Theoretical and experimental investigations of a magnetostrictive electro-hydrostatic actuator

In this study, the time-domain model of a magnetostrictive electro-hydrostatic actuator (MEHA) is built from the viewpoint of energy conversion, which consists of four energy transformation stages: electrical-magnetic, magneto-elastic, elastic-hydraulic and hydraulic-mechanical energy transformation. Accordingly, a Jiles-Atherton hysteresis model with the dynamic eddy current effect has been incorporated into the MEHA model, and a magneto-elastic energy transformation model has been established to depict not only the relationship between the magnetostriction and magnetization of a giant magnetostrictive material (GMM) rod, but also that between the magnetostriction and pre-stress of the GMM rod. Based on Boyle's law, an effective fluid bulk modulus equation is deduced to show a nonlinear functional relationship with fluid pressure. A pump chamber pressure model, a reed valve port flow equation model, a reed valve vibration model, a fluid pressure model in the high-pressure side cylinder, and a fluid motion model are later built sequentially to depict the complicated elastic-hydraulic transformation process. Finally, experiments show that the motion of the cylinder piston, as well as the pump flow rate, agreed well with the established model results under varying loads.