The Switching Control Strategy Of Plug-in Hybrid Electric Vehicle With Reflux Power Continuously Transmission System

The reflux power plug-in hybrid electric vehicle(R-PHEV)is a new type of hybrid transmission configuration.As a novel structure with a good prospect for development compared with the traditional CVT transmission system,it has the characteristics of wide transmission range and can improve the fuel economy and emission performance of the PHEV.There are two main problems in the power switching condition: The fluctuation between the power sources switching and the power flow direction sudden change during the switching between power reflux situation and CVT situation.Both problem aforementioned will cause the sudden change of the output torque and eventually affect the harshness of the vehicle.To solve the problem caused by mode switching,the research work is carried out as followings:(1)The special configuration of the power coupling system is introduced in detail.The reflux power transmission working principle is analyzed and explained in this paper.The working characteristics and efficiency characteristics of the reflux power coupling system is listed and according to these features the parameters of the vehicle are matched.In addition,the characteristics of its key component including the engine,motor,wet clutch and electronic control CVT are researched and the relevant mathematical model is also established at the same time.(2)According to the energy management strategy of the reflux power plug-in hybrid electric vehicle,the torque distribution law of different power source under different working modes is listed.The key process of the mode switching is studied in detail,and the whole mode switching process can be defined as two types: driving mode switching caused by the change of working states between engine and motor and speed regulation mode switching caused by the change of working states between reflux power mode and continuously variable transmission mode.Choosing the jerk of the vehicle as the evaluation parameter to characterize the smooth of the vehicle.The dynamic analysis of the two types of the mode switching process is carried out concluding the main factors affecting the torque fluctuation in each process.(3)Based on the dynamics analysis,the coordination control policy is put forward for mode switching process and the key components are controlled macroscopically,such as the engine throttle opening rate control and the clutch oil pressure rate fuzzy control.As for micro level,different coordination control strategies are implemented for different switching processes.For driving mode switching,the specific switching can be divided into three sub-categories.For the switching process with starting engine,a phase engine speed overshoot and motor torque compensation control strategy is adopted in this stage.When closing engine driving mode switching occurs,the control strategy of engine throttle and clutch disengagement is used,and the motor torque is followed to compensated.In the switching between the working mode with engine involved,the motor is used to compensate engine torque.For the speed control switching,it mainly refers to the switching process between reflux power mode and pure CVT mode,the clutch torque change ratio control strategy is proposed in this situation.(4)The forward simulation model of the reflux power plug-in hybrid electric vehicle is built.For the common working conditions such as cruise control,acceleration and variable speed ratio,the process of mode switching is analyzed by MATLAB/Simulink respectively.The main causes of the jerk in different parts and parameters influence are studied.Finally,the effectiveness of the control method is verified by simulation analysis.