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

Networked Control System Design and Parameter Estimation

Networked control systems (NCSs) are a kind of distributed control systems in which the data between control components are exchanged via communication networks. Because of the attractive advantages of NCSs such as reduced system wiring, low weight, and ease of system diagnosis and maintenance, the research on NCSs has received much attention in recent years. The first part (Chapter 2 - Chapter 4) of the thesis is devoted to designing new controllers for NCSs by incorporating the network-induced delays. The thesis also conducts research on filtering of multirate systems and identification of Hammerstein systems in the second part (Chapter 5 - Chapter 6). Network-induced delays exist in both sensor-to-controller (S-C) and controller-to-actuator (C-A) links. A novel two-mode-dependent control scheme is proposed, in which the to-be-designed controller depends on both S-C and C-A delays. The resulting closed-loop system is a special jump linear system. Then, the conditions for stochastic stability are obtained in terms of a set of linear matrix inequalities (LMIs) with nonconvex constraints, which can be efficiently solved by a sequential LMI optimization algorithm. Further, the control synthesis problem for the NCSs is considered. The definitions of H₂ and H∞ norms for the special system are first proposed. Also, the plant uncertainties are considered in the design. Finally, the robust mixed H₂/H∞ control problem is solved under the framework of LMIs. To compensate for both S-C and C-A delays modeled by Markov chains, the generalized predictive control method is modified to choose certain predicted future control signal as the current control effort on the actuator node, whenever the control signal is delayed. Further, stability criteria in terms of LMIs are provided to check the system stability. The proposed method is also tested on an experimental hydraulic position control system. Multirate systems exist in many practical applications where different sampling rates co-exist in the same system. The l₂-l∞ filtering problem for multirate systems is considered in the thesis. By using the lifting technique, the system is first transformed to a linear time-invariant one, and then the filter design is formulated as an optimization problem which can be solved by using LMI techniques. Hammerstein model consists of a static nonlinear block followed in series by a linear dynamic system, which can find many applications in different areas. New switching sequences to handle the two-segment nonlinearities are proposed in this thesis. This leads to less parameters to be estimated and thus reduces the computational cost. Further, a stochastic gradient algorithm based on the idea of replacing the unmeasurable terms with their estimates is developed to identify the Hammerstein model with two-segment nonlinearities. Finally, several open problems are listed as the future research directions

Robust optimal design of FOPID controller for five bar linkage robot in a cyber-physical system: a new simulation-optimization approach

This paper aims to further increase the reliability of optimal results by setting the simulation conditions to be as close as possible to the real or actual operation to create a Cyber-Physical System (CPS) view for the installation of the Fractional-Order PID (FOPID) controller. For this purpose, we consider two different sources of variability in such a CPS control model. The first source refers to the changeability of a target of the control model (multiple setpoints) because of environmental noise factors and the second source refers to an anomaly in sensors that is raised in a feedback loop. We develop a new approach to optimize two objective functions under uncertainty including signal energy control and response error control while obtaining the robustness among the source of variability with the lowest computational cost. A new hybrid surrogate-metaheuristic approach is developed using Particle Swarm Optimization (PSO) to update the Gaussian Process (GP) surrogate for a sequential improvement of the robust optimal result. The application of efficient global optimization is extended to estimate surrogate prediction error with less computational cost using a jackknife leave-one-out estimator. This paper examines the challenges of such a robust multi-objective optimization for FOPID control of a five-bar linkage robot manipulator. The results show the applicability and effectiveness of our proposed method in obtaining robustness and reliability in a CPS control system by tackling required computational efforts

Security Risk Management for the Internet of Things

In recent years, the rising complexity of Internet of Things (IoT) systems has increased their potential vulnerabilities and introduced new cybersecurity challenges. In this context, state of the art methods and technologies for security risk assessment have prominent limitations when it comes to large scale, cyber-physical and interconnected IoT systems. Risk assessments for modern IoT systems must be frequent, dynamic and driven by knowledge about both cyber and physical assets. Furthermore, they should be more proactive, more automated, and able to leverage information shared across IoT value chains. This book introduces a set of novel risk assessment techniques and their role in the IoT Security risk management process. Specifically, it presents architectures and platforms for end-to-end security, including their implementation based on the edge/fog computing paradigm. It also highlights machine learning techniques that boost the automation and proactiveness of IoT security risk assessments. Furthermore, blockchain solutions for open and transparent sharing of IoT security information across the supply chain are introduced. Frameworks for privacy awareness, along with technical measures that enable privacy risk assessment and boost GDPR compliance are also presented. Likewise, the book illustrates novel solutions for security certification of IoT systems, along with techniques for IoT security interoperability. In the coming years, IoT security will be a challenging, yet very exciting journey for IoT stakeholders, including security experts, consultants, security research organizations and IoT solution providers. The book provides knowledge and insights about where we stand on this journey. It also attempts to develop a vision for the future and to help readers start their IoT Security efforts on the right foot

DevOps for Trustworthy Smart IoT Systems

ENACT is a research project funded by the European Commission under its H2020 program. The project consortium consists of twelve industry and research member organisations spread across the whole EU. The overall goal of the ENACT project was to provide a novel set of solutions to enable DevOps in the realm of trustworthy Smart IoT Systems. Smart IoT Systems (SIS) are complex systems involving not only sensors but also actuators with control loops distributed all across the IoT, Edge and Cloud infrastructure. Since smart IoT systems typically operate in a changing and often unpredictable environment, the ability of these systems to continuously evolve and adapt to their new environment is decisive to ensure and increase their trustworthiness, quality and user experience. DevOps has established itself as a software development life-cycle model that encourages developers to continuously bring new features to the system under operation without sacrificing quality. This book reports on the ENACT work to empower the development and operation as well as the continuous and agile evolution of SIS, which is necessary to adapt the system to changes in its environment, such as newly appearing trustworthiness threats

DevOps for Trustworthy Smart IoT Systems

ENACT is a research project funded by the European Commission under its H2020 program. The project consortium consists of twelve industry and research member organisations spread across the whole EU. The overall goal of the ENACT project was to provide a novel set of solutions to enable DevOps in the realm of trustworthy Smart IoT Systems. Smart IoT Systems (SIS) are complex systems involving not only sensors but also actuators with control loops distributed all across the IoT, Edge and Cloud infrastructure. Since smart IoT systems typically operate in a changing and often unpredictable environment, the ability of these systems to continuously evolve and adapt to their new environment is decisive to ensure and increase their trustworthiness, quality and user experience. DevOps has established itself as a software development life-cycle model that encourages developers to continuously bring new features to the system under operation without sacrificing quality. This book reports on the ENACT work to empower the development and operation as well as the continuous and agile evolution of SIS, which is necessary to adapt the system to changes in its environment, such as newly appearing trustworthiness threats

Internet of Things and the Law: Legal Strategies for Consumer-Centric Smart Technologies

Internet of Things and the Law: Legal Strategies for Consumer-Centric Smart Technologies is the most comprehensive and up-to-date analysis of the legal issues in the Internet of Things (IoT). For decades, the decreasing importance of tangible wealth and power – and the increasing significance of their disembodied counterparts – has been the subject of much legal research. For some time now, legal scholars have grappled with how laws drafted for tangible property and predigital ‘offline’ technologies can cope with dematerialisation, digitalisation, and the internet. As dematerialisation continues, this book aims to illuminate the opposite movement: rematerialisation, namely, the return of data, knowledge, and power within a physical ‘smart’ world. This development frames the book’s central question: can the law steer rematerialisation in a human-centric and socially just direction? To answer it, the book focuses on the IoT, the sociotechnological phenomenon that is primarily responsible for this shift. After a thorough analysis of how existing laws can be interpreted to empower IoT end users, Noto La Diega leaves us with the fundamental question of what happens when the law fails us and concludes with a call for collective resistance against ‘smart’ capitalism

Internet of Things and the Law: Legal Strategies for Consumer-Centric Smart Technologies

Internet of Things and the Law: Legal Strategies for Consumer-Centric Smart Technologies is the most comprehensive and up-to-date analysis of the legal issues in the Internet of Things (IoT). For decades, the decreasing importance of tangible wealth and power – and the increasing significance of their disembodied counterparts – has been the subject of much legal research. For some time now, legal scholars have grappled with how laws drafted for tangible property and predigital ‘offline’ technologies can cope with dematerialisation, digitalisation, and the internet. As dematerialisation continues, this book aims to illuminate the opposite movement: rematerialisation, namely, the return of data, knowledge, and power within a physical ‘smart’ world. This development frames the book’s central question: can the law steer rematerialisation in a human-centric and socially just direction? To answer it, the book focuses on the IoT, the sociotechnological phenomenon that is primarily responsible for this shift. After a thorough analysis of how existing laws can be interpreted to empower IoT end users, Noto La Diega leaves us with the fundamental question of what happens when the law fails us and concludes with a call for collective resistance against ‘smart’ capitalism