葡萄株间除草机精准避障控制系统优化设计与试验

现有篱架式栽培葡萄双边作业株间自动避障除草机避障系统采用开关控制避障动作，由于避障行程固定，无法根据障碍物位置精确控制避障动作行程，导致除草效果不佳。针对上述问题，该研究在先前研究的基础上，依据仿形控制原理对避障控制系统进行优化，设计一种由避障信号采集部分、程序控制部分、液压执行部分、避障监测反馈部分等组成的精准避障控制系统。基于精准避障工作要求，确定避障动作闭环控制方案；优化液压回路结构，液压与电控结合实现精准避障控制；对精准避障控制程序进行静态标定和PID参数整定；利用Recurdyn对障碍物呈直线排列状态下除草机的精准避障作业进行模拟仿真，并通过分析除草刀盘运动轨迹选取较优除草刀盘转速；以机器作业速度为试验因素，除草作业覆盖率和果树损伤率为评价指标进行田间试验。试验结果表明，当机器作业速度为380 mm/s时，除草作业覆盖率与作业效率综合效果最佳，试验得到平均除草作业覆盖率为93.97%，较先前研究提高4.39%，果树损伤率为1.92%，除草机可良好实现避障除草作业。该研究可为果园株间除草机的进一步优化提供参考。

Optimized design and experiment of the precise obstacle avoidance control system for a grape interplant weeding machine

Weeds have generally seized the growth resources of grapes, resulting in the aggravation of plant diseases and insect pests for the reduced grape quality, particularly the yield reduced by 10% to 20%. Therefore, weed removal is one of the most important steps in the vineyard. The current obstacle avoidance system in an automatic obstacle avoidance weeder can be operated bilaterally in the hedge-frame grape cultivation. Most obstacle avoidance action was controlled by the switches, where the obstacle avoidance stroke was fixed. However, a relatively low effect of weeding often occurred, due mainly to the obstacle avoidance action stroke cannot be accurately controlled, according to the position of obstacles. In this study, a highly precise control system of obstacle avoidance was optimized to design in an interplant weeding machine, according to the principle of copying control. The specific system consisted of the signal acquisition of obstacle avoidance, program control, hydraulic actuator, and the obstacle avoidance monitoring feedback part. A closed-loop control system was also composed of signal acquisition, hydraulic actuator, and monitoring feedback part, according to the requirements of precise obstacle avoidance. The signal acquisition of obstacle avoidance was run to collect the angle change of signals ?β in real time when the weeding cutter moved to the position close to the obstacle. A voltage signal was then converted to transmit for the control system. The theoretical action stroke of the hydraulic actuator was calculated by the control system, where the signal was converted and output to the hydraulic actuator in the θ Angular variation ?β size. At the same time, the displacement sensor of obstacle avoidance monitoring feedback transmitted the actual action stroke to the control system for the precise adjustment of the action stroke of the hydraulic cylinder. The structure of the hydraulic circuit was optimized to realize the precise control of obstacle avoidance under the combination of hydraulic and electronic control. Static calibration was carried out for the precise control program of obstacle avoidance. Specifically, the effective stroke range was 5-145 mm for the calibration hydraulic cylinder and the feedback displacement sensor, and the effective stroke of the signal acquisition displacement sensor was 0-70 mm. PID parameters were set in the control program at the speed of 440 mm/s, where the optimal PID parameters were finally determined as P=0.034 3; I=127.78; D=0. The target center distance curve of the hydraulic cylinder was well fitted to the actual center distance curve, indicating an accurate, quick and stable implementation of the obstacle avoidance process. Recurdyn was used to simulate the precise obstacle avoidance operation in a weeding machine under the condition of straight obstacles. The coverage rate of the weeding operation was calculated to analyze the movement track of the weeding cutter disc. An optimal speed of the weeding cutter disc was selected as 200 r/min. Taking the operation speed of the machine as the experimental factor, the weeding coverage rate, and the damage rate of the fruit tree as evaluation indexes, field tests were carried out in the Scientific Research Test Base of China Agricultural University Zhuozhou, Hebei Province in June 2021. The results were as follows: The average coverage rate of weeding was 94.82%, 94.36%, 93.97%, and 92.60% at the machine speed of 260, 320, 380, and 440 mm/s, and the fruit tree damage rate was 1.67%, 1.78%, 1.92%, and 2.08%, respectively. The best comprehensive effect of weeding coverage rate and the highest operational efficiency was achieved at the operation speed of 380 mm/s. The average weeding operation coverage rate was 93.97% in the test, and the machine weeding operation coverage rate under the original obstacle avoidance control system was about 90.02%. The coverage rate of weeding operation increased by 4.39% at the same machine operation speed. Consequently, there was an excellent performance obstacle avoidance weeding in the highly precise control system of obstacle avoidance. This finding can provide a sound reference for further optimization of the interplant weeding machines in the modern orchards.