Robust Integrated Control of Wheel Slip and Direct Yaw Moment for Stabilizing the Dynamics of Skid-Steering Vehicles

Abstract

This paper presents a robust integrated control system to improve the stability and the handling performance of skid-steering vehicles. The control strategy is based on two layers: direct yaw moment control and wheel slip control. In the first layer, the direct yaw moment is obtained based on the nonlinear sliding mode control theory using the exact second order yaw rate response of the conventional steering vehicle. In the second layer, the direct yaw moment is optimally distributed to the four wheels in order to calculate the torque command needed at each wheel individually. Then, the sliding mode control theory is used again to control the torque command at each wheel individually and maintain the wheel slip at the desired value. A closed-loop driver-vehicle system subjected to a turning maneuver accompanied with braking at different surface conditions is simulated in Matlab/SIMULINK to validate the effectiveness of the proposed integrated control system. The simulation results show that the combination of wheel slip control and direct yaw moment is essential for stabilizing the motion of skid-steering vehicles. Moreover, the proposed control system is robust against uncertainty in the adhesion between the road surface and the wheel.