Vibration/Noise Reduction in Multi-Rotor Drones Using Optimal Phase Synchronization Method

Abstract

Using drones for various purposes has sparked concerns about the noise they create. There are several techniques to mitigate the drone noise such as propeller geometrical changes, material modifications, and active control using additional speakers. Recently the concept of phase synchronization with multiple propellers has drastic effect in reducing drone noise. In phase synchronization, the rotors are turned at the same rpm yet have a clear angular phase difference in position. If the angular phase difference is properly adjusted, the noise waves or vortices generated by every rotor destructively interfere with themselves. This makes the total noise from the drone decrease remarkably, particularly at the dominant frequency of the blade passing and its harmonics. This paper presents a comprehensive approach to reducing the noise/vibration produced by drone propellers without affecting the thrust. By considering the overall dynamics of the quadrotor drone with phase differences in thrust produced by each rotor, initially, the vibration responses are obtained numerically. The amplitudes of vibration in yaw direction are further minimized by setting the optimum relative phase angles subjected to a minimum thrust constraint. The dynamic response and noise levels of the effective phase angle configuration are finally reported.