*2.2. Modeling the EHA System with AMESim*

A diagram of the location of an EHA in the aircraft wing profile is shown in Figure 3, and the AMESim model of a flight control surface actuation system by EHA is shown in Figure 4. It consists of an EHA, a flight control surface, and a controller. The model in the red-dashed box is the EHA, which contains all the major parts of an EHA (motor, pump, anti-cavitation device, safety valves, and selector valve). The model in the green-line box is the controller. Only a simple three-loop (displacement, velocity, and current) controller is used in the present work, since the controller is not the purpose. The controller generates the command (as voltage) to drive a direct current motor, where the shaft of the motor is connected to a hydraulic fixed-displacement pump. The pump drives the actuator through a hydraulic circuit, which consists of re-feeding valves with a compensating hydraulic accumulator for anti-cavitation, a mode selector valve to select the mode (damping or active), and two pressure relieve valves for safety. The piston of the actuator moves the flight control surface of the aircraft, and the control surface is modeled with a planar mechanical 2D library, which can simulate the external load more realistically. This model has all the major parameters of the EHA system in the application scenario and the performance under different parameters can be obtained and evaluated.

**Figure 3.** Diagram of the location of the EHA in the aircraft wing profile.

**Figure 4.** Model of an EHA actuation system in AMESim.

In order to evaluate the performances of the EHA system, a typical angle command and load scenario of flight control surface is constructed, which is shown in Figure 5. The aerodynamic load include two parts; elastic load (proportional to the angle) and disturbance load. The angle and load commands include different conditions to evaluate different control performances, which are:


**Figure 5.** Dynamic response of a defined angle command and load scenario.
