The Dynamic Characteristic Study Of Hydrautic Flapper-Nozzle Servo-Vavle With Magnatic Fluid

Hydraulic flapper-nozzle servo-valve is the most important component in hydraulic control systems. It is used very widely in industrial and aerospace application fields because of its high responding speed. But sometimes self-excited oscillations and noise may appear in hydraulic flapper-nozzle servo-valve if its construction is not selected very correctly. If self-excited oscillations and noise appear in hydraulic servo-valve, the performance of hydraulic control systems may lose stability. Magnetic fluid is applied in hydraulic flapper-nozzle servo-valve in this paper to overcome the self-excited oscillations and noise. Magnetic fluid is a new magnetic material, which is a colloid with magnetic particles suspending uniformly in the solution. It has both of the magnetic property of magnetic material and the property of fluid. It will not settle out of the solution under the working of gravity, centrifugal and magnetic force. When magnetic fluid is filled into the working gaps of servo-valve torque motor between the armature and cores, it shows a higher saturation magnetization because of the working of the magnetic field inside the gaps. It will exert resistance and damping force to the torque motor armature, so that the dynamic performance, especially the stability, of flapper-nozzle servo-valve can be improved. The self-excited oscillations and noise can be removed. At the same time, as magnetic fluid has a higher magnetic permeability, the efficiency of torque motor magnetic circuit can be improved. Therefore the output magnetic torque of torque motor can be increased.In this paper, mathematical model of hydraulic flapper-nozzle servo-valve is introduced. The mathematical model of magnetic fluid is built according to the reference introduction. And the mathematical model of hydraulic flapper-nozzle servo-valve with magnetic fluid is derived. The dynamic performance and characteristics of hydraulic flapper-nozzle servo-valve are simulated using MATLAB/simulink. The dynamic responses in time domain and frequency domain are given and compared when magnetic fluid is used or not in the servo-valve. Experiments are carried out to test the dynamic response of the servo-valve with or without magnetic fluid and the force characteristics on torque...