Implementation of a "Clear Prop!" Function in Propulsion Inverter of Electric Aircraft

The unmanned aerial vehicles and aircraft electric propulsion systems use propellers to create a lifting force or thrust. Over last years their penetration in our life is growing with the quadcopters for photography and filming, delivery services, and other applications. This rases a problem of safety when starting the propellers, and many solutions use sound generation by the propulsion motors to attract attention of human and warn him from being harmed by the blades. This sound is replacing the command "Clear Prop!"—a phrase said before a propeller is starting up by the pilot to ensure there is no one in the area of the propeller. The sound is generated by feeding the motor windings with some current having frequency in the audible range prior to start of the motors. This paper considers two implementations of the sound generation using melody and recorded sound. The melody is defined by notes or tones and their durations, and the sound is recorded as 8-bit mono pulse-code modulation data. The algorithms for implementation are presented as well as samples of the sound playback.