Real-Time Sound and Vibration Modelling for Electric Motor 2021-01-1081

The replacement of the ICE engine with an electric motor has led to a significant reduction in vibration and noise. The characteristics of the electric motor as part of the powertrain still need consideration from an NVH perspective, as there are still two highly tonal components generating noise to the cabin, albeit at higher frequencies. The radial electromagnetic force causes a structural vibration on the casing which changes with motor speed and can be used to indicate vehicle speed. The current excitation causes a primarily tangential force on the poles of the motor at a specific frequency, but both are narrow band and can cause annoyance. The traditional approach to predicting the sound radiation of electric motors is usually based on finite element analysis (FEA). While this method has the capability to estimate the time response, it is computationally too demanding and does not allow for early investigations at systems level. To obtain the real-time sound and vibration data with a specified load condition, which will be used for quick motor design/integration, a rapid and widely applied model is needed. Hence, in this work, a simplified model has been established for analysing the permanent-magnet machine in MATLAB and Simulink, aiming to achieve the real-time estimation of the sound radiation due to the internal magnetic force. There are two stages in this model. In the first stage, the real-time internal magnetic force is calculated under both loading and unloading conditions in a simplified polar coordinate system with consideration of the stator slotting effect. A simplified structural mode l is generated using design data appropriate to an early motor design iteration, and the real-time sound radiation profile is estimated by the modal superposition model. The motor stator system in this stage is considered as a simplified shell with equivalent mass, stiffness and damping.