Research On Mechanical Structure And Control System Of 3-DOF Apple Picking Robot

In recent years,with the gradual improvement of people's living standard,the proportion of fruit in the entire food consumption structure is increasing,especially for apple.However,due to the increasingly serious problem of aging and the development of industrialization and urbanization,the agricultural labor force is being shifted in the direction to industry,services,etc.,so the agricultural labor shortages are growing.Apple picking is one of time-consuming parts of apple production,needing to invest a considerable amount of labor.Picking automation is the most effective way to solve the problem.At present,in view of low mechanization and intelligence of agriculture,developing economic and commercial agricultural picking robot has important strategic significance.This paper aims to design a core component of picking robot,picking manipulator,to lay the foundation for the development of the whole picking robot.The main contents include the following aspects:(1)Designed a set of 3-DOF(degrees of freedom)picking manipulator based on cylindrical coordinates,due to the characteristics of modern fruit growing and the shortcomings of traditional articulated manipulator.This paper introduced the agencies,transmission mode and parameters of motion axis.(2)The picking manipulator was modeled in the environment of creo2.0.Structural static analysis was carried out to check its stiffness and strength and in order to analyse the dynamic performance of ball screw which has important influence on the manipulator positioning precision,the finite element analysis using ADAMS software was also accomplished.Result shows that the maximum stress value is 13.23MPa,while the minimum stress value is 30.473Pa,the maximum stress is much smaller than the material yield strength 235MPa,so the picking manipulator can withstand the 40kg of loading;The maximum force of the ball screw in the motion simulation is 1200N and the forces of motion axis which are in line with the objective laws.(3)An opened architecture based on CAN bus was used in the control system,the harvesting procedure of robot was expounded and the picking control program was compiled based on C#,the comprehensive measures of security were provided for picking manipulator in terms of hardware and software.Considering the rationality of the entire layout of picking robot,the control cabinet was designed.(4)The single neuron adaptive PID control method was used in the joint control and was modeled in the MATLAB/Simulink environment,Simulation result shows that the control method can adapt to the complex,unstructured work environment.Finally,we had made some experiments including motion-consuming and positioning accuracy which showed that the average values of time and motion error were 6.619s and 4.929mm,the design improved the positioning accuracy,reduced costs,time and increased picking efficiency compared with traditional articulated manipulator.