Structural Design And Analysis Of A Series-Paralle Tomato Picking Manipulator

Tomato is a kind of berry fruit with flat or nearly spherical fruit,with two main colors: orange and bright red.Due to its fresh and juicy flesh,rich nutrition,and special flavor,it can be eaten raw,cooked,and processed into ketchup,and is deeply loved by people.The traditional picking method is manual picking,with high labor intensity,high cost,and low efficiency.It is the most time-consuming and laborious in the entire agricultural production.Therefore,relying on advanced science and technology,it is urgent to design and develop an intelligent tomato picking robot arm to replace manual picking,which not only promotes the development of picking agriculture,but also is the trend of future agricultural development.This paper takes tomatoes in greenhouse as the object of picking,aiming at the problem of tomato automatic picking,and combining with the actual planting situation,carries out the design and simulation test of tomato picking manipulator.The main research contents are as follows:The research status and key technologies of the harvesting manipulator at home and abroad are briefly summarized.According to the specific conditions of tomato planting and growth in greenhouse,the overall design scheme of the harvesting manipulator is proposed.According to the proposed design indicators,determine the configuration of the tomato picking robot arm,select a joint type mechanism as a series boom,a 3-RRS mechanism as a terminal actuator,and a series parallel hybrid robot arm as the overall framework.Then determine specific parameters such as joints and connecting rods,and obtain the torque required for each joint of the picking robot arm.Based on these parameters,The Ruite 57 closed-loop stepper motor is selected as the driving motor of the parallel mechanism,and the servo motor and the green harmonic reducer of Gugao Company are selected as the driving system of the picking manipulator.Finally,the three-dimensional model of the series-parallel tomato picking manipulator is drawn using the Solidworks graphics software.The D-H parameter method is used to make kinematics equations of the series boom and the parallel end mechanism of the tomato picking manipulator.The simulation of the kinematics equations of the series boom is carried out in Matlab software through the Robot Toolbox tool.The correctness of the mathematical model of the manipulator is verified by comparing the calculation results with the simulation model.Then the model simplification and kinematics analysis of the overall manipulator are carried out,Then,the Monte Carlo method is used to solve the working space point cloud diagram and each two-dimensional coordinate projection diagram of the end effector of the tomato picking robot arm.Through comparative analysis,the rationality and correctness of the structure design and size parameter design of the robot arm are verified.The model of shoulder joint parts is imported into Ansys finite element analysis software for statics analysis.When the load simulation picking environment is added,the stress distribution and elastic deformation of 6061 aluminum alloy material are within the safe range.Then,based on virtual prototype technology,dynamic simulation analysis is carried out in ADAMS software,and the curve diagram of each joint torque changes with time is obtained,which verifies that the selected motor and reducer models are safe and reliable,Able to meet harvesting needs.The assembly and experimental analysis of the prototype were carried out,using6061 aluminum alloy as the main manufacturing material for the robotic arm,and the production and assembly of the prototype were carried out.The scheme of PC+motion control card+motor driver was selected to build the hardware part of the control system and compile the simulation modular program.The tomato picking scene was simulated in the laboratory environment,and the tomato picking experiment based on trajectory planning algorithm was carried out.After 10 repeated experiments,the average positioning error of the end effector was measured to be less than 7 mm.Without considering the picking time of the end picking paws,the average time for the mechanical arm to move from the initial position to the fruit picking position and then reset was 7.3 s,with a maximum time of 7.7 s.