Nonlinear tracking control for mobile robots with nonholonomic constraints

Abstract

This dissertation addresses the nonlinear tracking control for the mobile robot systems that have nonholonomic constraints by using the Lyapunov direct method and the Input-output linearization method. The mobile robot systems in this study are two-wheeled mobile robot, car-like mobile robot, and trailer system linked with rigid free joint. In the tracking control of the mobile robots, few results have shown the globally asymptotic stability by means of the Lyapunov direct method. Therefore it is necessary to complete the globally asymptotically stable tracking control law for mobile robots. And a few researchers have applied the input-output linearization method to the mobile robot systems. They have considered the mobile robots as 2-input/2-output (only position) systems. However, the mobile robots can be considered as 3-output systems with orientation angle. Especially, for the tracking control of the trailer systems, a few results are reported. The navigation of the trailer systems is required for the automation of transportation in the seaport or airport because mobile robots have limits in the transportation capabilities. Therefore, it is necessary to discuss about the tracking control of the trailer systems. We propose a globally asymptotically stable (GAS) tracking control law for the mobile robot systems by using the Lyapunov direct method. Considering the posture term of the mobile robots completes the GAS tracking control law. The proposed scheme offers more direct and simpler method in stability analysis for the tracking control of the mobile robots. And a modified input-output linearization method for the mobile robots is proposed. We consider the orientation angle as another output variable. This scheme shows smoother control input trajectories for comparing the previous works. The stable responses are shown through the error dynamics analysis and the zero dynamics analysis. And we extend the proposed control schemes to the trailer systems. The ex...