# A Novel Optimal Control Strategy of Four Drive Motors for an Electric Vehicle
## 3 Discussion of Simulation Results  
### Performance Analysis of the Optimal Energy Management for the Electric Vehicle  
As shown in Figure 12 (top), this study uses the NEDC driving cycle as the input condition. The blue solid line represents the vehicle's demanded velocity, while the red dotted line represents the actual velocity after simulation. As shown in Figure 12 (bottom), the red solid line indicates the velocity difference between the target and actual velocity. From this figure, it can be observed that both at high and low velocity, the actual velocity can closely match the demanded velocity. From Figure 13, it can be seen that when the vehicle is in the mid-low velocity range, the torque distribution is mainly on the rear wheels with the front wheels as auxiliary. However, when the vehicle is in the high-velocity range, it is almost entirely driven by the rear wheels. Figure 11: The software development workflow for front and rear axle motors. Figure 10: The schematic configuration of the nested loop for front and rear axle motors. Energy Efficiency and Equivalent Fuel Economy Analysis of the Optimal Energy Management for the Electric Vehicle  
Through the motor's optimal energy distribution loop, the power distribution ratios of the four-wheel-side motors are calculated, as shown in Figure 14. However, using this distribution ratio to drive the motors will cause the vehicle to deviate and not be able to drive straight. The distribution method was modified to drive using the front and rear axle motors, and the power distribution ratios of the front and rear axle motors are shown in Figure 15. This thesis compares the energy consumption of front and rear axle motor electric vehicles, four-wheel-side motor electric vehicles, and electric vehicles with average output on all four wheels using the ECMS. Under the NEDC driving cycle, the front and rear axle motor electric vehicle achieved an energy consumption of 5.032 km/kWh, and the four-wheel-side motor electric vehicle achieved 5.071 km/kWh, compared to 4.803 km/kWh for the four-wheel average output electric vehicle, with respective improvement rates of 4.77% and 5.584%. In Figure 14, the \(\alpha\), \(\beta\), and \(\gamma\) values are calculated using the nested loops in Figure 7. The calculations of \(P_{d}\), \(SOC\), \(N_{m}\), \(\alpha\), \(\beta\), and \(\gamma\) are sequentially inputted into the  
Figure 12: Vehicle velocity results under the NEDC driving cycle. Figure 13: Torque results under the NEDC driving cycle. program, and all results are stored and arranged in a matrix. This matrix is plotted with torque on the \(X\)-axis and speed on the \(Y\)-axis, classified by \(\alpha\), \(\beta\), and \(\gamma\) to produce the results as shown in Figure 14. In Figure 15, \(\alpha\) is calculated using the nested loops in Figure 10, with the program sequentially inputting calculations for \(P_{d}\), \(N_{m}\), and \(\alpha\), and all results are stored and arranged in a matrix. This matrix is plotted with torque as the \(X\)-axis and speed as the \(Y\)-axis, with \(\alpha\) as the target to produce the results as shown in Figure 15.  
Figure 14: Parameter results of the power distribution ratio for four-wheel-side motors: (**a**) \(\alpha\); (**b**) \(\beta\gamma\); (**c**) \(\gamma\). In this experiment, the control architecture and whole-vehicle model were established using the simulation software MATLAB/Simulink(r) (R2021b, MATLAB, Natick, MA, USA). The NEDC and FTP-75 driving cycles were used for analysis. Additionally, in the Average Torque mode, the power distribution ratio is fixed, with the total demanded torque (\(T_{d}\)) equal to the sum of the front axle motor torque \(\left(T_{f}\right)\) and the rear axle motor torque (\(T_{r}\)), where both the front and rear axle motor torques are identical.