  This paper proposes a novel algorithm for aerobatic trajectory generation for
a vertical take-off and landing (VTOL) tailsitter flying wing aircraft. The
algorithm differs from existing approaches for fixed-wing trajectory
generation, as it considers a realistic six-degree-of-freedom (6DOF) flight
dynamics model, including aerodynamics equations. Using a global dynamics model
enables the generation of aerobatics trajectories that exploit the entire
flight envelope, enabling agile maneuvering through the stall regime, sideways
uncoordinated flight, inverted flight etc. The method uses the differential
flatness property of the global tailsitter flying wing dynamics, which is
derived in this work. By performing snap minimization in the differentially
flat output space, a computationally efficient algorithm, suitable for online
motion planning, is obtained. The algorithm is demonstrated in extensive flight
experiments encompassing six aerobatics maneuvers, a time-optimal drone racing
trajectory, and an airshow-like aerobatic sequence for three tailsitter
aircraft.
