A Cost-Effective Kite State Estimator for Reliable Automatic Control of Kites

Airborne Wind Energy (AWE) is a developing technology that uses tethered wings to harvest wind energy and convert it into electrical energy. Most of the AWE concepts that will be presented in this thesis have one common challenge: Estimating the position and the orientation of the kite, also called kite state, especially during highly dynamic flight
situations. The focus of this thesis is first, to investigate, if angular sensors are feasible to obtain reliable position data and second, which fusion algorithm can be used to join the data of the angular and Global Navigation Satellite System (GNSS) sensors. The TU Delft prototype is a suitable testing platform for this purpose.

The author added angular sensors to the ground station of the TU Delft AWE system that measure the elevation and the horizontal displacement of the tether holding the kite. They are mounted on a modular stainless steel construction, which has low wear and a long lifetime. The author used the tether length and the angular data to obtain a new position. This position was merged with the two GNSS positions that were already attached to the kite. The angular sensors were able to measure with a resolution of <0.01°. The elevation and azimuth position of the kite had an error of less than 0.7° as long as the tether force was higher than 2000N. One of the GNSS sensors provided reliable data during low force phases. A reliable position in all flight conditions could be obtained by using double exponential smoothing prediction to merge both positions. This development enables the implementation of a reliable kite power control system.