Flexible Tethered Kite with Movable Attachment Points, Part I: Dynamics and Control

Tethered kite technology is one potential means of harnessing energy available in high altitude winds. In an efficient and practical system, the kite is required to fly in cyclic patterns that maximize net power produced per cycle. At the same time, the tether length must be controlled to ensure the system does not expend more energy than it produces. This can be a challenging problem when the intermittency of the wind speed and direction, as well as unsteady wind components, are taken into account. This paper is the first of two that studies the dynamics and control of a flexible kite. In this part, a highly simplified dynamic model of the kite is derived based on a hinged, two-plate representation. This first approximation considers aerodynamic forces produced by the plates as a function of their instantaneous angle of attack. The plates are constrained to have the same yawing angle, but are unconstrained in pitch and roll. The combined pitch and roll of the system is controlled by means of moveable attachment points for the tether(s). Both stationkeeping and timevarying trajectories are considered, for which feedback control is applied for tracking.