Stability of 4WS Vehicle Based on Side Slip Zeroing Control: Influence of Steering System Dynamics

Some control strategies of four wheel steering (4WS) systems for automobiles have been proposed and studied in the past in order to improve maneuverability at low speeds and handling and stability at high speeds. An fundamental idea among these control strategies is to make the car body side slip motion zero from a view point of attitude control of the car body. There have been many reports on advantages of the 4WS handling and stability performances compared with the conventional front wheel steering system. But there is little study on steering system dynamics related with the four wheel steering systems to investigate into the steering torque or reaction torque which are strongly affected by the steering system dynamics.

This paper analizes the dynamic stability of the 4WS vehicle and the relation between the steering torque and the steering angle which are influenced by the steering system specially by side slip zeroing control. For this purpose a driver is modelled to be a hybrid steering model consisting of a visual feedback and a touch sensation feedback. Theoretical and numerical analyses show dynamic response characteristics of steering torque to steering angle, velocity dependent stability, comparison of step and frequency responses characterized by the side slip zeroing control.