Hexacopter outdoor flight test results using adaptive control allocation subject to an unknown complete loss of one propeller

Adaptive Fault–Tolerant Position Control of a Hexacopter Subject to an Unknown Motor Failure

“…The main advantages of this strategy are the following: (a) a unified controller handles the nominal, the degradation and the failure cases; (b) it exploits the full attainable moment set avoiding saturations whenever possible; (c) finally, it is possible to implement a degraded control strategy in order to prioritize specific virtual controls in the case of extreme degradation. This paper extends our previous results (Falconí et al, 2016) with mainly three contributions: (a) extension of the attitude controller to a position controller maintaining the fault tolerant properties; (b) improvement of the control effectiveness estimates by introducing the null space shaping approach; (c) outdoor GPS-based flight tests including failure scenarios. To the best of our knowledge, this paper presents the first outdoor flight tests of a position tracking controller of a hexarotor subject to an unknown failure of any of the six propellers.…”

“…2. The extension of the attitude controller from the work of Falconí et al (2016) to a position controller which maintains the fault tolerant properties is a main contribution of this paper. In the following sections the two controllers are derived.…”

“…2: the online optimization-based control allocation and the adaptive effectiveness estimation. The following results are based on the findings of Falconí et al (2016) and are applied here to the position tracking controller in order to exhibit fault tolerant properties. Furthermore, the control effectiveness estimates are improved by introducing the null space shaping approach, which is a main contribution of the paper.…”

“…Most of them are partial results showing only failure detection and identification (Freddi et al, 2014), or only controller reconfiguration assuming that the fault has been already identified (Achtelik et al, 2012;Du et al, 2015;Schneider et al, 2012;Santos et al, 2015), or using external sensors for having an accurate position measurement (Amoozgar et al, 2012;Dydek et al, 2010;Mueller and D'Andrea, 2014;Saied et al, 2015;Vey and Lunze, 2016), or making computations off-board (Dydek et al, 2013). Furthermore, in the special case of the hexarotor, the controllers are applied to different levels of actuator faults: only degradation (Heise et al, 2014;Mühlegg et al, 2015), the total failure of one rotor excluding a group of rotors (Vey and Lunze, 2016;Yang et al, 2016), the total failure of any rotor (Falconí et al, 2016) and the total failure of more than one rotor (Mueller and D'Andrea, 2014). The complexity increases with each of these cases because after a rotor failure the set of attainable forces and moments is noticeably reduced and saturations become an issue.…”

“…This includes handling unknown degradation and failure of any rotor, outdoor GPS-based flights and onboard computation of the algorithms. In our previous work (Falconí et al, 2016), we presented a fault tolerant attitude controller based on adaptive control allocation which consists of the estimation of the actuator control effectiveness and an optimal control allocation. The main advantages of this strategy are the following: (a) a unified controller handles the nominal, the degradation and the failure cases; (b) it exploits the full attainable moment set avoiding saturations whenever possible; (c) finally, it is possible to implement a degraded control strategy in order to prioritize specific virtual controls in the case of extreme degradation.…”