Modeling of armature-flapper assembly in a hydraulic servo valve by finite element analysis and acoustic excitation measurements

The vibration of armature-flapper assembly is one of the main reasons causing the self-excited noise in hydraulic servo valves. The study on vibration characteristics of armature-flapper assembly is vital and necessary to reveal the mechanism of self-excited noise and then suppress it. To predict the vibration characteristics accurately, an equivalent finite element model updated by the experimental results need to be established. In this work, the acoustic excitation method is adopted to extract the modal parameters by measuring the dynamic responses using the laser ranging technology. Some crucial geometry dimensions which affect the modal properties of armature-flapper assembly significantly are calibrated through structural optimization based on the tested natural frequencies. The simulated vibration characteristics of the optimized finite element model agree well with the experimental observations.