Submitted by Felipe Fakir null (zafakir@yahoo.com.br) on 2017-06-27T07:01:28Z No. of bitstreams: 1 FFAKIR Dissertação vFinalFichaCataAta.pdf: 2064786 bytes, checksum: 158a935a636b9dbf9e59618a35b4c8ef (MD5) / Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-06-28T19:39:58Z (GMT) No. of bitstreams: 1 fakir_f_me_bauru.pdf: 2064786 bytes, checksum: 158a935a636b9dbf9e59618a35b4c8ef (MD5) / Made available in DSpace on 2017-06-28T19:39:58Z (GMT). No. of bitstreams: 1 fakir_f_me_bauru.pdf: 2064786 bytes, checksum: 158a935a636b9dbf9e59618a35b4c8ef (MD5) Previous issue date: 2017-06-01 / A tecnologia de comunicação wireless vem se tornando parte fundamental do cotidiano das indústrias de processos, onde o uso de transmissores wireless aplicados à monitoração e controle já é uma realidade. A arquitetura de Sistema de Controle via Rede Sem Fio (WNCS) possui vantagens em relação às arquiteturas tradicionais ponto-a-ponto e às arquiteturas de redes cabeadas devido à facilidade de instalação, configuração e manutenção. No entanto, a evolução desta tecnologia introduziu novos desafios para a implementação da malha de controle fechada por um instrumento wireless como as não linearidades, perda de pacote de dados e restrições da comunicação de dados nas redes sem fio. Outro fator crítico relacionado à implementação de WNCSs é a fonte de energia limitada destes transmissores, que possuem vida útil dependente da quantidade de acessos e dados transmitidos. Este trabalho apresenta o estudo e o desenvolvimento de um controlador preditivo multi-rate como alternativa para melhorar a eficiência energética em aplicações industriais de WNCSs. A estratégia proposta não necessita receber constantemente os valores reais das variáveis do processo transmitidos pelos transmissores wireless, pois o controlador preditivo baseado em modelo (MPC) se utiliza do submodelo interno das variáveis de processo para estimar os valores das variáveis quando estas não são transmitidas. Dessa forma, uma diminuição da frequência de transmissão de dados na rede sem fio pode ser obtida e, consequentemente uma redução do consumo energético dos dispositivos sem fio. Resultados de simulações em diferentes condições de operação de um WNCS multivariável de controle de tanques acoplados demonstram que o MPC multi-rate possui características de robustez e é efetivo para aplicações de WNCS, garantindo requisitos de controle e estabilidade mesmo com a diminuição da frequência de transmissão de dados de realimentação na rede sem fio. Adicionalmente, resultados do consumo energético dos dispositivos do WNCS mostraram que o MPC multi-rate proporciona uma economia de energia de até 20% das baterias dos transmissores wireless. Uma análise da eficiência energética do WNCS é apresentada através do estudo dos limites operacionais do controlador MPC multi-rate considerando a relação de compromisso entre o período de amostragem dos dispositivos sem fio e o desempenho de controle do WNCS. / Wireless communication technology has become a fundamental part of the everyday life of process industries, where the use of wireless transmitters for monitoring and control is already a reality. The architecture of Wireless Networked Control Systems (WNCSs) has advantages over point-to-point and wired networks architectures due to the ease of installation, configuration and maintenance. However, the evolution of this technology has introduced new challenges to the implementation of the closed loop control with a wireless instrument as nonlinearities, packet losses and data communication constraints in the wireless networks. Another critical factor related to implementation of WNCSs is the energy source of these transmitters, which have limited lifetime dependent on the amount of access and data transmitted. This work presents the study and the development of a multi-rate predictive controller as an alternative to improve energy efficiency in industrial applications of WNCSs. The proposed strategy does not need to frequently receive updated process variables transmitted by wireless transmitters, because the model predictive controller (MPC) uses the internal submodel of the process variables to estimate the variables values when they are not transmitted. Thus, a decrease in the frequency of data transmission on the wireless network can be obtained and consequently a reduction of energy consumption of wireless devices. Simulation results for different operating conditions of a multivariable WNCS of coupled tanks shows that the multi-rate MPC provides robustness and it is effective for WNCS applications, ensuring control and stability requirements even with the reduction of the transmission frequency of the feedback data in the wireless network. In addition, energy consumption results from the WNCS devices showed that MPC multi-rate provides 20% of energy economy as it is effective in saving the energy expenditure of the wireless transmitter’s battery. An energy efficiency analysis of the WNCS is presented by studying the operating limits of the multi-rate MPC controller considering the compromise relationship between the sampling period of the wireless devices and the control performance of the WNCS.

Este trabalho investiga a influência da quantização em sistemas de controle em rede. São tratados problemas de estabilidade e estabilização de sistemas lineares de tempo discreto envolvendo quantização finita nas entradas da planta controlada, considerando dois tipos de quantizadores: os uniformes e os logarítmicos. Como consequência da quantização finita, ocorrem também efeitos de saturação e zonamorta dos sinais de entrada. Tais comportamentos não-lineares são considerados explicitamente na análise. Para plantas instáveis, o objetivo é estimar a região onde os estados estarão confinados em regime permanente. Esta região, denominada atrator dos estados, é estimada por meio de um conjunto elipsoidal. Ao mesmo tempo, determina-se um conjunto elipsoidal de condições iniciais admissíveis, para o qual se garante a convergência das trajetórias para o atrator em tempo finito. Primeiramente, esses conjuntos são determinados para o caso de um controlador dado e, posteriormente, sintetiza-se um controlador que minimiza o atrator. Em se tratando de plantas estáveis, investiga-se como o desempenho dinâmico é afetado pela quantização. Para tanto, utiliza-se como critério o coeficiente de decaimento exponencial que é garantido para o sistema. Nesta parte, excluem-se os comportamentos na região de saturação e na região da zona-morta. Primeiramente, o coeficiente de decaimento garantido é estimado para um sistema com controlador dado. Neste caso, faz-se uma análise de degradação de desempenho induzida pela quantização com relação ao comportamento do sistema em malha fechada sem quantização. Posteriormente, sintetiza-se um controlador que minimiza este coeficiente na presença da quantização. Na obtenção dos resultados, utilizam-se condições de setor respeitadas pelas não linearidades e formulam-se os problemas na forma de inequações matriciais que podem ser resolvidas a partir de problemas de otimização baseados em LMIs. / This work investigates the in uence of quantization over networked control systems. At rst, we tackle stability and stabilization problems of discrete-time linear systems involving nite quantization on the input of the controlled plant, considering two kinds of quantizers: uniform and logarithmic. As a consequence of the nite quantization, saturation and dead-zone e ects on the input signals are also present. These non-linear behaviors are explictly considered in the analysis. For unstable plants, the objective is to estimate the region where the states will be ultimately bounded. This region, which we call the attractor of the states, is estimated through an ellipsoidal set. Simultaneously, we determine an ellipsoidal set of admissible initial conditions, for which the trajectories will converge to the attractor in nite time. At rst, the sets are determined for the case where the controller is given and, in the sequel, a controller that minimizes the attractor is designed. When dealing with stable plants, we investigate how the dynamic performance is a ected by the quantization. To do that, we use as criterion the exponential decay rate which is guaranteed for the system. At this point, we exclude the behaviour in the saturation and deadzone regions. At rst, the guaranteed decay rate is estimated for a system where the controller is given. In this case, we analyze the deterioration of the performance in uenced by the quantization, compared to the behavior of the closed-loop system without quantization. In the sequel, a controller that minimizes that rate in the presence of quantization is designed. To obtain the results, we use sector conditions which are respected by the nonlinearities and we state the problems as matrix inequalities which can be solved using LMI-based optimization problems.

In recent years, the security of networked control systems (NCSs) has been an important challenge for many researchers. Although the security schemes for networked control systems have advanced in the past several years, there have been many acknowledged cyber attacks. As a result, this dissertation proposes the use of a novel time-delay switch (TDS) attack by introducing time delays into the dynamics of NCSs. Such an attack has devastating effects on NCSs if prevention techniques and countermeasures are not considered in the design of these systems. To overcome the stability issue caused by TDS attacks, this dissertation proposes a new detector to track TDS attacks in real time. This method relies on an estimator that will estimate and track time delays introduced by a hacker. Once a detector obtains the maximum tolerable time delay of a plant’s optimal controller (for which the plant remains secure and stable), it issues an alarm signal and directs the system to its alarm state. In the alarm state, the plant operates under the control of an emergency controller that can be local or networked to the plant and remains in this stable mode until the networked control system state is restored. In another effort, this dissertation evaluates different control methods to find out which one is more stable when under a TDS attack than others. Also, a novel, simple and effective controller is proposed to thwart TDS attacks on the sensing loop (SL). The modified controller controls the system under a TDS attack. Also, the time-delay estimator will track time delays introduced by a hacker using a modified model reference-based control with an indirect supervisor and a modified least mean square (LMS) minimization technique. Furthermore, here, the demonstration proves that the cryptographic solutions are ineffective in the recovery from TDS attacks. A cryptography-free TDS recovery (CF-TDSR) communication protocol enhancement is introduced to leverage the adaptive channel redundancy techniques, along with a novel state estimator to detect and assist in the recovery of the destabilizing effects of TDS attacks. The conclusion shows how the CF-TDSR ensures the control stability of linear time invariant systems.

Stability analysis of networked dynamical systems has been of interest in many disciplines such as biology and physics and chemistry with applications such as LASER cooling and plasma stability. These large networks are often modeled to have a completely random (Erdös-Rényi) or semi-random (Small-World) topologies. The former model is often used due to mathematical tractability while the latter has been shown to be a better model for most real life networks. The recent emergence of cyber physical systems, and in particular the smart grid, has given rise to a number of engineering questions regarding the control and optimization of such networks. Some of the these questions are: How can the stability of a random network be characterized in probabilistic terms? Can the effects of network topology and system dynamics be separated? What does it take to control a large random network? Can decentralized (pinning) control be effective? If not, how large does the control network needs to be? How can decentralized or distributed controllers be designed? How the size of control network would scale with the size of networked system? Motivated by these questions, we began by studying the probability of stability of synchronization in random networks of oscillators. We developed a stability condition separating the effects of topology and node dynamics and evaluated bounds on the probability of stability for both Erdös-Rényi (ER) and Small-World (SW) network topology models. We then turned our attention to the more realistic scenario where the dynamics of the nodes and couplings are mismatched. Utilizing the concept of ε-synchronization, we have studied the probability of synchronization and showed that the synchronization error, ε, can be arbitrarily reduced using linear controllers. We have also considered the decentralized approach of pinning control to ensure stability in such complex networks. In the pinning method, decentralized controllers are used to control a fraction of the nodes in the network. This is different from traditional decentralized approaches where all the nodes have their own controllers. While the problem of selecting the minimum number of pinning nodes is known to be NP-hard and grows exponentially with the number of nodes in the network we have devised a suboptimal algorithm to select the pinning nodes which converges linearly with network size. We have also analyzed the effectiveness of the pinning approach for the synchronization of oscillators in the networks with fast switching, where the network links disconnect and reconnect quickly relative to the node dynamics. To address the scaling problem in the design of distributed control networks, we have employed a random control network to stabilize a random plant network. Our results show that for an ER plant network, the control network needs to grow linearly with the size of the plant network.

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No description available.

Markov jump linear systems find application in many areas including economics, fault-tolerant control, and networked control. Despite significant attention paid to Markov jump linear systems in the literature, few authors have investigated Markov jump linear systems with time-inhomogeneous Markov chains (Markov chains with time-varying transition probabilities), and even fewer authors have considered time-inhomogeneous Markov chains with a priori unknown transition probabilities. This dissertation provides a formal stability and disturbance attenuation analysis for a Markov jump linear system where the underlying Markov chain is characterized by an a priori unknown sequence of transition probability matrices that assumes one of finitely-many values at each time instant. Necessary and sufficient conditions for uniform stochastic stability and uniform stochastic disturbance attenuation are reported. In both cases, conditions are expressed as a set of finite-dimensional linear matrix inequalities (LMIs) that can be solved efficiently. These finite-dimensional LMI analysis results lead to nonconservative LMI formulations for optimal controller synthesis with respect to disturbance attenuation. As a special case, the analysis also applies to a Markov jump linear system with known transition probabilities that vary in a finite set. / Ph. D.

L’objectif principal de cette thèse est l’étude de propriétés dynamiques et de méthodes de conception et synthèse des algorithmes de contrôle-commande des systèmes dans le cas où les fonctions de mesures, actionnements et contrôles sont distribuées sur des organes de calcul pouvant être partagés avec d’autres applications et connectés sur un réseau de communication numérique. En conséquence, les boucles de contrôle sont en compétition avec d’autres applications pour accéder aux ressources de calcul et de communication de capacité limitée et gérées par des politiques spécifiques. Ceci provoque l’apparition de délais et de perte d’informations transmises entre les différents nœuds qui peuvent dégrader les performances des systèmes et conduire à leur instabilité.Dans une première partie de la thèse, nous avons étudié l’analyse des performances de certains systèmes ainsi que la conception de contrôleurs robustes en fonction de la qualité de service fournie par le réseau. Cette étude a permis de spécifier les règles de conception de contrôleurs.Dans la deuxième partie, nous avons présenté une approche de conception conjointe intégrant les résultats obtenus dans les deux domaines: la synthèse et la conception des algorithmes de contrôle et l’ordonnancement de tâches temps réel qui partagent des ressources limitées. La technique proposée repose sur le changement de la période d’activation de l’algorithme de contrôle, et en conséquence le modèle du système devient un modèle échantillonné à taux variable. Les résultats proposés, en considérant l’algèbre de Lie des matrices d’évolution, permettent de calculer des contrôleurs adaptifs aux périodes qui stabilisent tous le système / The main contributions of this thesis are related to the analysis, synthesis and design of control systems sharing communication and computational resources. The research focuses on control systems where the feedback loops are closed over communication networks which transmit the information provided to its nodes by sensors, actuators and controllers. The shared resource in this scenario is the network. Some of the results are valid when the resource is a processor locally placed respect to several controller executing their algorithms on it. In any of the preceding scenarios, the control loops must contend for the shared resource. The limited capacity of the resource can cause delays and packet losses when information is transmitted. These effects can degrade the control system performance and even destabilize it.The first part of this thesis contributes to the performance analysis of specific classes of systems and to the design of robust controllers for network characteristics modeled by Quality of Service parameters. A series of methods to assist the control systems engineer are provided.In the second part, a contribution to the CoDesign approach is made via the integration of control system synthesis and design techniques with rules allowing to define the communication policy to manage real-time tasks sharing a limited resource. Putting in correspondence a scheduling of instances of the controller tasks with their sampling periods, the proposed policy results in discrete-time varying systems. The stabilization problem of these systems is solved with methods based on the solvability of Lie-algebras. Specifically, the proposed methodology provides adaptive controllers

La commande à transmissions événementielles est une approche dans laquelle les instants de transmission sont définis selon un critère dépendant de l'état du système et non plus d'une horloge à l'instar des implantations périodiques. Dans cette thèse, nous nous concentrons sur la synthèse de telles lois de commande par retour de sortie. Les contributions sont les suivantes : (i) nous proposons une méthode de synthèse dite par émulation pour des systèmes non linéaires; (ii) nous présentons une méthode de synthèse jointe de la loi de commande et de la condition de déclenchement pour les systèmes linéaires; (iii) nous nous intéressons au cas de systèmes non linéaires singulièrement perturbés et nous construisons le contrôleur à partir d’approximation de la dynamique lente uniquement. / Event-triggered control is a sampling paradigm in which the sequence of transmission instants is determined based on the violation of a state-dependent criterion and not a time-driven clock. In this thesis, we deal with event-triggered output-based controllers to stabilize classes of nonlinear systems. The contributions of the presented material are threefold: (i) we stabilize a class of nonlinear systems by using an emulation-based approach; (ii) we develop a co-design procedure to simultaneously design the output feedback law and the event-triggering condition for linear systems; (iii) we propose stabilizing event-triggered controllers for nonlinear systems whose dynamics have two-time scales (in particular, we only rely on the knowledge of an approximate model of the slow dynamics)

Sistema de controle via rede (NCS) é um sistema de controle distribuído onde os sensores, atuadores e controladores estão alocados fisicamente em locais separados e são conectados através de uma rede de comunicação industrial. O NCS representa a evolução das arquiteturas de controle em rede, fornecendo maior modularidade e descentralização do controle, facilidade de diagnóstico e manutenção e menor custo. O desafio no desenvolvimento de um NCS é contornar os efeitos degenerativos causados por fatores que afetam o seu desempenho e estabilidade. Entre estes fatores estão o período de amostragem dos sinais, a perda de informações transmitidas na rede e os atrasos de comunicação. Buscando superar este desafio, este trabalho apresenta o desenvolvimento de NCS para aplicações em redes CAN baseado no uso da simulação e na proposta de uma estratégia de controle. A utilização de ferramentas de simulação de NCS, selecionadas através de um estudo comparativo e qualitativo, permitiu analisar o impacto de fatores degenerativos no desempenho de controle e estabilidade de NCS. Essa análise por simulação permitiu evidenciar o período de amostragem como o fator de maior influência para o projeto de NCS em redes CAN. Para superar o problema do período de amostragem, uma estratégia de controle adaptativo foi proposta. Essa estratégia usa informações de saída do NCS para automaticamente adaptar o período de amostragem das mensagens, garantindo desempenho de controle e diminuindo significativamente a ocupação da rede CAN. Experimentos realizados em uma plataforma de pesquisa sobre NCS demonstraram a confiabilidade e robustez do uso da estratégia de controle adaptativo, mesmo em condições extremas de operação da rede CAN. Os experimentos também permitiram comprovar a eficácia de uma técnica de identificação de NCS desenvolvida, que apresenta a vantagem de utilizar informações disponíveis na rede para obtenção de um modelo do NCS com precisão aceitável. / Networked control system (NCS) is a distributed control system where the sensors, actuators and controllers are physically separated and connected through an industrial communication network. The NCS represents the evolution of networked control architectures providing greater modularity and control decentralization, maintenance and diagnosis ease and lower cost of implementation. The challenge in the development of NCS is to overcome the degenerative effects of factors which affect its performance and stability. Among these factors are the sampling time, the loss of information on the network and the network delays. Aiming to overcome this challenge, this work presents the development of NCS for applications in CAN-Based networks based on the simulation use and in a control strategy proposal. The use NCS simulation tools, selected by a comparative and qualitative study, allowed to analyze the impact of degrading factors in the NCS control performance and stability. This analysis using simulation highlighted the message sampling time as factor with the biggest influence for the design of CAN-based NCS. To overcome the sampling time problem, an adaptive control strategy was proposed. This strategy uses the NCS output to automatically adapt the message sampling time, ensuring NCS control performance and stability and providing significant reduction of the CAN network load. Experiments carried out on a NCS Research Platform demonstrated the reliability and robustness of the adaptive control methodology application, even under worst case conditions of operation of the CAN-based network. Experiments have also proved the effectiveness of a model identification technique developed for NCS, which presents the advantage of using information available on the network to obtain the NCS model with acceptable accuracy.