Organická elektronika a bioelektronika zažívá v moderním věku obrovskou snahu o vývoj nových organických materiálů s vlastnostmi, které běžná elektronika na bázi křemíku obvykle nedosahuje. Tato práce se zabývá syntézou a charakterizací nových organických materiálů pro organickou elektroniku. Zaobírá se přípravou nových pentafluorsulfanylových heterocyklických stavebních bloků, alkylovaných vysokoúčinných organických pigmentů a bioinspirovaných organických -konjugovaných materiálů s modifikovatelnými fyzikálně-chemickými vlastnostmi a racionálními syntetickými přístupy k jejich přípravě. Pentafluorsulfanylová skupina (SF5) je ceněna pro svou vysokou elektronegativitu, lipofilitu, tepelnou a chemickou stabilitu. Pozitivně ovlivňuje optické a elektronické vlastnosti, rozpustnost a stabilitu v často lepší míře než u zavedených CF3-analogů. Šesti a čtyřkrokovou syntézou byly připraveny dva typy derivátů 3-SF5-substituovaných pyrrolidinů, které mohou sloužit jako všestranné stavební jednotky pro začlenění do pokročilých aromatických a heteroaromatických -konjugovaných systémů prostřednictvím atomů dusíku jako fluorované terminální skupiny. Modelový derivát byl zaveden jako terminální skupina do elektronově chudého heteroaromatického systému nukleofilní substitucí. Vodíkovými můstky vázané vysokovýkonné organické pigmenty přitahují velkou pozornost díky svým působivým polovodivým vlastnostem, silné 2D molekulární asociaci, vysoké tepelné, chemické a fotochemické stabilitě a nízké toxicitě. Přesto jsou pouze omezeně rozpustné a zpracovatelné, což lze vyřešit zavedením solubilizačních skupin. Je známo, že obzvláště objemné rigidní skupiny nesoucí adamantyl zlepšují uspořádání molekulární struktury, tepelnou stabilitu a výsledné vlastnosti díky samoorganizační schopnosti adamantanu. Adamantylmethylová a adamantylethylová skupina byla zavedena do vybraných barviv a pigmentů ze skupiny karbonylových azaacenů, rylen-diimidů a indigoidů pomocí nukleofilní substituce se zaměřením na zvýšení rozpustnosti a zpracovatelnosti při zachování tepelné stability a efektivní molekulární organizaci v pevné fázi. Fyzikálně-chemické studie série derivátů quinacridonu a epindolidionu ukázaly srovnatelnou, nebo vyšší tepelnou stabilitu než u nesubstituovaných derivátů, dobrou rozpustnost v organických rozpouštědlech, silnou fluorescenci v pevné fázi a roztoku v oblasti VIS a unikátní krystalovou strukturu pozorovanou z RTG analýzy. Flaviny jsou všudypřítomné bioinspirované organické materiály s nepostradatelnými biologickými funkcemi, výhodnými fyzikálně-chemickými vlastnostmi, chemickou a aplikační všestranností. Cílem práce byla modifikace optických, elektronických, elektrochemických, tepelných a dalších vlastností rozšířením -konjugovaného systému syntetizovaných materiálů. V první fázi byly navrženy dva syntetické přístupy pro přípravu série NH-nesubstituovaných flavinů, u kterých byly provedeny komplexní fyzikálně-chemické studie. Poté byly navrženy dva přístupy k syntéze N,N'-dialkylovaných flavinů s inkorporovaným butylovým, adamantylethylovým a triethylenglykolovým substituentem. Alkylací byla zvýšena rozpustnost v organických rozpouštědlech a vodném prostředí, zesílena fluorescence v pevné fázi a v roztocích a modifikovány tepelné vlastnosti v závislosti na zavedeném alkylovém substituentu.

<p>  </p> <p>As space agencies look to conduct more scientific missions beyond Earth orbit, low-cost access to space becomes indispensable. Small satellites (smallsats) fulfill this need as they can be developed at a fraction of the cost of traditional large satellites. Consequently, smallsats are being envisioned for planetary science missions at several destinations including Mars. However, a significant challenge for interplanetary smallsats is performing fully-propulsive orbit insertion because modern smallsat propulsion technologies have limited total velocity change capabilities. At destinations with significant atmospheres, this challenge can be circumvented via <em>aerocapture</em>, a technique that uses a single atmospheric pass to convert a hyperbolic approach trajectory into a captured elliptical orbit. Aerocapture has been shown to enable significant propellant mass savings as compared to fully-propulsive orbit insertion, making it an attractive choice for smallsats. Performing aerocapture with smallsats requires a suitable vehicle design that satisfies the associated control requirements and volumetric constraints. To address this requirement, this dissertation proposes the <em>morphable entry system </em>(MES), a conceptual deployable entry vehicle that utilizes shape morphing to follow a desired atmospheric flight profile during aerocapture. The aerocapture performance of the MES at Mars is investigated using a six degree-of-freedom aerocapture simulation environment. The shape morphing strategy employed by the MES is shown to be feasible for targeting desired angle of attack and sideslip angle profiles that lead to successful orbit captures. Furthermore, the robustness of the MES to simulated day-of-flight uncertainties while employing angle of attack control is demonstrated through a Monte Carlo dispersion analysis. The major contributions of this research as well as areas of future work are described.</p>

Les zones blanches étendues sont de vastes espaces géographiques (forêts, déserts), sans ou ayant très peu d’infrastructures telles que les routes, les réseaux électriques ou de télécommunication. Cependant, très souvent, dans ces zones se développent de nombreuses activités économiques ou environnementales telles que le monitoring de l’environnement, la surveillance d’une frontière ou d’une installation de pipeline, ou encore la prévention des feux de forêt. Grâce aux techniques de télédétection et de communication, une fonction clé de ces activités repose sur la collecte d’informations issues de capteurs qui sont transmises à un centre d’analyse distant. Nous proposons des solutions réseau afin d’effectuer la collecte de ces données dans les zones blanches étendues grâce à des technologies de communication longue distance et faible énergie, de type LoRaWAN. Pour le problème du déploiement du réseau de capteurs sans fil dans ces zones difficiles, nous avons proposé une heuristique inspirée de la croissance biologique d’un champignon, le physarum. Le physarum est capable de créer un corps complexe de liens pour trouver de la nourriture nécessaire à sa survie tout en optimisant ses propres ressources corporelles lors des périodes de disette. Ce principe d’optimisation a été adapté au domaine des réseaux pour déployer un réseau tolérant aux fautes, tout en minimisant le nombre de ressources ou relais à placer sur la zone d’intérêt. Nous nous sommes ensuite intéressés à la collecte opportuniste de données dans les zones blanches afin de pouvoir collecter l’information des nœuds trop éloignés d’une station relais. Nous avons développé une méthode de collecte basée sur les avions de ligne qui survole le territoire. Durant une fenêtre de communication, l’avion est à portée d’un capteur et peut ainsi collecter les données stockées qui seront livrées au serveur à l’atterrissage de l’avion. Notre dernière contribution utilise conjointement les deux méthodes précédentes, pour permettre à la fois le déploiement du réseau et la collecte des capteurs isolés. / Although wide white areas are not equipped or sparsely equipped with any infrastructure (energy, roads ...), strategic human activities are being carried out such as mines, forest, pipeline... To tackle the problem of deploying sensor networks in a very large area where few infrastructures are available, we propose a network deployment algorithm which aims at efficiently linking sparse points of interest in a very wide white area. The originality of the proposed method is that it mimics the evolution of a type of mold called physarum. Secondly, we aim at overcoming the deployment problem in wide white areas by using long range communication between an aircraft and earth. The new data collection scheme he proposes is based on the use of commercial flights to collect data while they cross over an area of interest. It investigates the feasibility of such a scheme by determining the collection capacity of commercial aircraft in different locations of the desert. Finally, we mixed both solutions do repatriate data from sensors not covered by any flight to a covered data sink that relays data to the aircraft.

Questa tesi di dottorato studia l’interazione della cooperatività con il rumore in sistemi realistici, focalizzandosi principalmente sulla superradianza. Gli effetti cooperativi emergono dall’interazione collettiva di un insieme di elementi con un campo esterno. Esempi degni di nota sono la superconduttività, dove le coppie di Cooper elettroniche interagiscono con le vibrazioni reticolari, le eccitazioni di plasma, che sorgono dall'interazione collettiva degli elettroni in un metallo con il campo coulombiano, e la superradianza, ovvero quel processo di emissione spontanea cooperativa che sorge da un aggregato di emettitori identici. Gli effetti cooperativi sono tipicamente robusti al disordine e al rumore, cosa che li rende interessanti per delle applicazioni a dispositivi quantistici che possano operare a temperatura ambiente. In questo lavoro, inizialmente, introduciamo un formalismo di “master equations” che descrive l’accoppiamento collettivo di un aggregato di emettitori/assorbitori con il campo elettromagnetico, valido quando le dimensioni dell'aggregato sono sia maggiori che minori della lunghezza d’onda emessa/assorbita. Inoltre, il formalismo è valido per accoppiamento sia debole che forte con il campo elettromagnetico e, cosa più importante, permette di descrivere correttamente la superradianza in diversi regimi. In tale formalismo, studiamo l’interazione tra superradianza e rumore termico sia per nanotubi molecolari (di dimensioni minori della lunghezza d’onda associata alla transizione) che sono presenti nei complessi antenna fotosintetici dei Green Sulfur Bacteria, sia pure per superreticoli di quantum dots di nuova generazione, aventi dimensioni maggiori della lunghezza d’onda emessa. In entrambi i casi si dimostra che la coerenza può permanere in presenza di rumore termico alle temperature a cui questi sistemi sono stati analizzati sperimentalmente (temperatura ambiente per i nanotubi molecolari, e 6 K per i superreticoli di quantum dots). Nello specifico, nei nanotubi molecolari mostriamo che la macroscopica delocalizzazione coerente delle eccitazioni a temperatura ambiente, che copre centinaia di molecole, può essere considerata un effetto emergente che origina dall’effetto combinato della specifica disposizione geometrica delle molecole e della presenza di accoppiamenti tra subunità del cilindro, incrementati dagli effetti cooperativi. Questi risultati aprono la strada a nuovi modi per ingegnerizzare dei “quantum wires” robusti al rumore grazie alla cooperatività. Inoltre, la presente analisi di sistemi allo stato solido basati su superreticoli di “quantum dots” di perovskite (CsPbBr3) fornisce una base teorica in grado di comprendere recenti osservazioni di emissione superradiante. Sulla base della nostra teoria, suggeriamo che futuri esperimenti dove si utilizzino quantum dots più piccoli, potrebbe aumentare significativamente la robustezza del sistema al rumore termico, aprendo la strada verso la superradianza a temperatura ambiente in sistemi allo stato solido. Si considerano anche i complessi antenna dei Purple Bacteria, dove è ben risaputo che gli effetti cooperativi incrementano il trasferimento e l’accumulo di eccitazioni generate dalla luce assorbita. Mostriamo come queste proprietà possono essere sfruttate per creare un laser ispirato a sistemi biologici e basato su aggregati molecolari, dove la luce solare, benché debole, sarebbe utilizzata come sorgente di pompaggio. Il trasferimento efficiente di energia dentro questo sistema, all’atto pratico, focalizzerebbe l’eccitazione assorbita in direzione di un dimero molecolare, composto da una coppia di molecole interagenti, opportunamente scelte. L’orientazione dei momenti di dipolo di transizione in ciascun dimero è tale da concentrare tutta l’intensità del dipolo nel livello a più alta energia, lasciando lo stato eccitonico inferiore otticamente inattivo. Un dimero molecolare in tale configurazione, che è ideale per ottenere inversione di popolazione, è chiamato “H-dimer”. Tale H-dimer, nell’archittettura qui proposta per un laser ispirato a sistemi biologici, è posto al centro di un aggregato molecolare ispirato a sistemi biologici. Gli H-dimers, eccitati dagli aggregati molecolari circostanti, raggiungono inversione di popolazione e, dunque, possono emettere luce laser quando tali aggregati sono posti in una cavità ottica. Convertire l’energia incoerente fornita dal Sole in un fascio laser coerente supererebbe diverse limitazioni pratiche inerenti all’utilzzo della luce solare come sorgente di energia pulita. Per esempio, i fasci laser sono molto efficienti nell’avviare reazioni chimiche che convertono la luce solare in energia chimica. Inoltre, dal momento che i complessi fotosintetici batterici tendono ad operare nella regione spettrale del vicino infrarosso, la nostra proposta si presta in modo naturale a realizzare laser a infrarossi a corta lunghezza d’onda, i cui fasci viaggerebbero per lunghe distanze senza quasi perdere energia, quindi distribuendo in modo efficiente l’energia solare raccolta. Nella ricerca di un meccanismo comune alla cooperatività e alla sua robustezza, abbiamo confrontato il modello delle coppie di Cooper della superconduttività con la superradianza in singola eccitazione, mostrando molte somiglianze tra i due fenomeni: in particolare, i sistemi superradianti presentano una “gap” immaginaria nel piano complesso (ovvero, una segregazione tra i tempi di vita degli autostati del sistema) che, in modo simile alla gap superconduttiva, rende questi sistemi robusti al rumore statico. Più in generale, mostriamo che ogni interazione a lungo raggio tra i costituenti di un sistema induce effetti collettivi, manifestati da delle gap nello spettro eccitonico. Perciò, la nostra analisi successiva considera l’effetto delle interazioni a lungo raggio sul trasporto eccitonico lungo catene disordinate. Dimostriamo che la presenza di uno stato collettivo ben separato dagli altri stati influenza tutto lo spettro del sistema, generando dei regimi molto controintuitivi dove il trasporto è incrementato dal disordine o è indipendente da esso, e tali regimi si estendono su molti ordini di grandezza nell’intensità del disordine. Dimostriamo anche che una catena fortemente accoppiata a un modo del campo elettromagnetico in una cavità ottica è equivalente a una catena con interazione a lungo raggio, mostrandosi dunque molto promettente per esperimenti e applicazioni future. Nello specifico, mostriamo che catene molecolari realistiche, ioni intrappolati realizzati allo stato dell’arte e atomi di Rydberg sono tutti in grado di raggiungere l’intensità di interazione a lungo raggio tale per cui il trasporto sarebbe incrementato dal disordine o indipendente da esso, puntando alla realizzazione di un trasporto di energia senza dissipazione in “quantum wires” disordinati. / This Ph.D. thesis studies the interplay of cooperativity and noise in realistic systems, largely focusing on superradiance. Cooperative effects emerge from the collective interaction of an ensemble of elements to an external field. Notable examples are superconductivity, where the electron Cooper pairs interact with the lattice vibrations, plasmon excitations, arising from the collective interaction of electrons in a metal with the Coulomb field, and superradiance, that is a cooperative spontaneous emission process stemming from an aggregate of identical emitters. Cooperative effects are typically robust to disorder and noise, making them interesting for applications to quantum devices operating at room temperature. In this work, we first present a general master equation formalism that describes the collective coupling of an aggregate of emitters/absorbers to the electromagnetic field, valid both when the size of the aggregate is larger or smaller than the emitted/absorbed wavelength. Also, the formalism is valid both for weak and strong coupling of the emitters to the electromagnetic field and, most importantly, it allows to correctly describe superradiance in different regimes. Within such formalism, the interplay of superradiance and thermal noise is studied both for molecular nanotubes (of size smaller than the transition wavelength) that are present in the antenna complexes of photosynthetic Green Sulfur Bacteria, and also for novel solid state quantum dot superlattices, having size larger than the emitted wavelength. In both cases it is shown that coherence can persist in presence of thermal noise at the temperatures where these systems have been experimentally analyzed (room temperature for molecular nanotubes, and 6 K for quantum dot superlattices). Specifically, in natural molecular nanotubes we show that the macroscopic coherent delocalization of the excitation at room temperature, covering hundreds of molecules, can be considered an emergent effect originating from the combined effect of the specific geometric disposition of the molecules and the presence of cooperatively enhanced couplings between cylinder subunits. These results open the path to new ways of engineering quantum wires robust to noise thanks to cooperativity. Moreover, our analysis of solid state systems based on perovskite (CsPbBr3) quantum dot superlattices provides a theoretical framework able to explain recent observations of superradiant emission. Based on our theory, we suggest that further experiments, using smaller quantum dots, could significantly increase the robustness of the system to thermal noise, paving the way towards room-temperature superradiance in solid-state systems. We also considered the antenna complexes of Purple Bacteria, where cooperative effects are well known to boost the transfer and storage of photo-absorbed excitations. We show how these properties can be exploited to create a bio-inspired molecular aggregate laser medium, where natural sunlight, although weak, would be used as a pumping source. The efficient energy transfer within this system would effectively focus the absorbed excitation on a suitably chosen molecular dimer, composed by a pair of interacting molecules. The orientation of the molecule transition dipole moment in each dimer is such to concentrate all the dipole strength in the highest energy level, leaving the lower excitonic state dark. A molecular dimer in such configuration, which is ideal to achieve population inversion, is called H-dimer. Such an H-dimer in our proposed architecture for a bio-inspired laser medium, is placed at the center of the bio-inspired molecular aggregates. The H-dimers, pumped by the surrounding molecular aggregates, reach population inversion and, therefore, can lase when such aggregates are placed in an optical cavity. Turning the incoherent energy supply provided by the Sun into a coherent laser beam would overcome several of the practical limitations inherent in using sunlight as a source of clean energy. For example, laser beams are highly effective at driving chemical reactions which convert sunlight into chemical energy. Further, since bacterial photosynthetic complexes tend to operate in the near-infrared spectral region, our proposal naturally lends itself for realising short-wavelength infrared lasers which would allow their beams to travel nearly losslessly over large distances, thus efficiently distributing the collected sunlight energy. In search of a common mechanism to cooperativity and its robustness, we have compared the Cooper pair model of superconductivity and single-excitation superradiance, showing many similarities between the two: in particular, superradiant systems present an imaginary gap in the complex plane (that is, a segregation between the lifetimes of the system eigenstates) that, similarly to the superconducting gap, makes these systems robust to static disorder. More in general, we show that any long-range interaction between the constituents of a system generates collective behaviours, manifested by gaps in the excitonic spectrum. Therefore, our further analysis considers the effect of long-range interactions on excitation transport along disordered chains. We show that the presence of a gapped, collective state affects the whole spectrum of the system, generating quite counter-intuitive disorder-enhanced and disorder-independent transport regimes, that extend over many orders of magnitude of the disorder strength. We also prove that a chain strongly coupled to a cavity mode is equivalent to a long-range interacting chain, thus being very promising for future experiments and applications. Specifically, we show that realistic molecular chains, state-of-the-art trapped ions and Rydberg atoms are all able to reach the needed long-range interaction strength that would show disorder-enhanced or disorder-independent transport, aiming to the realization of dissipationless transport of energy in disordered quantum wires.

No description available.

Hexapod, ROS, Gazebo, Simulation, C++, Python, Node, Service, Publisher, Subscriber, Topic, URDF, SDF, AX-12+, USB2Dynamixel, CM-530, King Spider, Robotis, Navigation

This thesis addresses orchestration of servers amongst multiple co-hosted internet services such as e-Banking, e-Auction and e-Retail in hosting centres. The hosting paradigm entails levying fees for hosting third party internet services on servers at guaranteed levels of service performance. The orchestration of server ensemble in hosting centres is considered in the context of maximising the hosting centre's revenue over a lengthy time horizon. The inspiration for the server orchestration approach proposed in this thesis is drawn from nature and generally classed as swarm intelligence, specifically, sophisticated collective behaviour of social insects borne out of primitive interactions amongst members of the group to solve problems beyond the capability of individual members. Consequently, the approach is self-organising, adaptive and robust. A new scheme for server ensemble orchestration is introduced in this thesis. This scheme exploits the many similarities between server orchestration in an internet hosting centre and forager allocation in a honeybee (Apis mellifera) colony. The scheme mimics the way a honeybee colony distributes foragers amongst flower patches to maximise nectar influx, to orchestrate servers amongst hosted internet services to maximise revenue. The scheme is extended by further exploiting inherent feedback loops within the colony to introduce self-tuning and energy-aware server ensemble orchestration. In order to evaluate the new server ensemble orchestration scheme, a collection of server ensemble orchestration methods is developed, including a classical technique that relies on past history to make time varying orchestration decisions and two theoretical techniques that omnisciently make optimal time varying orchestration decisions or an optimal static orchestration decision based on complete knowledge of the future. The efficacy of the new biomimetic scheme is assessed in terms of adaptiveness and versatility. The performance study uses representative classes of internet traffic stream behaviour, service user's behaviour, demand intensity, multiple services co-hosting as well as differentiated hosting fee schedule. The biomimetic orchestration scheme is compared with the classical and the theoretical optimal orchestration techniques in terms of revenue stream. This study reveals that the new server ensemble orchestration approach is adaptive in a widely varying external internet environments. The study also highlights the versatility of the biomimetic approach over the classical technique. The self-tuning scheme improves on the original performance. The energy-aware scheme is able to conserve significant energy with minimal revenue performance degradation. The simulation results also indicate that the new scheme is competitive or better than classical and static methods.

Nous nous intéressons à la conception des mains mécaniques anthropomorphes destinées à manipuler des objets dans un environnement humain. Via l'analyse du mouvement de sujets humains lors d'une tâche de manipulation de référence, nous proposons une méthode pour évaluer la capacité des mains robotiques à manipuler les objets. Nous montrons comment les rapports de couplage angulaires entre les articulations et les limites articulaires, influent sur l'aptitude à manipuler dynamiquement des objets. Nous montrons également l'impact du poignet sur les tâches de manipulation rapides. Nous proposons une stratégie pour calculer les forces de manipulation en bout de doigts et dimensionner les moteurs d'un tel préhenseur. La méthode proposée est dépendante de la tâche visée et s'adapte à tout type de mouvement dès lors qu'il peut être capturé et analysé. Dans une deuxième partie, consacrée aux robots manipulateurs, nous élaborons des algorithmes de commande optimale. En considérant l'énergie cinétique du robot comme une métrique, le modèle dynamique est formulé sous forme tensorielle dans le cadre de la géométrie Riemannienne. La discrétisation temporelle est basée sur les Éléments Finis d'Hermite. Nous intégrons les équations de Lagrange du mouvement par une méthode de perturbation. Des exemples de simulation illustrent la superconvergence de la technique d'Hermite. Le critère de contrôle est choisi indépendant des paramètres de configuration. Les équations de la commande associées aux équations du mouvement se révèlent covariantes. La méthode de commande optimale proposée consiste à minimiser la fonction objective correspondant au critère invariant sélectionné. / We focus on the design of anthropomorphous mechanical hands destined to manipulate objects in a human environment. Via the motion analysis of a reference manipulation task performed by human subjects, we propose a method to evaluate a robotic hand manipulation capacities. We demonstrate how the angular coupling between the fingers joints and the angular limits affect the hands potential to manipulate objects. We also show the influence of the wrist motions on the manipulation task. We propose a strategy to calculate the fingertip manipulation forces and dimension the fingers motors. In a second part devoted to articulated robots, we elaborate optimal control algorithms. Regarding the kinetic energy of the robot as a metric, the dynamic model is formulated tensorially in the framework of Riemannian geometry. The time discretization is based on the Hermite Finite Elements.A time integration algorithm is designed by implementing a perturbation method of the Lagrange's motion equations. Simulation examples illustrate the superconvergence of the Hermite's technique. The control criterion is selected to be coordinate free. The control equations associated with the motion equations reveal to be covariant. The suggested control method consists in minimizing the objective function corresponding to the selected invariant criterion.

Made available in DSpace on 2014-12-17T15:46:59Z (GMT). No. of bitstreams: 1 LauraEASS_TESE.pdf: 2447411 bytes, checksum: 3e442431965058383423623bc7751de0 (MD5) Previous issue date: 2012-02-02 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / Traditional applications of feature selection in areas such as data mining, machine learning and pattern recognition aim to improve the accuracy and to reduce the computational cost of the model. It is done through the removal of redundant, irrelevant or noisy data, finding a representative subset of data that reduces its dimensionality without loss of performance. With the development of research in ensemble of classifiers and the verification that this type of model has better performance than the individual models, if the base classifiers are diverse, comes a new field of application to the research of feature selection. In this new field, it is desired to find diverse subsets of features for the construction of base classifiers for the ensemble systems. This work proposes an approach that maximizes the diversity of the ensembles by selecting subsets of features using a model independent of the learning algorithm and with low computational cost. This is done using bio-inspired metaheuristics with evaluation filter-based criteria / A aplica??o tradicional da sele??o de atributos em diversas ?reas como minera??o de dados, aprendizado de m?quina e reconhecimento de padr?es visa melhorar a acur?cia dos modelos constru?dos com a base de dados, ao retirar dados ruidosos, redundantes ou irrelevantes, e diminuir o custo computacional do modelo, ao encontrar um subconjunto representativo dos dados que diminua sua dimensionalidade sem perda de desempenho. Com o desenvolvimento das pesquisas com comit?s de classificadores e a verifica??o de que esse tipo de modelo possui melhor desempenho que os modelos individuais, dado que os classificadores base sejam diversos, surge uma nova aplica??o ?s pesquisas com sele??o de atributos, que ? a de encontrar subconjuntos diversos de atributos para a constru??o dos classificadores base de comit?s de classificadores. O presente trabalho prop?e uma abordagem que maximiza a diversidade de comit?s de classificadores atrav?s da sele??o de subconjuntos de atributos utilizando um modelo independente do algoritmo de aprendizagem e de baixo custo computacional. Isso ? feito utilizando metaheur?sticas bioinspiradas com crit?rios de avalia??o baseados em filtro

Dans cette thèse, nous nous intéressons au problème de l’atterrissage lunaire autonome et nous proposons une méthode innovante amenant une alternative à l’utilisation de capteurs classiques qui peuvent se révéler encombrants, énergivores et très onéreux.La première partie est consacrée au développement et à la construction de capteurs de mouvement inspirés de la vision des insectes volants et mesurant le flux optique.Le flux optique correspond à la vitesse angulaire relative de l’environnement mesurée par la rétine d’un agent. Dans un environnement fixe, les mouvements d’un robot génèrent un flux optique contenant des informations essentielles sur le mouvement de ce dernier. En utilisant le principe du « temps de passage », nous présentons les résultats expérimentaux obtenus en extérieur avec deux versions de ces capteurs.Premièrement, un capteur mesurant le flux optique dans les deux directions opposées est développé et testé en laboratoire. Deuxièmement un capteur adapté à la mesure des faibles flux optiques similaires à ceux pouvant être mesurés lors d’un alunissage est développé, caractérisé et enfin testé sur un drone hélicoptère en conditions extérieures.Dans la seconde partie, une méthode permettant de réaliser le guidage, la navigation et la commande (GNC pour Guidance Navigation and Control) du système est proposée. L’innovation réside dans le fait que l’atterrissage en douceur est uniquement assuré par les capteurs de flux optique. L’utilisation des capteurs inertiels est réduite au maximum. Plusieurs capteurs orientés dans différentes directions de visée, et fixés à la structure de l’atterrisseur permettent d’atteindre les conditions finales définies par les partenaires industriels. Les nombreuses informations décrivant la position et l’attitude du système contenues dans le flux optique sont exploitées grâce aux algorithmes de navigation qui permettent d’estimer les flux optiques ventraux et d’expansion ainsi que le tangage.Nous avons également montré qu’il est possible de contrôler l’atterrisseur planétaire en faisant suivre aux flux optiques estimés une consigne optimale au sens de la consommation d’énergie. Les simulations réalisées durant la thèse ont permis de valider le fonctionnement et le potentiel de la solution GNC proposée en intégrant le code du capteur ainsi que des images simulées du sol de la lune. / In this PhD thesis, the challenge of autonomous lunar landing was addressed and an innovative method was developed, which provides an alternative to the classical sensor suites based on RADAR, LIDAR and cameras, which tend to be bulky, energy consuming and expensive. The first part is devoted to the development of a sensor inspired by the fly’s visual sensitivity to optic flow (OF). The OF is an index giving the relative angular velocity of the environment sensed by the retina of a moving insect or robot. In a fixed environment (where there is no external motion), the self-motion of an airborne vehicle generates an OF containing information about its own velocity and attitude and the distance to obstacles. Based on the “Time of Travel” principle we present the results obtained for two versions of 5 LMSs based optic flow sensors. The first one is able to measure accurately the OF in two opposite directions. It was tested in the laboratory and gave satisfying results. The second optic flow sensor operates at low velocities such as those liable to occur during lunar landing was developed. After developing these sensors, their performances were characterized both indoors and outdoors, and lastly, they were tested onboard an 80-kg helicopter flying in an outdoor environment. The Guidance Navigation and Control (GNC) system was designed in the second part on the basis of several algorithms, using various tools such as optimal control, nonlinear control design and observation theory. This is a particularly innovative approach, since it makes it possible to perform soft landing on the basis of OF measurements and as less as possible on inertial sensors. The final constraints imposed by our industrial partners were met by mounting several non-gimbaled sensors oriented in different gaze directions on the lander’s structure. Information about the lander’s self-motion present in the OF measurements is extracted by navigation algorithms, which yield estimates of the ventral OF, expansion OF and pitch angle. It was also established that it is possible to bring the planetary lander gently to the ground by tracking a pre-computed optimal reference trajectory in terms of the lowest possible fuel consumption. Software-in-the-loop simulations were carried out in order to assess the potential of the proposed GNC approach by testing its performances. In these simulations, the sensor firmware was taken into account and virtual images of the lunar surface were used in order to improve the realism of the simulated landings.