Research On Improved Sliding Mode Model-Free Control Strategy Of Hydraulic System

The electro-hydraulic control system which is widely used in modern industrial power systems has the functions of large output power,and wide speed regulation range.And it has the advantages of strong anti-load rigidity,faster response speed and larger power-to-quality ratio.With the rapid development of modern industry,higher requirements have put forward for the control accuracy and response speed of the electro-hydraulic control system.There are some complex nonlinear problems in the electro-hydraulic control system,such as the uncertainty of viscous friction coefficient,elastic volume modulus of hydraulic oil,oil leakage of hydraulic cylinder and external disturbance,etc.,which increase the difficulty of accurate modeling of the hydraulic system,and restrict the further improvement of control accuracy.Therefore,the research of model-free control is an important research direction,in order to improve the control accuracy of hydraulic system which doesn’t rely on the high-precision mathematical model of hydraulic system.This paper aims at the complex nonlinear problems of hydraulic system.Hence,the model free control algorithm is studied.The main contents of this project are as follows:(1)Improved sliding mode model-free control.In order to improve the accuracy and response speed of the electro-hydraulic control system,based on the model-free control algorithm,the product of error and error rate of change,the core idea of human-simulated intelligent control,is introduced into sliding mode control,and a new sliding mode function is designed to make the model-free control algorithm have the control quantity of multiplying the deviation and the deviation change rate,so as to integrate the new attitude information in the hydraulic dynamic process into the controller,improving the response speed and steady-state accuracy of the hydraulic system,and the control performance of the system.The effectiveness of the control method is verified by simulation.(2)Improved sliding mode model-free control based on RBF neural network.To solve the difficulty of parameter adjustment in improved sliding mode model-free control,a neural network model is established with the error,integral and change rate of error of hydraulic system as input and the controller parameters as output.The online adaptive adjustment of controller parameters is realized and the steady-state accuracy of the system is further improved.The effectiveness of the improved control method is verified by simulation.On the electro-hydraulic control comprehensive experimental platform,the model-free control,model-free sliding mode control,improved sliding mode model-free control are verified by experiments.Through analyzing the experimental results and then comparing the control performance of different control schemes,the effectiveness of the designed hydraulic system control method is verified,and its response speed and steady-state accuracy have been greatly improved.