Fail-safe flight: Tilt control for quadrotors under rotor failure

This paper presents an integrated proportional–integral–derivative and Lyapunov based control, along with an active fault tolerant control system, for the control of a quadrotor in the event of a completely failed rotor. The proposed approach utilizes four tilting mechanisms to not only prevent collisions and crashes following a rotor failure, but also to return the quadrotor to its original flight path and successfully complete its mission, even during complex maneuvers. The dynamical model of the quadrotor, including the tilting actuators and control inputs, is first derived using the Newton–Euler method. A control strategy is then designed to enable a fault detection and isolation unit to accurately detect rotor failure and redirect the controller pathway accordingly. Various rotor failure scenarios and case studies are subsequently presented to demonstrate the efficiency and performance of the proposed approach in comparison with conventional methods.