Research On Control Of Citrus Picking Manipulator Based On Sliding Mode

Citrus is one of the fruits grown on a large scale in our country as well as a cash crop.At present,the picking operation of citrus is mainly manual picking,facing the problems of low efficiency,high labor intensity and high labor cost.The development of intelligent citrus picking robots instead of manual picking can improve the picking efficiency and free farmers from heavy picking operations.As one of the executive mechanisms of the intelligent citrus picking robot,the speed,precision and robustness of each joint of the robotic manipulator determine the efficiency and quality of the picking operation.Therefore,the trajectory tracking control algorithm of the citrus picking robotic manipulator is studied in this paper.The main contents are as follows:(1)Establishment of the dynamic model of citrus picking manipulator: According to the nonlinear characteristics of citrus picking manipulator system,the Lagrange method was used to establish the dynamic model and analyze its dynamic characteristics.(2)Design the inverse sliding mode controller based on exponential reaching law: First,according to the idea of inversion design,the inversion sliding mode control strategy is proposed,and then the exponential reaching law is added to improve the track tracking speed.In addition,the saturation function is used to replace the symbol function in the control law to reduce the chattering phenomenon of the system.Finally,the feasibility of the control scheme is verified by simulation experiments.(3)Design adaptive inversion sliding mode controller: Considering that the citrus picking manipulator will encounter external interference with unknown upper bound in the picking process,the adaptive inversion sliding mode control strategy is proposed.The adaptive control algorithm can adjust the relevant parameters of the controller in real time according to the external disturbance,so as to effectively deal with the external disturbance with unknown upper bound,and improve the robustness of the control system of the citrus picking manipulator.Finally,the effectiveness of the algorithm is verified by simulation experiments.(4)Design an adaptive inversion sliding mode controller based on high gain observer:In order to solve the problem that the angular velocity measurement of each joint is inconvenient in practical application,a high gain observer is designed to observe the system state and estimate the angular velocity signal of the manipulator system,so as to solve the measurement problem of the angular velocity of the joint.In addition,by combining the high gain observer with the adaptive inversion sliding mode algorithm,an adaptive inversion sliding mode controller based on high gain is designed,which makes the manipulator system have good control performance.Finally,the feasibility of the control scheme is verified by simulation experiments.