Networked control systems (NCSs) present many advantages such as easy installation and maintenance, flexible layouts and structures of components, and efficient allocation and distribution of resources. Consequently, they find potential applications in a variety of emerging industrial systems including multi-agent systems, power grids, tele-operations and cyber-physical systems. The study of NCSs with nonlinear dynamics (i.e., nonlinear NCSs) is a very significant yet challenging topic, and it not only widens application areas of NCSs in practice, but also extends the theoretical framework of NCSs with linear dynamics (i.e., linear NCSs). Numerous issues are required to be resolved towards a fully-fledged theory of industrial nonlinear NCS design. In this dissertation, three important problems of nonlinear NCSs are investigated: The robust filtering problem, the robust model predictive control (MPC) problem and the robust distributed MPC problem of large-scale nonlinear systems. In the robust filtering problem of nonlinear NCSs, the nonlinear system model is subject to uncertainties and external disturbances, and the measurements suffer from time delays governed by a Markov process. Utilizing the Lyapunov theory, the algebraic Hamilton-Jacobi inequality (HJI)-based sufficient conditions are established for designing the H_infty nonlinear filter. Moreover, the developed results are specialized for a special type of nonlinear systems, by presenting the HJI in terms of matrix inequalities. For the robust MPC problem of NCSs, three aspects are considered. Firstly, to reduce the computation and communication load, the networked MPC scheme with an efficient transmission and compensation strategy is proposed, for constrained nonlinear NCSs with disturbances and two-channel packet dropouts. A novel Lyapunov function is constructed to ensure the input-to-state practical stability (ISpS) of the closed-loop system. Secondly, to improve robustness, a networked min-max MPC scheme are developed, for constrained nonlinear NCSs subject to external disturbances, input and state constraints, and network-induced constraints. The ISpS of the resulting nonlinear NCS is established by constructing a new Lyapunov function. Finally, to deal with the issue of unavailability of system state, a robust output feedback MPC scheme is designed for constrained linear systems subject to periodical measurement losses and external disturbances. The rigorous feasibility and stability conditions are established. For the robust distributed MPC problem of large-scale nonlinear systems, three steps are taken to conduct the studies. In the first step, the issue of external disturbances is addressed. A robustness constraint is proposed to handle the external disturbances, based on which a novel robust distributed MPC algorithm is designed. The conditions for guaranteeing feasibility and stability are established, respectively. In the second step, the issue of communication delays are dealt with. By designing the waiting mechanism, a distributed MPC scheme is proposed, and the feasibility and stability conditions are established. In the third step, the robust distributed MPC problem for large-scale nonlinear systems subject to control input constraints, communication delays and external disturbances are studied. A dual-mode robust distributed MPC strategy is designed to deal with the communication delays and the external disturbances simultaneously, and the feasibility and the stability conditions are developed, accordingly. / Graduate / 0548 / 0544

Les travaux développés dans cette thèse portent sur la "co-conception diagnostic / ordonnancement des mesures dans un système contrôlé en réseau" qui est un sujet multidisciplinaire nécessitant des compétences en théorie du contrôle et en théorie des réseaux. La thèse a pour but de développer, dans le contexte des systèmes contrôlés en réseau, une approche de co-conception qui intègre de façon coordonnée les caractéristiques qui expriment la performance du diagnostic des défauts et les paramètres de l'ordonnancement temps-réel des messages. L'intérêt de cette approche coordonnée réside essentiellement dans la minimisation des ressources nécessaires pour atteindre la performance du diagnostic requise, minimisation qui prend tout son sens dans le contexte des systèmes embarqués. Nous nous sommes intéressés plus particulièrement à l'étude des problèmes liés à l'élaboration d'algorithmes de diagnostic efficaces et adaptés aux caractéristiques de l'application de façon tout en prenant en compte différents types de contraintes liées au réseau. En conjonction avec ces algorithmes, deux ensembles de techniques d'ordonnancement des mesures ont été développés : - ordonnancement hors ligne - ordonnancement évènementiel en ligne Pour l'ordonnancement hors ligne, les séquences de communication sont conçues en amont, préalablement à la mise en oeuvre de l'algorithme de diagnostic (implémentation). D'autre part, nous proposons aussi des techniques d'ordonnancement en ligne basées sur l'échantillonnage évènementiel développé au cours de la dernière décennie. Au contraire de la plupart des recherches en automatique classique, considérant que l'échantillonnage des signaux continus est réalisé d'une manière périodique, les mesures dans cette approche sont transmises si et seulement si la condition de transmission (évènement) est vérifiée / The works developed in this thesis deal with 'fault diagnosis and sensor scheduling co-design' in networked control system. This multidisciplinary subject requires theoretical knowledge in both fault diagnosis and communication networks. Our contribution consists in developing a co-design approach that integrates in the same framework the characteristics of fault diagnosis performance and real time sensor scheduling. The main benefit of this approach is minimizing the required network resources for attending acceptable fault diagnosis performances. We are interested in the development of more efficient and more adapted for real time implementation fault diagnosis algorithms while taking into account different types of communication constraints. In conjunction with these algorithms, two sets of sensor scheduling techniques are used : - Off-line scheduling - On-line scheduling (event triggered sampling) For off-line scheduling, the communication sequences are designed before the implementation of the diagnostic algorithm. In this context, we proposed several techniques for scheduling with different spatial and temporal complexity and adapted to different operating condition for the detection and the isolation of faults based on the information provided by the selected communication sequences. Moreover, we deal also with on-line scheduling techniques based on the event triggered sampling developed during the last decade. In This approach measurement packets are transmitted if and only if the transmission condition (event) is verified. This saves resources provided by the network while maintaining acceptable performance of fault diagnosis. The objective of these algorithms is to minimize the number of transmitted information which means less energy consumption and has a major importance in wireless networked control systems

Ce mémoire, réalisé dans le cadre d’une thèse sous convention CIFRE avec la société Schneider-Electric et l’Université de Lorraine à travers le laboratoire du CRAN, porte sur l’évaluation des performances temporelles des architectures de contrôle-commande distribuées sur un réseau de communication. Le besoin industriel s’exprime sous la forme d’un outil d’aide au dimensionnement des architectures en phase d’avant-vente caractérisée par une connaissance partielle de ces dernières. Le problème scientifique sous-jacent est relatif à la génération automatique des modèles servant de support à l’évaluation. En effet, l’évaluation des performances doit être réalisée pour un ensemble important d’architectures, dans un temps court, difficilement compatible avec une construction manuelle des modèles. Notre contribution porte sur la définition formelle, à l’aide de réseaux de Petri colorés et temporisés, d’un modèle « constructeur » d’architectures embarquant des mécanismes de configuration, d’instanciation et de paramétrage. Plusieurs algorithmes sont proposés pour, d’une part, construire automatiquement le modèle d’une architecture donnée, à partir d’une description formelle de sa topologie et d’une librairie de modèles d’équipements de contrôle-commande, et, d’autre part, pour générer les observateurs requis à partir d’une description formelle des performances à évaluer. Ces différents algorithmes ont été implantés dans un outil interfacé, d’une part avec l’outil Schneider de description des architectures, et, d’autre part avec le simulateur de l’outil CPN Tools qui fournit une estimation des performances via des simulations de Monte-Carlo. L’intérêt de cette approche a été illustrée sur la base de quelques architectures types fournies par la société Schneider-Electric / This PhD dissertation, supported by CIFRE convention between the company Schneider-Electric and the University of Lorraine through the CRAN laboratory, deals with the assessment of temporal performances for a networked distributed control system. The industrial need was the development of a quotation and sizing tool of industrial control architecture during pre-sales stage. This stage is characterized by limited information about the process and the customers’ needs. The underlying scientific problematic was the ability to generate automatically models serving as support for the evaluation. In fact, performance assessment is realized for a wide range of architecture during a small amount of time, which is not compliant with a manual definition of the models. Our contribution is mainly based on a formal definition of a “builder” model with Colored and Timed Petri Nets which embeds mechanisms for configuration, instantiation and parameters setting of the architecture models. Several algorithms have been proposed for firstly build automatically the architecture Petri Nets model from a formal description of the topology and from a component model library and, secondly, for generating performance observers. Theses algorithms have been implemented on a tool gathering a user interface developed by Schneider –Electric and the Petri Nets simulator called CPN Tools which provides the performance assessment through Monte-Carlo simulation. The added value of this approach has been illustrated through case studies provided by Schneider-Electric

&ldquo / Numerically Controlled&rdquo / (NC) machine tools, which are automatically operated by encoded (digital) commands, are capable of machining components with quality and quantity. Manufacturing industry heavily depends on these machines. Many different control architectures have been adapted in today&rsquo / s CNC technology. Centralized control system is quite popular in industry due to its ease of implementation. If the number of controlled axes on a CNC machine tool (&gt / 3), increases so does the computational burden on the central processors. Hence, more powerful processors are needed. An alternative architecture, which is not commonly used in CNC technology, is the decentralized (distributed) control. In this topology, the tasks handled by the distributed controllers that are interconnected to each other by a communication network. As the need arises, a new controller can be added easily to the network without augmenting the physical configuration. Despite its attractive features, this architecture has not been fully embraced by the CNC industry. Synchronization among the axes in the coordinated motion is proven to be quite challenging. In this thesis, alternative distributed controller architecture was proposed for CNC machine tools. It was implemented on a 3-axis CNC milling machine. Open-loop control performance was investigated under various conditions. Different communication protocols along with different physical communication interfaces and a number of controller hardware were devised. An industry-standard network (RS-485) was set up by interconnecting these distributed controllers. Different data transmission protocols were devised in order to establish appropriate communication methods. Also, computer software (a.k.a. graphical user interface), which can coordinate the interconnected controllers, interpret NC part programs and generate reference position data for each axis, was designed within the scope of this thesis.

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.

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.

De nos jours, les systèmes de contrôle-commande temps-réel distribués à travers un réseau de communication sont de plus en plus utilisés dans les secteurs de l’automobile, de l’avionique, de la robotique mobile, de la télécommunication et plus généralement de la conduite de procédés industriels. En comparaison avec les systèmes de contrôle point-à-point conventionnel, un système contrôlé en réseau (SCR) permet non seulement de réduire le câblage et les coûts d’installation, mais offre aussi plus de flexibilité pour faire évoluer une installation existante et favorise les actions de diagnostic et de maintenance. Comme le réseau est partagé par plusieurs boucles de contrôle et par d’autres applications, la conséquence est que le trafic de communication est difficilement maîtrisable, ce qui peut conduire à des pertes de messages et engendre des délais aléatoires. Par ailleurs, le diagnostic et la tolérance aux défauts sont des enjeux importants pour les SCR, particulièrement dans le cas ou le domaine d’utilisation exige une grande sécurité. Il est évident que la théorie et l’application des approches classiques de diagnostic et de tolérance aux défauts doivent être révisées lorsqu’il s’agit de SCR.L’étude des SCR, reposant sur des compétences en automatique, en informatique et en réseau propose naturellement des solutions propres à chaque domaine. La problématique du diagnostic des SCR consiste non seulement à détecter et localiser des défauts affectant l’ensemble du système mais aussi à distinguer, les perturbations et défaillances affectant le réseau de communication de celles du système contrôle. L’objectif de nos travaux de thèse est de proposer des modèles intégrés permettant de représenter le comportement des SCR et de contribuer à leurs diagnostics. / Real-time control systems distributed across communication networks are increasingly used in automotive, avionics, mobile robotics, and telecommunications and more generally in the conduct of industrial processes. Compared with point- to-point conventional control systems, a networked control system (NCS) can not only reduce wiring and installation costs, but also offer more flexibility to expand an existing facility and promote actions of diagnosis and maintenance. As the network is shared by multiple control loops and other applications, the result is that the communication traffic is difficult to control, which can lead to loss of messages and generate random delays.Diagnosis and fault tolerance are important issues for NCS, especially in the case where the area of application requires security. It’s obvious that the theory and application of conventional approaches to diagnosis and fault tolerance need to be revised when it comes to NCS.The study of the NCS, based on automatic skills, computer science and network competences naturally provides adequate solutions to each area. The problem of NCS diagnosis is the one hand to detect and locate faults affecting the whole system and on the other hand to distinguish, disturbances and malfunctions affecting the communication network of the control system.Our work aims is to propose integrated models to represent the behavior of NCS and contribute to its diagnosis.

Nous abordons des problèmes de sécurité dans des systèmes cyber-physiques industriels. Les attaques contre ces systèmes doivent être traitées à la fois en matière de sûreté et de sécurité. Les technologies de contrôles imposés par les normes industrielles, couvrent déjà la sûreté. Cependant, du point de vue de la sécurité, la littérature a prouvé que l’utilisation de techniques cyber pour traiter la sécurité de ces systèmes n’est pas suffisante, car les actions physiques malveillantes seront ignorées. Pour cette raison, on a besoin de mécanismes pour protéger les deux couches à la fois. Certains auteurs ont traité des attaques de rejeu et d’intégrité en utilisant une attestation physique, p. ex., le tatouage des paramètres physiques du système. Néanmoins, ces détecteurs fonctionnent correctement uniquement si les adversaires n’ont pas assez de connaissances pour tromper les deux couches. Cette thèse porte sur les limites mentionnées ci-dessus. Nous commençons en testant l’efficacité d’un détecteur qui utilise une signature stationnaire afin de détecter des actions malveillantes. Nous montrons que ce détecteur est incapable d’identifier les adversaires cyber-physiques qui tentent de connaître la dynamique du système. Nous analysons son ratio de détection sous la présence de nouveaux adversaires capables de déduire la dynamique du système. Nous revisitons le design original, en utilisant une signature non stationnaire, afin de gérer les adversaires visant à échapper à la détection. Nous proposons également une nouvelle approche qui combine des stratégies de contrôle et de communication. Toutes les solutions son validées à l’aide de simulations et maquettes d’entraînement / We address security issues in cyber-physical industrial systems. Attacks against these systems shall be handled both in terms of safety and security. Control technologies imposed by industrial standards already cover the safety dimension. From a security standpoint, the literature has shown that using only cyber information to handle the security of cyber-physical systems is not enough, since physical malicious actions are ignored. For this reason, cyber-physical systems have to be protected from threats to their cyber and physical layers. Some authors handle the attacks by using physical attestations of the underlying processes, f.i., physical watermarking to ensure the truthfulness of the process. However, these detectors work properly only if the adversaries do not have enough knowledge to mislead crosslayer data. This thesis focuses on the aforementioned limitations. It starts by testing the effectiveness of a stationary watermark-based fault detector, to detect, as well, malicious actions produced by adversaries. We show that the stationary watermark-based detector is unable to identify cyber-physical adversaries. We show that the approach only detects adversaries that do not attempt to get any knowledge about the system dynamics. We analyze the detection performance of the original design under the presence of adversaries that infer the system dynamics to evade detection. We revisit the original design, using a non-stationary watermark-based design, to handle those adversaries. We also propose a novel approach that combines control and communication strategies. We validate our solutions using numeric simulations and training cyber-physical testbeds

Cette thèse est dédiée à l'analyse de stabilité des systèmes à pas d'échantillonnage variable et à la commande dynamique de l'échantillonnage. L'objectif est de concevoir des lois d'échantillonnage permettant de réduire la fréquence d'actualisation de la commande par retour d'état, tout en garantissant la stabilité du système.Tout d'abord, un aperçu des récents défis et axes de recherche sur les systèmes échantillonnés est présenté. Ensuite, une nouvelle approche de contrôle dynamique de l'échantillonnage, "échantillonnage dépendant de l'état", est proposée. Elle permet de concevoir hors-ligne un échantillonnage maximal dépendant de l'état défini sur des régions coniques de l'espace d'état, grâce à des LMIs.Plusieurs types de systèmes sont étudiés. Tout d'abord, le cas de système LTI idéal est considéré. La fonction d'échantillonnage est construite au moyen de polytopes convexes et de conditions de stabilité exponentielle de type Lyapunov-Razumikhin. Ensuite, la robustesse vis-à-vis des perturbations est incluse. Plusieurs applications sont proposées: analyse de stabilité robuste vis-à-vis des variations du pas d'échantillonnage, contrôles event-triggered et self-triggered, et échantillonnage dépendant de l'état. Enfin, le cas de système LTI perturbé à retard est traité. La construction de la fonction d'échantillonnage est basée sur des conditions de stabilité L2 et sur un nouveau type de fonctionnelles de Lyapunov-Krasovskii avec des matrices dépendant de l'état. Pour finir, le problème de stabilisation est traité, avec un nouveau contrôleur dont les gains commutent en fonction de l'état du système. Un co-design contrôleur/fonction d'échantillonnage est alors proposé / This PhD thesis is dedicated to the stability analysis of sampled-data systems with time-varying sampling, and to the dynamic control of the sampling instants. The main objective is to design sampling laws that allow for reducing the sampling frequency of state-feedback control for linear systems while ensuring the system's stability.First, an overview of the recent problems, challenges, and research directions regarding sampled-data systems is presented. Then, a novel dynamic sampling control approach, "state-dependent sampling", is proposed. It allows for designing offline a maximal state-dependent sampling map over conic regions of the state space, thanks to LMIs.Various classes of systems are considered throughout the thesis. First, we consider the case of ideal LTI systems, and propose a sampling map design based on the use of polytopic embeddings and Lyapunov-Razumikhin exponential stability conditions. Then, the robustness with respect to exogenous perturbations is included. Different applications are proposed: robust stability analysis with respect to time-varying sampling, as well as event-triggered, self-triggered, and state-dependent sampling control schemes. Finally, a sampling map design is proposed in the case of perturbed LTI systems with delay in the feedback control loop. It is based on L2-stability conditions and a novel type of Lyapunov-Krasovskii functionals with state-dependent matrices. Here, the stabilization issue is considered, and a new controller with gains that switch according to the system's state is presented. A co-design controller gains/sampling map is then proposed