Hybrid electric vehicle has the advantages of internal combustion engine vehicle and pure electric vehicle. The mode transition from EV (electric vehicle) mode to HEV (hybrid electric vehicle) mode requires frequent engine starting. The engine ripple torque (ERT) at low speed will affect the stable operation of the output shaft and has a significant impact on ride comfort. In order to improve the effect of mode transition process, the distribution of motor torque is optimized. The engine ripple torque model is established by combining theoretical formula with experimental data. The dynamic torque of the compound power-split model is decoupled. The mode transition process from EV mode to HEV mode is analyzed. Aiming at power, ride comfort and economy, the optimal starting control strategy of engine is designed based on dynamic programing algorithm. The influence factors of starting process are studied. When the optimization grid of motor torque is 5, the best trade-off between optimization accuracy and calculation cost is obtained. The results show that, the best ride comfort is obtained by using the dynamic programing algorithm when the speed is 30 km·h⁻¹ and the load torque is −178 N·m. The starting effect is the best when the initial crank angle is 0° while the transient response time is 0.84 s, compared with the initial crank angle of 90°, the economy is improved by 21%.

混合动力汽车具有内燃机汽车和纯电动汽车的优点。从 EV（电动汽车）模式到 HEV（混合动力电动汽车）模式的模式转换需要频繁的发动机启动。低速时的发动机纹波扭矩（ERT）会影响输出轴的稳定运行，对乘坐舒适性有显着影响。为了提高模式转换过程的效果，优化了电机转矩的分配。将理论公式与实验数据相结合，建立了发动机脉动转矩模型。复合功率分配模型的动态扭矩是解耦的。分析了从EV模式到HEV模式的模式转换过程。针对动力性、平顺性和经济性，基于动态规划算法设计了发动机最优启动控制策略。研究了启动过程的影响因素。当电机转矩优化网格为 5 时，优化精度与计算成本之间取得了最佳折衷。结果表明，当车速为30 km·h时，采用动态规划算法获得了最佳的平顺性。^-1，负载扭矩为-178 N·m。初始曲轴转角为0°时启动效果最佳，瞬态响应时间为0.84 s，与初始曲轴转角90°相比，经济性提高21%。