Modal analysis of different drivetrain configurations in electric vehicles

This paper presents a modal analysis of different drivetrain configurations in electric vehicles; 1) an in - wheel motor, 2) direct drive, and 3) an electric motor with a reduction gear and a differential gear. A specific simulation model was developed to analyze the vibrations while taking into account the traction motor, possible mechanical reduction gears, and the driveshaft, as well as a Rigid Ring Model (RRM) to describe the tire. On the basis of the simulation results, the frequency responses were calculated for each drivetrain configuration and also for a non-drive, free-rolling tire. The analyzed results show interesting differences between the different drivetrain configurations. However, most of the negative aspects can be compensated for if identified in the early design phase. For instance, the frequency response of the in-wheel motor configuration indicated that the vibrations that occur might cause negative effects in terms of driving comfort and wheel speed signal noise. The direct drive configuration has an additional mode at 24Hz, and the differential configuration at 4 Hz. It is possible that these modes would resonate strongly if some drivetrain design parameters were poorly defined.