In this study, an integrative giant magnetostrictive material-based electro-hydrostatic actuator (GMEHA) was designed. Firstly, the uniform of magnetic field distribution on giant magnetostrictive material rod was obtained by using finite element method, i.e. the nonuniformity of the axis and radial direction magnetic field intensity were less than 3% and 0.05%, respectively. Secondly, the flow rate model through the reed valve model was established in COMSOL Multiphysics software, and the relevant properties of reed valves were studied. Thirdly, the dynamic mathematical model of GMEHA was systematically established based on the operational principles of the GMEHA, accordingly, and the simulation model of GMEHA was built in Matlab/Simulink. Finally, the model and simulation results were subsequently verified with the experimental data, which indicates the effective output stroke of the designed GMEHA reached 70 mm, and the maximum no-load output flow was 0.85 L/min at approximately 250 Hz with the best working frequency; the blocked force was nearly 120 N. These results demonstrated the accuracy of the theoretical model and provided a foundation for the design and optimization of the GMEHA.

In this paper, focusing on the application-oriented giant magnetostrictive material (GMM)-based electro-hydrostatic actuator, which features an applied magnetic field at high frequency and high amplitude, and concentrating on the static and dynamic characteristics of a giant magnetostrictive actuator (GMA) considering the prestress effect on the GMM rod and the electrical input dynamics involving the power amplifier and the inductive coil, a methodology for studying the static and dynamic characteristics of a GMA using the hysteresis loop as a tool is developed. A GMA that can display the preforce on the GMM rod in real-time is designed, and a magnetostrictive model dependent on the prestress on a GMM rod instead of the existing quadratic domain rotation model is proposed. Additionally, an electrical input dynamics model to excite GMA is developed according to the simplified circuit diagram, and the corresponding parameters are identified by the experimental data. A dynamic magnetization model with the eddy current effect is deduced according to the Jiles-Atherton model and the Maxwell equations. Next, all of the parameters, including the electrical input characteristics, the dynamic magnetization and the mechanical structure of GMA, are identified by the experimental data from the current response, magnetization response and displacement response, respectively. Finally, a comprehensive comparison between the model results and experimental data is performed, and the results show that the test data agree well with the presented model results. An analysis on the relation between the GMA displacement response and the parameters from the electrical input dynamics, magnetization dynamics and mechanical structural dynamics is performed.

A novel configuration of a four-nozzle flapper servovalve driven by a giant magnetostrictive actuator is described, and giant magnetostrictive actuator displacement model and four-nozzle flapper valve pressure–flow equation are built, which can quantificationally describe the physical process from input current to control pressure in the giant magnetostrictive material–based four-nozzle flapper servovalve. Then, by a computational fluid dynamics method, control pressure under different zero-clearance configurations is determined by the numerical method and compared with the control pressure determined by a theoretical calculation method, which verifies the availability of the above-mentioned numerical method and the accuracy of the implemented numerical model. Subsequently, to elucidate the interaction rule between the control pressure and the orifice flow with the main structural parameters of a four-nozzle flapper servovalve, the parameters and the configurations of a single nozzle, four nozzles and a fixed orifice are investigated, which provides a theoretical basis for the design and optimisation of a giant magnetostrictive material–based four-nozzle flapper servovalve. A test system of a giant magnetostrictive material–based four-nozzle flapper servovalve is established, and the test results of static control pressure and hysteretic control pressure are obtained, which enables the determination of the maximum output control pressure.

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.

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.