Comparative Study On Energy Efficiency Of Phev With CVT Or DCT

In order to improve the problems of the increasing fuel consumption and environmental pollution caused by the automobile,governments of various countries are introducing more and more strict emission regulations.Plug-in hybrid vehicles(PHEV),within a certain range of driving range,like the pure electric vehicles,can reduce the pollution by providing the energy required for driving by power batteries.when it is difficult to achieve the high driving range by power batteries,it can be realized by fuel-electricity hybrid drive for PHEV,and compared with a traditional vehicle,the consumption of fuel is reduced.Like traditional vehicle with internal combustion engines,PHEV usually needs to carry a gearbox to adjust the working state of the engine so as to obtain better energy consumption and economy.At present,there are some types of gearboxes that can be mounted in PHEV.Under different configurations and cycle conditions,it is difficult to directly determine which gearbox is superior in energy economy.In order to determine which of CVT or DCT can obtain better energy consumption economy for a PHEV in the project,the following work has been done in this paper.(1)Analyzing the configuration of a certain type of PHEV,determining the six working modes of PHEV.(2)Analyze the state and energy flow direction of engine,motor and other components under each working mode.Establish the efficiency model of the whole vehicle system under each working mode.According to the usage characteristics of Plug-in hybrid electric Vehicle power battery,energy management is divided into CD stage and CS stage.The division process of range for working mode based on the optimal system efficiency is formulated.Based on the m programming language of Matlab,the system efficiency model of the whole vehicle in each working mode is combined with the working mode division process,and a regular energy management strategy based on the optimal system efficiency when PHEV is equipped with CVT or DCT is formulated.The energy management strategy includes the range of working mode and component assignment actions which are transmission ratio assignment,engine torque distribution and motor speed assignment.(3)This paper analyzes how to apply reinforcement learning to optimize the regular energy management strategy with the system efficiency,and establishes a model of reinforcement learning algorithm to optimize the energy management control strategy.Considering the relationship between grid size of agent for reinforcement learning and training speed/energy consumption economy,a grid size with better comprehensive effect is set according to the operation results.As an example,With an optimized energy management strategy,the energy efficiency of the plug-in hybrid vehicle with CVT or DCT is improved.(4)Comparing the energy consumption economy of PHEV when carrying CVT or DCT under 21 operating conditions.A method of constructing decision tree based on comparison results and driving cycle characteristics is proposed,which is used to analyze the correlation between driving cycle characteristics and which gearbox of PHEV carrying CVT or DCT has better energy consumption and economy.The analysis results show that the plug-in hybrid vehicle should be equipped with DCT to obtain better energy consumption economy under urban conditions;when the working speed is high and stable(such as suburban conditions),plug-in hybrid vehicle It tends to be equipped with DCT to obtain better energy consumption economy;Under medium-high speed conditions and frequent acceleration and deceleration(such as the WLTC test cycle conditions adopted by the National VI standard),plug-in hybrid vehicles should be equipped with CVT to obtain better energy consumption economy.