玉米中耕变量施肥电控液压驱动系统设计与试验

Design and Test of Electronically Controlled Hydraulic Driving System for Variable Fertilization in Maize Medium Tillage

针对玉米中耕追肥时肥料利用率低、液压驱动变量施肥转速控制效果差,以及电机驱动力不足等问题,设计了大垄双行玉米中耕变量施肥电控液压驱动系统。系统主要包括光谱传感器、车载计算机、控制系统及液压系统。电控液压系统主要由液压泵站、电磁比例阀、液压马达、编码器及移动控制器等组成。移动控制器以微控制单元为核心,通过PID控制算法输出PWM信号,驱动电磁比例阀,达到稳定控制液压马达转速目的。搭建室内台架试验台,采用MatLab对电控驱动系统PID控制进行仿真测试,以减少整定PID系数次数,提高整定效率,初步确定PID参数分别为K_(P)=4.59、K_(I)=0.469、K_(D)=0.117。室内台架试验结果表明:确定PID控制参数分别为0.73、0.47、0.40,设定转速指令为100r/min时,电控液压驱动系统的超调量为13%、响应时间为0.85s,系统等幅振荡稳定后平均转速为99.8r/min,转速偏差为0.2%,转速控制精度高。田间试验表明:电控液压驱动系统控制精度高,在不同转速下转速控制精度可达98%,均可达到稳定控制的效果,可满足玉米中耕变量施肥精准控制的要求。

Aiming at the problems of low fertilizer utilization rate,poor control effect of hydraulic variable rate fertilization speed and insufficient motor driving force in Maize mid-tillage and topdressing,an electronically controlled hydraulic driving system for variable rate fertilization in large ridge and double row maize mid-tillage was designed.The system mainly includes spectrum sensor,on-board computer,control system and hydraulic system.The electronically controlled hydraulic system consists of hydraulic pump station,electromagnetic proportional valve,hydraulic motor,encoder,mobile controller,etc.The mobile controller takes the micro-control unit as the core,outputs the PWM signal through the PID control algorithm,drives the solenoid proportional valve,and achieves the goal of stabilizing the speed of the hydraulic motor.An indoor bench test-bed was built,and the PID control of the electronic control drive system was simulated by using MATLAB to reduce the times of setting the PID coefficient and improve the setting efficiency.The parameters of the PID were initially determined as K_(P)=4.59,K_(I)=0.469 and K_(D)=0.117,respectively.The indoor bench test results show that when the PID control parameters are determined to be 0.73,0.47 and 0.40 respectively and the speed instruction is set to be 100 r/min,the overshoot of the electronically controlled hydraulic drive system is 13%,the response time is 0.85 s,and the system oscillates in equal amplitude.After stabilization,the average speed is 99.8 r/min,the speed deviation is 0.2%,and the speed control accuracy is high.Field experiments show that the control precision of the electronically controlled hydraulic drive system is high,and the speed control accuracy can reach 99.8%at different rotational speeds,which can achieve stable control effect.The system can meet the requirements of variable rate fertilization precision control in Maize mid-tillage.