Control of Sideslip and Yaw Rate in Cars Equipped with 4-Wheel Steer-by-Wire

Abstract

This paper presents a new steering controller for cars equipped with 4-wheel steer-by-wire. The controller commands the front and rear steering angles with the objective of tracking reference sideslip and yaw rate signals describing the desired car lateral dynamics. In addition, the controller automatically rejects any disturbances in sideslip and yaw rate caused, for example, by μ-split braking manoeuvres or lateral wind gusts. The structure of the controller is based on a simplified model of the lateral Dynamics of 4-wheel steering cars. This structure allows an originally complex multivariable control design problem to be broken down into two simpler single-input, single-output (SISO) control design problems by means of the Individual Channel Design (ICD) methodology. Within the proposed structure, individual sideslip and yaw rate controllers, valid for varying vehicle speed, can be designed using classical linear control design techniques. An anti-windup scheme has been incorporated into the steering controller to mitigate the effects of the saturation or failure of the rear steering actuators. Results from a detailed non-linear simulation model are given to illustrate the controller's performance, robustness and integrity to rear actuator failure.