Fault-tolerant Flight Control of a VTOL Tailsitter UAV

Compared to other vertical take-off and landing (VTOL) systems, a tailsitter minimizes the number of actuators and moving parts necessary. The downside of having a minimalistic actuation is its inherent low fault-tolerance. The failure of an actuator usually results in a loss of controllability, resulting in a crash. In this paper we analyze possible actuator failures and the constraints they pose on the capabilities of the system. We further present light-weight adaptations to the nominal flight controller to make it fault-tolerant. The fault-tolerant controller is implemented on a small tailsitter VTOL aircraft and adjusted to the system by means of extensive experimental studies. Finally, the capabilities and performance under failures are demonstrated and analyzed.