On control of tethered wings for airborne wind energy

New results in the field of control of tethered wings for airborne wind energy systems with ground-level generators are presented. In the recent literature, a simple model for this kind of systems has been successfully used for control design. Such a model has been justified by measured data collected in experimental tests. Here, a similar model is derived, providing a theoretical analysis that gives an explicit link between the model equations and the physical parameters of the system. Moreover, a novel control approach to obtain figure-eight crosswind trajectories is presented. Contrary to most existing approaches, the proposed technique does not require a measurement of the wind velocity or of the apparent wind at the wing's location. The effectiveness of the approach is shown through hardware-in-the-loop tests and experimental results on a small scale prototype.