A direct drive solution for contra-rotating propellers in electric unmanned aerial vehicle

In this paper a solution is proposed for contra-rotating propellers in electric unmanned aerial vehicles. It is based on a direct drive system where the contra-rotating blades are directly fixed on the rotors of an axial-flux permanent magnet motor. The latter one is constituted by two external rotors and a single internal stator divided in two different sides. The study is focused on a 6 slots-4 poles three-phase motor and on a 10 slots-4 poles five-phase motor, characterized by single-layer armature windings. For each motor configuration some sets of motor sizes are found by using an automatic calculus procedure and by imposing suitable electrical, thermal and mechanical constraints.