Vibration characterisation of electric-vehicle electric drivetrain system under electromagnetic excitation and mechanical excitation coupling action

Electromagnetic and mechanical excitation are the main causes of electric drivetrain system (EDS) vibration. In this study, the vibration characteristics of an electric drivetrain assembly under electromagnetic-mechanical excitation coupling were investigated using a three-in-one EDS as the research object. A rigid-flexible coupling dynamic model of the EDS was developed to comprehensively analyse the electric motor, drivetrain, controller housing and bearings. Based on this, a finite-element model of a permanent magnet synchronous motor (PMSM) was developed to analyse the electromagnetic excitation in the EDS. Finally, the vibration response characteristics of different parts of the shaft system, bearing and housing of the EDS under electromagnetic-mechanical excitation coupling were analysed. The results indicated that the 24th and 48th-order electromagnetic excitations of the motor contributed considerably to the vibration of the system and that, with regard to mechanical excitation, the first-stage gear pair had a stronger impact on the system than the second-stage gear pair. The vibration response of the shaft system decreased in the following order: intermediate shaft > input shaft > output shaft > rotor shaft. The vibration state of each shaft bearing was consistent with that of the corresponding shaft system; on the assembly housing, the vibration was largest at the connection between the motor housing and the reducer housing. The findings of this study provide guidance for EDS noise, vibration and harshness (NVH) performance analysis and structural optimisation.