| Having both merits of traditional vehicles and electric vehicles,hybrid electric vehicles(HEV)plays a leading role in current automotive industry.As an essential part in the coupling of internal combustion engine(ICE)with electric machine,the transmission exerts great impact on the fuel economy,dynamic performance and drive-ability of HEV.Dual-clutch transmission(DCT)with its excellent efficiency,power shifting and low cost,shows great potential in its application to HEV.This paper focuses on the study of shift schedule and shift quality of DCT for HEV.Specific work completed are as follows:First,the concept and the development of HEV and DCT,the advantage of DCT's application to HEV,as well as the types of hybrid powertrain combining DCT,were briefly introduced;the principles and configuration of DCT and its key components were discussed and formulated.Second,based on certain parallel HEV,output torque model and efficiency model of its ICE and electric machine were analyzed and built respectively,through testbed testing;then the completed vehicle model was built on AVL-Cruise.Third,through the studying of the logic threshold energy management strategies,the working modes and torque distribution rules of the HEV,the concept of comprehensive efficiency was proposed,and then a new shift schedule taking into account of engine torque,speed and motor torque,was put forward to improve the fuel economy of HEV under different working modes.By conducting simulation on Cruise and Simulink,the effectiveness of the proposed shift schedule was verified.Finally,based on the analysis of the shift process of DCT,and the factors affecting shift quality,a new shift control strategy of utilizing ISG to reduce the speed gap between driving and driven parts of clutches was proposed,aiming at reducing the friction work and the jerk during shifting;simulation results of the strategy demonstrates that the proposed control strategy could effectively improve the shift quality of DCT. |
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