Research On Position Control Strategy Of Valve Controlled Asymmetric Cylinder System

Electro-hydraulic servo system has the advantages of large output torque,high bearing capacity,strong anti-interference ability,so it is widely used in the industrial field to complete a variety of complex tasks.In recent years,with the development of manufacturing technology and high technology in our country,there are higher requirements for the control precision and performance of electro-hydraulic servo system.The precision and robustness of the control system are affected by the parameter uncertainty and nonlinear factors of the electro-hydraulic servo system.This thesis takes the valve-controlled asymmetric cylinder system as the research object and the realization of high-precision control as the research goal.The main contents of the study are as follows:The working principle of the valve-controlled asymmetric cylinder system is deeply analyzed,and the state-space model of the valve-controlled asymmetric cylinder system is constructed according to the load-flow-pressure characteristic equation of the zero-opening four-way slide valve,the flow-pressure continuity equation of the hydraulic cylinder,the load balance equation and the dynamic characteristic equation of the servo valve,and its strict feedback form is derived to facilitate the design of the adaptive robust control strategy.The mathematical model and physical model of the valve controlled asymmetric cylinder system are built on the MATLAB\Simulink simulation platform.The simulation results show that the derived mathematical model can better reflect the working characteristics of the real hydraulic system.Aiming at the problems of complex nonlinearity in valve-controlled asymmetric cylinder system and difficulty in accurate modeling,a Tracking differentiator fuzzy PID control algorithm based on improved particle swarm is proposed,which is independent of complex model and convenient for tuning.The improved adaptive elite strategy particle swarm optimization algorithm based on Tent map can further avoid the problem that the standard particle swarm is easy to fall into the local optimal,and the convergence speed is fast.The simulation results show that the designed control strategy does not depend on the empirical tuning,and can improve the control accuracy of the valve controlled asymmetric cylinder system.Aiming at the problems of parameter uncertainty,interference and nonlinear factors caused by other unmodeled items in the valve-controlled asymmetric cylinder system,an adaptive robust control strategy based on the improved dynamic surface is proposed.Firstly,a dynamic surface method based on high-order filters is designed to avoid the "complexity explosion"caused by the traditional backstepping method.Secondly,a discontinuous projection adaptive operator is designed for parameter uncertainty.Finally,a robust controller based on interference observer is designed to compensate lumped disturbance items for a series of disturbance items caused by disturbance,friction and external load changes.The stability of the control algorithm is proved by Lyapunov function,and the robustness of the algorithm is verified by Simulink simulation.The Amesim and Simulink co-simulation platform and the top cylinder physical experiment platform are built,and the two proposed control strategies are experimentally verified and compared with the traditional methods.Through the analysis of experimental datas,the effectiveness of the proposed control method in tracking accuracy and robustness is verified.