Dynamic modeling and experimental investigations of a magnetostrictive nozzle–flapper servovalve pilot stage

Abstract

A magnetostrictive nozzle–flapper servovalve pilot stage is presented in this article, which is directly driven by a giant magnetostrictive actuator and features three nozzles for the development of large flow rate servovalve. According to the energy conversion sequence in this servovalve, a giant magnetostrictive actuator magnetization model, a giant magnetostrictive material rod eddy loss model and a servovalve dynamic pressure model are all established to enable quantitative depiction and modelling of the dynamic pressure response process of magnetostrictive nozzle–flapper servovalve pilot stage. Consequently, the matched simulation model of the magnetostrictive nozzle–flapper servovalve pilot stage with the mathematic model is followed to be established, and two unknown parameters of complex permeability are determined using the test data from the giant magnetostrictive actuator. By running this simulation model, flapper displacement and output pressure under different structural parameters and variational excited frequencies are determined, certain parameters that are sensitive to the dynamic characteristics of magnetostrictive nozzle–flapper servovalve pilot stage driven by giant magnetostrictive actuator are found and the accompanying rules are revealed. Finally, the experimental system of a magnetostrictive nozzle–flapper servovalve pilot stage driven by giant magnetostrictive actuator was built; both the step-input voltage response curve and the sine-input voltage response curve were captured; and these curves show that the amplitude bandwidth (−3 dB) and the phase bandwidth (−90°) of a magnetostrictive nozzle–flapper servovalve pilot stage can approach 150 and 110 Hz, respectively, which exhibit good agreement with the simulation results. Therefore, the magnetostrictive nozzle–flapper servovalve pilot stage offers a very promising prospect of the novel servovalves with the high-frequency response and the large flow rate.