Noise of personal e-mobility device - case of self balancing unicycles and scooters

Summary of e-NVH sound sample
Application Inmotion® two-wheel and one-wheel self balancing unicycle, Segway® two-wheeled self-balancing scooter
Electrical machine Unknown
Supply condition Run-up at max torque
Noise sources Electromagnetic, mechanical
See also

Measurement set-up

Noise is measured 40 cm away from the electric powertrain. A run-up is done with maximum torque up to 20 km/h. The following e-mobility device are tested:

Two-wheeled self balancing unicyle from InMotion<sup>®</sup>
Two-wheeled self balancing unicyle from InMotion®
Self balancing unicyle from InMotion<sup>®</sup>
Self balancing unicyle from InMotion®
Two-wheeled self balancing scooter from Segway<sup>®</sup>
Two-wheeled self balancing scooter from Segway®

Sound file and spectrograms

Sound measured on a two-wheeled self balancing unicyle from InMotion<sup>®</sup> during run-up
Sound measured on a two-wheeled self balancing unicyle from InMotion® during run-up
Sound measured on a self balancing unicyle from InMotion<sup>®</sup> during run-up
Sound measured on a self balancing unicyle from InMotion® during run-up
Sound measured on a self balancing scooter from Segway<sup>®</sup> during run-up
Sound measured on a self balancing scooter from Segway® during run-up

Note: these sound files are the property of EOMYS; for authorized use in presentations, website, publications or technical work, please contact us

E-NVH interpretations

These sound files illustrate electromagnetically-excited noise of different personal e-mobility device. Besides low frequency gravel noise due to tyre/road interaction, one can hear whine noise due to slot/pole Maxwell force harmonics. A second source of electromagnetic noise comes from PWM effects. On InMotion systems, the PWM switching frequency is set quite high (15 kHz) so its effect might not be heard by the driver. On the contrary, PWM effects are clearly audible on the Segway due to lower switching frequency (8 kHz), increasing significantly sound roughness.

Application to MANATE

MANATEE software can be used to quickly calculate NVH due to electromagnetic forces both in early design and detailed design phase, including PWM and slotting effects.

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