Novel Cascaded Incremental Nonlinear Dynamic Inversion Controller Approach for a Tiltrotor VTOL

This paper presents a novel cascaded incremental nonlinear dynamic inversion (INDI) flight controller approach for a tiltrotor VTOL. The main focus is the adaption of INDI to a specific tiltrotor VTOL configuration aiming for optimal exploitation of the actuator capabilities combined with the advantages of a cascaded INDI. For this purpose the tilt angle of the overall thrust vector with respect to the aircraft is introduced as important connection between two cascaded INDIs: For the outer INDI linearizing translational dynamics this serves as virtual control variable. For the inner INDI linearizing rotational dynamics this variable is a pseudo control input. Thus, the tilt mechanisms of the aircraft can be utilized creating rotational and translational dynamics in a cascaded INDI approach linearizing translational and rotational dynamics separately. The approach is evaluated in simulation studies focusing on functionality, linearization and decoupling.