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Multi-agent systems represent a group of agents that cooperate to solve common tasks in a dynamic environment. Multi-agent control systems have been widely studied in the past few years. The control of multi-agent systems relates to synthesizing control schemes for systems which are inherently distributed and composed of multiple interacting entities. Because of the wide applications of multi-agent theories in large and complex control systems, it is necessary to develop a framework to simplify the process of developing control schemes for multi-agent systems. <br /><br /> In this study, a framework is proposed for the distributed control and coordination of multi-agent systems. In the proposed framework, the control of multi-agent systems is regarded as achieving decentralized control and coordination of agents. Each agent is modeled as a Coordinated Hybrid Agent (CHA) which is composed of an intelligent coordination layer and a hybrid control layer. The intelligent coordination layer takes the coordination input, plant input and workspace input. After processing the coordination primitives, the intelligent coordination layer outputs the desired action to the hybrid layer. In the proposed framework, we describe the coordination mechanism in a domain-independent way, as simple abstract primitives in a coordination rule base for certain dependency relationships between the activities of different agents. The intelligent coordination layer deals with the planning, coordination, decision-making and computation of the agent. The hybrid control layer of the proposed framework takes the output of the intelligent coordination layer and generates discrete and continuous control signals to control the overall process. In order to verify the feasibility of the proposed framework, experiments for both heterogeneous and homogeneous Multi-Agent Systems (MASs) are implemented. In addition, the stability of systems modeled using the proposed framework is also analyzed. The conditions for asymptotic stability and exponential stability of a CHA system are given. <br /><br /> In order to optimize a Multi-Agent System (MAS), a hybrid approach is proposed to address the optimization problem for a MAS modeled using the CHA framework. Both the event-driven dynamics and time-driven dynamics are included for the formulation of the optimization problem. A generic formula is given for the optimization of the framework. A direct identification algorithm is also discussed to solve the optimization problem.

Designing Cyber-Physical Systems is hard. Physical testing can be slow, expensive and dangerous. Furthermore computational components make testing all possible behavior unfeasible. Model-based design mitigates these issues by making it possible to iterate over a design much faster. Traditional simulation tools can produce useful results, but their results are traditionally approximations that make it impossible to distinguish a useful simulation from one dominated by numerical error. Verification tools require skills in formal specification and a priori understanding of the particular dynamical system being studied. This thesis presents rigorous simulation, an approach to simulation that uses validated numerics to produce results that quantify and bound all approximation errors accumulated during simulation. This makes it possible for the user to objectively and reliably distinguish accurate simulations from ones that do not provide enough information to be useful. Explicitly quantifying the error in the output has the side-effect of leading to a tool for dealing with inputs that come with quantified uncertainty. We formalize the approach as an operational semantics for a core subset of the domain-specific language Acumen. The operational semantics is extended to a larger subset through a translation. Preliminary results toward proving the soundness of the operational semantics with respect to a denotational semantics are presented. A modeling environment with a rigorous simulator based on the operational semantics is described. The implementation is portable, and its source code is freely available. The accuracy of the simulator on different kinds of systems is explored through a set of benchmark models that exercise different aspects of a rigorous simulator. A case study from the automotive domain is used to evaluate the applicability of the simulator and its modeling language. In the case study, the simulator is used to compute rigorous bounds on the output of a model.

Identificar e localizar faltas em alimentadores de distribuição representa um passo importante para a melhoria da qualidade de energia, pois proporciona impactos diretos sobre o tempo de inspeção. Na verdade, a duração da inspeção implica consideravelmente no intervalo em que os consumidores estão sem energia elétrica, quando ocorre uma interrupção não programada. O objetivo deste trabalho é fornecer um sistema de detecção automática de curtos-circuitos, permitindo aos profissionais das companhias de distribuição acompanhar e monitorar de maneira on-line a ocorrência de possíveis faltas e transitórios eletromagnéticos observados na rede primária de distribuição. A abordagem de detecção utiliza um sistema híbrido que combina ferramentas inteligentes e convencionais para identificar e localizar faltas em redes primárias. Os resultados que foram compilados demonstram grande potencialidade de aplicação da proposta em sistemas de distribuição. / Efficient faults identification and location in power distribution lines constitute an important step for power quality improvement, since they provide direct impacts on the inspection time. In fact, the duration of inspection implies directly in the time interval where consumers are without power, considering here the occurrence of a non-programmed interruption. The objective of this work is to provide an automated fault detection system, allowing to the power companies engineers to online track and monitor the possible occurrence of faults and electromagnetic transients observed in the primary network for the distribution circuits. The detection approach uses a hybrid system, which combines a set of intelligent and conventional tools to identify and locate faults in the primary networks. Validation results show great application potential in distribution systems.

La thèse traite de l’utilisation des systèmes hybrides dans le contexte particulier des communications sécurisées et de la cryptographie. Ce travail est motivé par les faits suivants. L’essor considérable des communications qui a marqué ces dernières décennies nécessite des besoins croissants en terme de sécurité des échanges et de protection de l’information. Dans ce contexte, la cryptographie joue un rôle central puisque les informations transitent la plupart du temps au travers de canaux publics. Parmi les nombreuses techniques de chiffrement existants, le chiffrement par flot se distingue tout particulièrement lorsqu’on le débit d’une communication sécurisée est privilégié. Les chiffreurs par flot sont construits à partir de générateurs de séquences complexes décrits par des systèmes dynamiques et devant être synchronisés de part et d’autre du canal d’échanges. Les objectifs et les résultats de ce travail se déclinent en trois points. Tout d’abord, l’intérêt d’utiliser des systèmes hybrides en tant que primitives cryptographiques est motivé. Par la suite, une étude comparative est menée afin d’établir une connexion entre les algorithmes de masquage de l’information basés sur le chaos et les algorithmes de chiffrement usuels. L’étude porte exclusivement sur des considérations structurelles et repose sur des concepts de la théorie du contrôle, en particulier l’inversibilité à gauche et la platitude. On montre que la technique de masquage dite par inclusion, qui consiste à injecter l’information à protéger dans une dynamique complexe, est la plus efficace. De plus, on montre que sous la condition de platitude, un système de masquage par inclusion est structurellement équivalent à un chiffreur par flot particulier appelé auto-synchronisant. Enfin, des méthodes de cryptanalyse pour évaluer la sécurité du masquage par inclusion sont proposées pour une classe particulières de systèmes hybrides à savoir les systèmes linéaires à commutations. A nouveau, des concepts de la théorie du contrôle sont utilisés, il s’agit de l’identifiabilité paramétrique et des algorithmes d’identification. Des spécificités relatives au contexte particulier de la cryptographie sont prises en compte. En effet, contrairement à la plupart des cas rencontrés dans le domaine du contrôle où les variables des modèles dynamiques sont continues car relatives à des systèmes physiques, les variables prennent ici des valeurs discrètes. Les modèles dynamiques sont en effet décrits non plus dans le corps des réels mais dans des corps finis en vue d’une implémentation sur des machines à états finis tels ordinateur ou tout autre dispositif numérique / This manuscript deals with a specific engineering application involving hybrid dynamical systems : secure communications and cryptography. The work is motivated by the following facts. The considerable progress in communication technology during the last decades has led to an increasing need for security in information exchanges. In this context, cryptography plays a major role as information is mostly conveyed through public networks. Among a wide variety of cryptographic techniques, stream ciphers are of special interest for high speed encryption. They are mainly based on generators of complex sequences in the form of dynamical systems, which must be synchronized at the transmitter and receiver sides. The aim of this work is threefold. First, the interest of resorting to hybrid dynamical systems for the design of cryptographic primitives is motivated. Secondly, a connection between chaotic and conventional cryptography is brought out by comparing the respective algorithms proposed in the open literature. The investigation focuses on structural consideration. Control theoretical concepts, in particular left invertibility and flatness, are the central tools to this end. It is shown that the so-called message-embedding technique, consisting in injecting the information to be concealed into a dynamical system, is the most relevant technique. Furthermore, it is shown that, under the flatness condition, the resulting cipher acts as a self-synchronizing stream cipher. Finally, cryptanalytic methodologies for assessing the security of the message-embedded cryptosystem involving a special class of hybrid systems, namely the switched linear systems, are proposed. Again concepts borrowed from control theory, namely identifiability and identification, are considered. Specificities related to the context are taken into account. The variables describing the dynamical systems do not take values in a continuum unlike what usually happens in automatic control when physical models are considered. They rather take values in finite cardinality sets, especially finite fields, since an implementation in finite state machines, say computers or digital electronic devices, is expected

Sistemas Supervisórios Híbridos podem ser definidos como sistemas de controle cujos estados são representados por variáveis discretas e contínuas, e cuja dinâmica é determinada em função do tempo e da ocorrência de eventos discretos. O desenvolvimento desta classe de Sistemas Supervisórios pode ser dividido em duas fases. A 1ª Fase consiste na elaboração de um modelo protótipo para o Sistema Supervisório, que é descrito usando um formalismo, e que é validado com base nas especificações do problema. Na 2ª Fase, este modelo, já validado, é convertido na linguagem de programação do Sistema Supervisório propriamente dito. Esta tese concentra-se na 1ª Fase, para qual abordam-se três questões principais: (1) a escolha do formalismo de modelagem; (2) como construir o modelo do Sistema Supervisório Híbrido usando este formalismo; e (3) como validar o Sistema Supervisório Híbrido usando o modelo construído. Para questão (1), introduz-se um novo formalismo de modelagem baseado na aplicação dos conceitos de Orientação a Objetos (OO) às redes Predicado Transição Diferenciais (redes PTD). Este novo formalismo é chamado de redes PTD-OO. No que se refere a questão (2), é proposto um procedimento para obtenção do modelo do Sistema Supervisório em redes PTD-OO usando os diagramas da UML (‘Unified Modeling Language’). Finalmente, para a questão (3), o problema de validação é abordado através da definição de um conjunto de propriedades que o modelo em redes PTD-OO deve respeitar afim de que sejam garantidos os requisitos do Sistema Supervisório. Estas propriedades são, então, verificadas através de um procedimento proposto para análise de redes PTD-OO. / Hybrid Supervisory Systems can be described as control systems with states that are represented by both discrete and continuous variables. Their dynamics are function of time and depend also on the occurrence of discrete events. The development of Hybrid Supervisory Systems can be divided in two phases. In the 1st Phase, a prototype-model for the Supervisory System is described using a specific formalism and is validated based on the system requirements. In the 2nd Phase, this validated model is converted to the programming language of the Supervisory System. This thesis is focused on the 1st Phase of Hybrid Supervisory System development. It approaches three main issues: (1) the choice of the modelling formalism; (2) how to build the Hybrid Supervisory System model using this formalism; and (3) how to validate the Hybrid Supervisory System using this model. For issue (1), a new modelling formalism is introduced based on Differential Predicate Transition nets (DPT nets) and object-oriented (OO) paradigm. This new formalism is called DPT-OO net. Then, for the issue (2), a modelling procedure that assists the building of the DPT-OO net model using Unified Modelling Language (UML) diagrams is proposed. Finally, for the issue (3), the validation problem is approached by defining a set of properties of the DPT-OO net model that assures the Supervisory System requirements. These properties are then formally verified using a proposed analysis procedure.

A constituição de sistemas híbridos como alternativa ao fornecimento de energia da concessionária, gerando energia própria e operando de forma isolada ou interconectada ao sistema de distribuição, tem originado estudos e implementações em nível industrial, comercial e mais recentemente residencial. A principal discussão que surge são as análises das vantagens técnicas e econômicas pela opção desse tipo de instalação. Neste trabalho, é apresentado um estudo complementar às pesquisas realizadas, onde é projetado um sistema híbrido contendo aerogeradores, painéis fotovoltaicos, processo de eletrólise, célula a combustível, microturbina a gás e geradores diesel. Esse sistema é simulado e comparado técnica e economicamente a um sistema que contém apenas geradores diesel. O sistema híbrido proposto possui uma microrrede conectada a um típico sistema de distribuição mas com um limite de demanda contratada que impede a satisfação de todas as necessidades energéticas da instalação apenas com a energia da concessionária. Procura-se avaliar os impactos técnicos e econômicos do atendimento da demanda por eletricidade através deste sistema híbrido além de executar-se a otimização, via PSO, do dimensionamento deste sistema, que utiliza uma ordem de despacho para gerenciar as mini unidades geradoras de energia. Foi utilizado o software TRNSYS devido a sua característica de permitir estimar a potência e energia produzidas no intervalo de um ano com detalhamento horário de cada recurso, considerando estimativas reais e localizadas para a disponibilidade dos recursos eólicos e fotovoltaicos. / The designing of hybrid systems as an alternative to power supply from power utility, generating their own energy in operating islanded or grid-tie to the power utility, has resulted in studies and implementations in industrial, commercial and residential level recently. The main discussion that arises is the analysis of the technical and economical advantages for this type of solution. This work presents a complementary study to the researches conducted nowadays, which is designed a hybrid system containing wind turbines, photovoltaic panels, electrolysis process, fuel cell, gas micro turbine and diesel generators. This system was simulated and was compared technically and economically to a system with only diesel gensets. The proposed hybrid system has a microrrede connected to a typical distribution system with a limited power demand value that prevents the satisfaction of all energy needs of the installation only with the utility power. This study evaluates the technical and economical impacts to meeting electric power consumption through this hybrid system and optimize using PSO, the design of this system that uses a dispatch order to manage the mini power generation units. The TRNSYS software was used due to its feature of allowing estimate the electric power and electric energy produced in one year apart with hourly details of each feature, considering actual estimates and localized availability of wind and photovoltaic resources.

Les systèmes cyber-physiques sont une classe de systèmes complexe, de grande échelle, souvent critiques de sûreté, qui apparaissent dans des applications industrielles variées. Des approches de vérification formelle sont capable de fournir des garanties pour la performance et la sûreté de ces systèmes. Elles nécessitent trois éléments : un modèle formel, une méthode de vérification, ainsi qu’un ensemble de spécifications formelles. En revanche, les modèles industriels sont typiquement informels, ils sont analysés dans des environnements de simulation informels et leurs spécifications sont décrits dans un langage naturel informel. Dans cette thèse, nous visons à faciliter l’intégration de la vérification formelle dans le processus industriel de la conception basé sur modèle.Notre première contribution clé est une méthodologie de transformation de modèle. A partir d’un modèle de simulation standard, nous le transformons en un modèle de vérification équivalent, plus précisément en un réseau d’automates hybrides. Le processus de transformation prend en compte des différences de syntaxes, sémantique et d’autres aspects de la modélisation. Pour cette classe de modèle formel, des algorithmes d’atteignabilité peuvent être appliqués pour vérifier des propriétés de sûreté. Un obstacle est que des algorithmes d’atteignabilité se mettent à l’échelle pour des modèles affines par morceaux, mais pas pour des modèles non linéaires. Pour obtenir des surapproximations affines par morceaux des dynamiques non linéaires, nous proposons une technique compositionnelle d’hybridisation syntaxique. Le résultat est un modèle très compact qui retient la structure modulaire du modèle d’origine de simulation, tout en évitant une explosion du nombre de partitions.La seconde contribution clé est une approche pour encoder des spécifications formelles riches de façon à ce qu’elles peuvent être interprétées par des outils d’atteignabilité. Nous prenons en compte des spécifications exprimées sous forme d’un gabarit de motif (pattern template), puisqu’elles sont proche au langage naturel et peuvent être compris facilement par des utilisateurs non experts. Nous fournissons (i) des définitions formelles pour des motifs choisis, qui respectent la sémantique des automates hybrides, et (ii) des observateurs qui encodes les propriétés en tant qu’atteignabilité d’un état d’erreur. En composant ces observateurs avec le modèle formel, les propriétés peuvent être vérifiées par des outils standards de vérification qui sont automatisés.Finalement, nous présentons une chaîne d’outils semi-automatisée ainsi que des études de cas menées en collaboration avec des partenaires industriels. / Cyber-Physical Systems form a class of complex, large-scale systems of frequently safety-critical nature in various industrial applications. Formal verification approaches can provide performance and safety guarantees for these systems. They require three elements: a formal model, a formal verification method, and a set of formal specifications. However, industrial models are typically non-formal, they are analyzed in non-formal simulation environments, and their specifications are described in non-formal natural language. In this thesis, we aim to facilitate the integration of formal verification into the industrial model-based design process.Our first key contribution is a model transformation methodology. Starting with a standard simulation model, we transform it into an equivalent verification model, particularly a network of hybrid automata. The transformation process addresses differences in syntax, semantics, and other aspects of modeling. For this class of formal models, so-called reachability algorithms can be applied to verify safety properties. An obstacle is that scalable algorithms exist for piecewise affine (PWA) models, but not for nonlinear ones. To obtain PWA over-approximations of nonlinear dynamics, we propose a compositional syntactic hybridization technique. The result is a highly compact model that retains the modular structure of the original simulation model and largely avoids an explosion in the number of partitions.The second key contribution is an approach to encode rich formal specifications so that they can be interpreted by tools for reachability. Herein, we consider specifications expressed by pattern templates since they are close to natural language and can be easily understood by non-expert users. We provide (i) formal definitions for select patterns that respect the semantics of hybrid automata, and (ii) monitors which encode the properties as the reachability of an error state. By composing these monitors with the formal model under study, the properties can be checked by off-the-shelf fully automated verification tools.Furthermore, we provide a semi-automated toolchain and present results from case studies conducted in collaboration with industrial partners.

Sistemas Supervisórios Híbridos podem ser definidos como sistemas de controle cujos estados são representados por variáveis discretas e contínuas, e cuja dinâmica é determinada em função do tempo e da ocorrência de eventos discretos. O desenvolvimento desta classe de Sistemas Supervisórios pode ser dividido em duas fases. A 1ª Fase consiste na elaboração de um modelo protótipo para o Sistema Supervisório, que é descrito usando um formalismo, e que é validado com base nas especificações do problema. Na 2ª Fase, este modelo, já validado, é convertido na linguagem de programação do Sistema Supervisório propriamente dito. Esta tese concentra-se na 1ª Fase, para qual abordam-se três questões principais: (1) a escolha do formalismo de modelagem; (2) como construir o modelo do Sistema Supervisório Híbrido usando este formalismo; e (3) como validar o Sistema Supervisório Híbrido usando o modelo construído. Para questão (1), introduz-se um novo formalismo de modelagem baseado na aplicação dos conceitos de Orientação a Objetos (OO) às redes Predicado Transição Diferenciais (redes PTD). Este novo formalismo é chamado de redes PTD-OO. No que se refere a questão (2), é proposto um procedimento para obtenção do modelo do Sistema Supervisório em redes PTD-OO usando os diagramas da UML (‘Unified Modeling Language’). Finalmente, para a questão (3), o problema de validação é abordado através da definição de um conjunto de propriedades que o modelo em redes PTD-OO deve respeitar afim de que sejam garantidos os requisitos do Sistema Supervisório. Estas propriedades são, então, verificadas através de um procedimento proposto para análise de redes PTD-OO. / Hybrid Supervisory Systems can be described as control systems with states that are represented by both discrete and continuous variables. Their dynamics are function of time and depend also on the occurrence of discrete events. The development of Hybrid Supervisory Systems can be divided in two phases. In the 1st Phase, a prototype-model for the Supervisory System is described using a specific formalism and is validated based on the system requirements. In the 2nd Phase, this validated model is converted to the programming language of the Supervisory System. This thesis is focused on the 1st Phase of Hybrid Supervisory System development. It approaches three main issues: (1) the choice of the modelling formalism; (2) how to build the Hybrid Supervisory System model using this formalism; and (3) how to validate the Hybrid Supervisory System using this model. For issue (1), a new modelling formalism is introduced based on Differential Predicate Transition nets (DPT nets) and object-oriented (OO) paradigm. This new formalism is called DPT-OO net. Then, for the issue (2), a modelling procedure that assists the building of the DPT-OO net model using Unified Modelling Language (UML) diagrams is proposed. Finally, for the issue (3), the validation problem is approached by defining a set of properties of the DPT-OO net model that assures the Supervisory System requirements. These properties are then formally verified using a proposed analysis procedure.

At present many remote and Island communities rely solely on diesel powered generators to provide electricity. Diesel fuel is both expensive and polluting and the constant speed operation of the diesel engine is inefficient. In this thesis the use of renewable energy sources to help offset diesel fuel usage and an alternative way of running the diesel generator with the aim of reducing electrical energy costs is investigated. Diesel generators have to be sized to meet peak demand, in one or two diesel generator island grids, these generators will be running at a fraction of maximum output for most of the time. A new variable speed diesel generator allows for a reduction in fuel consumption at part load compared to constant speed operation. Combining the variable speed diesel generator with renewable generation should maximise the diesel fuel offsetting of the renewable source due to the increased efficiency at low loads. The stability issues of maintaining transient performance in a renewable variable speed hybrid system have been modelled and simulated. A control strategy has been developed and the use of energy storage as a buffer for any remaining stability problems has been explored. The control strategy has then been experimentally tested along with one of the possible energy storage solutions. An economic feasibility study has been performed on a case study community to validate the main aim of this research of reducing the cost of electrical energy in diesel generator grids.