Design and experimental verification of a hoverable quadrotor composed of only clockwise rotors

Abstract

This paper presents a novel structure for a quadrotor, making it hover only with clockwise rotors, where we denote it as a 4P (Positive) rotor. We first investigate the condition for a 4P rotor to hover. More specifically, we conduct the hoverability analysis, which is closely related to the controllability analysis, and show that the tilting angles of each rotor are crucial conditions for the hoverability of the 4P rotor. The derived condition for the tilting angles is then utilized to present two prototypes. Each prototype is developed with the following design purposes: One is to reduce the horizontal force generated by the tilted rotors, and the other is to make its torque generation the same as that of a standard quadrotor. The hoverability and dynamical property of both prototype is demonstrated in simulations and experiments.