| The omni-directional mobile robot with Swedish Wheels is extensively studied because of its many possible advantages,such as better flexibility, simpler structure and controlling more easily. This robot is suitable for the flat and narrow work environment and it can be used to carry goods in warehouses and participate in aircraft carrier scheduling.The specific goal of this study was to develop an effective control method, positioning and path tracking, for the robot.The main content consists of four parts: deriving positioning model with the robot’s kinematics and studying its error, investigating path tracking method and its error regulator, implanting the positioning and path tracking methods in a embedded control system (ECS) which is based on micro control units (MCU) and conducting experimentsFirstly, structure of the omni-directional mobile robot was introduced. The structure dimensions was determined by necessary technique data. Local and global reference frame of the robot were established based on the structural characteristics of the robot. According to the route that overall after partial, a common kinematic model of single Swedish wheel was built and then the overall kinematic model was obtained by combining these single models.The parameters of the position and orientation of each Swedish wheel in its local frame were determined and kinematic governing equations of the robot were derived by taking these parameters into the whole model.Secondly, By developing the mathematic positioning model based on odometry and gyroscope , update equation for robot positioning was obtained. Source of the positioning error was analyzed, and a error compensation model was developed followed by relative methods. Straight line and circle trajectory tracking algorithm was designed based on positioning. Then, path tracking error was analyzed and a Proportional Integral Derivative(PID) controller was developed for compensating the tracking error.Thirdly, the embedded robot control system was designed, including communication subsystem based on serial and parallel, positioning and servo motor control subsystem. Robot software framework based on Real Time Operating System (RTOS) was developed for positioning and geometric trajectory tracking,in which the robot overall control process worked.Finally, simulations were conducted aiming at verifying the algorithm for positioning and geometric trajectory tracking. The result of the simulations under different conditions were analyzed. Robot prototype testing environment and the methods of experimental data acquisition and measurement were introduced. The error of odometry and gyroscope was compensated through robot prototype testing. Position and orientation tracking error was analyzed under different test conditions. |
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