Relaxed hover solutions for multicopters: Application to algorithmic redundancy and novel vehicles

• Published in: The International journal of robotics research Vol. 35; no. 8; pp. 873 - 889
• Main Authors: Mueller, Mark W., D’Andrea, Raffaello
• Format: Journal Article
• Language: English
• Published: London, England SAGE Publications 01-07-2016; SAGE PUBLICATIONS, INC
• Subjects: Aerodynamics; Algorithms; Angular velocity; Center of mass; Computer simulation; Constants; Controllability; Design engineering; Failure; Gravitation; Offsets; Propellers; Redundancy; Vehicles; hover; failsafe; Multicopter; quadrocopter; control; flying robot; center of mass
• ISSN: 0278-3649; 1741-3176
• DOI: 10.1177/0278364915596233

This paper presents a relaxed definition of hover for multicopters with propellers
pointing in a common direction. These solutions are found by requiring that the
multicopter remain substantially in one position, and that the solutions be constant when
expressed in a coordinate system attached to the vehicle. The vehicle’s angular velocity
is then shown to be either zero or parallel to gravity. The controllability of a vehicle’s
attitude about these solutions is then investigated. These relaxed hover solutions may be
applied as an algorithmic failsafe, allowing, for example, a quadrocopter to fly despite
the complete loss of one, two, or three of its propellers. Experimental results validate
the quadrocopter failsafe for two types of failure (a single propeller and two opposing
propellers failing), and a nonlinear simulation validates the remaining two types of
failure (two adjacent and three propellers failing). The relaxed hover solutions are also
shown to allow a multicopter to maintain flight in spite of extreme center of mass
offsets. Finally, the design and experimental validation of three novel vehicles is
presented.