Abstract: When the hybrid electrical vehicle is cruising, in order to reduce the fuel consumption of the engine and improve the service life of the battery, the work areas optimization of the engine and motor is considered in the energy management strategy of hybrid electrical vehicle. At the same time, the work areas optimization of the battery is considered too. Aiming at this problem, the longitudinal dynamics of a mild hybrid electric vehicle with continuously variable transmission(CVT)is firstly analyzed. And then, the efficiency of total system under different cruise conditions is studied by comprehensively considering the efficiencies of the engine, motor, battery and transmission system. After the objective function and constraints are obtained, the sequential quadratic programming (SQP) algorithm is applied to the optimization of system efficiency for the mild hybrid electric vehicle. At last the optimal battery power and optimal speed reduction ratio are found for different cruise conditions. The optimization results show the characteristics of the drive system, and these results can lay a foundation for the optimization of the drive system.

Key words: Continuously variable transmission, Cruise, Hybrid electric vehicle, System efficiency