Development of control system for cotton picking test bench based on fuzzy PID control

Abstract: The quality of cotton harvesting performance has a direct impact on the technical index such as net production rate of cotton, loss rate of hit cotton and impurity rate. At the same time, field cotton picking test parameters are important basis for measuring cotton picking performance. In order to study and develop the cotton picking device, the cotton picking experiment must be carried out by using the experimental device. A control system of cotton picking test bench was designed in this paper. PLC (programmable logic controller) was used as the processor of the system and HMI (human-machine interface) was designed based on LabVIEW, which realized the automatic start-stop of the cotton picking test bench, and the picking performance parameters could be manual adjustment on the human-computer interface. According to the design requirements, the corresponding network programs included the main program, motor speed control subroutine, data acquisition and processing subroutine, serial communication subroutine, data storage subroutine and so on. The sub-program of motor speed control included the start and stop of picking motor, conveyor belt motor and fan motor. The subroutine of data acquisition and processing was used to collect the torque and speed of the picking device and the conveyor belt, the temperature and humidity of the picking environment. Serial communication subroutine was used to develop the communication program with PLC based on the standard of VISA instrument programming I/O API in LabVIEW. The data storage was used to collect the datas and save it to the hard disk for subsequent data analysis after processing. The control system was composed of 3 parts: motor control system, data acquisition system and upper computer. The motor control system consists of frequency converter, picking motor, conveyor motor, fan motor and PLC controller. According to the motor speed and fuzzy PID control strategy, the rotational speed of the plucking drum, the speed of conveyor belt and the speed of the fan were accurately controlled. The data acquisition system was composed of USB-2000 acquisition card, temperature and humidity sensor, torque speed sensor, F/V converter and signal conditioning circuit. Before the data collection system working, the parameters of USB-2000 card, communication channel and data acquisition frequency should be selected first. The output datas of torque speed sensor and temperature and humidity sensor were recorded in a high-speed and accurate way. At the same time, the torque speed sensor was used to measure the real-time speed of the motor, and on this basis, the fuzzy PID control of the motor was carried out. The upper computer system was made up of IPC and measurement and control software, the human-computer interaction interface developed by LabVIEW displayed and analyzed data in real time. The test results show that the picking speed and speed of conveyor belt could be continuously adjusted within 0～2 m/s, the temperature and picking torque signals could be collected quickly from 0~5 kHz and 10~15 kHz, and could carry on the data collection and record. In order to verify the reliability and accuracy of the measurement and control system, the picking experiment of cotton (Xin Luzao 26) was carried out in this paper. The moisture content of cotton was 25.1%, the plant spacing was 300 mm and the row spacing was 600 mm. When the conveyor speed was 1.67 m/s and the picking drum speed was 120 r/min, the cotton picking net rate of the cotton picking test bench was 94.3%, the impurity rate was less than 14.1%, the ground cotton was less than 1.1%, and the cotton picking quality was meet the requirements of the national cotton picker operating procedures. The quality of cotton picking conform the requirements of the national cotton picking machine. It provided a theoretical basis and technical support for the optimization of performance parameters of picking head and the localization of cotton picking and harvesting equipment.