In-water and in-air vehicle velocity estimation via harmonic and Doppler analysis

Abstract

Remotely-controlled (RC) vehicles, such as RC cars, boats, planes, and drones, use high energy-density lithium polymer batteries that enable powerful brushless DC motors to propel them at remarkable velocities. In prior work, measurements of the acoustic emissions from such motors on RC cars have been processed to estimate vehicle velocity, based on a spectral analysis of the emissions, together with a parametric model for the acoustic emissions, relating them to motor speed and vehicle velocity. This work builds on prior models for the acoustic emissions of the DC motors to estimate the motor speeds for in-water and in-air craft, including RC boats and drones. Spectrograms of the acoustic recordings of the vehicles at moving at constant velocity provide sufficient harmonic structure to effectively measure the Doppler shift at closest point of proximity, enabling vehicle velocity estimates. These, in turn, enable calibration of the harmonic structure for motor speed estimation. Preliminary results demonstrate the correlation between the speed profile of the vehicle, acoustic harmonic structure, and Doppler shift.