| In recent years,the planting area and total yield of fruit increased year by year in our country,in the process of fruit production,the production cost of 50%-70% comes from picking.The picking operation is repetitive and the labor demand is large,but the mechanical equipment used for fruit picking is less and the level of intelligence is low,which cannot effectively liberate people from the complicated agricultural production,cannot effectively save the labor resources,improve the productivity.Therefore,the study of intelligent and efficient fruit picking robots helps to liberate people from agricultural production and reduce production costs and improve labor productivity.The picking manipulator is the most important executive part of picking robot,Its motion planning and task planning directly affect the success rate and efficiency of the picking robot.Therefore,it is necessary to study the motion planning and mission planning of the picking manipulator.The main research work of this paper is as follows:(1)The positive and inverse kinematics analysis of the picking manipulator was carried out.The "minimum energy" criterion was used to select the wanted inverse solution when the eight inverse solutions of the manipulator were obtained by using the analytical method.The positive and inverse kinematics simulation interfaces for manipulator were built based on MATLAB GUI with the aid of Robotics toolbox and the simulation results showed that the kinematics solutions were correct.(2)A method of picking posture planning considering the fifth joint separation that could first determine whether fruit picking was in the picking space,and then determine the picking arm gesture was proposed,which was demonstrated by theoretical calculation and MATLAB simulation.For trajectory planning for joint space,the motion characteristics of several trajectory planning methods were compared and the cycloidal trajectory planning was selected finally.Combining posture planning and trajectory planning,a single fruit picking simulation experiment was carried out.The experimental results showed that the manipulator could adaptively plan the attitude and trajectory to meet the movement requirements of the robot.(3)Aiming at accomplishing the task of picking up a number of fruits continuously for picking robots,a mission planning method based on "minimum weighted joint angle" was proposed to determine the objective function of mission planning.The ant colony algorithm were used to solve the problem.The simulation interface of the robot arm continuously picking multiple fruits was programmed.Comparing the proposed planning method and a planning method based on the "minimum path" in the simulation,the multiple simulation results showed that the method could not only meet the requirements of picking multiple fruits continuously,but also the proposed method saved more energy than the "shortest path" approach when the number of fruits was more than three.(4)A picking experiment platform was built in the laboratory and many single fruit picking and multiple fruits picking experiments were carried out.The experiments of single fruit picking showed that the motion planning could make the robot to complete the motion requirement of single fruit picking.The average picking time for a fruit was 25.5s.In the multiple fruits picking experiments,the results showed that the mission planning based on the "minimum weighted joint angle" could make the robot automatically complete the continuous picking task and the picking time of the method was shorter than the "minimum path" method. |
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