Dynamic Characteristic Research Of Jet Pipe Servo Valve With Magnetic Fluid

Jet pipe servo valve has a good prosperity in the field of aviation, aerospace, ship craft, electrohydraulic system control and so on because of the high resistance to contamination, high sensitivity, high safety and long life. However, by comparison with flap nozzle servo valve which has been used widely and popularly by now, the torque motor of jet pipe servo valve has a larger rotary inertia. This causes low natural frequency of servo valve, and thus the response speed of jet pipe servo valve is slow. Moreover, the jet pipe of servo valve has large flexibility, and it is easy to excite oscillations and noise in the valve, which is named self-excited oscillations and noise. Because of the self-excited oscillations and noise, the servo valve loses its stability. Magnetic fluid shows higher saturation when it is exposed to magnetic field. In this paper, magnetic fluid is used to improve the dynamic performance of jet pipe servo valve by filling magnetic fluid in the working clearances of torque motor between armature and core. On one hand, it may exert damping on the armature of torque motor and overcome self-excitation of jet pipe. One the other hand, it may enlarge magnetic permeability of working clearances and improve magnetic circuit efficiency of torque motor to boost dynamic response speed of servo valve.In this paper, simulation analysis and experimental research are given about dynamic response characteristics of jet pipe servo valve with magnetic fluid and without magnetic fluid. Mathematical models of jet pipe servo valve with magnetic fluid and without magnetic fluid and mathematical model of magnetic fluid are deduced. Dynamic characteristics of jet pipe servo valve with magnetic fluid and without magnetic fluid are simulated in frequency domain and time domain by using MATLAB. Simulation results are compared and analyzed. Experimental research of frequency response about jet pipe servo valve is carried out about jet pipe servo valve with magnetic fluid and without magnetic fluid, and experiment results are also compared. At last, according to the experimental data of dynamic characteristics, mathematical models of jet pipe servo valve with magnetic fluid and without magnetic fluid which are used in the experiment are identified by using the method of system identification.