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For the stability assessment of members and structures according to EN 1993-1-1, the equivalent member method, the geometrical non-linear calculation with equivalent geometrical imperfections or the GMNIA analysis with geometrical imperfections and residual stresses can be used alternatively. The second possibility requires a corresponding model for the cross-section resistance. For the verification of lateral torsional buckling, bow imperfections e0 out-of-plane are defined, which lead in combination with the given loading in-plane and the geometrical non-linear analysis to bending moments Mz and torsion of the members. The amplitudes of the imperfections are highly dependent on the nature of the approach (e.g., scaling of the buckling shape, assumption of bow imperfections) and the verification method for the members. Within the framework of the scientific work supervised by the TU Dresden and TU Darmstadt, extensive parametric studies were conducted to calibrate imperfections for lateral torsional buckling based on the GMNIA. After determining the nature of imperfections and the design models for section resistance, this article presents results of these parametric studies and shows the calibration of imperfections for a standardisation proposal based on EN1993-1-1. The evaluation of the data in combination with the necessary simplifications for the design practice leads to appropriate definitions of imperfection values e0,LT and the necessary differentiations.

Tesis por compendio / [ES] El fuego es uno de los principales riesgos que pueden afectar a las estructuras de acero. El impacto del fuego en estas estructuras es muy adverso y complejo de simular, principalmente en escenarios de fuego realistas, donde el calentamiento en los miembros de acero no es uniforme y en miembros de acero esbeltos porque fallan prematuramente por la aparición de abolladuras locales. Para predecir con exactitud la respuesta de las estructuras de acero al fuego, se han desarrollado modelos avanzados y complejos de EF con elementos de cáscara y sólidos. Sin embargo, estos modelos son costosos desde el punto de vista computacional, lo que complica la realización de análisis más complejos que requieren muchas simulaciones en poco tiempo y con bajos costes computacionales. Por lo tanto, es necesario desarrollar modelos computacionales sencillos, precisos y de bajo coste, tan fiables como los modelos de cáscara, que abran el camino más fácilmente hacia la modelización de problemas estructurales de acero más complejos en situación de incendio. En esta tesis se presentan propuestas sencillas y de bajo coste computacional para simular la respuesta mecánica de estructuras de acero en condición de incendio utilizando un elemento finito de viga de Timoshenko de Ansys. Una de las propuestas consiste en una nueva metodología para el análisis en 3D de estructuras de acero sometidas a temperaturas no uniformes por el fuego. Las otras consisten en dos estrategias de modelización para analizar el pandeo lateral torsional en miembros de acero de clase 4 a temperaturas elevadas. Las propuestas simplifican significativamente la modelización estructural y se validan satisfactoriamente con resultados numéricos y experimentales. Esto significa que problemas complejos de ingeniería de incendio, como los análisis probabilísticos y de optimización, pueden tratarse con mucha más facilidad, lo que representa un paso importante hacia la aplicación generalizada de enfoques basados en el desempeño para tratar los efectos del fuego en las estructuras de acero. / [CA] El foc és un dels principals riscos que poden afectar les estructures d'acer. L'impacte del foc en estes estructures és molt advers i complex de simular, principalment en escenaris de foc realistes, on el calfament en els membres d'acer no és uniforme i en membres d'acer esvelts perquè fallen prematurament per l'aparició d'abonyegadures locals. Per a predir amb exactitud la resposta de les estructures d'acer al foc, s'han desenvolupat models avançats i complexos d'elements finits de corfa i sòlids. No obstant això, estos models són computacionalment costosos, la qual cosa complica la realització d'anàlisi més complexos que requerixen moltes simulacions en poc de temps i amb baixos costos computacionals. Per tant, és necessari desenvolupar models computacionals senzills, precisos i de baix cost, tan fiables com els models de corfa, que òbriguen el camí més fàcilment cap a la modelització de problemes estructurals d'acer més complexos en situació d'incendi. En esta tesi es presenten propostes senzilles i de baix cost per a simular la resposta mecànica d'estructures d'acer en condició d'incendi utilitzant un element finit de biga de Timoshenko d'Ansys. Una de les propostes consistix en una nova metodologia per a l'anàlisi en 3D d'estructures d'acer sotmeses a temperatures no uniformes pel foc. Les altres consistixen en dos estratègies de modelització per a analitzar el bombament lateral torsional en membres d'acer de classe 4 a temperatures elevades. Les propostes simplifiquen significativament la modelització estructural i es validen satisfactòriament amb resultats numèrics i experimentals. Açò significa que problemes complexos d'enginyeria d'incendi, com les anàlisis probabilístiques i d'optimització, poden tractar-se amb molta més facilitat, la qual cosa representa un pas important cap a l'aplicació generalitzada d'enfocaments basats en l'exercici per a tractar els efectes del foc en les estructures d'acer. / [EN] Fire is one of the main hazards that can affect steel structures. The impact of fire on these structures is highly adverse and complex to simulate, mainly in realistic fire scenarios, where heating in steel members is non-uniform and in slender steel members because they fail prematurely by local buckling. In order to accurately predict the response of steel structures to fire, advanced and complex FE models with shell and solid elements have been developed. However, these shell models are computationally expensive, complicating the carrying out of more complex analyses that require many simulations in a short time and at low computational costs. Therefore, there is a need to develop simple, accurate, and low-cost computational models as reliable as shell-type models that open the path more easily towards modeling more complex steel structural problems in fire conditions. This thesis presents simple and low-cost proposals to simulate the mechanical response of steel structures under fire using Timoshenko's beam-type finite element available in Ansys. One of the proposals consists of a new methodology for the 3D-analysis of steel frames subjected to non-uniform temperatures by fire. The others consist of two modeling strategies for analyzing the lateral-torsional buckling in class-4 steel structural members at elevated temperatures. The proposals significantly simplify the structural modeling and satisfactorily validate numerical and experimental results. That means that complex fire engineering problems, such as probabilistic and optimization analyses, can be handled much more easily, representing a significant step toward the generalized application of performance-based approaches to deal with fire effects on steel structures. / Pallares Muñoz, MR. (2022). New Proposals for Modeling the Thermo-Mechanical Response of Steel Structures Under Fire Using Beam-Type Finite Elements [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/182768 / Compendio

Thin-walled cold-formed steel (CFS) has exhibited inherent structural and architectural advantages over other constructional materials, for example, high strength-to-weight ratio, ease of fabrication, economy in transportation and the flexibility of sectional profiles, which make CFS ideal for modern residential and industrial buildings. They have been increasingly used as purlins as the intermediate members in a roof system, or load-bearing components in low- and mid-rise buildings. However, using CFS members in building structures has been facing challenges due to the lack of knowledge to the fire performance of CFS at elevated temperatures and the lack of fire design guidelines. Among all available design specifications of CFS, EN1993-1-2 is the only one which provided design guidelines for CFS at elevated temperatures, which, however, is based on the same theory and material properties of hot-rolled steel. Since the material properties of CFS are found to be considerably different from those of hot-rolled steel, the applicability of hot-rolled steel design guidelines into CFS needs to be verified. Besides, the effect of non-uniform temperature distribution on the failure of CFS members is not properly addressed in literature and has not been specified in the existing design guidelines. Therefore, a better understanding of fire performance of CFS members is of great significance to further explore the potential application of CFS. Since CFS members are always with thin thickness (normally from 0.9 to 8 mm), open cross-section, and great flexural rigidity about one axis at the expense of low flexural rigidity about a perpendicular axis, the members are usually susceptible to various buckling modes which often govern the ultimate failure of CFS members. When CFS members are exposed to a fire, not only the reduced mechanical properties will influence the buckling capacity of CFS members, but also the thermal strains which can lead additional stresses in loaded members. The buckling behaviour of the member can be analysed based on uniformly reduced material properties when the member is unprotected or uniformly protected surrounded by a fire that the temperature distribution within the member is uniform. However if the temperature distribution in a member is not uniform, which usually happens in walls and/or roof panels when CFS members are protected by plaster boards and exposed to fire on one side, the analysis of the member becomes very complicated since the mechanical properties such as Young’s modulus and yield strength and thermal strains vary within the member. This project has the aim of providing better understanding of the buckling performance of CFS channel members under non-uniform temperatures. The primary objective is to investigate the fire performance of plasterboard protected CFS members exposed to fire on one side, in the aspects of pre-buckling stress distribution, elastic buckling behaviour and nonlinear failure models. Heat transfer analyses of one-side protected CFS members have been conducted firstly to investigate the temperature distributions within the cross-section, which have been applied to the analytical study for the prediction of flexural buckling loads of CFS columns at elevated temperatures. A simplified numerical method based on the second order elastic – plastic analysis has also been proposed for the calculation of the flexural buckling load of CFS columns under non-uniform temperature distributions. The effects of temperature distributions and stress-strain relationships on the flexure buckling of CFS columns are discussed. Afterwards a modified finite strip method combined with the classical Fourier series solutions have been presented to investigate the elastic buckling behaviour of CFS members at elevated temperatures, in which the effects of temperatures on both strain and mechanical properties have been considered. The variations of the elastic buckling loads/moments, buckling modes and slenderness of CFS columns/beams with increasing temperatures have been examined. The finite element method is also used to carry out the failure analysis of one-side protected beams at elevated temperatures. The effects of geometric imperfection, stress-strain relationships and temperature distributions on the ultimate moment capacities of CFS beams under uniform and non-uniform temperature distributions are examined. At the end the direct strength method based design methods have been discussed and corresponding recommendations for the designing of CFS beams at elevated temperatures are presented. This thesis has contributed to improve the knowledge of the buckling and failure behaviour of CFS members at elevated temperatures, and the essential data provided in the numerical studies has laid the foundation for further design-oriented studies.

Le cancer du sein est le cancer le plus fréquent chez la femme. Il demeure la cause de mortalité la plus importante chez les femmes âgées entre 35 et 55 ans. Au Canada, plus de 20 000 nouveaux cas sont diagnostiqués chaque année. Les études scientifiques démontrent que l'espérance de vie est étroitement liée à la précocité du diagnostic. Les moyens de diagnostic actuels comme la mammographie, l'échographie et la biopsie comportent certaines limitations. Par exemple, la mammographie permet de diagnostiquer la présence d’une masse suspecte dans le sein, mais ne peut en déterminer la nature (bénigne ou maligne). Les techniques d’imagerie complémentaires comme l'échographie ou l'imagerie par résonance magnétique (IRM) sont alors utilisées en complément, mais elles sont limitées quant à la sensibilité et la spécificité de leur diagnostic, principalement chez les jeunes femmes (< 50 ans) ou celles ayant un parenchyme dense. Par conséquent, nombreuses sont celles qui doivent subir une biopsie alors que leur lésions sont bénignes. Quelques voies de recherche sont privilégiées depuis peu pour réduire l`incertitude du diagnostic par imagerie ultrasonore. Dans ce contexte, l’élastographie dynamique est prometteuse. Cette technique est inspirée du geste médical de palpation et est basée sur la détermination de la rigidité des tissus, sachant que les lésions en général sont plus rigides que le tissu sain environnant. Le principe de cette technique est de générer des ondes de cisaillement et d'en étudier la propagation de ces ondes afin de remonter aux propriétés mécaniques du milieu via un problème inverse préétabli. Cette thèse vise le développement d'une nouvelle méthode d'élastographie dynamique pour le dépistage précoce des lésions mammaires. L'un des principaux problèmes des techniques d'élastographie dynamiques en utilisant la force de radiation est la forte atténuation des ondes de cisaillement. Après quelques longueurs d'onde de propagation, les amplitudes de déplacement diminuent considérablement et leur suivi devient difficile voir impossible. Ce problème affecte grandement la caractérisation des tissus biologiques. En outre, ces techniques ne donnent que l'information sur l'élasticité tandis que des études récentes montrent que certaines lésions bénignes ont les mêmes élasticités que des lésions malignes ce qui affecte la spécificité de ces techniques et motive la quantification de d'autres paramètres mécaniques (e.g.la viscosité). Le premier objectif de cette thèse consiste à optimiser la pression de radiation acoustique afin de rehausser l'amplitude des déplacements générés. Pour ce faire, un modèle analytique de prédiction de la fréquence de génération de la force de radiation a été développé. Une fois validé in vitro, ce modèle a servi pour la prédiction des fréquences optimales pour la génération de la force de radiation dans d'autres expérimentations in vitro et ex vivo sur des échantillons de tissu mammaire obtenus après mastectomie totale. Dans la continuité de ces travaux, un prototype de sonde ultrasonore conçu pour la génération d'un type spécifique d'ondes de cisaillement appelé ''onde de torsion'' a été développé. Le but est d'utiliser la force de radiation optimisée afin de générer des ondes de cisaillement adaptatives, et de monter leur utilité dans l'amélioration de l'amplitude des déplacements. Contrairement aux techniques élastographiques classiques, ce prototype permet la génération des ondes de cisaillement selon des parcours adaptatifs (e.g. circulaire, elliptique,…etc.) dépendamment de la forme de la lésion. L’optimisation des dépôts énergétiques induit une meilleure réponse mécanique du tissu et améliore le rapport signal sur bruit pour une meilleure quantification des paramètres viscoélastiques. Il est aussi question de consolider davantage les travaux de recherches antérieurs par un appui expérimental, et de prouver que ce type particulier d'onde de torsion peut mettre en résonance des structures. Ce phénomène de résonance des structures permet de rehausser davantage le contraste de déplacement entre les masses suspectes et le milieu environnant pour une meilleure détection. Enfin, dans le cadre de la quantification des paramètres viscoélastiques des tissus, la dernière étape consiste à développer un modèle inverse basé sur la propagation des ondes de cisaillement adaptatives pour l'estimation des paramètres viscoélastiques. L'estimation des paramètres viscoélastiques se fait via la résolution d'un problème inverse intégré dans un modèle numérique éléments finis. La robustesse de ce modèle a été étudiée afin de déterminer ces limites d'utilisation. Les résultats obtenus par ce modèle sont comparés à d'autres résultats (mêmes échantillons) obtenus par des méthodes de référence (e.g. Rheospectris) afin d'estimer la précision de la méthode développée. La quantification des paramètres mécaniques des lésions permet d'améliorer la sensibilité et la spécificité du diagnostic. La caractérisation tissulaire permet aussi une meilleure identification du type de lésion (malin ou bénin) ainsi que son évolution. Cette technique aide grandement les cliniciens dans le choix et la planification d'une prise en charge adaptée. / Breast cancer is the most frequent cancer in women and the leading cause of death for women between 35 and 55 years old. In Canada, more than 20,000 new cases are diagnosed each year. Most of the previous works have shown that life expectancy is closely related to the precocity of diagnosis. Current diagnostic imaging methods such as mammography, sonography, MRI present limitations such as irradiation (mammography), low specificity and low resolution (sonography) and high cost (MRI). For example, about 95% of abnormalities detected by mammography are proven to be benign lesions after complementary examinations (biopsy). Sonography is useful as a complementary examination but the low resolution of its images, its low specificity (54% for women less than 50 years) and its operator dependent interpretation seriously limit the use of this modality alone. MRI is a non-invasive technique with a relatively high sensitivity (86% for women below 50 years), but its limitations are the high cost and the waiting time for medical examination, which dedicate it as a monitoring technique in high-risk patients. It is therefore necessary to examine new noninvasive and cost effective methods. In this context, dynamic elastography is a promising approach. It is an emerging quantitative medical imaging technique inspired from palpation and based on the determination of elastic properties (stiffness) of tissues. This thesis aims the development of a novel dynamic ultrasound elastography method for early detection of breast lesions. One of the main problems of dynamic elastography techniques using remote palpation (acoustic radiation force) is the strong attenuation of shear waves. After few wavelengths of propagation, displacement amplitudes considerably decrease and their tracking becomes difficult even impossible. This problem greatly affects biological tissue characterization. Moreover, these techniques give only the information about elasticity while recent studies show that some benign lesions have the same elasticity as malignant lesions which affect the specificity of these techniques and motivate investigation of other physical parameters (e.g. viscosity). The first objective of this thesis is to optimize the acoustic radiation force using frequency adaptation to enhance the amplitude of displacements. An analytical model has been developed to predict the optimal frequency for the generation of the radiation force. Once validated on phantoms (in vitro), this model was used for the prediction of the optimal frequencies for the generation of the radiation force in tissue mimicking phantoms and ex vivo human breast cancer samples obtained after total mastectomy. Gains in magnitude were between 20% to158% for in vitro measurements on agar-gelatin phantoms, and 170% to 336% for ex vivo measurements on a human breast sample, depending on focus depths and attenuations of tested samples. The signal-to-noise ratio was also improved by more than four folds with adapted sequences. We conclude that frequency adaptation is a complementary technique that is efficient for the optimization of displacement amplitudes. This technique can be used safely to optimize the deposited local acoustic energy, without increasing the risk of damaging tissues and transducer elements. In the second part of this thesis, a prototype of an ultrasound probe for the generation of a specific type of adaptive shear waves called ''adaptive torsional shear waves'' has been developed. The goal was to use the optimized radiation force (developed in the first part) to generate adaptive torsional shear wave, and prove their utility in improving the amplitude of displacement. During their inward propagation, the amplitude of displacement generated by torsional shear waves was enhanced and the signal to noise ratio improved due to the constructive interferences. Torsional shear waves can also resonate heterogeneities which further enhance the displacement contrast between suspicious masses and its surrounding medium. Finally, in the context of assessment of mechanical proprieties of tissue, the last step of this thesis is to develop an inverse problem based on the propagation of adaptive torsional shear waves to estimate the viscoelastic parameters. A finite element method (FEM) model was developed to solve the inverse wave propagation problem and obtain viscoelastic properties of interrogated media. The inverse problem was formulated and solved in the frequency domain and its robustness was evaluated. The proposed model was validated in vitro with two independent rheology methods on several homogeneous and heterogeneous breast tissue mimicking phantoms over a broad range of frequencies (up to 400Hz). The obtained results were in good agreement with reference rheology methods with discrepancies between 8% and 38% for shear modulus and from 9% to 67% for loss modulus. The robustness study showed that the proposed inverse problem solution yielded a good estimation of the storage (19%) and loss moduli (32%) even with very noisy signals.

After decades of routine operation, the hydropower industry faces new challenges. Large-scale integration of other renewable sources of generation in the power system accentuates the role of hydropower as a regulating resource. At the same time, an extensive reinvestment programme has commenced where many old components and apparatus are being refurbished or replaced. Introduction of new technical solutions in existing power plants requires good systems knowledge and careful consideration. Important tools for research, development and analysis are suitable mathematical models, numerical simulation methods and laboratory equipment. This doctoral thesis is devoted to studies of the electromechanical interaction between hydropower units and the power system. The work encompasses development of mathematical models, empirical methods for system identification, as well as numerical and experimental studies of hydropower generator and power system interaction. Two generator modelling approaches are explored: one based on electromagnetic field theory and the finite element method, and one based on equivalent electric circuits. The finite element model is adapted for single-machine infinite-bus simulations by the addition of a network equivalent, a mechanical equation and a voltage regulator. Transient simulations using both finite element and equivalent circuit models indicate that the finite element model typically overestimates the synchronising and damping properties of the machine. Identification of model parameters is performed both numerically and experimentally. A complete set of equivalent circuit parameters is identified through finite element simulation of standard empirical test methods. Another machine model is identified experimentally through frequency response analysis. An extension to the well-known standstill frequency response (SSFR) test is explored, which involves measurement and analysis of damper winding quantities. The test is found to produce models that are suitable for transient power system analysis. Both experimental and numerical studies show that low resistance of the damper winding interpole connections are vital to achieve high attenuation of rotor angle oscillations. Hydropower generator and power system interaction is also studied experimentally during a full-scale startup test of the Nordic power system, where multiple synchronised data acquisition devices are used for measurement of both electrical and mechanical quantities. Observation of a subsynchronous power oscillation leads to an investigation of the torsional stability of hydropower units. In accordance with previous studies, hydropower units are found to be mechanically resilient to subsynchronous power oscillations. However, like any other generating unit, they are dependent on sufficient electrical and mechanical damping. Two experimentally obtained hydraulic damping coefficients for a large Francis turbine runner are presented in the thesis.

This thesis presents the development of a fault detection and diagnosis (FDD) procedure capable of capturing, isolating and identifying multiple abrupt parametric faults. The proposed method relies on parameter estimation deployed in a set membership framework. This approach presupposes the utilization of a linearly parametrizable model and the a priori knowledge of bounded noise errors and parameter perturbations. Under these assumptions, a data-hyperspace is generated at every time instant. The goal of set membership identification (SMI) is the determination of the parametric set, formed as an orthotope or ellipsoid, within which the nominal parameter vector resides and intersects with the data-hyperspace. The fault detection mechanism is activated when the normal operation of the SMI procedure is interrupted due to an empty intersection of the data-hyperspace and the estimated parametric set. At the detection instant, a resetting procedure is performed in order to compute the parameter set and the data-hyperspace that contain the varied nominal parameter vector, allowing the SMI algorithm to continue its operation. During the fault isolation, consistency tests are executed, relying on the projections of the worst case parametric sets and the ones arisen from the normal operation of SMI. A faulty component is indicated when these projections do not intersect, while the distance of their centers is used for fault identification. In case of the ellipsoidal SMI-based FDD and under the assumption of a time invariant parameter vector, a new fault detection criterion is defined based on the intersection of support orthotopes of ellipsoids. A more accurate estimation of the time instant of fault occurrence is proposed based on the application of a backward-in-time procedure starting from the fault detection instant, while the conditions under which a fault will never be detected by the orthotopic and ellipsoidal SMI based FDD are provided. This dissertation explores the efficiency of the proposed FDD methodology for capturing failure modes of two microelectromechanical systems; an electrostatic parallel-plate microactuator and a torsionally resonant atomic force microscope. From an engineering point of view, failure modes appeared in the microcomponents of the microactuator and the TR-AFM are encountered as parameter variations and are captured, isolated and identified by the proposed FDD methodology. / Σε αυτή την διατριβή, παρουσιάζεται η ανάπτυξη μιας διαδικασίας Ανίχνευσης και Διάγνωσης Σφαλμάτων, η οποία είναι ικανή να εντοπίζει, απομονώνει και αναγνωρίζει πολλαπλά, απότομα παραμετρικά σφάλματα. H προτεινόμενη μέθοδος βασίζεται στην αναγνώριση του συνόλου συμμετοχής των παραμέτρων. Ο στόχος της Αναγνώρισης Συνόλου Συμμετοχής είναι ο καθορισμός του παραμετρικού συνόλου εντός του οποίου κείται το ονομαστικό διάνυσμα παραμέτρων, δεδομένου ότι το ονομαστικό διάνυσμα παραμέτρων ανήκει επίσης σε έναν υπερχώρο δεδομένων. Το παραμετρικό σύνολο απεικονίζεται ως ένα ορθότοπο ή ένα ελλειψοειδές, λόγω της εύκολης μαθηματικής τους περιγραφής. Έτσι, η διαδικασία Αναγνώρισης Συνόλου Συμμετοχής αντιστοιχεί σε ένα πρόβλημα βελτιστοποίησης, το οποίο αποσκοπεί στον υπολογισμό του ορθοτόπου ή ελλειψοειδούς το οποίο περιέχει το ονομαστικό διάνυσμα παραμέτρων και τέμνεται με τον υπερχώρο δεδομένων. Ο μηχανισμός Ανίχνευσης Σφαλμάτων ενεργοποιείται όταν διακόπτεται η φυσιολογική λειτουργία της Αναγνώρισης Συνόλου Συμμετοχής, λόγω της κενής τομής μεταξύ των εκτιμώμενου παραμετρικού συνόλου και του υπερχώρου δεδομένων. Τη χρονική στιγμή ανίχνευσης ενός σφάλματος, εφαρμόζεται μια διαδικασία επαναρύθμισης που σκοπεύει στον υπολογισμό του νέου παραμετρικού συνόλου, το οποίο περιέχει το μεταβεβλημένο ονομαστικό διάνυσμα παραμέτρων και τέμνεται με το υπερχώρο δεδομένων. Κατά τη διάρκεια της διαδικασίας απομόνωσης του σφάλματος, εκτελούνται τεστ συμβατότητας, τα οποία βασίζονται στις προβολές των νέων παραμετρικών συνόλων και στις προβολές των παραμετρικών συνόλων χείριστης περίπτωσης, ενώ η απόσταση των κέντρων των προβολών χρησιμοποιείται για αναγνώριση σφάλματος. Στην περίπτωση που η Ανίχνευση και Διάγνωση Σφαλμάτων πραγματοποιείται βασιζόμενη στην Αναγνώριση Συνόλου Συμμετοχής με ελλειψοειδή και θεωρώντας το ονομαστικό διάνυσμα παραμέτρων χρονικά αμετάβλητο, ορίζεται ένα νέο κριτήριο ανίχνευσης σφαλμάτων, χρησιμοποιώντας την τομή των περιβαλλόντων ορθοτόπων των ελλειψοειδών. Σε αυτή την περίπτωση, ένα σφάλμα ανιχνεύεται όταν η τομή αυτή είναι κενή. Ακόμη, προτείνεται μια πιο ακριβής εκτίμηση της χρονικής στιγμής εμφάνισης του σφάλματος, ενώ παρατίθενται οι συνθήκες υπό τις οποίες ένα σφάλμα μπορεί να μην ανιχνευθεί ποτέ με την εφαρμογή των προτεινόμενων μεθόδων. Η συγκεκριμένη διατριβή επίσης ερευνά την αποτελεσματικότητα της προτεινόμενης μεθοδολογίας Ανίχνευσης και Διάγνωσης Σφαλμάτων για τον εντοπισμό των τρόπων εκδήλωσης σφαλμάτων σε δύο μικροηλεκτρομηχανικά συστήματα (ΜΗΜΣ), έναν ηλεκτροστατικό μικροεπενεργητή παράλληλων πλακών και ένα ατομικό μικροσκόπιο συντονισμού στρέψης. Από πλευράς μηχανικής, οι τρόποι εκδήλωσης σφαλμάτων στα δομικά στοιχεία του μικροεπενεργητή ή του ατομικού μικροσκοποίου αντιμετωπίζονται ως απότομες παραμετρικές, οι οποίες εντοπίζονται και διαγιγνώσκονται από τις προτεινόμενες μεθόδους.

Tesis por compendio / [ES] El desarrollo tecnológico en la creación de trayectorias que permitan navegación libre de colisiones de Vehículos Autónomos (AVs) ha sido un objetivo constante de estudio debido a su fuerte interés científico y tecnológico en las últimas tres décadas. Las diferentes clases de AVs, ya sean Vehículos Aéreos no Tripulados (UAVs), Vehículos Terrestres no Tripulados (UGVs) o Vehículos Submarinos no Tripulados (UUVs), fomentan el desarrollo e implementación de trayectorias en el espacio tridimensional (3D). Un grupo especial de tecnología UAV está caracterizado por su ala fija, lo cual destaca características particulares en los AVs, debido a las restricciones no-holonómicas (un sistema que se describe mediante un conjunto de parámetros sujetos a restricciones diferenciales que no permiten que un vehículo se mueva de forma instantánea en cualquier dirección). En este sentido, las trayectorias navegables para estos UAVs no deben ser construidas como un conjunto de líneas rectas y círculos como en la gran mayoría de planificadores basados en primitivas, ya que no se garantiza una continuidad en su curvatura. Por lo tanto, las trayectorias construidas para esta rama tecnológica deben ser resueltas considerando las diferentes restricciones de maniobrabilidad del UAV, además de criterios de continuidad de curvas (el problema de continuidad se refiere principalmente a la continuidad geométrica, en términos de continuidad tangencial o de curvatura), suavidad en las curvas (una curva es suave si sus derivadas son continuas en el intervalo definido) y la seguridad en el vuelo (el control de seguridad garantiza que una trayectoria suave esté suficientemente lejos de los obstáculos). Finalmente, la cinemática del movimiento de los vehículos es otro factor que debe ser considerado mientras se suavizan las trayectorias. El presente trabajo está enfocado en la creación de trayectorias navegables en el espacio 3D, para UAVs de características no-holonómicas. La principal dificultad al solventar este problema se debe a la movilidad de esta clase de UAVs, pues se ven obligados a avanzar sin la posibilidad de detenerse a través de trayectorias 3D, realizando curvas con curvaturas limitadas (una máxima capacidad de giro a una velocidad definida). En consecuencia, se han desarrollado las herramientas necesarias para proporcionar una completa caracterización de trayectorias óptimas (con un radio de giro limitado) para UAVs que se mueven en el espacio 3D a una velocidad constante. Esta tesis se centra en la generación de caminos con trayectorias navegables en el espacio Euclídeo 3D, que contenga curvas con curvatura continua, considerando de esta manera las restricciones cinemáticas de los UAVs. Por tal motivo el objetivo principal es el desarrollo de la matemática necesaria para definir curvas clotoides en el espacio tridimensional, de modo que puedan ser utilizadas como primitivas en la generación de trayectorias. Finalmente, culminado el desarrollo de esta herramienta básica, y en función de los obstáculos del entorno, se puede completar una planificación y replanificación activa de movimientos. Para complementar la investigación, la verificación de las herramientas de planificación de trayectorias y del sistema, se han realizado simulaciones con la ayuda del entorno de desarrollo integrado (IDE) Matlab. De la misma forma, se ha preparado una plataforma de simulación de vuelo, tomando las virtudes del simulador de vuelo FlightGear 2018, y el modelo dinámico del avión de ala fija con restricciones no-holonómicas (Kadett 2400 ). En cuanto a la generación de trayectorias 3D, se han desarrollado simulaciones off-line, donde las acciones de control que debe ejecutar el avión para que siga la trayectoria calculada son definidas por: acceleración, brusquedad de curvatura y brusquedad de torsión. Por último, el enfoque de revisión bibliográfica presente en este documento se ha centrado en trabajos realizados que buscan cumplir con las tareas de planificación. / [CA] El desenvolupament tecnològic en la creació de trajectòries que permeten navegació lliure de col·lisions de Vehicles Autònoms (AVs) ha estat un objectiu constant d'estudi a causa del seu fort interés científic i tecnològic en les últimes tres dècades. Les diferents classes d'AVs, ja siguen Vehicles Aeris no Tripulats (UAVs), Vehicles Terrestres no Tripulats (UGVs) o Vehicles Submarins no Tripulats (UUVs), fomenten el desenvolupament i la implementació de trajectòries a l'espai tridimensional (3D). Un grup especial de tecnologia UAV està caracteritzat per la seua ala fixa, cosa que destaca característiques particulars en els AVs, a causa de les restriccions no-holonòmiques (un sistema que es descriu mitjançant un conjunt de paràmetres subjectes a restriccions diferencials que no permeten que un vehicle es menege de forma instantània en qualsevol direcció). En aquest sentit, les trajectòries navegables per a aquests UAVs no han de ser construïdes com un conjunt de línies rectes i cercles com a la gran majoria de planificadors basats en primitives, ja que no es garanteix una continuïtat en la seua curvatura. Per tant, les trajectòries construïdes per a aquesta branca tecnològica han de ser resoltes considerant les diferents restriccions de maniobrabilitat de l'UAV, a més de criteris de continuïtat de corbes (el problema de continuïtat es refereix principalment a la continuïtat geomètrica, en termes de continuïtat tangencial o de curvatura), suavitat a les corbes (una corba és suau si les seves derivades són contínues en l'interval definit) i la seguretat en el vol (el control de seguretat garanteix que una trajectòria suau estiga prou lluny dels obstacles). Finalment, la cinemàtica del moviment dels vehicles és un altre factor que cal considerar mentre se suavitzen les trajectòries. Aquest treball està enfocat a la creació de trajectòries navegables a l'espai 3D, per a UAVs de característiques no-holonòmiques. La principal dificultat en solucionar aquest problema es deu a la mobilitat d'aquesta classe de UAVs, ja que es veuen obligats a avançar sense la possibilitat d'aturarse a través de trajectòries 3D, fent corbes amb curvatures limitades (una màxima capacitat de gir a una velocitat definida). En conseqüència, s'han desenvolupat les ferramentes necessàries per proporcionar una completa caracterització de trajectòries òptimes (amb un radi de gir limitat) per a UAVs que es mouen al pla 3D a una velocitat constant. Aquesta tesi se centra en la generació de camins amb trajectòries navegables a l'espai Euclidià 3D, que continguen corbes amb curvatura contínua, considerant així les restriccions cinemàtiques dels UAVs. Per aquest motiu, l'objectiu principal és el desenvolupament de la matemàtica necessària per definir corbes clotoides a l'espai tridimensional, de manera que puguen ser utilitzades com a primitives en la generació de trajectòries. Finalment, culminat el desenvolupament d'aquesta ferramenta bàsica, i en funció dels obstacles de l'entorn, es pot completar una planificació i una replanificació activa de moviments. Per complementar la investigació, la verificació de les ferramentes de planificació de trajectòries i del sistema, s'han fet simulacions amb l'ajuda de l'entorn de desenvolupament integrat (IDE) Matlab. De la mateixa manera, s'ha preparat una plataforma de simulació de vol, prenent les virtuts del simulador de vol FlightGear 2018 i el model dinàmic de l'avió d'ala fixa amb restriccions no-holonòmiques (Kadett 2400). Pel que fa a la generació de trajectòries 3D, s'han desenvolupat simulacions off-line, on les accions de control que ha d'executar l'avió perquè seguisca la trajectòria calculada són definides per: acceleració, brusquedat de curvatura i brusquedat de torsió. Finalment, l'enfocament de revisió bibliogràfica present en aquest document s'ha centrat en treballs realitzats que busquen complir les tasques de planificació de trajectòria, planificació de moviment i construcció de corbes suaus per a AVs. / [EN] The technological development in the creation of trajectories that allow collision-free navigation of Autonomous Vehicles (AVs) has been a continuous target of study due to its strong scientific and technological interest in the last three decades. Different classes of AVs, whether, Unmanned Aerial Vehicles (UAVs), Unmanned Ground Vehicles (UGVs) or Unmanned Underwater Vehicles (UUVs), encourage the development and implementation of paths in three-dimensional (3D) space. A special group of UAV technology is characterized by its fixed wing, which emphasizes particular characteristics in UAVs, due to non-holonomic constraints (a system that is described by a set of parameters subject to differential constraints that do not allow a vehicle to move instantaneously in any direction). In this sense, navigable paths for these UAVs should not be built as a set of straight lines and circles as in the vast majority of primitive-based planners, since no continuity in their curvature is guaranteed. Therefore, the paths built for this technology branch must be solved considering the different maneuverability constraints of the UAV, in addition to curve continuity criteria (the continuity problem refers mainly to geometric continuity, in terms of tangential or curvature continuity), curve smoothness (a curve is smooth if its derivatives are continuous in the defined interval) and flight safety (safety control ensures that a smooth path is sufficiently far away from obstacles). Finally, the kinematics of vehicle motion is another factor to be considered while smoothing paths. This thesis work is focused on the creation of navigable paths in 3D space for UAVs with non-holonomic characteristics. The main difficulty in solving this problem is due to the mobility of this kind of UAVs, since they are forced to move without the possibility of stopping through 3D paths, performing curves with limited curvatures (a maximum turning capacity at a defined speed). Consequently, the needed tools have been developed to provide a complete characterization of optimal paths (with a limited turning radius) for UAVs moving in the 3D plane at a constant velocity. This thesis focuses on the generation of paths with navigable trajectories in 3D Euclidean space, containing curves with continuous curvature, thus considering the kinematic constraints of UAVs. Therefore, the main aim is the development of the necessary mathematics to define clothoid curves in the three-dimensional space, so that they can be used as primitives in the generation of paths. Finally, once the development of this basic tool has been completed, and depending on the obstacles in the environment, an active planning and replanning of movements can be completed. To complement the research, the verification of the path planning tools and the system, simulations have been performed with the help of the integrated development environment (IDE) Matlab. In the same way, a flight simulation platform has been prepared, taking the virtues of the FlightGear 2018 flight simulator, and the dynamic model of the fixed-wing aircraft with non-holonomic constraints (Kadett 2400 ). Regarding the generation of 3D paths, off-line simulations have been developed, where the control actions to be executed by the aircraft to follow the calculated path are defined by: acceleration, curvature sharpness and torsion sharpness. Finally, the literature review approach presented in this document has focused on works that address the tasks of path planning, motion planning and construction of smooth curves for AVs. Special care has been taken in the methodologies used, the variety of techniques, in addition to the advantages and disadvantages presented throughout the literature review. / The authors are grateful to the financial support of Spanish Ministry of Economy and European Union, grant DPI2016-81002-R (AEI/FEDER, UE). This work was also supported by the postdoctoral fellowship “APOSTD/2017/055” and the local administration “GV/2017/029” (Generalitat Valenciana, Conse- lleria d’Educació) Valencia - Spain. / Vanegas Zabala, GI. (2024). Generación de maniobras suaves en el espacio 3D [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/203122 / Compendio

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[pt] Nesta tese, a teoria das hastes de Cosserat é revisitada e aplicada à dinâmica de coluna de perfuração. O objetivo é estudar o comportamento dessas estruturas dentro de poços de petróleo curvos. Para atingir este objetivo, um modelo estrutural determinístico é construído onde as tubos de perfuração (drill-pipes) e o conjunto de fundo (bottom hole assembly) são considerados como uma estrutura unidimensional de Cosserat. Em seguida, é desenvolvida uma estratégia para tratar o contato lateral em poços com configuração curvilínea. Depois disso, o problema de contorno livre é tratado mediante uma estratégia que considera como a condição de borda evolui à medida que a estrutura de perfuração avança. Isto é feito mediante uma formulação de interação broca-rocha que deve considerar a dinâmica de corte. Para isso, uma equação extra, de advecção, é resolvida junto com as equações de movimento de Cosserat. Em seguida, alguns casos de aplicação são apresentados. Numa primeira instancia, alguns elementos do problema são avaliados separadamente. Seguidamente, eles são integrados e analisados de forma conjunta. Por exemplo, primeiramente uma coluna de perfuração sem contato de fundo (off-bottom) é simulada, ou seja, sem contato broca-rocha, para estudar o comportamento e a implementação da estratégia para o contato lateral. Aqui também são calibrados alguns dos parâmetros do modelo de atrito. Em seguida, a estratégia para contabilizar o corte na rocha é implementada em um modelo 2-DOF de baixa dimensão e em um semi-discreto onde a dinâmica de torção é modelada como uma equação de onda. Os resultados mostram que o uso de abordagens contínuas resulta mais apropriade que aquelas onde se utilizam modelos de baixa dimensãom, particularmente quando são consideradas colunas longas, e quando há interesse em analisar não apenas o comportamento da broca, mas também o comportamento do sistema mecânico ao longo dos tubos de perfuração. Isso é reforçado por outro exemplo onde a dinâmica de corte é combinada com a formulação de Cosserat. Observações semelhantes do ponto de vista qualitativo são encontradas. Resumindo os resultados obtidos, as diferenças nas previsões dadas pelos modelos de baixa dimensão e o de unidimensional de Cosserat justificam o desenvolvimento e aplicação da abordagem com esta formulação em estruturas de perfuração. Finalmente, a modo de introduzir outro aspecto importante em colunas de perfuração e que pode ser uma linha de pesquisa para continuar o trabalho, a variabilidades presente em elementos como rocha, inclui-se um caso de aplicação considerando um poço horizontal e um campo estocástico de atrito. / [en] In this thesis, the theory of Cosserat rods is applied to the dynamics of drill-strings. The main objective is to evaluate the behaviour of these strings when they move within curved wells. To achieve this goal, a deterministic structural model is constructed, where the drill-pipes and the bottom hole assembly are taken as a Cosserat rod. Next, a strategy to deal with the lateral contact in curved well configurations is developed. After that, the free boundary problem is assessed: while drilling, the boundary changes due to cutting, modifying the position of the soil and, consequently, changing the bit-rock interaction forces. For this reason, a bit-rock model that can account for the cutting dynamics is adopted, in which an extra advection equation is solved together with the equations of motion of the Cosserat rod. Next, application cases are provided. First, some effects included in the model are tested in isolation, such as the lateral friction, the lateral contact, and the cutting. After that, they are all combined. In the first analysis, an off-bottom string is simulated, i.e. without contact at the bit. This allows testing the formulation associated with the lateral contact. Also, the calibration of the lateral friction parameters is made. Following that, the strategy to account for the cutting at the bit is implemented in a low-dimensional 2-DOF model, and in a semi-discrete model with a continuous wave equation for the torsional dynamics. The results show that the use of continuous approaches is more appropriate than low-dimensional models. Especially when long columns are considered, and when there is interest in understanding not only the behaviour at the bit but also along drill-pipes. This finding is reinforced by another application where the cutting dynamics are combined with the Cosserat rod formulation. Again, similar observations from a qualitative point of view are found. Overall, the differences in the results between the lumped low-dimensional models and the continuous Cosserat rod justify the development and application of the Cosserat approach to drilling structures. Finally, an introductory stochastic analysis concerning the variability of the rock is presented as an introduction to a future line of research, where stochasticity is included. / [es] En esta tesis, la teoria de Cosserat para elementos unidimensionales es revisitada y aplicada a la simulación de columnas de perforación. El objetivo es estudiar el comportamiento de estas estructuras en pozos de geometría curva. Para alcanzar este objetivo se construye un modelo determinístico. En este modelo, los caños de perforación (drill-pipes) y el conjunto de fondo (bottom hole assembly) son modelados como una estructura unidimensional de Cosserat. Seguidamente, una estrategia para tratar con el contacto lateral en pozos curvos es desarrollada. Luego, el problema de frontera libre es estudiado: durante la perforación, la condición de borde cambia debido al cambio del perfil altimétrico del terreno, alterando su posición y consecuentemente las fuerzas asociadas a la interacción broca-roca. Por esta razón, se decide utilizar un modelo de interacción broca-roca que tiene en cuenta la dinámica del corte. En este abordaje una ecuación extra, la ecuación de advección, es resuelta en forma acoplada con las ecuaciones del movimiento de la estructura de Cosserat. Algunos ejemplos de aplicación son presentados. En una primera instancia, algunos de los elementos del problema son estudiados en forma aislada. Luego combinados en un modelo completo. Por ejemplo, el caso de una columna sin contacto de fondo (off-bottom) es tratado para evaluar el comportamiento y la implementación de la estrategia mencionada para detectar el contacto lateral. Además, se efectúa la calibración de alguno de los parámetros relacionados con la fricción lateral. Luego, la estrategia para considerar el corte en la punta es implementada en un modelo de 2-DOF, y en otro semi-discreto donde se considera un modelo de ecuación de onda para la dinámica torsional. Los resultados muestran que el uso de formulaciones continuas es más apropiado que aquellas formulaciones donde se utilizan modelos de dimensiones reducidas, particularmente cuando se estudia columnas largas donde el interés se centra en entender no solo el comportamiento de la broca sino también a lo largo de la tubería. Este resultado es reforzado por otro caso de aplicación en donde se combina la dinámica de corte con un modelo de Cosserat. Observaciones similares son vistas en el comportamiento cualitativo de la solución. En resumen, las diferencias observadas en los diferentes ejemplos de aplicación entre los modelos de dimensiones reducidas y el modelo continuo de Cosserat justifican el desarrollo y la aplicación de la teoría de Cosserat a estructuras de perforación. Finalmente, dado que uno de los objetivos planteados también es considerar la variabilidad en algunos elementos como ser las propiedades de la roca, un caso de aplicación considerando un pozo horizontal es mostrado.