Abstract

A variety of theoretical and tracking control problems have been studied for various classes of nonholonomic wheeled mobile robot (WMR). The relative difficulty of the tracking control problem depends not only on nature structural properties of the nonholonomic WMR system but also on the tracking control objective. In this thesis several structural properties regarding controllability, stabilizability and nonholonomy of the kinematic state models of WMRs have been given, taking into account the restriction to robot mobility induced by the constraints. By using the concepts of degree of mobility and degree of steerability , this study provides a general and unifying presentation of the modeling issue of WMRs. For particular prototypes of WMRs, the posture kinematic models for WMRs are available in the literature. However, in this thesis, a more general viewpoint is adopted for the consideration of a general class of WMRs with an arbitrary number of wheels of different types. Three-wheel mobile robot-Nomad 200 used in the experiment is described in details. The control objective in this investigation is to determine a control law so that the robot can track a desired trajectory. Two control algorithms are therefore presented. The first control algorithm is using a "virtual vehicle approach", which is shown to be robust with respect to error and disturbances; the second one is a time-varying adaptive control algorithm developed for a general class of nonholonomic mechanical system, which guarantees the global stability of the closed-loop system. Simulation results with SIMULINK software and Nomad simulator confirmed the validity of the proposed algorithms, and the implementation of the both algorithms on a nonholonomic WMR, Nomad 200 platform, clearly, verify that proposed tracking control algorithms can achieve the control objective in a stable and robust way