| With the growing pollution of environment and the depletion of oil resource, the development of hybrid vehicles has become a trend. Hybrid electric vehicle has two power sources which are engine and motor. Hybrid electric vehicle has several working modes due to different combinations of their working states. According to the running state, the hybrid electric vehicle can do mode switching among the various working modes. At present, the theoretical study of the hybrid vehicle mode switching mainly focuses on the basis of the steady-state modeling. During the study, they ignore the influence of the dynamic characteristics of drive system components to the process of mode switch. However, in the actual vehicle driving, the dynamic characteristics of the drive system components will affect the process of the mode switching. Therefore, the mode switching control which considering the dynamic characteristics of the drive system is the key point of the mode switching theoretical study. In this paper, aiming at a full hybrid system with single motor equipped with DCT, the dynamic characteristics of the key components of the drive system has been studied in depth. The simulation model based on the dynamic characteristics of the drive system has been established and the dynamic control of the mode switching of the hybrid electric vehicle has been studied. The main contents are as follows:(1) The structural characteristics of the DCT full hybrid system are analyzed. The parameters of the whole vehicle and the drive system are presented. The average model which considering the dynamic characteristics of the engine is established, and a comparison between the experimental data and simulation results has been presented. The dynamic simulation model of ISG motor is established, and the torque response characteristics of ISG motor is simulated and analyzed. The torque accuracy is verified through the test. At the same time, the main clutch model, the battery model, the DCT model and the whole vehicle model have been presented which lays the foundation for the mode switching research.(2) The working principle and structure of the hydraulic system of the wet main clutch are expounded. The dynamic model of the high-speed switch valve and the clutch cylinder piston has been established respectively. The transfer function between the duty cycle of the high-speed switch valve and the control pressure of the clutch cylinder has been established. The dynamic characteristics of the high-speed switch valve and the clutch cylinder piston displacement have been analyzed by using the Matlab / Simulink software simulation platform.(3) The recognition of the driver’s torque requirement has been presented, and in order to make sure the target torque of the power source, a division of the working mode area has been given. The algorithms that limit the change rate of the target torque are used to control the engine, and the direct control mothod is used to control the motor. The clutch control has been divided into two stages by making the engine ignition time as a critical point, and different control algorithms for two stages have been put forward. On the basis of the dynamic analysis of three typical mode switch process, a coordinated mode switching control strategy has been proposed.(4)The mode switching simulation model has been built by using the Matlab / Simulink software simulation platform. A comparison of the simulation results between the dynamic modeling and the steady state modeling of the mode switching has been presented. At last, in order to verify the simulation results, the bench test has been carried out. The results show that the model switch simulation results under dynamic modeling can better reflect the dynamic characteristics of the drive system than the steady state modeling and have better consistency to the test results, which lay the foundation for perfecting the mode switching strategy and evaluating the mode switching quality. |
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