果园有机肥深施机分层变量排肥控制系统设计与试验

果园不同深度的土壤养分不同,果树根系分层吸肥能力不同,有机肥分层变量深施可以解决传统施肥存在的养分分布不均和肥料利用率低等问题。针对有机肥分层变量深施的排肥控制问题,本文设计了排肥控制系统,可以根据用户设置的各层理论排肥量和作业速度,实时计算液压马达的理论转速,并采用PID算法控制比例流量阀开度,调节马达转速驱动螺旋输送器排肥,实现分层变量排肥。将AMESim中建立的液压系统模型与在Matlab/Simulink中建立的控制模型进行联合仿真,整定PID参数。液压马达转速调节性能试验中最大超调量为14r/min,达到稳定转速的时间最大为6s,控制性能较好,表明通过AMESim-Matlab/Simulink联合仿真,能够快速便捷地整定PID参数,结果准确可靠。排肥控制性能试验中排肥量相对误差最大6.20%,变异系数最大8.69%,排肥量准确性和均匀性均达到要求。设计的控制系统具有较好的性能,能为果园有机肥分层变量深施提供技术支撑。

Design and Test of Layered Variable Rate Fertilizer Discharge Control System for Organic Fertilizer Deep Applicator

Due to the different soil nutrients in different depths of orchard, and the ability of fruit tree roots to absorb fertilizer is different, the layered variable deep application of organic fertilizer can solve the problems of uneven distribution of nutrients and low utilization rate of fertilizer in traditional fertilization. In view of the electro-hydraulic control of layered variable rate fertilizer discharge, a fertilizer discharge control system was designed, which can calculate the theoretical speed of hydraulic motor in real time according to the theoretical fertilizer amount of each layer set by the user and the forward speed of the unit. PID algorithm was used to control the opening of the proportional flow valve, and the motor speed was adjusted to drive the screw conveyor to discharge fertilizer, so as to realize the layered variable rate fertilizer discharge. PID algorithm usually needed to adjust the parameters such as proportion, integral, differential coefficient and sampling time to obtain better control performance. Matlab/Simulink is a powerful simulation software, which can establish the control system model and carry out simulation. It can quickly and conveniently adjust PID parameters. But it is necessary to establish the mathematical model of the controlled object. It is difficult to establish an accurate mathematical model for the valve controlled motor speed control system because of its nonlinearity, time-varying and hysteresis. AMESim is a multi-disciplinary complex system modeling and simulation platform, especially suitable for hydraulic system simulation and analysis. The hydraulic system model was built in AMESim, the control model was built in Matlab/Simulink, and the joint simulation results were more accurate and reliable. The hydraulic system mainly included gear pump, relief valve, differential pressure reducing valve, proportional throttle valve and hydraulic motor. According to the sample of hydraulic components, the hydraulic system model was completed in AMESim, the parameters of each component was set, the rotating load was set according to the actual working environment, the speed sensor and coupling interface was added. The PID control simulation model was established in Matlab/Simulink, and the parameters were adjusted through joint simulation. When the values of proportional, integral and differential coefficients were 0.005, 0.05 and 0, respectively, and the sampling time was 0.5s, the control performance was the best. The adjusted algorithm was used in the bench test of speed regulation performance and fertilizer discharge performance. The regulation performance test results showed that the speed regulation performance was good, the maximum overshoot was 14r/min and the maximum time to reach the stable speed was 6s. The simulation results were accurate and reliable, AMESim-Matlab/Simulink joint simulation can quickly and conveniently research the layered variable rate fertilizer control algorithm, and adjust algorithm parameters. The fertilizer discharge performance test results showed that the accuracy and uniformity of fertilizer discharge can meet the requirements, the maximum relative error of fertilizer discharge was 6.20%, the maximum coefficient of variation was 8.69%. The control system had better control performance, and it can provide technical support for layered variable rate deep application of organic fertilizer in orchard.