Robust Control in Diagonal Move Steer Mode and Experiment on an X-by-Wire UGV

This paper proposes a novel X-by-wire unmanned ground vehicle (UGV)-unmanned ground carrier (UGC). To show functions of the UGV, the mechanisms and design processes of the key subsystems are described, especially the in-wheel motor-driven and independent steer subsystems. As an all-wheel-independently steered (AWIS) UGV, the UGC is able to achieve the diagonal move steer mode (DMSM) to improve the maneuverability significantly. To improve the path tracking performance in DMSM, a robust H_2/H_∞ chassis yaw controller is proposed, which uses the additional yaw moment provided by in-wheel motors to track the desired sideslip angle and avoid the yaw motion. The energy to peak and energy to energy performance of the sideslip angle and the yaw velocity are considered and handled by linear matrix inequalities (LMIs) approach during the H_2/H_∞ controller design. The parametric uncertainties and disturbances of the vehicle mass, the yaw inertia, and tire cornering stiffness are considered to improve the robustness. Finally, the step steer and lane change tests are conducted with the UGV testbed to validate the efficiency and robustness of the proposed chassis controller.