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A Novel Robust Hexarotor Capable of Static Hovering in Presence of Propeller Failure
No full textInternational audienceThis paper presents a novel open source design of the Y-shaped hexarotor Unammend Aerial Vehicle (UAV), and proves both in theory and real experiments its robustness to the failure of any of its propellers. An intuitive geometrical interpretation of UAV static hovering ability is presented, through which the robustness of different coplanar/collinear hexarotor designs is analyzed. Following the presented geometrical interpretation, we also show a method to render the Star-shaped hexarotor robust to the failure of some of its propellers, while showing its incapability to static hover in the case of the failure of any of its propellers. Finally, the efficiency of the Y-shaped and Star-shaped hexarotors are tested experimentally, and conclusions on the advantages and disadvantages of the two designs are drawn
Sensitivity analysis in general metric spaces
No full textInternational audienceIn this paper, we introduce new indices adapted to outputs valued in general metric spaces. This new class of indices encompasses the classical ones; in particular, the so-called Sobol indices and the Cramér-von-Mises indices. Furthermore, we provide asymptotically Gaussian estimators of these indices based on U-statistics. Surprisingly, we prove the asymp-totic normality straightforwardly. Finally, we illustrate this new procedure on a toy model and on two real-data examples
Fisher-Rao geometry of Dirichlet distributions
No full textInternational audienceIn this paper, we study the geometry induced by the Fisher-Rao metric on the parameter space of Dirichlet distributions. We show that this space is geodesically complete and has everywhere negative sectional curvature. An important consequence of this negative curvature for applications is that the Fréchet mean of a set of Dirichlet distributions is uniquely defined in this geometry
High dimensional multidisciplinary design optimization with Gaussian process for eco-design aircraft
No full textInternational audienceThe European project AGILE 4.0 (https://www.agile4.eu/) is developing methodologies to opti mize complex aeronautical systems addressing the entire life cycle. It will provide aircraft industry with solutions to reduce significantly the cost and the quantity of energy expended by aircraft, moving towards cheaper and greener solutions.Aeronautics design is especially multidisciplinary and, in this context, some integer or categorical variables could arise such as the number of engines, the shape of the tail or the type of the wingtip devices. To tackle this class of problems, new mixed integer multidisciplinary efficient global optimization algorithms have recently been developed. We propose to tackle mixed integer optimization and its application to aeronautic design. The problem will be treated as an expensive black-box that we try to optimize with as few evaluations as possible and with both a large number of design variables (∼700) and many constraints (∼20). The constraints can be inequalities or equalities and we will consider no convexity assumption.This work follows the PhD thesis of R.Priem (2017-2020) in which an adaptative efficient global optimization method under constraint (enrichment algorithm) was developed. The latter extends the stochastic efficient optimization to both equality and inequality constraints. This approach was evaluated on a large battery of academic tests and validated at an industrial scale on the BRAC test case of Bombardier Aviation, Canada.Bayesian optimizers that handle both continuous and categorical inputs are of high interest, yet pose significant challenges. Current approaches, like one-hot encoding, severely increase the dimension of the covariance matrix related to the Kriging model, also known as Gaussian Process.In this context, the construction of the Kriging model may not be scalable to practical applications involving multiple categorical variables. In fact, using the surrogate model in the standard way is computationally expensive due the the large number of hyperparameters to estimate in the covariance matrix.To begin with, in this PhD thesis (2020-2023), we address this issue by constructing a covariance kernel for the Kriging model that depends on only a few hyper-parameters. The new kernel is constructed using continuous relaxation and based on information obtained from the Partial Least Squares method. In the classical approach the mixed problem is modeled by a Multi-Arm Bandit where every arm is a discrete category and corresponds to a continuous space evaluate via conditional probabilities.A benchmark of functions was proposed to validate the method and new results were obtained on a reference model of a A320 aircraft design problem. The obtained numerical results lead to a significant computational gain without jeopardizing the performance of the regarded Bayesian optimization solver.Regarding the approaches, many ways of improvement are being considered. A possible improvement for optimization is to correctly estimate mixed probability distributions. In addition, the thesis of J. Pelamatti (2017-2020) made it possible to explore many variants of Gaussian process models using covariance kernels adapted to mixed integer variables.Two direct applications of this thesis are the optimization of a flexible wing aircraft and that of a hybrid propulsion aircraft which will serve as test cases for developed algorithms.Taking into account mixed variables in aeronautical design optimization will allow to obtain more efficient aircraft configurations, such as in the aircraft concept DRAGON aiming at reducing fuel consumption through distributed electric propulsion
Routeur embarqué pour les communications critiques aéronautiques en environnement multi liens
No full textCritical aeronautical communications are a major issue for flight safety. For a long time, these have relied solely on voice, which is transmitted via an analog communication system. Given the growth in air traffic, this mean of communication has reached saturation and moreover, it has sometimes shown its limits in terms of understanding voice messages, hence the need to find an alternative method. The development of communication technologies based on digital signals allows text messages to be exchanged over a long distance. Initially reserved for non-critical airline operations, it was quickly adopted for communications between the pilot and the air traffic controller, in order to offload the dedicated radio channel. This is known as Data Link. This system, included in a more global infrastructure called the ATN/OSI, has the double advantage of relieving congestion on the frequencies used, but also of limiting the misunderstanding of certain messages. The next evolutions of this aeronautical communication system based on the IP suite and called ATN/IPS is under development. It will have to solve certain problems by proposing new communication technologies and innovative network solutions that can adapt to the increase in critical air data traffic. In this thesis, we address several issues related to the development of ATN/IPS. The first one concerns the network mobility of the aircraft. Indeed, the ATN/IPS will gather several operators, each providing their own sub-networks composed of one or more access methods. Given the limited range of some of them, an aircraft necessarily needs to use several of them during a flight. A handover is triggered as soon as an aircraft connects to a new ground station, which in some cases requires a change in routing to the aircraft. We propose to combine and adapt two mobility protocols, PMIPv6 and LISP, to guarantee continuity of critical data transmission while minimizing the impact on the avionics architecture and the radio communication channel. Our solution is compared to a standard IP mobility solution in a simulated network environment and specifically developed under OMNeT++. The results show that our approach reduces the handover delay, while lightening the signaling traffic on the radio channel. Moreover, in order to propose the best aircraft connectivity, we propose an automation of the selection of the best links in the multilink and ATN/IPS context. Typically, multilink algorithms (or link selection) are split into three parts : collecting link information, deciding which links to use, and using the new links. As the mobility solution proposed in this thesis is also compatible with multilink, we are interested in the first two steps. We propose to use an active method to probe the links and estimate their quality. This approach has the advantage of being independent of the underlying communication technologies. We then compare three estimation methods based on round trip delay and evaluate the performance of each of them. The first method is based on threshold determination, the second is based on a probabilistic model and the third uses supervised learning. This learning-based method makes it possible to estimate the link over time with good precision. Finally, we propose a link selection algorithm in the case where the primary link no longer meets the quality of service requirements.Les communications critiques aéronautiques constituent un enjeu majeur pour la sécurité des vols aériens. Pendant longtemps, celles-ci se reposaient uniquement sur la voix, qui est transmise via un système de communication analogique. Compte-tenu de la croissance du trafic aérien, ce moyen de communication est arrivé à saturation et de plus il a parfois montré ses limites en terme de compréhension des messages vocaux, doù la nécessité de trouver une méthode alternative. Lessor des technologies de communication basées sur des signaux numériques permet déchanger des messages textuels sur une longue distance. Au départ réservé pour les opérations des compagnies aériennes non critiques, il a vite été adopté pour les communications entre le pilote et le contrôleur aérien, afin de décharger le canal radio dédié. On parle alors de Data Link. Ce système, inclus dans une infrastructure plus globale appelée ATN/OSI, a le double avantage de désengorger les fréquences utilisées mais aussi de limiter la mauvaise compréhension de certains messages. Les prochaines évolutions de ce système de communication aéronautique basé sur la suite IP et appelé ATN/IPS est en cours de développement. Il devra résoudre certains problèmes en proposant de nouvelles technologies de communication et des solutions réseaux innovantes pouvant s'adapter à laccroissement du trafic de données critiques aériennes. Dans cette thèse, nous adressons plusieurs problématiques liées au développement de lATN/IPS. La première concerne la mobilité réseau de lavion. En effet, lATN/IPS regroupera plusieurs opérateurs fournissant chacun leur propres sous-réseaux composés dune ou plusieurs méthodes daccès. Etant donné la portée limitée de certaines dentre elles, un avion a nécessairement besoin den utiliser plusieurs lors dun vol. Un transfert intercellulaire (handover) est déclenché dès lors quun avion se connecte à une nouvelle station sol, entraînant dans certains cas la nécessité de modifier le routage vers celui-ci. Nous proposons dassocier et d'adapter deux protocoles de mobilité, PMIPv6 et LISP, afin de garantir la continuité de la transmission des données critiques tout en minimisant limpact sur larchitecture avionique et le canal radio de communication. Notre solution est comparée à une solution standard de mobilité IP dans un environnement réseau simulé et spécifiquement développé sous OMNeT++. Les résultats démontrent que notre approche permet de réduire le délai du handover, tout en allégeant le trafic de signalisation sur le canal radio. De plus, afin de proposer la meilleure connectivité de lavion nous proposons une automatisation de la sélection des meilleurs liens dans le contexte multilink et ATN/IPS. Généralement, les algorithmes de multilink (ou sélection de liens) sont découpés en 3 parties : la collecte des informations de liens, la décision des liens à utiliser, et lutilisation des nouveaux liens. La solution de mobilité proposée dans cette thèse étant aussi compatible avec le multilink, nous nous intéressons aux 2 premières étapes. Nous proposons dutiliser une méthode active pour sonder les liens et estimer leur qualité. Cette approche a lavantage dêtre indépendante des technologies de communication sous-jacentes. Nous comparons ensuite 3 méthodes destimation basées sur le délai daller-retour et évaluons les performances de chacune dentre elles. La première méthode repose sur une détermination par seuils, la deuxième s'appuie sur un modèle probabiliste et la troisième utilise l'apprentissage supervisé. Cette méthode par apprentissage permet destimer le lien sur la durée avec une bonne précision. Enfin, nous proposons un algorithme de sélection de liens dans le cas où le lien primaire ne répond plus aux exigences de qualité de service
State of the Art on Computer-Supported Collaborative Work (CSCW), Situation Awareness (SA) and Human-Automation Teaming (HAT) for the SESAR ER2 AEON (Advanced Engine-Off Navigation) Project
No full textUse of new technology in order to increase security, efficiency, and effectiveness of airports: case study of Secure Boarding Project at Brazilian Airports
No full textThe continuous increase of passenger’s flow requires new processes, new technology and a level of interaction and coordination between civil aviation stakeholders, especially government agencies, airports and airlines operators to provide facilitation, focused on enabling a faster, seamless flow of passengers, baggage, and cargo while enhancing safety and security through the airport facilities, and improving airlines' customer experience and satisfaction. Regarding the future vision for international air travel, a range of innovative identity projects is being developed. This fact indicates that the industry is increasingly concerned with addressing the growing needs of passengers related to innovation, frictionless travel experience, improvement of disruption management and streamlining the baggage handling process, as presented in the International Air Transport Association (IATA) 2019 survey, which explores passenger preferences and frustrations across the air travel experience. Furthermore, the impact of the sanitary measures required with the advent of the COVID-19 pandemic tends to make this type of technology even more necessary. In this context, this study project aimed at conducting broad literature review of scientific studies comprising the concept of airport function, the actual passenger process, aspects about security control and facilitation, the use of technologies on air transportation, the impact of COVID-19 pandemic on the processes and in the future of civil aviation. Besides that, this study aims to define a implementation project roadmap, analyse the results of the “Passenger Perception Survey about the Covid-19 Pandemic” conducted in Brazil during the second semester 2020, as well as, propose parameters and evaluate the development of a pilot project deployed at two Brazilian Airports of the Secure Boarding Project, a project that will implement Biometric Boarding using Identity as a Service (IDaaS), through the validation of travellers’ identity through the passenger biometric capture at the time of check-in, comparing it with the biometric record contained in the Government databases
Proposed framework for normal operations audits of accredited flight exams in Brazil
No full textICAO, since its beginning, has regulated personell licensing. Am important part of this are pilot flight exams, which cane assess flight skills. The role of the flight examiner is central in order to support the usefullness of proficiency exams. Exams cane be performed by accredited examiners, but Civil Aviation Authorities must assure that they perform as required by closely supervising the activity. ICAO has some frameworks for normal operations surveilance, but flight school exams can present a chalenger environment for presencial supervision. Therefore, by finding that transit departments in Brazil record proficiency exams in video, the study focused on evaluating the possibility and usefulness of video recording accredited flight exams. After personally recording and with colaboration of a flight school and a student pilot, the conclusion is that video recording exams is not only possible but, if some constraints are stablished, it could be a great source of data for licensing system evolution. To do so, there should be a regulatory action, aligned with colaboration with industry on how to collect, analyze and use data
Code-Based Cryptography
No full textInternational audienceThis chapter focuses on the essentials of code-based cryptography and on coding theory and the associated hard problems useful for cryptography as well as more recent proposals for public-key cryptography, key-exchange protocols, and digital signatures. Code-based cryptography was originally proposed using the standard Hamming metric. The M. Ajtai–C. Dwork cryptosystem also inspired the Learning with Errors lattice-based cryptosystem by O. Regev which generated a huge amount of research in lattice-based cryptography. While Hamming Quasi-Cyclic has the advantage of relying only on the hardness of the (decisional) syndrome decoding problem for random quasi-cyclic codes, it still features big keys for low encryption rates. In 2003, M. Alekhnovich proposed an innovative approach based on the difficulty of decoding purely random codes. Among many broken families in the R. J. McEliece framework, it is interesting to notice that up to now there is no specific attack when considering the smaller BCH code family rather than Goppa codes
Design of Iterative Demapping Schedules for Reduced-Complexity BICM-ID with Binary LDPC Codes and Orthogonal Modulations
No full textInternational audienceLDPC-coded modulations are attractive solutions for many communications links. BICM provides a very simple, flexible yet effective way of combining binary channel codes with non-binary modulations. However, iterative demapping is sometimes necessary to increase the coding gains. This is especially the case for orthogonal modulations where the "BICM capacity" falls far away from the coded modulation capacity. Unfortunately, iterative demapping results in a significant computational cost. A pragmatic solution to reduce this computational cost aims at restricting the number of demapping activations. In this article, a strategy to compute the minimum number of demapping activations necessary for a target estimated BER performance is presented and results are introduced for BICM-ID with binary LDPC-coded orthogonal modulations. Iterative demap-ping schedules optimized for a limited number of demapper activations are designed and evaluated in the finite code length regime