The common pilot stage of the EHSV is the double-nozzle flapper valve. Numerous academics have carried out modeling investigations on the DNFEHSV and the valve created using redundancy technology in recent years, and they have produced fruitful research findings.
To accomplish pilot control in the EHSV, Anderson et al. [
3] employed two slide valves rather than a single slide valve. The feedback spring rod of the armature assembly is no longer required, improving manufacturing precision and lowering production costs. Through mathematical modeling, Chen et al. [
4] established the static and dynamic characteristic equations for the single-stage DNFEHSV, and, in order to address the imprecision of the Taylor expansion local linearization approach, Mu et al. [
5] constructed the DNFEHSV model while taking nonlinear parameters like the flow at the nozzle into consideration. Wang [
6] studied the effects of the throttling edge fillet and radial clearance on the zero position characteristics of the three-stage EHSV by AMESim, and the simulation was used to assess how the degree of orifice clogging and the excessive oil–gas content affected the dynamic and static characteristics. The magnetic resistance of the permanent magnet and the magnetic permeator, as well as the magnetic leakage of the permanent magnet, were all considered in Liu’s [
7] determination of the electromagnetic torque linearized expression of the torque motor. The calculation formulas for the spring stiffness and the electromagnetic torque coefficient were modified. Wang et al. [
8] conducted the armature assembly sub-model by AMESet, and the DNFEHSV AMESim simulation model was established. Gordic et al. [
9,
10] established the EHSV simulation model with Simulink and analyzed the influences of zero gap length and coil turns. Li et al. [
11] established the DNFEHSV simulation model by AMESim and analyzed the effects of common faults. Li [
12] built the DNFEHSV multidisciplinary physical model through the Simcape Modeling Toolbox in Simulink. The model was highly precise and without complicated mathematical formulas. Shi [
13] established the DNFEHSV simulation model by AMESim and proposed the PSO-CG-BP neural network model. It could be used in the field of fault diagnosis for the EHSV. The above-mentioned investigators conducted a simulation modeling study on the EHSV using AMESim or MATLAB, developed a trustworthy theoretical simulation model, and analyzed the impact of different settings on the performance of the servo valve. But since these simulation models are designed to simulate the conventional DNFEHSV, it is quite easy to control displacement and match parameters for power stage four-side slide valves. Yan et al. [
14] developed a theoretical model for the triplex-redundancy EHSV and examined its dynamic and static properties using Simulink and AMESim, respectively. For a 2D servo valve, Yan [
15] created a double-redundancy controller that allowed for a free changeover between controllers in the event of a problem. Aiming for a high-power thrust vector control for the future heavy launch vehicle, Chen et al. [
16]. proposed a high-power redundant Electro-Hydrostatic Actuators (EHA) technical program. Adopting an advanced modular design, the EHA can realize a high-power output with a parallel connection of servomotor pumps with good dynamic performance and a high power-to-weight ratio, which verifies the technical feasibility of the EHA with higher redundancy levels, such as three or four redundancy levels. Han et al. [
17]. designed a control system through the utilization of a Q-filter-based disturbance observer (DOB), which could eliminate the force-fighting phenomena and respond effectively to unexpected disturbances in redundant actuators. The simulation results confirmed the effectiveness and reliability of the method in accurately observing and responding to the force-fighting phenomenon that occurs in the redundant driving device. Based on the redundancy theories, the researchers created the simulation model and evaluated its accuracy. Additionally, they computed the transfer function of the EHSV using redundancy architecture, which is suitable for DNFEHSV with redundant design in the pilot stage but not in the power stage. However, the DREHSV features a pilot stage composed of two double-redundancy double nozzle flapper valves, and the double-system power stage slide valve is controlled by a total of four torque motors; therefore, the inferred transfer function is not applicable to the DREHSV. The double-system slide valve, four sets of piston bushes, and a four-redundancy displacement sensor (LVDT) make up the power stage. The oil inlet and outlet of the slide valve have rectangular holes rather than the more common round ones. The control difficulty of the DREHSV is sharply increased. In addition, the double redundancy actuator studied is mainly driven by servomotor pumps, and there are few studies on adapting the DREHSV to driving. Therefore, this paper mainly adopts AMESim to carry out simulation modeling research on the DREHSV and indirectly introduces the double redundancy actuator driven by the DREHSV to verify the advantage of the redundant design for the power stage.
Because there is not an appropriate sub-model in AMESim, the armature assembly sub-model is created by AMESet with C-code in order to create the simulation model to analyze the performance of the DREHSV. Through theoretical study, the double-system slide valve model is built, and then the DREHSV simulation model is established. Through simulation and experimentation, dynamic and static characteristic curves are generated. The effects of different faults on the performance are analyzed by AMESim, and the advantage of redundant design is verified, which could provide a reference for the design, debugging, and maintenance of the DREHSV. Abundant sample data can be generated by the model for the fault diagnosis of the valve.