Noise prediction of multi-rotor UAV by RPM fluctuation correction method

Abstract

The multi-rotor type unmanned aerial vehicle (UAV) controls the movement through the rotational speed of each rotor. Since the phase of each rotor is different and minute variations of the rotational speed are always accompanied during flight, frequency modulation of the drone noise occurs. In this study, a new approach, called the rotation per minute (RPM) fluctuation correction method, was developed to consider the frequency modulation effects through correcting the signals predicted by the classical rotorcraft noise prediction methods. For verification of the suggested method, two experiments were performed for a single isolated rotor and a full vehicle. The measured spectra of the isolated rotor were used for verifying the spectrum before the correction. Also, the spectra corrected by the RPM fluctuation correction method were compared and verified with the noise of the full vehicle, which has frequency modulation effects.