension on His Ride Comfort

Vibration and ride comfort is usually evaluated for vehicle passengers in passive state, in particular the human passenger is considered as a passive mechanical system. However, several experiments and experience with them indicated that the human passenger is an active participant of the dynamic process of comfort creation. This paper builds on these results with the novelty that the ultimate consequence of human muscle tension change is the improvement of ride comfort impression. Multibody model of human passenger body was developed and calibrated based on carried out experiments. The activity of passenger body is modeled as its muscle tension. The positive influence of muscle tension level on vibration and ride comfort is evaluated. It corresponds to the measured activities of human passenger bodies during carried out experiments.

Michael Valasek

### A Novel Switchable Suspension Inspired by Duffing Oscillator

Inspired by the duffing oscillator, a novel suspension is proposed, which could realize the softening/hardening spring, and could switch between passive, semi-active and active control mode of suspension solely through control of the electric motor. The mathematical model of quarter vehicle suspension is given to express the suspension at different modes. Then the equivalent linear approximate model (ELAM) [1] is introduced and the switching between the semi-active suspension and passive suspension is realized through the idea from the model. The ELAM model is validated numerically by the comparison of simulation between ELAM and sky-hook control model. To further validate the proposed switching method, a scaled suspension test rig is developed, the idea of the switchable suspension is implemented by the control of the servo motor equipped in the rig, the switching experiment result agrees well with the simulation.

Qiang Chen, Yong Zhang, Jiaqi Zhao, Zhanshuai Song, Ye Zhuang

### Comfort Improvement of an Adaptive Vehicle Suspension via Pointwise-Constrained Optimal Control

Eduardo Palomares, Miguel Felix, Angel L. Morales, Antonio J. Nieto, Jose M. Chicharro, Publio Pintado

### Model-Based Investigation of the Influence of Wheel Suspension Characteristics on Tire Wear

The amount of a vehicle’s tire wear depends on several factors, such as material properties of the tire, environmental factors, driving behavior and especially the interaction between wheel suspension and wheel. While driving, the wheel has a defined setting to the road, which is given by the kinematic and compliance characteristics of the wheel suspension. This study takes an isolated look at wheel suspension characteristics with respect to tire wear. A flexible multibody simulation model of a multi-link rear axle is built up in MSC Adams/View to analyze the influence of wheel suspension parameters on the tire footprint. This model consists of a combination of flexible and rigid bodies and nonlinear connection elements like rubber metal bushings. The simulation model is enhanced by two FTire tire models, which is a widely used commercial physically based, 3D nonlinear flexible structure tire model. It was chosen because it has a separate tire tread model to compute the contact pressure and friction force distribution in the tire contact patch. To apply road excitation, a two-dimensional road model with a stochastic road profile is used. Various wheel suspension kinematics were set up and their influence on tire wear examined.

Jan Schütte, Walter Sextro

### Model-Based Estimation of Damper Excitations and Velocities Due to Road Surface Irregularities with Focus on Ride Comfort

In this paper a model-based method for estimating the damper excitations and velocity amplitudes by means of synthetic road irregularities are shown. They are based on a stationary white noise process with power density 1. With two 1st order filters it is possible to generate realistic synthetic road irregularities which are limited to an adequate magnitude level for both, small frequencies and higher frequencies.To estimate the damper excitations and velocity amplitudes two methods are presented. The first method is based on the standard deviation method, which takes the appearance probability of 99.7% of simulated damper excitations and velocity amplitudes into account. The main disadvantage of these method, no information of the amount of amplitudes can be extracted, can be overcome with the second method. It is based on the relative frequency of the damper excitations and velocity amplitudes.Three different synthetic roads based on the road types highway, main road and urban road, with an equivalent road surface quality index are generated. With a quarter vehicle model, which consists of a nonlinear so called VDA-characteristic simulations are presented to estimate the damper excitations and velocity amplitudes by means of the two described methods.

David Benz, Peter E. Pfeffer

### Capturing Brake Groan Using Multibody Quarter Car Model

By now, the brake noises have been classified by using a variety of different words like judder, groan, moan, squeal, squeak, hum, etc. For simplicity, based on their frequency ranges, they can be grouped into 3 categories: judder (around 10 Hz), groan (50–150 Hz) and squeal (>1k Hz). Brake creep groan noise is generated when a brake pedal is slowly released especially in an automatic transmission car which was initially stationary. The primary reason is a stick-slip behaviour between the pads and the disc. Stick occurs when the pad and the disc move together with no relative movement between them, while Slip occurs when the brake force decreases and the wheel torque begins to catch up with the brake torque and eventually a wind up of the brake assembly causes a momentarily slip. Without further release of the brake pressure, the stick happens again and the cycle repeats. The noise and vibration due to this sustained stick-slip is called brake groan.A Multibody quarter car model was developed using a Multibody Simulations (MBS) software with data from Volvo Cars to simulate the Brake Groan phenomenon. The model contained a detailed brakes system and the quarter car front suspension system with all the suspension components modelled flexible (deformable). The Brakes components on the other hand, e.g. Brake pads, disc, callipers, piston etc. were modelled as rigid bodies. The aim of this work was to capture the stick-slip between the disc and the pads as the brakes are slowly released and the vehicle is accelerated gradually.

Avijit Chauhan, Patrick Sabiniarz

### Identification of Kinematic Points Based on KnC Measurements from the Suspension Motion Simulator

A systematic method to identify the kinematic point positions (x-, y- and z-values) of a rear axle has been developed with help of Kinematics and Compliance (KnC) measurements from the Suspension Motion Simulator (SMS) at TU Dresden. The kinematic points were at first measured with a ROMER arm, which is a coordinate measurement machine (CMM). The KnC simulation results of a MBS (Multibody System) model in ADAMS/Car based on CMM data were verified by KnC measurements from the SMS test rig. To reduce the calculation time, the total identification process was defined in two steps, rough and fine identification. In the first step of rough identification, the boundary conditions were constant lengths of links or constant distances between two kinematic points as to find possible spatial positions of kinematic points in a restricted range. For fine identification, the objective function considered also the KnC characteristic curve error between MBS simulations and test rig measurements, which was realized by a simulation exchange between ADAMS/Car and MATLAB. The errors between identified positions of kinematic points and CMM data were in an acceptable range, which has validated the developed identification method.

Chao Liu, Yi Zhang, Clemens Deubel, Felix Kocksch, Jan Kubenz, Günther Prokop

### Posture Control of All Terrain Mobile Robot with Vibration Isolation System

Robot will inevitably change its body posture (position and attitude) when crossing obstacles on extreme roads, at the same time, the road will have a huge impact on the body. In order to reduce road impact and body vibration, a wheel-legged all terrain mobile robot (WLATMR, the same below) with a new series slow active suspension structure was designed. The vibration isolation performance of the suspension was verified by the 11DOF dynamics model. In order to realize the closed-loop control of the posture, the kinematics and dynamics model of the robot considering the deformation of the suspension was built, and the co-simulation based on SIMULINK and ADAMS was carried out, the simulation results show that whether the suspension deformation is considered or not has little effect on the final control result, but the requirements on the working speed and working range of the actuator can be effectively reduced by considering the suspension deformation. This can effectively reduce the system steady-state time, improve the system response rate, and reduce the use cost in specific practical applications.

Fangwu Ma, Liwei Ni, Lulu Wei, Jiahong Nie, Liang Wu, Weiwei Jia

### Comparative Performance Analysis of Active and Semi-active Suspensions with Road Preview Control

The paper presents a comparative performance analysis of passive, active and semi-active suspensions with various optimal control system settings. The active suspension is controlled by a linear quadratic regulator (LQR) in combination with road preview control, while the semi-active suspension is controlled by a clipped-optimal LQR approach. The LQR cost function includes three conflicting criteria related to ride comfort, vehicle handling and suspension stroke limits. The trade-off among these three criteria is assessed by using covariance analysis, i.e. by comparing standard deviations of the criteria-reflected system outputs with respect to stochastic road profile input. Further comparative analyses are based on frequency responses of linear quarter-car model and time responses of nonlinear full-car suspension model. The analysis results show that for some not-too-soft settings, semi-active suspensions with road preview control can outperform active suspensions without road preview, while the best overall performance is achieved by using fully active suspension with road preview control. Time responses of a full-car model, obtained in an advanced simulation environment, demonstrate that controllers based on simple, quarter-car model can be successfully applied to nonlinear, full-car model for improving ride comfort and vehicle handling.

Ivan Cvok, Joško Deur, H. Eric Tseng, Davor Hrovat

### A New Generic Model for Adaptive Shock Absorbers

Adaptive shock absorbers improve the ride quality by changing the damping characteristic depending on road excitation. An adjustable bypass valve allows to switch between different force characteristics. This paper introduces a new generic damper model which uses a modular damping function (MDF) to adapt the resulting force output through position-, stroke- and frequency-dependent adjustments. The piston motion is used to determine the shock absorber’s basic force and the state-dependent force difference, which results from the adjustable bypass. In contrast to established modeling approaches that are used for digital performance predictions in the early stage of the development process, MDF includes both the maximum and the minimum force characteristic, thus allowing the implementation of adaptive shock absorbers. Few additional parameters are required to specify both hysteresis and the adjustable bypass effect. In later stages, measurement data can be used to fit the model quality to the increasing maturity level of the described shock absorber.

Niklas Kunz, Steffen Müller

### Analysis of Active Suspension Performance Improvement Based on Introducing Front/Rear LQ Control Coupling

The paper investigates the potential of improving vehicle ride comfort based on introducing control design coupling between front- and rear-axle active suspensions. The considered linear quadratic regulator (LQR) cost function includes conflicting criteria related to ride comfort, vehicle handling, and suspension stroke. A covariance analysis related to standard deviations of cost function criteria with respect to stochastic road profile input is carried out for half-car models with two and four degrees of freedom. The presented results show that the control-design coupling can considerably improve the ride comfort in terms of reduced sprung mass pitch or heave acceleration with a relatively small sacrifice of vehicle handling and suspension stroke. The performance improvement is explained by the fact that the rear suspension controller uses state information from the front axle (and vice versa), which may be considered as a kind of preview action.

Ivan Cvok, Joško Deur, H. Eric Tseng, Davor Hrovat

### Development of a Cab Suspension for a 4 × 2 Semi-truck

In this paper, within the scope of a competitive product development process in accordance with customer demands and ISO comfort standards, development of the cab suspension system for a 4 × 2 semi-truck is presented. In the first part of the study, benchmark vehicles were selected due to the customer demands. Cab comfort evaluation tests were applied to these vehicles. By this way proper ranges of the design targets were determined. Subsequently a first level (or mule) prototype of the vehicle was produced. The acceleration and displacement data are collected from the cab and the chassis of the first level prototype. By using nCode Glyphworks commercial software, these data were refined to create the input functions for the Adams/Car™-based multibody dynamics (MBD) cab suspension model. Virtual acceleration and displacement data were also collected via the MBD model and correlated with the data obtained from the first level prototype. After the model verification, a design of experiments (DOE)-based optimization study was performed via Adams®/Insight commercial software to achieve required characteristic curves which satisfy design targets. With the use of new suspension system features, second level prototype was also produced and validation tests are performed. After verification of suspension characteristic, dynamic response of the cab was evaluated with respect to ISO 2361 comfort criteria. By using the absorbed suspension energy method, comfortable working durations for driver were determined according to ISO 8608 road profiles.

Uğur Deryal, Ezgi Zeynep Sarıkaya, Mehmet Murat Topaç

### A Novel Approach for Parametrization of Suspension Kinematics

In the automotive industry, simulations are needed to analyse the dynamics of vehicles and also of its main components and subsystems, e.g. tires, brakes and suspension systems. These simulations are required for an early-stage development and in consequence, they must deliver realistic results. Suspension systems plays a key role in comfort and safety of road vehicles. They usually consist of rigid links and force elements that are arranged with a specific topology. In addition, some of their functionalities are to carry the weight of the car and the passengers, and maintain a correct wheel alignment. In simulations involving suspension systems, lookup-tables are frequently used. They are obtained from a Kinematic and Compliance (KnC) test and then standardized for a specific vehicle simulation software. Nonetheless, lookup-tables require a reasonable number of characteristic points. Additionally, derivatives, interpolation, and extrapolation are not necessarily smooth. This produces results that depend on the interpolation technique and may be inaccurate. In this paper, a novel method called “design kinematics” is proposed. This method can describe the kinematic properties of almost any type of suspension systems. Comparisons with an analytic calculation and a KnC measurement shown that the design kinematics is able to represent the kinematic and compliance properties of suspension systems extremely well and very efficiently.

Georg Rill, Abel Arrieta Castro

### Influence of the Speed-Dependent Tire-Road Friction on the Car Drifting Dynamics

The Force and Moment properties of the tire under large slip maneuvers have speed-dependent feature. The tire force model considering such feature is introduced to the car drifting model. The influence of it to the drifting dynamics is analyzed in detail from the aspects of drift equilibria, phase portrait and control.The analysis of drift equilibria shows that the front lateral force has a large level of unsaturation as counter-steer angle increases due to the decrease of the rear friction coefficient. The analysis of phase portrait shows that the steering characteristics of system, the number of equilibria and the unstable area in the phase plane vary significantly at larger steer angles. The simulation results show that the system considering such feature is easy to enter the drift state and has relatively better anti-interference ability especially in the process of exiting drift.

Ye Zhuang, Zhanshuai Song, Qiang Chen, Jiaqi Zhao, Konghui Guo

### Full-Field Strain Measurement of the Contact Patch via the Inside Tyre Surface

The tyre is the only interface between the vehicle and the road and has thus been the subject of many research studies. An important aspect of tyre research is the development of a smart tyre which can indirectly determine parameters representing the state of the vehicle such as the tyre forces and side-slip angle. In this paper Digital Image Correlation (DIC) is used on the inside surface of the tyre to produce full-field strain measurements of the inside surface of a tyre in contact with the road. The study aims to measure and understand the full-field strain measurements caused by various loading cases with the aim of smart tyre development.

Megan S. Pegram, Theunis R. Botha, P. Schalk Els

### Nonlinear Modeling of Truck-Semitrailer Lateral Dynamics Including Experimental Validation of Lateral Tire Forces

Advanced Driver Assistance Systems for commercial vehicles are mainly implemented in the truck and in most cases only consider measurements or estimates about the truck’s states. However, the trailer accounts for up to 80% of the total vehicle mass and therefore significantly influences the vehicle’s dynamics. For analysis of the trailer’s dynamic behavior and for potential implementation in model-based observer or control design, in this paper a nonlinear single track model of lateral dynamics of a typical truck-semitrailer combination is developed. The model thoroughly considers the lateral tire forces which, in contrast to most other publications, are validated on measurements from a real test vehicle. The results show an adequate simulation of the measured vehicle’s states. The implementation of the model on an automotive rapid prototyping ECU shows it’s online capability.

Zygimantas Ziaukas, Jan-Philipp Kobler, Alexander Busch, Mark Wielitzka, Tobias Ortmaier

### Experimental Investigation and Semi-physical Modelling of the Influence of Rotational Speed on the Vertical Tyre Stiffness and Tyre Radii

Development and validation of vehicle dynamics controls and automated driving functions require real-time capable tyre models that are able to consider main influencing parameters at the tested operation condition accurately. In the presented study, experimental investigations with two types of tyres were conducted to quantify the effect of the tyre rotation on the vertical tyre stiffness, the unloaded, static and effective tyre radius. Based on the semi-physical handling tyre model TMeasy, an enhanced modelling approach is presented which is able to consider the rotational speed dependent tyre behaviour in an effective semi-physical and numerically efficient manner. The measurement results of the tyre testing series are analysed and the effects of the tyre rotation are identified. The tested tyres show a nearly linear rotational speed induced increase of the vertical stiffness and a non-linear increase of the unloaded radius. Finally, the performance of the presented enhanced semi-physical model for the vertical tyre force transmission and tyre radii is validated. The results are discussed and an outlook regarding further investigations is given.

Martin Schabauer, Andreas Hackl, Wolfgang Hirschberg, Cornelia Lex

### Predicting Tyre Behaviour on Different Road Surfaces

Most tyre models used in vehicle dynamics simulations are parameterised with data obtained on a flat-track test rig, where the tyre is commonly driven on sandpaper. The resultant models are typically very accurate at low to medium slip conditions. At high slip, the prediction of forces and moments of a tyre rolling on surfaces other than sandpaper is less reliable as this condition is dominated by the rubber-road friction characteristics. To extend the validity of tyre models derived from sandpaper surface measurements to road surfaces, this paper explores the use of frictional behaviour of tread rubber obtained with a purpose-built rubber friction measurement system. Since rubber friction depends on many variables, tests have been carried out under controlled conditions in order to obtain accurate and repeatable data. Friction measurements were performed on sandpaper and incorporated into a brush-type tyre model to recreate the flat-track measurements of the full tyre. Preliminary results indicate the benefits and potential of detailed knowledge on the frictional behaviour for accurately modelling tyre forces and moments.

Alex O’Neill, Patrick Gruber, John F. Watts, Jan Prins

### A Grey Box Model Approach for the Prediction of Tire Energy Loss

The maintenance costs of vehicles, and particularly commercial vehicles, are influenced by rolling resistance and tread wear of tires. In this context, the tire label is established in Europe for indicating the energy efficiency of a tire, although the respective test procedures do not reflect realistic application scenarios in daily use. Therefore, we propose a grey box model approach for predicting rolling resistance and tread wear of tires, i.e., tire energy losses, as a function of route, vehicle, driver and traffic parameters by means of physical models for the vehicle and tire dynamics in combination with machine learning techniques. This enables the prediction of tire energy loss for different customer groups in arbitrary regions around the world under realistic conditions.

Michael Burger, Stefan Steidel