Flight Guidance and Control of a Tethered Airplane in an AirborneWind Energy Application

One of the concepts of an upcoming technology known as airborne wind energy is the pumping kite system. The pumping kite system uses a conventional gliders to fly highly dynamic crosswind patterns downwind of a generator to which it is connected by a tether to harvest wind energy. Operating the pumping kite system requires a novel view on conventional flight control. A tether based reference frame is introduced that in effect decouples the longitudinal and lateral motion which can thereby be designed independently and thus allowing the highly dynamic motion of the glider to be controlled through simple control schemes. Furthermore the longitudinal motion is constrained through the tether of which the tangential velocity is controlled by the generator providing an additional control input besides the elevator to control longitudinal motion. Flight tests demonstrate that using the tether based flight control system reasonably simple and commonly used control methods provide satisfactory flight performance.