Optimal Design And Energy Management For A Multi-mode Power Split Hybrid Electric Transmission

Due to climate degradation and energy shortages,the development of new energy vehicles is an inevitable trend,currently,hybrid electric vehicle(HEV)is still a better solution.For heavy-duty trucks,multi-mode power split HEV transmission has good adaptability.Considering the large size and multiple application scenarios of heavy-duty trucks in China,this study designed a new multi-mode power split HEV transmission suitable for heavy-duty trucks with mode continuity characteristics.And the parameters are optimized and an energy management strategy is developed.The details are as follows:Based on the lever method,the split-ratio characteristics of the power split system are analyzed,and the relationship between the split ratio and structural parameters is obtained.By analyzing the characteristics of mode continuity from both functional and operational perspectives and considering output speed and transmission relationship,the three conditions of mode continuity are summarized.The configuration evaluation criteria is established by comprehensively considering transmission efficiency,motor power level,parameter applicability,etc.,and configuration optimization based on comprehensive performance evaluation and functional and structural design of multimode schemes that consider mode connection characteristics is conducted.Aiming to the designed multi-mode power split HEV transmission,vehicle type matching and power source selection are conducted.And the power level matching of the electric motor is completed by solving the split characteristics of the two power split modes and considering the driving requirements.According to the vehicle speed demand and the relationship between the rotational speeds of various components and the range limits,the range of structural parameters is determined.With the fuel economy as the optimization goal,the structural parameters are optimized based on Genetic Algorithm.The torque coordination control strategy based on optimal engine efficiency is determined,and specific control logic between various components and simplified energy management strategy are formed.The mode switching rule is determined based on the minimum instantaneous comprehensive fuel consumption,and the mode switching strategy is obtained by combining the rule and considering the continuity of mode switching;Simulation tests on the fuel economy and acceleration performance of the designed transmission scheme and corresponding control strategy show that the fuel economy of the designed transmission system is improved by 4.14% compared to the original vehicle transmission scheme,and the overall acceleration performance is improved.