Flexible Tethered Kite with Movable Attachment Points, Part II: State and Wind Estimation

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 to 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 second in a series of two that studies the dynamics and control of a flexible kite. In this part, the dynamic model and trajectories derived in Part I are used to develop a nonlinear dynamic observer. Full state estimation is required to implement one of the proposed feedback tracking controllers. The system dynamics are extremely complex and therefore a method that does not require the computation of vector field derivatives has been chosen. The square-root unscented Kalman filter is implemented to estimate the kite dynamics as well as the true wind speed at the kite.