Cyclic Pitch Control of a Rotary Kite

Master Thesis Defense

Daniel Unterweger

Monday, December 20, 2021, 14:00 - 15:00

online via Zoom

Airborne wind energy (AWE) systems need to generate an uplifting force in order to reach altitude. For rotary kite systems this is often done using a dedicated lifting kite where the rotary kite is attached to. The lifting kite is undesired since it has a limited operating region and makes the system hard to maneuver. One approach to eliminating the lifting kite is to use a cyclic pitch mechanism on the rotary kite.
In this thesis it is investigated how this approach can be used to control the altitude of a rotary kite.  A rotation compensation control is implemented and characterized. The aerodynamic effects that the cyclic pitch steering has on the rotor forces are studied. For this purpose, experiments using a rotary kite and a simplified rotor on a test rig are conducted. A simplified aerodynamic rotor model is obtained that describes the tilting moment of the rotor dependent on the rotational speed and controls. A model of the controlled overall AWE system is developed. Finally, the system is simulated to investigate its behavior under different working conditions.
It is shown that a simple PID controller is able to compensate the rotary motion of a rotary kite. The magnitude of the tilting moment on the rotor can be approximated to depend linearly on the cyclic pitch amplitude and quadratically on the rotational speed. From the performed simulation it can be seen, that the overall system is capable of keeping a predefined altitude and compensate wind fluctuations under certain conditions.

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