Regenerative braking control strategy based on joint high-efficiency optimization

Abstract

Traditional regenerative braking control strategies only consider how to ensure motor to work along with the battery/motor joint high-efficiency working line, but do not consider continuously variable transmission efficiency. However, continuously variable transmission efficiency varies between 70% and 95% which cannot be neglected. Based on the analysis of relationship among the battery, motor, continuously variable transmission, and synthesis efficiency, the battery/motor/continuously variable transmission joint high efficiency is calculated and obtained, and the regenerative braking control strategy is proposed. Comparing the previous control strategy with battery/motor joint high efficiency, the motor average generating efficiency increases by 2.91%, and braking energy recovery rate increases by 4.09% under Extra Urban Driving Cycle, while the motor average generating efficiency increases by 3.84%, and braking energy recovery rate increases by 5.74% under Federal Test Procedure-72 through offline simulation. Furthermore, under the hardware-in-the-loop test, the average generating efficiency increases by 2.72%, and the braking energy recovery rate increases by 5.03% under Extra Urban Driving Cycle, while the average generating efficiency increases by 3.13%, and the braking energy recovery rate increases by 3.94% under Federal Test Procedure-72. Both simulation and hardware-in-the-loop test results show that the proposed regenerative braking control strategy can realize battery, motor, and continuously variable transmission to work with joint high efficiency which can enhance braking energy recovery rate.