Abstract:
Numerical optimizations of small rotors for multicopter UAS are presented using blade element momentum theory as the objective function. Total power required is minimized by allowing the chord distribution, twist distribution, and rotor rotational speed to vary subject to several geometric and performance constraints. The region of the global minimum of the objective function is found using the non-gradient-based genetic algorithm NSGA-II, at which point a gradient-based method is used to refine the solution. Two design cases are presented. The first is for sea-level hover of a nine inch diameter rotor intended for use on small multicopter UAS. The second is for high-altitude hover of a larger rotor. Optimized designs for the first case operating at the same thrust required twenty-nine percent less power than a baseline rotor. The power savings associated with a large maximum allowable chord length is found to be very small.