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. However, due to the load increases of the manipulator, there will be great 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 was 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.