12th International Munich Chassis Symposium 2021

Hyundai Motor Group’s vision is to become a Smart Moblity Service Provider (SMSP), and to this end, there are largely four areas of technological innovation required in the chassis sector: electrification, robo-facturing, mobility and autonomous driving. In the following electrification section, Hyundai Motor Group’s first EV platform called the E-GMP (Electric-Global Modula Platform) is introduced, while the autonomous driving section touches upon reliability in regards to system redundancy and system monitoring. When it comes to mobility, low-floor skateboard platforms for PBVs (Purpose Built Vehicles), integrated chassis module for robo-taxis, and innovative technologies such as the UAM are currently under development. Lastly, in the area of smart factory, the company envisions the future mobility smart factory pursuing the concepts of by-wiring/modularization/standardization design, assembly automation and build-to-order.

The demands for shorter development times, reduced costs and prototypes make a greater use of virtual methods in the development process necessary. However, the real driving experience in a road test still offers essential insights for engineers and management. In particular, controllability tests through structurally damaged chassis components are extremely time-consuming in road tests and can therefore only be conducted to a limited extent. Moreover, they are often not reproducible or not representative, since the occurrence of damage is difficult to control over time and the tests can also be dangerous. On the other hand, purely virtual methods cannot adequately represent the driver’s reaction and driver assessment of controllability.In a feasibility and potential study, solutions and methods based on a dynamic driving simulator were developed. The Driver-in-the-Loop method using a driving simulator enables the precise control of a wide range of damage patterns and a broad spectrum of driving situations, while always offering a high level of safety in the test conduction. In addition, it records the human reaction and makes the controllability subjectively experienceable and assessable. Certain variants can also be presented to the management with this method and made experienceable for the decision-makers. In this way, important decisions and setting the course in the development can be supported. Overall, the method could save a lot of time and money.The University of Applied Sciences Kempten together with the affiliated institute MdynamiX has build-up a dynamic driving simulator with a novel rail and movement concept, which was designed for vehicle dynamics and enables further applications such as ADAS/AD, HMI, functional safety. The concept was developed by Williams F1 and industrialized by AB Dynamics. The high dynamic visualization and environment simulation with low latency time and high level of details was developed by rFpro. The overall simulator system is characterized by exceptionally high lateral and vertical dynamics and a very realistic vehicle dynamics behavior and related driving experience.The question now arises whether the controllability in case of vehicle damage can be reliably perform in such a driving simulator. The simulator thus offers good conditions for the study. Therefore a method for model design and simulation of the failure of selected chassis components using the MSC ADAMS Multi-Body Simulation (MBS) environment was developed. Furthermore, a transfer of the vehicle behavior into the simulation environment IPG CarMaker was worked out and the application of the methodology in real-time simulations was verified. Thereby replacement models of the different damages in IPG CarMaker were created, e.g. for the transient and dynamic wheel behavior. These were transferred to the dynamic driving simulator, where they were tested for controllability in the context of “driver-in-the-loop”. In order to be able to compare and validate the controllability between simulator and real test. The controllability tests with several subjects were examined subjectively and objectively and compared with the behavior in the simulator. The paper will present the method and the given results of the study and further potentials for damage and failure possibilities.

With the aim of moving a significant part of ride comfort development from physical to virtual, IDIADA and Toyota Motor Europe (TME) have been working on an advanced driving simulator set-up, where a full multibody vehicle model and a physical tire model run in real-time on a driving simulator. Firstly, a vehicle model was created in Simpack and made capable of running real-time (RT). Model creation was followed by model validation using proving ground measurements. Secondly, the Simpack RT model was integrated by IDIADA on their VI-grade DiM250 driving simulator. This required validation of the motion platform: signals taken at IDIADA’s proving ground were replayed to assess the simulator response accelerations and frequency ranges relevant for ride comfort. Lastly, an on-site activity took place in which professional evaluators drove a physical vehicle on IDIADA’s proving ground, back-to-back with driving the corresponding vehicle and track on the simulator. Subjective feedback from evaluators was taken in both the physical and virtual environments to establish their similarities, and a cross-check against objective signals was performed. The collaboration between IDIADA and TME is ongoing to refine platform response and overall methodology.

This paper is intended to provide an example in which ways the vehicle development process can be optimized through the combination of driving simulators and virtual test driving including a virtual prototype. It describes, how these optimizations can lead to increased cost efficiency, reproducible test cases and higher quality.Driving simulators reduce the leap between hardware-in-the-loop (HIL) and conventional test drives with real prototypes. Driver-in-the-loop (DIL) methods can help to gain important knowledge concerning the system characteristics and the vehicle behavior at a much earlier stage in the development process. A subjective impression of the expected driving experience can thus be experienced early on. DIL can be implemented with the open integration and test platform CarMaker and the driving simulators from VI-grade. This solution can be used in all classes of driving simulators.On the path to SAE automation level 5 and when developing ADAS/AV, the necessary interaction between driver and vehicle increases. Thanks to a full feedback from the simulator, the user is able to evaluate the ADAS functions and their influence on the driver. The simulator allows to test and optimize the behavior of these functions in a safe way, early in the development cycle.To increase efficiency in the development process, previously configured virtual vehicle prototypes are further used on the driving simulator. The presented solution offers different operation modes that allow to insert components of one or the other partner and to build on strengths according to already existing data or customer requirements.

This paper describes the design process of an innovative suspension concept for improved longitudinal comfort, especially with the difficulty of a heavy electric motor on the rear axle. The longitudinal compliance of a 5-link suspension needs no longer to be determined solely by the bushings of the rear subframe, but rather to a large extent by the wheel guiding elements of the suspension system. This task is mainly coped by the upper and lower trailing links. However, even with fairly soft bushings the wheel carrier is prevented from twisting, which compromises vehicle dynamics.The paper includes the basic design concept of the so-called C-Link (Compliance Link) mechanism (which has also been patented) with its corresponding trailing links. Several possible solutions will be discussed and one promising way described in more detail. The design, simulation and CAD-design are aimed towards a BMW SUV. The elastokinematic behavior of the favored solution is simulated and optimized in Adams/Car. The optimization of longitudinal comfort without compromising vehicle dynamics is demonstrated.The objective is to improve the characteristics of longitudinal compliance and to keep the elastokinematic properties as close to the reference vehicle as possible; for improved comparability. The simulation results are discussed extensively.

The twist-beam axle is widely used in front-wheel driven battery electric vehicles (BEV) of the compact and subcompact segments. Since its cross beam requires major lateral and vertical design space, it is a limiting factor to the rear end of the battery package. Therefore, the goal of this work is to introduce a new rear axle concept, the so-called Multi-Link Torsion Axle (MLTA), that allows to relocate the transversal beam behind the rear wheel centers. This is done by using a reversed installation of a twist-beam axle and integrating it into a longitudinal Watt’s linkage. By doing so an increased and connected volume in the underbody of the vehicle is obtained which can directly be assigned to the battery design space. In this way, the available volume for the battery can be increased by almost 30% in comparison to the conventional twist beam axle. The usage of the Watt’s linkage also leads to the increased compliances. This paper shall introduce the new rear axle concept and its potential regarding the packaging of BEVs as well as the kinematic and elasto-kinematic design process to retain the advantages and tackle the downsides. In order to examine the performance of the suspension the research project “E-MLTA” was started in October 2018. The goal of this project is to develop the suspension concept based on the academical and industrial standards and later implement it into a small-sized passenger car.

The present paper deals with improvements in vehicle performance and efficiency using of electric driven (semi-)trailers towed by a tractor. The special focus of this paper is the possible improvement of the overall vehicle performance by adding a precise controllable electric drive in the trailer. Achievable efficiency gains or range extension for BEV trucks are discussed in other publications. Here, a description of various functions is given which improve traction and acceleration behavior, vehicle stability & safety and comfort in special driving situations. The basic idea behind the presented concept is the integration of the trailer eDrive control into the brake- and stability systems of both, truck and trailer, with the possibility to ensure safe and efficient torque distribution by incorporation of all relevant systems in truck and trailer. The concept makes use of the standardized (and in future) adapted ISO-11992-2 truck-trailer communication link as well as ZF’s detailed knowledge and capabilities in the field of electric drivetrains and vehicle control.

For many drivers, parking is a necessary challenge. There are even drivers who avoid certain parking spaces because their parking skills seem to be insufficient. Without doubt, there are drivers who are very good at parking but also drivers who are less good at it. Similarly, in modern vehicles you will find parking maneuver assistance systems (PMAs) which do this task very well and those which do it much worse. In attribute-based development, the pursuit of goals based on objective key performance indicators (KPIs) are essential. To be able to evaluate manual parking maneuvers as well as PMAs, the University of Applied Sciences Kempten (UAS Kempten) in cooperation with MdynamiX has conducted a customer study with 21 participants and different PMAs. The generated data was used to develop a method for the objective evaluation of parking performance in general and to correlate this with a subjective evaluation. The goal of this new evaluation method was to analyze the parking maneuver in its different phases, from the selection of the parking space to the final standstill of the vehicle and even parking out. Different steering, braking and acceleration strategies were examined in their characteristics and the customer experience, too. For example, the question arises as to which shunting speeds are favored and whether it is better to steer when stationary or while driving, which could have a major effect on e.g., comfort experience, tire wear etc. In addition, the question arises which approaching and related braking and acceleration strategy is perceived as more pleasant. The manually driven parking maneuvers define the reference and will be compared to the performance of the PMAs with the developed KPIs.

The mobility demand of people is a key enabler for autonomous driving and transportation technology. Nowadays, several research projects find practice in public studies. IAV as a technology specialist is developing a shuttle for highly automated public transportation within the research project HEAT. This paper presents an insight into chassis development of the prototype. First, an overview of the project aims is given. To realize safe driving on open road for test operation, functional safety has to be considered carefully. Therefore, the paper puts focus on functional safety issues starting with the background and general strategy. After that, essential excerpts are given to understand further steps. Within the current development phase, a shuttle attendant observes shuttle driving behavior and conditions on open road. The attendant is able to take over and react for de-escalation, if necessary. Knowledge from operation on public road is used to enhance functional abilities of the shuttle. Therefore, this paper presents aspects of a chassis safety concept for safe travelling with focus on SAE-Level 4. The paper sums up with a discussion of the current challenges and perspective.

Motorsport has always been an enabler for technological advancement, and the same applies to the autonomous driving industry. The team TUM Autonomous Motorsports will participate in the Indy Autonomous Challenge in October 2021 to benchmark its self-driving software-stack by racing one out of ten autonomous Dallara AV-21 racecars at the Indianapolis Motor Speedway. The first part of this paper explains the reasons for entering an autonomous vehicle race from an academic perspective: It allows focusing on several edge cases encountered by autonomous vehicles, such as challenging evasion maneuvers and unstructured scenarios. At the same time, it is inherently safe due to the motorsport related track safety precautions. It is therefore an ideal testing ground for the development of autonomous driving algorithms capable of mastering the most challenging and rare situations. In addition, we provide insight into our software development workflow and present our Hardware-in-the-Loop simulation setup. It is capable of running simulations of up to eight autonomous vehicles in real time. The second part of the paper gives a high-level overview of the software architecture and covers our development priorities in building a high-performance autonomous racing software: maximum sensor detection range, reliable handling of multi-vehicle situations, as well as reliable motion control under uncertainty.

In the 21st century, also known as the century of automation, automated endurance testing of e.g. chassis components will become more and more important in order to be competitive to other vehicle manufacturers. Automation can not only can guarantee the reproducibility between different test runs and thus shortens the development time and costs of vehicle components, but also enables us to test complex maneuvers of an interacting vehicle fleet e.g. highway pilot (ADAS). Thus, automated testing will become absolutely mandatory in future. In the following, we will discuss in detail the newly and self-developed software components that enables us to automate the testing of e.g. chassis components. Finally, we will give an overview of the advantages and disadvantages of the proposed solution and will discuss how to embed artificial intelligence (AI) into a predictive control design. We will highlight the difference between learning-based and non-learning based control and will end with simulation and experimental data.

The connection of a vehicle to the cloud in combination with machine learning algorithms offers new approaches to vehicle health management. New insights are gained not only by monitoring an individual vehicle but also by comparing the meta-data of an individual vehicle with those of the entire fleet. A benefit of these insights is better prediction of the remaining useful life of a chassis component, which enables preventative maintenance and in turn increases the vehicle owner’s perception of enhanced vehicle dependability. This is particularly important in the context of automated vehicle fleets, which are expected to have a much higher usage rate than privately owned cars. Further benefits include reduction of warranty and cloud-based root-cause analysis.The paper covers the underlying concepts of vehicle health management, including the “digital twin,” and describes a steering use-case, as well as Integrated Vehicle Health Management standardization frameworks.

A continuously rising level of virtualization throughout all development phases plays an important key role to reduce real hardware tests and the corresponding amount of expensive prototypes. Highly accurate models are necessary to transfer test drives on the road to complex multibody simulations or to enable a subjective evaluation on a dynamic driving simulator, respectively. Simultaneously, highly automated and autonomous driving leads to increased customer requirements regarding ride comfort characteristics, especially due to road excited vibrations. Since the automotive shock absorber is a central element in the process of suspension tuning, modeling its complex nonlinear dynamic behavior is crucial. Therefore, a new modular and real-time capable modeling concept based on local linear model networks is proposed in this contribution. Extensive component measurements of various shock absorber setups focusing on different secondary ride comfort characteristics were carried out and serve as a reference for both parameterization and the definition of required model accuracy. An efficient process of model parameter and topology optimization is shown. In this context, the model is validated by using stochastic excitations derived from real full vehicle measurements on representative roads.

In the last three decades a relatively wide literature has discussed the potential vehicle dynamics benefits of the control of the front-to-total anti-roll moment distribution generated by active suspension systems, either based on actuators located within the individual corners or controllable anti-roll bars. However, because of the nonlinearity of the involved phenomena, there is a lack of systematic model based design routines to achieve the reference cornering response in steady-state and transient conditions through active suspension controllers, and for the integration of suspension control with direct yaw moment control. This paper targets such knowledge gap, by introducing design tools for front-to-total anti-roll moment distribution control, based on: i) optimizations using a quasi-static model for the computation of the non-linear feedforward contribution of the controller; ii) a novel linearized vehicle model formulation for linear control design in the frequency domain; and iii) a nonlinear vehicle model formulation to be used as prediction model for nonlinear model predictive control. A set of simulation and experimental results shows the benefits in terms of: a) understeer gradient tunability; b) increased maximum achievable lateral acceleration; c) increased yaw and sideslip damping; and d) energy consumption reduction.

Ride comfort has become one of the most important vehicle characteristics perceived by the costumer, on the same level of style, infotainment, safety and performance. In the last years, OEMs have been investing more and more time on improving ride comfort characteristics, in order to keep up with the increasing customer expectations. Today’s high level has been achieved combining two branches of vehicle dynamics development: testing and simulation.The role of vehicle dynamics simulation has been extended massively in the past years, reducing development time and costs for physical prototypes. Multi-body models are commonly used for ride comfort and handling simulation: they ensure good correlation with real measurements at the cost of high computational time and preparation effort. As most multi-body models are computationally not yet capable of real-time execution, functional models with highly reduced degrees of freedom have been developed. This enables OEMs to use virtual prototypes to perform subjective evaluations at early stage (e.g. Driver in the Loop). While handling properties can be represented quite well, limitations are still existing for higher frequency effects happening for example in ride comfort.The Chassis CAE and Controls team in the HMETC Chassis department has investigated the capabilities of functional models for ride comfort development, focusing on the vertical excitation path (e.g. tire, spring, damper, top mount). The results obtained with the multi-body software (MSC Adams/Car) were compared against those of the functional model (VI-grade VI-CarRealTime) for ride comfort frequency range [0–30] Hz. A simplified excitation methodology consisting of sinusoidal shaped road profiles with different amplitude and frequency has been introduced to evaluate both tools in a controlled environment. The limits of the functional model have been analyzed and shown deficiencies in the frequency range beyond 5 Hz. To improve the functional model in this aspect a model enhancement of the rubber connection between damper and the vehicle’s body has been implemented.

The aim of Mercedes-Benz was to make the new S-class as easy to handle as a compact car in big cities, combined with an excellent handling performance. This impressive driving function is realized by using a rear axle steering with large steering angles up to 10° as well as an integrated vehicle control for steering, braking and active suspension. The benefit for the customer is shown in all vehicle handling categories: impressive benefit during parking maneuver and perfect city agility with low steering effort during cornering, the turning circle is reduced up to 2 m, and an extraordinary handling performance and stability regarding vehicle dynamics at high speed. The rear axle steering is available in two different options, the standard steering with approximately 4.5° and the rear-axle steering with large angles (10°). This system is part of the success story of the new S-class and achieves an excellent customer perception and performance.

In the 1980's, rear-wheel steering systems were widely spread among Japanese automobiles for improvement in making a small turn at a low velocity as a main purpose. However, almost all the rear-wheel steering systems disappeared due to high cost and unnatural feeling at the time of steering. Recently, the increasing number of manufactures adopt the rear-wheel steering systems for purposes of improving steering responsiveness and vehicle stability. However, it is strongly recognized that the unnatural feeling given to a driver, which is represented by “teacup-ride like feeling”, during anti-phase steering at the low velocity is a characteristic of the rear wheel steering. In this study, control laws were developed with a side-slip angle and a yaw rate being set as target vehicle characteristics, and a large-angle rear-wheel steering system perfecting natural feeling and small-turn performance was developed.

MOBIL ELEKTRONIK is an owner-managed family company from the region of world market leaders near Heilbronn.

A specially designed test rig is used to determine the compressibility of brake pads. With this test rig, the cold compressibility can be determined according to ISO 6310. A batch of 32 brake pads is examined. For each brake lining, not only is the K6 value determined, but also the complete force-displacement curve recorded.Furthermore, a chamber furnace is to be used to pre-load the brake pads thermally. Here, a case of abuse is shown in which the brake lining is exposed to high temperatures. The cold compressibility is then determined here again.Another investigation includes the influence of the age of the brake pads on the compressibility. A chamber furnace is used for this in order to reproduce artificial aging of the brake linings. The knowledge gained is particularly relevant for the development of lifelong brakes.With the help of the force-displacement curves obtained, an attempt is then made to reproduce the non-linear material behavior in an FEM system as well as possible. Existing material models are used for this and parameterized accordingly. Finally, the material models are compared and their suitability assessed.

An innovative Hardware-in-the-Loop (HiL) test bench for brake systems and controller development is presented. It integrates a complete brake system into a HiL test bench, the so-called Brake System Integration HiL (BSI-HiL). A brake system is incorporated into a test bench with soft real-time and large-scale automation components - from the pedal to the wheel brakes. The soft real-time simulation environment enables an extensive development process from Model-in-the-Loop (MiL) over Software-in-the-Loop (SiL) and a digital twin of the HiL to the complete BSI-HiL application. It is primarily designed for the development of brake systems, ABS, ESC and ACC control logics and features for automated driving. The vehicle model and the test environment are created in MATLAB Simulink and simulated in soft real-time. Emphasis was placed on an easy and continuous development process. By creating a similar test environment for all development stages, controller development becomes straight forward. The evaluation environment enables fast performance analyses and comparisons between tests but also development stages Mil, SiL and HiL up to real vehicle tests. The simulation runs on a conventional PC or laptop, no dedicated real-time environment is needed. An EtherCAT connection is utilized for communication, as this allows high update speeds for large data exchange. The brake system of a C-segment car is used and mounted on a small form factor and transportable test bench. With the BSI-HiL’s modularity, various brake systems from different manufacturers can be realized. The components and the architecture in use allow for a cost-reduction compared to conventional brake HiL’s with similar performance.

A new mobility system, which can be mounted directly between the damaged tire and the wheel is presented which enables fast recovery of mobility for the customer. The mobility ring system consists of two resp. three parts, a ring divided optionally into two parts and a carrier cross.

Traditional manufacturing methods for aluminum alloy wheels have either high tool costs (forging) but good properties or lower properties, which result in higher weight (LPDC). For that reason, the Mubea Cast Forging is introduced as innovation that combines the superior material and wheel properties of forging with the design flexibility of casting. The patented casting process with two squeezing steps is described as well as the shortened heat treatment and sophisticated quenching. It is demonstrated that a fine-grained, porosity-free microstructure can be produced. The high material and fatigue properties are discussed and compared to the traditional methods using the example of a 20-inch AUDI wheel, originally designed for forging.

The change towards electrified powertrains in passenger cars leads to increased material utilization of chassis components and especially chassis attachments. The wheel attachment is no exception, facing e.g. increase of axle loads, wheel dimensions, cornering loads due to tire grip and center of gravity improvements. At the same time lightweight design approaches on its attached components are applied.The wheel attachment has a special standing due to its increasing dynamic load cases combined with being a “customer interface”. Therefore a reasonable amount of reliability and safety margin is very important, which needs to be tested at an early stage of the development process. The presentation gives an overview on the current changes due to physical and “customer based” requirements, failure modes and suitable test procedures ABC Umformtechnik applies on wheel fasteners to prevent failures. A test & analysis procedure for fastener load measurements is being presented, leading to detailed knowledge of dynamic axial and bending loads in a wheel/chassis fastener at its critical failure area. Also a dynamic fatigue test approach is presented to create fatigue data (Wöhler- curves) of the fastener at dynamic bending loads at constant preload, similar to its real driving dynamic load cases.This detailed understanding of occurring loads at the fastener itself enables improved safety in all chassis fasteners, by hardware testing and finite element simulation approaches at these same time, leading to improved design processes in an early stage of development.

Increasing levels of electrification and automated driving systems are resulting in the replacement and augmentation of vehicle functions with electrically controlled e-motors. These ‘smart actuators’ are increasingly complex, incorporating complex functional safety solutions, cyber security, and performance algorithms. They are increasingly developed using digital twin simulations to intensive automotive standards such as ASPICE, ISO26262 and AUTOSAR. This requires high development effort across multiple engineering disciplines.Although the power, safety integrity and physical implementation of these smart actuators vary widely, they can be built from a limited sub-set of functional architectures. To exploit this similarity the ZF reusable foundation architecture ecosystem presented in this paper allows new product lines to build on the development effort of previous products. This ecosystem includes functional safety, systems architecture, digital twin models, test-cases, electronic circuit libraries and software components. As a result, ZF has significantly reduced the development effort across a wide range of smart actuator product-lines.

The electrification of suspension systems in vehicles and especially in hybrid and electric vehicles is ubiquitous. With the striving for higher performance and the simultaneous increase in weight, mechanical, electromechanical and (semi-)active suspension systems based on 12 V or 48 V low voltage (LV) power trains are reaching their dynamic limits. One approach to improve performance is to use suspension systems and components that can be applied to the high voltage (HV) vehicle power train that is being used more and more frequently. The use of HV suspension components results in many advantages such as punctual available power without having to set the voltages higher by means of so called DC/DC converters. However, there are also many challenges in this field that do not allow a simple exchange of the hardware from LV to HV without further considerations. During development, for example, the question of functional safety and the behavior of the HV suspension components in case of a crash arises. It is also necessary to take a closer look at what the main cost drivers in development are, whether a component has to be actively cooled due to the generation of heat or how it affects the overall range of an electric vehicle.Silver Atena GmbH has specialized in the development of LV and HV electronic components for decades. This includes also development and production of HV suspension components. This paper is intended to give a brief overview of the current challenges and the uncertainties in the complex HV suspension components development process. In the main part, after the motivation for using HV in suspension systems, it is shown which problems can arise from the replacement of LV by HV suspension components. Since their development can quickly reach a high degree of complexity, a good overview of key requirements will be pointed out here. The conclusion gives an outlook on the still open questions and challenges to be solved.

Important for an all-electric vehicle, especially when used in an urban area, is still lightweight design. Simple chassis systems for small urban vehicles covering those weight limitations often lack an acceptable drive comfort and driving stability in extreme situations. A new active chassis suspension designed for such an urban car is in development at the DLR Institute for Vehicle Concepts in the founded project Next Generation Car (NGC) Urban Modular Vehicle (UMV). This concept even provides active safety measurements regarding the demanding small overlap crash scenario. The main components are a composite transverse leaf spring, an orbital wheel bearing optional with an integrated electrical drive and an innovative wheel independent two axis steering actuator changing the toe and camber angle. For the realisation of this innovative concept a (partly) automated design and dimensioning process is going to be established.

Virtual methods in vehicle development processes are constantly getting a greater role over time. The benefits of such methods are lower the costs, speed up the process, explore a wider design space and increase the level of design detail before getting into physical prototypes; in recent years such methods are covering more and more the human perception and how the driver feels the vehicle. The case study presented in this paper is about the tuning of an EPS using Hardware-in-the-Loop methods to carry on the power steering development in a simulator using a steering HiL test-rig driven by human test-drivers. The work starts by analyzing the behavior of a production steering system of the same manufacturer using standard open loop maneuvers and track driving to collect objective and subjective metrics to assess the steering behavior. This phase has a strong importance in order to understand which objective parameters impact in certain specific subjective score. After first validation and decoding phase, the same metrics are then used to tune the EPS in development. The proposed development process allows to greatly reduce costs and time required to tune a steering system and has the side benefit to enhance the steering feeling of the driving simulator thanks to a deeper understanding of the developed steering system. Thanks to these improvements, the proposed process significantly contributes to the current SoA by showcasing new frontiers for virtual methods for vehicle development.

In the development of Electric Power Steering (EPS), calibration is the final step and is crucial for a good steering feel. Previous studies focus on design optimization of the mechanical system and control strategy of the EPS in the early phase of the development process, rarely addressing on-site calibration with physical prototypes. In this paper an EPS calibration method is proposed to meet strict objective targets of steering feel. The method is based on a theoretical model established between EPS assist parameters and steering torque characteristics. Parameters of the theoretical model depend on the electro-mechanical property of each vehicle, but they are identified with field test data during the calibration process instead of being calculated. The identified model is then used to obtain a new set of assist parameters that meet the steering feel targets. It is shown with test data that strict objective steering feel targets can be fulfilled with no more than two field tests, thus improving calibration efficiency without compromising accuracy.

Future regulations for emissions will increasingly focus on reducing respirable particles, which are caused by abrasion from brakes, tires and roads. PMP (Particle Measurement Program) under the United Nations Economic Commission for Europe (UNECE) has already defined a measurement cycle together with international organizations to measure brake wear on brake dynamometers. Questions about the sampling method and details about the measurement are open.This paper will focus on Brake Emissions as the regulations on the one hand are already on the way, and on the other hand the measuring methods are basically defined. Furthermore the central points are not chemical or legislative details, but a view from system and vehicle perspective.However, the focus of the regulation is currently only on passenger cars with internal combustion engines, since the measurement process only records the emissions of the “brake” component, without taking into account recuperation, for example.The exact definition of the limit values is still pending, but it can be assumed that they will be based on exhaust emissions of internal combustion engines.There are numerous measures to reduce particle emissions, which either aim to generally prevent particle emissions from the brake or to filter the particles that have already been emitted.As a result, the volume of tests relating to the brake will increase massively, as all variants have to be tested and certified. On the other hand, the necessary changes to the brakes are also affecting other properties of the entire vehicle, causing e.g. compromises between performance, emissions and comfort.The automotive industry will then face a further increase in the challenges when considering tire and road abrasion emissions.

Brakes are tribological high-load contacts. Such contacts are characterized by the fact that the wear provides material in the friction contact, which can generate additional tribologically active contact surfaces there. In addition to the natural contact areas, wear dust in the boundary layer forms temporary contact areas. These contribute significantly to the resulting friction power.Over the last 20 years, scientific research has focused on the dynamics generated by wear in the boundary layer. The growth and destruction of the local contact areas formed by wear dust have been successfully used to explain time-variant effects. Thus, dynamic friction laws have been developed along with spatially resolved simulations that reflect the evolutions of surface geometry very precisely.Following investigations into friction dynamics, the demand for time-resolved predictions of wear, and in particular the wear dust load during braking is becoming increasingly important. For the description of brake dust loads, we have now set up highly automated high-precision optical measurements combined with a certificated particulate matter measurement system (TSI EEPS 3090) and several low-cost particulate matter sensors, which investigate wear and wear dust emission during braking over long periods of time. These measurements have shown that the wear and particle emission intensity also has its own time dynamics. The wear dust moves in the boundary layer between pad and disc. It is not only originally responsible for the construction of contact patches, but also fills reservoirs near the surface in various ways. The cavities are filled once and then emptied again. These reservoir dynamics seem to be characteristic for the output of wear dust in high load contacts in transient operation and modulates not only the friction coefficient but also the wear intensity in the friction contact.

Friction brakes are one of the main sources of PM emissions from cars today. However, due to the electrification of the powertrain, the share of friction brakes in vehicle deceleration is continuously decreasing. Due to the reduced number of braking applications and the lower brake pressure level, the amount of emitted particles also decreases. This is associated with the disadvantage of an increased potential for the formation of rust on the surfaces of the friction materials, which is expected to influence friction and wear. Due to the increasing challenge posed by corroded friction partners, drum brakes are increasingly used to decelerate battery electric (EV) and hybrid electric vehicles (HEV).In this study, basic investigations on the particle emission behaviour of drum brakes are carried out using an inertia dynamometer (LINK 3900-NVH). To ensure representative sampling, a constant-volume sampling system is used, which is optimised in terms of transport efficiency and particle distribution. Condensation particle counters (CPC) and filter holders (TX40) are used to determine PN/PM emission factors. CPCs with differently calibrated cut-off are used to evaluate the formation of nanoscale particle formations. In this context, special attention is paid to the influence of temperature on the particle formation process.From the comparison between rear-axle disc brake and rear-axle drum brake it could be proven that the predominant part of the wear mass remains within the drum, which affects the size distribution of the emitted particles. The ratio between PM10 and PM2.5 mass-related emissions factors decreases from about 2 (disc brake) to about 1.3 (drum brake). In addition, the emission behaviour is differentiated via the bedding procedure of the drum brake. To achieve a reproducible emission level, a doubling of the number of cycles (WLTP-brake cycle) is necessary. Due to a higher temperature level, nanoparticles could be detected during testing of the drum brake, whereby the number-related emission factor (PM2.5) was partly higher than for the disc brake.

The tire is the only force-transmitting element between the road and the vehicle. Thus, the tire mainly determines the driving dynamic properties of a motor vehicle. The tire is connected to the wheel hub of the vehicle via the wheel. Therefore, the wheel is the first connecting element between the tire and the body of the vehicle. As a result, the wheel has an impact on the driving dynamic properties of a motor vehicle. Unlike the known requirements for a vehicle wheel such as durability, low weight to minimize unsprung masses, brake cooling and low mass moment of inertia for dynamic load changes, so far the wheel bending stiffness, is not the major focus as an influencing factor in vehicle dynamics development.Nevertheless, the presented research reveals that the impact of wheel bending stiffness can have a significant influence on characteristic values such as cornering stiffness, aligning torque or high frequency behavior. Exemplary studies have shown that cornering stiffness can differ up to 5.3% between different wheel designs whereby the dimension of the wheels are the same. An approach will be presented, where measurement procedures and metrics for wheel bending stiffness are defined and state of the art lateral tire-wheel measurements on a MTS Flat-Trac and a static stiffness test rig are performed using different wheel designs. Ultimately, the goal of this study is to investigate and describe the dependency between wheel bending stiffness and the change in typical tire characteristics as well as to provide a virtual forecast for design and specification of wheels in the early phase of vehicle development process.

Due to the absent masking noise from the combustion engine, the transition from combustion engine cars to electrical cars yields more focus on the structure-borne noise induced by the tire/road contact. Consequently, the tire air cavity resonance noise is increasingly impacting the vehicle interior noise perception. Besides interior noise, also other tire performances such as rolling resistance are important for electric vehicles. Both performances are strongly influenced by the tire size and tire construction. Therefore, car manufacturers are looking for a dedicated tire model to perform simulation-based noise, vibration, and harshness (NVH) assessments for the car up to 300 Hz, and thus allowing to differentiate between different tires and sizes. In this paper, the authors show that the tire model CDTire/3D can fulfill the OEM full-vehicle simulation requirements satisfactorily. Several tire tests need to be performed to parameterize the CDTire/3D model. One of these tests is a standard cleat experiment performed on a dedicated drum test rig. In this paper, models have been created for different tires featuring the typical design space of a vehicle manufacturer. The authors then present the comparison of rough road rolling simulation results against measurements on a rough road drum test bench. In a second step the tire models are applied in a hybrid simulation approach that couples FEM (Finite Element Method) and MBS (Multi-body Simulation) for full vehicle predictions of structure-borne road noise.

Driving comfort is becoming increasingly important in the development of modern vehicles. As the only link between the vehicle and the road, tires have a significant impact on the vehicle ride and NVH behavior. Nowadays, the influence of tires on overall vehicle comfort is evaluated by expensive vehicle testing sessions. To reduce this effort and to support the tire submissions, an earlier comfort assessment of tires based on their behavior at component- and system-level is essential. In this paper, the influence of the tire vibration behavior on ride comfort is investigated and correlations between the dynamic component- and system-level coupling/cutting forces are derived. Recently in-house developed chassis NVH and cleat tire test rigs were used for this investigation, enabling measurements under a wide range of operating conditions (e.g. velocities, wheel loads and cleat dimensions). Relevant operating conditions for the tire-related ride comfort assessment at component level are highlighted based on characteristic trends in frequency and time domain. On this basis the state-of-the-art measurement protocol used for the parameterization of physical tire models is discussed. Furthermore, the influence of the suspension system on the comfort values previously determined on tire component level are highlighted.

Two trends could currently be observed in the automotive industry which are affecting NVH development for new vehicles or platforms. On the one hand many axle systems are being adjusted for new electrified architectures, on the other hand virtualization and “front-loading” of the NVH tuning can be seen. The combination of both trends is challenging for OEMs. As a leading global automotive NVH development supplier, Vibracoustic has devised unique NVH axle test rigs and virtual approaches to support OEMs on their way to superior NVH performance.Vibracoustic employs proprietary NVH test rigs to analyze and optimize entire axles without the surrounding vehicle. Load cells at all interface points, acceleration sensors and other signal sources permit a comprehensive characterization of an axle while it is either subjected to hydraulic shake inputs at the wheel hubs or running on a dyno. Having benchmarked more than eighty axles this way, using our proprietary NVH KPIs we are able to comparatively assess any new axle and assist our customers in their NVH performance judging and optimization.If prototype hardware is already existing, the experimental axle results are used to validate simulation models, which are enabling the NVH optimization at an early stage of the development. For ride, shake and low frequency measures usually multi body models are used. Mostly handling-oriented multi-body simulation (MBS) models are enhanced to incorporate nonlinearities like friction and amplitude dependent rubber behavior. For higher frequencies, Finite Element models of the axle system or the entire vehicle are used. Both simulation approaches can be validated by Vibracoustic NVH axle analysis – and are the basis for further NVH optimization. The development process and unique contributions by NVH axle test rigs are explained in this paper. For a broader overview of our product and solutions portfolio, see [3].

The ongoing electrification process of passenger cars leads to constantly changing and increasing requirements regarding the NVH behavior of cars and their efficiency. In order to quickly meet these requirements, development processes are often supported by the use of simulation models. To reproduce the behavior of complex structures such as tires or chassis correctly, the simulation models must be parameterized based on test rig measurements. For measurements involving tires, the laboratory testing conditions usually exhibit a compromise between reproducibility and the correct representation of reality, especially for the surface texture of the test rig. The aim of this work, based on initial tests, is to demonstrate the potential of real road surface replicas on lab test rigs to close the gap between the derived behavior of tires on real roads and in a laboratory environment.

In a futuristic setting of automated driving, the driver commits the driving task to the vehicle and the steering wheel disappears into the dashboard. SteerByWire steering systems serve as key technology to implement this idea. The mechanical coupling between the steering wheel and the steered wheels is eliminated, which saves installation space and the steering wheel can be moved more freely and even stowed in the dashboard. Along with this, the vehicle is controlled via DriveByWire functions. Therefore, the vehicle's lane keeping is independent of the driver. Apart from automated driving, the DriveByWire functionality gives manual driving new opportunities to improve the driving experience, as well. The aim is to support the driver additionally in order to increase comfort, driving safety and agility.But how can these functions be developed? Are they delivering the anticipated progress for tomorrows driving? In order to answer these questions, it is necessary to develop and test new functions in first test vehicles. There are currently no redundant SteerByWire systems available on the market, which means that vehicle manufacturers have to set up their own systems in cooperation with their suppliers. However, this step is associated with very high costs and a long development time in order to set up a first redundant test system.In cooperation with Volkswagen AG and a number of suppliers, IAV has succeeded in setting up a cost-effective development platform. A column-type EPS serves as a ForceFeedback actuator and a DualPinion EPS as a rack actuator. In consultation with the respective supplier, these components are enabled for the DriveByWire application. In addition, a clutch is integrated into the steering column to provide a fallback level.This paper focuses on building a development platform and testing a SteerByWire system. Using the developed system, it is possible to make the new technology experience, develop new features and validate them.

Development of true Steer-by-Wire systems without a mechanical backup continues to progress in the marketplace. As with any vehicle safety-critical system, Steer-by-Wire system design must provide for uninterrupted, safe operation throughout the life of the vehicle. There are multiple approaches to achieve this objective, which can be different for various failure modes. When considering system safety of Steer-by-Wire systems, common topics of discussion include different failures modes unique to Steer-by-Wire, what constitutes a safe operating state, how long a vehicle should be allowed to operate when a next electrical component failure would lead to violation of a safety goal, and what vehicle operating conditions are acceptable as a safe state. Currently, answers to these questions vary significantly, with approaches and philosophies largely left to individual vehicle manufacturers. One way to improve this situation is to develop and acknowledge industry-wide safety standards. This paper presents several areas for consideration in establishing safety standards for vehicles equipped with true Steer-by-Wire systems and draws parallels to more familiar topics associated with Electric Power Steering. Initial recommendations are made for areas which would benefit from industry-wide consensus and establishment of standards to benefit OEM’s, suppliers, end consumers, and ultimately the entire industry.

Electric parking brakes are typically equipped with voltage and current sensors for control and safety purposes. Sensors for rotational or translational degrees of freedom of the actuator are not included for cost reasons. By usage of “sensorless” methods, these values can be measured or estimated through the already available electrical signals and hence contribute to a functional enhancement of the system without additional hardware costs. A new method is introduced for robust detection of an oscillation in the electrical motor signals of the electric parking brake whose frequency is proportional to the rotational speed. Hence, the motor can be used as an incremental encoder which allows for precise positioning of the leadscrew nut and in certain situations accordingly the brake piston. By this additional information about the system enhanced functions can be implemented. As examples a procedure for estimating the pad wear as well as control methods for a more accurate setting of the clamping force and clearance are presented.

Traffic-related emissions are strongly criticised by the public because they contribute to climate change and are classified as hazardous to health. Combustion engine emissions have been regulated by limit values for almost three decades. There is currently no legal limit for non-exhaust emissions, which include particulate brake and tire wear and resuspension. As a result, the percentage of total vehicle emissions has risen continuously. Since some of the particles can be assigned to the size classes of particulate matter (≤10 µm), these sources of particulate matter are of particular relevance to human health.To predict the amount of particles emitted as a function of the driving situation or driving condition, a comprehensive database must be prepared and transferred to a prediction model. This makes it possible to simulate environmental pollution in multivalent traffic scenarios. At present, no approaches have been described in the literature by whose application the emission indicators can be effectively predicted. Furthermore, the mechanisms of brake and tire particle formation are associated with highly stochastic phenomena that cannot be captured by traditional deterministic modelling tools. Therefore, machine learning algorithms are used in the present work to identify branched correlations between tribological properties, pad composition and operating conditions. Different experimental methods are presented to determine brake and tire particle emission models.In addition, an approach is presented which reduces the amount of emitted particles on the basis of a situation-dependent driving condition control, especially with regard to future semi-autonomous and autonomous mobility systems.

During normal driving conditions, wear particles are formed due to the friction between tire tread and road surface. To derive realistic particles for study purposes, basically, two approaches can be taken: Either collection outdoor under real usage conditions or indoor under very controlled conditions. The first approach is challenging due to many disturbing factors, while the second might be biased by choosing specific conditions. This article describes how both approaches are used in combination to ensure field relevance of high-quality characterization insights.Particle samples collected from the environment always contain material from both surfaces—the tire tread and the road, which is why in this context we refer to TRWP (Tire Road Wear Particles), which consist of combined material—roughly 50%/50% (by mass)—from both sources. To capture those TRWP outdoor under real usage conditions a special vehicle was used which is equipped with a vacuum cleaner system in the wheelhouse. For further evaluation the samples were further refined and analyzed. For better assignment of the collected material to the dedicated test tire a TiO2 marker was used. A trend between driving conditions and detected particle size was observed which must be further investigated.Under lab conditions the generated particles can be assigned explicitly to the specific compound and to the operation conditions. The particles are observed with optical methods direct at the sample wheel or separately offline after collection. The obtained images are processed applying methods from the field of “Particle Object Tracking”, such as Feature-Point-Detection and Blob-Analysis. As an outcome, individual rubber particles are identified, tracked and characterized. Finally, the size distribution of the particles can be concluded from the entity of all particles, whereby information about the shape of each individual particle is available. Through these insights on size and shape environmental impact of TRWP can be determined more accurately and—most importantly—suitable mitigation approaches can be derived.

Relaxed cruising with Active Cruise Control, without having to adjust the riding speed to the vehicle in front – already available in cars for years, not yet in series production for motorcycles. BMW Motorrad is the first motorcycle manufacturer to offer the Active Cruise Control (ACC) rider assistance system in the new R1250RT, giving motorcyclists a completely new, comfortable riding experience.This article presents the new rider assistance system for motorcycles in detail and discusses the motorcycle-specific features that need to be taken into account when integrating the system into a single-track vehicle. Starting with the integration of the radar sensor into the front of the vehicle, the functional adaptations especially for cornering, and the challenging driving dynamics of motorcycles. The display and operating concept and the consideration of functional safety, which is a further focus of development due to the newly created interfaces to the engine and braking system, are discussed.The article also provides an outlook on further assistance systems that could be introduced on motorcycles in the next few years. I.e. the expansion of environment sensor technology and the introduction of collision warning systems in both the front and rear areas of motorcycles.ABS, which is essential for rider assistance systems, plays a central role in the new BMW Motorrad Active Cruise Control. In particular, the roll angle-dependent ABS functions and the full integral function are explained in more detail.