Global ETD Search

31	Robust nonlinear control : from continuous time to sampled-data with aerospace applications. / Commande non linéaire robuste : du temps-continu jusqu’aux systèmes sous échantillonnage avec applications aérospatiales. Mattei, Giovanni 13 February 2015 (has links) La thèse porte sur le développement des techniques non linéaires robustes de stabilisation et commande des systèmes avec perturbations de model. D’abord, on introduit les concepts de base de stabilité et stabilisabilité robuste dans le contexte des systèmes non linéaires. Ensuite, on présente une méthodologie de stabilisation par retour d’état en présence d’incertitudes qui ne sont pas dans l’image de la commande («unmatched»). L’approche récursive du «backstepping» permet de compenser les perturbations «unmatched» et de construire une fonction de Lyapunov contrôlée robuste, utilisable pour le calcul ultérieur d’un compensateur des incertitudes dans l’image de la commande («matched»). Le contrôleur obtenu est appelé «recursive Lyapunov redesign». Ensuite, on introduit la technique de stabilisation par «Immersion & Invariance» comme outil pour rendre un donné contrôleur non linéaire, robuste par rapport à dynamiques non modelées. La première technique de contrôle non linéaire robuste proposée est appliquée au projet d’un autopilote pour un missile air-air et au développement d’une loi de commande d’attitude pour un satellite avec appendices flexibles. L’efficacité du «recursive Lyapunov redesign» est mis en évidence dans le deux cas d’étude considérés. En parallèle, on propose une méthode systématique de calcul des termes incertains basée sur un modèle déterministe d’incertitude. La partie finale du travail de thèse est relative à la stabilisation des systèmes sous échantillonnage. En particulier, on reformule, dans le contexte digital, la technique d’Immersion et Invariance. En premier lieu, on propose des solutions constructives en temps continu dans le cas d’une classe spéciale des systèmes en forme triangulaire «feedback form», au moyen de «backstepping» et d’arguments de domination non linéaire. L’implantation numérique est basée sur une loi multi-échelles, dont l’existence est garantie pour la classe des systèmes considérée. Le contrôleur digital assure la propriété d’attractivité et des trajectoires bornées. La loi de commande, calculée par approximation finie d’un développement asymptotique, est validée en simulation de deux exemples académiques et deux systèmes physiques, le pendule inversé sur un chariot et le satellite rigide. / The dissertation deals with the problems of stabilization and control of nonlinear systems with deterministic model uncertainties. First, in the context of uncertain systems analysis, we introduce and explain the basic concepts of robust stability and stabilizability. Then, we propose a method of stabilization via state-feedback in presence of unmatched uncertainties in the dynamics. The recursive backstepping approach allows to compensate the uncertain terms acting outside the control span and to construct a robust control Lyapunov function, which is exploited in the subsequent design of a compensator for the matched uncertainties. The obtained controller is called recursive Lyapunov redesign. Next, we introduce the stabilization technique through Immersion \& Invariance (I\&I) as a tool to improve the robustness of a given nonlinear controller with respect to unmodeled dynamics. The recursive Lyapunov redesign is then applied to the attitude stabilization of a spacecraft with flexible appendages and to the autopilot design of an asymmetric air-to-air missile. Contextually, we develop a systematic method to rapidly evaluate the aerodynamic perturbation terms exploiting the deterministic model of the uncertainty. The effectiveness of the proposed controller is highlighted through several simulations in the second case-study considered. In the final part of the work, the technique of I\& I is reformulated in the digital setting in the case of a special class of systems in feedback form, for which constructive continuous-time solutions exist, by means of backstepping and nonlinear domination arguments. The sampled-data implementation is based on a multi-rate control solution, whose existence is guaranteed for the class of systems considered. The digital controller guarantees, under sampling, the properties of manifold attractivity and trajectory boundedness. The control law, computed by finite approximation of a series expansion, is finally validated through numerical simulations in two academic examples and in two case-studies, namely the cart-pendulum system and the rigid spacecraft. Commande non linéaire Commande robuste Fonction de Lyapunov contrôlée robuste Modélisation de l'incertitude Backstepping robuste Commande multi-échelles Projet d'autopilote pour missile Stabilisation d'attitude Satellite flexible Nonlinear control Robust control Robust control Lyapunov function Uncertainty modeling Robust Backstepping Nonlinear sampled data control Multi-rate control Missile autopilot design Attitude stabilization Flexible spacecraft Recursive Lyapunov redesign Lypunov redesign Immersion and invariance
32	Abordagem multidimensional para avaliação da acessibilidade de interfaces vocais considerando a modelagem da incerteza. / Multidimensional approach to assess the accessibility of voice interfaces considering uncertainty modeling. CARNEIRO, Maria Isabel Farias. 31 July 2018 (has links) Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-07-31T19:39:43Z No. of bitstreams: 1 MARIA ISABEL FARIA CARNEIRO - DISSERTAÇÃO PPGCC 2014..pdf: 45568096 bytes, checksum: 7fe570750f4904224de8b7e2f76035e2 (MD5) / Made available in DSpace on 2018-07-31T19:39:43Z (GMT). No. of bitstreams: 1 MARIA ISABEL FARIA CARNEIRO - DISSERTAÇÃO PPGCC 2014..pdf: 45568096 bytes, checksum: 7fe570750f4904224de8b7e2f76035e2 (MD5) Previous issue date: 2014-03 / 0 desenvolvimento de interfaces vocais [VUI - Voice User Interface) per se não é uma garantia para um processo interativo de qualidade entre usuários com deficiência visual e sistemas computacionais. Com o intuito de avaliar os problemas de acessibilidade em VUI, a presente pesquisa focalizou a proposição de uma abordagem de avaliação baseada em um conjunto de técnicas já conhecidas pela comunidade de IHC (Interação Homem-Máquina). No tocante a cada técnica utilizada, o problema foi focado a partir de diferentes perspectivas: (i) do usuário, expresso a partir das visões dos usuários sobre o produto, reunidas a partir de uma abordagem de avaliação; (ii) do especialista, expresso sob a forma de análise dos resultados dos desempenhos dos usuários em sessões de teste de acessibilidade; e (iii) da comunidade de acessibilidade, expresso com base em revisões de projeto, a fim de determinar se o projeto da interface está em conformidade com um padrão. Além disso, visando a evidenciar a incerteza associada aos julgamentos do avaliador na inspeção de conformidade do produto, incorporou-se a modelagem de incerteza, a partir da utilização de Redes Bayesianas, possibilitando ao avaliador explicitar os níveis de incerteza associados às inspeções de conformidade do produto a um padrão, por ele realizadas. A abordagem metodológica foi validada a partir de um estudo de caso envolvendo a avaliação da acessibilidade do sistema computacional DOSVOX, desenvolvido na Universidade Federal do Rio de Janeiro (UFRJ), com o objetivo de auxiliar usuários com deficiência visual no uso de sistemas computacionais. No enfoque da inspeção de conformidade, consideraram-se as partes 14 (Diálogos via menus), 17 (Diálogos via preenchimento via formulários) e 171 (Guia de acessibilidade de software) do padrão internacional ISO 9241. Por outro lado, nos enfoques da mensuração de desempenho e da sondagem da satisfação subjetiva do usuário, foram realizados testes de acessibilidade, envolvendo um universo amostrai de 100 usuários. Inicialmente, os participantes foram agrupados como cegos (40 usuários), baixa visão (20 usuários) e sem deficiência visual (40 usuários), de acordo com tipo de deficiência visual. Em seguida, eles foram classificados como principiantes (46 usuários) ou intermediários (54 usuários), de acordo com o nível de conhecimento em Informática e de experiência o produto avaliado. Os dados resultantes dos testes de acessibilidade foram processados estatisticamente, a fim de verificar a correlação entre os desempenhos dos grupos de usuários e entre o desempenho das categorias de usuários de cada grupo. O processamento estatístico dos dados evidenciou a inexistência de diferenças significativas entre os desempenhos dos grupos, bem como entre as categorias de usuários. Por outro lado, a confrontação dos resultados dos três enfoques (mensuração de desempenho do usuário, mensuração da satisfação subjetiva do usuário e inspeção de conformidade do produto a padrões) demonstrou que a abordagem de avaliação proposta produziu resultados complementares e reforçou a relevância da utilização de uma abordagem multimétodos para a avaliação de acessibilidade de interfaces vocais. / Voice interaction design per se does not provide quality assurance of the interactive process for visually impaired users. In this dissertation, a method for evaluating voice user interface (VUI) accessibility based upon a set of techniques already well-known to the HCI (Human-Computer Interaction) community is proposed. For each technique, the problem is focused from a different perspective: (i) the user's perspective, which is expressed as views on the product gathered from an inquiry-based approach; (ii) the specialist's perspective, which is expressed by the analysis of the performance results in accessibility testing sessions; and (iii) the accessibility community's perspective, which is expressed by design reviews to determine whether a user interface design conforms to standards. Additionally, Bayesian networks were used in order to make explicit the uncertainty inherent in conformity inspection processes. A case study with DOSVOX system was performed to validate the proposed approach. DOSVOX system was developed at Federal University of Rio de Janeiro (UFRJ) with the aim of helping visually impaired users use the computer. A conformity inspection was performed in accordance with parts 14 (Menu dialogues), 17 (Form-filling dialogues) 171 (Guidance on software accessibility) of ISO 9241. On the other hand, the user performance measurement and the user subjective satisfaction measurement were conducted via accessibility testing. One hundred subjects were enrolled in this study. First, they were categorized as blind (40 users), low vision (20 users) and non-visually impaired (40 users), according to their visual impairment. Second, they were grouped as novices (46 users) and intermediates (54 users), according to their knowledge level in Informatics and experience with the evaluated product. Accessibility test results were statistically analyzed in order to verify the correlation between category performances and between group performances. No statistically significant differences between the user categories or the user groups were found. On the other hand, data comparison showed that the three strategies adopted (user performance measurement, user satisfaction measurement and standard conformity inspection) add to the evaluation process, producing complimentary data that are significant to the process, and reinforcing the relevance of a multi-layered approach for the accessibility evaluation of voice user interfaces. Ciência da Computação. Interfaces vocais - avaliação Acessibilidade de interfaces vocais Modelagem da incerteza Abordagem multimétodos Avaliação de acessibilidade Interface vocal com usuário Voice user interface Interação homem-máquina Redes Bayesianas DOSVOX - Sistema computacional Acessibilidade de software Estudo com cegos Multi-layered approach Uncertainty modeling Accessibility evaluation
33	Highway Development Decision-Making Under Uncertainty: Analysis, Critique and Advancement El-Khatib, Mayar January 2010 (has links) While decision-making under uncertainty is a major universal problem, its implications in the field of transportation systems are especially enormous; where the benefits of right decisions are tremendous, the consequences of wrong ones are potentially disastrous. In the realm of highway systems, decisions related to the highway configuration (number of lanes, right of way, etc.) need to incorporate both the traffic demand and land price uncertainties. In the literature, these uncertainties have generally been modeled using the Geometric Brownian Motion (GBM) process, which has been used extensively in modeling many other real life phenomena. But few scholars, including those who used the GBM in highway configuration decisions, have offered any rigorous justification for the use of this model. This thesis attempts to offer a detailed analysis of various aspects of transportation systems in relation to decision-making. It reveals some general insights as well as a new concept that extends the notion of opportunity cost to situations where wrong decisions could be made. Claiming deficiency of the GBM model, it also introduces a new formulation that utilizes a large and flexible parametric family of jump models (i.e., Lévy processes). To validate this claim, data related to traffic demand and land prices were collected and analyzed to reveal that their distributions, heavy-tailed and asymmetric, do not match well with the GBM model. As a remedy, this research used the Merton, Kou, and negative inverse Gaussian Lévy processes as possible alternatives. Though the results show indifference in relation to final decisions among the models, mathematically, they improve the precision of uncertainty models and the decision-making process. This furthers the quest for optimality in highway projects and beyond. highway development decision making under uncertainty real options jump processes infinitely divisible distributions Lévy processes measure theory characteristic function characteristic exponent Lévy jump measure probability measure cádlág stochastic process Wiener process Poisson process compound Poisson process finite activity models jump diffusion models Merton model Gaussian jump process Kou model double exponential jump process leptokurtic volatility smile infinite activity models pure jumps process generalized hyperbolic model modified Bessel function negative inverse Gaussian model geometric Brownian motion model log-normal distribution model normality assumption heavy-tailed distribution asymmetric distribution quantile-quantile plot Rydberg algorithm parameter calibration moments cummulants sum of squares Monte Carlo simulation least-squares regression backward dynamic programming discrete-time Markov chain land price traffic demand highway service quality index data collection traffic volume Annual Average Daily Traffic Ontario Ministry of Transportation Land Registry Office Freedom of Information Act seasonality value of transportation types of transportation systems importance of highway systems cost of wrong decisions monetary cost private sector cost human cost land expropriation environmental cost irreversibility cost factor time cost factor political cost factor opportunity cost opportunity cost of wrong decisions economic cost of wrong decisions economic cost of mis-estimation economic profit of wrong decisions cost of inaction price of making right decisions scope of decisions rehabilitation decision land acquisition decision expansion decision uncertainty modeling land acquisition cost expropriation cost construction cost material cost Montréal-Mirabel International Airport Pickering Airport 407 Express Toll Route Highway 407 Statistics
34	Highway Development Decision-Making Under Uncertainty: Analysis, Critique and Advancement El-Khatib, Mayar January 2010 (has links) While decision-making under uncertainty is a major universal problem, its implications in the field of transportation systems are especially enormous; where the benefits of right decisions are tremendous, the consequences of wrong ones are potentially disastrous. In the realm of highway systems, decisions related to the highway configuration (number of lanes, right of way, etc.) need to incorporate both the traffic demand and land price uncertainties. In the literature, these uncertainties have generally been modeled using the Geometric Brownian Motion (GBM) process, which has been used extensively in modeling many other real life phenomena. But few scholars, including those who used the GBM in highway configuration decisions, have offered any rigorous justification for the use of this model. This thesis attempts to offer a detailed analysis of various aspects of transportation systems in relation to decision-making. It reveals some general insights as well as a new concept that extends the notion of opportunity cost to situations where wrong decisions could be made. Claiming deficiency of the GBM model, it also introduces a new formulation that utilizes a large and flexible parametric family of jump models (i.e., Lévy processes). To validate this claim, data related to traffic demand and land prices were collected and analyzed to reveal that their distributions, heavy-tailed and asymmetric, do not match well with the GBM model. As a remedy, this research used the Merton, Kou, and negative inverse Gaussian Lévy processes as possible alternatives. Though the results show indifference in relation to final decisions among the models, mathematically, they improve the precision of uncertainty models and the decision-making process. This furthers the quest for optimality in highway projects and beyond. highway development decision making under uncertainty real options jump processes infinitely divisible distributions Lévy processes measure theory characteristic function characteristic exponent Lévy jump measure probability measure cádlág stochastic process Wiener process Poisson process compound Poisson process finite activity models jump diffusion models Merton model Gaussian jump process Kou model double exponential jump process leptokurtic volatility smile infinite activity models pure jumps process generalized hyperbolic model modified Bessel function negative inverse Gaussian model geometric Brownian motion model log-normal distribution model normality assumption heavy-tailed distribution asymmetric distribution quantile-quantile plot Rydberg algorithm parameter calibration moments cummulants sum of squares Monte Carlo simulation least-squares regression backward dynamic programming discrete-time Markov chain land price traffic demand highway service quality index data collection traffic volume Annual Average Daily Traffic Ontario Ministry of Transportation Land Registry Office Freedom of Information Act seasonality value of transportation types of transportation systems importance of highway systems cost of wrong decisions monetary cost private sector cost human cost land expropriation environmental cost irreversibility cost factor time cost factor political cost factor opportunity cost opportunity cost of wrong decisions economic cost of wrong decisions economic cost of mis-estimation economic profit of wrong decisions cost of inaction price of making right decisions scope of decisions rehabilitation decision land acquisition decision expansion decision uncertainty modeling land acquisition cost expropriation cost construction cost material cost Montréal-Mirabel International Airport Pickering Airport 407 Express Toll Route Highway 407 Statistics

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