This paper aims to fully exploit the superior advantages in improving energy economy and dynamic performance of an electric vehicle powertrain equipped with two motors and multi-gear ratios. Considering the dependence of gear ratio selection on motor sizing, a two-loop optimization algorithm, combined by the global search method and non-dominated sorting genetic algorithm-II, is proposed to find optimal motor sizes and transmission ratios. An energy management strategy with novel shift schedules based on the equivalent efficiency of two motors, current engaged gears, and driving conditions is then recommended. The energy management strategy also optimizes the torque allocation to two motors to minimize electricity consumption. Subject to the total of motor peak powers being constant, simulation results for a case study of urban bus show that the optimization of both motor sizes and gear ratios considerably enhances the energy efficiency of powertrain system. In comparison with a single-motor powertrain, optimal motor scales of larger than 0.42 and corresponding gear ratios reduce the electricity consumption significantly by 4.82−5.08%. Besides, the introduced energy management strategy with optimal shift schedules is proved to ensure comparably maximum efficiency while effectively preventing unnecessary and repeated gear changes.

本文旨在充分发挥两电机多速比电动汽车动力总成在提高能源经济性和动力性能方面的优越优势。考虑到传动比选择对电机选型的依赖性，提出了一种将全局搜索法和非支配排序遗传算法-II相结合的双环优化算法来寻找电机的最佳尺寸和传动比。然后建议采用基于两个电机的等效效率、当前啮合的档位和驾驶条件的具有新颖换档计划的能源管理策略。能源管理策略还优化了两个电机的扭矩分配，以最大限度地减少电力消耗。在电机峰值功率总和不变的情况下，城市公交车案例研究的仿真结果表明，电机尺寸和齿轮比的优化显着提高了动力系统的能源效率。与单电机动力总成相比，大于0.42的最佳电机比例和相应的齿轮比可显着降低4.82-5.08%的电力消耗。此外，具有最佳换档计划的引入能源管理策略被证明可以确保相对最大的效率，同时有效地防止不必要和重复的换档。