Optimization Design And Experiment Of Three Degree Of Freedom Apple Picking Mechanical Arm

China is a large country of apple planting and production in unstructured orchards.Apple picking is an important part of the production process,and the seasonal characteristics are obvious.It requires centralized labor in a short period of time.Due to the increase of labor costs and picking risks caused by the aging population,apple picking is more difficult.Therefore,the development of apple picking robot is very important.At present,China is in the development and test stage,and there are deficiencies in the structural design and automatic control of the picking robot.The specific research contents of this paper are as follows :(1)Parameter design and kinematics modeling of apple picking mechanical arm.According to the regional distribution of the fruit,the target picking space of the mechanical arm is determined.The structural parameters of the mechanical arm are designed through the target picking space,the structural dimensions of the mechanical arm are optimized,and the utilization rate of the working space is improved.The three-dimensional modeling and kinematics modeling of the mechanical arm lay a theoretical foundation for the mechanical arm control.The workspace of the mechanical arm is visually solved by Matlab software to verify the matching degree between the mechanical arm workspace and the target picking space.(2)Lightweight design of apple picking mechanical arm.The dynamic model of the mechanical arm is established by Newton-Euler equation,and the simulation of apple picking process is completed.Through the theoretical data of the key positions in the dynamic model,the stress and strain of the mechanical arm and its key components are analyzed,and the stress and strain under different lightweight schemes are compared to obtain the optimal lightweight scheme.By comparing the simulation data of the mechanical arm before and after lightweight,the peak driving torque is reduced by21N·m and 15N·m respectively,and the mass of the big arm and the small arm is reduced by 2.1kg.The dynamic model provides theoretical data support for the lightweight design of the mechanical arm,and also provides a theoretical basis for motor selection.(3)The control system of apple picking mechanical arm is built.The CANopen protocol is used to complete the communication between the industrial computer and the motor servo driver.According to the motor motion control system,the PDO mapping configuration and motion control configuration suitable for the apple picking mechanical arm system are designed.According to the control requirements and processes of each module of apple picking,the control system of apple picking test platform is designed and the design of human-computer interaction interface of upper computer is completed.(4)Physical prototype test of apple picking experimental platform.The prototype of the mechanical arm is built and the prototype of the apple picking test platform is integrated with each module,and the picking test is carried out in the laboratory environment and the orchard environment respectively.Firstly,the positioning accuracy,motion planning and control program of the mechanical arm are tested in the laboratory environment,and then the automatic continuous picking of the apple picking test platform is tested.The picking success rate is high,reaching 94%,and the control system also has high reliability.Then,the apple picking test platform was tested in a complex orchard environment.The picking effect was lower than that in the laboratory environment,the total success rate could still reach 81%.The total average picking time was 11.1s,and the automatic picking function of apple was realized.