Attitude Control of a Tilt-rotor Tailsitter Micro Air Vehicle Using Incremental Control

Tailsitter Micro Air Vehicles with two rotors are promising due to their simplicity and efficient forward flight, but actuator saturation due to ineffective pitch control at a high angle of attack flight is a challenge limiting the flight envelope. This paper proposes a novel tilt-rotor tailsitter design which features two tilting rotors as the only means for control moment generation. Incremental Nonlinear Dynamic Inversion (INDI) is applied to the attitude control problem of the tiltrotor tailsitter, whose attitude angle tracking performance is validated by indoor and outdoor flight tests. It is found that actuator saturation is largely avoided by using thrust vectoring which provides sufficient capability of pitch moment generation. However, it is also found that the proposed design with only leading-edge tilting motors excluding any aerodynamic control surfaces has limited roll control effectiveness in forward flight.