Improve Handling Stability for Path Tracking of a 4WIS Vehicle Based on Sliding-mode Method

Four-wheel-independent-steering (4WIS) vehicle with more degrees of freedom in steering control satisfies the high demand on handling performance of autonomous driving application. This paper proposes a control framework to improve the handling stability for path tracking of a 4WIS vehicle. Based on the lateral and heading error model in Frenet coordinate system, a LQR controller gives four-wheel steering angles to follow the reference path. With the ideal vehicle state gains generated by kinetic constrains and ideal steering center offset, the sliding-mode state feedback controller can effortlessly deal with the path disturbances and model uncertainties. Rear-wheel compensation angles which aims to adjust the vehicle state are added with the four-wheel steering angle above to compose 4WIS angles. Simulation results in CarSim-Simulink environment show that the proposed control framework is effective in enhancing the smoothness of the steering behavior and then the handling stability for path tracking of 4WIS vehicle.