WorldCat Identities

Lefèvre, Laurent (19..-....; professeur en mathématiques appliquées)

Overview
Works: 23 works in 31 publications in 2 languages and 39 library holdings
Roles: Thesis advisor, Opponent, Other, Author
Publication Timeline
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Most widely held works by Laurent Lefèvre
De l'introduction d'éléments fonctionnels au sein de la théorie des bond graphs by Laurent Lefèvre( Book )

3 editions published between 1999 and 2013 in French and held by 3 WorldCat member libraries worldwide

Ce rapport détaille la problématique du couplage entre modèles de dimension infinie (ou à paramètres distribués) et modèles de dimension finie (ou à paramètres localisés). Dans les deux cas, les modèles étudiés sont fondés sur l'analyse des processus de stockage, de dissipation et de transfert d'énergie. Les modèles à paramètres localisés considérés sont des bond graphs. Le premier chapitre s'attache à décrire de manière formelle le processus de modélisation récursive. Cette approche montre qu'aucune hypothèse physique ne s'oppose formellement à la généralisation des éléments constitutifs des bond graphs. Les éléments ainsi généralisés sont définis par des opérateurs liant les efforts et les flux à leurs accès et sont baptisés éléments fonctionnels. De nombreux exemples d'éléments fonctionnels sont passés en revue afin d'illustrer l'intérêt de la problématique de couplage. Le deuxième chapitre aborde le problème de la réduction d'opérateurs linéaires de dimension infinie à des systèmes de dimension finie réalisés par bond graph. La méthode développée fait usage des approximants de Padé pour la réduction proprement dite, puis des propriétés des séries de Stieltjes pour établir le caractère physiquement admissible de leur réalisation. Cette méthode s'applique aux opérateurs de relaxation (et donc notamment à des modèles d'impédance hydraulique fractale pour lesquels elle est étudiée en détail). Le troisième chapitre s'attaque au problème de la généralisation de la notion de passivité aux systèmes linéaires de dimension infinie. La caractérisation de cette propriété, comme dans le cas de dimension finie, conduit à la notion de fonction de transfert positive réelle, et définit ainsi la plus large famille de système linéaire pour lesquels les méthodes de réduction similaire à celle du chapitre 2 peuvent avoir un sens. Enfin, en annexe 2, sont développés quelques résultats préliminaires concernant la réduction d'opérateurs non linéaires à mémoire évanescente. Ceux-ci ouvrent la voie à la généralisation ultérieure de ce travail aux éléments fonctionnels non linéaires
Modélisation de l'acidification de l'océan by Paul Geri( Book )

2 editions published between 2014 and 2016 in French and held by 2 WorldCat member libraries worldwide

Conception et réalisation d'un système efficace de communication et de coordination au sein d'une flotille de drones aquatiques de surface by Yoann Hervagault( )

1 edition published in 2019 in English and held by 2 WorldCat member libraries worldwide

The work described herein concerns the development of a communication strategy for a fleet of USVs (Unmanned Surface Vehicles). This project's aim is to improve the performances of the SPYBOAT system, developed by the French company CT2MC to perform environmental monitoring missions in fresh waters. In order to successfully fulfill their task, autonomous surface vehicles must be able to maintain a reliable communication link. This thesis's goal is twofold and complementary:- propose the design of an antenna dedicated to the particular conditions of an USV environment and contained in the vessel's hull,- take into account the effective radio ranges and the limited onboard computing resources to develop an admissible deployment strategy.First, the system under study is identified through experiments performed in the Bourget Lake. The differential flatness property of the model is also proved for further use in the computation of reference trajectories.Subsequently, the characteristics of the USV are described from a radio-frequency point of view. The environmental conditions involved by the water proximity, the low heights of the antennas and the high density of conductive materials in unmanned systems are very challenging. The selected antenna configuration is a planar antenna array, composed of three elementary semi-circular monopoles. Low-height measurements over the ground in open space, in good agreement with simulations, have proven that the proposed antenna and the currently used wire antennas exhibit good electrical performances. Antennas simulations have shown that the radiation pattern loses its omnidirectional property when placed in the vessel's hull due to the reflexions on the embedded equipment, and multiple antennas are required to maintain a reliable communication link.Finally, an algorithm able to compute a feasible reference trajectory for a fleet of USVs is proposed. The flatness-based optimization algorithm takes into account communication constraints to ensure that none of the agents in the network becomes isolated. The optimization problem is solved offline to reduce the computation task of the embedded controller. Then, the trajectory tracking algorithm is implemented online via an LQR (Linear Quadratic Regulator) controller which has been simulated and successfully experimented under various scenarios over the real platforms of CT2MC. The experimental tests show that the pre-established communication constraints are preserved while minimizing the tracking error
Commande optimale sous contraintes pour micro-réseaux en courant continu by Thanh Hung Pham( )

1 edition published in 2017 in English and held by 2 WorldCat member libraries worldwide

The goals of this thesis is to propose modelling and control solutions for the optimal energy management of a DC microgrid under constraints. The studied microgrid system includes electrical storage units (e.g., batteries, supercapacitors), renewable sources (e.g., solar panels) and loads (e.g., an electro-mechanical elevator system). These interconnected components are linked to a three phase electrical grid through a DC bus and associated DC/AC converters. The optimal energy management is usually formulated as an optimal control problem which takes into account the system dynamics, cost, constraints and reference profiles.An optimal energy management for the microgrid is challenging with respect to classical control theories. Needless to say, a DC microgrid is a complex system due to its heterogeneity, distributed nature (both spatial and in sampling time), nonlinearity of dynamics, multi-physic characteristics, the presence of constraints and uncertainties. Moreover, the power-preserving structure and the energy conservation of a microgrid are essential for ensuring a reliable operation.This challenges are tackled through the combined use of port-Hamiltonian formulations, differential flatness, and economic Model Predictive Control.The Port-Hamiltonian formalism allows to explicitly describe the power-preserving structure and the energy conservation of the microgrid and to connect different components of different physical natures through the same formalism. The strongly non-linear system is then translated into a flat representation. Taking into account differential flatness properties, reference profiles are generated such that the dissipated energy and various physical constraints are taken into account. Lastly, we minimize the purchasing/selling electricity cost within the microgrid using the economic Model Predictive Control with the Port-Hamiltonian formalism on graphs.The proposed control designs are validated through simulation results
Approche hamiltonienne à ports pour la modélisation, la réduction et la commande des systèmes non linéaires à paramètres distribués : application aux écoulements à surface libre by Boussad Hamroun( Book )

2 editions published in 2009 in French and held by 2 WorldCat member libraries worldwide

Une formulation hamiltonienne à ports des écoulements unidimensionnels à surface libre modélisés par les équations de Saint-Venant a été proposée. Des propriétés intéressantes telles que la passivité et la conservation d'énergie découlent naturellement de cette formulation. En utilisant des méthodes de réduction type éléments finis mixtes un modèle hamiltonien à port réduit à été obtenu. Cette réduction dites géométrique à permis de conserver les propriétés dynamiques qualitatives du modèle d'origine. On a montré aussi que le modèle réduit possède des propriétés spectrales et entrées-sorties proches du modèle d'origine. Des lois de commande, permettant de réguler le débit et la hauteur d'eau, ont été synthétisées sur le modèle réduit en utilisant la méthode IDA-PBC et de modelage d'énergie. L'approche de modelage d'énergie à été généralisée sur le modèle en dimension infinie. Des résultats de simulation ainsi que des résultats expérimentaux obtenus sur un micro-canal expérimental ont permis de valider les lois de commande
Planification de mouvement pour les systèmes dynamiques multi-agents dans un environnement variable by Ngo Quoc Huy Tran( )

1 edition published in 2019 in English and held by 2 WorldCat member libraries worldwide

This thesis proposes optimization-based control solutions for the motion planning of multi-agent dynamical systems operating in a variable environment (with static/mobile obstacles and time-varying environmental disturbances).Collision-free paths are planned for the agents through the combined use of set theory (particularly, bounded convex sets), non(-linear) Model Predictive Control (MPC), Potential Field (PF) and graph-based methods. The contributions build on the proposal of repulsive potential field constructions together with on-off barrier functions which describe and, respectively, activate/deactivate the collision-free conditions introduced in a distributed NMPC framework. These constructions are further used for connectivity maintenance conditions among the group of agents while ensuring the tracking of the a priori generated path. Furthermore, a nonlinear disturbance observer is integrated within the control scheme for environmental disturbance rejection.Finally, the results are validated in simulation through comparisons with mixed-integer approaches and over a benchmark for the safe navigation of Unmanned Surface Vehicles (USVs) in the Trondheim fjord, Norway, using real numerical data
Modélisation et analyse des systèmes de commande multi-physiques by Benjamin Vincent( )

1 edition published in 2019 in French and held by 2 WorldCat member libraries worldwide

Par multi-physiques systèmes, nous considérons les systèmes à paramètres distribués gouvernés par des lois de conservation. Ces dernières sont interconnectées par des phénomènes de transports et de couplages distribués. Cette thèse porte sur l'étude et le développement d'outils pour la modélisation et l'analyse de la classe de système pour des fins de commande. L'approche considérée repose sur la formulation géométrique des équations d'état avec la mise en œuvre des structures Hamiltoniennes à port et GENERIC. Ces formulations encodent les lois fondamentales de la physique, comme la première et la seconde loi de la thermodynamique. Les contributions portent sur la formulation structurée de systèmes multi-physiques. Des outils de réduction et de discrétisation pseudo-spectrale géométrique sont utilisés pour obtenir des modèles de commande. Une étude de stabilité et de passivité basée sur la production irréversible d'entropie est également proposée pour cette classe de systèmes. La thèse est motivée par deux applications distinctes : le problème de commande des profils de plasma dans les Tokamaks, et la réjection d'instabilités thermo-acoustiques dans un tube de Rijke. La première application vise à assurer un fonctionnement à l'état d'équilibre d'un réacteur de fusion par confinement magnétique. Les équations décrivant la dynamique du plasma à une échelle macroscopique sont les lois de conservation caractérisant les domaines physiques électromagnétiques et cinétiques (masse, moments et énergies). Des modèles structurés du plasma, avec la réaction de fusion, sont présentés sous forme 3-D, 1-D, et 0-D avec le formalisme Hamiltonien à port. Un modèle thermomagnétique du plasma est formulé avec le formalisme GENERIC ouvert. La seconde application illustre les concepts d'instabilités thermo-acoustiques que l'on retrouve par exemple dans les chambres à combustion. Le tube de Rijke est un tube vertical où une source de chaleur localisée est disposée dans sa partie inférieure. Sous certaines conditions, le processus d'échange de chaleur et le domaine acoustique sont interconnectés par un retour de boucle qui déstabilise le système. Cette instabilité se manifeste par la production d'un son bruyant
Contrôle hiérarchique fiable pour les systèmes multicoptères by Ngoc Thinh Nguyen( )

1 edition published in 2019 in English and held by 2 WorldCat member libraries worldwide

The goal of this thesis is to propose reliable control laws for the motion planning of a multicopter system under constraints and unexpected events (e.g., actuator faults). A hierarchical control architecture which decouples the scheme into position and attitude control is proposed. At the high level the position controller calculates the position error and provides the desired thrust and angles to the attitude controller at the low level to stabilize the system around the desired angles. The scheme's reliability (i.e., ensuring feasibility, stability and constraint validation) is done through a coherent merging of differential flatness, feedback linearization and Nonlinear Model Predictive Control (NMPC). Hence, the main thesis contributions lie in:i) The analysis and design of bounds which characterize the various inputs and states of the system (angle position and velocity, torques, etc.). These are subsequently applied for constrained trajectory design (which combines differential flatness and feedback linearization through the use of B-spline parametrizations).ii) Designs which exploit the ``computed-torque control law'' as local control within an NMPC with recursive feasibility guarantees. We show that avoiding the standard linearizations employed for nonlinear dynamics improves performance (in the sense of reducing the prediction horizon, enlarging the terminal region and reducing the problem's complexity). Further advances relax the requirement of set invariance and even discard the need for terminal stabilizing constraints. Generalizations for similar feedback linearizable systems are discussed.iii) A hierarchical optimization-based FTC (Fault Tolerant Control) scheme to counteract a stuck rotor fault. This is done through control reconfiguration at both high and low levels, coupled with a fault diagnosis mechanism capable of handling fault detection, isolation and estimation.The results are validated over extensive simulations and laboratory experiments involving a nano-quadcopter
Contrôle distribué multi-couche des systèmes complexes avec contraintes de communication : application aux systèmes d'irrigation by Le-Duy-Lai Nguyen( )

1 edition published in 2017 in English and held by 2 WorldCat member libraries worldwide

This thesis presents control problems of irrigation network with communication constraints and a multi-layer approach to solve these problems in a distributed manner. Detailed discussions of each layer with analytical and simulation results are described throughout several chapters. They emphasize the potential interest of the multi-layer approach, more precisely its efficiency and reliability for supervision, multi-objective optimization and distributed cooperative control of complex water transport systems. Conventionally, the first layer to be considered is the hydraulic network composed of free-surface channels, hydraulic structures and mesh subnetwork of pressurized pipes. By coupling the Saint-Venant equations for describing the physics of free-surface fluid and the Lattice Boltzmann method for the fluid simulation, a discrete-time nonlinear model is obtained for channel reaches. The hydraulic structures are usually treated as internal boundaries of reaches and modeled by algebraic relationships between the flow and pressure variables. To enable the exchange of information among the control system's components, a communication network is considered in the second layer. Solving challenging problems of heterogeneous devices and communication issues (e.g., network delay, packet loss, energy consumption) is investigated in this thesis by introducing a hybrid network architecture and a dynamic routing design based on Quality of Service (QoS) requirements of control applications. For network routing, a weighted composition of some standard metrics is proposed so that the routing protocol using the composite metric achieves convergence, loop-freeness and path-optimality properties. Through extensive simulation scenarios, different network performance criteria are evaluated. The comparison of simulation results can validate the interest of this composition approach for dynamic routing. Finally, the third layer introduces an optimal reactive control system developed for the regulatory control of large-scale irrigation network under a Distributed Cooperative Model Predictive Control (DCMPC) framework. This part discusses the implementation of different control strategies (e.g., centralized, decentralized, and distributed strategies) and how the cooperative communication among local MPC controllers can be included to improve the performance of the overall system. Managing divergent (or outdated) information exchange among controllers is considered in this thesis as a consensus problem and solved by an asynchronous consensus protocol. This approach based on the multi-agent system paradigm to distributed control requires each controller to agree with its neighbors on some data values needed during action computation. For simulations, a particular benchmark of an irrigation channel is considered. The comparison of simulation results validate the benefits of the distributed cooperative control approach over other control strategies
Identification des systèmes hamiltoniens à ports by Silviu Medianu( )

1 edition published in 2017 in English and held by 2 WorldCat member libraries worldwide

The objective of this thesis is to develop a specific identification theory for Port Controlled Hamiltonian (PCH) systems. The main reasons to develop this theory comes from their remarkable properties like power conservation and stability under power preserving interconnection (e.g. parallel, series or feedback interconnections). In a first part PCH systems are analysed for structural identifiability using some classical or new techniques: observability/controllability identifiability, direct test, power series expansion or a new power energy approach, defining also a new concept of port identifiability. Further it is proposed a perturbation model by means of the interaction port together with a practical identifiability analysis realized using the controllability and observability concepts. The fourth part presents a new framework for time-discretization of PCH systems in the nonlinear or linear case, by combined discretization of the flows and efforts preserving in the same time their characteristic properties. Also in this part it is proposed a discretization error Hamiltonian to distinguish the continuous-time PCH system from the discrete-time one. The fifth part of the thesis makes an analysis of PCH systems identifiability using the subspace identification approach in the deterministic case, proposing also a new power energy approach in direct connection with the structural identifiability results. In the end are presented the main conclusions, personal contributions and perspectives for future work
Modeling and control of magnetic shape memory alloys using port hamiltonian framework by Nandish Rajpravin Calchand( )

2 editions published in 2014 in English and held by 2 WorldCat member libraries worldwide

Les matériaux actifs sont des matériaux qui réagissent quand on leur applique un champ extérieur comme la température, la lumière, un champ magnétique ou un champ électrique. Ces champs changent les propriétés du matériau comme la longueur, la susceptibilité magnétique ou la permittivité électrique. Ces changements peuvent être utilisé pour faire du travail. Quelques exemples sont les matériaux piézoélectriques, qui changent de longueur quand on applique un champ électrique, les alliages à mémoire de forme qui changent leur longueur sous l'action de la température. Un matériau plus récent qu'on appelle les alliages mémoire de forme magnétique se de forme sous l'action d'un champ magnétique. Dans cette thèse, on utilise ce matériau pour Confectionner un actionneur. Pour ce faire, on utilise la thermodynamique des procédés irréversibles pour modéliser le matériau. La thermodynamique s'avère très versatile pour ce type de matériau car il permet de quantifier l' échange et la transformation d' énergie dans le matériau. Aussi, étant donné que le matériau se comporte d'une façon non-linéaire et hystérique, le cadre énergétique nous permets justement de prendre en compte ces non- linearités. Cette thèse utilise l'approche énergétique notamment les Hamiltonien à ports pour modéliser un actionneur à base d'alliage à mémoire de forme. Cette méthode nous permets aussi de concevoir des lois de commande pour contrôler le matériau
Modélisation Hamiltonienne à ports et commande distribuée de structures flexibles : application aux endoscopes biomédicaux à actionneurs à base de polymère électro-actif by Ning Liu( )

2 editions published in 2020 in French and held by 2 WorldCat member libraries worldwide

This thesis deals with the multiphysical modeling and the distributed control of flexible structures actuated by Ionic Polymer Metal Composite (IPMC) actuators. We firstly propose a model for the IPMC actuator using infinite dimensional port-Hamiltonian formulations in order to tackle the multiphysical and multiscale couplings. Lagrange multipliers are used to handle the mechanical constraints appearing in the actuator. The mechanical structure of the flexible structure is then modeled in 1D with beam models and in 2D with a thin shell model. Secondly, two structure preserving discretization methods are presented and extended to infinite dimensional dissipative port-Hamiltonian system with distributed input. The proposed IPMC actuator model is then discretized using the structure preserving finite differences method on staggered grids and validated on experimental data. Thirdly, we propose an in-domain distributed control law on a simplified model i.e. the vibrating string actuated with patches, that allows to shape the total energy of the system and to inject damping in order to stabilize the overall system with predefined performances
Approche hamiltonienne à ports pour la modélisation, la réduction et la commande des dynamiques des plasmas dans les tokamaks by Ngoc Minh Trang Vu( )

1 edition published in 2014 in English and held by 2 WorldCat member libraries worldwide

The modelling and analysis of the plasma dynamics in tokamaks using the port-Hamiltonian approach is the main project purpose. Thermo-mMagnetohydrodynamics balances have been written in port-Hamiltonian form using Stokes-Dirac interconnection structures and 3D differential forms. A simplified 1D model for control has been derived using quasi-static and symmetry assumptions. It has been proved to be equivalent to a classical 1D control model: the resistive diffusion model for the poloidal magnetic flux. Then a geometric spatial integration scheme has been developped. It preserves both the symplecticity of the Dirac interconnection structure and physically conserved extensive quantities. This will allow coming works on energy-based approaches for the non linear control of the plasma dynamics.An Interconnection and Damping Assignment - Passivity Based Control (IDA-PBC) , the most general Port-Hamiltonian control, is chosen first to deal with the studied Tokamak system. It is based on a model made of the two coupled PDEs of resistive diffusion for the magnetic poloidal flux and of radial thermal diffusion. The used TMHD couplings are the Lorentz forces (with non-uniform resistivity) and the bootstrap current. The loop voltage at the plasma boundary, the total external current and the plasma heating power are considered as controller outputs. Due to the actuator constraints which imply to have a physically feasible current profile deposits, a feedforward control is used to ensure the compatibility with the actuator physical capability. Then, the IDA-PBC controllers, both finite-dimensional and infinite-dimensional, are designed to improve the system stabilization and convergence speed. The proposed works are validated against the simulation data obtained from the Tore-Supra WEST (CEA/Cadarache, France) test case and from RAPTOR code for the TCV real-time control system (CRPP/ EPFL, Lausanne, Switzerland)
Discrétisation et commande frontière de systèmes vibro-acoustiques, une approche hamiltonienne à ports by Vincent Trenchant( )

2 editions published in 2017 in French and held by 2 WorldCat member libraries worldwide

This thesis deals with the boundary control of an acoustic by a network of co-localised sensors/actuators which constitutes a smart skin. In order to cope with this multiphysical problem, we chose to place our study in the framework of port-Hamiltonian systems, a structured approach based on the representation of energy exchanges between different energy domains between different systems of subsystems. We proposed a port-Hamiltonian model of the wave equation interconnected through its boundary to the distributed actuation system, which corresponds to a 2D formulation of the physical problem. We developed a spatial discretization method based on the use of finite differences on several staggered grids that preserve the port-Hamiltonian structure of the wave equation. This method also permits to easily interconnect the discretized system with other subsystems, which is convenient for instance for control purposes. Its main advantage over other structure preserving methods is its simplicity of implementation which stems from the use of finite differences. In order to control the vibro-acoustic system, we proposed a control law synthesis method for systems governed by two conservation laws in 1D. The originality of this method lies in the fact that it relies on the computation of structural invariants (Casimir functions) exploited in order to modify the structure of the system in closed loop. The conditions of application of these laws on a 2D system are studied and numerical results validate the synthesized control laws
Synthèse de lois de commande à base d'observateurs pour les systèmes à paramètres distribués : une approche Hamiltonienne à ports by Jesús Pablo Toledo Zucco( )

2 editions published in 2021 in English and held by 2 WorldCat member libraries worldwide

L'approche Hamiltonienne à ports s'est avérée être particulièrement bien adaptée à la modélisation et la commande des systèmes à paramètres distribués (SPD). A titre d'exemples de systèmes entrant dans cette classe de systèmes nous pouvons citer les ondes, les poutres vibrantes, les canaux ouverts, la dynamique des fluides, les structures piézoélectriques et les réacteurs chimiques. Dans cette thèse, nous proposons de nouveaux outils pour la synthèse de lois de commandes basées observateurs d'état (CBOE) pour une classe de SPD. Plus précisément la classe de SPD étudiée dans cette thèse est la classe des systèmes Hamiltoniens à ports linéaires contrôlés à la frontière (SHP-CF). Ce sont des systèmes décrits par des équations différentielles partielles dont les actionneurs et les capteurs sont situés à la frontière de leur domaine spatial. Pour la synthèse, nous utilisons deux approches : early-lumping et late-lumping. Pour la première approche, le système est dans un premier temps discrétisé et la commande basée observateurs est ensuite synthétisé en dimension finie. Pour cela nous proposons deux méthodes, l'une privilégiant la commande, l'autre l'observation. Dans les deux cas, nous combinons des outils de contrôle classiques comme le régulateur quadratique linéaire ou le placement de pôles avec l'approche Hamiltonienne pour garantir la stabilité du système en boucle fermée lorsque le correcteur CBOE d'ordre réduit est appliqué au SHP-CF. Pour la deuxième approche, nous proposons différents observateurs de dimension infinie pour les SHP-CF en fonction des mesures disponibles. Selon le cas considéré, la convergence asymptotique ou exponentielle de l'observateur est prouvée. Enfin, nous proposons quelques résultats préliminaires sur la commande par injection de dissipation ou modelage d'énergie en utilisant les observateurs précédemment étudiés et la corde vibrante comme exemple illustratif
Contributions à la modélisation avec un système multi agent du transfert technologique en Green IT by Christina Herzog( )

1 edition published in 2015 in English and held by 1 WorldCat member library worldwide

Over the past 5 to 10 years, research is numerous on energy reduction in IT (mainly electricity reduction). Several studies indeed alerted the stakeholders and environmental agencies on the urgency of the problem of the energy consumption of large scale infrastructures, like data centres, clouds or simply companies running servers and lots of IT equipment. This awareness moved from a non-so-important issue to major constraints on the operation of these infrastructures. In some cases, the operational costs reach the investment costs, urging new methodologies to appear in order to reduce costs and ecological impact. As of today, new hardware are developed by equipment manufacturers to decrease these costs. Only few and basic techniques are offered at the software and middleware levels out-of-the-box: But in laboratories, some techniques have proven on synthetic data, dedicated workflows or selected applications, to be able to save energy during the lifetime of an infrastructure, in several contexts, from Cloud to HPC in particular. Unfortunately, the transfer (or even the knowledge of the existence) of these techniques to industries is limited to project partners, innovative companies or large private research centres, able to invest time (thus money) on this topic. In my thesis, I investigate the reasons restraining the large adoption of several research results, from the simpler ones to more elaborated ones and I model the ties and interactions between the actors of the technological transfer. The target field has been restricted to Green IT but the methodology and the developed models can be extended to other domains as well. The idea is to identify, on the scale of technical maturity for wider adoption, what is missing and how to increase the speed of the transfer of scientific knowledge. The methodology is based on the following path: First, identifying the actors involved in the process of technology transfer, and understanding their motivations, their means of actions and their limitations. After a study of the state of the art in the domain of innovation diffusion and innovation management, this phase involved the production and the analysis of a dedicated survey targeting researchers and companies, from different size and turnover, restricted to those working in the Green IT field. Identifying each actor is not sufficient since they all interact; therefore their links and the potential of these links for technology transfer have also been studied carefully in a second phase so as to identify the most important ones, with the same methodology with the actors' identification. From these two phases, a multi-agent system (MAS) has been designed
Systèmes couplés d'EDPs, vus comme des systèmes Hamiltoniens à ports avec dissipation : Analyse théorique et simulation numérique by Anass Serhani( )

1 edition published in 2020 in French and held by 1 WorldCat member library worldwide

Dans cette thèse, nous nous intéressons à la modélisation, la discrétisation, la simulation et l'analyse numérique de systèmes d'équations aux dérivées partielles dissipatives, contrôlées et observées à la frontière, via le formalisme des systèmes Hamiltoniens à ports d'interaction, ou port-Hamiltonian systems (pHs). L'objectif principal est de préserver le bilan de puissance des systèmes continus lors du passage au discret. Le problème des ondes et de la chaleur y sont largement étudiés.Dans la première partie de la thèse, nous avons étudié un modèle d'ondes hétérogènes anisotropes avec plusieurs types d'amortissement, interne et frontière. Non seulement nous avons rigoureusement éclairci le cadre fonctionnel du problème, mais nous avons mis en évidence son aspect géométrique, plus précisément, en mettant en lumière la structure de Stokes-Dirac sous-jacente au bilan de puissance. Pour discrétiser le problème des ondes amorties, la récenteméthode des éléments finis partitionnés, ou Partitioned Finite Element Method (PFEM), est adoptée pour sa construction systématique et sans traitement supplémentaire d'une structure de Dirac de dimension _nie, ce qui permet l'obtention naturelle d'une version discrète du bilan de puissance ; la simulation s'effectue par la résolution d'une équation différentielle ordinaire (ODE) linéaire. Cette discrétisation structurée est appliquée aux dissipations internes de type fluide et visco-élastique et aux dissipations frontières de type admittance et impédance.Dans la deuxième partie, nous nous sommes intéressés à un problème de diffusion. Le problème de la chaleur est modélisé, en formulation Hamiltonienne, par plusieurs choix de Hamiltoniens possibles, qui découlent soit de la littérature mathématique, soit de la littérature thermodynamique (énergie interne ou bien entropie). Puisque le problème des ondes et le problème de la chaleur partagent le même opérateur de structure, la discrétisation du problème de diffusion hérite d'un grand nombre de raisonnements faits dans la première partie. Néanmoins, le système discret obtenu est alors une équation différentielle algébrique (DAE), linéaire ou bien non-linéaire. La méthode PFEM retenue dans ce travail démontre son efficacité par sa capacité à mimer, au niveau discret, la diffusion bien connue de l'équation de la chaleur, mais également les premier et second principes de la thermodynamique (selon le Hamiltonien choisi lors de la modélisation).La troisième partie de la thèse, très originale, est consacrée à l'analyse numérique de la méthode de discrétisation proposée. La convergence du schéma numérique est démontrée pour des configurations multiples de familles d'éléments finis sur le modèle des ondes de la première partie, et les ordres obtenus sont vérifiés numériquement. En particulier, la configuration optimale des familles d'éléments finis, c'est-à-dire la minimisation du nombre de degrés de liberté pour un ordre de convergence donné, est obtenue en corollaire. La simulation numérique, n-dimensionnelle, des problèmes étudiés a donné lieu à des codes scientifiques développés en Python. Ces derniers sont adressés à destination, à la fois, des utilisateurs novices et des développeurs intéressés pour améliorer les codes ou pour les adapter à d'autres modèles
Recent advances in regional controllability of cellular automata by Sara Dridi( )

1 edition published in 2019 in English and held by 1 WorldCat member library worldwide

The issue addressed in this thesis concerns the controllability of a class of discrete spatio-temporal systems named cellular automata (CA). The purpose of this study is to highlight new ways to prove the controllability of complex systems. Morespecifically, this thesis focuses on regional controllability which consists in restricting the study to a subregion of the domain where the system will have to achieve a given objective through targeted actions. The case of Boolean CA have been particularly examined throughout this thesis. The first part is devoted to the study of the problem of the regional controllability of deterministic CAs when the actions are exerted on the boundaries of the controlled region. A first approach that we used relies on Markov chains and controllability is characterized by establishing a matrix similar to their transition matrix using the definitions of a regular and ergodic chain. This study has been extended to the case of probabilistic CAs that are widely used tomodel many real phenomena. The same problem has been apprehended using tools of graph theory. We proposenecessary and sufficient conditions for the regional controllability of deterministic CAs using the notions of Hamiltonian circuit and strongly connected component. The control that ensures regional controllability is defined through a preimage algorithm.The second part is devoted to the problem of the boundary regional controllability of Boolean CAs, which consists of acting on the boundary of the domain in order to reach a desired goal in a target region. We first consider linear CAs for which we givea characterization result using the Kalman condition. We propose an algorithm to determine the control that allows to force the appearance of a desired configuration in the study area. The case of nonlinear CAs was also considered using a preimagesearch algorithm
Modélisation et commande d'interaction fluide-structure sous forme de système Hamiltonien à ports : Application au ballottement dans un réservoir en mouvement couplé à une structure flexible by Flávio Luiz Cardoso-Ribeiro( )

1 edition published in 2016 in English and held by 1 WorldCat member library worldwide

This thesis is motivated by an aeronautical issue: the fuel sloshing in tanksof very flexible wings. The vibrations due to these coupled phenomena can lead to problemslike reduced passenger comfort and maneuverability, and even unstable behavior. Thisthesis aims at developing new models of fluid-structure interaction based on the theory ofport-Hamiltonian systems (pHs). The pHs formalism provides a unified framework for thedescription of complex multi-physics systems and a modular approach for the coupling ofsubsystems thanks to interconnection ports. Furthermore, the design of controllers using pHsmodels is also addressed. PHs models are proposed for the equations of liquid sloshing based on 1D and 2D SaintVenant equations and for the equations of structural dynamics. The originality of the workis to give pHs models of sloshing in moving containers. The interconnection ports are used tocouple the sloshing dynamics to the structural dynamics of a beam controlled by piezoelectricactuators. After writing the partial differential equations of the coupled system using thepHs formalism, a finite-dimensional approximation is obtained by using a geometric pseudospectralmethod that preserves the pHs structure of the infinite-dimensional model at thediscrete level. The thesis proposes several extensions of the geometric pseudo-spectral method,allowing the discretization of systems with second-order differential operators and with anunbounded input operator. Experimental tests on a structure made of a beam connected to atank were carried out to validate both the pHs model of liquid sloshing in moving containersand the pseudo-spectral semi-discretization method. The pHs model was finally used to designa passivity-based controller for reducing the vibrations of the coupled system
Modélisation dynamique d'un système couplé pompe à chaleur - stockage thermique par matériaux à changement de phase : approche systémique et validation expérimentale by Jing Wu( )

1 edition published in 2015 in French and held by 1 WorldCat member library worldwide

In the area of buildings refrigeration, the use of thermal energy storage coupled with heat pump is a significant way for reducing the operating costs and optimizing the design of equipment. A prototype of refrigeration-PCM (Phase Change Material) energy storage system is built and implemented within the framework of the project ACLIRSYS (Advanced Control for Low Inertia Refrigeration Systems), funded by the French National Research Agency. The objective of my PhD thesis is to propose a dynamical physical model for the complete system. Within the evaporator and condenser of the heat pump, the refrigerant can be liquid, vapor or mixture of both, while the storage media can be solid, liquid or a mixture of both. Therefore, it is necessary to consider the discrete events associated to phase changes in order to solve the energy and mass balances in different configurations. In this work, static models are used for the compressor and the expansion valve of the heat pump. The heat exchangers of the heat pump and the storage models are based on a representation of the fluid flows by a cascade of Continuous Stirred Tank Reactors (CSTRs). In order to assure the continuity of system evolution, the switching mechanism between different configurations is established. This switching is performed by matrix operations, which permit to achieve a global and very compact representation of the system. The thermodynamic properties of the refrigerant and their partial derivatives are analytically determined by using an equation of state. Two versions of the model for the storage are proposed. A simplified version where the supercooling is assumed to take place at a constant temperature and a more detailed version based on the population balance equations. Experimental data from the prototype has been used to validate the developed model. Experiments in transient states were performed by varying the operating conditions. These date relate to the functioning of the heat pump alone, the storage alone and the coupled system. A very good agreement between the numerical results and experimental data was obtained
 
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