| As a production mode of modern agriculture,facility agriculture can achieve efficient agricultural production in a controlled environment.In recent years,it has been vigorously promoted.In order to facilitate the large-scale cultivation and management of vegetables,hole dish seedling cultivation is often used in facility agriculture.In order to meet the requirements of fine agriculture,the technique of thinning and transplanting is often used in the process of vegetable seedling cultivation,that is,vegetable seedlings are transplanted from high density to low density,so as to provide further growth conditions for the seedlings.However,at present,thinning and transplanting is mainly artificial,which is inefficient and easy to damage seedlings.Therefore,the study of automatic thinning and transplanting technology is of great significance to realize the operation automation of precise transplanting of hole disk seedlings and improve the operation efficiency of transplanting.Based on the previous studies on the pot pot seedlings of tomato,an adjustable plant spacing sparse planting and transplanting scheme was proposed in this paper.The main research contents and conclusions are as follows:(1)Study on physical characteristics of tomato pot seedlings in greenhouse.According to the agronomic requirements of sparse planting and transplanting.The physical parameters of "Luyang k9" tomato pot seedlings at different seedling ages of 15 d,20d,25 d,30d and 35 d were measured,including seedling height,seedling leaf width,stem diameter and total seedling weight.The physical parameters showed a gradually increasing trend with the growth of seedling age.The distribution of root system of tomato pot seedlings with seedling age was analyzed.With the growth of seedling age,seedling pot root system gradually developed,and it was really suitable for mechanized sparse planting and transplanting seedlings with seedling age of 20-30 days.The compressive characteristics of tomato seedling pot under different seedling age and different moisture content were studied,and the moisture content of seedling pot was divided into three levels: low,medium and high.Combined with the effect before and after seedling pot compression,it was determined that the compressive characteristics of seedling age at medium moisture content(60%)were better,which was more suitable for mechanized thinning and transplanting.This study provides a theoretical basis for the design of the adjustable plant spacing thinning and transplanting device.(2)Determine the overall plan for thinning and transplanting devices.The function and performance requirements of the thinning and transplanting device were determined.Comparing and analyzing the schemes of plant spacing adjustment mechanism and gripping end-effector of seedling extraction;According to the advantages of precise distance adjustment,simple structure and smooth operation of cylindrical CAM mechanism,it is determined as the plant distance adjustment mechanism,and the clamping type seedling picking end-effector is selected as the single-finger four-pin oblique insertion type.The end effector with adjustable plant spacing based on cylindrical CAM was determined.Cartesian coordinate arm was selected as the transplant arm scheme.Finally determine the overall scheme of thinning and transplanting device.(3)Design key components and control system of thinning and transplanting device.The structure and parameters of cylindrical CAM mechanism were designed and studied,and the contour curve of cylindrical CAM was determined as the equation curve of harmonic motion law.Based on ADAMS,the working process of cylindrical CAM mechanism with simple harmonic motion law is analyzed to verify the rationality of the scheme design.Stress analysis of cylindrical CAM mechanism in the working process,the maximum torque required for its work is determined to be 14.76 N·mm,which provides reference for motor selection.The structure and parameters of the clipped end-effector seedling picking needle were designed and studied.CT scanning technology was used to obtain the real model of seedling pot root system,so as to establish the seedling pot root-soil complex.Based on EDEM and Recur Dyn,coupling simulation experiment was conducted to study the extraction effect of seedlings with different parameters for seedling pot root-soil complex.The simulation results showed that the extraction effect of root-soil complex was better.The parameters of taking seedling needles were as follows: the seedling needle angle was 10 °～12 °,the penetrating angel was 4 °～ 6 °,and seedling needle spacing was 4 mm～8 mm.The plug tray image recognition module is designed,and the detection frame is built through the YOLO v4 algorithm to identify the holes,so as to determine the plug size and guide the work of the planting and distance changing mechanism,and the recognition accuracy can reach 97%;the control system control module and the control system are determined.The hardware model of the electrical components of each part of the device,and the flow chart of the control system is determined according to the overall plan of the device.(4)Trial production and verification test of thinning and transplanting device.According to the overall scheme of the device and the design of the mechanism and control system,the prototype was trial-produced and the control system was debugged.The parameter optimization test of the adjustable end-effector of thinning and transplanting was carried out,and the orthogonal test of thinning and transplanting was carried out on the basis of the parameter working range determined by the single-factor simulation test in the early stage.The optimal parameters of the end-effector were determined as follows: the seedling needle angle was 10 °,the penetrating angel was 4 °,the seedling needle spacing was 8 mm,and the pitch change speed was 5 mm/s.The verification test was carried out under the optimal parameter combination,and the plug seedlings were transplanted from 128-cell to 72-cell and from 72-cell to 50-cell respectively.The average seeding bowl deformation quantity of 128-cell was 1.13±0.68 mm,and the average seeding bowl deformation quantity of 72-cell was1.51±0.64 mm.The total success rate of transplant was 93.33%,and the transplanting efficiency of the whole machine was 22 plants /min.All the seedlings survived and met the design requirements. |
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