Pitching Moment Caused by Rotor Flow Interference on a Small Quad-rotor Unmanned Aerial Vehicle in a Uniform Flow

Abstract

Multi-rotor unmanned aerial vehicles (UAVs) are used in various applications because they can hover and take off and land vertically. Although they are useful for civilian applications, their cruise flight speeds are limited owing to the generation of a pitching moment in a uniform flow. However, aerodynamic forces acting on multi-rotor UAVs have not been precisely examined. The effects of the body-yaw angle, body-pitch angle, and distance between rotors on the pitching moment and thrust in a uniform flow are important considerations when designing UAVs. Furthermore, rotor flow interaction can affect the rotor performance in horizontal flight. The objective of the present study is to examine the thrust and pitching moment of a quad-rotor UAV in a uniform flow using different configurations. First, the rotor thrust and pitching moment on two rotors were measured while changing the relative rotor positions in a wind tunnel. Second, the thrust and moment of a quad-rotor UAV were measured at different yaw directions, pitch angles, and rotors distances. Experiment results clarify that maintaining the yaw direction in a plus configuration, rather than an X configuration, with regard to the flow direction can reduce the pitching moment.