Research On Path Plan And Motion Control Of Mobile Robots In The Navigation

Path plan and motion control problems are the key issues for autonomous wheeled mobile robots. These problems are not only very important to accomplish autonomous navigation and other complex intelligent tasks, but also embody perception ability and intelligence of robots. The model of the environment is grid map in which the robot needs to run the controller of path plan frequently, so heuristic search algorithm is used to design the controller of path plan. This paper designs the controller of trajectory tracking and path following based on nonholonomic kinematic model of wheeled mobile robot, and completes the goal of autonomous navigation for the mobile robot. The main research achievements are as followings.Firstly, development of navigation technology is introduced. The key technologies of path plan and motion control are analyzed. The methods are proposed to solve the problems in the application of path plan and motion control.Secondly, heuristic search theory in artificial intelligence is introduced, including heuristic information, evaluation function and admissibility of search algorithm. The controller of path plan based on graph search algorithm (A-Star algorithm) is designed by considering real-time property, optimality about the search algorithm and the problem of dead-zone. The controller can compute the path efficiently and find the optimal path in the global occupancy grid map.Thirdly, nonholonomic kinematic model of wheeled mobile robot is analyzed. Using the idea of integral Backstepping, a simple virtual feedback variable is proposed and a time varying feedback controller of trajectory tracking is designed via Lyapunov direct method. The way of following the path which is combined by the discrete way points is by using the controller of path following. This controller is designed via Lyapunov direct method and the theory of point stabilization. Simulation experiments verify the correctness and effectiveness of the controllers of trajectory tracking and path following.Finally, System structure of the J-Pot robot is introduced. The autonomous navigation experiments for the mobile robot are designed by using the programs of the controllers of trajectory tracking and path following. The programs which can be run in the upper computer of the robot are written in C language. The experimental results indicate the performance evaluation for the controllers. Because of simplifying algorithms for the controllers, the programs for the controllers can be easily written and the controllers are stable.