Research On Dynamic Coordinated Control Of Start-up And Mode Switching Of P2.5 Plug-in Hybrid Power System

With the energy crisis and environmental pollution becoming more and more prominent,fuel consumption and emission regulations are becoming increasingly stringent,and the development prospect of new energy vehicles is broad.Due to the battery energy density,the "mileage anxiety" problem of Electric Vehicle(EV)is difficult to solve in the short term,Plug-in Hybrid Power System(PHPS)has more market-oriented advantages.Major automobile manufacturers have invested in the development of PHEV,and various PHPS have appeared in the market.At the same time,Dual Clutch Transmission(DCT)has the structural characteristics of dual clutch and dual input shaft,no power interruption in the process of start-up and mode switching,high transmission efficiency and other performance advantages,and the proportion of PHEV is increasing year by year.Hybrid power system can be classified in many ways,in which P(Position)represents the structure of electrified components and the relative position between motors.Combined with different number codes,the single motor hybrid power system is divided into P1,P2,P2.5,P3,P4 and other configurations.Based on the P2.5 plug-in hybrid power system(P2.5-PHPS)equipped with DCT,the motor is integrated into an input shaft of DCT.Compared with the P1-PHPS with the drive motor at the engine output and the P2-PHPS at the transmission input,the P2.5-PHPS has the advantages that the motor efficiency is not affected by the high temperature heat radiation of the engine,and the P2.5 drive motor torque can be directly driven by the transmission to start or drive,and the clutch can control the engine Compared with P3-PHPS and P4-PHPS,P2.5-PHPS optimizes the working range of the drive motor by using the variable motor speed ratio,improves the power output efficiency,does not need the low-voltage motor to start the engine and generate electricity,and has less impact of oil electric coupling.Therefore,this configuration has great application prospects and research significance with its many advantages.Taking P2.5-PHPS with DCT as the research object,this paper analyzes and studies the dynamic process of its start-up and mode switching(1)Based on the P2.5-PHPS with DCT,the characteristics and structure principle of the system are analyzed,the start-up and mode switching processes are established in multiple stages,and the corresponding dynamic equations are established.Considering the steady-state and dynamic characteristics of engine and P2.5 drive motor,as well as the torque transmission characteristics of wet clutch,the models of engine,P2.5 drive motor and wet clutch are established.At the same time,the vehicle longitudinal dynamics model is built according to the vehicle dynamics equation to form the P2.5-PHPS vehicle model framework.(2)Considering the operating conditions and the characteristics of power source,the starting types are divided into three categories: pure electric starting,engine starting and dual power source joint starting.According to the working state of wet dual clutch,engine starting can be divided into single/dual clutch starting and dual power source starting.The starting process analysis and corresponding dynamic equations are established in multi-stage.In order to improve the problem that the vehicle state can not effectively follow the driver’s starting demand in the starting process,a starting control strategy considering the driver’s starting intention recognition is proposed based on the starting process evaluation index.(3)Combined with the energy management strategy of hybrid power system,the demand torque of the whole vehicle is identified,the working mode area is divided and the output torque of power source is distributed.Considering the configuration characteristics and structural advantages,based on the working state of two wet clutches,the configuration mode switching types are divided into three categories: wet double clutch combination,wet double clutch separation and no wet double clutch action.The multi-stage mode switching process is established,and the corresponding dynamic equations are established.Combined with the evaluation index of mode switching process,the corresponding dynamic coordination control strategy of mode switching process is formulated.(4)Based on the above starting and mode switching control strategy,combined with MATLAB/Simulink,different starting and mode switching control strategy models are built and simulated offline.The simulation results of different starting modes and mode switching types are compared and analyzed.To verify the feasibility and effectiveness of the starting and mode switching control strategy of P2.5-PHPS based on DCT,and provide reference and basis for the control of P2,P3 and other hybrid systems.