番茄钵苗整排取苗手定位的模糊PID控制

为解决自动移栽机作业过程中由于机械手定位误差导致的抓取失败、伤苗及漏苗问题,实现整排取苗机械手准确快速定位,该文采用模糊PID控制算法实现自动取苗机械手的步进定位控制。根据整排取苗试验平台分析了机械手水平和竖直方向的定位精度需求,以两相混合式步进电机为对象建立步进电机角速度控制模型,设计模糊规则,建立模糊PID控制器,通过对误差及误差变化率的在线修正,来满足不同误差和误差变化率情况下的控制要求。应用MATLAB/Simulink进行系统仿真,从超调量、响应时间和稳定性指标验证了控制方法的可行性;以单位阶跃信号作为激励,分析PID和模糊PID的控制效果,结果表明:通过固定参数PID仿真分析,获得系统最优PID参数为KP=20,KI=0.2,KD=1,达到稳态所需的时间为0.285 s。在此参数下,模糊PID控制达到稳态所需时间为0.25 s,响应速度优于固定参数PID控制,系统无超调。固定参数PID和模糊PID控制加入扰动后的控制效果分析表明,模糊PID控制系统超调量为40%,达到稳态所需时间为1.34 s,均明显小于固定参数PID控制43%和1.45 s,表明模糊PID在具有扰动的环境中控制效果明显优于固定参数PID控制,步进电机系统快速响应,控制稳定。系统试验结果,模糊PID控制算法的最大误差为2.8 mm,定位平均相对误差为0.81%,定位准确度高,可以满足机械手水平定位精度要求。

Fuzzy PID control of manipulator positioning for taking the whole row seedlings of tomato plug seedlings

The planting mode of plug seedling transplanting is adopted for tomato planting in Xinjiang, the whole row seedlings taking can greatly improve the working efficiency and meet the requirements of large-scale planting and transplanting in short agricultural time. However, due to the load increases of the manipulator, there will be large friction and vibration during the movement, which cause positioning error, resulting in seedling taking failure, seedling damage and leakage, so the key to realize the automatic transplanting is to correct the displacement errors in time and positioning the manipulator accurately. In order to solve the problems of seedling taking failure, seedling damage and seedling leakage caused by the positioning error of the manipulator during the operation of the automatic transplanter, and realize the accurate and rapid positioning of the whole row seedling taking manipulator, this paper adopted the fuzzy PID control algorithm to realize the stepper positioning control of the automatic seedling taking manipulator and the accurate and fast positioning of the whole row seedling taking manipulator. Firstly, the positioning accuracy requirements of the manipulator in horizontal and vertical directions were analyzed according to the whole row seedling taking test platform. The two-phase hybrid stepper motor was taken as the object to establish the stepper motor angular velocity control model. After that the fuzzy rules and related controller were designed. Secondly, the feasibility of the PID and fuzzy PID control methods were verified from overshoot, response time and stability by MATLAB/Simulink tool, respectively. The results indicated that the optimal PID parameters were 20, 0.2 and 1, the adjusting time of the traditional fixed-parameter PID control was 0.285 s, that of the fuzzy-PID controlI was 0.25 s. The control effects of traditional fixed-parameter PID control PID and fuzzy PID control with disturbance was then analyzed. The overshoot of the fuzzy PID control system wa 40%, and the time required to reach the steady state was 1.34 s, both of which were less than that of the traditional fixed-parameter PID control 43% and 1.45 s. Bench test results showed that the maximum displacement error of the fuzzy PID control algorithm was 2.8 mm, the average relative error of positioning was 0.81%, while that of the fixed-parameter PID control algorithm were 5.5 mm and 1.23%, respectively. The proposed method realized the stepping positioning control of whole row seedlings taking manipulator, enhanced the location accuracy of the manipulator, and improved the anti-interference and the stability of the control system. The study not only provides a reference for the research and development of the control system of the automatic transplanting machine, but also provides a reference for the positioning of manipulator and the control scheme in nonlinear environment.