  The control design of an airborne wind energy system with rigid aircraft,
vertical take-off and landing, and pumping operation is described. A
hierarchical control structure is implemented, in order to address all
operational phases: take-off, transition to power generation, pumping energy
generation cycles, transition to hovering, and landing. Control design at all
hierarchical levels is described. The design approach is conceived and
developed with real-world applicability as main driver. Aircraft design
considerations in light of system maneuverability are presented, too, as well
as three possible alternative strategies for the retraction phase of the
pumping cycle. The automatic control approach is assessed in simulation with a
realistic model of the overall system, and the results yield a comparison among
the three retraction strategies, clearly indicating the most efficient one. The
presented results allow one to simulate the dynamical behavior of an AWE system
in all operational phases, enabling further studies on all-round system
automation, towards fully autonomous and reliable operation.
