Research Of Path Tracking Controller Of Mobile Robot With Color Vision Based On CPLD

Path tracking is an elementary technique in vision guided mobile robot systems, and controller is the key in realizing the function of robot. At present, most of controllers are controlled by software and executive the program step by step according to the software instruction, and then there are some shortcomings' in stability, timely and reliability inevitably. So the development of mobile robot's controller is facing to new challenge. The complex programmable logic device (CPLD) breaks a new path for the development of robot's controller. Based on CPLD and Quartus II ,we design a special controller,which is built of pure hardware circuit. The controller can be used in the control of path tracking with its assorted peripheral circuit. The operation in controller dose not depend on software instruction, so it dose not have the disadvantage that consists in traditional controller.In this paper, Mobile robot's path tracking system is composed of three parts: visual system, control system, and driving system. Using the method of identifying the color path through image, the visual system gets the color and position of the path, then figures out the relative deviation between robot and the tracked path. According to the relative signal, the control system can command the driving system to do real-time trace. The controller is the key of path tracking system; we study it deeply in this paper. Because the visual servo control system based on image is direct to control actuator to use image feature, we put forward a kind of visual servo control algorithm based on image feature difference, which was used to path tracking control.In the study, the controller is designed with the method of software hardening and VHDL (a design description language used in IBM AS/400 processor). According to the designing course and the necessary function, the controller is divided into eight modules. Every module is described with VHDL, and then all the programs would be compiled, simulated and tested. It takes modularized method to design the system, so it is easy to be designed, maintained and extended.After the designing was finished, the controller is implemented in the CPLD and some experiments have been done, the results indicate that using CPLD as single controller chip in path tracking control has many advantages, for example, the program is criterion, the test of time sequence is facility, the modification of system is flexible, the hardware need not change on the whole, and the speed of mobile robot in path tracking can be enhanced to a great extent. It is a new and efficient method inrealizing the path tracking control of mobile robot.