Coordination Control of Path Tracking and Stability for 4WS Autonomous Vehicle

Path tracking and stability are two main considerations in autonomous vehicle control design. Compared with traditional front wheel steering, 4WS (four wheel steering) has better stability in high-speed steering, but the intervention of rear wheel steering will reduce the performance of vehicle's path tracking. In this paper, the linear quadratic optimal control theory is used to design a front and rear wheel coordinated control method for the path tracking problem of active 4WS autonomous vehicle, which can improve the lateral stability of the vehicle and have a better path tracking ability. First of all, 2-DOF vehicle dynamics model and optimal preview path tracking model are established and combined, then different weighting functions are selected for the front and rear wheels to optimize the vehicle state. In the environment of MATLAB / CarSim, the simulation of the high-speed double shift line condition is carried out. The results show that the proposed control strategy, compared with the classical proportional control four-wheel steering vehicle, improves accuracy of path tracking, reduces the lateral speed and acceleration, and improves lateral stability of the vehicle.