Abstract
The resonance of the armature assembly is the main problem leading to the fatigue of the spring pipe in a torque motor of hydraulic servo valves, which can cause the failure of servo valves. To predict the vibration characteristics of the armature assembly, this paper focuses on the mathematical modeling of the vibration characteristics of armature assembly in a hydraulic servo valve and the identification of parameters in the models. To build models more accurately, the effect of the magnetic spring is taken into account. Vibration modal analysis is performed to obtain the mode shapes and natural frequencies, which are necessary to implement the identification of damping ratios in the mathematical models. Based on the mathematical models for the vibration characteristics, the harmonic responses of the armature assembly are analyzed using the finite element method and measured under electromagnetic excitations. The simulation results agree well with the experimental studies.
Highlights
Hydraulic servo control systems have been widely applied in many areas, such as manufacturing machines, automatic production lines, aerospace actuation controls, and agriculture machines, because of significant advantages, such as a large power density, high responding speed, and high control precision
Much work has been carried out to study the mechanism of self-excited noise in hydraulic valves, and the studies have shown that cavitations, shear-layer oscillations inside the flow fields, and vibration of the armature assembly are the possible causes of this noise [3,4,5,6]
The harmonic response of the armature assembly is investigated through numerical simulations and experimental measurements
Summary
Hydraulic servo control systems have been widely applied in many areas, such as manufacturing machines, automatic production lines, aerospace actuation controls, and agriculture machines, because of significant advantages, such as a large power density, high responding speed, and high control precision. Unpredictable self-excited noise at high frequency causes performance deterioration and even failure of hydraulic servo valves Such noise is a combination of fluid dynamic and mechanical noise, which is often accompanied by an intense oscillation of the armature assembly and is a main cause of spring pipe fracture, oil leakage, and control failure. Based on a corrected and experimentally verified mathematical model of two-stage mechanical feedback servo valves, Gordic et al studied the effects of the variation of a few torque motor parameters on the dynamic performance of servo valves [12]. Liao et al presented a new modal technique for extracting the damping properties of polymethyl methacrylate (PMMA) beams based on the hammer excited free response [19] This technique is useful for estimating high mode damping ratios using the log decrement method and band-pass filters. A damping ratio identification method based on the resonant free delay response is adopted in this work
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