The Development of a Method for NVH Prediction in Electrical Driving Systems Using a Quasi-Transient Excitation Force

Most motor vibrations are generated by excitation forces such as torque and switching ripples that are amplified at the mechanical resonance frequency. Both electromagnetic and structural vibration analyses should be used to accurately predict these vibrations. In this study, an analysis method that can simultaneously consider the excitation forces and vibration characteristics is proposed. The switching ripple was obtained from a 1D analysis model that included inverter and motor elements, while the motor torque ripple was extracted from a 2D electromagnetic analysis. To express the transient characteristics as the frequency of the excitation force increase when the vehicle accelerates, the excitation forces obtained in a steady state were converted into quasi-transient excitation forces using a sine sweep function which is newly suggested in this paper. For the vibration response characteristics of the motor, the transfer function between the excitation position and the response point of the motor was derived through structural analysis using the 3D finite element method. Using the quasi-transient excitation force and the transfer function obtained in the frequency domain, it was possible to establish a method for simultaneously representing the vibration characteristics due to resonance and excitation forces such as torque and switching ripples.