# A Novel Optimal Control Strategy of Four Drive Motors for an Electric Vehicle
## 4 Conclusions  
This study completes a new software model for an electric vehicle with novel four-wheel-side motors, using the four-wheel-side motors as the power source. It includes the driving mode model, the driver model, the lithium battery model, the vehicle dynamics model, and the energy management system model, with the following results:  
1. Established algorithms for the average torque mode, rule-based control, optimization of the front and rear axle motors, and four-wheel motors optimization. The optimization uses the ECMS method for development.
2. Compared to the average torque mode and rule-based control under the UDDS driving cycle, in a pure simulation environment, the enhancement rates for pure electric energy efficiency are 3.9%/6.8%/10.7% and 0.8%/4.8%/5.6%, respectively. In the hardware-in-the-loop (HIL) simulation comparison, the enhancement rates for pure electric energy efficiency are 3.6%/5.8%/6.1% and 0.6%/4.8%/6.0%, respectively. (These four improvement rates are based on 45 kW/95 kW and two control strategies.)
3. Compared to the average torque mode and rule-based control under the FTP-75 driving cycle, in a pure simulation environment, the enhancement rates for pure electric energy efficiency are 0.1%/0.5%/1.3% and 0.2%/1.5%/3.9%, respectively. In the hardware-in-the-loop (HIL) simulation comparison, the enhancement rates for pure electric energy efficiency are 0.1%/1.6%/5.1% and 0.4%/1.3%/4.8%, respectively. (These four improvement rate are based on 45 kW/95 kW and two control strategies.)
4. The four-wheel optimization algorithm showed a higher improvement rate compared to the front and rear axle optimization algorithm, mainly due to the four-wheel optimization algorithm's ability to more delicately control the output of each motor, reducing losses in the energy distribution process, thereby significantly enhancing overall efficiency.
5. The ECMS method considers all factors in its search, allowing it to find the global optimum solution.  
Future research will establish conditions for the lateral dynamics of electric vehicles, create vehicle safety criteria, and, under the condition of satisfying vehicle driving requirements, develop a new optimization method for four-wheel hub motors.  
Conceptualization, C.-H.W. and W.-Z.G.; Methodology, C.-H.W.; Software, W.-Z.G. and J.-M.Y.; Validation, W.-Z.G. and J.-M.Y.; Formal Analysis, C.-H.W. and W.-Z.G.; Investigation, C.-H.W.; Data Curation, W.-Z.G. and J.-M.Y.; Writing--Original Draft, C.-H.W.; Writing--Review and Editing, C.-H.W.; Visualization, C.-H.W.; Resources, C.-H.W.; Supervision, C.-H.W.; Project Administration, C.-H.W.; Funding Acquisition, C.-H.W. All authors have read and agreed to the published version of the manuscript.  
The authors would like to thank the National Science and Technology Council of the Republic of China, Taiwan, for financial support for this research under Contract No. NSTC 111-2221-E-027-081-MY3; and thanks to the APh ePower Co., Ltd. project for advanced vehicle control.  
The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.