Design And Implementation Of Motion Control System For Vehicle Chassis Detection Robot

At present days in China, the vehicle chassis security checking is normally operated by user holding the vehicle inspection mirror, which reply on the vehicle convex lens imaging technology. This method was found unable to deliver an ideal result especially in the dim environment constantly. Another method is building special vehicle chassis detection platform which the relative detecting equipment is fixed on the ground, less time but higher cost and poor flexibility. By comparison, the foreign devices not only having better performance but also equipped with more functions, including video recording, etc. However, no matter the domestic device or the foreign device, the users are required to manipulate by holding the device in a short distance, which has a certain life security threat to operators. Under this situation and marketing opportunity, it is necessary to develop the automatic vehicle chassis detection equipment instead of human operated inspection, which will not only protect human safety, but also fulfill the job with a higher efficiency.The automatic vehicle chassis detection robot is combined of mechanical module and function control module. The control module is the central technology for the whole system, which will give the robot all directions and orders of the proper actions and function. The design in this paper is referenced by the deep analysis of the function, application and current developing status of the wheeled mobile robot, in China, and calculated the kinematics model of three-wheel omni-directional mobile robot in detail; introduced the control of the DC motor; deeply analyzed the Proportion-Integration-Differentiation, PID control theory. This design applied the Cortex-M4, STM32F407 as the central control chip, and built the hardware control platform, accomplished the design of STM32 control module and power driving circuit which mainly including STM32 minimum circuit, peripheral interface circuit, Pulse Width Modulation, PWM controlled motor driving circuit and power supply circuit, detail introduction were provided in this paper. The control system software is developed under MDK 5.17 developing environment, which completed the programming of clock initialization module, PWM signal generation module, quadrature encoder module, TIMER7 module, and a serial port module, infrared obstacle avoidance module, PID control algorithm, speed decomposition function module based on the FreeRTOS operating system. Introduction of Free RTOS and the Free RTOS based on STM32F407 is provided in this paper as well.At last, the design finished the test progress, which was mainly monitored from system function performance, including the closed-loop testing, localization error testing and comprehensive testing of vehicle chassis detection. Under the test of FreeRTOS operating system, the motor response time is less than 0.5s, which successfully met the reference speed with only 0.9% overload. The system can provide clear visual under 0.4-0.6 m/s speed stage with a slice difference, which proved the system is functional.