Trajectory tracking control for nonholonomic mobile robots with unknown parameters and bounded disturbance

The trajectory tracking control problem for a nonholonomic mobile robot with unknown system parameters and bounded external disturbances is investigated and a robust adaptive tracking control scheme is proposed in this paper. The main difficulty of tracking control of a nonholonomic mobile robot is that the kinematics is underactuated. To deal with this difficulty, an additional controller variable is created through variable transformation by using the traverse function method. With the additional control variable, the kinematic model of the nonholonomic mobile robot is no longer underactuated, thus, facilitating the control design for the nonholonomic mobile robot extensively. Finally, nonlinear adaptive control and parameter projection techniques are adopted to derive the tracking controller and parameter estimator through the Lyapunov function approach. It is shown with rigorous proof that with our proposed control scheme, the reference trajectory can be followed globally with an arbitrarily small tracking error. Simulation results also demonstrate the effectiveness of our proposed controller.