A Differential Torque Controller for Autonomous Wheeled Mobile Robots

Autonomous wheeled mobile robots, used in a variety of outdoor applications such as farming and mining, must traverse terrains with varying wheel tractions, resulting in wheel slip and deviations from desired trajectories. In this paper, a new differential torque controller is proposed. Inspired by a mechanical differential gearbox, the proposed model-based dynamic controller can drive the robot through surface changes without losing the desired velocities. This, coupled with an outer-loop kinematic controller, is used to demonstrate good tracking of trajectories under varying surface tractions. The ability of the controller to compensate for the surface change is tested by suddenly changing the surface under one or both wheels. The simulation results have shown that the dynamic controller compensates for the change in the surface, and the resulting position errors are driven to zero using the kinematic controller.