Research On Torsional Vibration Of Driveline For Hybrid Electric Vehicle

The vibration and noise problems of vehicles with hybrid drive are more complicated than those of the conventional vehicles, which have significant impacts on the NVH quality of the hybrid electric vehicle. The research on the characteristics of the torsional vibration on the driveline of vehicle has great theoretical and practical values.In this research, a dynamic model of the compound planetary gear sets and the whole transmission system are established respectively for the free and forced torsional vibration analysis of the Hybrid Electric Vehicle(HEV).The dynamic parameters of the components of the driveline are calculated. “Ravigneaux” gear set is applied in this transmission system. So the modeling of the compound planetary gear set is the most important part of the whole driveline system.Natural vibration characteristics are composed of natural frequency and vibration mode which have significant impacts on dynamic response and vibration forms. Through the analysis and calculation of natural frequency and vibration mode, the vibration modes of the driveline system under hybrid electric condition and pure electric condition are obtained, which provide the theoretical basis for the dynamic characteristic analysis of the driveline system. On basis of the calculation the natural frequency, resonant speed of the powertrain was optimized through the stiffness matching of torsional damper. The analysis results indicate that the resonant speed can be reduced out of the engine idling speed range by decreasing the stiffness of the torsional damper. Besides, the amplitude-frequency and phase-frequency characteristics of the driveline system are analyzed.The forced torsional vibration of the driveline model is simulated in ADAMS. In this paper, the dynamic model of the compound planetary gear set is established by adding virtual gears. The studies focus on the driveline system parameters change on the dynamic characteristics, including damping coefficient and stiffness of the torsional damper, moment of inertia of the flywheel, damping coefficient and stiffness of axle shaft and torsional stiffness of the wheels. Besides, the time domain responses of the components of the driveline are respectively analyzed under hybrid electric condition and electric condition.For the purpose of determining the noise excitation source, the acoustic test of the powertrain is needed. Comparing with the results of acoustic test, the natural frequency and vibration mode of the system are analyzed. It is demonstrated that the noise is mainly caused by the engagement of gear pairs. Moreover, numerical results show torsional vibration has a significant impact on the noise of transmission system.According to the results of the test and simulation, the influence manner and the influence degree on the driveline system of different parameters are discussed in order to find feasible solution to minimize the vibration and noise by optimizing some parameters.