Modeling And Simulation Research Of Valve-less Electro-hydraulic Servo System

Valve-less electro-hydraulic servo system is also called Driver Volume Control system, which is a hydraulic system that pump is directly driven by speed variable electromotor. This hydraulic system is controlled by different pump's flux, which is realized by changing the speed of pump, instead of changing pump's displacement. The most important character of this system is using AC timing motor to replace electro-hydraulic servo valve. This system has lots of advantages which come from hydraulic control system and AC timing system. Because of its close-loop construction, the system has some new advantages, such as environmental protection, oil saving. All these unusual advantages make it accord with the development of the industry.Based on reading lots of relevant references, this paper summarizes present research of the valve-less electro-hydraulic servo system, expatiates the principle and character of this system, introduces the principle of vector control and based on this theory, setting up the mathematic model of AC asynchronous motor and AC permanent magnet synchronous servo motor. In this paper, the theory and method of modeling and simulating by using Matlab/Simulink are introduced, the control model for simulating of AC timing system and Pump controlled cylinder are built by using Simulink and transfer function, and simulation blocks of valve-less electro-hydraulic servo system are built separately by using Ac asynchronous motor and Ac permanent magnet synchronous servo motor as actor. All above models are simulated and analyzed by Matlab.Through testing and analyzing every simulation block, this paper concludes that conventional electro-hydraulic servo valve system can be replaced by the AC timing system. The new system can preferably realize the control of hydraulic system.