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Image Processing Systems and Algorithms for estimating Deformations of Aircraft Structures in Flight

Demoulin, Quentin. Image Processing Systems and Algorithms for estimating Deformations of Aircraft Structures in Flight. PhD, Informatique et Télécommunication, Institut National Polytechnique de Toulouse, 2021

(Document in English)

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If you have ever been on an aircraft and looked at the window, you may have noticed the remarkable deformations of its wings. This observation actually conveys a lot of information about the aerodynamic efforts that are applied to the aircraft. Long before the first flight of an aircraft, manufacturers are able to predict its mechanical behavior in various scenarii depending for instance on the aircraft weight, speed or angle of attack, based on accurate theoretical models. As part of the aircraft certification procedure, these models have to be validated and refined through in-flight estimation of wing deformations. However, as the quality and accuracy of the wing models increase, the methods used to obtain the actual measurements should also evolve. In this work, a new system is developed and evaluated to estimate the 3D shape of a wing in flight. To answer the new needs of dense mapping, precision, or frequency, while introducing no disturbance on the wing aerodynamic behavior, this study is focusing on the methods of non-contact 3D reconstruction. After performing a detailed study about state-ofthe-art systems in this field, a photogrammetry approach using multiple cameras installed at the aircraft windows was retained, and a full algorithmic and hardware system was developed. Similarly to most standard photogrammetry methods, the proposed approach is based on Bundle Adjustment (BA), a classical method that simultaneously estimates camera positions and surrounding 3D scene. BA is an iterative optimization algorithm that aims at minimizing a non-convex and non-linear cost function. Therefore, one cannot guarantee its convergence to a global minimum, and the choice of the initial conditions is crucial in practical applications. Consequently, the application of photogrammetry to 3D wing reconstruction in flight is a very challenging problem, due to strong installation constraints, and highly varying environment with vibrations, luminosity changes, potential reflections and shadows. To face these challenges, this work presents a new constrained BA, which uses prior knowledge resulting from wing mechanical limits beyond which the wing would break, and improves reconstruction results as demonstrated through realistic tests. In a second step, an in-depth study of error sources and reconstruction uncertainty is provided in order to guarantee the quality of the 3D estimation, as well as the possibility of having a better interpretation of reconstruction errors. To this aim, all potential sources of uncertainty are evaluated, and propagated through the proposed framework using three approaches: analytical calculation, Monte-Carlo simulation, and experimental validation on synthetic images. The different implementations and results allowed one to conclude on the advantages and disadvantages of each method. They also prove that the developed system meets the expectations of Airbus. Finally, the designed system is validated on real tests with an A350-1000 of the flight test center in Airbus. These experimentations conducted in real conditions show the pertinence of the proposed solution with respect to the observed sources of uncertainty, and provide promising results.

Item Type:PhD Thesis
Uncontrolled Keywords:
Institution:Université de Toulouse > Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)
Laboratory name:
Research Director:
Tourneret, Jean-Yves and Kouamé, Denis
Deposited On:05 Nov 2021 12:33

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