Design And Research Of Electro Hydraulic Servo System Controller For Heavy Load Manipulator

With the rapid development of science and technology,the development of industrial robots has also been driven.As an important branch of industrial robots,heavy-load mechanical arms are widely used in aerospace military industry,gold mining and other fields because of their advantages of high working efficiency,being able to work in harsh environment and carrying out heavy load tasks.However,if they want to give full play to the advantages of heavy-load manipulator,they must ensure that the manipulator can achieve certain accuracy,which puts forward certain requirements for the control strategy of the manipulator.In this paper,the electro-hydraulic servo system of valve-controlled cylinder of 7-DOF manipulator was taken as the research object,and the main research work is as follows:(1)The mechanical structure and technical indexes of heavy-load manipulator were analyzed,and the hydraulic servo system of 7-DOF manipulator was introduced,including the working parameters of hydraulic system and the oil circuit diagram of hydraulic servo system.The design scheme and working condition of valve of derricking cylinder,telescopic cylinder,advance and retreat cylinder control valve group were analyzed.(2)The nonlinear friction of actuator,nonlinear flow of servo valve,nonlinear pressure of actuator and nonlinear structure of differential equation in valve-controlled cylinder electro-hydraulic position servo system of heavy-load manipulator were analyzed and studied.The mathematical model of electro-hydraulic servo system considering Stribeck friction and system nonlinearity was established,which paves the way for the later controller design.(3)An adaptive robust controller was designed to deal with the uncertain parameters such as leakage coefficient,Coulomb friction coefficient,viscous damping coefficient and Stribeck friction parameter in the electro-hydraulic servo system to achieve accurate control of the system.Then,an extended state observer was designed to observe the external disturbances and unmodeled dynamics in the system,and was applied to the adaptive robust controller.The stability of the two controllers was analyzed by using Lyapunov theorem.The control performance of the two controllers under different conditions was verified by MATLAB simulation.The optimal controller was selected and applied to the heavy-load manipulator.(4)According to the actual parameters of the heavy-load manipulator,the controller was applied to it.Matlab software was used to simulate the horizontal,vertical and circular motion of the manipulator.Since the manipulator had variable load after grasping the workpiece,it is necessary to simulate the situation of grasping the workpiece during the movement of the manipulator.The obtained curves of position tracking,error and control input were analyzed to verify the effectiveness of the controller on the heavy-load manipulator.