475 research outputs found

    Extracting Petri Modules From Large and Legacy Petri Net Models

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    Petri nets, even though very useful for modeling of discrete event systems, suffer from some weaknesses such as huge size, huge state space, and slow in simulation. Due to the huge state space, model checking a Petri net is difficult. Also, due to the slowness in simulation, discrete-timed Petri nets cannot be used for real-time applications. Thus, modular Petri nets are suggested as a way of overcoming these difficulties. In modular Petri nets, modules are designed, developed, and run independently, and the modules communicate with each other via inter-modular connectors. This approach is suggested for developing newer Petri net models. However, there exists a large number of Petri net models of real-life systems, and these legacy models are enormous and non-modular. And, these models cannot be discarded as large amounts of time and money were spent to develop these models. This paper presents a unique algorithm for extracting modules from large and legacy Petri net models. The algorithm extracts modules (known as “Petri modules”) that are well-defined for inter-modular collaboration. Also, the extraction method preserves the structural properties. The goal of the paper is to introduce a methodology by which Petri nets can be moved to a new level in which a modular Petri net model can be made of Petri modules. The Petri modules are independent and can be hosted on different computers. These modules communicate via inter-modular components such as TCP/IP sockets. Since Petri modules are compact, also run faster, thus become suitable for supervisory control of real-time systems.publishedVersio

    Ninth Workshop and Tutorial on Practical Use of Coloured Petri Nets and the CPN Tools, Aarhus, Denmark, October 20-22, 2008

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    This booklet contains the proceedings of the Ninth Workshop on Practical Use of Coloured Petri Nets and the CPN Tools, October 20-22, 2008. The workshop is organised by the CPN group at the Department of Computer Science, University of Aarhus, Denmark. The papers are also available in electronic form via the web pages: http://www.daimi.au.dk/CPnets/workshop0

    Proceedings of the 5th International Workshop on Reconfigurable Communication-centric Systems on Chip 2010 - ReCoSoC\u2710 - May 17-19, 2010 Karlsruhe, Germany. (KIT Scientific Reports ; 7551)

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    ReCoSoC is intended to be a periodic annual meeting to expose and discuss gathered expertise as well as state of the art research around SoC related topics through plenary invited papers and posters. The workshop aims to provide a prospective view of tomorrow\u27s challenges in the multibillion transistor era, taking into account the emerging techniques and architectures exploring the synergy between flexible on-chip communication and system reconfigurability

    Distributed systems : architecture-driven specification using extended LOTOS

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    The thesis uses the LOTOS language (ISO International Standard ISO 8807) as a basis for the formal specification of distributed systems. Contributions are made to two key research areas: architecture-driven specification and LOTOS language extensions. The notion of architecture-driven specification is to guide the specification process by providing a reference-base of pre-defined domain-specific components. The thesis builds an infra-structure of architectural elements, and provides Extended LOTOS (XL) definitions of these elements. The thesis develops Extended LOTOS (XI.) for the specification of distributed systems. XL- is LOTOS enhanced with features for the formal specification of quantitative timing. probabilistic and priority requirements. For distributed systems, the specification of these ‘performance’ requirements, ran be as important as the specification of the associated functional requirements. To support quantitative timing features, the XL semantics define a global, discrete clock which can be used both to force events to occur at specific times, and to measure Intervals between event occurrences. XL introduces time policy operators ASAP (as soon as possible’ corresponding to “maximal progress semantics") and ALAP (late as possible'). Special internal transitions are introduced in XL semantics for the specification of probability, Conformance relations based on a notion of probabilization, together with a testing framework, are defined to support reasoning about probabilistic XL specifications. Priority within the XL semantics ensures that permitted events with the highest priority weighting of their class are allowed first. Both functional and performance specification play important roles in CIM (Computer Integrated Manufacturing) systems. The thesis uses a CIM system known as the CIM- OSA lntegrating Infrastructure as a case study of architecture-driven specification using XL. The thesis thus constitutes a step in the evolution of distributed system specification methods that have both an architectural basis and a formal basis

    Actor based behavioural simulation as an aid for organisational decision making

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    Decision-making is a critical activity for most of the modern organizations to stay competitive in rapidly changing business environment. Effective organisational decision-making requires deep understanding of various organisational aspects such as its goals, structure, business-as-usual operational processes, environment where it operates, and inherent characteristics of the change drivers that may impact the organisation. The size of a modern organisation, its socio-technical characteristics, inherent uncertainty, volatile operating environment, and prohibitively high cost of the incorrect decisions make decision-making a challenging endeavor. While the enterprise modelling and simulation technologies have evolved into a mature discipline for understanding a range of engineering, defense and control systems, their application in organisational decision-making is considerably low. Current organisational decision-making approaches that are prevalent in practice are largely qualitative. Moreover, they mostly rely on human experts who are often aided with the primitive technologies such as spreadsheets and visual diagrams. This thesis argues that the existing modelling and simulation technologies are neither suitable to represent organisation and decision artifacts in a comprehensive and machine-interpretable form nor do they comprehensively address the analysis needs. An approach that advances the modelling abstraction and analysis machinery for organisational decision-making is proposed. In particular, this thesis proposes a domain specific language to represent relevant aspects of an organisation for decision-making, establishes the relevance of a bottom-up simulation technique as a means for analysis, and introduces a method to utilise the proposed modelling abstraction, analysis technique, and analysis machinery in an effective and convenient manner

    Factories of the Future

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    Engineering; Industrial engineering; Production engineerin

    Coalition based approach for shop floor agility – a multiagent approach

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    Dissertation submitted for a PhD degree in Electrical Engineering, speciality of Robotics and Integrated Manufacturing from the Universidade Nova de Lisboa, Faculdade de Ciências e TecnologiaThis thesis addresses the problem of shop floor agility. In order to cope with the disturbances and uncertainties that characterise the current business scenarios faced by manufacturing companies, the capability of their shop floors needs to be improved quickly, such that these shop floors may be adapted, changed or become easily modifiable (shop floor reengineering). One of the critical elements in any shop floor reengineering process is the way the control/supervision architecture is changed or modified to accommodate for the new processes and equipment. This thesis, therefore, proposes an architecture to support the fast adaptation or changes in the control/supervision architecture. This architecture postulates that manufacturing systems are no more than compositions of modularised manufacturing components whose interactions when aggregated are governed by contractual mechanisms that favour configuration over reprogramming. A multiagent based reference architecture called Coalition Based Approach for Shop floor Agility – CoBASA, was created to support fast adaptation and changes of shop floor control architectures with minimal effort. The coalitions are composed of agentified manufacturing components (modules), whose relationships within the coalitions are governed by contracts that are configured whenever a coalition is established. Creating and changing a coalition do not involve programming effort because it only requires changes to the contract that regulates it

    Error Detection and Diagnosis for System-on-Chip in Space Applications

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    Tesis por compendio de publicacionesLos componentes electrónicos comerciales, comúnmente llamados componentes Commercial-Off-The-Shelf (COTS) están presentes en multitud de dispositivos habituales en nuestro día a día. Particularmente, el uso de microprocesadores y sistemas en chip (SoC) altamente integrados ha favorecido la aparición de dispositivos electrónicos cada vez más inteligentes que sostienen el estilo de vida y el avance de la sociedad moderna. Su uso se ha generalizado incluso en aquellos sistemas que se consideran críticos para la seguridad, como vehículos, aviones, armamento, dispositivos médicos, implantes o centrales eléctricas. En cualquiera de ellos, un fallo podría tener graves consecuencias humanas o económicas. Sin embargo, todos los sistemas electrónicos conviven constantemente con factores internos y externos que pueden provocar fallos en su funcionamiento. La capacidad de un sistema para funcionar correctamente en presencia de fallos se denomina tolerancia a fallos, y es un requisito en el diseño y operación de sistemas críticos. Los vehículos espaciales como satélites o naves espaciales también hacen uso de microprocesadores para operar de forma autónoma o semi autónoma durante su vida útil, con la dificultad añadida de que no pueden ser reparados en órbita, por lo que se consideran sistemas críticos. Además, las duras condiciones existentes en el espacio, y en particular los efectos de la radiación, suponen un gran desafío para el correcto funcionamiento de los dispositivos electrónicos. Concretamente, los fallos transitorios provocados por radiación (conocidos como soft errors) tienen el potencial de ser una de las mayores amenazas para la fiabilidad de un sistema en el espacio. Las misiones espaciales de gran envergadura, típicamente financiadas públicamente como en el caso de la NASA o la Agencia Espacial Europea (ESA), han tenido históricamente como requisito evitar el riesgo a toda costa por encima de cualquier restricción de coste o plazo. Por ello, la selección de componentes resistentes a la radiación (rad-hard) específicamente diseñados para su uso en el espacio ha sido la metodología imperante en el paradigma que hoy podemos denominar industria espacial tradicional, u Old Space. Sin embargo, los componentes rad-hard tienen habitualmente un coste mucho más alto y unas prestaciones mucho menores que otros componentes COTS equivalentes. De hecho, los componentes COTS ya han sido utilizados satisfactoriamente en misiones de la NASA o la ESA cuando las prestaciones requeridas por la misión no podían ser cubiertas por ningún componente rad-hard existente. En los últimos años, el acceso al espacio se está facilitando debido en gran parte a la entrada de empresas privadas en la industria espacial. Estas empresas no siempre buscan evitar el riesgo a toda costa, sino que deben perseguir una rentabilidad económica, por lo que hacen un balance entre riesgo, coste y plazo mediante gestión del riesgo en un paradigma denominado Nuevo Espacio o New Space. Estas empresas a menudo están interesadas en entregar servicios basados en el espacio con las máximas prestaciones y el mayor beneficio posibles, para lo cual los componentes rad-hard son menos atractivos debido a su mayor coste y menores prestaciones que los componentes COTS existentes. Sin embargo, los componentes COTS no han sido específicamente diseñados para su uso en el espacio y típicamente no incluyen técnicas específicas para evitar que los efectos de la radiación afecten su funcionamiento. Los componentes COTS se comercializan tal cual son, y habitualmente no es posible modificarlos para mejorar su resistencia a la radiación. Además, los elevados niveles de integración de los sistemas en chip (SoC) complejos de altas prestaciones dificultan su observación y la aplicación de técnicas de tolerancia a fallos. Este problema es especialmente relevante en el caso de los microprocesadores. Por tanto, existe un gran interés en el desarrollo de técnicas que permitan conocer y mejorar el comportamiento de los microprocesadores COTS bajo radiación sin modificar su arquitectura y sin interferir en su funcionamiento para facilitar su uso en el espacio y con ello maximizar las prestaciones de las misiones espaciales presentes y futuras. En esta Tesis se han desarrollado técnicas novedosas para detectar, diagnosticar y mitigar los errores producidos por radiación en microprocesadores y sistemas en chip (SoC) comerciales, utilizando la interfaz de traza como punto de observación. La interfaz de traza es un recurso habitual en los microprocesadores modernos, principalmente enfocado a soportar las tareas de desarrollo y depuración del software durante la fase de diseño. Sin embargo, una vez el desarrollo ha concluido, la interfaz de traza típicamente no se utiliza durante la fase operativa del sistema, por lo que puede ser reutilizada sin coste. La interfaz de traza constituye un punto de conexión viable para observar el comportamiento de un microprocesador de forma no intrusiva y sin interferir en su funcionamiento. Como resultado de esta Tesis se ha desarrollado un módulo IP capaz de recabar y decodificar la información de traza de un microprocesador COTS moderno de altas prestaciones. El IP es altamente configurable y personalizable para adaptarse a diferentes aplicaciones y tipos de procesadores. Ha sido diseñado y validado utilizando el dispositivo Zynq-7000 de Xilinx como plataforma de desarrollo, que constituye un dispositivo COTS de interés en la industria espacial. Este dispositivo incluye un procesador ARM Cortex-A9 de doble núcleo, que es representativo del conjunto de microprocesadores hard-core modernos de altas prestaciones. El IP resultante es compatible con la tecnología ARM CoreSight, que proporciona acceso a información de traza en los microprocesadores ARM. El IP incorpora técnicas para detectar errores en el flujo de ejecución y en los datos de la aplicación ejecutada utilizando la información de traza, en tiempo real y con muy baja latencia. El IP se ha validado en campañas de inyección de fallos y también en radiación con protones y neutrones en instalaciones especializadas. También se ha combinado con otras técnicas de tolerancia a fallos para construir técnicas híbridas de mitigación de errores. Los resultados experimentales obtenidos demuestran su alta capacidad de detección y potencialidad en el diagnóstico de errores producidos por radiación. El resultado de esta Tesis, desarrollada en el marco de un Doctorado Industrial entre la Universidad Carlos III de Madrid (UC3M) y la empresa Arquimea, se ha transferido satisfactoriamente al entorno empresarial en forma de un proyecto financiado por la Agencia Espacial Europea para continuar su desarrollo y posterior explotación.Commercial electronic components, also known as Commercial-Off-The-Shelf (COTS), are present in a wide variety of devices commonly used in our daily life. Particularly, the use of microprocessors and highly integrated System-on-Chip (SoC) devices has fostered the advent of increasingly intelligent electronic devices which sustain the lifestyles and the progress of modern society. Microprocessors are present even in safety-critical systems, such as vehicles, planes, weapons, medical devices, implants, or power plants. In any of these cases, a fault could involve severe human or economic consequences. However, every electronic system deals continuously with internal and external factors that could provoke faults in its operation. The capacity of a system to operate correctly in presence of faults is known as fault-tolerance, and it becomes a requirement in the design and operation of critical systems. Space vehicles such as satellites or spacecraft also incorporate microprocessors to operate autonomously or semi-autonomously during their service life, with the additional difficulty that they cannot be repaired once in-orbit, so they are considered critical systems. In addition, the harsh conditions in space, and specifically radiation effects, involve a big challenge for the correct operation of electronic devices. In particular, radiation-induced soft errors have the potential to become one of the major risks for the reliability of systems in space. Large space missions, typically publicly funded as in the case of NASA or European Space Agency (ESA), have followed historically the requirement to avoid the risk at any expense, regardless of any cost or schedule restriction. Because of that, the selection of radiation-resistant components (known as rad-hard) specifically designed to be used in space has been the dominant methodology in the paradigm of traditional space industry, also known as “Old Space”. However, rad-hard components have commonly a much higher associated cost and much lower performance that other equivalent COTS devices. In fact, COTS components have already been used successfully by NASA and ESA in missions that requested such high performance that could not be satisfied by any available rad-hard component. In the recent years, the access to space is being facilitated in part due to the irruption of private companies in the space industry. Such companies do not always seek to avoid the risk at any cost, but they must pursue profitability, so they perform a trade-off between risk, cost, and schedule through risk management in a paradigm known as “New Space”. Private companies are often interested in deliver space-based services with the maximum performance and maximum benefit as possible. With such objective, rad-hard components are less attractive than COTS due to their higher cost and lower performance. However, COTS components have not been specifically designed to be used in space and typically they do not include specific techniques to avoid or mitigate the radiation effects in their operation. COTS components are commercialized “as is”, so it is not possible to modify them to improve their susceptibility to radiation effects. Moreover, the high levels of integration of complex, high-performance SoC devices hinder their observability and the application of fault-tolerance techniques. This problem is especially relevant in the case of microprocessors. Thus, there is a growing interest in the development of techniques allowing to understand and improve the behavior of COTS microprocessors under radiation without modifying their architecture and without interfering with their operation. Such techniques may facilitate the use of COTS components in space and maximize the performance of present and future space missions. In this Thesis, novel techniques have been developed to detect, diagnose, and mitigate radiation-induced errors in COTS microprocessors and SoCs using the trace interface as an observation point. The trace interface is a resource commonly found in modern microprocessors, mainly intended to support software development and debugging activities during the design phase. However, it is commonly left unused during the operational phase of the system, so it can be reused with no cost. The trace interface constitutes a feasible connection point to observe microprocessor behavior in a non-intrusive manner and without disturbing processor operation. As a result of this Thesis, an IP module has been developed capable to gather and decode the trace information of a modern, high-end, COTS microprocessor. The IP is highly configurable and customizable to support different applications and processor types. The IP has been designed and validated using the Xilinx Zynq-7000 device as a development platform, which is an interesting COTS device for the space industry. This device features a dual-core ARM Cortex-A9 processor, which is a good representative of modern, high-end, hard-core microprocessors. The resulting IP is compatible with the ARM CoreSight technology, which enables access to trace information in ARM microprocessors. The IP is able to detect errors in the execution flow of the microprocessor and in the application data using trace information, in real time and with very low latency. The IP has been validated in fault injection campaigns and also under proton and neutron irradiation campaigns in specialized facilities. It has also been combined with other fault-tolerance techniques to build hybrid error mitigation approaches. Experimental results demonstrate its high detection capabilities and high potential for the diagnosis of radiation-induced errors. The result of this Thesis, developed in the framework of an Industrial Ph.D. between the University Carlos III of Madrid (UC3M) and the company Arquimea, has been successfully transferred to the company business as a project sponsored by European Space Agency to continue its development and subsequent commercialization.Programa de Doctorado en Ingeniería Eléctrica, Electrónica y Automática por la Universidad Carlos III de MadridPresidenta: María Luisa López Vallejo.- Secretario: Enrique San Millán Heredia.- Vocal: Luigi Di Lill
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