Parameter Optimization Of Transmission System And Research Of Energy Management Strategy For Power Split Hybrid Electric Vehicle

In the face of increasingly serious environmental problems,energy crises and stringent emission standards,many countries in the world have put great effort in the development of new energy vehicles.Our government has issued a series of policies and regulations to encourage the development and application of new energy vehicles.Due to inherit the advantages of the traditional vehicles and pure electric vehicles,Hybrid electric vehicle have good performance on mileage and emissions.Among them,the power split hybrid electric vehicle combines the advantages of series and parallel hybrid electric vehicle,uses a dynamic coupling mechanism which is based on planetary gear to decoupling the torque and speed between engine and wheel.The power split hybrid electric vehicle has multiple power output sources,the coordinate of power output for each power source to reduce the fuel consumption of vehicles is the key for hybrid power system can give full play to the advantages of configuration.Therefore,it is very important to design a good energy management control strategy which is based on the characteristics of the power split of the coupling mechanism and the efficiency characteristics of each power source.In this paper,a power split hybrid electric vehicle with double planetary row power coupling mechanism is regarded as the research object.The characteristic parameters of the transmission system are optimized and the optimal control strategy to improve the fuel economy of the vehicle is discussed by analyzing the operating characteristics of the hybrid system.Specifically,the research work is carried out from the aspects of the operating characteristics of hybrid powertrain,the matching and optimization of vehicle transmission system parameters,the optimal design of energy management strategy and the HIL simulation verification.As follows:First of all,the coupling mechanism was analyzed to reach the characteristic equation of dynamic coupling mechanism.Combined with the characteristics of hybrid system,the working mode of the vehicle is analyzed and the working mechanism of the vehicle is studied.On this basis,according to the principle and method of parameter matching of the power split hybrid electric vehicle,the selection and parameterization of each part of the vehicle is completed.Secondly,based on forward modeling theory,the vehicle longitudinal dynamics model and energy management control system model of the power split hybrid electric vehicle are established and the simulation model of the closed-loop system is built.Combined with the optimization software Isight,using NSGA-II optimization algorithm to optimize the characteristic parameters of the coupling mechanism and main reducer transmission ratio,which can further reduce the vehicle fuel consumption.Then,the paper introduces each subsystem components of the hybrid HEV energy management control strategy respectively.Based on the above theory,the engine optimal operating line(OOL)control strategy and instant optimization algorithm of equivalent fuel consumption minimization strategy are designed.In the OOL control strategy,the best optimal operating line of the engine is established and makes use of the motor to tuning the engine speed possibly to achieve the target speed.So as to obtain lower fuel consumption based on the certain power.In the ECMS control strategy,the electric energy consumption of hybrid power system is equal to the corresponding fuel consumption,and according to this,the instantaneous optimization objective function is established.Through searching the best equivalent factor,establishing the correction function to make sure the battery SOC is in the range of floating interval.In order to further improve the ECMS control strategy under different conditions of adaptive capacity,the paper elaborated another control strategy that is adaptive equivalent consumption minimization strategy which could change the equivalent factor with the vary of the battery SOC.The optimal initial equivalent factor and the renewal period of the A-ECMS control strategy are determined by searching for different initial equivalent factors and different update cycles.In order to highlight the effectiveness of A-ECMS control strategy,the paper compared the simulation results which are battery SOC change and equivalent fuel consumption between ECMS and A-ECMS based on NEDC cycle and UDDS cycle respectively.By comparing the simulation results,the adaptive minimum equivalent fuel consumption control strategy can control the battery SOC change better and get the lower equivalent fuel consumption.Finally,based on dSPACE simulation environment establishing the transfer simulation model and control strategy model individually,then,compiled and downloaded the model to the emulator.The two emulators made information interaction through the CAN line and hard line.The simulation result both proved the effectiveness of engine OOL and A-ECMS optimization algorithm which are lay a foundation for the practical development and application of vehicle controller.