The effect of subsystem characteristics on the performance of a concept vehicle with active rear steering for yaw motion control

A concept vehicle with active rear steering for yaw motion control has been developed at the TNO Road-Vehicles Research Institute in co-operation with PSA. The work has been carried out in the scope of a PROMETHEUS project, and is concentrated on the aspect of Safe Driving. The main objectives for the control design are improved vehicle stability and reduced drivers effort. The vehicle control system has been developed in terms of hardware, electronics and control strategy. During the development process, simulations were widely used to support the development of hardware components and control yaws. Relevant system characteristics have been identified with simulations and several systems are enhanced based on the simulation results. Testing has been carried out on components seperately and on the vehicle as a whole. The application of simulations in the process has been found essential for understanding the system behaviour. The paper describes what the influence of non-ideal component characteristics is on the overall vehicle behaviour of the yaw motion controlled vehicle. Studies have been made by simulations and by component and full vehicle testing. The results of simulation studies are presented. A simulation model for in-plane vehicle motions is used to study the effect of component characteristics on the vehicle behaviour. Other aspects of automotive components (price, durability, reliability, weight, size, power consumption, etc.) have been secondary in the development of the concept vehicle and as many standard automotive parts as possible were used. The main components that are analysed in the simulations are a micro processor and a hydraulic servo system. Both components can be modelled as a delay for the development of the yaw control system, which simplifies the development process. Only discretization in the processor calculation affects the vehicle behaviour significantly. These effects can be reduced considerably by using a higher resolution (i.e. 12 bits instead of 8 bits) in calculation.