  This paper develops a novel physics-based approach for fault-resilient
multi-quadcopter coordination in the presence of abrupt quadcopter failure. Our
approach consists of two main layers: (i) high-level physics-based guidance to
safely plan the desired recovery trajectory for every healthy quadcopter and
(ii) low-level trajectory control design by choosing an admissible control for
every healthy quadcopter to safely recover from the anomalous situation, arisen
from quadcopter failure, as quickly as possible. For the high-level trajectory
planning, first, we consider healthy quadcopters as particles of an
irrotational fluid flow sliding along streamline paths wrapping failed
quadcopters in the shared motion space. We then obtain the desired recovery
trajectories by maximizing the sliding speeds along the streamline paths such
that the rotor angular speeds of healthy quadcopters do not exceed certain
upper bounds at all times during the safety recovery. In the low level, a
feedback linearization control is designed for every healthy quadcopter such
that quadcopter rotor angular speeds remain bounded and satisfy the
corresponding safety constraints. Simulation results are given to illustrate
the efficacy of the proposed method.
