Design And Experimental Study On Cutting Device Of Rootstock For Grafting Seedlings In Field Based On 3-RPR Mechanism

Grafting is an important link of breeding and cultivation of seedlings.Meanwhile,grafting is a kind of repetitive operation with high intensity and high precision.At present,the grafting of fruit trees and seedlings in the field is mainly completed by manual labor,and the labor intensity of workers is high,and the survival rate of grafting is closely related to the working proficiency of workers.Hence,it is very important to realize the mechanization and automation of the grafting of fruit trees and seedlings.Due to the requirement of land utilization,intensive planting mode is generally adopted to cultivate seedlings in the field,so field grafting is faced with problems such as limited working space,complex cutting trajectory and large cutting force.In view of the above problems,this paper designs a field seedling grafting rootstock cutting device based on 3-RPR mechanism,and the vibration sawing is used to reduce drag,which has a certain research significance and application prospect.The main research contents of this paper are as follows:(1)Through the field investigation of seedling grafting,the task planning of the rootstock cutting operation is carried out,and the improved“split grafting method”is determined to be adopted for mechanized grafting operation.Combined with the degree of freedom required by the rootstock cutting operation,the basic motion screw system of the rootstock cutting device is established based on the screw theory,and the constraint screw system is deduced to determine the basic configuration of the device.According to the above analysis,the overall structure design of the rootstock cutting device is carried out,and the modal analysis is carried out to avoid the resonance phenomenon between the vibration sawing machine and the device with high frequency vibration.(2)Through kinematics analysis of rootstock cutting device,the inverse kinematics equation is established,and the expression form of its Jacobian matrix is deduced,which provides theoretical basis for motion control and stiffness analysis of rootstock cutting device.Based on the inverse kinematics equation,the structure parameters of the rootstock cutting device are determined in combination with the limitation of rootstock cutting working space in the field.The workspace of the device is analyzed by the limit boundary search method,and the correctness of the inverse kinematics of the device is verified by the simulation of ADAMS virtual prototype.(3)In order to ensure the survival rate of grafting,the cutting surface of the rootstock is required to be smooth,so the device needs to move smoothly in the process of operation.At the same time,the limited space requires the device to be small,and the device needs to have efficient force transfer performance.According to the performance requirements,the key structural parameters of the device are optimized by combining the motion/force transfer performance indexes.In order to achieve cambium alignment during grafting,it is necessary to ensure the dimension accuracy of the cutting of the rootstock,which requires the device to have good stiffness performance.Therefore,the stiffness performance of the device before and after optimization is compared and analyzed based on the minimum feature method.(4)Based on the parameter optimization results and combined with the rootstock cutting agronomic process,the movement trajectory planning of the device is carried out.The coordinates of each track point are calculated,the interpolation algorithm is designed,and the motion control of the rootstock cutting device is realized by combining the inverse kinematics equation.On this basis,the control system hardware construction,control process planning and control program writing,complete the design and debugging of the control system.(5)A prototype test platform is built and rootstock cutting test is carried out with apple seedlings as the test object.The feasibility of the prototype is verified by testing the different growth conditions of the seedlings.The rootstock cutting ability of the device is verified by rootstock cutting success rate of the device before and after parameter optimization.Based on the planarity error of the cutting surface of the rootstock and the angle error of the cut,the effect of the rootstock cutting device is analyzed.The experimental results show that the seedling grafting rootstock cutting device based on 3-RPR mechanism can complete multi-track rootstock cutting operation in confined space,which provides a reference for the research and development of the field grafting rootstock cutting device.