Optimal Control for Shifting Command of Two-Speed Electric Vehicles Considering Shifting Loss

Abstract

The energy efficiency of battery electric vehicles (BEVs) remains to be improved, and a two-speed transmission can be regarded as a prominent technology for BEVs because the two-speed transmission can improve acceleration and powertrain efficiency. However, the transmission device requires a well-designed control strategy because the performance of the vehicle can deteriorate if the controller selects an inefficient gear step. Herein, a gear shifting control concept based on dynamic programming is proposed to maximize the system efficiency, where the shifting loss caused by shifting actuators is considered in the control problem. The performance of the proposed control concept is compared to that of a controller utilizing a shifting map obtained via quasi-static optimization. It is shown that the proposed concept improves the efficiency by 0.01 ∼ 0.4 % compared with the shifting map applied to different hysteresis gaps, and around 13 % shifting frequency reduction has been experienced while the best energy hysteresis gap is selected. In addition to improving efficiency, the control concept can be extremely beneficial to engineers who wish to design the best control strategy without calibrating the control parameters when the actuator loss is considered in the control problem. © 2023, KSAE.