*2.3. Internal Combustion Engine Model*

The internal combustion engine (ICE) module mainly cooperated with the brake-specific fuel consumption (BSFC) lookup table according to the engine speed and torque to find the corresponding fuel rate. The total fuel consumption of the driving cycle was obtained through integration. A V-6 3.6-L engine efficiency chart is shown in Figure 5.

**Figure 5.** Internal combustion engine's efficiency chart.

### *2.4. Electric Motor*/*Generator Model*

The electric motor/generator (M/G) modules obtain the operating efficiency of the electric motor through a three-dimensional lookup table based on the current speed and torque. Two 60 kW permanent magnet AC motors were constructed. The efficiency diagram is shown in Figure 6. The power of the M/G was calculated as Equation (1).

$$P\_{\rm MG} = \omega\_{\rm MG} T\_{\rm MG} \eta\_{\rm MG}^k \tag{1}$$

*PMG*, ω*MG*, and *TMG* are the power, speed, and torque of the electric motor/generator, respectively. η*MG* represented the efficiency of M/G. If the values of the torque and the speed were positive or negative at the same time, the M/G was consuming power and performing as an electric motor. If the values of the speed and torque were of the opposite sign, the M/G was charging and running as a generator. *k* represents the energy path. If M/G operated as an electric motor, *k* was −1. If it operated as a generator, *k* was +1.

**Figure 6.** Motor/generator's efficiency chart.
