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

Abstract

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.

Control of statically hoverable multi-rotor aerial vehicles and application to rotor-failure robustness for hexarotors

“…the surrounding environment. The same does not hold for a platform in dynamic hovering (see [7]) as explained in the Introduction.…”

“…For static hoverability we instead mean that the platform is able to keep a constant position and a constant orientation without rotating around any axis. Relaxed (dynamic) versions of the hovering concept have been recently introduced in [7]. Those solutions represent a valuable resource as last resort methods to attempt saving the platform from catastrophic damages.…”

ARDEA—An MAV with skills for future planetary missions

“…Fail‐safe robustness is achieved by adding redundancy to the propulsion system and failure detection and handling in the control software. In Michieletto, Ryll, and Franchi, 2018 and M. Müller and D'Andrea (2014, 2016) suitable system designs for motor redundancy and necessary control strategies to handle motor faults are discussed. We discuss this aspect of our system design in Section 4.1.1.…”

Fault tolerant control of a quadrotor using C 1 adaptive control

“…The consequence of the loss of a complete e↵ector and the subsequent loss of control of a degree-of-freedom also needs exploring. The question of whether this scheme can be extended to maintain control over fewer degreees-of-freedom in a similar manner to Mueller and D'Andrea [2015] is an open one.…”

“…The question of tolerance to failure of a quadrotor actuator/e↵ector has been addressed previously. Maintaining hover while losing control of one degree-of-freedom (notably yaw) is an approach considered by, for example, Mueller and D'Andrea [2015] [see also Mueller and D'Andrea, 2014] and by Lanzon et al [2014]. Control allocation methods that use actuator redundancy in hexrotor or octorotor arrangements have been proposed by, for example, Adîr et al [2011], Marks et al [2012], Hamayun et al [2015] and .…”