On one approach to constraining wheel slip for the autonomous control of a 4WS/4WD vehicle

This work presents an approach to constraining wheel slip for the automatic path tracking control of a four-wheeled steering and four-wheeled drive (4WS/4WD) vehicle. The approach deals with and limits the quasi-steady state of the longitudinal and lateral wheel slips. A new control structure of wheel torque and wheel steering is proposed to transform the constrained tracking problem to that of state regulation with norm-bounded control. For the transformed problem, a low-and-high gain technique and an integral compensator are introduced to construct the constrained controller so that the utilization of the constrained wheel slip can be enhanced and the steady state error of tracking can be eliminated. Simulation shows that the proposed scheme can render the 4WS/4WD vehicle tracking along the desired path within a prescribed threshold of wheel slip, and can provide satisfactory coordination between wheel torque and wheel steering.