Heuristics for Periodic Scheduling

V posledních několika desetiletích se masivně zvýšilo využívání elektronických komunikačních systémů, které ovlivňují všechny oblasti lidské činnosti. Díky nízkým nákladům a vysoké efektivitě mohou být tyto modely široce rozšířené. Masivní využívání takových systémů v různých doménách jako je průmysl, chytrá města (smart cities), atd., volá po vývoji rozvrhovacích metod, které jsou rychlé, přizpůsobivé a spolehlivé. V této práci formalizujeme problém vysoce kritického periodického rozvrhování. Dále navrhujeme aplikaci v Javě, která umožnuje jednoduché testování různých rozvrhovacích metod. Hlavní přínos této práce spočívá v několika heuristikách vhodných pro striktně periodické rozvrhování komunikace a porovnání jejich výkonnosti na vygenerovaných instancích.In the past decades, the usage of electronic communication systems that influence all areas of human activities massively increased. Low cost and high effectiveness allow it to be used widely. The massive usage of such systems in different domains such as industry, smart cities, etc. calls for developing scheduling methods that are fast, adjustable and reliable. In this thesis, we formalize the highly critical periodic scheduling problem and design a Java-based framework that allows easy testing of different scheduling methods. The main contribution of this thesis is several heuristics suitable for strictly periodic network communication and comparison of their performance on generated instances

Time-Sensitive Networking for Industrial Automation: Challenges, Opportunities, and Directions

With the introduction of Cyber-Physical Systems (CPS) and Internet of Things (IoT) into industrial applications, industrial automation is undergoing tremendous change, especially with regard to improving efficiency and reducing the cost of products. Industrial automation applications are often required to transmit time- and safety-critical data to monitor and control industrial processes, especially for critical control systems. There are a number of solutions to meet these requirements (e.g., priority-based real-time schedules and closed-loop feedback control systems). However, due to their different processing capabilities (e.g., in the end devices and network switches), different vendors may come out with distinct solutions, and this makes the large-scale integration of devices from different vendors difficult or impossible. IEEE 802.1 Time-Sensitive Networking (TSN) is a standardization group formed to enhance and optimize the IEEE 802.1 network standards, especially for Ethernet-based networks. These solutions can be evolved and adapted into a cross-industry scenario, such as a large-scale distributed industrial plant, which requires multiple industrial entities working collaboratively. This paper provides a comprehensive review on the current advances in TSN standards for industrial automation. We present the state-of-the-art IEEE TSN standards and discuss the opportunities and challenges when integrating each protocol into the industry domains. Finally, we discuss some promising research about applying the TSN technology to industrial automation applications

Kommunikation und Bildverarbeitung in der Automation

In diesem Open-Access-Tagungsband sind die besten Beiträge des 9. Jahreskolloquiums "Kommunikation in der Automation" (KommA 2018) und des 6. Jahreskolloquiums "Bildverarbeitung in der Automation" (BVAu 2018) enthalten. Die Kolloquien fanden am 20. und 21. November 2018 in der SmartFactoryOWL, einer gemeinsamen Einrichtung des Fraunhofer IOSB-INA und der Technischen Hochschule Ostwestfalen-Lippe statt. Die vorgestellten neuesten Forschungsergebnisse auf den Gebieten der industriellen Kommunikationstechnik und Bildverarbeitung erweitern den aktuellen Stand der Forschung und Technik. Die in den Beiträgen enthaltenen anschaulichen Beispiele aus dem Bereich der Automation setzen die Ergebnisse in den direkten Anwendungsbezug

A Diagnostics Model for Industrial Communications Networks

Over the past twenty years industrial communications networks have become common place in most industrial plants. The high availability of these networks is crucial in smooth plant operations. Therefore local and remote diagnostics of these networks is of primary importance in solving any existing or emerging network problems. Users for most part consider the “plant networks” as black boxes, and often not sure of the actual health of the networks. The major part of the work outlined in this research concentrates on the proposed “Network Diagnostics Model” for local and remote monitoring. The main objective of the research is to aid the establishment of tools and techniques for diagnosis of the industrial networks, with particular emphasis on PROFIBUS and PROFINET. Additionally this research has resulted in development of a number of devices to aid in network diagnostics. The work outlined in this submission contributes to the developments in the area of online diagnostics systems. The development work was conducted in the following phases: 1. Development of Function Block (FB) for diagnosing PROFIBUS network for implementation on PLC. 2. Development of OPC server for diagnosing PROFIBUS network for implementation on PC. 3. Development of a web based diagnostic software for multiple fieldbuses for implementation on imbedded XP platform. 4. Development of OPC server for diagnosing PROFINET network for implementation on PC 5. Conformance testing of masters (PLC) in PROFIBUS network to increase the health of the network. 6. Use of diagnostics tools for performance analysis of fieldbuses networks for high performance applications. The research work outlined in this submission has made a significant and coherent contribution to online diagnostics of fieldbus communications networks, and has paved the way for the introduction of the online diagnostics devices to the market place. It has shown that the proposed model provides a uniform framework for research and development of diagnostics tools and techniques for fieldbus networks. Organizations that use fieldbus should consider installing advanced online diagnostic systems to boost maintenance efficiency and reduce operating costs, and maintain the availability of plant resources. Based on the experience gained over a number of years a multilayer model is proposed for future development of diagnostics tools

Redes de sensores

Desafortunadamente no hay un único estándar de comunicación para redes de sensores/actuadores, sin embargo, no hay otra opción para la conectividad con el ordenador, que no sea Ethernet, junto con los protocolos de Internet, que es reconocida actualmente como la solución universal. Así los sistemas de Bus de Campo, Ethernet Industrial, y las recientes Redes Inalámbricas aplicadas en estos ámbitos, marcan el camino recorrido hasta hoy. Se demuestra que existió continuidad y escalabilidad en el desarrollo de estas tres generaciones de sistemas de comunicación industrial, y que se intenta garantizar la compatibilidad con versiones anteriores a expensas de una innovación más profunda. Gracias a las modernas tecnologías de comunicaciones, se van modificando las arquitecturas de las redes de automatización, llegando hasta las actuales arquitecturas híbridas que combinan cable y redes inalámbricas. En este trabajo, tras una visión general de los actuales sistemas de comunicación industriales, aplicados a nivel de sensores y actuadores, se analizará el estado del arte de estas redes de comunicación en aplicaciones industriales. También se presentarán sus problemáticas más comunes, y los enfoques mejor considerados en la actualidad, para resolverlos. Cabe aclarar que se profundizara mas el análisis a nivel eléctrico de los sistemas de transmisión serie, sobre buses RS 232, 422 y 485, ya que son estos los masivamente más utilizados en la actualidad, y parte de las problemáticas que ellos presentan, se proyectan también sobre Profibus y otros sistemas más modernos.Facultad de Informátic

Redes de sensores

Desafortunadamente no hay un único estándar de comunicación para redes de sensores/actuadores, sin embargo, no hay otra opción para la conectividad con el ordenador, que no sea Ethernet, junto con los protocolos de Internet, que es reconocida actualmente como la solución universal. Así los sistemas de Bus de Campo, Ethernet Industrial, y las recientes Redes Inalámbricas aplicadas en estos ámbitos, marcan el camino recorrido hasta hoy. Se demuestra que existió continuidad y escalabilidad en el desarrollo de estas tres generaciones de sistemas de comunicación industrial, y que se intenta garantizar la compatibilidad con versiones anteriores a expensas de una innovación más profunda. Gracias a las modernas tecnologías de comunicaciones, se van modificando las arquitecturas de las redes de automatización, llegando hasta las actuales arquitecturas híbridas que combinan cable y redes inalámbricas. En este trabajo, tras una visión general de los actuales sistemas de comunicación industriales, aplicados a nivel de sensores y actuadores, se analizará el estado del arte de estas redes de comunicación en aplicaciones industriales. También se presentarán sus problemáticas más comunes, y los enfoques mejor considerados en la actualidad, para resolverlos. Cabe aclarar que se profundizara mas el análisis a nivel eléctrico de los sistemas de transmisión serie, sobre buses RS 232, 422 y 485, ya que son estos los masivamente más utilizados en la actualidad, y parte de las problemáticas que ellos presentan, se proyectan también sobre Profibus y otros sistemas más modernos.Facultad de Informátic

A Survey on Industrial Control System Testbeds and Datasets for Security Research

The increasing digitization and interconnection of legacy Industrial Control Systems (ICSs) open new vulnerability surfaces, exposing such systems to malicious attackers. Furthermore, since ICSs are often employed in critical infrastructures (e.g., nuclear plants) and manufacturing companies (e.g., chemical industries), attacks can lead to devastating physical damages. In dealing with this security requirement, the research community focuses on developing new security mechanisms such as Intrusion Detection Systems (IDSs), facilitated by leveraging modern machine learning techniques. However, these algorithms require a testing platform and a considerable amount of data to be trained and tested accurately. To satisfy this prerequisite, Academia, Industry, and Government are increasingly proposing testbed (i.e., scaled-down versions of ICSs or simulations) to test the performances of the IDSs. Furthermore, to enable researchers to cross-validate security systems (e.g., security-by-design concepts or anomaly detectors), several datasets have been collected from testbeds and shared with the community. In this paper, we provide a deep and comprehensive overview of ICSs, presenting the architecture design, the employed devices, and the security protocols implemented. We then collect, compare, and describe testbeds and datasets in the literature, highlighting key challenges and design guidelines to keep in mind in the design phases. Furthermore, we enrich our work by reporting the best performing IDS algorithms tested on every dataset to create a baseline in state of the art for this field. Finally, driven by knowledge accumulated during this survey's development, we report advice and good practices on the development, the choice, and the utilization of testbeds, datasets, and IDSs

A dynamically reconfigurable hard-real-time communication protocol for embedded systems

Echtzeitkommunikation ist eine Grundanforderung für viele verteilte eingebettete Systeme. Für eine neue Klasse von Anwendungen sind jedoch nicht nur Echtzeitfähigkeit, sondern auch Flexibilität und Anpassungsfähigkeit notwendige System-Attribute. Um die Flexibilität zu erhöhen, wurde in dieser Arbeit ein neues Kommunikationsprotokoll namens TrailCable konzipiert. Es profitiert von den Eigenschaften des Earliest Deadline First Scheduling-Verfahrens, wie z. B. der optimalen Ausnutzung von Ressourcen und der Unterstützung von heterogenen Tasks. Ein Kommunikationsnetzwerk wird aufgebaut mit Hilfe von voll-Duplex-, Punkt-zu-Punkt-Verbindungen, wobei die Knoten Datenpakete weiterleiten können, um eine Multi-hop Übertragung zu gewährleisten. Es werden Methoden vorgestellt, die es erlauben, automatisch die Kommunikationsanforderungen erfüllende Echtzeit-Kanäle auf das Netzwerk abzubilden. Echtzeit-Kanäle können nur dann aktiviert werden, wenn im Voraus ein Akzeptanztest erfolgreich durchgeführt wurde. Solch eine Prüfung kann mittels eines Tools automatisch erfolgen. Alle dafür notwendigen Netzwerkinformationen werden aus XML-Dateien eingelesen. Zur Laufzeit prüft ein Mechanismus, der Bandbreitenwächter genannt wird, ob die eingelesenen Pakete mit ihrer Spezifikation übereinstimmen, damit Fehler die Echzeitfähigkeit anderer Kanäle nicht beeinträchtigen können. Zeitkritische Funktionen des Kommunikationsprotokolls, wie Scheduling, Bandbreitenwächter, Routing und Uhrsynchronisation, sind mittels dedizierter Hardware implementiert. Ein voll funktionsfähiger FPGA-basierter Prototyp wurde aufgebaut und in zahlreichen Tests evaluiert, um das Echtzeit-Verhalten des Protokolls unter realen Bedingungen zu testen und zu analysieren.Real-time communication is a basic requirement for many distributed embedded systems. However, for an emerging new class of applications not only real-time behavior but also flexibility and adaptability will become necessary system attributes. In order to increase the flexibility of real-time communication systems a new protocol called TrailCable was designed. It takes advantage of the properties of Earliest Deadline First (EDF) scheduling, which include optimal utilization bounds and the possibility to cope with heterogeneous task sets. A communication network is built with full-duplex, point-to-point links, and nodes can route packets to allow multi-hop message delivery. This work introduces methods for automatically mapping real-time channels on a given network directly from communication requirement specifications. The activation of real-time channels in the network is permitted only after a successful schedulability analysis, which can be executed automatically by a tool that checks XML-based network configuration models. At run-time, the characteristics of all incoming packets are checked against their specification by an admission control technique called bandwidth guardian, which is used to ensure that occasional faults will not impair the timeliness of other real-time channels. Time-critical functions of the communication protocol, such as scheduling, admission control, packet routing, and clock synchronization, are implemented by means of dedicated hardware. A fully operational FPGA-based prototype was built and used in different measurement experiments to validate the real-time behavior of the protocol under real conditions.Tag der Verteidigung: 02.04.2012Paderborn, Univ., Diss., 201

Sobre a aplicação de técnicas de controlo em redes industriais com falhas

Doutoramento em Engenharia EletrotécnicaThe performance of real-time networks is under continuous improvement as a result of several trends in the digital world. However, these tendencies not only cause improvements, but also exacerbates a series of unideal aspects of real-time networks such as communication latency, jitter of the latency and packet drop rate. This Thesis focuses on the communication errors that appear on such realtime networks, from the point-of-view of automatic control. Specifically, it investigates the effects of packet drops in automatic control over fieldbuses, as well as the architectures and optimal techniques for their compensation. Firstly, a new approach to address the problems that rise in virtue of such packet drops, is proposed. This novel approach is based on the simultaneous transmission of several values in a single message. Such messages can be from sensor to controller, in which case they are comprised of several past sensor readings, or from controller to actuator in which case they are comprised of estimates of several future control values. A series of tests reveal the advantages of this approach. The above-explained approach is then expanded as to accommodate the techniques of contemporary optimal control. However, unlike the aforementioned approach, that deliberately does not send certain messages in order to make a more efficient use of network resources; in the second case, the techniques are used to reduce the effects of packet losses. After these two approaches that are based on data aggregation, it is also studied the optimal control in packet dropping fieldbuses, using generalized actuator output functions. This study ends with the development of a new optimal controller, as well as the function, among the generalized functions that dictate the actuator’s behaviour in the absence of a new control message, that leads to the optimal performance. The Thesis also presents a different line of research, related with the output oscillations that take place as a consequence of the use of classic co-design techniques of networked control. The proposed algorithm has the goal of allowing the execution of such classical co-design algorithms without causing an output oscillation that increases the value of the cost function. Such increases may, under certain circumstances, negate the advantages of the application of the classical co-design techniques. A yet another line of research, investigated algorithms, more efficient than contemporary ones, to generate task execution sequences that guarantee that at least a given number of activated jobs will be executed out of every set composed by a predetermined number of contiguous activations. This algorithm may, in the future, be applied to the generation of message transmission patterns in the above-mentioned techniques for the efficient use of network resources. The proposed task generation algorithm is better than its predecessors in the sense that it is capable of scheduling systems that cannot be scheduled by its predecessor algorithms. The Thesis also presents a mechanism that allows to perform multi-path routing in wireless sensor networks, while ensuring that no value will be counted in duplicate. Thereby, this technique improves the performance of wireless sensor networks, rendering them more suitable for control applications. As mentioned before, this Thesis is centered around techniques for the improvement of performance of distributed control systems in which several elements are connected through a fieldbus that may be subject to packet drops. The first three approaches are directly related to this topic, with the first two approaching the problem from an architectural standpoint, whereas the third one does so from more theoretical grounds. The fourth approach ensures that the approaches to this and similar problems that can be found in the literature that try to achieve goals similar to objectives of this Thesis, can do so without causing other problems that may invalidate the solutions in question. Then, the thesis presents an approach to the problem dealt with in it, which is centered in the efficient generation of the transmission patterns that are used in the aforementioned approaches.Em resultado de várias tendências que têm afetado o mundo digital, o desempenho das redes de comunicação em tempo-real está continuamente a ser melhorado. No entanto, tais tendências não só introduzem melhorias, como também introduzem uma série de não idealidades, tais como a latência, o jitter da latência de comunicação e uma maior probabilidade de perda de pacotes. Esta tese tem o seu cerne em falhas de comunicação que surgem em tais redes, sob o ponto de vista do controlo automático. Concretamente, são estudados os efeitos das perdas de pacotes em redes de controlo, bem como arquitecturas e técnicas óptimas de compensação das mesmas. Primeiramente, ´e proposta uma nova abordagem para colmatar os problemas que surgem em virtude de tais perdas. Essa nova abordagem ´e baseada no envio simultâneo de vários valores numa única mensagem. Tais mensagens podem ser de sensor para controlador, caso em que as mesmas são constituídas por um conjunto de valores passados, ou de controlador para actuador, caso em que tais mensagens contˆem estimativas de futuros valores de controlo. Uma série de testes revela as vantagens de tal abordagem. A abordagem acima explanada ´e seguidamente expandida de modo a acomodar o controlo óptimo. Contudo, ao contrário da abordagem acima apresentada, que passa pelo não envio deliberado de certas mensagens com vista a alcançar um uso mais eficiente dos recursos de rede; no presente caso, as técnicas são usadas para reduzir os efeitos da perda de pacotes. Em seguida são estudadas abordagens de controlo óptimo que em situações de perda de pacotes empregam formas generalizadas da aplicação de valores de saída. Este estudo culmina com o desenvolvimento de um novo controlador óptimo, bem como a função, entre as funções generalizadas do funcionamento do actuador, que conduz o sistema a um desempenho óptimo. É também apresentada uma linha de investigação diferente, relacionada com a oscilação da saída que ocorre em consequência da utilização de técnicas e algoritmos clássicos de co-desenho de controlo e redes industriais. O algoritmo proposto tem como finalidade permitir que tais algoritmos clássicos possam ser executados sem causar oscilações de saída, oscilações que por sua vez aumentam o valor da função de custo. Tais aumentos da função do custo, podem, em certas circunstâncias, por em causa os benefícios da aplicação das técnicas de co-desenho clássico. Numa outra linha de investigação, foram estudadas formas, mais eficientes que as contemporâneas, de geração de sequências de execuções de tarefas que garantam que pelo menos um dado número de tarefas activadas serão executadas por cada conjunto contíguo composto por um número predefinido de activações. Esta técnica poderá, no futuro, ser aplicada na geração dos padrões de envio de mensagens que ´e empregue na abordagem de utilização eficiente dos recursos de rede acima referida. A técnica proposta de geração de tarefas é melhor que as anteriores no sentido em que a mesma é capaz de escalonar sistemas que não são escalonáveis pelas técnicas clássicas. A tese também apresenta um mecanismo que permite fazer o encaminhamento multi-caminho em redes de sensores sem fios com falhas sem causar a contagem em duplicado. Assim sendo a mesma técnica melhora o desempenho das redes de sensores sem fios, tornando as mesmas mais maleável as necessidades do controlo aum´atico em redes sem fios. Como foi referido acima, a tese foca-se em t´ecnicas de melhoria de desempenho de sistemas de controlo distribu´ıdo em que os v´arios elementos de controlo encontram-se interligados por meio de uma rede industrial que pode estar sujeita a perda de pacotes. As primeiras três abordagens cingemse a este tema, sendo que primeiras duas olham para o problema sob um ponto de vista arquitetural, enquanto que a terceira olha sob um ponto de vista mais teórico. A quarta abordagem garante que outras propostas que podem ser encontradas na literatura e que visam atingir resultados semelhantes aos que se pretendem atingir nesta tese, possam fazˆe-lo sem causar outros problemas que invalidem as soluções em questão. Seguidamente, é apresenta-se uma abordagem ao problema proposto nesta tese que foca-se na geração eficiente de padrões para subsequente utilização nas abordagens acima referidas. E por fim, apresentar-se-a uma técnica de optimização do funcionamento de redes sem fios que promete melhorar o controlo em tais redes