Motor noise reduction of unmanned aerial vehicles

Abstract

The noise of multi-rotor unmanned aerial vehicles (UAVs) mainly comes from high-speed rotating propellers and brushless direct current motors. With extensive research on the generation mechanism and suppression methods of propeller noise, fruitful results have been achieved on the noise reduction of propellers. Therefore, the noise radiated by UAV motors has received more attention in recent years. In this paper, the noise of the motor of a small quadrotor UAV is reduced by a composite sound-absorbing structure that couples a cylindrical micro-perforated panel absorber (MPPA) with a carbon fiber porous material. The cylindrical MPPA adopts an open design to balance its noise reduction performance and heat dissipation performance. To more realistically reproduce the actual working state of the motor, different shapes of motor loads were designed and manufactured to simulate the propeller. The noise reduction experiment of the UAV motor is carried out in a semi-anechoic chamber. The experimental results show that the composite sound-absorbing structure designed in this paper can effectively reduce the noise of UAV motors and has a good heat dissipation effect. In addition, a custom-made composite sound-absorbing structure was installed on a quad-rotor UAV, and field experiments were carried out. The results of field experiments show that the composite sound-absorbing structure designed in this paper has good practicability to absorb the noise of UAV motors, and this work can provide a reference for the design of silent UAVs in the future.