Research On Group Control System Of Tractor

The paper designed a group control system of tractor based on ultrasonic positioning technologies. A driver could operate several agricultural vehicles that less labour needed. The efficiency and precision of the agricultural production could be enhanced using the group system. The infrared-ultrasonic positioning distance measured system based on the MCS-51 singlechip was used for the positioning system of the first vehicle. The least square method was used for the path planning. A PID tracking controller was designed depend on the state information of the second vehicle, and the computer simulation experiment of the PID controller was carried out.(1)System introduction: Including tractor group,infrared-ultrasonic positioning system, information acquisition control system, steering control system and tracking control system.(2)Design of the positioning system: Include establishment of locating model and the ultrasonic range-measurement system. Positioning technology is the key problem of the automatic navigation system. The paper established a position model depending on the discussion of the position relation between the first vehicle and the second vehicle. The opposite-type ultrasonic ranging was used to measure the distance between the two vehicles, and the coordinate of the first vehicle was calculated by the measured distances. In order to enhance the measurement accuracy, the ultrasonic velocity in air was corrected in the system.(3)Design of the information acquisition system: Including the fixing device and software design of the velocity sensor, course angle sensor and the other state information sensor. Transducer calibrating and performance testing were done through the MFC-Program on the personal computer. A steering driving device was designed, and the personal computer could control the driving wheel by sending the control signal to the DC motor driver.(4)Path planning and controller design: Path planning is one of the important factors which can influence precision of navigation. The system transformed coordinates of first vehicles relative position points collecting by positioning system, and then using the least squares fitting out driving path of second vehicle. Taking lateral deviation error and heading deviation as inputs, steering angle as output, PID tracking controller was designed. Computer simulation indicated that PID tracking controller possesses good quality, it can make second vehicle follow the first vehicle.(5)The straight-line following control test was carried out, and the test result indicated that the maximal lateral deviation of second vehicle was 5cm while the speed was 0.27m/s in 30m driving.