Motion Control and Trajectory Tracking Control for a Mobile Robot Via Disturbance Observer

This paper investigates the tracking control of a wheeled mobile robot in the unknown environment. A disturbance observer is developed with utilization the integral filter. The proposed control scheme employs the disturbance observer control approach to design an auxiliary wheel velocity controller to make the tracking errors, which includes the velocity tracking error, the angular velocity tracking and the trajectory tracking error vector, as small as possible in consideration of unknown bounded disturbance in the kinematics of the mobile robot, and makes use of the disturbance controller to reject the unknown bounded disturbance. The approximation errors and the unknown bounded disturbance can be efficiently rejected by employing the integral filter. A major advantage of the proposed methods is that the position (or velocity/angular velocity) and the desired trajectory (or velocity/angular velocity) are no longer necessary. This is because the observer controller “tracking” both the mobile kinematics and the unknown bounded disturbance. Most importantly, all signals in the closed-loop system can be assured to be uniformly ultimately bounded. The system stability and convergence of the motion control and the trajectory tracking errors are proved using the Lyapunov stability theory. Simulation results are provided to verify the proposed control strategy. It is shown that the control strategy is feasible. Key-Words: Disturbance observer, Velocity tracking, Trajectory tracking, Time-varying disturbance, Mobile robot, Motion control, Lyapunov stability