Research On Electro-hydraulic Servo Valves Controlled Cylinder System Basing On Load Port Independent Control

With the development of science and technology, electro hydraulic servo system plays a more and more important role. The introduction of load port independent control technique, not only inherits the character of fast response and high control precision for valve controlled cylinder system, but also makes up the shortage of traditional valve controlled cylinder system having poor control performance in beyond load conditions, and ensures high control precision of system in different load conditions.The principle of valve controlled cylinder electro hydraulic servo system basing on load port independent control is given. The station equation model is built and examined. Comparing load port independent control system with traditional single valve control system in theoretical analysis and simulation, load port independent control system is proved better. Combining flow conductance and static operation point theory, a calculation method for pressure control target is posed. With the analysis of character of system pressure control, a dynamic monotone-variable pressure control method basing on error is given. The flow of servo valve is controlled by calculated flow feedback control method. For four load conditions of system, a mode switch control strategy of controller is designed.For control algorithm, active disturbance rejection control(ADRC) is chosen. Firstly, the reason for using ADRC is explained and the disadvantage of proportional-integral-derivative(PID) algorithm is discussed. Then, the derivation processes of tracking differentiator(TD), extended state observer(ESO) and nonlinear feedback(NF) are given and the tuning method of controller parameters is discussed. In MATLAB-AMESim united simulation, speed and position control of hydraulic cylinder are simulated, and the results are analyzed.