Research On A Design Methodology For Mutli-mode Hybrid Electric Vehicle Powertrain With Planetary Gear Sets

As an important development direction of new energy vehicles,hybrid electric vehicles(HEVs)have outstanding energy saving potential and powerful operation control ability,which is an effective solution to energy shortage and environmental pollution.Its energy saving and emission reduction potential mainly depends on the mechanical connection mode of each component,the instantaneous power distribution strategy between component parameters and each power source,that is,it depends on configuration and energy management.The configuration of hybrid electric system(HES)is the basis of energy management.It determines the algorithm selection of energy management and optimization potential,as well as its working mode and power distribution strategy,which directly affects the vehicle’s dynamic performance and fuel economy.Therefore,the innovative design and optimization of configuration is the key to improve the comprehensive performance of HEV.At present,the HES with planetary gear sets(PGs)has been widely studied and applied because of its compact structure and high transmission efficiency.However,with the increase of its operation mode,the number of power sources,clutches,brakes and PG required is increasing.Moreover,it is very difficult to design and screen the novel HEV configurations due to the random and diverse connection forms between above components.This paper takes the multi-mode HES with several PGs as the research object,and relies on the excellent talents support program project of chongqing university "Research on real-time control mechanism of decentralized adaptive energy management of plug-in hybrid electric vehicles",and conducts the following research:(1)Based on the tree characteristics of clear structure and distinct hierarchy in nature,an equivalent tree graph method is proposed to describe multi-mode hybrid electric vehicle powertrain with planetary gear sets.As a result,the equivalent tree graph models are extracted from the HEV configurations with single,double,and multi-planetary gear sets.Moreover,the tree models are divided into several fragments after analyzing its characteristics.And the fragments obtained are classified and saved in the corresponding tree library,which is convenient for subsequent selection.(2)By analyzing the hierarchical relation of trunk,branch and leaf in the tree graph,the main components are coded and the tree diagram is further transformed into a matrix.The automatic generation of the configuration is completed according to the equivalent tree library.And a certain number of HEV configurations with single,double,and multi-planetary gear sets are finally obtained under certain constraints.(3)A class of configurations in the obtained multi-mode hybrid electric system with single-PG are selected and the subsequent selection process is analyzed completely.According to the operation modes of the configuration with the most number of clutches and brakes,its mode shift rules are established and the minimum mode shift rule diagram is proposed.Considering the mode switching rules and the actual parameters of each component,this kind of configuration is screened and the effective configuration is obtained.(4)All effective mode switching rules are developed for the screened configurations,and the fuel economic is analyzed in combination with the minimum equivalent fuel consumption strategy.Meanwhile,the mode switching strategy is reanalyzed to delete the invalid and redundant modes,so as to optimize their configurations and reformulate the minimum mode shift rule diagram.To achieve the configuration optimization and obtain the optimal configuration,its performance is analyzed and compared with general HES under various operation cycles.