Authors

Abstract

To address issues related to fertilization accuracy and uniformity under field conditions affected by terrain undulations and load fluctuations, an electric precision fertilization control system based on a Siemens S7-200 SMART PLC was developed. The system employs a stepper motor as the actuator and incorporates an incremental encoder with 2,000 pulses per revolution to provide closed-loop speed feedback. A PID parameter optimization method based on differential evolution (DE) is proposed, which performs global optimization using fitness functions defined by tracking error and dynamic performance. Comparative simulations of DE-PID and conventional PID were conducted in MATLAB, followed by field experiments in Dongying City, Shandong Province. The results show that, under conventional PID control, the maximum relative error, average relative error, and coefficient of variation were 4.2%, 3.68%, and 0.36%, respectively, whereas under DE-PID control, these values decreased to 3.2%, 2.92%, and 0.23%, respectively. These findings indicate that the DE-PID strategy effectively improves fertilization accuracy and uniformity, providing a reference for the precise control of external-grooved wheel-type fertilization equipment.

Abstract in Chinese

针对外槽轮式施肥机在田间作业中易受地面振动、肥料流动性变化及负载波动影响，导致施肥误差增大和均匀性下降的问题，本文设计了一套基于西门子 S7-200 SMART 的电驱精准施肥控制系统。系统采用步进电机驱动槽轮转动，并在电机轴端安装 2000 脉冲/转增量式编码器，构建转速闭环反馈；结合 PLC 100 ms 采样周期，实现“设定—测量—控制—执行”的闭环调节。为提高复杂工况下 PID 参数整定的适应性，提出基于Differential Evolution算法的 PID 参数优化方法，将 Kp，Ki，Kd作为优化变量，构建综合适应度函数，实现参数全局寻优。基于两相混合式步进电机等效模型建立控制对象传递函数，并在 Matlab 平台开展 DE-PID 与传统 PID 的仿真对比。进一步在山东省东营市农高区开展田间试验，采用 5 m×5 m网格法评价单位面积施肥量误差与施肥均匀性。结果表明，传统 PID 控制下最大相对误差为 4.2%，平均相对误差为 3.68%，变异系数为 0.36%；DE-PID 控制下分别为 3.2%、2.92% 和 0.23%。说明 DE-PID 控制策略能够有效提高施肥精度与均匀性，为外槽轮式施肥装备的精准控制提供了参考。