Authors

Abstract

To address the low control precision caused by the high nonlinearity and pure time-delay of hydraulic pipelines in variable-rate soybean foliar fertilization, this study developed an automatic variable-rate control system for boom sprayers. Based on Fluent dynamic mesh simulations, the throttling characteristics of the electric control valve were revealed, and a second-order transfer function model with pure time-delay was accurately identified for the actuator. To overcome the reliance of conventional fuzzy controllers on expert experience, an improved Sparrow Search Algorithm-optimized Fuzzy PID (ISSA-Fuzzy PID) control strategy was proposed. By integrating optimized population initialization and adaptive global search, this improvement mechanism effectively avoids premature convergence during dynamic parameter tuning. Simulation results indicate that the proposed algorithm compresses the rise time to 0.35 s, limits the overshoot to within 20%, and achieves steady-state convergence within 1.0 s. Bench tests verified that the average detection errors for system flow rate and pressure were merely 2.14% and 2.34%, respectively. Under the working pressure of 250–350 kPa, dynamic pressure regulations were completed stably within 1.9 s without significant overshoot, exhibiting improved regulation precision under high-flow conditions. This research effectively overcomes the lag bottleneck of actuating mechanisms, providing an integrated control solution with high dynamic response and steady-state precision for variable-rate applications. Practically, this optimized system ensures rapid dosage correction and pressure stability, providing technical support for improving the operational timeliness and fertilizer-use efficiency of field spraying operations.

Abstract in Chinese

针对大豆叶面肥变量喷施中液压管路高非线性与纯滞后导致的控制精度低等问题，本文开发了一套喷杆喷雾机变量自动控制系统。基于 Fluent 动网格仿真揭示了电控阀节流特性，并精确辨识出执行机构的二阶带纯滞后传递函数模型。为克服模糊控制器高度依赖专家经验的局限，提出改进麻雀搜索算法优化模糊 PID（ISSA-Fuzzy PID）控制策略。该改进机制通过融合优化的种群初始化与自适应全局搜索策略，有效避免了动态参数寻优过程中的早熟收敛问题。仿真表明，该算法将上升时间缩短至 0.35 s，超调量控制在 20% 以内，并在 1.0 s 内实现稳态收敛。台架试验验证：系统流量与压力的平均误差仅为 2.14% 和 2.34%；在 250~350 kPa 工作压力下，动态调节可在 1.9 s 内无显著超调地切入稳态，且大流量工况下调节精度更优。本研究有效突破了执行机构的滞后瓶颈，为高精度变量施药提供了兼具高动态响应与稳态精度的集成控制方案。在实际应用中，该系统能够确保施药量的快速修正与压力稳定，从而显著提升田间喷施作业的响应及时性与肥料利用率。