Robust Trajectory Tracking Control For Nonholonomic Mobile Robots

In this thesis, the trajectory tracking control for a class of nonholonomic mobile robots is studied. The emphasis is the robust trajectory tracking control for mobile robots with uncertainties. The main works of this thesis are listed as follows.Based on the kinematic model of a nonholonomic mobile robot, a feedback velocity control law is designed for trajectory tracking. First, the posture error model of trajectory tracking is established denoted by Cartesian coordinates in the local coordinates. Then the nonlinear state feedback control law is designed for the tracking error system using a control Lyapunov function. Under the proposed control law, the closed-loop system is uniformly asymptotically stable at origin, and asymptotic tracking for the desired trajectory is guaranteed. The following works are all based on the proposed kinematic controller.Based on the dynamic model of the nonholonomic mobile robot, a torque controller is designed, from which the actual control input of the dynamic system can be obtained. The designing of the controller is based on the backstepping technique. Firstly, an auxiliary velocity control signal is designed, which can make the tracking error asymptotically stable. Then to guarantee the actual velocity converge to the auxiliary control signal, an acceleration control law is designed. The actual control signal is obtained at last by the computed torque controller.The problem of trajectory tracking control for dynamic system with unknown external disturbances and inertia parametric uncertainties is studied, with the prerequisite that the external disturbances are bounded. A robust adaptive controller is designed, under which the influence caused by uncertainties can be overcome, and the robustness of the system can be improved.On the basis of the dynamic model, the drive motor dynamics is taken into account further in the control design. In this case, the control input of the system is the voltage of the motor. The trajectory tracking control for mobile robot system with uncertain inertia parameters and uncertain structure parameters is studied. An adaptive controller is proposed for this case to ensure robustness to the uncertainty of model parameters.The effectiveness of every designed controller is verified by the simulation results of actual models.