11th International Munich Chassis Symposium 2020

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All great Empires in history were looking for solutions to achieve expansion. To give you some examples: the Romans built roads, the Ottomans used light-weight chain armor and the Mongolians used a dynamic cavalry.

Toyota New Global Architeture (TNGA) is the latest company-wide program to design “ever better cars“ by enhancing the vehicle structure and the development process.

The rapid launch of automated vehicles on global markets requires uniform global regulations. To date, however, the regulations have varied greatly from region to region, and the development of uniform, internationally binding guidelines has only just begun. The first UNECE regulation for an automated driving system at SAE level 3 is expected in 2020—a pioneering achievement and a template for further internationally binding regulations.

The requirements imposed on the brake system of a Battery Electric Vehicle (BEV); above all the requirements imposed on the recuperative capacity of the system for maximum energy recovery, are constantly increasing. Energy recovery, not just in the usual form as a major contribution to energy efficiency and increasing the range in day-to-day operation, but rather in this case – which is typical of Porsche, using the first electric Porsche sports car, the Taycan as the example – this also extends to the limits of driving dynamics, under extremely high lateral acceleration and during ABS control. Thus recuperation is a very large and important contributor to thermal offload of the wheel brake on the one hand, but also towards increasing the drivable number of laps until the next charging procedure, on the other hand. The demand is to allow the interactions of the various deceleration actuators (friction brake and electric motor) required in this regard, to run in the best manner possible, unnoticed by the driver. This applies equally in the context of "requirements for racing circuit driving", and to the objective of a brake pedal feel that is as natural as possible, such as retention of the haptic ABS pressure point relative to pedal force and pedal travel, as well as to the challenge of minimal influence on front-axle to rear-axle braking force distribution, so as not to disadvantageously influence the driving dynamics that are customary and typical for Porsche. In the article below – after a brief description of drive system and chassis – the recuperative brake system for combined braking of the Porsche Taycan will be presented in detail. This includes all participating components, from the pedal system to the brake actuation system and the recuperation strategy and on through to the wheel brake. In this regard a technical description of the lightweight design concepts and technologies that are used will be provided.

The Lincoln Corsair is a compact premium crossover vehicle on Ford's global C (compact class) platform, replacing the Lincoln MKC. The prime focus of the research and development workstreams of the integral bushing rear suspension architecture for the new Lincoln Corsair was to significantly improve the performance in terms of impact harshness as well as noise, vibration and harshness (NVH) behavior compared to the Lincoln MKC featuring a control blade rear suspension architecture. The new integral bushing rear suspension architecture is an evolution of the integral link rear suspension architecture developed for Ford's global CD (midsize class) platform. Compared to the integral link rear suspension architecture the integral bushing rear suspension architecture is significantly lighter and the cost structure could be improved without compromising the performance level of the integral link rear suspension architecture. With regards to the interior noise attribute the performance level could be significantly improved. The integral bushing rear suspension architecture development included benchmarking activities, definition of attributes and targets, suspension concept design as well as system evaluation and selection. The concept development work was conducted with special attention to key requirements implied by a compact premium crossover product like the Lincoln Corsair as well as design constraints introduced by the platform and the sister product Ford Kuga deploying a control blade rear suspension architecture. This paper focuses on the design aspects and the fundamental layout principles of the integral bushing rear suspension architecture by presenting the journey starting from the integral bushing rear suspension prototype development towards the final series production design of the premium rear suspension architecture of the new Lincoln Corsair.

One of the most commonly used advanced driver assistance system is adaptive cruise control. Although many cars are equipped with such a driver assistance system, the development is still based on subjective evaluation indices. The design of adaptive cruise control could be more powerful and reach more customer acceptance when a design process with specific values to ensure good driving characteristics is used. Such an objective based process is still state of the art of classic chassis development, but typically not used for advanced driver assistance systems.To achieve this, use case-based scenarios are deduced from properties. A scenario simulation is used to generate information about important KPIs and collect data to develop an automated data analysis tool. To correlate subjective KPIs with objective measurement values an inertial navigation system in each car with differential GPS (RTK) and a wireless connection between both cars is installed. With the aid of this measurement system differential speed, acceleration and distances are calculated in a precise way. It also contains a fully controllable target vehicle in longitudinal and lateral direction to generate manoeuvres with high reproducibility. An analysis algorithm automatically calculates KPIs and displays important diagrams after each test run. This leads to a complete system analysis test in two days for each car. The comparison of target KPIs and subjective evaluation criteria shows whether the system reached its goals or if improvements are necessary. For this purpose the project partners Porsche, University of Applied Sciences Kempten and MdynamiX have joined their forces.

When the suspension deforms, damping force is generated as the piston of the shock absorber moves, but a time difference occurs before the large hydraulic damping force rises. At the same time the frictional force in the shock absorber is playing an important role in generating effective damping force against deformation of the suspension, the generated force itself is small but its response is high. The frictional force in the shock absorber occurs in reciprocating motion in various speed ranges from amplitude of less than one millimeter to larger amplitudes, its behavior changes dynamically and is non-linear. Recent studies have revealed that controlling the friction is more important than reducing it for improvement of the performance. Because of this we have investigated the dynamic friction characteristics of shock absorber oil and sliding parts, by the means of an own developed device that can measure the speed dependence of friction force in reciprocating motion with high accuracy.The result of our analysis shows that friction dissipates energy at a speed level of 0,002m/s where hydraulic dissipation is not working yet. By knowing this phenomenon, we have developed different kind of oil types in order to generate various dynamic friction characteristics.The influence of our developed oil types on the ride and handling performance was tested and analyzed in different vehicles. Subjective assessments and objective measurement show the vehicle performance improvement, which can be generated by using more advanced oil types.

The two major challenges in chassis development - both aiming at im-proved efficiency - the automotive industry is facing are: reducing development cost – e.g. less prototype vehicles, less physical testing increasing value for customers – e.g. more variants, higher complexity In this challenge, virtual methods are efficiently serving the development process with data and key performance indicators in order to understand effects on an objective level. Nevertheless, shaping the overall vehicle dynamics characteristics to a brand-specific DNA and providing this DNA throughout the whole vehicle lineup often requires the need to enhance the understanding of objective knowledge by subjective measures.Given multiple examples of new installations in the recent years, the rise of driving simulator technology in the industry is more than obvious. However, driving simulators itself are tools – and like other simulation tools – featured with several limits and boundary conditions in their application. As in physical testing, test procedures need to be designed in a way that specific performances of the vehicle can be evaluated. The same holds for the usage of driving simulators, but unlike in physical testing several additional points need to be considered. Therefore, the paper describes as a first step a driving simulator-oriented test and maneuver design for efficient vehicle evaluation and lists advantages which are only present in virtual environments.Whereas many publications are developing methods which focus on studies with many participants (“normal driver”), Hyundai has developed a methodology aiming at the standard vehicle dynamics process which is executed with the help of professional subjective test drivers. The paper describes how the virtual tests are prepared and how test drivers are smoothly integrated in the process.The application of this process is shown on the example of vehicle variant development, which is in the real world only possible for some selected variants of a given vehicle. Based on the shown process, a driving simulator environment enables the subjective evaluation and consistency check for different weight, trim line or tire configurations for a wider range of variants, which finally improve the quality of the brand specific vehicle dynamics DNA.

Small and narrow electric vehicles can represent a solution module for the impending traffic infrastructure and environmental problems in city centres. Along with this vehicle concept, either a deterioration in driving comfort due to a very hard chassis tuning has to be accepted or an active tilting system has to be integrated into the concept. On the one hand, this active tilting control requires an additional development effort for a robust and safe control system. On the other hand, however, it also offers new possibilities for a new, attractive driving experience. With this newly gained degree of freedom in the tilt motion it is possible e.g. to vary the perceived lateral acceleration in a wide range.

Dynamic wireless power transfer (WPT) can solve the short-cruising range problem of electric vehicles. Energy transfer is one of the major problems of dynamic WPTs. Prevention of the entry of foreign objects physically be-tween the transmitting and receiving coils is the best way to increase energy transfer for dynamic WPT. This research proposes a novel WPT system, named in-wheel coil, which can transfer through the tire and the wheel. The suitable materials of tires and wheels for in-wheel coil is also evaluated and proposed. Metal belt of tire is not efficient and rises temperature of tire. Instead of metal belt, fiber belt which has no conductivity is proposed and proved that it does not has any influence for WPT system at 85 kHz. This research also revealed that steel and aluminum and cross carbon fiber reinforced plastic (CFRP) has critical influence for WPT performance and uni-directional (UD) CFRP has little influence for WPT performance at 85 kHz. Combination of the wheel made of UD CFRP wheel and the tire whose belt is fiber belt is the best way to improve WPT efficiency.

Car drivers constantly demand a higher level of road safety, whether in terms of road infrastructure, vehicle and/or tires. They also ask for more information about the level of safety they have when driving. To meet this need, the tire label – which has existed since 2012 in Europe – gives them information about the tire’s wet grip performance as well as its noise and fuel consumption impact. However, this information is worth for a new tire, and it is known that wet grip performance is one of the few tire performances that reduces as a tire wears.In this study, the analysis of wet grip mechanisms is conducted through an innovative method, which is based on a detailed analysis of the regulatory wet braking test. This method enables a decomposition of the respective weighting of each mechanism, both for new and worn tires. It has been observed that there are two main mechanisms of wet grip: rubber friction and hydroplaning. While rubber friction enables the generation of a braking or steering force by the tire through the rubber-road contact, hydroplaning reduces its efficiency by diminishing the contact surface area.This study demonstrates that the relative importance of the involved mechanisms depends on the tire state: while rubber grip is the predominant mechanism of a new tire, both hydroplaning and rubber friction are important for worn tires. This decomposition study also shows that the reduction of wet grip from a new to a worn tire is tire dependent as decrease may be linked to rubber friction, or to a reduced hydroplaning capability.

This paper describes the development of a methodology for representing tire behaviour during extreme vehicle handling simulations. Firstly, the tire operating conditions during a “fishhook” maneuver are analyzed. During this maneuver the tires experience significantly higher vertical loads, sideslip rates and camber angles than during nominal passenger car tire testing conditions. As these tire measurements are used for model parameterization, only testing the tire under nominal conditions is insufficient for accurately modeling the tire performance during extreme handling maneuvers. Three different tire testing protocols are used to parameterize the MF-Tyre/MF-Swift model. The three generated parameter sets are used in vehicle dynamic simulations of which the results are compared to vehicle measurements. The effect of the sideslip angle rate (steering rate) on the tire behaviour is found to be most influential. The effect of the steering rate is eminent when tire thermal effects are considered. Results using an extended version of MF-Tyre/MF-Swift that takes into account thermal effects show that the steering rate directly influences the peak friction that the tire reaches. It is concluded that if a tire model is used for extreme handling maneuvers, the tire operating conditions during the vehicle maneuver should be considered in the tire parameterization test protocol to increase accuracy.

The Cornering feedback from the vehicle is important information to control the path and the yaw stability, especially in limit handling situation. To improve this cornering feedback, in-depth analysis of vehicle cornering motion should be advanced. But, due to the transient characteristics of vehicle corner-ing motion, effective analysis of cornering feedback has remained as a very challenging task. In this article, 1) important properties of transient cornering motion have been studied and 2) yaw de-composition based new transient motion analysis method is proposed. This new analysis method enables separate analysis of vehicle yaw motions by its sources, from path following and from yaw spinning, which is the key element in objectification of cornering feedback. Additionally, an in-depth analysis of yaw center migration and its effect on driver feeling has been investigated. Based on these analysis methods, subjective vs. objective correlation study has been conducted and major cornering feedbacks includes carving feel have been objectively analyzed and quantified. In this article, side slip motion compliance & resistance in path following also has been investigated to analyze vehicle turn-in response. Additionally, based on this newly proposed transient motion analysis, its application idea includes active control of vehicle motion in various situations is also proposed.

Simulation has established itself as an essential tool in the virtual chassis development process to reduce both development time and costs, especially for suspension design. In the literature, a variety of characteristic values are proposed to characterize and benchmark suspension systems. These characteristic values play a vital role for the design of suspension kinematics and compliance. This paper presents an approach for the analysis and characterization of suspension systems within multi-body simulation, which makes use of the suspension system’s compliance matrix. A universal methodology for the calculation of the existing characteristic values, which characterize both steering feedback and wheel guidance, by means of the compliance matrix is outlined as well. The results demonstrate the application of the proposed approach to several exemplary use cases within suspension design. The newly gained insights with this method can be used to further enhance suspension design by improving the characterization and benchmarking of suspension systems.

The challenges of modern vehicle software development are mainly due to the increasing complexity and growing number of functions that lead to high costs and time expenditure for software tests. To meet these challenges, in this paper a method is presented that assigns software test cases to the test in-stances Hardware-in-the-loop simulation and vehicle. The main aim is an efficient and effective use of both instances. As vehicle prototypes are tremendously expensive, the focus is on the reduction of time for vehicle tests. A four-stage method assigns individual test situations to the correct instance by means of a utility analysis. For this purpose, the identification of technical aspects of testing is the first step. Afterwards, filtering and weighting of these aspects is necessary for specific use cases. Subsequently, the identification of test situations is the next step before assigning them to the correct test instance with the utility analysis. To prove the validity of the developed method the paper contains an application ex-ample, which evaluates 151 test manoeuvres with the method. The result is a drastic reduction of the time required for vehicle tests.

In the era of future mobility ahead of us, the importance of ride comfort performance will be highlighted further by the increasing demand from customers for comfort to lead daily lives such as reading and resting in cars while on the move. If it is possible to predict the ride comfort performance of the vehicle using only the system without the vehicle tests, ride comfort performance development at the early stage is very advantageous through target cascading and system level performance enhancement. In this paper, newly installed test rigs (suspension module test rig, dynamic comfort roadway, chassis dyno) were used to identify the effect of the vibration characteristics of suspension on the ride comfort performance, and the system’s vibration characteristics and ride tests were carried out, and correlation between the ride comfort performance and system vibration characteristics was analyzed. Ride comfort performance enhancement process at the system level based on analysis of system vibration characteristics was proposed. The target of vibration characteristics of the suspension system to improve ride comfort performance and a process of component design was proposed.

With battery electric vehicles (BEV), due to the absence of the combustion process, the rolling noise comes even more into play. The BEV technology also leads to different concepts of how to mount the electric engine in the car. Commonly, also applied with the Audi e-tron, the rear engine is mounted on a subframe, which again is connected to the body structure. This concept leads to a better insulation in the high frequency range, yet it bears some problems in designing the mounts for ride comfort (up to 20Hz) or body boom (up to 70Hz).Commonly engine mounts are laid-out based on driving dynamics and driving comfort (up to 20Hz). The presentation proposes a new method to find an optimal mount design (concerning the stiffness) in order to reduce the dynamic chassis forces which are transferred to the body (20Hz – 70Hz). This directly comes along with a reduction of the sound pressure level for the ‘body boom’ phenomena.We use multibody simulation along with a sophisticated tire model in the time domain in order to capture the correct excitation and structural dynamics behavior. Along with an optimizer, we rely on design of experiments (DOE) in order to find the optimal setup for engine-mount stiffness and therefore directly reduce the sound pressure level.

One challenge for the Ford chassis research team in the recent past was to investigate lightweight solutions for the upcoming Transit platform, for the end customer benefits of higher payload, reduced emission and better fuel consumption. As first application within the platform, the Camper /Motorhome was chosen. One of the promising items which was looked at were the rear longitudinal leaf springs. Replacing the standard steel springs with equivalent parts in composite material, generated a weight saving of about fifty percent, or about fifteen kilograms per vehicle. The spring had to be entirely redesigned, to obtain best in class performance, considering the new material properties and limitations. The project covered all the necessary steps, from the first research state to series implementation. Three important aspects which are discussed here are the design, the testing and finally the manufacturing process.

Batteries and drive train components in future concepts for electrified vehicles require a significant amount of space. Because of their additional cost and weight penalty it is necessary for the chassis components to claim as little space as possible and contribute to the overall cost and weight savings of the whole vehicle.To achieve these goals a suspension concept with a reduced number of parts is introduced. By functional integration only a single part made of fiber-reinforced plastic is needed to support the wheel load and provide wheel guidance. This spring/control arm and the shock absorber are the sole means to control wheel travel instead of several control arms and bushings. The required space for the suspension system is minimized without affecting vehicle dynamics and ride comfort.Test rig and misuse testing results of a prototype front axle are discussed, and simulation and road test results of a rear axle concept in a prototype vehicle are presented. Finally, possibilities of further cost and weight reduction are suggested.

Vehicle subframes are architecturally significant and highly integrated structural components of the chassis. They have a major influence on functional chains at the overall vehicle level and are characterized by a large number of interfaces. The conflicting objectives of increased component complexity versus cross-platform design modularization require new methods and concepts aimed at more efficient development and evaluation of subframe designs across multiple stages of product maturity. This paper presents a method to cope with the complexity and uncertainties in the early development phase of structural components and to carry out a multidisciplinary as well as functional and geometric design at the detail level. First, the complexity is reduced by using automatically generated knowledge-based CAD models and corresponding FEM models, which can cover different degrees of maturity in the design process within the early development phase. Secondly, automated processes are used for all relevant requirement disciplines in order to generate data in a fast and efficient manner to train neural networks, which can map the complex and often non-linear relationships between the design parameters and the characteristic values. Thirdly, epistemic uncertainties are considered with the help of the solution space engineering framework, in which maximized solution intervals for the individual design parameters are determined, to increase robustness and flexibility for the following design process. The effectiveness of the approach is demonstrated using a rear subframe as an example problem.

Customer demands and governmental emission regulations require new lightweight and electro mobility concepts in the commercial vehicle market.The necessary design changes have a significant impact on both, the structural strength and the dynamics of the chassis and the body. The evaluation of the chassis components and the body in terms of structural dynamics and operational strength at an early stage of the development process plays an important role for a time and cost effective validation process. Using simulation methods, the virtual vehicle can be analyzed long before a physical prototype is available which allows faster structural design optimizations. The virtual rough road testing combines multiple simulation disciplines and takes the full vehicle dynamics into account. Starting with the full finite element model for strength analysis, a superelement is generated using component mode synthesis. This superelement is incorporated in multibody rough road simulation to consider the elastic body deformations. The multiaxial loading history and the material data of all components are subsequently used in the operational strength analysis to determine the resulting hotspot regions and to derive structural optimizations. For a reliable operational strength forecast, an accurate prediction of the input load history is important. Therefore, the modelling of the front axle used in city busses is investigated. A flexible model of the axle is used for a stress comparison with real world test track data. In a further step, the necessity of the flexible body is evaluated with a comparison of the resulting bushing forces attached to the frame structure.

This article proposes a method to independently control the gain and the phase characteristics of the vehicle frequency response. In steer-by-wire vehicle, it is possible to design the characteristics of vehicle dynamics like the yaw response. However, the gain and phase of the frequency response of linear systems are coupled which limits the tunability. Therefore, when one characteristic is changed, the other is changed too. To deal with this issue, we propose a control method for enabling independent gain and phase characteristics of the yaw rate dynamics on a steer-by-wire system. The construction of a NARX model with a neural network enables generating the nonlinear characteristics. Furthermore, a LQR controller calculates the front wheel angle to track the nonlinear target yaw rate. The proposed control is validated on a steer-by-wire equipped vehicle. The control strategy is described and experimental data demonstrate the improvement on maneuverability and stability.

Steer-by-Wire (SbW) is a newly emerging technology entering the market in the next decade. The additional degree of freedom in the steering system leads to not only new and enhanced features, but also opens up numerous questions how the system needs to operate in specific situations to satisfy the driver. These situations encompass events where the separation of steering wheel and road wheels may lead to unique behaviours when compared to traditional steering systems. To better understand these use-cases, Ford Motor Company conducted multiple customer clinics as well as expert studies to define the requirements of the SbW system. One key question to be answered was, if a SbW system requires an electro-mechanic locking device to prevent misalignments between steering wheel and road wheel position. Other items of interest are feedback actuator sizing and strategies to mitigate hand and road wheel misalignment. This paper describes how a preliminary set of requirements were derived for Steer-by-Wire system to function without a feedback actuator locking device. Special attention was given to minimize system sizing and power consumption while achieving customer satisfaction.

Contemporary partially automated passenger cars assist the driver with the aid of longitudinal and lateral control systems without claiming the entire driving authority. The driver has the possibility to regain full control over the vehicle and relies on consistent feedback of the vehicle’s driving state through haptic, optic, acoustic and kinesthetic sensing channels.The steering system is the key element for shared lateral motion control with its steering wheel as the driver interface and its steering assist unit as the interface for lateral control systems such as lane keeping assistance. Depending on driving scenario as well as configuration and parametrization of the lane keeping assistance system, the driver can feel the system’s presence and activity to a greater or lesser extent compared to steering without lane keeping assistance system.Even if the actual lane keeping performance is improved by the assistance system, the driver might react skeptical or reject the technology due to an unpleasant steering feel. In order to solve this dilemma, an optimal cooperative assisted steering feel must be identified specifically for partial automation.This research introduces an objective characterization method based on key performance indicators for assisted steering feel in the context of lane keeping assisted steering. Subjective assessment criteria and driving scenarios for individual evaluation are defined. Vehicle measurement data from driving maneuvers served as a basis for the extraction of characteristic key performance indicators. This method can support the development of a pleasant assisted steering feel and therefore improve vehicle safety.

Current solutions for steer by wire force feedback actuators (FFA) based on steering column-integrated actuators require a huge effort for integration as design spaces used by head up display, climate systems or knee airbags are infringed. Additionally the crash element in the steering column limits the available retraction length of the steering wheel. A solution highly integrated in the steering wheel based on Joyson Safety Systems (JSS) active front steering concept enables the introduction of Steer-by-Wire (SbW) for any vehicle platform and automation level along with a maximum interior flexibility: Ranging from the pure integration of SbW-Systems in existing vehicle platforms to retractable or foldable and stowable steering wheels.

HiL testing as a standardized methodology takes real components into consideration, such as entire steering systems. The capabilities and possible use cases of these systems depend on the performance of the test bench and the maturity of the underlying real-time model. This paper describes a new level of performance steering test benches including the possibility of subjective steering feel tests.

The hub-steer system by which the additional front wheel steer of the vehicle is avail-able with no modification of the external layout configurations of the existing steering and suspension systems has been developed. The control algorithms of the hub-steer for improving the vehicle handling characteristics during steady circular turning and also for improving the vehicle transient response characteristics to steer input are introduced. Following to the simulation studies, the experimental investigation into the effects of the hub-steer system with the control algorithms using a conventional passenger vehicle equipped with the hub-steer system are carried out on a proving ground.

Currently, the application cycle of a steering system goes together with the life cycle of a vehicle application. Significant changes in function and content are typically introduced through new vehicle applications and platform architectures. With the fast development of connected vehicle functions, new chassis applications and innovations can be introduced during the life cycle of a vehicle via over-the-air system updates.What made the Smartphone so successful that we all have one? A powerful, flexible, software-upgradable platform architecture that comes to life with new downloadable applications is a major part of the answer.Steer-by-Wire will have the same impact in a connected and software-defined vehicle: Elimination of the I-shaft eliminates constraints in packaging and functionality. It improves new functions like Automatic Emergency Steering and enables functions that we have not yet even thought of but that will develop over the coming years. The steering wheel is transforming into a Human Machine Interface by creating additional degrees of freedom for haptic interaction between driver and vehicle – like fly-by-wire in the aerospace industry.The connected, software-defined vehicle will feature new software functions, updated over the air over the lifetime of the vehicle, that keep the product portfolio fresh. Therefore, the connected, steer-by-wire–equipped vehicle brings multiple trends together: connectivity and software.

A Consortium of Companies and Universities cooperated to design and manufacture electric motors for brake actuation. The project, in an Industry 4.0 framework, aimed to combine the design of both product and process.The electric motors for brakes have been optimized to shrink as much as possible the geometric dimensions while keeping high output torque, with the constraints of reduced production cost and extremely high level of reliability and performance.A smart production plant has been studied and optimized together with the electric motor design.Multi-objective optimization has been used to design the brushless DC motor. Fifteen design variables were considered for the definition of stator and rotor geometry, pole pieces and permanent magnets. The performance indices are peak torque, efficiency, rotor mass and inertia. The design constraints refer to components stress levels and temperature thresholds.The physical mathematical models used for optimal design refer to electromagnetic field and related currents computation, to thermo-fluid dynamics simulation, to local stress and vibration assessment. A surrogate model based on Artificial Intelligence has been used to speed-up the simulations. An Artificial Neural Network model, trained with an iterative procedure, was employed.Pareto-optimal solutions resulting from the design process are presented. Significant improvements of the performance indices with respect to a reference solution have been found.

Well-known for its brake system components, e.g., the vacuum pump for brake systems, HELLA develops a digitally controlled actuator for brake-by-wire applications with a small design environment, high dynamics, and extended diagnostic functionality. Besides the functionalities in the brake system like ABS or EPB, the actuator can also provide Park Brake Actuator functionalities in a vehicle system.

The paper investigates the importance of wheel-individual drive and brake systems for the development of vehicle dynamics control systems for automated road vehicles. Based on the findings from the Formula Student competition, system requirements for wheel-individual drives for automated driving are developed using the example of vehicles from the Munich University of Applied Sciences in the categories Electric (FSE) and Driverless (FSD). The conceptual system design as well as the technical implementation of the competition vehicles will be reported in detail. A further focus lies on software requirements and the structure of the control systems. Special aspects of safety and comfort in automated driving are discussed using the system description of the trajectory tracking control of the FSD vehicle. In addition, simulation results of driving operation are presented in order to show the safety gain due to the stability reserve set by means of continuous wheel-individual drive and brake control.

The main function of a vehicle braking system is to decelerate the vehicle predictable and reliable in any driving condition. Overheating of brake components can cause undesirable effects, such as brake fading or boiling of brake fluid. To ensure safe operation, aerodynamic concepts such as brake ducts, deflectors or brake disc ventilation have been introduced and steadily improved. These measures ensure sufficient heat-rejection but can reduce brake performance under rainy conditions, due to water ingress towards the brake. This phenomenon is called “brake wet fading” and results in a decrease of the friction coefficient between brake pad and disc.During the vehicle development process, brake components (pad and disc materials) are tested on component test benches. However, realistic environmental and aerodynamic boundary conditions in the vehicle cannot be applied during these tests. In order to obtain more realistic results, measurements for brake wet fading are taken on the test track in later development stages, although environmental conditions such as side wind and ambient temperature, rarely remain constant. This makes direct comparisons between different test configurations difficult.For these reasons, FKFS developed a new test procedure for brake wet fading in the FKFS Thermal Wind Tunnel. It provides a robust test environment in which aerodynamic measures regarding brake wet fading can be evaluated. This paper presents the brake wet fading test procedure and correlation measurements with road tests. Results of the new brake test procedure show good agreement with those from on-road measurements, with a deviation of less than 3% in friction coefficient. With this level of accuracy achieved and a superior reproducibility, the tests in the FKFS Thermal Wind Tunnel for brake wet fading can be considered an improved alternative to on-road tests – in dry and wet conditions.

Smart tires are systems that are able to measure temperature, inflation pressure, footprint dimensions, and, importantly, tire contact forces. The integration of this additional information with the signals obtained from more conventional vehicle sensors, e.g., inertial measurement units, can enhance state estimation in production cars. This paper evaluates the use of smart tires to improve the estimation performance of an Unscented Kalman filter (UKF) based on a nonlinear vehicle dynamics model. Two UKF implementations, excluding and including smart tire information, are compared in terms of estimation accuracy of vehicle speed, sideslip angle and tire-road friction coefficient, using experimental data obtained on a high performance passenger car.

This paper studied the vehicle running resistance prediction limitations based on tyre Rolling Resistance Coefficient (RRC) reduction. Tyre RRC reduction is one of the approaches used to increase fuel consumption efficiency of automobiles. It is known that the RRC value can vary with loading, velocity and temperature, and that the latter has the largest effect. Current tyre developments challenge the trade-off between maximum braking forcee coefficient (μ) and RRC, and present high thermal sensitivity of tyre tread rubber hysteresis loss property. Since different temperature conditions are ordered in ISO28580 tests which is used for Tyre RRC measurements and Road-Load tests which is used for vehicle running resistance measurements, the RRC is rendered less meaningful for estimations of running resistance than intended. The relation between RRC under Road-Load test conditions (RRCRL) and under ISO test conditions (RRCiso) is investigated with the focus on temperature effect. It is found that the estimation of vehicle running resistance improvement by reducing RRCiso on the current tyre development processes is not representative enough of the improvement that can actually be obtained.

With the emergence of electromobility, demands on driving comfort are changing. Replacing the internal combustion engine with an electric drive train eliminates one of the main sources of vehicle noise and vibration, increasing the influence of those caused by road unevenness. As the only components making contact with the road, tyres filter out or amplify road excitations according to their frequency response. Due to their complex design and multi-material structure, a complete and accurate description of these frequency response characteristics is difficult to achieve. Multibody simulations used in the early phases of a vehicle development process to determine chassis and full vehicle frequency response utilize specialized physical tyre models for this purpose. The most widely used parametric models determine the correct frequency response based on vibration measurements (e.g. cleat tests). State-of-the-art approaches for the evaluation of such measurements are based on the Fourier transform and Power spectral density, which limit the insight into the frequency domain to only the frequency con-tent and its magnitudes. The aim of this paper is to provide a deeper insight into the frequency domain of the tyre vibration by implementing the concept of wavelet analysis. By analyzing real measurement data of tyre cleat tests, some vibration phenomena and the advantages of the proposed methodology will be discussed.

For all-season tire development a snow testing session is needed. Snow testing is possible and economically convenient only in a limited period and specific test centers. Therefore, tire development on snow is not achievable out of these boundary conditions. A prediction of snow performances during spring/summer/autumn testing actually is not feasible.The aim of the study is to identify sets of all-season tire design parameters with same snow performances, rolling resistance and rolling noise but different performances on dry/wet surfaces, of brake, comfort and handling, free to be tuned based on the vehicle target attributes. Pattern geometry (PG), tread compound shore hardness (TSH) and glass transition temperature of tread compound (GTT) have been selected as tire design parameters.To support the study, the Design for Six Sigma Methodology (DFSS) has been applied. DFSS is a structured approach to obtain the state of maximum robustness in product design. The optimization of the Ideal Function related to the Intended Function (lateral and longitudinal accelerations defined as Output Response, hereafter OR) of the component (tire) is obtained selecting proper Control Factors and Levels (hereafter C.F., which are PG, TSH and GTT) under systematic variation of Noise Factors (dry/wet/snow surfaces, hereafter N.F.) and Input Signals (car speed, hereafter IS). The result of DFSS approach, processed to objective evaluation, has been to identify the optimal combination (sets of all-season tire design parameters) of the above Control Factors and Levels to make the tire minimally sensitive to Noise Factors (dry/wet/snow surfaces) that causing variability in the output responses of component (tire performances).In summary, the effects of PG, TSH, and GTT on the trade-off between snow performances, rolling resistance, rolling noise and driving dynamics have been identified.

The digital transformation for vehicle, chassis, systems and tire design is on its way for the sake of vehicle performances, lead-time and cost reduction. It leads to deep changes into automotive industry design processes and Michelin leads these fast-evolving trends and technical strategies with a complete approach from virtual tire design to tire models delivered to the OEM and fast iterations.Based on some on-going application cases, the study will show a range of possi-ble efficient virtualization of the chassis-tire development on different perfor-mances such as vehicle dynamics, max handling, interior noise or rolling re-sistance.It will be explained how FEA calculations can be connected to tire models’ pre-dictions to virtually design different specification letters and pre-screen some de-sign orientation without building any prototype tires.

Since 2016, vehicles are tested for noise emissions in accordance with the standard UNECE R 51.03 [1], where the measuring track must be in conformance with ISO 10844:2014. In Vauffelin near Biel (Switzerland), DTC AG has such a track at its disposal, and as an accredited test laboratory to ISO 17025, is able, among others, to measure motor vehicle noise in accordance with the UNECE R 51.03 standard. In order to remain within the scope of this article, the following section will focus on measurements of M1 class vehicles.