Reduction of the head-up pitching moment of small quad-rotor unmanned aerial vehicles in uniform flow

Multi-rotor unmanned aerial vehicles are unstable in headwind because of nose-up pitching moment generation and thrust degradation. Reducing the pitching moment generation could enhance the tolerance of the unmanned aerial vehicles to wind and improve cruise flight speed. In this study, a canted rotor configuration was proposed to reduce the moment in uniform flow and examined. The objective of the study is to evaluate the effect of moment reduction by canted rotors. First, flow interactions between rotors of the quad-rotor were visualized using a smoke wire method. Second, the moment reduction by canted rotors was estimated based on isolated rotor performance. Third, the moment of the quad-rotor varying the body pitching angle was examined using a wind tunnel. At an 8 m/s wind, when the body pitching angle is horizontal, slanting the rotor by 20° to outside the body degraded the moment by 26% compared with the parallel rotor configuration.