Lateral control of a backward driven front-steering vehicle

This paper addresses control of the lateral position and orientation of a backward driven front steering vehicle. The low speed associated with backward driving eliminates some challenges but introduces others in lateral control design. While slip angles are small and can be neglected, other small angle approximations can no longer be made. The curvature of the desired path can be very sharp requiring large steering angles. Two control strategies based on a nonlinear kinematic model of the vehicle are developed. One controller is based on input-state feedback linearization with no associated internal dynamics. The other controller incorporates preview and is based on input-output linearization with stable internal dynamics. A major portion of the paper concentrates on experimental implementation of the two controllers using an instrumented Navistar truck. The experimental performance on straight and circular paths as well as on transient curved paths is studied. Good experimental performance is obtained with a spacing accuracy better than 40 cm being achieved in the worst case transient paths. The use of preview turns out to be important with the preview-incorporating controller providing superior performance.