WorldCat Identities

Le Gorrec, Yann

Overview
Works: 31 works in 42 publications in 2 languages and 47 library holdings
Roles: Opponent, Thesis advisor, Other, Author
Publication Timeline
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Most widely held works by Yann Le Gorrec
Commande des systèmes multidimentionnels by Caroline Chiappa( Book )

1 edition published in 2004 in French and held by 3 WorldCat member libraries worldwide

Commande modale robuste et synthèse de gains autoséquencés approche multimodèle by Yann Le Gorrec( Book )

2 editions published in 1998 in French and held by 3 WorldCat member libraries worldwide

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
Port-Hamiltonian modeling of fluid-structure interactions in a longitudinal domain by Luis Alejandro Mora Araque( )

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

Fluid-structure interaction (FSI) is a multi-physics problem (with multiple physic domains) that study the reciprocal action between a structure and a fluid flow through a coupling surface or interface. Mathematically, Fluid-structure interaction is described by a set of differential equations and boundary conditions, obtained by an Euler-Lagrange formulation and the Navier-Stokes equations, which belong to the structure an fluid domains respectively. The behavior of FSI can be studied through numerical solutions using finite elements or finite differences methods. An alternative to Euler-Lagrange in the modeling of the energy-conserving physical systems is the port-Hamiltonian framework where the system dynamics are described through a non-negative function that represents the total stored energy in the system, called Hamiltonian H. The port-Hamiltonian framework allows the modeling of the energy transfer between systems in different physical domains. An interesting example of a FSI is the voice production mechanism of the vocal folds, where the intraglottal airflow generates a vibration cycle that produces the phonation. In this context, numerical models of the vocal folds are relevant to explore the effects of certain therapeutic or surgical procedures. In recent years there has been a growing interest in the study of energy flux in the glottis for analysis of pathophysiology of vocal disorders. The study of this kind of multi-physics system can be extended to other FSI system where a fluid moving in a longitudinal domain interacts with a mechanical system that move in the transversal dimension. In this thesis, a scalable finite-dimensional model for FSI systems will be developed. The division of fluid-structure problem into n interconnected sub-systems described by finite-dimensional models, provide an alternative to the traditional infinite-dimensional formulation. In addition, the use of port-Hamiltonian framework to describe the dynamics allows an adequate characterization of the energy flux in the system. Thus, the aim of this study develop a scalable finite-dimensional model focused in the energy flux for fluid-structure systems in a longitudinal domain with application to vocal folds
Contrôle frontière de l'équation des ondes avec amortissement distribué by Christophe Roman( )

1 edition published in 2018 in English and held by 2 WorldCat member libraries worldwide

This thesis is concerned by the boundary control of the one dimensional wave equation, which can be used to model a string (like a guitar string). The objective is to act at one boundary to control and stabilize the otherboundary which is considered to be an unstable dynamic boundary condition. This thesis suggests answers to both following questions:Consider that the unstable dynamics boundary condition has some unknown parameters. Is a nonlinear adaptive control law still performing efficiently, if the viscous damping taken equal to zero for its design is no longer neglected?How can we take into account the in-domain damping in order to stabilize the wave equation subject to dynamic boundary conditions?This thesis suggests a method to derive a Lyapunov analysis in order to prove the robustness mismatch ofparticular nonlinear adaptive control law as the answer of the first question. Then using infinite dimensionalbackstepping technique we develop feedback control law that exponentially stabilize the considered wave equation
Commande et stabilité des systèmes commutés : Application Fluid Power by Omar Ameur( Book )

2 editions published in 2015 in French and held by 2 WorldCat member libraries worldwide

This work focuses on the control and stability analysis of an electro-pneumatic system, i.e. a linear pneumatic cylinder controlled by two servo valves regulating the mass flow entering each chamber of the actuator. The general problem is motivated by the appearance of stick-slip on the electro-pneumatic system, hardly taken into account by the current studies in automatic control. This problem, encountered throughout the years, concerns all mono- and multidimensional linear and non-linear controls systems studied at the laboratory. In pneumatic cylinders, the phenomenon consists in a displacement of the rod a while after it has come to a rest ; this is due to the fact that the force acting on the rod initially becomes smaller that the threshold which is necessary for a motion, and then this threshold is overcome later on. In this case, stick-slip is caused by the presence of dry friction and by the pressure dynamics in the chambers, which continue to evolve (integrating the net incoming mass flow from the servovalves) even after the rod has stopped. The first part of this thesis proposes a nonlinear switching control law in order to avoid stick-slip on pneumatic cylinder, taking into account with the variations of dry friction that may occur at any time causing this phenomenon. This technique is implemented and its effectiveness is recognized. The greatest part of this thesis deals with the stability analysis of the pneumatic cylinder with its switched control law. The presence of dry friction and the application of a switched control law requires an appropriate method for approaching the stability analysis ; this method is based on considering the closed-loop system as belonging to a class of switched systems called piecewise affine systems (PWA). The main difficulty in this approach lies in obtaining adequate Lyapunov functions for proving stability, which turns into an optimization problem under LMI constraints (Linear Matrix Inequality) using the S-procedure. In order to analyze the stability of a PWA system, a first method is proposed allowing the computation of a piecewise quadratic Lyapunov function through an optimization problem under LMI constraints. The methods takes into account, in contrast to conventional methods, that the states might converge not to a single point but to a set of equilibrium points. The proposed approach allows also the study of robustness with respect to parametric variations in the system. A second method is also proposed for the construction of a type of Lyapunov functions called piecewise polynomial, using the “sum of squares” and “power transformation” techniques. This approach proposes less conservative sufficient conditions than those imposed by the piecewise quadratic Lyapunov functions, yielding a more succesfull stability test when for PWA systems featuring sliding modes and parametric variations. In fact, on PWA systems with discontinuous dynamics (which can generate sliding phenomena), piecewise quadratic Lyapunov functions might prove ineffective to prove the stability. Therefore, the results on piecewise quadratic Lyapunov functions are extended in order to compute piecewise polynomial Lyapunov functions of higher order, by solving an optimization problem under LMI constraints. These functions are more general and allow less conservative conditions compared to those formerly developed in the literature. Both of these methods have been applied to the stability analysis of the set of equilibrium points of the pneumatic cylinder, considering first a friction model in saturation form and then a model in relay form with a discontinuous dynamics. The application of the methods is successful, i.e. the robust stability is proven under dry friction threshold variations, with possibility of sliding modes
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
Modelling and stability analysis of flexible robots : a distributed parameter port-Hamiltonian approach by Andrea Mattioni( )

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

The objective of this thesis is to provide a mathematical framework that allows to explicit the dynamical model of a class of flexible mechanisms, to design their control law and to analyze the resulting closed loop asymptotic behaviour. From a mathematical point of view, the flexible parts are distributed parameter systems whose dynamics are described by Partial Differential Equations (PDE), while the dynamics of the rigid parts are described by Ordinary Differential Equation (ODE). Therefore, the total model is described by a mixed set of ODE-PDE (m-PDE-ODE). For studying these dynamic models, this thesis uses the port-Hamiltonian framework combined with the infinite-dimensional semigroup theory.First, we define a rigorous procedure based on the Least Action Principle for deriving the model of mechanisms with possible flexible components, providing several illustrative examples. The general class of nonlinear systems enclosing all the proposed examples is shown to be passive with respect to its mechanical energy. In this class of systems, the distributed parameter parts are modelled as one dimensional boundary control systems.Second, we restrict ourselves to a linear class of m-ODE-PDE systems for which we propose different control laws. We show that the proposed control laws allow achieving asymptotic or exponential stability.Finally, a rotating arm that enters in contact with the external environment is studied in case the link is considered as being both rigid or flexible. Since this system exhibits instant changes in the impact times, we study this problem with the help of switching theory applied to infinite dimensional systems
Robust control for manipulation inside a scanning electron microscope by Marcelo Gaudenzi de faria( Book )

2 editions published in 2016 in English and held by 2 WorldCat member libraries worldwide

This work studies the nano-positioning problem inside the scanning electron microscope (SEM). To acquire fast and accurate positional information, a dedicated setup was implemented consisting of a vibrometer placed inside the SEM. This approach differs from methods based on image processing, as it allows to capture real-time data on the dynamic behavior of structures. In a first study, the mechanical disturbances acting inside the microscope's vacuum chamber were characterized and its sources were identified. This demonstrated how external mechanical vibrations and acoustic noises can largely influence the components inside the SEM through mechanical coupling, limiting the effective positioning precision of manipulators. Next, a commercial micro-gripper was studied, both in air and in vacuum, and the differences between its response were highlighted. This allowed to obtain two dynamic models for this end-effector, one for each environment. Two control laws were proposed (H-infinity control and Extended State Observer based control) for the system, to obtain a real-time, precise positioning in the vacuum environment and to attenuate the effects of the external mechanical disturbances. Results were demonstrated through simulation and experimental validation
Stratégies de modélisation et de commande des microsystèmes piézoélectriques à plusieurs degrés de liberté by Didace Habineza( )

2 editions published in 2015 in French and held by 2 WorldCat member libraries worldwide

Piezoelectric actuators are among the most used tools in many applications at micro/nano-scale (micromanipulation,microassembly, micropositioning, etc). From a functional perspective, there exist mono-axis actuators(which are made to bend in one direction) and multi-axis actuators (which provide deflections in different directions).The popularity of piezoelectric actuators is especially due to their high resolution (nanometric resolution),the large bandwidth (greater than 1kHz possible), the low electrical power consumption, the high force density,the ease of integration in positioning systems, etc. However, piezoelectric actuators are characterized by hysteresisand creep nonlinearities, badly damped vibrations and they are sensitive to the variation of ambient conditions(especially to the temperature variation). In addition, multi-axis actuators exhibit cross-couplings betweentheir axis. This thesis proposes novel strategies for modeling and control of multi-axis piezoelectric actuators,with the aim to counteract the aforementionned problems. These strategies are grouped into two categories.The first category concerns feedback control techniques. These techniques are the most suitable to ensurethe robustness and a high level of precision for piezoelectric actuators. However, at the micro/nanoscale, thesetechniques are limited by the lack of enough physical space to install feedback sensors. The second categoryconcerns the feedforward control techniques. The main advantage of these techniques is related to the factthat, in feedforward control schemes, feedback sensors are not needed for tracking. This allows to achieve ahigh degree of packageability and the cost reduction. In this thesis, we first propose multivariable modelingand feedforward control techniques. Then, we analyse the effects of temperature variation on piezoelectricactuators and we propose feedforward and feedback control techniques for these effects. Finally, a feedbackstrategy based on decoupling techniques with an aim to reduce the order of feedback controllers for multi-axispiezoelectric actuators, is proposed. All these modeling and control strategies are experimentally applied on apiezoelectric tube actuator
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
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
Commande robuste et optimale via les techniques par intervalles pour le contrôle de microsystèmes by Mounir Hammouche( )

2 editions published in 2018 in English and held by 2 WorldCat member libraries worldwide

Piezoelectric actuators are widely used at micro/nanoscale because of their simpleconfiguration, high resolution (sub-nanometric), high speed (large bandwidth upto 1kHz), and high force density. However, they are characterized by some nonlinearitiessuch as hysteresis, internal friction and creep,...etc. These characteristicsconsiderably impact the dynamics of the piezoactuators which makes the controlof these systems not a trivial task. Various robust controllers have been developedto control piezoelectric actuators. These include high gain feedback approach, H1approach, disturbance observer based control approach,...etc. Those techniquesdemonstrated a significant improvement of the control performance, but they oftenderive controllers with high-order which are difficult for implementation. Tobypass this limitation, we focus on the thesis on combining interval analysis withclassical controller design techniques to obtain a low order controllers. The mainadvantage of intervals is that they permit to model parametric uncertainties easilyby bounding them. Furthermore, the process of modeling the system uncertaintiesby intervals makes the synthesis of robust controller with low order relatively easy.The state of the art on the use of interval techniques to design and derive robustcontrollers for uncertain system can be divided into two categories: intervaltransfer functions based approaches and interval state-space representation basedapproaches. Interval transfer functions based designs have been widely used tomodel and to control SISO (Single Input single Output) systems subjected to uncertainties.These approaches make the synthesis of robust controllers for suchsystems easy with providing good performance. However, the current work thatuse interval transfer functions are limited to systems in SISO case. In the otherside, the state-space based approaches have been shown to be well adapted tosynthesis robust controllers for multivariable systems. Nevertheless, the excitingworks are limited to systems with state and input matrices of special structures.Furthermore, they address only the degree of stability of the closed-loop systemwithout discussing performance specification. In order to make the design of robustcontroller using interval state-space approach possible for any interval state-spacestructure, this thesis will explore the interval state-space control design using robustpole assignment technique. This proposed approach will guarantee the stability and the desired performance of the closed-loop system also it allows to obtaina low order controller.For this matter, an algorithm based on Set Inversion Via Interval Analysis(SIVIA) combined with interval eigenvalues computation is proposed to seek for aset of robust gains. This recursive SIVIA-based algorithm allows to approximatewith subpaving the set solutions [K] that satisfy the inclusion of the eigenvaluesof the closed-loop system in a desired region in the complex plan. Furthermore,simple algorithms are proposed to find the optimal feedback gains among the rangeof robust gains [K] as well as the range of the gains that satisfy input constraints,all with the help of interval analysis. Finally, in order to improve the controllerperformance, we were directed our attention to nonlinear control approaches andespecially interval sliding mode control (ISMC) design using interval observers.The effectiveness of the proposed approaches are tested by a real experimentationon several platforms developed in our laboratory to achieve robust performance
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
Stabilization of a class of nonlinear systems with passivity properties by Luis Pablo Borja Rosales( )

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

In this thesis we address the problem of stabilization of nonlinear systems. In particular, we focus on models where the energy plays a fundamental role. This energy-based framework is suitable to capture the phenomena of several physical domains, such as mechanical systems, electrical systems, hydraulic systems, etc. The starting point in the proposed controllers are the concepts of passive system, passive outputs and energy (storage) functions. In this work we study two classes of dynamical systems, namely port-Hamiltonian (PH) and Euler-Lagrange (EL), which are suitable to represent many physical processes. A first step towards the controller design is to show the passivity of the PH systems and the characterization of their passive outputs. Thereafter, we explore the use of the different passive outputs in two well-known passivity-based control (PBC) techniques, that is control by interconnection (CbI) and energy balancing (EB), and we compare the obtained results in both approaches. In addition, we propose a novel methodology in which the controller consists in a proportional (P), an integral (I) and, possibly, a derivative (D) term of the passive output. In this approach the energy of the closed-loop system is shaped without the necessity of solving partial differential equations (PDEs). We analyze the scenario of the PID controller using the different passive outputs previously characterized. Finally, we apply a PID-PBC scheme recently proposed in the literature to a complex mechanical system, namely an ultra flexible inverted pendulum, which is represented as a constrained EL model. The controller design, the stability proof, as well as simulations and experimental results are presented to show the applicability of this technique to physical systems
Stabilization of infinite dimensional port-Hamiltonian systems by nonlinear dynamic boundary control( )

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

Abstract: The conditions for existence of solutions and stability, asymptotic and exponential, of a large class of boundary controlled systems on a 1D spatial domain subject to nonlinear dynamic boundary actuation are given. The consideration of such class of control systems is motivated by the use of actuators and sensors with nonlinear behavior in many engineering applications. These nonlinearities are usually associated to large deformations or the use of smart materials such as piezo actuators and memory shape alloys. Including them in the controller model results in passive dynamic controllers with nonlinear potential energy function and/or nonlinear damping forces. First it is shown that under very natural assumptions the solutions of the partial differential equation with the nonlinear dynamic boundary conditions exist globally. Secondly, when energy dissipation is present in the controller, then it globally asymptotically stabilizes the partial differential equation. Finally, it is shown that assuming some additional conditions on the interconnection and on the passivity properties of the controller (consistent with physical applications) global exponential stability of the closed-loop system is achieved
Contribution à l'élaboration d'un outil de simulation de procédés de transformation physico-chimique de matières premières issues des agro ressources : application aux procédés de transformation de biopolymères par extrusion réactive by Marie-Amélie de Ville d'Avray( )

1 edition published in 2010 in French and held by 1 WorldCat member library worldwide

The development of biorefineries requires integrating and optimizing plants and handling a large number of material flows and unit operations. The development of a process simulator dedicated to this field would thus be of great interest. This is what we intended to initiate by relying on the example of the oxidation of biopolymers by reactive extrusion. Reactive extrusion is characterized by a strong coupling between flow, heat transfer and reaction kinetics. This coupling depends on the desired reactions. We here intended to elaborate aflexible model, being easily integrated into a static process simulator, and enabling to reach agood compromise between the predictive character of the model and the amount of experiments required to adjust model parameters. Therefore, we adopted a hybrid modelling approach combining a flow description based on ideal reactors and continuum mechanics laws. Flow is modeled as a cascade of continuous stirred tank reactors (CSTR) with possible backflow. Flow rates between CSTRs are calculated using physical laws taking into account the operating conditions and geometric parameters of the equipment. Each CSTR is characterized by a filling ratio, which depends on the operating conditions. The calculation of steady-state filling ratio, pressure and flow rates between the CSTRs is achieved by performing a material balance in each CSTR. Material temperature in each CSTR is calculated through a thermal balance. The chemical modification of the material is described using three reactions: the oxidative depolymerization, the formation of functional groups(carbonyl and carboxyl) and the thermomechanical degradation of the biopolymer induced by heating and shearing. The number-averaged and weight-averaged molecular weight of the biopolymer and the oxidant content in each CSTR are computed simultaneously by applying the moment operation to population balance equations. Viscosity is linked to the mean molecular weight. An iterative algorithm enables to couple material balance, thermal balance and reaction kinetics. The experimental data required for model validation were provided by the experimental platform developed at the CVG (Centre de Valorisation des Glucides,Amiens, France) in the frame of the Synthons program. A method was proposed in order to adjust model parameters with a minimal number of experimental data, enabling to assess the predictive character of the model. Once the parameters were adjusted, the reactive extrusion model enabled to reproduce the experimental results obtained with different raw materials,flow rates, screw rotation speeds, and using two extruders with different size and screw configuration. The integration of the reactive extrusion model into a process simulator - the USIM PAC software - enabled to simplify its implementation. This constitutes a promising step in a perspective of process optimization and scale-up, and enables to simulate a reactive extrusion operation within a global plant simulator
A port-Hamiltonian formulation of flexible structures. Modelling and structure-preserving finite element discretization by Andrea Brugnoli( )

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

This thesis aims at extending the port-Hamiltonian (pH) approach to continuum mechanicsin higher geometrical dimensions (particularly in 2D). The pH formalism has a strong multiphysicscharacter and represents a unified framework to model, analyze and control bothfinite- and infinite-dimensional systems. Despite the large literature on this topic, elasticityproblems in higher geometrical dimensions have almost never been considered. This workestablishes the connection between port-Hamiltonian distributed systems and elasticity problems.The originality resides in three major contributions. First, the novel pH formulationof plate models and coupled thermoelastic phenomena is presented. The use of tensor calculusis mandatory for continuum mechanical models and the inclusion of tensor variablesis necessary to obtain an intrinsic, i.e. coordinate free, and equivalent pH description. Second,a finite element based discretization technique, capable of preserving the structure of theinfinite-dimensional problem at a discrete level, is developed and validated. This methodologyrelies on an abstract integration by parts formula and can be applied to linear and non-linearhyperbolic and parabolic systems. Several finite elements for beams and plates structuresare proposed and tested. The discretization of elasticity problems in port-Hamiltonian formrequires the use of non-standard finite elements. Nevertheless, the numerical implementationis performed thanks to well-established open-source libraries, providing external users withan easy to use tool for simulating flexible systems in port-Hamiltonian form. Third, flexiblemultibody systems are recast in pH form by making use of a floating frame description validunder small deformations assumptions. This reformulation include all kinds of linear elasticmodels and exploits the intrinsic modularity of pH systems
Réseau de PLLs distribuées pour synthèse automatique d'horloge de MPSOCs synchrones by Anton Korniienko( )

1 edition published in 2011 in French and held by 1 WorldCat member library worldwide

The classical clock distribution trees used in the synchronous microprocessor systems in nowadays have several drawbacks such as skew, jitter, frequency limitation, perturbation and disturbance behavioral impact independently of their origin, etc.. These factors, critical for the modern microprocessors, motivate the research of an alternative architecture of the clock generation and distribution system. An example of such alternative architectures is the network of coupled PLLs where the PLLs are geographically distributed on the chip and produce the local clock signals. These local clock signals are then synchronized, in real time, by an exchange of information between the PLLs and by local feedback corrections realized by its controllers. Distributed PLLs network allows overcoming the mentioned limitation encountered for the classical clock distribution system. However, the active nature of this network requires going beyond the scope of usual stand-alone PLL design methods. Indeed, the dynamical aspects of the feedback loops and the transformations of the signal inside this complex system make the design problem extremely difficult to solve. The main issue consists in ensuring certain properties of the global network as well as local properties of each subsystem PLL because those properties may change drastically from independent stand-alone PLL designed with standard tools and methods. Indeed, depending on the network topology, the local properties and global dynamical behavior are not necessarily ensured for the overall network. The main contribution of this PhD thesis is the development of a control law design method for each subsystem (such as PLL) ensuring the desired behavior of the global network. A method for transforming the global design problem to an equivalent local control law design problem is proposed. It is based on the assumption that all subsystems are identical. The relation between the local and global properties is established using advanced Control System Theory tools such as input-output and dissipativity principle. This principle decreases significantly the problem complexity by transforming the design problem into a form that is closed to the design of a stand-alone closed loop system. The proposed method is combined with robust H∞ control and LMI optimization that can be solved efficiently with appropriate algorithms that are well suited for the considered application i.e. the PLLs network synchronization. The proposed approach can be easily generalized to other types of networked system to be controlled
Modelling and control of systems of conservation laws with a moving interface : an application to an extrusion process by Mamadou Lamine Diagne( )

1 edition published in 2013 in English and held by 1 WorldCat member library worldwide

This thesis is devoted to the analysis of Partial Differential Equations (PDEs) which are coupled through a moving interface. The motion of the interface obeys to an Ordinary Differential Equation (ODE) which arises from a conservation law. The first part of this thesis concerns the modelling of an extrusion process based on mass, moisture content and energy balances. These balances laws express heat and homogeneous material transport in an extruder by hyperbolic PDEs which are defined in complementary time-varying domains. The evolution of the coupled domains is given by an ODE which is derived from the conservation of mass in an extruder. In the second part of the manuscript, a mathematical analysis has been performed in order to prove the existence and the uniqueness of solution for such class of systems by mean of contraction mapping principle. The third part of the thesis concerns the transformation of an extrusion process mass balance equations into a particular input delay system framework using characteristics method. Then, the stabilization of the moving interface by a predictor-based controller has been proposed. Finally, an extension of the analysis of moving interface problems to a particular class of systems of conservations laws has been developed. Port-Hamiltonian formulation of systems of two conservation laws defined on two complementary time-varying intervals has been studied. It has been shown that the coupled system is a port-Hamiltonian system augmented with two variables being the characteristic functions of the two spatial domains
 
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