On sensor fusion for airborne wind energy systems

TL;DR

This paper investigates sensor fusion techniques for accurately estimating the position, velocity, and heading of airborne wind energy systems, enabling improved control despite complex nonlinear dynamics and fast maneuvers.

Contribution

It introduces a structured approach to partitioning the nonlinear system into simpler filtering problems and evaluates sensor fusion algorithms through experimental tests on small-scale prototypes.

Findings

Filtering algorithms are effective across different wing sizes and designs.

Sensor fusion based on kinematic laws is independent of wing-specific features.

Experimental results demonstrate reliable state estimation in dynamic conditions.

Abstract

A study on filtering aspects of airborne wind energy generators is presented. This class of renewable energy systems aims to convert the aerodynamic forces generated by tethered wings, flying in closed paths transverse to the wind flow, into electricity. The accurate reconstruction of the wing's position, velocity and heading is of fundamental importance for the automatic control of these kinds of systems. The difficulty of the estimation problem arises from the nonlinear dynamics, wide speed range, large accelerations and fast changes of direction that the wing experiences during operation. It is shown that the overall nonlinear system has a specific structure allowing its partitioning into sub-systems, hence leading to a series of simpler filtering problems. Different sensor setups are then considered, and the related sensor fusion algorithms are presented. The results of experimental tests carried out with a small-scale prototype and wings of different sizes are discussed. The designed filtering algorithms rely purely on kinematic laws, hence they are independent from features like wing area, aerodynamic efficiency, mass, etc. Therefore, the presented results are representative also of systems with larger size and different wing design, different number of tethers and/or rigid wings.