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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
321

[en] A MULTI-AGENT SYSTEM FOR REAL TIME MONITORING AND DATA ACQUISITION / [pt] UM SISTEMA MULTI-AGENTES PARA MONITORAMENTO E AQUISIÇÃO EM TEMPO REAL

FREDERICO SILVA GUIMARAES 24 August 2006 (has links)
[pt] Sistemas supervisores envolvendo software embarcados são encontrados com freqüência e são responsáveis pela supervisão de equipamentos que vão desde máquinas industriais e eletrodomésticos, a celulares e PDAs. Muitos possuem severos requisitos de confiabilidade e tolerância a falhas, bem como características de sistemas de tempo real. Esta pesquisa investiga o uso de tecnologias de ponta como Design by Contract, Agentes de Software, Mock Objects e Componentes de Software no auxílio ao desenvolvimento de sistemas de monitoramento e aquisição em tempo real. Explora-se, ainda, o conceito de sistemas orientados à recuperação. Para realizar tal análise é utilizado como estudo de caso um sistema de inspeção de dutos, que foi implementado utilizando tais tecnologias. De maneira resumida, pode-se dizer que neste estudo de caso percebeu-se que o uso dessas tecnologias fez com que o sistema fosse desenvolvido em um curto espaço de tempo, sendo que questões relevantes não foram prejudicadas, como por exemplo o fato do sistema ser robusto e tolerante a falhas. É importante ressaltar que o sistema apresentado se encontra em uso em inspeções de dutos reais. / [en] Supervisory systems allied to embedded software, a common subject in the literature, are responsible by the supervision of equipments like industrial machines, household-electric devices, cellular phones and PDAs. Many of them have severe requisites of fault tolerance and reliability as well as real time systems features. This research investigates the use of state-of-the-art technologies such as Design By Contract, Mock Objects, software agents and components in the development of real-time monitoring and data-acquisition systems. Recovery oriented systems concepts are also explored. The case study carried out to the research is a pipeline inspection software system, which uses such technologies. In a nutshell, it can be said that this case study showed strong evidence that the use of these technologies allowed the development in a very short time, without any loss of robustness, fault tolerance and reliability. The developed system is currently being used in real pipeline inspections.
322

Proposta de modelo de veículos aéreos não tripulados (VANTs) cooperativos aplicados a operações de busca. / Proposal of cooperative unmanned aerial vehicles (UAVs) model applied to search operations.

Chaves, Áquila Neves 18 December 2012 (has links)
Os Veículos Aéreos Não Tripulados (VANTs) são ideais para operações de risco e estressante para o ser humano são as chamadas dull, dirty and dangerous missions. Portanto, uma importante aplicação desse tipo de robô aéreo diz respeito a operações de busca envolvendo múltiplos VANTs cooperativos, em que há risco de colisões entre aeronaves e o tempo de um voo é limitado, entre outros fatores, pela capacidade de um piloto trabalhar sem descanso. Entretanto, apesar de atualmente verificar-se um crescente número de pesquisas envolvendo VANTs e do grande potencial existente na utilização de VANTs, operações de busca cooperativas ainda não estão ocorrendo. Esse assunto é uma área de estudo multidisciplinar e nascente, que possui diversas linhas de pesquisa. Diferentes algoritmos de navegação e padrões de busca foram estudados visando selecionar o(s) mais adequado(s). Além disso, apresenta-se, neste trabalho, uma visão geral sobre os mecanismos de coordenação multiagente e avalia a adequação de cada uma delas à coordenação distribuída de agentes (VANTs), visando cooperação. Assim, com o objetivo de melhorar o desempenho de uma operação de busca, esta pesquisa de mestrado propõe um modelo de VANTs cooperativos que combina mecanismos de coordenação multiagente, algoritmos de navegação e padrões de busca estabelecidos pelos principais órgãos responsáveis pelas operações de busca e salvamento. Visando avaliar a sensibilidade do percentual médio de detecção de objetos, bem como o tempo médio de busca, foi desenvolvido um simulador e milhares de simulações foram realizadas. Observou-se que, utilizando o modelo, VANTs cooperativos podem reduzir, em média, 57% do tempo de busca (comparando com uma busca de dois VANTs não cooperativos no mesmo cenário), mantendo a probabilidade média de detecção dos objetos próxima de 100% e sobrevoando apenas 30% do espaço de busca. / There are an increasing number of researches into UAV (Unmanned Aerial Vehicle) in the literature. These robots are quite suitable to dull, dirty and dangerous missions. Thus, an important application of these vehicles is the search operations involving multiple UAVs in which there is risk of collisions among aircrafts and the flight time is limited by the maximum time of pilot working hours. However, despite the huge potential use of the UAVs, cooperative search operations with this kind of flying robots are not yet occurring. This research topic is a new and multidisciplinary area of study in its beginning and there are several issues that can be studied, such as centralized versus decentralized control, path planning for cooperative flights, agent reasoning for UAV tactical planning, safety assessments, reliability in automatic target reconnaissance by cameras, agent coordination mechanisms applied to UAV cooperation and the application itself. Different path planning algorithms were studied aiming to attain the most suitable to these kinds of operations, and the conclusions are presented. In addition, official documents of Search and Rescue operations are also studied in order to know the best practices already established for this kind of operations, and, finally, an overview of the coordination multi-agent theory is presented and evaluated to achieve the UAV coordination. This work proposes a model that combines path planning algorithms, search patterns and multi-agent coordination techniques to obtain a cooperative UAV model. The great goal for cooperative UAV is to achieve such performance that the performance of the group overcomes the sum of the individual performances isolatedly. Then, aiming to analyze the average percentage of objects detection, and the average search time, a simulator was developed and thousands of simulations were run. It was observed that, using the proposed model, two cooperative UAVs can perform a search operation 57% faster than two non cooperative UAVs, keeping the average probability of objects detection approaching at 100% and flying only 30% of the search space.
323

Um modelo de sistemas multiagentes para partilha de conhecimento utilizando redes sociais comunitárias. / A multi-agent systems' model for knowledge sharing using communitary social networks.

Giménez Lugo, Gustavo Alberto 30 April 2004 (has links)
Este trabalho apresenta um modelo para sistemas multiagentes constituídos por agentes de informação destinados a auxiliar comunidades humanas que partilham conhecimento. Tais agentes são cientes do entorno social dos usuários, pois possuem representações do conhecimento dos mesmos e também das redes sociais que os circundam, organizadas subjetivamente. Conceitos pertencentes às suas ontologias são estendidos com informação organizacional para representar de forma explícita as situações nas quais foram aprendidos e utilizados. Discute-se como tais agentes autônomos podem raciocinar sobre o uso e a privacidade de conceitos em termos de construções organizacionais, possibilitando raciocinar sobre papéis sociais em comunidades abertas na Internet. / This work presents a model for multi-agent systems for information agents supporting information-sharing communities. Such agents are socially aware in the sense that they have representations of the users' knowledge and also of their social networks, which are subjectively organized. Concepts in their ontologies are extended with organizational information to record explicitly the situations in which they were learned and used. It is discussed how such autonomous agents are allowed to reason about concept usage and privacy in terms of organizational constructs, paving the way to reason about social roles in open Internet communities.
324

[en] FROM OBJECTS TO AGENTS: AN ASPECT ORIENTED APPROACH / [pt] OBJETOS E AGENTES: UMA ABORDAGEM ORIENTADA A ASPECTOS

ALESSANDRO FABRICIO GARCIA 13 July 2004 (has links)
[pt] Agentes de software incorporam várias propriedades específicas, como autonomia, adaptação, interação, aprendizagem e mobilidade. A inclusão dessas propriedades de agência é uma das maiores fontes de complexidade na construção de sistemas multiagentes. Dificilmente elas são modularizadas com abstrações e mecanismos da engenharia de software orientada a objetos. À medida que a complexidade da arquitetura interna dos agentes aumenta, essas propriedades tendem a se espalhar através dos vários módulos ou objetos do sistema. O espalhamento é observado desde fases preliminares de desenvolvimento, como a fase de definição arquitetural. O uso de abstrações e mecanismos existentes conduz ao projeto e à implementação de sistemas multiagentes que são difíceis de manter e reutilizar. Este trabalho apresenta uma abordagem orientada a aspectos para o desenvolvimento de sistemas baseados em agentes. A abordagem provê suporte para modularização e composição das propriedades de agência por meio de abstrações e mecanismos do paradigma orientado a aspectos. Além disso, tais propriedades são incorporadas de forma transparente à funcionalidade básica do sistema de software, desde a fase de definição arquitetural. A abordagem compreende três componentes: (i) um método arquitetural, (ii) uma linguagem de padrões e (iii) um framework para avaliação quantitativa. O método e a linguagem apresentam um conjunto de soluções orientadas a aspectos para a definição arquitetural, projeto e implementação de agentes de software. O framework define um conjunto de métricas e um modelo de qualidade que permite a avaliação empírica da nossa abordagem em termos de reusabilidade e manutenibilidade. Estudos experimentais qualitativos e quantitativos foram realizados para avaliar nossa proposta em diferentes domínios de aplicação. Os resultados empíricos concluíram que nossa abordagem permite a construção de sistemas baseados em agentes com modularização superior, menor acomplamento, menos linhas de código e menor complexidade interna dos componentes. / [en] Software engineers of Multi-Agent Systems (MASs) are faced with different concerns (properties), such as autonomy, adaptation, interaction, collaboration, learning, and mobility. Many of these agent concerns cannot be modularized based only on object-oriented abstractions. MAS developers however have relied mostly on objectoriented design techniques and on object-oriented programming languages, such as Java. As the agent complexity increases, the agent concerns tend to spread across several system components at the architectural, design and implementation levels. It often leads to a poor separation of agent concerns in the software system, and in turn to the production of MASs that are difficult to maintain and reuse. This thesis presents an innovative aspect-oriented approach for the seamless integration of agents into object-oriented software engineering from the architectural stage to the implementation stage. Aspect is the abstraction used to modularize agent concerns that crosscut several system components. The proposed approach encourages the separate handling of agent properties, and provides a disciplined scheme for their composition. The approach is composed of an architectural method, a pattern language, and an assessment framework. The architectural method and the pattern language provide aspect-oriented solutions for modularizing the agent concerns at different stages of design and implementation. The purpose of the assessment framework is to support the evaluation of the reusability and maintainability of aspect-oriented solutions based on a metrics suite and a quality model. Experimental studies in different application domains have been conducted to assess the proposed approach based on qualitative and quantitative criteria. The use of the aspect-oriented solutions resulted in fewer lines of code, fewer design and implementation components, lower internal complexity of system components, and lower coupling.
325

Analyse et contrôle de systèmes de dynamiques d'opinions / Analysis and control of opinion dynamics

Dietrich, Florian 22 November 2017 (has links)
Les dynamiques d'opinions suscitent un regain d'intérêt de la part des communautés d'Automatique et de Mathématiques Appliquées. Cela peut s'expliquer par l'émergence des réseaux sociaux en ligne et de la possibilité d'exploiter et comprendre les comportements et données associés. Les modèles de dynamiques d'opinions sont des cas particuliers de systèmes multi-agents. Ces systèmes ont des applications diverses comme par exemple le contrôle du comportement d'une flotte de robots collaboratifs. Un système de dynamique d'opinions est ainsi constitué de plusieurs agents. L'état de chaque agent est alors modélisé par un réel qui représente l'opinion de celui-ci à propos d'un certain sujet. Les modèles mathématiques de dynamiques d'opinions décrivent alors l'évolution des opinions des agents dans le temps. De nombreux résultats ont été obtenus sur le régime asymptotique de ces systèmes, notamment sur la convergence vers le consensus, lorsque les opinions de tous les agents du système tendent vers la même valeur. Le régime transitoire, moins bien connu, présente également des phénomènes intéressants comme la formation d'accords locaux transitoires mais qui sont plus délicats à définir. Une étude de ces phénomènes est présentée pour des systèmes de dynamiques d'opinions à temps discret avec fonctions d'influence génériques dépendant de l'état. La contribution principale propose un critère de détection de la formation de ces accords locaux, ainsi que la prédiction de la durée pendant laquelle ce critère est vérifié. La seconde partie de cette thèse se concentre sur les dynamiques d'opinions en temps continu dont un des agents, appelé leader, a un rôle particulier : l'évolution de son opinion est contrôlable. Le leader est utilisé pour rassembler tous les agents dans son voisinage en temps fini, puis pour les amener vers une valeur de consensus désirée. La loi de commande proposée est valide pour des systèmes à fonctions d'influence dépendant du temps et de l'état et sous certaines conditions. De plus, le problème de contrôle en temps optimal consistant à rassembler tous les agents dans le voisinage du leader en temps minimal est examiné. Ceci est effectué dans le cas particulier de fonctions d'influence dépendant uniquement de l'état. Afin de déterminer la classe des commandes optimales admissible, le Principe du Maximum de Pontryagin est utilisé. Dans un cadre général, la commande optimale est précisée sous la forme de relations implicites. Pour le cas particulier où il n'y a pas d'interaction entre les agents, la loi de commande en temps optimal a été obtenue en pratique pour toute condition initiale / Opinion dynamics systems aroused renewed interest in the Control System Theory and Applied Mathematics communities. This can be explained by the emergence of online social networks and the possibility of exploiting and understanding associated behaviours and data. Opinion dynamic models are special cases of multi-agent systems. These systems have various applications such as controlling the behaviour of a fleet of collaborative robots. A system of opinion dynamics is thus composed of several agents. The state of each agent is then modeled by a real number, which represents the agent's opinion on a certain subject. The mathematical models of opinion dynamics then describe the evolution of agents' opinions over time. Many results have been obtained on the asymptotic behaviour of these systems, notably on convergence towards consensus, when the opinion of all agents of the system tend towards the same value. The less well known transient state also presents interesting phenomena such as the formation of local transient agreements, which are more tricky to define. A study of these phenomena is presented for discrete-time opinion dynamics systems with generic state dependent influence functions. The main contribution proposes a criterion for detecting the formation of these local agreements, as well as a prediction of the duration during which this criterion is verified. The second part of this thesis focuses on opinion dynamics in continuous time in which one of the agents, called leader, has a particular role: the evolution of its opinion is controllable. For systems with time and state-dependent influence functions and under certain conditions, a control law is presented that allows the leader to gather all agents in its neighbourhood in finite time and then steer them to a desired consensus value. In addition, the problem of time optimal control which consists in bringing all agents together in the neighborhood of the leader in minimal time is also examined for the case of only state-dependent influence functions. The Pontryagin Maximum Principle specifies the class of admissible optimal controls with implicit expressions within a general framework. For the particular case where there is no interaction between agents, the time-optimal control law has been obtained in practice for any initial conditions
326

Système multi-agents de pilotage réactif des parcours patients au sein des systèmes hospitaliers / Reactive multi-agent control system of the patient flow in healthcare system

Benhajji, Noura 24 November 2017 (has links)
Nos travaux de recherches sont des travaux supports pour les gestionnaires de l’hôpital Robert Pax de Sarreguemines, et plus généralement de tout centre hospitalier pour développer des approches centrées sur le patient. Nous nous sommes inspirés des approches centrées sur le produit issues du domaine industriel qui ont été proposées pour répondre aux exigences croissantes de gestion des produits dans un environnement de plus en plus incertain. Par analogie, les systèmes de production de soins centrés patient peuvent être assimilés aux systèmes de production de biens centrés produit. Cependant, il ne faut pas perdre de vue la spécificité des systèmes de production de soins : le facteur humain. Cette spécificité est à l’origine de leur caractère complexe, aléatoire et imprévisible. Par ailleurs, les approches de pilotage, que ce soit dans le milieu industriel ou hospitalier, sont majoritairement des modèles mathématiques et des modèles de simulation utilisant une approche de gestion centrée sur une ou plusieurs ressources considérées comme critiques. C’est pourquoi il nous a paru judicieux d’opter pour une approche centrée patient basée sur le paradigme multi-agents. Nous proposons alors, un système multi-agents de pilotage réactif dynamique et distribué centré patient du parcours patient au sein des systèmes hospitaliers. L’alternative que nous proposons consiste à utiliser une approche centrée patient et basée sur les agents permettant de minimiser les délais d’attente, ainsi que la durée de séjour, et par conséquent les coûts des soins, tout en assurant un soin de qualité pour l’ensemble des patients et une meilleure gestion des ressources hospitalières / Through our research, we offer a support tool for the managers in Robert Pax hospital in Sarreguemine (France), and more generally any hospital center wishing to develop a patient centered approach. We were inspired by « product centered » approaches emerging from industrial domain which were proposed to answer the increasing requirements of products management. By analogy, health care systems patient centered can be assimilated to production systems product centered. However, it is important not to lose sight of the specificities of health care systems which is the human factor. This specificity makes this system complex, random and unpredictable. Besides, the approaches used in industrial or hospital environment, are mainly mathematical models and simulation approaches centered on one ore several resources categorized as critical. In that sense, it seemed judicious to choose a patient centered approach based on a multi-agent paradigm. We proposed a Reactive multi-agent control system of the patient flow in healthcare system. The proposed alternative is a patient centered approach allowing to minimize the patients waiting time and the length of their stay and consequently the care costs. The proposed approach also ensures the care quality and an optimal use of the hospital resources
327

[en] MDA BASED APPROACH FOR DEVELOPING MULTI-AGENT SYSTEMS / [pt] USANDO A ABORDAGEM MDA NO DESENVOLVIMENTO DE SISTEMAS MULTI-AGENTES

BEATRIZ ALVES DE MARIA 17 June 2005 (has links)
[pt] Sistemas multi-agentes (SMA) diferem de sistemas que não são baseados em agentes devido ao fato dos agentes serem unidades autônomas capazes de ações flexíveis e inteligentes. Por este motivo é proposto na literatura um grande número de metodologias, frameworks e linguagens para dar apoio a construção deste tipo de sistema. Muitas dessas metodologias e suas ferramentas provêm da comunidade de inteligência artificial e estão focadas em uma arquitetura específica de agentes. Este trabalho propõe o uso da arquitetura Model Driven Architecture (MDA), descrita pela OMG, no processo de desenvolvimento de SMA. MDA é uma arquitetura para desenvolvimento de software estruturada em etapas de modelagem que dá suporte a todo o ciclo de desenvolvimento de um sistema. O processo de desenvolvimento proposto está dividido de acordo com as etapas apresentadas por MDA. Na etapa PIM, onde são especificados modelos independentes de plataforma, propomos a utilização da linguagem de modelagem MAS-ML para SMA. Na etapa PSM, onde são definidos modelos específicos de plataforma, propomos utilizar a linguagem de modelagem UML. Os modelos MAS-ML definidos na etapa PIM são transformados em modelos UML na etapa PSM com base em um framework para implementação de SMA utilizando orientação a objetos. Na ultima etapa do desenvolvimento, o código da aplicação é gerado a partir dos modelos UML. Este trabalho detalha as etapas PIM e PSM do processo de desenvolvimento de SMA e as transformações necessárias para a geração de código. Para demonstrar a aplicação do processo proposto são apresentadas duas aplicações de SMA desenvolvidas utilizando o mesmo. Ao final, apresenta-se a ferramenta MAS-ML Tool desenvolvida para dar apoio ao processo de desenvolvimento proposto. Esta ferramenta implementa todas as etapas presentes no processo, permitindo assim a implementação de SMA a partir de sua modelagem. / [en] Multi-agent systems (MAS) differ from non-agent systems because agents are intended to be autonomous units capable of flexible and intelligent actions. For this reason it is proposed in the literature a great number of methodologies frameworks and languages to support the development of these systems. Several methodologies and their tools are come from artificial intelligent community and are focused in a specific agent architecture. This work proposes the use of the Model Driven Architecture (MDA), described by OMG, in the development process of MAS. MDA specifies a structured software development process in modeling stages that supports all system development life cycle. The proposed development process is divided according to the MDA stages. In PIM stage, where platform independent models are specified, we propose the use of MAS-ML modeling language for MAS. In PSM stage, where platform specific models are specified, we propose the use of UML modeling language. The MASML models defined on PIM stage are transformed in UML models at PSM stage, based on an object-oriented framework for implementing MAS. In the last development stage, the application code is generated from UML models. This work details the PIM and PSM stages of the MAS development process and the models transformations to generate source code. To exemplify the applicability of the proposed MAS development process, two different MAS applications were developed based on the process. Finally, a MAS-ML tool is presented. Such tool was developed to support the proposed development process. The tool implements all stages presented in the process, allowing the modeling and implementation of MAS.
328

Constrained coalition formation among heterogeneous agents for the multi-agent programming contest

Rodrigues, Tabajara Krausburg 26 March 2018 (has links)
Submitted by PPG Ci?ncia da Computa??o (ppgcc@pucrs.br) on 2018-05-28T12:31:15Z No. of bitstreams: 1 TABAJARA_KRAUSBURG_RODRIGUES_DIS.pdf: 4049392 bytes, checksum: 154302eff9df959cfa74d6c0faec5d4e (MD5) / Approved for entry into archive by Sheila Dias (sheila.dias@pucrs.br) on 2018-06-06T13:05:51Z (GMT) No. of bitstreams: 1 TABAJARA_KRAUSBURG_RODRIGUES_DIS.pdf: 4049392 bytes, checksum: 154302eff9df959cfa74d6c0faec5d4e (MD5) / Made available in DSpace on 2018-06-06T13:35:29Z (GMT). No. of bitstreams: 1 TABAJARA_KRAUSBURG_RODRIGUES_DIS.pdf: 4049392 bytes, checksum: 154302eff9df959cfa74d6c0faec5d4e (MD5) Previous issue date: 2018-03-26 / Esta disserta??o apresenta um estudo sobre forma??o de coaliz?es entre agentes heterog?neos para a competi??o de programa??o multiagente de 2017. Foi investigado e aplicado a forma??o de estruturas de coaliz?es entre agentes para resolver problemas log?sticos simulados sobre o mapa de uma cidade real. A fim de atingir o objetivo deste trabalho, foram integrados algoritmos formadores de coaliz?es na plataforma JaCaMo por meio de um artefato CArtAgO chamado CFArtefact. Foi utilizada a implementa??o provida pelo time SMART-JaCaMo (time participante da competi??o multiagente), para experimentar a forma??o de coaliz?es na competi??o. Tr?s abordagens foram avaliadas no dom?nio da competi??o em diferentes configura??es. A primeira abordagem utiliza somente aloca??o de tarefas para resolver o problema. A segunda e a terceira abordagem utilizam a t?cnica de forma??o de coaliz?es anteriormente ? aloca??o de tarefas; dentre estas abordagens, uma utiliza um algor?timo ?timo para resolver o problema e a outra um heur?stico. As an?lises dos experimentos realizados mostram que algor?timos formadores de coaliz?es podem melhorar a performance do time participante da competi??o quando a taxa de trabalhos gerados pelo simulador ? baixa. Entretanto, conforme a taxa de trabalhos aumenta, a abordagem que realiza somente aloca??o de tarefas obt?m um desempenho melhor quando comparada as demais. Mesmo a abordagem heur?stica tem desempenho pr?ximo ? abordagem ?tima para coaliz?es. Desta forma, ? poss?vel concluir que forma??o de coaliz?es possui grande valia para balancear os agentes para um conjunto de trabalhos que precisa ser completado. / This work focuses on coalition formation among heterogeneous agents for the 2017 multiagent programming contest. An agent is a computer system that is capable of independent action to achieve its goals. In order to increase the effectiveness of the agents, we can organise them into coalitions, in which the agents collaborate with each other to achieve individual or common goals. We investigate and apply coalition structure generation (the first activity of the coalition formation process) in simulated scenarios, specifically the 2017 contest scenario, where the agents forming a competing team cooperate to solve logistic problems simulated on the map of a real city. In order to achieve our goal, we integrate coalition formation algorithms into the JaCaMo platform by means of a CArtAgO artefact, named CFArtefact. We use the implementation of the SMART JaCaMo team for experimenting with the coalition formation approach in the contest scenario. We experiment on three approaches in the contest domain with different configurations. In the first, we use only a taskallocation mechanism, while the other approaches use an optimal coalition formation algorithm and a heuristic coalition formation algorithm. We conducted several experiments to compare the advantages of each approach. Our results show that coalition formation algorithms can improve the performance of a participating team when dealing with low job rates (i.e., how quickly new jobs are created by the simulation). However, as we increase the job rate, the approach using only task allocation has better performance. Even a heuristic coalition formation approach has close performance to the optimal one in that case. Coalition formation can play an important role when we aim to balance each group of agents to accomplish some particular goal given a larger team of cooperating agents.
329

Méthodes d’optimisation distribuée pour l’exploitation sécurisée des réseaux électriques interconnectés / Distributed optimization methods for the management of the security of interconnected power systems

Velay, Maxime 25 September 2018 (has links)
Notre société étant plus dépendante que jamais au vecteur électrique, la moindre perturbation du transport ou de l’acheminement de l’électricité a un impact social et économique important. La fiabilité et la sécurité des réseaux électriques sont donc cruciales pour les gestionnaires de réseaux, en plus des aspects économiques. De plus, les réseaux de transport sont interconnectés pour réduire les coûts des opérations et pour améliorer la sécurité. Un des plus grand défis des gestionnaires des réseaux de transport est ainsi de se coordonner avec les réseaux voisins, ce qui soulève des problèmes liés à la taille du problème, à l’interopérabilité et à la confidentialité des données.Cette thèse se focalise principalement sur la sécurité des opérations sur les réseaux électriques, c’est pourquoi l’évolution des principales caractéristiques des blackouts, qui sont des échecs de la sécurité des réseaux, sont étudiés sur la période 2005-2016. L’approche de cette étude consiste à déterminer quelles sont les principales caractéristiques des incidents de ces 10 dernières années, afin d’identifier ce qui devrait être intégré pour réduire le risque que ces incidents se reproduisent. L’évolution a été étudiée et comparé avec les caractéristiques des blackouts qui se sont produit avant 2005. L’étude se focalise sur les préconditions qui ont mené à ces blackouts et sur les cascades, et particulièrement sur le rôle de la vitesse des cascades. Les caractéristiques importante sont extraites et intégrées dans la suite de notre travail.Un algorithme résolvant un problème préventif d’Optimal Power Flow avec contraintes de sécurité (SCOPF) de manière distribuée est ainsi développé. Ce problème consiste en l’ajout de contraintes qui assure qu’après la perte de n’importe quel appareil d’importance, le nouveau point d’équilibre, atteint suite au réglage primaire en fréquence, respecte les contraintes du système. L’algorithme développé utilise une décomposition fine du problème et est implémenté sous le paradigme multi-agent, basé sur deux catégories d’agents : les appareils et les bus. Les agents sont coordonnés grâce à l’ « Alternating Direction Method of Multipliers (ADMM)» et grâce à un problème de consensus. Cette décomposition procure l’autonomie et la confidentialité nécessaire aux différents acteurs du système, mais aussi, un bon passage à l’échelle par rapport à la taille du problème. Cet algorithme a aussi pour avantage d’être robuste à n’importe quelle perturbation, incluant la séparation du système en plusieurs régions.Puis, pour prendre en compte l’incertitude sur la production créée par les erreurs de prédiction des fermes éoliennes, une approche distribuée à deux étapes est développée pour résoudre un problème d’Optimal Power Flow avec contraintes probabilistes (CCOPF), d’une manière complétement distribuée. Les erreurs de prédiction des fermes éoliennes sont modélisées par des lois normales indépendantes et les écarts par rapport aux plannings de production sont considérés compensés par le réglage primaire en fréquence. La première étape de l’algorithme a pour but de déterminer des paramètres de sensibilités nécessaires pour formuler le problème. Les résultats de cette étape sont ensuite des paramètres d’entrée de la seconde étape qui, elle, résout le problème de CCOPF. Une extension de cette formulation permet d’ajouter de la flexibilité au problème en permettant la réduction de la production éolienne. Cet algorithme est basé sur la même décomposition fine que précédemment où les agents sont également coordonnés par l’ADMM et grâce à un problème de consensus. En conclusion, cet algorithme en deux étapes garantit la confidentialité et l’autonomie des différents acteurs, et est parallèle et adaptée aux plateformes hautes performances. / Our societies are more dependent on electricity than ever, thus any disturbance in the power transmission and delivery has major economic and social impact. The reliability and security of power systems are then crucial to keep, for power system operators, in addition to minimizing the system operating cost. Moreover, transmission systems are interconnected to decrease the cost of operation and improve the system security. One of the main challenges for transmission system operators is therefore to coordinate with interconnected power systems, which raises scalability, interoperability and privacy issues. Hence, this thesis is concerned with how TSOs can operate their networks in a decentralized way but coordinating their operation with other neighboring TSOs to find a cost-effective scheduling that is globally secure.The main focus of this thesis is the security of power systems, this is why the evolution of the main characteristics of the blackouts that are failures in power system security, of the period 2005-2016 is studied. The approach consists in determining what the major characteristics of the incidents of the past 10 years are, to identify what should be taken into account to mitigate the risk of incidents. The evolution have been studied and compared with the characteristics of the blackouts before 2005. The study focuses on the pre-conditions that led to those blackouts and on the cascades, and especially the role of the cascade speed. Some important features are extracted and later integrated in our work.An algorithm that solve the preventive Security Constrained Optimal Power Flow (SCOPF) problem in a fully distributed manner, is thus developed. The preventive SCOPF problem consists in adding constraints that ensure that, after the loss of any major device of the system, the new steady-state reached, as a result of the primary frequency control, does not violate any constraint. The developed algorithm uses a fine-grained decomposition and is implemented under the multi-agent system paradigm based on two categories of agents: devices and buses. The agents are coordinated with the Alternating Direction method of multipliers in conjunction with a consensus problem. This decomposition provides the autonomy and privacy to the different actors of the system and the fine-grained decomposition allows to take the most of the decomposition and provides a good scalability regarding the size of the problem. This algorithm also have the advantage of being robust to any disturbance of the system, including the separation of the system into regions.Then, to account for the uncertainty of production brought by wind farms forecast error, a two-step distributed approach is developed to solve the Chance-Constrained Optimal Power Flow problem, in a fully distributed manner. The wind farms forecast errors are modeled by independent Gaussian distributions and the mismatches with the initials are assumed to be compensated by the primary frequency response of generators. The first step of this algorithm aims at determining the sensitivity factors of the system, needed to formulate the problem. The results of this first step are inputs of the second step that is the CCOPF. An extension of this formulation provides more flexibility to the problem and consists in including the possibility to curtail the wind farms. This algorithm relies on the same fine-grained decomposition where the agents are again coordinated by the ADMM and a consensus problem. In conclusion, this two-step algorithm ensures the privacy and autonomy of the different system actors and it is de facto parallel and adapted to high performance platforms.
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Verification of behaviourist multi-agent systems by means of formally guided simulations / Verificação de sistemas multi-agentes comportamentalistas através de simulações formalmente guiadas

Silva, Paulo Salem da 28 November 2011 (has links)
Multi-agent systems (MASs) can be used to model phenomena that can be decomposed into several interacting agents which exist within an environment. In particular, they can be used to model human and animal societies, for the purpose of analysing their properties by computational means. This thesis is concerned with the automated analysis of a particular kind of such social models, namely, those based on behaviourist principles, which contrasts with the more dominant cognitive approaches found in the MAS literature. The hallmark of behaviourist theories is the emphasis on the definition of behaviour in terms of the interaction between agents and their environment. In this manner, not merely re exive actions, but also learning, drives, and emotions can be defined. More specifically, in this thesis we introduce a formal agent architecture (specified with the Z Notation) based on the Behaviour Analysis theory of B. F. Skinner, and provide a suitable formal notion of environment (based on the pi-calculus process algebra) to bring such agents together as an MAS. Simulation is often used to analyse MASs. The techniques involved typically consist in implementing and then simulating a MAS several times to either collect statistics or see what happens through animation. However, simulations can be used in a more verification-oriented manner if one considers that they are actually explorations of large state-spaces. In this thesis we propose a novel verification technique based on this insight, which consists in simulating a MAS in a guided way in order to check whether some hypothesis about it holds or not. To this end, we leverage the prominent position that environments have in the MASs of this thesis: the formal specification of the environment of a MAS serves to compute the possible evolutions of the MAS as a transition system, thereby establishing the state-space to be investigated. In this computation, agents are taken into account by being simulated in order to determine, at each environmental state, what their actions are. Each simulation execution is a sequence of states in this state-space, which is computed on-the-fly, as the simulation progresses. The hypothesis to be investigated, in turn, is given as another transition system, called a simulation purpose, which defines the desirable and undesirable simulations (e.g., \"every time the agent does X, it will do Y later\"). It is then possible to check whether the MAS satisfies the simulation purpose according to a number of precisely defined notions of satisfiability. Algorithmically, this corresponds to building a synchronous product of these two transitions systems (i.e., the MAS\'s and the simulation purpose) on-the-fly and using it to operate a simulator. That is to say, the simulation purpose is used to guide the simulator, so that only the relevant states are actually simulated. By the end of such an algorithm, it delivers either a conclusive or an inconclusive verdict. If conclusive, it becomes known whether the MAS satisfies the simulation purpose with respect to the observations made during simulations. If inconclusive, it is possible to perform some adjustments and try again. In summary, then, in this thesis we provide four novel elements: (i) an agent architecture; (ii) a formal specification of the environment of these agents, so that they can be composed into an MAS; (iii) a structure to describe the property of interest, which we named simulation purpose; and (iv) a technique to formally analyse the resulting MAS with respect to a simulation purpose. These elements are implemented in a tool, called Formally Guided Simulator (FGS). Case studies executable in FGS are provided to illustrate the approach. / Sistemas multi-agentes (SMAs) podem ser usados para modelar fenômenos que podem ser decompostos em diversos agentes que interagem entre si dentro de um ambiente. Em particular, eles podem ser usados para modelar sociedades humanas e animais, com a finalidade de se analisar as suas propriedades computacionalmente. Esta tese trata da análise automatizada de um tipo particular de tais modelos sociais, a saber, aqueles baseados em princípios behavioristas, o que contrasta com as abordagens cognitivas mais dominante na literatura de SMAs. A principal característica das teorias behaviorista é a ênfase na descrição do comportamento em termos da interação entre agentes e seu ambiente. Desta forma, não apenas ações refl exivas, mas também de aprendizado, motivações, e as emoções podem ser definidas. Mais especificamente, nesta tese apresentamos uma arquitetura de agentes formal (especificada através da Notação Z) baseada na teoria da Análise do Comportamento de B. F. Skinner, e fornecemos uma noção adequada e formal de ambiente (com base na álgebra de processos pi-calculus) para colocar tais agentes juntos em um SMA. Simulações são freqüentemente utilizadas para se analisar SMAs. As técnicas envolvidas tipicamente consistem em simular um SMA diversas vezes, seja para coletar estatísticas, seja para observar o que acontece através de animações. Contudo, simulações podem ser usadas de forma a pertmitir a realização de verificações automatizadas do SMA caso sejam entendidas como explorações de grandes espaços-de-estados. Nesta tese propomos uma técnica de verificação baseada nessa observação, que consiste em simular um SMA de uma forma guiada, a fim de se determinar se uma dada hipótese sobre ele é verdadeira ou não. Para tal fim, tiramos proveito da importância que os ambientes têm nesta tese: a especificação formal do ambiente de um SMA serve para calcular as evoluções possíveis do SMA como um sistema de transição, estabelecendo assim o espaço-de-estados a ser investigado. Neste cálculo, os agentes são levados em conta simulando-os, a fim de determinar, em cada estado do ambiente, quais são suas ações. Cada execução da simulação é uma seqüência de estados nesse espaço-de-estados, que é calculado em tempo de execução, conforme a simulação progride. A hipótese a ser investigada, por sua vez, é dada como um outro sistema de transição, chamado propósito de simulação, o qual define as simulações desejáveis e indesejáveis (e.g., \"sempre que o agente fizer X, ele fará Y depois\"). Em seguida, é possível verificar se o SMA satisfaz o propósito de simulação de acordo com uma série de relações de satisfatibilidade precisamente definidas. Algoritmicamente, isso corresponde a construir um produto síncrono desses dois sistemas de transições (i.e., o do SMA e o do propósito de simulação) em tempo de execução e usá-lo para operar um simulador. Ou seja, o propósito de simulação é usado para guiar o simulador, de modo que somente os estados relevantes sejam efetivamente simulados. Ao terminar, um tal algoritmo pode fornecer um veredito conclusivo ou inconclusivo. Se conclusivo, descobre-se se o SMA satisfaz ou não o propósito de simulação com relação às observações feitas durante as simulações. Se inconclusivo, é possível realizar alguns ajustes e tentar novamente. em resumo, portanto, nesta tese propomos quatro novos elementos: (i) uma arquitetura de agente, (ii) uma especificação formal do ambiente desses agentes, de modo que possam ser compostos em um SMA, (iii) uma estrutura para descrever a propriedade de interesse, a qual chamamos de propósito de simulação, e (iv) uma técnica para se analisar formalmente o SMA resultante com relação a um propósito de simulação. Esses elementos estão implementados em uma ferramenta, denominada Simulador Formalmente Guiado (FGS, do inglês Formally Guided Simulator). Estudos de caso executáveis no FGS são fornecidos para ilustrar a abordagem.

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