Structural Vibration Analysis and NVH Trouble Shooting for an Electric Drive System 2021-01-0703

Compared with the traditional vehicle drivetrain system, the electric drive system is characterized by one or two transmission ratio, higher maximum speed and faster torque response. Therefore, NVH problem of electric drive system is more complex. In the development of electric drive system, NVH problems caused by structural vibration, especially the torsional vibration, are easy to occur and difficult to solve.

The purpose of this study is to further study the structural characteristics of the electric drive system and its response characteristics under various vibration excitations. The research object is an electric drive system under development, which adopts two-stage and fixed ratio transmission, the maximum speed is 12000 rpm. In the on-vehicle test, an unbearable noise has been found in this system under certain running condition. According to the NVH measurement result, this noise was caused by the system resonance at a certain frequency. In order to find out which structure is responsible for this resonance, modal analysis was performed on this system via both of simulation and test. According to the analysis result, none of the modal frequency of the assembly or its component was close to the resonance frequency. Next, to verify whether the resonance is caused by the torsional vibration mode of the system, a multi flexible comprehensive coupling model was built to accurately predict the torsional vibration characteristics of the electric drive system. This analysis results indicated that a system torsional vibration modal exist near the resonance frequency.

In order to solve the problem caused by the torsional vibration, optimization measures are developed from the excitation source, transmission path and responder. After considering the optimization effect, engineering cost and other factors, the final optimization scheme focuses on the excitation source, that is, the second gear. With the aid of micro modification of the gear teeth, the torsional fluctuation of the gear meshing excitation was improved, and thus the resonance was also solved on vehicle.

The results of this study, which have strong practical guiding significance, can be used as a reference for the design and development of E-drive system.