Modeling and control of a passively-coupled tilt-rotor VTOL aircraft

We conceptualised, designed and flight-tested a novel type of passively-coupled tilt-rotor vertical take-off and landing drone capable of rapid transitions between vertical and forward flight. The drone consists of a quadrotor frame attached to a fixed-wing frame by an unactuated hinged mechanism. The platform is capable of smooth transitions from hover to forward flight without the use of tilting actuators: transitions are made possible by differential thrust between the fore and aft propellers of the quadrotor frame. This simplifies greatly the mechanical design and control problem. A cascaded control architecture based on P/PID controllers is proposed to achieve inner-loop attitude, height and forward velocity control. Simulated and experimental results are obtained with close match for hover, transitions, forward flight, and banked turn maneuvers. This concept VTOL aircraft is particularly desirable in urban air mobility applications requiring operation in restricted airspace and rapid transition for improved endurance.