Potential of elastodynamic analysis for robust suspension design in the early development stage

In the chassis development process, requirements for each subsystem are deduced from complete vehicle targets regarding safety, ride comfort and driving dynamics. After the design of individual components, they are integrated into respective subsystems resulting in a complete vehicle. Late modifications in the development process after vehicle testing resulting from insufficient quality of simulations (e.g. because of disregarded effects or parameter uncertainties) and unnecessary target conflicts (e.g. regarding package) due to disregarded solution spaces lead to increasing development costs and time. Chassis development is focused on the design and optimization of the suspension system. Characteristic values calculated from kinematics and compliance are in the center of interest and play a decisive role in evaluating chassis performance. Interactions with the steering system are partially modeled with reduced complexity or not considered at all. This paper deals with a newly developed approach to evaluate suspension systems considering steering properties without a complete vehicle. For this purpose, analysis of a complete front suspension system including steering system is carried out using multi-body simulation. The suspension model comprehends kinematic and compliant properties. The steering system is modeled with relevant elasticities as well as speed-dependent steering assistance. Stiffness properties of the suspension system, including steering system, are studied using the compliance matrix of the suspension system. The focus is on the analysis of the compliant steering axis by means of the compliance matrix method in comparison to the kinematic steering axis. The proposed method is also used to calculate corresponding characteristic values for the suspension system. These are analyzed for relevant load cases. The objective is to gain further insights into suspension design to characterize and eventually optimize suspension performance in the early development stage. Therefore, respective interactions between the individual subsystems (suspension and steering system) and their components are analyzed. Their corresponding influences on the overall system are quantified. The advantage of considering compliant effects and the mentioned interactions for robust suspension design is shown.     «

In the chassis development process, requirements for each subsystem are deduced from complete vehicle targets regarding safety, ride comfort and driving dynamics. After the design of individual components, they are integrated into respective subsystems resulting in a complete vehicle. Late modifications in the development process after vehicle testing resulting from insufficient quality of simulations (e.g. because of disregarded effects or parameter uncertainties) and unnecessary target confli...     »