The knowledge of the suspension kinematic points are of main interest for many engineers in order to create complex multi body system (MBS) models of road vehicles for benchmarking or in-depth investigation on the suspension. In many cases, those either are known from OEM construction data or are commonly determined with the help of contact giving multi-axis coordinate measurement machines. Another literature-discussed approach is the indirect determination under usage of Kinematics and Compliance (KnC) measurements.

The method presented hereinafter has the advantage of an easy integration in the standard KnC measurement process, reducing both time and costs. As a result, the hard point information obtained will transfer the real suspension to the simulation in the same conditions as on the test rig. This will be advantageous for pursuing investigations in case of special consideration of the position of the vehicle relative to the (virtual) test environment.

At the Institute of Automobile Engineering of the TU Dresden, a systematic method for the identification of kinematic point positions (x-, y- and z-values) using a hybrid photogrammetric and optimization approach has been developed. In a first step, the kinematic point positions are approximately determined using a high resulting optical measurement system. The suspension is positioned at the respective wheel deflection, typically because of the vehicles empty weight with or without an additional drivers weight. In a second step, the approximately identified hard points are used as initial values of the subsequent iteration process as to find possible spatial positions of kinematic points in a small range. Therefore, the KnC simulation results from an MBS model in ADAMS/Car are compared to the KnC measurements from the Suspension Motion Simulator (SMS) test rig iteratively. The objective is to minimize the errors between the KnC characteristic curves and the simulation.

The iteration is realized with a simulation exchange between ADAMS/Car and MATLAB. For the purpose of validating the developed identification method, the kinematic points have been measured by a coordinate measurement machine directly as well. The differences between identified positions of kinematic points and those gathered from the measurement machine show to be sufficient for the desired modelling of the suspension.

The trends towards increasing popularity of high performance SUVs require a novel assessment of “trade-off” between driving dynamics and rollover stability, which represents a new challenge for chassis design in the concept phase of chassis development. However, the rollover behavior has been typically investigated by means of experimental test maneuvers with prototype vehicles, which require a large amount of resources, such as measuring equipment, outrigger and roof loading. Besides, measurement data with measurement errors do not always provide satisfactory results due to external disturbance factors, e.g. environmental temperature and road surface. By contrast, a simulation environment can rule out the part of the aforementioned disturbance factors by reproducible simulation maneuvers in order to reduce the development expenses and obtain a better understanding of the rollover behavior. Within a cooperation project between Audi AG (Germany) and TU Dresden (Germany) five previous works have focused on the vehicle modeling, model verification, validation, analysis methodology and physical effect chains analysis for rollover behavior. However, a study into existing literature reveals that the interaction between yaw instability and roll instability has not been investigated sufficiently to date. Especially the question arises, to what extent the oversteer tendency (lateral instability) affects the rollover behavior (roll instability). Therefore, this paper aims to analyze the motion couplings between yaw and roll dynamics to explain the interrelation between oversteer tendency and rollover behavior, using the developed nonlinear two-track model with full axle kinematics and compliance, a dynamic steering and a nonlinear tire model. Firstly, a new criterion to describe the dynamical oversteer tendency in the nonlinear limit range of driving dynamics has been defined, which can be regarded as a further development of the traditional definitions of oversteer tendency in the linear range. Secondly, the rollover criticality has been quantified by means of a new maneuver in order to gain a comprehensive comparison between different vehicle configurations. Subsequently, different chassis parameters of the reference vehicle have been varied to investigate the relationship between driving performance and rollover stability. Finally, the results of the study are interpreted and discussed. Through analysis in this paper, the driving dynamics both in the linear and nonlinear range are evaluated to identify the operation principles between dynamical oversteer tendency and the rollover behavior. Summarizing the acquired know-how together, recommendations for design targets in the early phase of chassis development are derived. Newsworthy: 1. A new criterion to describe the dynamical oversteer tendency in the nonlinear limit range of driving dynamics 2. Systematical investigation of the interaction between oversteer tendency and rollover behavior 3. Parameter study to build up the understanding of the nonlinear physical chains of rollover behavior

With the continuous digitalization of the vehicle development process, virtual design methods play an increasingly important role. Representative load profiles, which can be determined for example with the aid of multi-body system simulation, are required for the reliable design and validation of complex elastomeric bearings such as engine mounts for conventional and electrified drive trains. Due to the complex material properties and complex designs of today's elastomer and hydro mounts, the virtual representation of these components is a challenging task.

In already published researches (46th Conference of the "DVM Arbeitsgruppe Betriebsfestigkeit") it could be shown that the current standard characterization of elastomeric bearings using static and dynamic stiffness as well as loss angle is only partly appropriate to build up and parameterize exact models for the virtual load data determination. On the basis of multi-axial load tests of selected engine mounts, which are done at the highly dynamic component test rig of the Chair of Automotive Engineering of the TU Dresden, physical effects with relevance for the durability could be determined. These are multi-axial static, dynamic and transient changes in stiffness and damping properties. With the knowledge of these effects, a complex model was developed which is designed for the representation of high dynamic loads, hydraulic damping and superposition effects of multi-axial excitations. The model is to be used primarily to calculate operating load signals using multi-body system simulation.

Within the context of the research described here, a complex multistep parameter identification procedure based on particle swarm optimization is presented. With this method it is possible to use complex stochastic signals to identify the model parameters. The first step is to determine the static stiffness of the bearing model in the considered main direction. The uniaxial dynamic parameters are identified afterwards. In the following, the dependence of the uniaxial dynamic parameters on the deformation amplitude is evaluated. Finally, the parameters of the model elements are identified which are dependent on the deformation of the secondary directions (multi-axial model components). The described procedure allows a modularization of the complex bearing model, whereby the model complexity can be adapted according to the application.

Multi-axial test rig measurements showed a significant improvement in the image quality of measured load signals compared to standard models for the newly developed model and the parameter identification process. The simulation error is used as evaluation criterion and the signal damage is considered by means of a standard fatigue strength evaluation. Different types of elastomeric and hydromounts are investigated for validation. Furthermore, the simulation quality of the modelling process outside the fitting range is evaluated. With the help of these investigations it can be deduced that the methods work robustly and will be suitable for practical use after a few adjustments. The investigations contribute to an improved and validated digital representation of elastomeric bearings with a focus on load data determination.