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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Design Demonstration and Optimization of a Morphing  Aircraft Control Surface Using Flexible Matrix Composite Actuators

Doepke, Edward Brady 13 March 2018 (has links)
The morphing of aircraft wings for flight control started as a necessity for the Wright Brothers but quickly fell out of favor as aircraft increased speed. Currently morphing aircraft control is one of many ideas being explored as we seek to improve aircraft efficiency, reduce noise, and other alternative aircraft solutions. The conventional hinged control surface took over as the predominant method for control due to its simplicity and allowing stiffer wings to be built. With modern technologies in variable stiffness materials, actuators, and design methods, a morphing control surface, which considers deforming a significant portion of the wing's surface continuously, can be considered. While many have considered morphing designs on the scale of small and medium size UAVs, few look at it for full-size commercial transport aircraft. One promising technology in this field is the flexible matrix composite (FMC) actuator. This muscle-like actuator can be embedded with the deformable structure and unlike many other actuators continue to actuate with the morphing of the structure. This was demonstrated in the FMC active spoiler prototype, which was a full-scale benchtop prototype, demonstrated to perform under closed-loop control for both the required deflection and load cases. Based on this FMC active spoiler concept a morphing aileron design was examined. To do this an analysis coupling the structure, fluid, and FMC actuator models was created. This allows for optimization of the design with the objectives of minimizing the hydraulic energy required and mass of the system by varying the layout of the FMC aileron, the material properties used, and the actuator's design and placement with the morphing section. Based on a commercial transport aircraft a design case was developed to investigate the optimal design of a morphing aileron using the developed analysis tool. The optimization looked at minimizing the mass and energy requirements of the morphing aileron and was subject to a series of constraints developed from the design case and the physical limitations of the system. A Pareto front was developed for these two objectives and the resulting designs along the Pareto front explored. From this optimization, a series of design guidelines were developed. / Ph. D.
2

Détection de défauts des systèmes non linéaires à incertitudes bornées continus / Fault detection of nonlinear continuous systems with bounded uncertainties

Thabet, Rihab El Houda 09 December 2014 (has links)
La surveillance des systèmes industriels et/ou embarqués constitue une préoccupation majeure en raison de l’accroissement de leur complexité et des exigences sur le respect des profilsde mission. La détection d’anomalies tient une place centrale dans ce contexte. Fondamentalement,les procédures de détection à base de modèles consistent à comparer le fonctionnement réel dusystème avec un fonctionnement de référence établi à l’aide d’un modèle sans défaut. Cependant,les systèmes à surveiller présentent souvent des dynamiques non linéaires et difficiles à caractériserde manière exacte. L’approche retenue dans cette thèse consiste à englober leur influencepar des incertitudes bornées. La propagation de ces incertitudes permet l’évaluation de seuils dedécision visant à assurer le meilleur compromis possible entre sensibilité aux défauts et robustesseaux perturbations tout en préservant une complexité algorithmique raisonnable. Pour cela, unepart importante du travail porte sur l’extension des classes de modèles dynamiques à incertitudesbornées pour lesquels des observateurs intervalles peuvent être obtenus avec les preuves d’inclusionet de stabilité associées. En s’appuyant sur des changements de coordonnées variant dans letemps, des dynamiques LTI, LPV et LTV sont considérées graduellement pour déboucher sur desclasses de dynamiques Non Linéaires à Incertitudes Bornées continues (NL-IB). Une transformationdes modèles NL-IB en modèles LPV-IB a été utilisée. Une première étude sur les non-linéaritésd’une dynamique de vol longitudinal est présentée. Un axe de travail complémentaire porte surune caractérisation explicite de la variabilité (comportement aléatoire) du bruit de mesure dansun contexte à erreurs bornées. En combinant cette approche à base de données avec celle à basede modèle utilisant un prédicteur intervalle, une méthode prometteuse permettant la détection dedéfauts relatifs à la position d’une surface de contrôle d’un avion est proposée. Une étude portenotamment sur la détection du blocage et de l’embarquement d’une gouverne de profondeur. / The monitoring of industrial and/or embedded systems is a major concern accordingto their increasing complexity and requirements to respect the mission profiles. Detection of anomaliesplays a key role in this context. Fundamentally, model-based detection procedures consist incomparing the true operation of the system with a reference established using a fault-free model.However, the monitored systems often feature nonlinear dynamics which are difficult to be exactlycharacterized. The approach considered in this thesis is to enclose their influence through boundeduncertainties. The propagation of these uncertainties allows the evaluation of thresholds aimingat ensuring a good trade-off between sensitivity to faults and robustness with respect to disturbanceswhile maintaining a reasonable computational complexity. To that purpose, an importantpart of the work adresses the extension of classes of dynamic models with bounded uncertaintiesso that interval observers can be obtained with the related inclusion and stability proofs. Based ona time-varying change of coordinates, LTI, LPV and LTV dynamics are gradually considered tofinally deal with some classes classes of nonlinear continuous dynamics with bounded uncertainties.A transformation of such nonlinear models into LPV models with bounded uncertainties has beenused. A first study on nonlinearities involved in longitudinal flight dynamics is presented. A complementarywork deals with an explicit characterization of measurement noise variability (randombehavior of noise within measurement) in a bounded error context. Combining this data-drivenapproach with a model-driven one using an interval predictor, a promising method for the detectionof faults related to the position of aircraft control surfaces is proposed. In this context, specialattention has been paid to the detection of runaway and jamming of an elevator.

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