Effects Of Hydraulic Stiffness And Other Parameters On The Performance Of The Electro-hydraulic Position Servo System

With the development of modern industry, the electro-hydraulic servo system hasalso increasingly higher demand on the performance. And the system can work stably,rapidly and accurately in full hydraulic cylinder stroke. As we know theelectro-hydraulic servo system is an uncertain nonlinear system which parameters aretime-varying and are disturbed by external loads. Therefore it is very important toaccurately predict the performance of the system under the parameters such as theorifice coefficients, stroke, hydraulic stiffness and load stiffness are varying. For thestroke, hydraulic stiffness, load stiffness and other parameters will change in theprocess of system operation. The Analysis method is combining the theoreticalanalysis and simulation research. Mainly analyzes the changing rule of the orificecoefficients when the stroke, hydraulic stiffness and load stiffness are varying, and theinfluence of the change of these parameters on the performance of the system. On thisbasis a controller is designed to make the system obtain better dynamic and staticperformance. Mainly works were as follows:Firstly, taking an electro-hydraulic position servo system as the research object,the electro-hydraulic position servo system mathematical model is built according tothe theory of electro-hydraulic servo system control.Secondly, the factors of valve coefficient of the servo valve were analysed. Byintroducing the hydraulic cylinder-load equation the flow gain and flow-pressurecoefficient can obtained by the linearization of the flow equation at operating point.The numerical calculations can obtain the change rule of flow gain and flow-pressurecoefficient.Thirdly, according to the mathematical model and the numerical calculations ofthe orifice coefficients, the Simulink simulation model is built by the MATLAB. Takedifferent coefficient of the valve, the hydraulic stiffness and load stiffness on thesystem simulation model for numerical simulation. Analyze the effect of differentcoefficient of the valve, the hydraulic stiffness and load stiffness on the stability,quickness and accuracy of the system. The numerical calculations show that: underdifferent hydraulic stiffness and coefficient of the valve, the output responses willslow down and the accuracy will be reduced with the increase of stroke. Amplitudemargin is14.5dB-14.5dB, the rise time is0.356s-0.59s, the steady state accuracyis99.1%-99.1%.Finally, aiming at the problem of time-varying parameters, combining fuzzy control and PID control, fuzzy PID controller is designed to adapt to the change ofsystem parameters, and the system work stably, rapidly and accurately in fullhydraulic cylinder stroke. The steady state accuracy remains above99.3%.