  In this paper, a reconfigurable control scheme for a generalized class of
multicopters is presented to overcome single or multiple rotor failures. In a
multicopter, the rotor failure heavily affects its dynamics and thus its
controllability. Limited controllability leads to limited or no
reconfigurability. \emph{Available Control Authority Index} has been recently
developed \cite{Du2015} as a measure of controllability of multicopters. In
this work, the notion of \emph{Available Reduced-Control Authority Index}
(ArCAI) is introduced, which shows that in some uncontrollable failures it is
still possible to control reduced set of states. Based on this notion, a
reconfigurable control scheme is presented, which comprises a \emph{Nonlinear
Dynamic Inversion} based baseline control law, a constrained control allocation
scheme along with some modifications to incorporate reconfiguration, and a
simplified fault detection and isolation technique. Simulation results for a
commonly used configuration of Hexacopter are presented in the presence of
single and multiple rotor failures.
