A control design approach to achieve fully autonomous take-off and flightmaneuvers with a tethered aircraft is presented and demonstrated in real-worldflight tests with a small-scale prototype. A ground station equipped with acontrolled winch and a linear motion system accelerates the aircraft totake-off speed and controls the tether reeling in order to limit the pullingforce. This setup corresponds to airborne wind energy systems with ground-basedenergy generation and rigid aircrafts. A simple model of the aircraft'sdynamics is introduced and its parameters are identified from experimentaldata. A model-based, hierarchical feedback controller is then designed, whoseaim is to manipulate the elevator, aileron and propeller inputs in order tostabilize the aircraft during the take-off and to achieve figure-of-eightflight patterns parallel to the ground. The controller operates in a fullydecoupled mode with respect to the ground station. Parameter tuning andstability/robustness aspect are discussed, too. The experimental resultsindicate that the controller is able to achieve satisfactory performance androbustness, notwithstanding its simplicity, and confirm that the consideredtake-off approach is technically viable and solves the issue of launching thiskind of airborne wind energy systems in a compact space and at low additionalcost.
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