Dynamic Optimization Method for Speed Ratio of Electric Vehicle with Two-Speed Transmission System

Currently, most of speed ratio optimizing methods for automotive transmission system belong to static optimization, while values of transmission ratio in the whole optimization process of velocity ratio are changing constantly. In order to obtain the best economic performance for the vehicle, corresponding gear- shift schedules should be adopted to different speed ratio. The paper has put forward a dynamic optimization method for speed ratio of the transmission system through analyzing deficiencies of static optimization method for speed ratio of transmission system. The method takes speed ratio of transmission system as design variable, and establishes objective function which considered lightweight design principles of transmission system. With ISIGHT-MATLAB/Simulink co-simulation optimization software platform and shift point judgment rules, it implementes dynamic optimization of speed ratio for transmission system, and has conducted comparative analysis on optimizing results simulated with static optimization method for speed ratio of transmission system. Ultimate optimizing results have indicated the correctness of the dynamic optimization for velocity ratio put forward in the paper as well as the correctness of considering lightweight design principle for the transmission system put forward in the paper.