RT Dissertation/Thesis
T1 Application of aircraft's flight testing techniques to the aerodynamic characterization of power kites
A1 Borobia Moreno, Ricardo
AB This thesis has developed an experimental methodology for the flight testing and data analysis ofpower kites applied to Airborne Wind Energy Systems (AWES). In particular, the EstimationBefore Modeling technique, a well-known method in the aerospace industry for the aerodynamiccharacterization of an aircraft using real flight data, has been adapted for tethered aircraft. Thedeveloped methodology has two main building blocks: (i) an experimental setup to recordexperimental data during the flight testing, and (ii) a Flight Path Reconstruction algorithm toestimate the state of the system from the experimental data. From them, the aerodynamiccharacteristics of two types of kites were investigated.The proposed experimental setup was designed to be low cost, portable and easily adaptable toboth, rigid and semi-rigid kites. It is composed of an instrumented kite representative of the onesused in AWES, an instrumented control bar, a ground computer and a wind station. Whenever itwas possible, commercial off the shelf components have been used, including low cost openhardwaresensors based on the PixHawk platform. However, after the first flight tests wereconducted and the obtained results were discussed, high precision sensors were also included.The Flight Path Reconstruction (FPR) algorithm for tethered aircraft is based on an Extended KalmanFilter (EKF). In addition to the standard set of estimated state variables (ie. Euler angles, positionor ground speed), the algorithm also provides the aerodynamic torque and forces upon the kite aswell as the tether tensions and wind velocity vector. The EBM technique, and the FPR algorithmhave been used to identify the aerodynamic characteristics of both, four-line Leading EdgeInflatable (LEI) kites and two-line Rigid Frame Delta (RFD) kites. Quantitative and qualitativeresults have been obtained. Albeit both types of kites exhibited very high AoA during the flight,some significant differences were found. In particular, the estimated lift coefficient of the LEIkite showed a behavior identified with a post-stall condition, while the RFD showed a pre-stallbehavior with a lower AoA and a positive relation between the lift coefficient and the kite AoA.The presented experimental methodology can be of great interest for AWE industry as it helps toimprove modeling of tethered aircraft, leading to more accurate performance figures which mayincrease investors interest in the technology. Moreover, flight testing methodologies andexperimental data analysis are of great interest for benchmarking AWES performances,contributing to de-risk their development process and providing better tools for AWE "bestconcept" identification. Finally, as a sub-product of the presented methodology, the FPRalgorithm can be used as a validated state estimator of the tethered aircraft, which is a keyelement of a closed loop flight control system.
YR 2021
FD 2021-01
LK https://hdl.handle.net/10016/32528
UL https://hdl.handle.net/10016/32528
LA eng
DS e-Archivo
RD 1 sept. 2024