Design And Experiment Of Key Components Of Automatic Transplanter For Chili Plug Seedlings

Chili is one of the main vegetable crops in our country.As one of the main vegetable crops in China,the planting area and yield of chili are increasing year by year,but the comprehensive mechanization level of manufacturing is less than 50%,and the weakness of planting mechanization is particularly significant.It is urgent to improve the mechanization level of chili planting.The cultivation and transplanting of standardized plug seedlings can improve the yield and quality,which has gradually become the main way of chili planting.Compared with semi-automatic transplanting machine,the full-automatic transplanting machine of chili seedlings has the function of picking up seedlings and putting down seedlings,which can greatly reduce labor intensity and improve manufacturing efficiency.It is the inevitable trend of transplanting technology development.In this paper,on the basis of analyzing the current situation of dryland transplanter and its seedling picking up device at home and abroad,aiming at the key problems of low success rate of picking up seedlings due to damage of the pot in the process of picking up seedlings by the automatic transplanter,the clamping pot type seedling picking up device and the ejecting pot-clamping stem type seedling picking up device were designed respectively,and their working mechanism was studied and the schemes were compared.Automatic transplanter was designed.The specific research contents and conclusions are as follows:（1）Experimental on biological and mechanical characteristics of chili plug seedlingsTaking the stem and pot of chili plug seedlings as the test object,the biological and mechanical properties were studied to provide theoretical basis for the structural design of key components of automatic transplanter.The morphological characteristics of chili plug seedling were measured,including total seedling height,stem length,stem diameter and shape parameters of pot,etc.The stem characteristic test results showed that the best place to hold the stem was close to the root.The design value of the holding force should be lower than the yield force of the stem 34.81 N,the design value of the compression displacement should not be greater than 50%of stem diameter,and the deformation should not be higher than 1.15 mm.Under these conditions,the damage caused in the process of picking seedlings from the plug could be reduced and the quality of transplanting could be improved.The results of clamping stem type pull-out tray test showed that it was easy to pull out seedlings from tray,and the maximum pull-out force was 3.54 N～5.38 N.The results of the pot characteristic test show that the water content range of put is 40%～75%,and it is feasible to control the water content at low（40%～50%）,medium（51%～64%）and high（65%～75%）levels by the amount of watering.The compression test of pot was carried out and the results showed that the compression process of pot is roughly divided into five stages.The hand force during the holding or topping of pot should be controlled at the initial linear stage.The calculated elastic modulus E_m of pot is 3.49E-2 MPa,the deformation at the yield point of pot is 10.87 mm,and the pressure resistance at this time is 12.33 N.The pot substrate loss rate increased significantly with the increase of seedling fall height,and the design value of seedling height should be reduced as far as possible,so that the fall height is controlled below 300mm.（2）Research on open-and-close clamping pot type seedling picking up with four fingers technology and design of deviceWith the aim to solve the problems of plug seedlings being damaged and the low success rate in the process of picking up seedlings,an open-and-close seedling picking manipulator with four fingers was designed.The clamping scheme with quadrangle inserting while clamping was designed in order to reduce the disturbance and injury of pot substrate soil.The working principle of manipulator was expounded,and a mathematical model of the mechanism movement was established.The force transmission of the mechanism and force between finger and pot was analyzed,and the constraint condition of optimum force transmission efficiency and low damage when picking up seedlings was analyzed.A set of optimal parameters and the trace curve of the finger end point were obtained.The calculation results show that when the cylinder extension length h is pushed from 32.35 mm to 28.75 mm,the corresponding manipulator moves down45mm,and the composite movement of fingers clamping while inserting can complete the action of picking up seedlings better.Kinematics parameters were analyzed and verified by ADAMS software.The simulation result proved the end point trajectory obtained by motion simulation was basically consistent with that obtained by theoretical calculation.Velocity and acceleration curves of each mechanism component were obtained,and the result proved the velocity and acceleration of the tip of the finger changed greatly,and the inertia impact was large;the inertia force helped to clamp the pot.（3）Research on ejecting pot-clamping stem type seedling picking up technology and design of deviceFor the pot clamping type seedling picking mechanism,when the end of grippers are inserted into the pot to pick up seedlings,the pot is broken due to the weak twining force between roots and soil;and for the stem pulling type seedling picking mechanism,when the seedling claws clip and pull the stem,success rate of seedling picking is low due to the weak adhesion force between the pot and the plug.In order to solve the above problems,a technical method of picking up seedlings with ejecting pot-clamping stem were proposed.The route of picking up seedlings was designed,and the structure and working principle of the device were described,and device trial manufacture and test optimization were carried out.The stress models of pot body and stem during the three movements of ejecting,clamping and throwing were established.Then the key parameters of the seedling picking and throwing device were designed.Through calculation and analysis,the design values of the terminal parameters of ejecting pot are as follows:the height of the ejecting pot ranges from 10 mm to 20 mm,the diameter of the top rod is 6mm,and the moving displacement of the top rod is 40 mm.The design values of the parameters of the seeding mechanism are as follows:the normally open spacing of the inner end of the cylinder of the clamping stem is 34 mm,the normally closed spacing is20 mm,the thickness of the clamping piece is 7.5 mm,the thickness of the clamping wall is 2 mm,the height of the clamping is 20 mm,and the width of the clamping clip is 10mm.The seedling height was 220 mm,240 mm and 260 mm,the time of falling seedling was 0.21 s,0.22 s and 0.23 s,and the horizontal distance was 207.3 mm,152.5 mm and100.05 mm,respectively.The installation position of the seedling cup was designed according to the three sets of data.The optimization analysis and demonstration of two kinds of picking up types were carried out,and the final choice was ejecting pot-clamping stem type.（4）Design of ejecting pot-clamping stem type automatic transplanterThe design and trial manufacture of automatic transplanter were carried out based on the method of ejecting pot-clamping stem type seedling picking up.The design requirements and technical parameters of the whole machine were put forward,the structure and working principle of the whole machine were expounded,and structure design and control system design of the vertical trays feeding device,pressure tray device,seedling tray conveying and recovery device and other components were carried out,and to ensure that the assembly of each component without interference,and the coordination of each action,complete the automatic transplanting work.The whole automatic control system design,including drive system,control system hardware and software design.The mechanical transmission system and pneumatic system of the transplanter were designed and calculated.The results showed that the average gas consumption was 30.286 L·min^-1when transplanting at a frequency of 60 plants·min^-1.The main controller is STM32F4071GT6 MCU development board,and motor drive module is composed of 5sets of stepper motor and 2 sets of servo motor.The PWM pulse output of the main controller controls on and off of the optical coupling isolation relay,so as to control extend to retract or open to close of each cylinder;visual man-machine interaction module establishes the information exchange between the users of the transplanting machine and the software,system and other objects.The timing sequence and program of transplanting work were designed to complete a series of automatic operations,such as tray feeding,seedling tray conveying,seedling picking up and recovery.（5）Bench test of operating performance of automatic transplanter was carried outStatic bench tests were carried out on plug seedling transplanter,including the whole machine debugging,plug seedling conveying performance test,parameter calibration of transplanter control system,ejecting pot test,clamping pot type and ejecting pot-clamping stem type seedling picking up test.The test results showed that the accuracy of X and Y direction moving position of the seedling tray reached more than 95%,which met the requirements.Pot moisture content,seedling pick-up frequency,and finger material were used as experimental factors for the clamping stem type seedling pick-up test for“Zhongnong Luheng line pepper 363”plug seedlings..The results showed that pot moisture content and seedling pick-up frequency both had significant effects on the rate of successful seedling pick-up.The optimum level was that when moisture content was45%,frequency of picking seedlings was 20 plants·min^-1,and clamping finger material was carbon steel;the damage rate of the pot body was 1.98%,and the success rate of picking seedlings was 98%.First,ejecting pot-clamping stem type seedling picking up experiment was carried out with the simulated seedlings.The results showed that the best effect was obtained when the height of seedlings was 220 mm,and the actual horizontal distance of seedlings was 210 mm,which met the working requirements.After ejecting pot-clamping stem type seedling picking up experiment was carried out.When seedling pick-up frequency was 60 plants·min^-1,height of seedling ejecting was 10 mm,15 mm and 20 mm,success rates of seedling picking up were 90%,94%and 96%respectively.