| In recent years, the trajectory tracking control problem of the omni-directional wheeled mobile robot has been widely studied. In this thesis, the omni-directional wheeled mobile robot, developed in Northeastern University, as a research object, establish its kinematic and dynamic models. Analysis of its motion characteristics, based on the kinematic model, hierarchical control scheme for the omni-directional wheeled mobile robot is selected to control the trajectory tracking problem. The fuzzy control, the sliding mode control, the quasi-sliding mode control and the fuzzy reaching law sliding mode control in the trajectory tracking controller design were researched in this thesis. The main work and accomplishment of this thesis includes:Firstly, the structural design features of omni-directional wheeled mobile robot are described. The kinematic model and dynamics model are established by using the coordinate transformation method. Based on kinematic model, hierarchical control scheme for the omni-directional wheeled mobile robot is selected to control the trajectory tracking problem according to its motion characteristics.Secondly, based on the kinematics model of the omni-directional wheeled mobile robot, several controllers are designed by taking the liner speed and the angular speed of the mobile robot as the control inputs, then, the simulation proved the correctness of the design method.(1)Fuzzy controller is designed for the omni-directional wheeled mobile robot’s trajectory tracking control, to achieve the desired trajectory tracking control.(2)In order to improve the robustness of the system, sliding mode controller is designed to effectively overcome the interference of the external uncertainties, and accordingly the simulation shows the effectiveness and feasibility of the design.(3)In order to weaken the sliding mode controller’s chattering, quasi-sliding mode controller is designed by taking saturation function instead of the original sign function, and simulation results show that it could weaken buffet well.Then, the reaching law sliding mode tracking controller based on the kinematics model of the omni-directional wheeled mobile robot is designed. The liner speed and the angular speed of the circular path are uniform in a limited time to achieve perfect tracking. Robot, the multi-input multi-output, highly coupled nonlinear system can be well controlled by this method. It can also weaken the chattering of sliding mode controller and has a very good robustness. Finally, we summarizes the work done, and put forward the prospect of further research directions and problems. |
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