The introduction of the fourth-stage fuel limit standard and the national VI emission standard has accelerated the development of more energy-efficient and environmentally friendly new energy vehicles by Chinese automakers. Currently, the 48V mild-hybrid system is one of the most effective technical solutions for the easy technology development, low cost, short development cycle, energy saving and emission reduction. In this paper, the 48V mild-hybrid vehicle is taken as the research object. Through the comparative analysis, the architecture of the 48V mild-hybrid system, the type of the battery and motor are determined. The external characteristics of motor are obtained by bench experiment and the battery model parameters are obtained by offline identification. Aiming at the research focus of the thesis, a single-target optimization strategy based on threshold is proposed, including engine startstop, power assisting, brake regeneration and SOC balance and the strategy model is built in Simulink. The 48V mild-hybrid vehicle model and the original vehicle model are built in the Cruise software. The co-simulation of the vehicle model and strategy model is achieved by calling the strategy model’s DLL file. The results show that compared with the original vehicle, the ratio of fuel economy improvement of the 48V mild-hybrid vehicle is more than 10%, the acceleration performance is increased by 9.7%, the climbing performance is improved by 23%, and the emission performance improvement effect is remarkable. Also, the proposed control strategy is better in reducing vehicle fuel consumption and maintaining battery SOC balance compared with the control strategy based on logic threshold.
Keywords 48V mild-hybrid vehicle, control strategy, energy saving and emission reduction, dynamic performance, Cruise