Fault-tolerant control of actuator failure combinations in quad-tilt rotor UAVs

This paper proposes a fault-tolerant algorithm for quad-tilt rotor unmanned aerial vehicles (UAVs), addressing the full set of actuator failure combinations involving both rotor spin and tilt mechanisms. Unlike prior studies that primarily focus on limited or symmetric fault cases, this work classifies all possible failure scenarios and evaluates their controllability through a numerical feasibility analysis using a control-feasibility function. Each case is categorized as fully controllable, partially controllable, or uncontrollable. A Lyapunov-based virtual control framework with slack variables is employed to ensure smooth transitions and stability under sudden faults. The proposed controller operates within a single unified architecture without requiring mode switching, making it practical for real-time applications. Simulation results validate the method’s effectiveness across diverse and complex failure conditions, demonstrating that the proposed strategy enables safe and continuous operation of quad-tilt rotor UAVs even under severe actuator degradation.