  This paper presents a flight control design for compound Vertical Takeoff and
Landing (VTOL) vehicles. With their multitude of degrees of controllability as
well as the significant variations in their flight characteristics, VTOL
vehicles present challenges when it comes to designing their flight control
system, especially for the transition phase where the vehicle transitions
between near-hovering and high-speed wing-borne flights. This work extends
previous research on the design of unified and generic control laws that can be
applied to a broad class of vehicles such as hovering vehicles and fixed-wing
aircraft. This paper exploits this unifying property and presents an extension
for the case of compound VTOL vehicles. The proposed control approach consists
of nonlinear geometric control laws that are continuously applicable over the
entire flight envelope, excluding the use of switching policies between
different control algorithms. A transition strategy consisting of a sequence of
high-level setpoints is associated with the flight control laws, it is defined
with respect to flight envelope limitations and is applied in this work to a
commercially available compound unmanned aerial vehicle. The control algorithms
are implemented on a Pixhawk controller, they are evaluated via
Hardware-In-the-Loop simulations and finally validated in a flight experiment.
