Nonholonomic Mobile Robot Trajectory Tracking Control

Mobile robot is a mobile platform which is concerning about multi-subject comprehensive technology.Mobile robot has been playing an increasingly important role in high-end manufacturing and social life.Mobile robot belongs to a kind of nonholonomic systems in terms of analytical mechanics,therefore it is also called as nonholonomic mobile robot.Nonholonomic mobile robot has very high values in commerce and a wide application prospect and its control problems have gained more and more attention.The nonholonomic wheeled mobile robot is studied in this thesis.Firstly,its nonholonomic property is analyzed and then the control problems of asymptotic trajectory tracking and finite-time trajectory tracking are mainly studied in the respect of its kinematic and dynamic models,respectively.The main research work of this thesis consists of the following three aspects.Firstly,the control problem of trajectory tracking of mobile robot is studied based on its kinematic model and the asymptotic trajectory tracking controller is designed.For the strong nonlinearity of the original kinematic model,the chained-transformation is used to transform the original kinematic model of the wheeled mobile robot to chained-form system model and in turn the tracking error dynamics which have much linearity is obtained.Then the cascaded control method is used to divide the error dynamics into two subsystems.Under the framework of the cascaded control method,two controllers are designed for the two subsystems,respectively to make the two subsystems achieve global uniform asymptotic stability and in turn the error dynamics achieve global uniform asymptotic stability,so as to make the mobile robot track the reference trajectory asymptotically.Secondly,the control problem of trajectory tracking of mobile robot is considered based on its kinematic model and the finite-time trajectory tracking controller is designed.The chained-transformation is used to the original kinematic model as above,and in turn the chained-form tracking error dynamics are obtained.Then the error dynamics are divided into two subsystems and each of them is stabilized by a finite-time controller,in turn the whole error dynamics are stabilized by the two finite-time controllers,so as to make the mobile robot track the reference trajectory in finite time.Finally,the control problem of trajectory tracking of mobile robot is studied based on its dynamic model.The dynamic model with actuator dynamics is considered and the controllers designed before based on the kinematic model are seen as virtual controller laws.Then the voltage controllers are designed by the backstepping method so as to make the mobile robot track the reference trajectory asymptotically.