Surface Vibration Measurement and Analysis for UAM/UAS Electric Motor Noise

Urban Air Mobility vehicles are an emerging class of vertical lift vehicles using electric motors to drive multiple rotors for lift. The outrunner electric motors that are commonly used, may be capable of generating noise that could contribute to the vehicle’s overall noise profile and could generate cabin noise. Understanding and predicting the noise requires more knowledge of the rotor vibrations and eventually a model to predict the frequencies of those vibrations. This work presents a measurement of the rotor vibrations of two different small-scale motors. Two techniques to measure the surface vibration were used. The displacement spectra are compared with acoustic measurements. A finite element analysis model is used to predict the rotor resonance frequencies. The predicted frequencies are in fair agreement with the experimentally observed vibration frequencies, but requires further work to understand discrepancies.