Optimal design of torque distribution algorithm considering battery charge strategy for hybrid electric vehicles

Abstract

Hybrid electric vehicles, which have an internal combustion engine (ICE) and electric motor(s) (EMs), are effective to improve fuel consumption and exhaust emissions. We had constructed a novel energy management system (EMS) considering torque control strategy, in which a function called the torque control function was introduced to reduce CO₂ and NO_x emissions. However, only the regenerative braking was used for battery charge in the EMS. In this paper, an improved EMS considering the battery charge by ICE is proposed. To charge the battery, a charge torque considering the target state of charge (SOC) is newly introduced. To determine the torque control function and the charge torque, a sequential approximate optimization using a radial basis function network is adopted. CO₂ and NO_x are then simultaneously minimized. A multi-objective design optimization is the formulated, and the torque control function and charge torque are determined with a small number of simulation runs. Through the numerical simulation, the validity of proposed EMS is examined.