The performance of a vehicle with four-wheel steering control in crosswind

A nonlinear 5 degrees of freedom (DOF) system is used to model the dynamics of a four-wheel steering control vehicle. In the model the yawing and roll motions of the sprung mass of the vehicle are considered and the nonlinear differential equations of motion are derived. In addition, the crosswind model and the driver model are established in this paper. They are used to investigate both the conventional front-wheel steering (FWS) and the four-wheel steering (4WS) vehicle during a crosswind disturbance. Two different 4WS control laws are used. The first is an open loop control law (OL4) in which the rear wheel steering angle is only determined by the front wheel steering angle. The second is a closed loop law (CL4) in which the rear wheel angle is determined by both the front wheel steering angle and the yawing angle of the sprung mass of the vehicle. Simulation results indicate that the CL4 system significantly improves the vehicle steering stability in response to a crosswind disturbance.