Local controllability and attitude stabilization of multirotor UAVs: Validation on a coaxial octorotor

This paper addresses the attitude controllability problem for a multirotor unmanned aerial vehicle (UAV) in case of one or several actuators failures. The small time local controllability (STLC) of the system attitude dynamics is analysed using the nonlinear controllability theory with unilateral control inputs. This analysis considers different actuators configurations and compares their fault tolerance capabilities regarding actuators failures. Analytical results are then validated experimentally on a coaxial octorotor. A stabilization control law is applied on the coaxial configuration under one, two, three and four motors failures, when the system is controllable. Real-time experimental results demonstrate the effectiveness of the applied strategy.