Research On The Control System Of Automatic Pick-up Plug Seedlings Mechanism

Planting operation is an important part in agricultural production, and adoptting plug seedlingtransplanting technology and developing automatic plug seedling transplanters have important significancein reducing the labor intensity, liberating the labor productive forces and improving the efficiency oftransplanting. At present, the domestic research has not been involved in the automatic plug seedlingtransplanters which are suitable for field operation. At the same time, the greenhouse intelligent machinesin the study is still in the experimental stage, and there are the following problems as a whole in theircontrol system: low location accuracy, poor flexibility and reliability, unstable control performance, lowintelligence and operation efficiency, and so on. And automatic pick-up plug seedlings mechanism is one ofthe key components of full-automatic field transplanter, so this paper studied the control system of a newkind of automatic pick-up plug seedlings mechanism.(1) Through the analysis of mechanical structure characteristics of this new mechanism,corresponding control requirements were put forward. Then the dynamical systems of the mechanism wasselected, and the control scheme of the dynamical systems was designed. Then it was proposed to realisethe speed control of stepping moter with the method of S-shaped speed curve after analyzing the controlway of the displacement, the direction and the speed of stepping moter. In addition, the control scheme ofpneumatic transmission system and its pneumatic circuit was designed.(2) Because the stepping location control of potted trays conveying system plays an important in theentire control system of this mechanism, this paper analysed and calculated the location accuracyrequirement in conveying potted trays in details, and the control accuracy of the potted trays conveyingsystem under simple closed loop stepping location control was worked out theoretically. Then this paperstated the limitations of stepping location control system under simple closed loop control, fixed parameterPID control or fuzzy control, and adaptive Fuzzy-PID control algorithm was proposed to be used to achievethe stepping location control. In this paper, aptive Fuzzy-PID controller was designed, the modeling andsimulation analysis in the Matlab were carried on as well as the system debugging experiment. The resultsshow that the adaptive Fuzy-PID control algorithm that applied to fulfill the location control can satisfy thelocation requirement of conveying potted trays, and in the meantime, the anti-jamming performance andthe operation stability of the system get improved, which ensures the efficient operation of this automaticpick-up plug seedlings mechanism and makes it suitable to complex field transplanting operationenvironment.(3) The hardware circuit of the pick-up plug seedlings mechanism’s control system were designed. Inthe design of the hardware, it used STC89C54RD+microcontroller as the controller, and by usingmodularized design method, control circuit is divided into the following several modules based on thesystem’s hardware functionality: processor module, power module, signal acquisition module, control quantity output module and human-computer interaction. The parts selection, the control pin assignmentand the circuit design of every module was completed, and PCB circuit board was designed. On the whole,the design of hardware circuit is simple and reliable, and at the same time, the PCB production isreasonable, practical and anti-jamming.(4) The software program of the pick-up plug seedlings mechanism’s control system were developed.In the design of the software, it used C51language to write the program, Keil uVision2integrateddevelopment environment to develop the software and STC-ISP program burning software to download theprogram. By using the modularized design method which was based on the hardware modules to developthe program, the software system consisted of signal acquisition program module, control quantityoutput program module, human-computer interation program module and main program. In the paper, thecontrol process of every part was analyzed, and the corresponding program flowchart was designed indetails. The design of software program is simple and reliable.