Research On The Control System Of Automatic Gripper-type Pick Up Plug Seedlings Mechanism

Now the domestic research for the plug seedling transplanting technology is still in the experimentalstage. The transplanting precision, reliability and intelligent degree can’t meet the high efficiencyrequirements. And the level of the pick-up plug seedlings mechanism’s ability will directly affects the rateand quality of transplanter. Compared with the problems of manual transplanter and semi-automatictransplanter, in the paper, the automatic control system on a new kind of gripper-type pick-up plugseedlings mechanism is designed.(1) Given the research object, it analyzed the mechanism’s entire action sequence of pick-up seedlingand the field work environment. According to the whole movement of this apparatus, three power drivesystem were equipped. The dynamic system of conveying seedling adopted stepper motor to drive. And thelatter two chose pneumatic control as the drive mode.(2) In view of the importance of accurate positioning about the key movement in automatic picking upseedling process, the method of S-shaped speed curve was proposed to realize the speed control of steppingmotor. The electro-pneumatic proportional pressure valve was introduced in the paper for solving thepositioning accuracy of cylinders. The transfer function of the control cylinder system was establishedbased on the adaptive PID controller, through selecting the component and establishing the mathematicalmodel about the servo system. Then the simulation experiment of the adaptive PID positioning controllerwas carried on in the Simulink. The results about the response curves of unit step and sine signal shows thatthe adaptive PID control algorithm can satisfy the positioning requirement of picking up seedling apparatus,and in the meantime, improve the system anti-interference ability, which guarantees the operation of thepicking up seedling mechanism.(3) STC89C52RC MCU was used as the core controller of the picking up seedlings mechanism’scontrol system. The hardware circuit part, on the basis of modularized design, was designed. Thenaccording to each part of the modules, it completes components selection, circuit design and pin assignment.The hardware’s anti-interference ability is improved by the measures of shielding, grounding and so on.Then PCB circuit board and its wiring were designed reasonably.(4) C51programming language was used to develop the software program of the picking up seedlingsmechanism’s control system. By using the modularized design method which was based on the hardwaremodules, the software program was divided into three independent modules: the control output programmodule, the signal acquisition program module and the human-computer interaction program module.Finally the complete control system software consists of the three modules and a main program. Thesoftware’s anti-interference ability is improved by the techniques such as software redundancy and softwaretrap.