Design And Experiment Analysis Of Articulated 4-DOF Robotic Arm For Grape Picking

Grape is a kind of berry fruit grown in clusters,and they are popular with most people because of their plentiful juice and large grains.Traditional picking relies mainly on manual work.Picking operations are labor-intensive,costly,and tedious.With the transfer of China's agricultural labor force,the reduction of the rural population,and the aggravation of population aging,the labor force engaged in agricultural production is becoming less and less.Therefore,the development of key technologies for grape picking robots has become an urgent need in the development of facilities agricultural production.As an important executing mechanism in the picking robot,the robotic arm plays an important role in the picking process.In this paper,the design,simulation and experiment of grape picking robot arm are carried out based on straw planting edible grapes.The main research contents are as follows:(1)A brief overview of the domestic and foreign research status and key technologies of the robotic arm was provided.According to the growth and planting conditions of pruning food grapes under the fence,the overall design index of the picking robot arm was proposed.Then,according to the design index requirements to determine the robot configuration,degree of freedom and connecting rod length and other parameters.SolidWorks software was used to establish a three-dimensional model of grape picking robot arm.And the simplified model of the manipulator was established through Adams,and the dynamic simulation was carried out.When gripping 2Kg grapes as load,the lumbar,shoulder,elbow,and wrist joints require 95N·m,52N·m,48N·m and 12N·m as driving torques.,and select Yaskawa AC servo motor and planetary gear reducer as the drive system of the motor.(2)Using the D-H parameter method,the mathematical model of grape picking manipulator was established.The forward and inverse kinematic equations were deduced based on the link coordinate system,and the solutions of the forward and inverse kinematics were obtained.Through the Robotics Toolbox in MATLAB,the 3D simulation model of the robot arm was established to realize visualization.Comparing the forward and inverse kinematics calculation results of the mathematical model with the simulation results of the robot toolbox,the correctness of the mathematical model of the robot arm was verified.The Monte Carlo method was used to obtain the working space point cloud diagram and the two-dimensional coordinate projection diagram of the end effector point of the manipulator.Through the analysis of the point cloud image of the workspace,the correctness and rationality of the geometric parameters design of the robot arm are verified.(3)The trajectory planning of joint space and Cartesian space of manipulator was studied.The trajectory planning of the joint space introduced the cubic polynomial interpolation and the fifth-order polynomial interpolation mathematical model;The Cartesian space trajectory planning introduced space linear trajectory planning algorithm and space arc trajectory planning algorithm.Based on the principle of the shortest path,the space linear trajectory of the fifth-order polynomial interpolation was selected as the path of the end effector of the manipulator.The mathematical calculations and simulations were carried out to verify the rationality and correctness of the trajectory planning,and to provide the theoretical basis and support for the subsequent picking experiments.(4)Simulation of grape picking scenes in a laboratory environment,the hardware configuration and control procedures of the robotic arm control system were designed.The upper computer controller and the lower computer controller were designed based on the difference between the control target and the used object.The hardware drivers were programmed through the LABVIEW platform.The test part was divided into single joint position control test and grape picking test based on trajectory planning algorithm.In the single joint position control test,30 repeated experiments were performed.The average positioning error of the single joint was 2.32 mm,1.25 mm,1.21 mm,and 1.11 mm,respectively.The average reduction error was 2.43 mm,1.33 mm,1.23 mm and 1.12 mm.The joint movement of the robot arm was reset from the initial point to the picking point and finally to the fruit-setting point.The average value of the deviation between the theoretical point of the end effector marker and the actual distance is 5.47 mm,6.46 mm,and 5.19 mm,respectively,which meets the requirements for picking precision.Regardless of when the end-effector picks the grapes,the average time required for the robotic arm to reset from the initial point to the picking point to the fruit-setting point is 24.1 s,and the maximum time is 24.99 s.