Research On Structure Design And Control System Of Tomato Branch And Leaf Cutting Manipulator

The cutting of branches and leaves of fruits and vegetables plays a role in protecting the normal development of the main stem of the plant.At present,the cutting of branches and leaves in China is done manually,which has the disadvantages of high labor cost and low cutting efficiency.Therefore,it is of great significance to realize the automation of cutting of branches and leaves to improve the cutting efficiency.Taking tomato branches and leaves as cutting object,the design and experiment of tomato branches and leaves cutting manipulator were carried out:(1)The physical characteristics of tomato plants showed that the diameter of tomato lateral branches mainly ranged from 3.8 mm to 6.8 mm.The more mature the lateral branch is,the greater the shear force is.(2)According to the physical characteristics,growth space and cultivation mode of tomato lateral branches,a semicircular finger clamping device and a cutting circular blade end actuator were designed,and a stepping motor was selected as the driving motor;a five degree of freedom manipulator including three rotating joints and two moving joints was designed,and the moving joints included a first-order telescopic joint and a second-order flexible joint with a rack and pinion as the transmission mechanism The electric push rod is a secondary expansion joint with the main component.(3)The key components of the end effector of the tomato branch and leaf cutting manipulator were statically simulated,and the equivalent stress and strain of the main components were obtained.Considering the lightweight principle of the end effector parts,according to the simulation results,the key components of the end effector are optimized.The thickness of the cutting round blade of the end effector is reduced to1.5mm,the side thickness of the semicircular finger claw is reduced by 8mm,and the bottom thickness is reduced by 5mm.After optimization,the equivalent stress and strain of the end effector remain unchanged,and the mass is reduced by 0.05 kg.The kinematics simulation of the end effector shows that it takes about 5 seconds for the end effector to complete cutting and clamping,and there is no big fluctuation in the speed and acceleration.The kinematics,dynamics and statics simulation of the five degree of freedom manipulator are carried out.According to the results,the velocity,angular velocity,acceleration and angular acceleration of the manipulator do not fluctuate greatly in the whole working process,and the manipulator runs smoothly;the maximum torque of large arm joint and lumbar joint are 683N·mm and1746N·mm respectively,which verifies the rationality of the selected drive motor;the manipulator is in the static state The maximum equivalent force and strain are5.0007 mpa and 0.06216 mm,respectively.(4)The control system design of end effector and manipulator is completed.In this dissertation,STM32 is selected as the control chip of manipulator and its end effector,and the control module based on STM32 is made.(5)The theoretical error of tomato cutting manipulator was calculated and analyzed.The prototype of the manipulator is developed,the manipulator test platform is built,and the no-load and load tests are carried out.The experimental results show that the maximum theoretical errors of tomato branch and leaf cutting manipulator are 2.87 mm,5.61 mm and 2.93 mm on X,Y and Z axes respectively;the ultimate load of the end effector of the manipulator is 1.26 kg,which meets the working requirements of the manipulator;the average cutting time of the manipulator is 37.8s,the cutting success rate is more than 60%,and the maximum height of the manipulator is 335 cm The lowest height is 65 cm.