| As the electrical-mechanical transfer device of hydraulic servo valve, torque motor has a significant influence on the characteristics of the whole servo valve system. Magnetic fluid is a magnetic liquid shows a higher saturation when it is exposed to a magnetic field. Using its magnetization, damping and lubricating property, the applications of magnetic fluid are extensive. In the paper, by making use of the special characteristics, magnetic fluid was filled into the servo valve torque motor working gaps. Thereby the dynamic performance of servo valves torque motor can be improved. By using the larger magnetic permeability, magnetic fluid was used to improve the magnetic circuit efficiency in torque motor, enlarge the output torque and displacement of torque motor, and the output flow of servo valve. Correspondingly, the ability of noise-overcoming and system damping was enhanced due to the property of magnetic fluid. As a result, the stability of servo valve and servo-control system can be improved.The mathematical models of torque motor with magnetic fluid and without magnetic fluid were studied in this paper. The MATLAB/Simulink software was used to analyze the dynamic characteristics of torque motor. The time-domain and frequency-domain analysis were came out when the parameters of torque motor and magnetic fluid changed. A high speed laser displacement sensor was used to do experiment research on frequency response of torque motor with magnetic fluid and without magnetic fluid. The result of experiment validated the mathematical models and simulation methods. On the basis of theoretical models and experimental data, the least square technique was used to identify the indeterminable parameters in torque motor and parameters of magnetic fluid. Finally, simulation on the dynamic response characteristics of torque motor with magnetic fluid and without magnetic fluid is processed, and the effecting of anti-interference of torque motor with magnetic fluid is presented.
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