| The proposal of precision agriculture has led to the research of intelligent agricultural machinery equipment.The performance of steering control systems in the research of tractor automatic navigation systems affects the control accuracy of the entire navigation system.After fully understanding the research status and development trends at home and abroad,this study used Dongfanghong SG250 tractor as a research platform to build an electro-hydraulic control steering system on this platform.Design the steering angle of the wireless acquisition system and the steering control signal calibration method.The specific research content and achievements are as follows:(1)Design and build an electric-hydraulic proportional control tractor steering system platform.The hardware of the two-position four-way electromagnetic valve,two-position three-way electromagnetic valve,electro-hydraulic proportional controller and other wireless control module for the steering angle signal acquisition control circuit were introduced and installed and debugged.(2)Analyze the steering system in the autonomous navigation system of tractors currently studied,and explain the problems in the accuracy of signal acquisition and the difficulty of device installation.It proposes to adopt more accurate measurement modules and wireless transmission technologies to improve the overall system accuracy and stability.Through the device selection,the high-precision inertial navigation module JY-901 and the low.power wireless transmission station WSN-02 were selected,and built a wireless measurement module for steering angle.Finally,the feasibility was verified through data transmission tests.(3)Establish a mathematical model of the control system,designing a PD steering controller and testing its system performance.The test data shows that the steering performance of the same system under different steering resistance conditions cannot achieve the same effect.Proposed by removing the dead-zone signal,linear fitting,linear stretching calibration method,the control voltage U and the steering speed W obtained under different conditions were calibrated by MATLAB through a first-order,quadratic function,and then test the system performance after calibration.The test shows that the same control system can be calibrated in three different steering resistances to make the steering performance basically consistent.(4)The program design of the host computer control system based on C++ language is completed,and the man-machine interaction operation interface is provided.The upper computer can configure the sensor data port and transmission rate.Through the configuration of the completed steering angle data displayed in real time in the software interface,the user can calibrate the current environment through the calibration function.In the host computer program,the user can input the steering angle or directly input the control voltage according to the need,and can also switch the manual or automatic mode in real time through the hand/automatic switch.(5)Test the system response signal in different environments through the system's overall performance test.By entering the step signal,the system has a steady-state error of 0.410 and an overshoot of 1.82° at an amplitude of 10°,The steady-state error at an amplitude of 200 is 0.32° and the overshoot is 1.53.When the amplitude is-10°,the steady-state error is 0.21°,the overshoot is 2.13°,the amplitude is-0.45° and the overshoot is 1.87°.The system basically meets the control requirements.By inputting the sine signal,the average delay time in the three resistance environments was 0.68s,0.71s,and 0.72s respectively,and the steady-state errors were 0.73°,1.06°,and 1.13°. |
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