HARMONIC RESPONSE ANALYSIS OF A HYDRAULIC SERVO-VALVE TORQUE MOTOR UNDER THE ACTION OF ELECTROMAGNETIC FORCE AND PRESSURE FLUCTUATION IN JET FLOW FIELD

To discover the mechanism of self-excited noise in servo valves, vibration characteristics of a hydraulic servo valve torque motor was studied. Firstly the working mechanism of a nozzle-flapper hydraulic servo valve was introduced, and then the mathematical models of the forces which act on the armature assembly were created. The mathematical model of harmonic response analysis for single degree of freedom system was presented and the relationship between resonance frequency and natural frequency was analyzed. By using ANSYS software, the harmonic response characteristics of the torque motor under the action of the electromagnetic field and the flow field were simulated. The harmonic response curves of key points in different directions were obtained and the resonance regularity in the range 0~4500Hz was analyzed. The simulation results show that the electromagnetic field and the flow field may excite the high frequency vibration of the torque motor, as a result, the self-excited noise may be induced.