On One Approach to Constraining the Combined Wheel Slip in the Autonomous Control of a 4WS4WD Vehicle

This paper presents an approach of wheel slip constraint in controlling an autonomous four-wheeled steering and four-wheeled drive (4WS4WD) vehicle. This approach regards the quasi-steady state of the combined wheel slips as the target to limit. We introduce a control structure of wheel torque and wheel steering to transform the original constrained tracking problem to that of state regulation with norm-bounded control. For the transformed problem, an integral compensation with low-and-high gain technique is exploited to simultaneously eliminate steady-state error of the path tracking and enhance utilization of the constrained wheel slip. Simulation shows that the proposed scheme effectively renders the vehicle tracking along reference path within a prespecified threshold of wheel slip. Besides, a harmonious coordination between the wheel torque and wheel steering can be provided during the cornering control