Design And Analysis Of Apple Harvesting Robot's Manipulator

At present,the automation level of picking fruits and vegetables is still very low, because picking fruits and vegetables is a complex work.In the 21st century,countries around the world are all facing the problem of population aging,not only the high cost of labor,and not readily available.Therefore,the development of mechanized harvesting technology,research and development of robot picking fruits and vegetables are of great significance.Robots for picking fruits and vegetables are still in the phase of research and development,the commercialization of the process is still very difficult,one of the main reasons is that the robot's specific structure are weak in design and analysis.This paper was support by the National "863" Project "fruit harvesting robot research of key technologies"(Item No:2006AA10Z254).The apple harvesting robot's manipulator was designed and analyzed.A kind of 5-DOF series connected joint apple harvesting manipulator was put forward.Several end-effectors which were designed in practical way were fabrieated,the structure of the prototype was determined by the results of tests.Simulation and experimental results show that the manipulator and the end-effector have good performance for picking apple.The main research contents as follows:First,various robots for apples and other fruit-vegetable harvesting are analyzed. Aiming at lack of the current main structure designs,the basic principle for fruit vegetable harvesting manipulator structure design is presented.The specific features of picking apple with robots were analyzed by research on apple orchard;a kind of 5-DOF series connected joint apple harvesting manipulator was put forward.Based on apple tree's fruit distribution space,the manipulator structural parameters were analyzed by CAD technology.The optimal solution of the manipulator structural parameters was got by setting up the optimization model and programming on MATLAB.The whole structure and control scheme of the apple-picking robot were put forward in practical point of view.Then,some important parts of the manipulator were designed concretely,such as:take-off and landing platform of waist,joint-type robot arm and the end-effector.Second,the manipulator's kinematics model was established by means of the homogeneous coordinate transformation in the cartesian coordinate system,then,forward kinematics and inverse kinematic were solved separately.The jacobian matrix of the manipulator was solved by vector product method,so the relationship of instantaneous speeds between the joints and end-effector were set by the jacobian matrix,the acceleration direct and inverse solution were analyzed by using generalized inverse matrix.Based on the front specific design,the prototype model of the manipulator was set by using Pro/e which is a famous 3d entities modeling software.Then,the prototype model was introduced into ADAMS which is a simulation software,that made the process of manipulator movement visual.Forward kinematics and inverse kinematic were simulated,and the results of the simulation show that the solution of kinematics model was absolutely correct.The manipulator kinetics equation was established by lagrange equation and the analysis of ADAMS kinetics simulation was done,then the parameters of drive motor and the reducer of the robot joints were chosen.Third,the manipulator's workspace had portrayed based on the Monte Carlo principle through programming on MATLAB.The characteristics of the boundary singular configuration and internal singular configuration of the manipulator were analyzed and simulated using ADAMS,The CAD inverse solution model was put forward and on the basis of the CAD inverse solution model,the manipulator's three kinds path planning were set by ADAMS simulation,the three kinds path planning as follows:the manipulator along a straight line,a ellipticobstacle route and "Eyes-in-hand" obstacle avoidance route arrived at the target point respectively.Each path planning was feasible by analyzing the corresponding ADAMS curves.At last,several end-effectors which were designed in practical and intelligent way were fabrieated;the structure of the prototype was determined by the results of tests.It is composed of clamping mechanism,cutting devices,pneumatic system,and sensor control system.In the process of end-effector's design and manufacture,the engineering drawing of the end-effector's parts were made by Pro/e.On the base of ensuring the requirements of stiffness and strength,the non-standard parts selected aluminum alloy and engineering plastics.The prototype's weight is only 1.3kg.The experiment of apple picking proved that the picking program was reasonable and effective and its overall performance can meet the requirements of apple-harvesting robot.The end-effector needs only 2.3 s to perform actions of harvesting,which has a certain versatile for other globular fruits harvesting.