Adaptive fuzzy-PID control of accurate orientation for auto-detect seedling supply device

Abstract: There is more serious seedling leakage phenomenon for duckbill-type automatic transplanter. When the seedlings in plug tray are lacked or the picking seedling machinery fails to pick seedling or the trajectory is inaccurate, throwing seedling to duckbill planter will cause cavity phenomenon on the surface of soil. Current research has focused on seedlings detection out of plug tray, aiming to provide guidelines in picking seedling mechanism's work regularity. However, it cannot resolve the problems that picking seedling needle clamp fails to grip seedlings into duckbill planter, which leads to seedling trajectory deviation. In this paper, a new auto-detect seedlings device suitable for automatic transplanting machine was designed in order to solve the problems above. Seedling positioning detection control system was analyzed and studied systematically. Different from general control system of transplanting machine, which was commonly simple closed-loop control, a method was developed, which adopted the self-adaptation fuzzy-PID (proportion, integral, derivative) control algorithm. It could control stepping motor angle speed firmly, improve response speed to angle speed, and control seedlings positioning accurately on automatic detection system. The mathematical model of the stepping motor velocity control transfer function was developed, and the adaptive fuzzy-PID controller and the fuzzy rules were designed. The mathematical model of angular speed control of stepping motor was established through MATLAB Simulink module based on fuzzy-PID controller of stepper motor system. The control model took step signal as excitation signal, and the adaptive fuzzy-PID control and PID control simulation experiments showed that when the system exerted incentive through step signal, the response time of PID control was 7 s, the system response was slow, and the shock with a super adjustable volume of 0.1 appeared. Through adjusting PID controller parameter and increasing proportion coefficient, the system response time was shortened to 2.2 s, the system response speed obviously sped up, and the shock did not appear. But, PID controller parameter adjustment was offline, and the system load mutation or tough working environment for seedlings detection system would be prone to all kinds of interference. And it may not quickly be adjusted to the steady state values to fill the gaps with seedlings detection system. Response time of adapted fuzzy-PID was 0.12 s and the stepping motor system quickly reached the steady-state value of the step response. It showed that the angular velocity control of stepping motor was stable and the angle change was fast, which could meet the positioning requirements of seedlings conveying. When the auto-detect seedlings device load mutated or the expected value of stepping motor speed changed, the stepping motor could fast response, and the seedlings could fill the gaps timely and be planted normally, at the same time the seedling which will fill the gap will be conveyed to the required position. The experiment result of automatically filling the gaps with seedlings showed that the actual seeding frequency of 2ZXM-2 automatic membrane transplanting machine was 40-60 seedlings/min. When seeding frequency was more than 60 seedlings/min, there existed matching error between seedlings manipulator and plant duckbill. It could increase the leakage rate of seedlings. When the frequency was lower than 40 seedlings/min, the planting efficiency was low and at the same time it could make planting distance of transplanting seedling larger. The seeding frequency was 40, 50 and 60 seedlings/min in test, and the success rate of filling the gaps with seedlings was 100%, 100%, and 95.8%, respectively. As long as the optical fiber sensor detected slight signal, the stepping motor responded quickly based on adaptive fuzzy-PID control system, and the control system of filling the gaps with seedlings could automatically fill the gaps with seedlings accurately and timely. This provides a new method to solve the problem of seedlings leakage of automatic transplanting machine in field.