Modelling and validation approach for the development of a yaw controlled passenger car

The objective of this paper is to present a systematic modelling approach to vehicle handling simulation, validation and optimisation. Moreover, special attention will be paid to the use of mathematical tools for the development of a passenger car with active rear wheel steering for yaw motion control. Several models for the vehicle as well as for the servo system have been used. In the early stages of research, conceptual models were used to define global specifications. Then, to develop steering strategies, relatively simple linear models were used. Component level models were used for trouble shooting and to investigate the influence of non-linear effects. By comparing the above mentioned models with results from driving tests and subsystem measurements, their limitations could be identified. A minimum model set-up for the analyses of inplane vehicle motions allowing fast parameter fitting has resulted in the so-called gyro-axle model. This model is an extended bicycle model including a front and rear axle, each with two rigidly connected wheels, as well as a correctly oriented roll-axis. In order to represent the vehicle sufficiently accurately, it proved necessary to add a relaxation length for the lateral forces in the tyre model. From a control point of view, a mere time delay proved sufficient to include the micro processor and hydraulic servo system used in the vehicle model for the development of the yaw motion control system. Computer modelling has been used succesfully for the vehicle system behaviour assesment as well as for control system optimisation. In a subjective evaluation of the yaw controlled passenger car, it was concluded that the developed feedback of yaw velocity setting contributes positively to many aspects of the handling behaviour.