*3.2. Energy Consumption Index of EHA*

Energy efficiency is another key characteristic for EHA. Some previous works used the design parameters to calculate the efficiency of EHA, but could not evaluate energy consumption well since it is related to the working condition. In the present study, the energy consumption is indexed by the total energy input of EHA to finish the pre-defined representative simulation task. The integration of input power of the electrical motor is the energy consumption of the EHA, which can be expressed as:

$$E\_m = \int\_0^T \mathcal{U}(t)I(t)dt,\tag{1}$$

where *U*(*t*) and *I*(*t*) are the input voltage and current of the motor, which can be obtained from the dynamic simulation results; and *T* is the simulation time of the typical scenario.

#### *3.3. Dynamic Response Performance Index of EHA*

The dynamic performance is very important for EHA and it usually can be evaluated by rise time (*tr*). The smaller *tr*, the faster the system responds. The rise time is evaluated by the dynamic simulation. The reference angle has a step variation, and the EHA need to control the control surface to follow the reference signal. The time between 10% to 90% of step usually defined as the rise time. As can be seen from the Figure 5, the *tr* can be expressed as:

$$t\_r = t\_2 - t\_1 \tag{2}$$

where *t*<sup>1</sup> and *t*<sup>2</sup> are the time corresponding to the response curve being 10% and 90% of the steady state value, respectively.
