Este trabalho descreve a utilização da Rede de Petri como ferramenta de análise e desenvolvimento da automação de uma Micro-usina de cogeração piloto de 130 kW. O projeto foi implantado no centro laboratorial de qualidade de energia da Escola Politécnica da Universidade de São Paulo. O objetivo principal desta Micro-usina é estudar as principais variáveis inerentes à qualidade de energia e funcionalidades destes tipos de sistemas automatizados. A utilização da Rede de Petri (RP) permitiu prever a alcançabilidade, vivacidade, segurança e reversibilidade do programa aplicativo desenvolvido e implantado em um controlador programável (CLP) de última geração. Através de uma rede de comunicação de protocolo aberto foi possível a troca de informações entre o CLP e os módulos de controle.dos geradores (G1 e G2). Entradas e saídas digitais foram utilizadas para monitorar e comandar as chaves de transferência automática (Close e Open Transition) e também os disjuntores motorizados. As operações realizadas são sinalizadas no painel local de controle e transferência (PCT) assim como, via rede Ethernet, na interface remota de supervisão e controle (SCADA).No estudo de caso da Micro-usina de cogeração foram identificadas um total de 24 posições (Position) distintas, considerando as quatro fontes de geração atuais e os dois centros de consumo de energia. Através de uma IHM local ou um supervisório remoto (SCADA) é possível a mudança entre as posições (topologia) permitindo realizar as principais manobras de paralelismo momentâneo e transitório dos grupos geradores com a concessionária. No programa aplicativo do CLP foi implementado o intertravamento de segurança para todos os equipamentos comandados, assumindo sempre o desconhecimento, por parte do operador, dos critérios e seqüências de segurança exigidos para execução das transições entre topologias (pior caso). / This study is about the usage of the Petri Net as an analysis and development tool of the automation of a pilot micro plant of 130 kW. The project was carried out in the energy quality laboratory center at the Escola Politécnica de São Paulo. Its main goal was to study the most important variables related to the quality of energy and the functionalities of the automatized system types. By using the Petri Net, it was possible to foresee the attainment, vivacity, reliability and reversibility of the software, developed and installed in a state-of-the-art programmable logical controller (PLC). Through an open protocol communication network, information was exchanged between the PLC and the generators (G1 and G2) control modules. Digital inputs and outputs were used to monitor and switch the automatic transfer keys (Close and Open Transition) and the motor switches. The procedures done were shown on a local panel of control and transfer, as well as on the Ethernet, at a remote supervision and control interface (SCADA). In this case study, 24 different positions were identified, taking into account the four sources of generation at the moment and the two centers of energy consumption. Through local IHM or remote supervision (SCADA), it was possible to switch positions (topology) and perform the main maneuvres of momentary and transitional parallelism from generator groups to concessionary. As to the PLC application program, a security block was set to all commanded devices, assuming that the operator was unaware of the criteria and security steps needed to proceed with transitions in topology (worst case).

Petri nets are a graphical construction with clearly de ned semantics which can model concurrent communicating systems in a formal manner similar to the way that automata theory can model formal language theory(Petri, 1962). As Dr. Carl Petri found the existing automata insu cient or too cumbersome for describing communicating systems others have found Petri Nets to be too cumbersome for e ectively reasoning about sophisticated, real world systems. In some cases these di culties were overcome by extending the theory of Petri Nets. Dr. Kurt Jensen developed the theory of Coloured Petri Nets (Jensen, 1981) for the purpose of generalizing and simplifying complex Petri Net models. This work incorporates Coloured Petri Nets and other theoretical extensions to describe a real world automated steel cutting system. During the course of this investigation the paper will formalize colours in the language of algebras and examine patterns related to timing conditions. / Thesis / Master of Science (MSc) / Petri nets can provide a graphical explanation of computer systems that have sophisticated communications. The graph has a precise mathematical meaning which allows it to be formally analyzed to prove many interesting properites of the net. There have been many extensions of the theory, some of which are incorporated to this model of an automated steel cutting machine. This thesis also presents the idea of colours, or data types, in the language of algebras.

No description available.

Rede de Petri é uma poderosa ferramenta de modelagem gráfica e matemática bastante aplicada no desenvolvimento de projetos de sistemas de eventos discretos. Porém a sua aplicação na análise e interpretação de tais sistemas torna-se inviável por resultar em modelos grandes, com muitos elementos gráficos. Para solucionar tal problema, vários pesquisadores têm concentrado esforços no desenvolvimento de novas extensões e métodos de síntese de rede de Petri, para reduzir o tamanho dos modelos e assim facilitar a sua aplicação e análise de sistemas grandes e complexos. Rede de Petri Virtual é uma nova extensão de rede de Petri que possibilita a modelagem de tais sistemas de forma modular. Cada elemento do sistema é representado por um módulo e a comunicação entre eles é feita através dos nós virtuais. Esse trabalho formaliza a definição de rede de Petri virtual, desenvolve algoritmo e procedimento de junção dos módulos para gerar o modelo final, uma rede de Petri ordinária que representa o sistema completo. / Petri net is a powerful graphical and mathematical modeling tool commonly used to project Discrete Events Systems. The increasing complexity of such systems does not allow the use of Petri net tools due to the large size of the models (many graphical elements), which is difficult to understand and analyze. Due to this fact, researchers have been made efforts to the development of new synthesis methods for Petri nets, in order to reduce the models size and become easier its use and the analysis task of the systems properties. Virtual Petri net is a new kind (extension) of Petri net, combining its best in control and representation of discrete events systems to the best of modular modeling. This king of Petri net allows to build up models of complex systems from the modules that represent its elements, linked by the virtual nodes. The present work formalizes the definition of Virtual Petri Net. Also develops an algorithm to its use in the discrete events systems and presents a procedure to link and assemble the modules in the whole model. The modular modeling makes easier the understanding and graphical visualization of the system, keeping the final model the same features of the common Petri nets.

This thesis proposes an approach for automatic code generation from a Colored Petri net specification. Two tools were developed for the aforementioned purpose, a Colored Petri net editor to create and modify Colored Petri nets, and an automatic code generator to generate code from a Colored Petri net specification. Through the use of the editor four models were created, these models were used as input to the automatic code generator. The automatic code generator successfully generated code from the Colored Petri net specification, code in the form of component scripts for the Unity3D game engine. However, the approach used by the code generator had flaws such as introducing overhead in the generated code, failing to deal with concurrency, and restricting the types of Colored Petri nets which could be used as input. The aforementioned tools could be used in the future to research the benefits and disadvantages of modeling game systems with Colored Petri nets, and automatically generating code from Colored Petri nets.

Rede de Petri é uma poderosa ferramenta de modelagem gráfica e matemática bastante aplicada no desenvolvimento de projetos de sistemas de eventos discretos. Porém a sua aplicação na análise e interpretação de tais sistemas torna-se inviável por resultar em modelos grandes, com muitos elementos gráficos. Para solucionar tal problema, vários pesquisadores têm concentrado esforços no desenvolvimento de novas extensões e métodos de síntese de rede de Petri, para reduzir o tamanho dos modelos e assim facilitar a sua aplicação e análise de sistemas grandes e complexos. Rede de Petri Virtual é uma nova extensão de rede de Petri que possibilita a modelagem de tais sistemas de forma modular. Cada elemento do sistema é representado por um módulo e a comunicação entre eles é feita através dos nós virtuais. Esse trabalho formaliza a definição de rede de Petri virtual, desenvolve algoritmo e procedimento de junção dos módulos para gerar o modelo final, uma rede de Petri ordinária que representa o sistema completo. / Petri net is a powerful graphical and mathematical modeling tool commonly used to project Discrete Events Systems. The increasing complexity of such systems does not allow the use of Petri net tools due to the large size of the models (many graphical elements), which is difficult to understand and analyze. Due to this fact, researchers have been made efforts to the development of new synthesis methods for Petri nets, in order to reduce the models size and become easier its use and the analysis task of the systems properties. Virtual Petri net is a new kind (extension) of Petri net, combining its best in control and representation of discrete events systems to the best of modular modeling. This king of Petri net allows to build up models of complex systems from the modules that represent its elements, linked by the virtual nodes. The present work formalizes the definition of Virtual Petri Net. Also develops an algorithm to its use in the discrete events systems and presents a procedure to link and assemble the modules in the whole model. The modular modeling makes easier the understanding and graphical visualization of the system, keeping the final model the same features of the common Petri nets.

Made available in DSpace on 2016-06-02T19:06:15Z (GMT). No. of bitstreams: 1 6263.pdf: 2838494 bytes, checksum: 852261a244b09c47cc828522a799cc8d (MD5) Previous issue date: 2014-06-26 / Petri Net (PN) is a graphical mathematical tool used to create models that provide a formal specification of systems, creating the possibility of running behavior analysis and property verification. PN models can be used to model several system types, for example, Manufacturing Systems. In general, using PN to model systems with too many characteristics cause the so-called state-space explosion problem, in other words, a great element profusion in the model. In order to mitigate the referred problem researchers developed reduction rules to synthetize models. Reduced models maintain original system properties and can be easily analyzed and simulated. A method to automate reduction rules application is proposed on the present research. A Genetic Algorithm heuristic is responsible for applying six reductions rules on Place-Transition Petri Nets given as input. The proposed algorithm, presented as a Matlab toolbox, may contribute when simulating and running property verification methodologies on Petri Net models. / Rede de Petri (RP) é uma ferramenta de modelagem com rigor matemático usada para especificar e formalizar sistemas e suas características. Modelos de RP podem ser avaliados quanto à seu comportamento dinâmico e suas propriedades estruturais. Diversos tipos de modelos podem ser especificados usando RP s, por exemplo, modelos de Sistemas de Manufatura. De maneira geral, modelos de sistemas complexos sofrem do problema da grande profusão de elementos. Esse problema é um limitante para diversas metodologias de verificação de propriedades e simulação de comportamento dinâmico dos modelos. Frequentemente metodologias baseadas em regras de redução são propostas para superar o problema da grande profusão de elementos. O presente trabalho apresenta uma ferramenta para automatizar a aplicação de regras de redução em modelos de RP. Um conjunto de regras foi selecionado para montar uma base de regras de redução e uma heurística baseada em algoritmos genéticos foi criada para aplicar reduções em modelos de RP Lugar-Transição. Os resultados obtidos mostraram que a ferramenta proposta, apresentada como uma toolbox do Matlab, pode ser utilizada para auxiliar no processo de análise, simulação e verificação de propriedades de sistemas modelados por meio de RP s.

Presently, most spacecraft are controlled from ground involving activities such as up-linking the schedule of daily operations and monitoring health parameters. These activities lead to a cognitive overload on human operators. Imaging/science opportunities are lost, if any discrepancies occur during the execution of pre-planned sequences. Consequently, advanced space exploration systems for future needs demand on-board intelligence and autonomy. This thesis attempts to solve the problem of providing an adequate degree of autonomy in future generation of spacecraft. The autonomous spacecraft accept high-level goals from users and make decisions on-board to generate detailed command schedules satisfying stringent constraints posed by the harsh environment of the space, visibility criteria and scarce on-board resources. They reconfigure themselves in case of any failure and re-plan when needed. Autonomy concepts are derived in the context of complex systems by drawing analogy to living organisms and social organisations. A general autonomy framework may be defined with a six level structure comprising of the following capabilities -reflexes, awareness, self-regulation, self-healing, self-adaptation and self-evolution. A generic and reusable software architecture is proposed using hybrid multi-agent systems, which are arranged in a hierarchical manner using two types of decomposition viz. stratum and layer. The software architecture of the autonomous spacecraft is modeled as a stratified agent with a deliberative stratum, which achieves adaptive behaviour and a reactive stratum, which achieves reactive behaviour. Each individual agent has a generic structure comprising of perception, action, communication and knowledge components. It achieves the specialist capability through model-based reasoning. The knowledge models encompass: Planning knowledge describing higher-level goals, task structure and method of achieving the goals, Control knowledge encompassing the static and dynamic models of the spacecraft and Diagnostic knowledge incorporating the cause-effect relationships. The deliberative stratum is capable of planning in different time horizons and is, in turn, organised into a hierarchical agent system with three layers corresponding to different time horizons. It is composed of a long-term, medium-term and short-term planning agents, focusing on strategic issues, spacecraft level resources and specific spacecraft states respectively. The power of Petri nets is exploited for knowledge modeling as well as for plan representation. The ability of Petri nets to represent causality, concurrency and conflict relations explicitly makes it an excellent tool for representing the planning problem. Hierarchical Timed Petri Net is chosen for our modeling, since it captures the temporal requirements of the real-time spacecraft operations as well as facilitates the modeling of the system with multiple levels of abstraction. The necessary primitives for the plan representation are defined. In hierarchical modeling using Petri nets, refinement is done by a compound (high-level) transition. A compound transition models either a complex activity, which corresponds to high-level operation on spacecraft or a method, which corresponds to the agent capability. At the lowest layer, a transition in the plan represents a primitive command to the spacecraft, such as ‘switch on camera’. The Petri net unfolding technique, which is a partial order approach, is applied to derive the plans from the dynamic knowledge models. This tackles the problem of combinatorial explosion. A hierarchical planning approach is followed, in which the abstract plan is recursively decomposed using the unfolding technique and refined by way of exercising the appropriate decisions in each layer. The reactive stratum is configured with three peer level agents. The control agent executes the command schedule and has the capability for reflex action. Structural properties of Petri nets are exploited by the execution-monitoring agent and the diagnostic agent for system level diagnosis. Fault tree method is applied for fine granularity diagnosis. The resultant architecture is a cost-effective solution, since it permits reusability of knowledge models across similar missions. The knowledge models are formally verified for ensuring the absence of deadlocks, buffer overflows, recoverability and detection of unreachable modules using Petri net properties such as reachability, liveness, boundedness, safeness, reversibility and home state. The high-risk components are subjected to safety property verification, which makes the system rugged. The hierarchical composition of Petri net models (which are independently verified), preserves liveness and boundedness characteristics and thus ensuring the reliability of the integrated models. This, in turn, ensures that reliable plans are generated on-board using these good quality models. The models of the system components viz. partial order plan, conditional plan, dynamic world model, reflex model, resource model and the hierarchical models are developed and demonstrated using HPSIM and Moses Tool Suite, using examples from spacecraft domain. The long-term planning agent, with hierarchical world models, for handling high-level goals is developed and simulated using Moses Tool Suite. The plan generation using unfolding approach is demonstrated using VIPTool, which has the partial order analysis capability. In summary, the main contributions include (a) Definition of a general framework for spacecraft autonomy; (b) design of a generic and reusable architecture for autonomous spacecraft using hybrid multi-agent concepts; (c) unified knowledge representation and reasoning using Petri nets across various strata/layers; (d) application of Petri net unfolding technique in a hierarchical manner for plan generation; (e) use of structural properties of Petri nets for fault identification and location; (f) verification and validation of Petri net models using Petri net properties and (g) simulation and demonstration of the system components viz. partial order plan, conditional plan, dynamic world model, reflex model, resource model and hierarchical models, by developing examples from spacecraft domain, using HPSIM and Moses Tool Suite and demonstration of plan generation using unfolding technique using VIPTool.

Modern software systems have increasingly higher expectations on their reliability, in particular if the systems are critical and real-time. The development of these complex software systems requires strong modelling and analysis methods including quantitative modelling and formal verification. Unified Modelling Language (UML) is a widely used and intuitive graphical modelling language to design complex systems, while formal models provide a theoretical support to verify system design models. However, UML models are not sufficient to guarantee correct system designs and formal models, on the other hand, are often restrictive and complex to use. It is believed that a combined approach comprising the advantages of both models can offer better designs for modern complex software development needs. This thesis focuses on the design and development of a rigorous framework based on Model Driven Development (MDD) that facilitates transformations of non-formal models into formal models for design verification. This thesis defines and describes the transformation from UML2 sequence diagrams to coloured Petri nets and proves syntactic and semantic correctness of the transformation. Additionally, we explore ways of adding information (time, probability, and hierarchy) to a design and how it can be added onto extensions of a target model. Correctness results are extended in this context. The approach in this thesis is novel and significant both in how to establish semantic and syntactic correctness of transformations, and how to explore semantic variability in the target model for formal analysis. Hence, the motivation of this thesis establishes: the UML behavioural models can be validated by correct transformation of them into formal models that can be formally analysed and verified.

Aujourd’hui les réseaux électriques sont exploités dans un marché dérégulé. Les gestionnaires des réseaux électriques sont tenus d’assurer un certain nombre de critères de fiabilité et de continuité du service, tout en minimisant le coût total consacré aux efforts effectués pour maintenir la fiabilité des installations. Il s’agit de trouver une stratégie, qui répond à plusieurs exigences, comme : le coût, les performances, la législation, les exigences du régulateur, etc. Cependant, le processus de prise de décision est subjectif, car chaque participant ramène sa contribution sur base de sa propre expérience. Bien que ce processus permette de trouver la « meilleure » stratégie, cette dernière n’est pas forcément la stratégie « optimale ». Ce compromis technico-économique a sensibilisé les gestionnaires des réseaux électriques à la nécessité d’un recours à des outils d’aide à la décision, qui doivent se baser sur des nouvelles approches quantitatives et une modélisation plus proches de la réalité physique. Cette thèse rentre dans le cadre d’un projet de recherche lancé par ELIA, et dénommé COMPRIMa (Cost-Optimization Models for the Planning of the Renewal, Inspection, and Maintenance of Belgian power system facilities). Ce projet vise à développer une méthodologie qui permet de modéliser une partie du réseau électrique de transport (par les réseaux de Petri stochastiques) et de simuler son comportement dynamique sur un horizon donné (simulation de Monte Carlo). L’évaluation des indices de fiabilité permet de comparer les différents scénarios qui tentent d’améliorer les performances de l’installation. L’approche proposée est basée sur la stratégie RCM (Reliability-Centered Maintenance). La méthodologie développée dans cette thèse permet une modélisation plus réaliste du réseau qui tient compte, entre autres, des aspects suivants : - La corrélation quantitative entre le processus de maintenance et le processus de vieillissement des composants (par un modèle d’âge virtuel) ; - Les dépendances liées à l’aspect multi-composant du système, qui tient compte des modes de défaillance spécifiques des systèmes de protection ; - L’aspect économique lié à la stratégie de maintenance (inspection, entretien, réparation, remplacement), aux coupures (programmées et forcées) et aux événements à risque (refus disjoncteur, perte d’un client, perte d’un jeu de barres, perte d’une sous-station, etc.).