Trajectory Tracking Control Of Wheeled Mobile Robot

Recently, with the development of science and technology, research on robot has been widely investi-gated specially for wheeled mobile robot (WMR) because of its extensive application in many fields such as agriculture, industry, service industry, national defense industry and so on. The important point is that it is capable of heavy and dangerous tasks for human beings in the harsh environment. Therefore, it is of great importance both in theory and practice to deal with WMRs. This thesis focuses on dealing with the problem of trajectory tracking of WMRs. Kinematic controller, dynamic controller, adaptive law and disturbance ob-server will be designed for kinematic and dynamic model of the nonholonomic WMR based on Lyapunov function, backstepping method and technologies of sliding mode variable structure, adaptive, disturbance ob-server to deal with the problem of trajectory tracking of WMRs in this thesis. The main contents are concluded as follows:(1) The problem of trajectory tracking of kinematic model of nonholonomic wheeled mobile robots is addressed. The controllers are designed according to whether d=0(the distance between the mass center and geometric center). Firstly, for the situation of d=0, appropriate sliding surface and Lyapunov function are chosen for kinematic error system to design the kinematic controller based on the technology of fast terminal sliding mode. It is proven that kinematic error system globally asymptotically converges to zero. In addition, a finite time controller is designed for the kinematic error system. Secondly, for the case of d?0, a suitable Lyapunov function is selected to design a kinematic controller to make the closed-loop system globally asymptotically converge to zero. Lastly, the simulation is established to verify the effectiveness of the proposed algorithm.(2) The problem of trajectory tracking of the dynamic model with external disturbance of the wheeled mobile robot is considered. Firstly, a virtual speed controller is designed for the error system of the kinematic model to guarantee that the closed-loop kinematic system is globally asymptotically stable. Secondly, appro-priate sliding surface and Lyapunov function are chosen for the dynamic model to design a torque controller and a nonlinear disturbance observer which will make a feedforward compensation for the closed-loop sys-tem. Lastly, it is proved that the proposed controller can render the closed-loop system globally asymptotically stable with an appropriate choice of the parameters.(3) An adaptive sliding mode controller is designed for the problem of trajectory tracking of the dynamic model with unknown parameters and external disturbance of the wheeled mobile robot. Firstly, appropriate sliding surface and Lyapunov function are chosen for the kinematic model to design a kinematic controller based on technology of fast terminal sliding mode to make sure that the closed-loop kinematic system is globally asymptotically stable. Secondly, an adaptive sliding mode controller is designed for the dynamic model to estimate the unknown parameters and external disturbance and guarantee the dynamic error system is globally asymptotically stable. Finally, the simulation is established to verify the effectiveness of the proposed algorithm.(4) A new scheme is proposed to design an adaptive controller and a disturbance observer for trajectory tracking of dynamic model with unknown parameters and external disturbance. Firstly, an adaptive virtual speed controller is designed for the kinematic model with d?0 to guarantee the closed-loop system is globally asymptotically stable and estimate d online. Secondly, an appropriate Lyapunov function is chosen for dynamic model to design torque controller, adaptive estimators and a disturbance observer to make sure that the error system can converge to zero and estimate the lumped disturbance and compensate the system by a feedforward manner. Lastly, the stability of the closed-loop system is given and the simulation is established to verify the performance of the controllers and estimators.