12th International Munich Chassis Symposium 2021

Inhaltsverzeichnis

1. Frontmatter

2. Challenges for a Smart Mobility Service Provider

   Moo Sang Kim

   Abstract

   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.

3. Study to Assess the Controllability after Chassis Component Damages on the Dynamic Driving Simulator

   Thomas Kersten, Georg Ungemach, Bernhard Schick, Maximilian Böhle, Moritz Martynkewicz, Nils Harendza

   Abstract

   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.

4. Enhanced Ride Comfort Evaluation on the Driving Simulator with Real-Time Multibody Models

   Ivan Mula, Guido Tosolin, Xabier Carrera Akutain

   Abstract

   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.

5. Optimizing the Vehicle Development Process by Combining Driving Simulators and Virtual Test Driving

   Alexander Frings, David Ewbank

   Abstract

   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.

6. An Innovative Rear Axle Concept for Optimized Longitudinal Comfort

   Stefan Büchner, Roland König, Ralf Stroph, Martin Waldmann, Anton Tworek

   Abstract

   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.

7. Development Process of the Multi-link Torsion Axle (MLTA) – A Space- Optimising Suspension for BEVs

   Tobias Niessing, Jens Olschewski, Xiangfan Fang

   Abstract

   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.

8. How an Electric Drive in a Semi-trailer Improves the Overall Vehicle Performance

   Johannes Heseding, Thomas Dieckmann

   Abstract

   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.

9. Development of an Objective Evaluation Method for Manual and Automated Parking Maneuvers

   Thomas Boscher, Adrian Günther, Korbinian Scheck

   Abstract

   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.

10. The HEAT is on! – Functional Safety of Chassis Functions for Highly Automated Public Transportation

    Marcus Perner, Jens Matyschik, Veit Lemke, Martin Gebhardt, Simon Heine

    Abstract

    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.

11. Indy Autonomous Challenge - Autonomous Race Cars at the Handling Limits

    Alexander Wischnewski, Maximilian Geisslinger, Johannes Betz, Tobias Betz, Felix Fent, Alexander Heilmeier, Leonhard Hermansdorfer, Thomas Herrmann, Sebastian Huch, Phillip Karle, Felix Nobis, Levent Ögretmen, Matthias Rowold, Florian Sauerbeck, Tim Stahl, Rainer Trauth, Markus Lienkamp, Boris Lohmann

    Abstract

    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.

12. Automated Endurance Testing and an Outlook to AI

    Fabian Pfitz, Schaefer Max

    Abstract

    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.

13. New Approaches to Vehicle Health Management via a Digital Twin

    Joe Klesing, Peter Schmitt, Michael Story

    Abstract

    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.

14. Experimental Nonlinear System Identification of a Shock Absorber Focusing on Secondary Ride Comfort

    Ronnie Dessort, Maximilian Meissner, Sebastian Kolmeder, Günther Prokop, Jan Kubenz

    Abstract

    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.

15. On the Design of Front-To-Total Anti-roll Moment Distribution Controllers for Enhancing the Cornering Response

    Marco Ricco, Matteo Dalboni, Patrick Gruber, Miguel Dhaens, Aldo Sorniotti

    Abstract

    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.

16. Feasibility Study for Ride Comfort Application by Functional Vehicle Models: New Excitation Method and Model Extension

    Lorenzo Falchi, Florian Goy, Christian Ludwig, Alessandro Salgarello

    Abstract

    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.

17. Innovative Rear Axle Steering with Large Angles

    Magnus Rau, Ralph Michalski, Björn Spangemacher

    Abstract

    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.

18. Development of Large-Angle Rear-Wheel Steering System Perfecting Small-Turn Performance and Natural Steering Feeling at Low Velocity

    Yohei NAGAI, Yoshiaki TSUCHIYA

    Abstract

    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.