基于气动下压力控制的高速轻型免耕播种机播深调控系统设计与试验

Design and Experiment of Sowing Depth Regulation System for High-speed Lightweight No-till Planter Based on Pneumatic Downforce Control

摘要:

针对常规播种机高速作业时播深稳定性差，而装配基于仿形轮下压力传感式播深调控系统灵敏度低等问题，本文设计了一种基于气动下压力控制的高速轻型免耕播种机播深调控系统，以提高其高速播种时作业质量。系统主要包括：监测装置、决策控制系统、播深调控执行机构和保护装置。监测装置利用平行四杆仿形机构角度传感器、仿形镇压轮薄膜压力传感器以及播种机姿态传感器协同实现对播深实时监测；决策控制系统处理传感器数据，通过电磁阀和电气比例阀控制空气弹簧内部气压，保证执行机构输出作用力实时调控。为提高播深调控系统执行机构输出作用力的精确性，建立播深调控系统空气弹簧输出作用力与下压力关系模型，该模型通过薄膜压力传感器监测到的仿形镇压轮下压力变化实时改变空气弹簧输出作用力，模型决定系数R2为0.9959。进行了高速轻型免耕播种机播深调控系统阶跃响应台架试验，试验结果表明：当压力为0.1～0.6MPa时，系统最大超调量为6.40%，平均响应时间为0.3s，平均稳态误差为0.0047MPa，平均稳态值标准差为0.0027MPa，平均变异系数为0.93%。以平行四杆仿形弹簧式播深控制系统为对照组进行了田间性能对比试验，结果表明，在高速作业条件（14~16km/h）下，加装该播深调控系统轻型免耕播种机平均播种深度合格率为81%，相比于机械弹簧式下压力调控方式（56%）提升4464%；播种深度标准差平均值为4.87mm，变异系数平均值为14.08%，相比于机械弹簧调节方式，分别降低21.52%、29.35%。研究结果为高速轻型免耕播种机播深稳定性提升提供了理论参考。

Abstract:

Aiming at the problems of poor stability of sowing depth in the high-speed operation of conventional planter and low sensitivity of the assembly of profiled wheelbased under-pressure sensing sowing depth regulation system, a high-speed lightweight no-till planter sowing depth regulation system was designed based on pneumatic under-pressure control to improve the quality of its high-speed sowing operation. The designed system mainly included monitoring device, decision control system, sowing depth control actuator and protection device. The monitoring device utilized the angle sensor of the parallel four-bar profiling mechanism, the film pressure sensor of the profiling pressure wheel and the attitude sensor of the planter to realize the real-time monitoring of the sowing depth;the decision-making control system processed the sensor data and controlled the internal air pressure of the air spring through the solenoid valve and the electrical proportional valve to ensure that the actuator’s output force was regulated in real time. In order to improve the accuracy of the output force of the actuator of the sowing depth control system, a model of the relationship between the output force of the air spring of the sowing depth control system and the lower pressure was established, which changed the output force of the air spring in real time through the change of the pressure under the imitation suppressor wheel monitored by the thin-film pressure sensor, and the model coefficient of determination R2 was 0.9959. A step response test was carried out for the step response of the sowing depth control system of the high-speed and light no-tillage planter. Tests were conducted, and the results showed that the maximum overshoot of the system was 6.40%, the average response time was 0.3s, the average steady state error was 0.0047MPa, the average standard deviation of the steady state value was 0.0027MPa, and the average coefficient of variation was 0.93% for pressures ranging from 0.1MPa to 0.6MPa. A comparative field performance test was conducted with the parallel four-bar profiling spring-type depth control system as the control group, and the results showed that under high-speed operating conditions (14~16km/h), the average seeding depth qualification rate of the light-duty no-till planter retrofitted with this seeding depth control system was 81%, which was 44.64% higher than that of the mechanical spring-type downward pressure control mode (56%);the standard deviation of the sowing depth was an average of 4.87mm, and the coefficient of variation averaged 14.08%, compared with the mechanical spring-loaded regulation method, which were reduced by 21.52% and 29.35%, respectively. The research results can provide theoretical reference for the improvement of sowing depth stability of high-speed lightweight no-till planter.