Four-wheel steering vehicle stability under random wind excitation

In this paper, a three degree of freedom handling model with 4WS is used to study the vehicle straight line stability at high speed under random wind excitation. The model takes into account the driver model as an expert system to reduce the vehicle lateral deviation and steering system as a lumped mass spring system to incorporate its compliance. The linear optimal control theory (LQR) is used to derive the control action which is the rear wheel steering angle based on minimizing all state variables. The results are generated and presented in time and frequency domains as well as root mean square values. In comparison with the conventional 2WS vehicle, significant improvements are obtained especially for the vehicle lateral deviation and yaw rate.