New Stochastic Geometry Approaches to the Modelling and Analysis of Low and High Frequency Wireless Communication Networks

Monsieur Xiaojun XI
Soutenance de thèse de doctorat le 19 Décembre 2019, 15h00 à CentraleSupelec (Gif-sur-Yvette) Amphi F3-06

Composition du jury:

M. Marco Di Renzo Directeur de recherche-CNRS Directeur de Thèse
Mme Maryline Helard Professeur-IETR Président
M. Jalel Ben-Othman Professeur-CNRS-CentraleSupélec-Université Paris-Saclay and Université Paris 13 Examinateur
M. Jean-Marie Gorce Professeur-INSA-Lyon Examinateur
Mme Lina Mroueh Maître de conférences-ISEP Examinateur
Mme Valeria Loscri Chargé de recherche-Inria Lille-Nord Europe Examinateur
M. Mustapha Benjillali Maître de conférences-INPT-Maroc Rapporteur
M. Laurent Clavier Professeur-Institut Mines-Telecom Rapporteur

Abstract: In this thesis, we have developed new analytical frameworks for analyzing and optimizing future cellular networks with the aid of stochastic geometry and point processes. This thesis provides four main technical contributions.
First, we analyze emerging networks that can communicate by using light instead of radio waves. In this context, we propose an innovative analytical framework that allows us to estimate the coverage probability and the average rate of spatially distributed networks, which are used to gain insight for system optimization.
Second, we propose an innovative methodology for modeling spatially correlated cellular networks by using in-homogeneous point processes. The proposed approach is tested against practical deployment of cellular networks and found to be tractable and accurate. It is applied to the analysis of visible light communication networks, and the impact of spatial correlation is studied.
Third, we tackle the open problem of modeling Massive MIMO cellular networks. We study uplink and downlink cellular networks and propose new upper and lower bounds for the average spectral efficiency, which allow us to identify the optimal number of user to serve in each cell of the network and the impact of several key system parameters.
Fourth, we introduce and analyze the performance of a new interference-aware scheduling algorithm for application to the uplink of cellular networks. The proposed approach is based on muting some users in order to reduce the level of interference. The achievable performance and the user-fairness of the proposed approach are discussed and quantified analytically.


This PhD thesis is supported by the European Commission through the H2020-ETN-5Gaura project under grant 675806

Keywords: Stochastic geometry, visible light communication, in-homogeneous  point process, Massive MIMO, interference awarenesss

A Stochastic Geometry Approach to the Analysis and Optimization of Cellular Networks

Monsieur Jian SONG
Soutenance de thèse de doctorat le 19 Décembre 2019, 10h00 à CentraleSupelec (Gif-sur-Yvette) Amphi F3-06

Composition du jury:

M. Marco Di Renzo Directeur de recherche CNRS Directeur de Thèse
Mme Maryline Helard Professeur - IETR Président
M. Jalel Ben-Othman Professeur-CNRS-CentraleSupélec-Université Paris-Saclay-Université Paris 13 Examinateur
M. Jean-Marie Gorce Professeur - INSA-Lyon Examinateur
Mme Valeria Loscri Chargé de recherche - Inria Lille-Nord Europe Examinateur
Mme Lina Mroueh Maître de conférences - ISEP Examinateur
M. Mustapha Benjillali Maître de conférences - INPT - Maroc Rapporteur
M. Laurent Clavier Professeur - Institut Mines-Telecom Rapporteur

Abstract: The main focus of this thesis is on modeling, performance evaluation and system-level optimization of next-generation cellular networks by using stochastic geometry. In addition, the emerging technology of Reconfigurable Intelligent Surfaces (RISs) is investigated for application to future wireless networks. In particular, relying on a Poisson-based abstraction model for the spatial distribution of nodes and access points, this thesis develops a set of new analytical frameworks for the computation of important performance metrics, such as the coverage probability and potential spectral efficiency, which can be used for system-level analysis and optimization. More specifically, a new analytical methodology for the analysis of three-dimensional cellular networks is introduced and employed for system optimization. A novel resource allocation problem is formulated and solved by jointly combining for the first time stochastic geometry and mixed-integer non-linear programming. The impact of deploying intelligent reflecting surfaces throughout a wireless network is quantified with the aid of line point processes, and the potential benefits of RISs against relaying are investigated with the aid of numerical simulations.

This PhD thesis is supported by the European Commission through the H2020-ETN-5Gaura project under grant 675806.

Keywords: Cellular Networks, Stochastic Geometry, Poisson Point Process, Optimization, Reconfigurable Intelligent Surfaces

Séminaire d'Automatique du plateau de Saclay

Séminaire le 4 Décembre 2019, 10h00 à CentraleSupelec (Gif-sur-Yvette) Salle du conseil du L2S - B4.40
Paolo Mason & Hendra Nurdin

10:00-11:00 Paolo Mason (Chargé de recherche, CNRS, L2S, CentraleSupélec)

Title: Controllability of the Schrodinger equation via adiabatic methods

Abstract: In this presentation I will consider the approximate controllability problem for the bilinear Schrodinger equation. In particular I will focus on the application of adiabatic techniques in presence of conical eigenvalues intersections of the Hamiltonian operator. These methods allow to design, in a constructive way, control laws capable of (approximately) steering the system from an eigenstate of the Hamiltonian to an arbitrary target state (or, more precisely, to an arbitrary density distribution). The relationship between our results and other controllability results for the bilinear Schrodinger equation will be discussed, as well as the connection between adiabatic and singular perturbation techniques. Finally, in order to justify the applicability of the presented results, I will provide physically meaningful classes of Hamiltonian operators
for which eigenvalues intersections are generically conical.

Biography: Paolo Mason was born in Dolo, Italy, in 1978. He received the Laurea degree in mathematics from the University of Padova, Italy, in 2002, and the Ph.D. degree from SISSA, Trieste, Italy, in 2006. Since 2009 he works as a “chargé de recherche” (researcher) for CNRS at the Laboratoire des Signaux et Systèmes, Gif-sur- Yvette, France. His research interests include geometric control theory, quantum control and hybrid systems. 

11:00-12:00 Hendra Nurdin (Senior Lecturer, School of Electrical Engineering and Telecommunications, UNSW, Australia)

Title: Learning nonlinear input-output maps with dissipative quantum systems

Abstract: In this seminar, I will describe a theoretical framework for learning of nonlinear input-output maps with fading memory by dissipative quantum systems, as a quantum counterpart of the theory of approximating such maps using classical dynamical systems. Such a theory can provide the foundation for harnessing of dissipative quantum systems for applications such as nonlinear systems modelling and signal processing. In particular, the theory identifies the properties required for a class of dissipative quantum systems to be universal, in the sense that any input-output map with fading memory can be approximated arbitrarily closely by an element of this class. We then introduce an example class of dissipative quantum systems that is provably universal. Some numerical examples will be presented.

The seminar is based on joint work with J. Chen (Quantum Information Processing, 18(7):198 (2019)) 

Biography: Dr Hendra I. Nurdin received the bachelor's degree in electrical engineering from Institut Teknologi Bandung, Bandung, Indonesia, the master's degree in engineering mathematics from the University of Twente, Enschede, the Netherlands, and the Ph.D. degree in engineering and information science from the Australian National University (ANU), Canberra, ACT, Australia, in 2007. From 2007 to 2011, he was a Research Fellow and then an Australian Research Council APD Fellow with the ANU before joining the University of New South Wales, Australia, in 2012. His research interests include quantum systems, quantum feedback control, stochastic systems and stochastic control, and applications of control theory to microgrids and renewable energy systems. He  is a coauthor, with Naoki Yamamoto, of the Springer research monograph “Linear dynamical quantum systems: Analysis, synthesis, and control” (2017).

Modélisation et commande prédictive flexible de la demande en chauffage des bâtiments raccordés à des réseaux de chaleur

Madame Nadine AOUN
Soutenance de thèse de doctorat le 2 Décembre 2019, 14h00 à CentraleSupelec (Gif-sur-Yvette) Salle du conseil du L2S - B4.40

Composition du jury proposé:

M. Guillaume Sandou Professeur - CentraleSupélec Directeur de Thèse
M. Khalil El Khoury Professeur - Université Libanaise Examinateur
Mme Sihem Guernouti Chargée de Recherche - Cerema Examinatrice
M. Marc Petit Professeur - CentraleSupélec Examinateur
M. Vittorio Verda Professeur - Politechnico di Torino Examinateur
M. Etienne Wurtz Directeur de Recherche - CNRS-CEA-INES Examinateur
M. Bruno Lacarrière Professeur - IMT Atlantique Rapporteur
M. Stéphane Ploix Professeur - Université Grenoble-Alpes Rapporteur
M. Roland Bavière Ingénieur de recherche - CEA Co-encadrant
M. Mathieu Vallée Ingénieur de recherche - CEA Co-encadrant
M. David Canal Ingénieur de Recherche - Ademe Invité

Résumé: La gestion de la demande en chauffage des bâtiments raccordés à des réseaux de chaleur s'effectue au niveau de la sous-station au moyen d'un contrôleur qui détermine la température de départ de l'eau alimentant le circuit de chauffage interne (variable de contrôle).

Dans les stratégies de contrôle classiques, cette variable de contrôle est régie par la température extérieure via une courbe de chauffe : lorsque cette dernière chute, la première est relevée. Ce mode de contrôle est appelé « régulation par loi d’eau ».

En dépit de ses incontestables atouts, parmi lesquels une implémentation simple et une réponse fiable à la demande en chauffage, la régulation par loi d’eau ne tient pas compte de l'inertie thermique du bâtiment et ne permet donc pas une modulation de sa demande.

La modulation de la demande en chauffage se définit comme l'action de contrôle consistant à modifier de manière stratégique et raisonnable les conditions de confort thermique interne à des fins économiques. Il s’agit d’une mesure essentielle dans les stratégies de contrôle flexibles qui envisagent le déplacement des charges et l’effacement des pics pour ainsi permettre un engagement durable des ressources énergétiques favorisant la pénétration de l’énergie renouvelable et de récupération à l’échelle urbaine.

Ces travaux de thèse visent à développer et à évaluer numériquement une stratégie de contrôle prédictif et flexible de la demande en chauffage, basée sur un modèle physique simplifié du système de bâtiment et applicable de manière non intrusive dans les réseaux de chaleur.

Tout d'abord, un simulateur thermique dynamique de bâtiment résidentiel, chauffé par un circuit de radiateurs connecté à une sous-station de réseau de chaleur, est développé. Il permet la définition de plusieurs cas d’études de bâtiments représentatifs du parc immobilier résidentiel Français et constitue l’environnement expérimental virtuel de nos travaux de recherche.

Ensuite, une méthodologie permettant d’obtenir un modèle orienté-contrôle et d’ordre réduit de bâtiment avec son système de chauffage est proposée. Elle commence par la définition de la structure du modèle en se basant sur des connaissances physiques, puis consiste en l'identification des paramètres par optimisation méta-heuristique à l'aide des données générées par le simulateur. La structure du modèle est destinée à capter les dynamiques thermiques à court terme. Ainsi, elle comporte des capacités thermiques pour les éléments à forte inertie thermique : la masse interne et le circuit de chauffage. L'approche d'identification paramétrique évalue la possibilité de réaliser cette tâche en ne s’appuyant que sur des données non intrusives et disponibles au niveau de la sous-station, notamment en s’interdisant d’utiliser des mesures de température intérieure.

Enfin, la stratégie de contrôle prédictif est implémentée pour planifier la température de départ de l'eau de chauffage à partir de prévisions des conditions météorologiques et des variations des prix de l’énergie. Le contrôleur flexible est conçu pour résoudre un problème d’optimisation linéaire sous contraintes, selon le principe de l’horizon fuyant. Il incorpore les équations linéarisées du modèle d’ordre réduit du bâtiment dans la formulation du problème et fait un compromis optimal entre les coûts de consommation d'énergie et l'inconfort thermique, le degré de flexibilité pour la modulation de la demande en chauffage étant défini par l’intermédiaire de paramètres de réglage dédiés.

Cette thèse est cofinancée par l'Agence De l'Environnement et de la Maîtrise de l'Energie (ADEME) et le Commissariat à l´Energie Atomique et aux Energies Alternatives (CEA). Elle est préparée au sein du Laboratoire des Systèmes Energétiques et Démonstrateurs territoriaux (LSED) du CEA et en collaboration avec le Laboratoire des Signaux et Systèmes (L2S), unité mixte de recherche du Centre National de la Recherche Scientifique (CNRS), de l’Ecole CentraleSupélec et de l’Université Paris-Sud.

Mots clés: réseaux de chauffage urbains, modélisation de bâtiments, commande prédictive, identification paramétrique, simulation thermique dynamique, programmation linéaire mixte

Abstract: In District Heating Systems (DHSs), buildings space-heating (SH) demand management takes place at the substation level by means of a controller that determines the supply water temperature to the internal SH circuit (control variable).

In conventional control strategies, this control variable is governed by the outdoor temperature via a heating curve: when the latter drops, the former is raised. This is referred to as Weather-Compensation Control (WCC).

Despite its widely recognized assets which include simple implementation and reliable fulfilment of the SH demand, WCC does not account for the building system thermal inertia, and consequently it does not allow modulation of the demand.

SH demand modulation is the control action of strategically and reasonably altering the indoor thermal comfort conditions for economic benefits. It is a key measure in flexible demand control strategies, which seek loads shifting and peaks shaving to allow sustainable commitment of energy resources in favour of renewable power penetration and waste heat recovery at urban scale.

The work presented in this thesis aims at developing, and numerically evaluating, a flexible Model Predictive Control (MPC) strategy for SH demand, non-intrusively applicable in DHSs.

Firstly, a thermal dynamic simulator of a residential building with a radiator SH circuit connected to a DHS substation is developed. It allows defining multiple case study buildings representative of the French residential stock and constitutes the virtual experimental environment for the research.

Then, a methodology to obtain a control-oriented Reduced-Order Model (ROM) for the building and its SH system is proposed. It starts by defining the ROM structure based on physical knowledge, and proceeds to parameters identification by meta-heuristic optimization using data generated by the simulator. The ROM structure is intended to capture short-term thermal dynamics, thus it features thermal capacitances for elements with considerable thermal inertia: the internal mass and the SH circuit. The parametric identification approach assesses the possibility of achieving this task using strictly non-intrusive data available at the substation level, notably not relying on indoor temperature measurements.

Finally, MPC is implemented to schedule the supply water temperature in anticipation of weather conditions and energy price variations. The flexible controller is designed to solve a constrained linear optimization problem according to the receding horizon principle. It embeds the linearized ROM equations within the problem formulation and makes an optimal trade-off between energy consumption costs and thermal discomfort, the degree of flexibility to modulate SH demand being defined through dedicated tuning parameters.

This PhD thesis is jointly funded by ADEME and CEA. It is prepared at CEA - LSED laboratory in collaboration with L2S, a CNRS - CentraleSupélec - Université Paris-Sud joint laboratory.

Keywords: District heating systems, Building modelling, Model predictive control, parametric identification, thermal dynamic simulation, Mixed-integer linear programming

Séminaire d'Automatique du plateau de Saclay

Séminaire le 29 Novembre 2019, 10h00 à CentraleSupelec (Gif-sur-Yvette) Salle du conseil du L2S - B4.40
Elena Panteley & Ubirajara F. Moreno

10:00-11:00 Elena Panteley (Director of research, CNRS, L2S, CentraleSupélec)

Title: Dynamic consensus in heterogeneous networks

Abstract: In this talk we present an analysis framework for the study of synchronization of nonlinear systems interconnected over networks described by directed graphs.  Systems may have different dynamical models or the same model with different parameters.  We introduce the concept of dynamic consensus and we characterize the synchronization behavior of the network in terms of the stability properties of two interconnected dynamical systems that evolve in orthogonal spaces: one corresponds to the synchronization error dynamics and the second to the so-called emergent dynamics. Such an approach allows not only to formulate conditions for practical asymptotic synchronization of heterogeneous networked systems, but also to characterize their collective behavior.  In the end we present two extensions of the proposed approach to the analysis of networks of Stuart-Landau oscillators.

Biography. Elena Panteley was born in Leningrad, USSR. She received the M.Sc. and Ph.D. degrees in applied mathematics from the State University of St. Petersburg, St. Petersburg, Russia. She is a Director of Research (DR 2) of the French National Centre of Scientific Research (CNRS), Laboratoire de Signaux et Systemes, Yvette, France. From 1986 to 1998, she held a research position with the Institute for Problem of Mechanical Engineering, the Academy of Science of Russia, St. Petersburg. During 1998, she was an Associate Researcher with the Center for Control Engineering and Computation, University of California at Santa Barbara. During 1999, she was with the INRIA Rhone Alpes, Monbonnot, France. She is coauthor of over 90 scientific articles and book chapters. Her research interests include stability of nonlinear time-varying systems, control of electromechanical systems, nonlinear, and robust control.

11:00-12:00 Ubirajara F. Moreno (Professor, Department of Automation and Systems (DAS), Federal University of Santa Catarina (UFSC))

Title: Modelling and Simulation of Online Social Networks

Abstract: From the first Internet-based social networking applications designed to get people in contact and make friends, to social networks made up of over 2 billion users, the combination of communication networks, portable devices and AI has changed the way People interact and make decisions. The extent of this influence could be observed not only in marketing, and social behavior but also in referendums and elections, leading to distortion of democratic manifestations and representations. The aim of this presentation is show that an approach based on Systems & Control could be applied to modelling and analisys of the behavior of social networks, as well as, to assess some regulatory policies. The analysis are based on simulation of this models on small and large scale networks.

Biography: Since 2004, Ubirajara F. Moreno is a professor at the Department of Automation and Systems (DAS) at Federal University of Santa Catarina (UFSC). In the period of 2014 to 2016 he served as Director of the Campus of Blumenau from the Federal University of Santa Catarina. He participated in several national and international cooperation projects (PROCAD, BRAFITEC, CAPES / COFFECUB, ANP-PRH-34, CNPq-CNRS, CAPES / GRICES, CAPES/SIU, among others), having coordinated a project of Cooperation Brazil / Cuba: CAPES / MES, 108/2010: entitled Development of an Embedded System of Low Cost for Industrial Monitoring and Diagnosis and a cooperation project Brazil / Portugal: CAPES / FCT 353/13 entitled PICC - Integrated Controllers and Communications Project for NCS. In 2016 he was the national committee chairman of the 1st IFAC Conference on Cyber-Physical & Human Systems held in Florianópolis. Currently coordinates the BRAFITEC project, Brazil / France, entitled Franco-Brazilian Cooperation Project for the Training of Engineers in the Control and Automation Area, in partnership with CentraleSupelec, EC Nantes, UFRGS and UNICAMP, and participates in a Brazil/Norway project of international cooperation on Modeling and Control Strategies with Application in Offshore Oil and Gas Production . He participated in joint research projects with the industry in the development of monitoring systems (Petrobras, Bosch Rexroth).The research interests of prof. Ubirajara Franco Moreno are: Networked Control Systems, Cooperative Robotics, Systems Monitoring and Human Machine Interaction. From August/2019 to April/2020 he is in a sabbatical stay, at L2S, working with Françoise Lamnabhi-Lagarrigue, on Cyber-Physical and Human Systems (CPHS) interaction in Industry 4.0.

Journée Scientifique Mobilité électrique - Couplage au réseau électrique et stockage

Tue, 11/12/2019 - 16:30
CentraleSupélec - Campus de Paris-Saclay - Bâtiment Bouygues Amphi SC.071



Journée Scientifique Mobilité électrique

Quelques problèmes dans l’analyse et la commande des réseaux électriques avec des charges à puissance constante

Monsieur Juan E. Machado
Soutenance de thèse de doctorat le 22 Novembre 2019, 15h00 à CentraleSupelec (Gif-sur-Yvette) Salle des séminaires du L2S

Composition du jury proposé:

Mr. Romeo Ortega L2S (CNRS, UMR 8506) Directeur de thèse
Mr. Luca Greco Université Paris-Sud (UMR8506) Examinateur
Mr. Robert Griñó Universitat Politècnica de Catalunya Examinateur
Mme Françoise Lamnabhi-Lagarrigue L2S (CNRS, UMR 8506) Examinateur
Mr. John W. Simpson-Porco University of Waterloo Rapporteur
Mr. Aleksandar Stankovic Tufts University Rapporteur


Resumé: La croissante demande d’énergie électrique a conduit à la conception de systèmes électriques de grande complexité où les combustibles fossiles constituent la principale source d’énergie. Néanmoins, les préoccupations environnementales poussent à un changement majeur dans les pratiques de production d’électricité, avec un passage marqué des énergies fossiles aux énergies renouvelables et des architectures centralisées à distribuées. Les problèmes de stabilité dus à la présence de ce qu’on appelle les Charges à Puissance Constante (CPLs) constituent l’un des principaux défis auxquels sont confrontés les systèmes électriques distribués. On sait que ces charges, que l’on trouve couramment dans les installations de technologie de l’information et de la communication, réduisent l’amortissement effectif des circuits qui les alimentent, ce qui peut provoquer des oscillations de tension, voire une chute. Dans cette thèse, les principales contributions sont centrées sur la compréhension et la résolution de divers problèmes rencontrés dans l’analyse et le contrôle de systèmes électriques contenant des CPLs. Les contributions sont énumérées comme suit. (i) Des conditions simplement vérifiables sont proposées pour certifier la non existence d’états en régime permanent pour des réseaux multi-ports, à courant alternatif avec une distribution de CPLs. Ces conditions, qui reposent sur les inégalités matricielles linéaires, permettent d’écarter les valeurs des puissances des charges qui produiraient certainement un effondrement de la tension sur l’ensemble du réseau. (ii) Pour des modèles généraux de certains systèmes électriques modernes, y compris les réseaux de transmission à courant continu haute tension et les microréseaux, il est montré que, si des équilibres existent, il existe un équilibre caractéristique à haute tension qui domine tous les autres. En outre, dans le cas des systèmes d’alimentation en courant alternatif sous l’hypothèse de découplage standard, cet équilibre caractéristique s’avère stable à long terme. (iii) Une classe de systèmes port-Hamiltoniens, dans laquelle les variables de contrôle agissent directement sur l’équation de puissance, est explorée. Il est démontré que ces systèmes sont décalés de manière passive lorsque leurs trajectoires sont contraintes à des ensembles facilement définissables. Ces dernières propriétés sont exploitées pour analyser la stabilité de leurs équilibres intrinsèquement non nuls. Il a également été montré que la stabilité des réseaux électriques à courant continu multiports et des générateurs synchrones, tous deux connectés à des CPLs, peuvent naturellement être étudiée dans le cadre proposé. (iv) Le problème de la régulation de la tension de sortie du convertisseur buck-boost alimentant une CPL non connu est résolu. L’un des principaux obstacles à la conception de commandes linéaires classiques provient du fait que le modèle du système est de phase non minimale par rapport à chacune de ses variables d’état. Cette thèse rapporte un contrôleur adaptatif non linéaire capable de rendre un équilibre souhaité asymptotiquement stable; de plus, une estimation de la région d’attraction peut être calculée. (v) La dernière contribution concerne l’amortissement actif d’un système d’alimentation de petite taille à courant continu avec une CPL. Au lieu de connecter des éléments passifs peu pratiques et énergétiquement inefficaces au réseau existant, l’ajout d’un convertisseur de puissance contrôlé est exploré. La contribution principale rapportée ici est la conception d’une loi de contrôle non linéaire basée sur l’observateur pour le convertisseur. La nouveauté de la proposition réside dans le fait qu’il n’est pas nécessaire de mesurer le courant électrique du réseau ni la valeur de la CPL, soulignant ainsi son applicabilité pratique. L’efficacité du schéma de contrôle est ensuite validée par des expériences sur un réseau à courant continu réel.

Abstract: The continuously increasing demand of electrical energy has led to the conception of power systems of great complexity that may extend even through entire countries. In the vast majority of large-scale power systems the main primary source of energy are fossil fuels. Nonetheless, environmental concerns are pushing a major change in electric energy production practices, with a marked shift from fossil fuels to renewables and from centralized architectures to more distributed ones. One of the main challenges that distributed power systems face are the stability problems arising from the presence of the so-called Constant Power Loads (CPLs). These loads, which are commonly found in information and communication technology facilities, are known to reduce the effective damping of the circuits that energize them, which can cause voltage oscillations or even voltage collapse. In this thesis, the main contributions are focused in understanding and solving diverse problems found in the analysis and control of electrical power systems containing CPLs. The contributions are listed as follows. (i) Simply verifiable conditions are proposed to certify the non existence of steady states in general, multi-port, alternating current (AC) networks with a distributed array of CPLs. These conditions, which are based on Linear Matrix Inequalities, allow to discard the values of the loads’ powers that would certainly produce a voltage collapse in the whole network. (ii) For general models of some modern power systems, including High-Voltage Direct Current transmission networks and microgrids, it is shown that if equilibria exist, then there is a characteristic high-voltage equilibrium that dominates, entry-wise, all the other ones. Furthermore, for the case of AC power systems under the standard decoupling assumption, this characteristic equilibrium is shown to be long-term stable. (iii) A class of port-Hamiltonian systems, in which the control variables act directly on the power balance equation, is explored. These systems are shown to be shifted passive when their trajectories are constrained to easily definable sets. The latter properties are exploited to analyze the stability of their intrinsically non zero equilibria. It is also shown that the stability of multi-port DC electrical networks and synchronous generators, both with CPLs, can be naturally studied with the proposed framework. (iv) The problem of regulating the output voltage of the versatile DC buck-boost converter feeding an unknown CPL is addressed. One of the main obstacles for conventional linear control design stems from the fact that the system’s model is nonminimum phase with respect to each of its state variables. As a possible solution to this problem, this thesis reports a nonlinear, adaptive controller that is able to render a desired equilibrium asymptotically stable; furthermore an estimate of the region of attraction can be computed. (v) The last contribution concerns the active damping of a DC small-scale power system with a CPL. Instead of connecting impractical, energetically inefficient passive elements to the existing network, the addition of a controlled DC-DC power converter is explored. The main contribution reported here is the design of a nonlinear, observer-based control law for the converter. The novelty of the proposal lies in the non necessity of measuring the network’s electrical current nor the value of the CPL, highlighting its practical applicability. The effectiveness of the control scheme is further validated through experiments on a real DC network.

Mots clés: Réseaux électriques, Charges à Puissance Constante, Analyse, Commande

Keywords: Power systems, Constant Power Loads (CPLs), Analysis, Control

Computational characterization of supra-threshold hearing to understand speech-in-noise intelligibility deficits

Séminaire le 20 Novembre 2019, 10h30 à CentraleSupelec (Gif-sur-Yvette) Salle des séminaires du L2S
Emmanuel PONSOT

Séminaire S³

Title: Computational characterization of supra-threshold hearing to understand speech-in-noise intelligibility deficits

Abstract: A largely unresolved problem in hearing sciences concerns the large heterogeneity observed among individuals with similar audiograms (hearing thresholds measured in quiet) in understanding speech in noisy environments. Recent studies suggest that supra-threshold auditory mechanisms (i.e. that operate above detection threshold) play a prominent role in these interindividual differences, but a precise view of where and how distortions arise along the auditory processing hierarchy is lacking. Addressing this problem requires novel approaches that not do simply consider hearing in terms of sensitivity, but in terms of fidelity of encoding. In this talk, I will present a novel methodological framework developed for this purpose, which combines signal-processing with psychoacoustical tests and computational modeling tools derived from system identification methods. I will present and discuss results from several experiments conducted in both normal-hearing and hearing-impaired individuals within this framework to characterize the processing of supra-threshold signals made of spectrotemporal modulations -- broadband noises whose envelope is jointly modulated over time and frequency -- which constitute the most crucial features underlying speech intelligibility. I will then explain how the detailed computational characterization returned from this joined experimental-modeling approach can be used to identify the different components underlying suprathreshold auditory encoding deficits. Overall, this project describes an innovative approach that capitalizes on system-engineering methods to shed an unprecedented light on supra-threshold hearing and its disorders. By integrating the knowledge of how the auditory system operates above the threshold in noisy conditions, this project will generate new avenues for the development of novel audiological procedures and signal-processing strategies for hearing aids.

Biographies: Emmanuel Ponsot was initially trained in Engineering at Ecole Centrale (Lyon), and received a Master degree in Acoustics in 2012. He then turned to Psychoacoustics and Cognitive Sciences and obtained a Ph.D. from Sorbonne Université in 2015 on loudness processing and coding in humans. From 2015 to 2017, he did a first postdoc at IRCAM (Paris), during which he developed new tools to explore the computational bases of Social Cognition in speech prosody. He is currently a post-doctoral researcher at the Laboratoire des Systèmes Perceptifs (ENS, Paris), where he combines experimental and modeling approaches to characterize the auditory mechanisms used to process complex supra-threshold signals in noise, in both normal-hearing individuals and individuals with hearing loss.

Direct sampling method in inverse electromagnetic scattering problem

Sangwoo KANG
Soutenance de thèse de doctorat le 14 Novembre 2019, 10h00 à CentraleSupelec (Gif-sur-Yvette)

Lieu: Bâtiment Breguet - D2.07 (Petit Conseil) - 3 rue Joliot Curie - 91190 Gif-sur-Yvette

Composition du jury:

Mr.Marc Lambert Chargé de recherche CNRS GeePs Directeur de thèse
Mr.Houssem Haddar Directeur de recherche INRIA CMAP Examinateur
Mr.Dominique Lesselier Directeur de recherche CNRS L2S Examinateur
Mr.Mikyoung Lim Professeur Korean Advanced Institute of Science and Technology Examinateur
Mme Amélie Litman Maître de Conférence Université de Marseille Rapporteur
Mr.Matteo Pastorino Professeur Université de Gênes Rapporteur


Résumé: Le problème de l'imagerie non itérative dans le cadre de la diffraction électromagnétique inverse utilisant la méthode d'échantillonnage direct (DSM) est considéré. Grâce à une combinaison de l'expression asymptotique du champ proche ou du champ lointain diffracté et de l'hypothèse de petits obstacles, les expressions analytiques de la fonction d'indicateur DSM sont présentées dans diverses configurations telles que des configurations 2D/3D, mono-/multi-configurations statiques,  à vue limitée/complète et fréquence unique/ diversité en fréquence. Une fois l'expression analytique obtenue, sa structure est analysée et des améliorations proposées. Notre approche est validée à l’aide de données de simulation, et d’expériences le cas échéant. Premièrement, la structure mathématique du DSM à fréquence fixe en 2D dans divers problèmes de diffusion est établie, permettant une analyse théorique de son efficacité et de ses limites. Pour surmonter les limitations connues, une méthode alternative d'échantillonnage direct (DSMA) est proposée. Puis le cas multi-fréquence est investigué en introduisant et en analysant le DSM multi-fréquence (MDSM) et le DSMA multi-fréquence (MDSMA).Enfin, notre approche est étendue aux problèmes de diffraction électromagnétique inverse 3D pour lesquels le choix de la polarisation du dipôle de test est un paramètre clé. De par notre approche analytique, ce choix peut être effectué sur la base de la polarisation du champ incident.

Abstract: The non iterative imaging problem within the inverse electromagnetic scattering framework using the direct sampling method (DSM) is considered. Thanks to the combination of the asymptotic expression of  the scattered near-field or far-field and of the small obstacle hypothesis the analytical expressions of the DSM indicator function are presented in various configurations such as 2D/3D configurations and/or mono-/multi-static configurations and/or limited-/full-view case and/or mono-/multi-frequency case. Once the analytical expression obtained, its structure is analyzed and  improvements  proposed.  Our approach is validated using  synthetic data and experimental  ones when available. First, the mathematical structure of DSM at fixed frequency in 2D various scattering problems is established allowing a theoretical analysis of its efficiency and limitations. To overcome the known limitations an alternative direct sampling method (DSMA) is proposed. Next, the multi-frequency case is investigated by introducing and analyzing  the multi-frequency DSM (MDSM) and the multi-frequency DSMA (MDSMA). Finally,  our approach is extended to 3D inverse electromagnetic scattering problems for which the choice of the polarization of the test dipole is a key parameter. Thanks to our analytical analysis it can be made based on  the polarization of the incident field.

"Séminaire d'Automatique du plateau de Saclay" of iCODE

Séminaire le 25 Octobre 2019, 10h00 à CentraleSupelec (Gif-sur-Yvette) Salle du conseil du L2S - B4.40
Antoine Girard & Sajad Naderi

10:00-11:00 Antoine Girard (L2S, Gif-Sur-Yvette, France)

Title: A Symbolic Control Approach to the Programming of Cyber-Physical Systems

Abstract: Autonomous vehicles, intelligent buildings or robots promise to transform the everyday life of our society in all its dimensions (transport, housing, industry, health, assistance to the elderly ...). These systems are examples of cyber-physical systems (CPS) resulting from the integration of computer components and physical processes. The development of these systems is often complex (due to cyber-physical interactions) and with critical safety requirements.
In this talk, I will present the first steps towards developing a framework for CPS programming that will enable fast and safe development of their functionality through a high-level programming language. The originality of the approach is to consider that programs are not intended to be executed on the digital platform made up of computer components, but on the cyber-physical platform, which additionally includes the physical part of the system. Thus, high-level programs do not specify the behavior of the computer components but directly that of the cyber-physical system. Then, an automatic synthesis tool uses a model of the physical process to generate low-level control algorithms that enforce the specified behavior.
I will introduce a high-level language for CPS directly inspired by the formalism of hybrid automata. Following the paradigm of 'correct by construction synthesis', low-level control algorithms are synthesized by symbolic control techniques. The key concept of symbolic control is that of the symbolic model, which is a dynamic finite state system, obtained by abstracting physical trajectories on a finite set of symbols. When symbolic and physical dynamics are formally linked by a behavioral relation (e.g., simulation or bisimulation), controllers synthesized for the symbolic model using discrete synthesis techniques can be refined to controllers certified for the physical system. I will provide illustrating examples from the domain of autonomous vehicles.

Biography: Antoine Girard is a senior researcher at CNRS and a member of the Laboratory of Signals and Systems. He received the Ph.D. degree in applied mathematics from Grenoble Institute of Technology, in 2004. From 2004 to 2006, he held postdoctoral positions at University of Pennsylvania and Université Grenoble-Alpes. From 2006 to 2015, he was an Assistant/Associate Professor at the Université Grenoble-Alpes. His main research interests deal with analysis and control of hybrid systems with an emphasis on computational approaches, formal methods and applications to cyber-physical systems. Antoine Girard received the George S. Axelby Outstanding Paper Award from the IEEE Control Systems Society in 2009. In 2014, he was awarded CNRS Bronze Medal. In 2015, he was appointed as a junior member of the Institut Universitaire de France (IUF). In 2016, he was awarded an ERC Consolidator Grant. In 2018, he received the first Test of Time Award from the International Conference on Hybrid Systems: Computation and Control and the European Control Award.

11:00-12:00 Sajad Naderi (Eindhoven University of Technology, The Netherlands)

Title: Model order reduction for linear time delay systems based on energy functionals

Abstract: In this talk, I first present a model order reduction approach for asymptotically stable linear time systems with point-wise delays. This approach, which can be regarded as an extension of existing balanced model order reduction techniques for linear delay-free systems, is based on energy functionals that characterize observability and controllability properties of time delay system. This type of approach provides an a priori bound on the reduction error. Moreover, the resulting reduced model is an asymptotically stable time delay system with the same delay-structure as the original model. In the second part of the presentation, I introduce an extended model order reduction technique for time delay systems. This extension is beneficial when the preservation of physical interconnection structures or uncertainties is desired.

Biography: Sajad Naderi received his MSc in control systems from the school of electrical and computer engineering at the University of Tehran, Iran. For his MSc thesis, he worked on the design and implementation of nonlinear adaptive controllers for the speed control of PMSM drives. He is currently pursuing a PhD degree within the dynamics and control group of the mechanical engineering department at Eindhoven University of Technology, The Netherlands. His PhD research focuses on model order reduction of infinite-dimensional systems, with application to managed pressure drilling automation. In the scope of this industrial project, he has spent 1.5 years of his PhD at the Norwegian company Kelda Drilling Controls in Porsgrunn, Norway.

Contribution à l'estimation d'état par méthodes ensemblistes ellipsoidales et zonotopiques

Soutenance de thèse de doctorat le 24 Octobre 2019, 14h00 à CentraleSupelec (Gif-sur-Yvette) Amphi F3-06

Membres du jury :

Mme Cristina STOICA MANIU          CentraleSupélec - L2S          Directrice de thèse
M. Teodoro ALAMO                         Université de Séville            Co-encadrant
M. Eduardo F. CAMACHO                  Université de Séville         Co-encadrant
M. Antoine GIRARD                            CNRS - L2S                          Examinateur
M. Christophe COMBASTEL                Université de Bordeaux      Examinateur
M. Dan SELISTEANU                       Université de Craiova             Rapporteur
M. José Manuel CARO BRAVO               Université de Huelva              Rapporteur
M. Nacim RAMDANI                        Université d'Orléans            Rapporteur


Résumé : Dans le contexte des systèmes dynamiques, cette thèse développe des techniques d'estimation d'état ensemblistes pour des différentes classes de systèmes. On considère pour cela le cas d'un système standard linéaire invariant dans le temps soumis à des perturbations, des bruits de mesure et des incertitudes inconnus, mais bornés. Dans une première étape, une technique d'estimation d'état ellipsoïdale est étendue, puis appliquée sur un modèle d'octorotor utilisé dans un contexte radar. Une extension de cette approche ellipsoïdale d'estimation d'état est proposée pour des systèmes descripteurs. Dans la deuxième partie, nous proposons une méthode fondée sur la minimization du P-rayon d'un zonotope, appliquée à un modèle d'octorotor. Cette méthode est ensuite étendue pour traiter les systèmes affines par morceaux. Dans la continuité des approches précédentes, un nouveau filtre de Kalman sous contraintes zonotopiques est proposé dans la dernière partie de cette thèse. En utilisant la forme duale d'un problème d'optimisation, l'algorithme projète l'état sur un zonotope qui forme l'envelope de l'ensemble des contraintes auxquelles l'état est soumis. La complexité de l'algorithme est ensuite améliorée en remplaçant le zonotope initial par une forme réduite en limitant son nombre de générateurs.

Title : Contribution to ellipsoidal and zonotopic set-membership state estimation

Abstract : In the context of dynamical systems, this thesis focuses on the development of robust set-membership state estimation procedures for different classes of systems. We consider the case of standard linear time-invariant systems, subject to unknown but bounded perturbations and measurement noises. The first part of this thesis builds upon previous results on ellipsoidal set-membership approaches. An extended ellipsoidal set-membership state estimation technique is applied to a model of an octorotor used for radar applications. Then, an extension of this ellipsoidal state estimation approach is proposed for descriptor systems. In the second part, we propose a state estimation technique based on the minimization of the P-radius of a zonotope, applied to the same model of the octorotor. This approach is further extended to deal with piecewise affine systems. In the continuity of the previous approaches, a new zonotopic constrained Kalman filter is proposed in the last part of this thesis. By solving a dual form of an optimization problem, the algorithm projects the state on a zonotope forming the envelope of the set of constraints that the state is subject to. Then, the computational complexity of the algorithm is improved by replacing the original possibly large-scale zonotope with a reduced form, by limiting its number of generators.

Mots-clés : Estimation d'état ensembliste, inégalité matrice linéaire, zonotopes, ellipsoides

Keywords : Set-membership state estimation, linear matrix inequality, zonotopes, ellipsoids


Séminaire Scube CentraleSupélec

Séminaire le 18 Octobre 2019, 11h00 à CentraleSupelec (Gif-sur-Yvette) Salle des séminaires du L2S
Diarra FALL

Title: Test d'hypothèses bayésien non paramétrique et application à la modélisation de la zone du langage


Abstract: Dans cet exposé je parlerai de modèles bayésiens non paramétriques et de tests d'hypothèses, avec pour exemple d'application, un travail en cours avec le centre hospitalier régional d'Orléans portant sur l'estimation de la zone contrôlant le langage chez des patients ayant eu un AVC.

Biographies: I joined the University of Amiens (France) where I was post-graduated in theoretical Mathematics. Afterward, I received a Master research degree in Data processing from the UVSQ, UPMC & Telecom Sud Paris. I obtained my Ph.D. degree in Image processing from the University Paris Sud. From 2007 to 2011, I did my doctoral research in the Laboratory of Modeling Simulation and Systems at CEA (French Atomic Energy Commission), and in the Laboratory of Signals and Systems (Supélec), in collaboration with Frédéric Joliot Hospital Service. In 2008-2010, I was a teaching assistant in Statistics and Numerical Analysis at ENSIIE Evry. From 2011 to 2013, I was an assistant professor of Mathematics at the University Paris Descartes. Since September 2013, I am an associate professor of Mathematics at the University of Orleans.

«Trajectoires optimales et commande prédictive d'un quadricoptère pour la réalisation de plans de vol cinématographiques » « Optimal trajectory planning and predictive control for cinematographic flight plans with quadrotors »

Soutenance de thèse de doctorat le 18 Octobre 2019, 10h00 à

  CentraleSupélec (Gif-sur-Yvette) - Bâtiment Bouygues - Amphi SC.071


Membres du jury:

Mme Cristina STOICA MANIU            L2S/CentraleSupélec Directrice de thèse
M. Mathieu BABEL  Parrot Drones Co-encadrant
Mme Sihem TEBBANI L2S/CentraleSupélec Co-encadrante
M. Nicolas MARTIN Parrot Drones Co-encadrant - invité
M. Sylvain BERTRAND ONERA Examinateur
M. Pedro CASTILLO-GARCIA Université de Technologie de Compiègne Examinateur
M. Nicolas PETIT  Mines ParisTech Rapporteur
M. Didier THEILLIOL Université de Lorraine Rapporteur


Résumé: Cette thèse s'intéresse à la réalisation autonome de plans de vol cinématographiques par un quadrotor équipé d'une caméra. Ces plans de vol consistent en une série de points de passage à rejoindre successivement, en adoptant diverses méthodes de prise de vue et en respectant des références de vitesse ainsi que des couloirs de vols. Une étude approfondie de la dynamique du quadrotor est tout d'abord proposée, et utilisée pour construire un modèle linéarisé du drone autour de l'équilibre de vol stationnaire. L'analyse de ce modèle linéaire permet de mettre en évidence l'impact de l'inertie des rotors du drone dans sa dynamique, notamment l'apparition d'un comportement à non minimum de phase en roulis ou tangage, lorsque les moteurs sont inclinés. Dans un second temps, deux algorithmes de génération de trajectoires lisses, faisables et adaptées à la cinématographie sont proposés. La faisabilité de la trajectoire est garantie par le respect de contraintes sur ses dérivées temporelles, adaptées pour la cinématographie et obtenues grâce à l'étude du modèle non linéaire du drone. Le premier repose sur une optimisation bi-niveaux d'une trajectoire polynomiale par morceaux, dans le but de trouver la plus rapide des trajectoires à minimum de jerk permettant d'accomplir la mission. Le second algorithme consiste en la génération de trajectoires B-spline non-uniformes à durée minimale. Pour les deux solutions, une étude de l’initialisation du problème d'optimisation est présentée, de même qu'une analyse de leurs avantages et limitations. Pour ce faire, elles sont notamment confrontées à des simulations et vols extérieurs. Enfin, une loi de commande prédictive est proposée pour asservir les mouvements de la caméra embarquée de manière douce mais précise.

Abstract: This thesis deals with the autonomous performance of cinematographic flight plans with camera equipped quadrotors. These flight plans consists in a series of waypoints to join while adopting various camera behaviors, along with speed references and flight corridors. First, an in depth study of the nonlinear dynamics of the drone is proposed, which is then used to derive a linear model of the system near the hovering equilibrium. An analysis of this linear model allows us to emphasize the impact of the inertia of the propellers when the latter are tilted, such as the apparition of a non minimum phase behavior of the pitch or dynamics. Then, two algorithms are proposed to generate smooth and feasible trajectories suited for cinematography. The feasibility of the trajectory is ensured by constraints on its time derivatives, suited for cinematography and obtained with the use of the nonlinear model of the drone. The first algorithm proposed in this work is based on a bi-level optimization of a piecewise polynomial trajectory and try to find the fastest feasible minimum jerk trajectory to perform the flight plan. The second algorithm consists in the generation of feasible, minimum time, non uniform B-spline. For both solutions, a study of the initialization of the optimization problem is proposed, as well as a discussion about their advantages and limitations. To this aim, they are notably confronted to simulations and outdoor flight experiments. Finally, a predictive control law is propose to smoothly but accurately control the on-board camera.





Séminaire d'Automatique du plateau de Saclay

Séminaire le 17 Octobre 2019, 10h00 à CentraleSupelec (Gif-sur-Yvette) Salle du conseil du L2S - B4.40
Islam Boussaada & Ludovic Sacchelli

10:00-11:00 Islam Boussaada (Inria Saclay, Equipe DISCO & L2S, Gif-Sur-Yvette)

Title: Coalescence and Splitting Mechanisms of Spectral Values and their Effect on Stability: Towards a New Framework for Reduced Complexity Pole-placement Design for Time-Delay Systems

Abstract: For linear delay-differential equations, a question of ongoing interest is to determine conditions on the equation parameters that guarantee exponential stability and stabilization of solutions. This talk starts by a review of an old design method for time-delay systems called finite pole-placement. Its advantages and limitations shall be stressed. Next, some recent results showing a link between the stable manifold and the manifold corresponding to a given multiplicity of a spectral value shall be presented, hence enabling a spectral abscissa assignment. After a motivation of the tracking of multiple spectral values for analysis/control perspectives, some existing links between Birkhoff’s interpolation problem and a result due to Pólya and Szegö on the number of quasipolynomial's roots in a horizontal strip shall be revisited. Later, hints of an analytic proof of the dominancy of the quasipolynomial's root will be presented, setting up a reduced-complexity delayed stabilizing design. Sensitivity of the control design with respect to the parameters' variation will be discussed. To overcome the sensitivity of multiple roots, an extension of the approach to real distinct pole assignment shall be presented. Finally, various reduced order examples will illustrate the applicative perspectives of the proposed control approach.

Biography: Islam Boussaada received his Master in Mathematics from University Tunis II, and an M.Sc. degree in Pure Mathematics from University Paris 7 in 2004. In December 2008, he defended his Ph.D. degree in Mathematics from University of Rouen Normandy. In June 2016, he received his HDR degree (French Habilitation) in Physics from University Paris Saclay-University Paris Sud. In 2010, IB was appointed for two years as a post-doctoral fellow in the control of time-delay systems at L2S, Supelec-CNRS-University Paris Sud. Since 2012, he has been an associate professor at IPSA and an associate researcher at MODESTY Team of L2S. Since September 2017, IB is appointed permanent researcher at DISCO Team and full professor at IPSA where he headed the Aeronautical and Aerospace Systems department from September 2017 till May 2019.
Since September 2018 untill August 2020, IB is a researcher in temporary secondment at Inria Saclay-DISCO Team. His research interests belong to the qualitative theory of dynamical systems and its application in control problems. It includes stability analysis and stabilization of linear/nonlinear dynamical systems, analysis of parametric systems, analysis of delay induced dynamics, nonhyperbolic dynamics, analysis of algebraic dierential systems, control of active vibrations, dynamics of biochemical networks. IB is co-author of a monograph and co-editor of a contributed book, both published in Springer series, as well as co-author of more than 60 peer-reviewed publications. He co-organized the 4th GDRI DelSys's Workshop on Observing and Controlling Complex Dynamical Systems (November 2015), as well as the 1st GDRI Spa-Disco's workshop on Delays and Constraints in Distributed Parameters Systems (November 2017), both funded by CNRS and held at CentraleSupelec (Gif sur Yvette). At the occasion of the 20th World Congress of the International Federation of Automatic Control (IFAC) (Toulouse, July 2017), IB co-organized an invited session "Frequency domain Techniques for Time-delay Systems". At the occasion of the 13th-15th IFAC Workshop on Time-delay Systems (Istanbul 2016, Budapest 2018, Sinaia 2019), IB co-organized thematic sessions on Spectral Methods for Rightmost Roots Characterization in LTI Time-delay Systems. Since September 2018, IB is co-leading the national research group GT OSYDI of the CNRS/GDR MACS and is a deputy director of the IRS iCODE Institute of the University Paris Saclay.

11:00-12:00 Ludovic Sacchelli (Lehigh University, Pennsylvania, USA)

Title: Stabilization of non-uniformly observable system

Abstract: A common strategy in dynamic output feedback stabilization is to apply a state feedback to an observer in order to stabilize the coupled state-observer system. It is well known that global stabilizability, paired with uniform observability, implies semi-global stabilisability by dynamic output feedback. However in many generic cases, the system is not uniformly observable, and usual strategies for semi-global stabilization break down. New approaches need to be explored to resolve this issue. We will present case studies to give an outlook for the challenges raised by this problem and highlight a promising answer based on the idea of unitary embeddings of control systems.

Biography: Ludovic Sacchelli is a visiting assistant professor in the Mathematics Department of Lehigh University, in Bethlehem, Pennsylvania. He graduated from Ecole Normale Supérieure de Cachan and received his master's degree in analysis of PDEs from Paris-Sud University in 2015. He obtained a Ph.D. in applied mathematics from Ecole Polytechnique in 2018 on the topic of sub-Riemannian geometry. Ludovic spent the following year as a postdoc in the Electrical Engineering Department of University of Toulon (LIS Lab) before departing for his current position. His research interests lie in sub-Riemannian geometry, control theory and observability.

Techniques champ proche: Du système antennaire à l'application sur le terrain

Mohammed SERHIR
Habilitation à Diriger des Recherches (HDR) le 10 Octobre 2019, 14h00 à

Cette soutenance aura lieu à CentraleSupélec – Campus de Paris-Saclay

Lieu: Amphi IV  dans le Bât. Eiffel

Composition du jury:

M. Jean-Yves DAUVIGNAC Professeur à l’Université de Nice-Sophia Antipolis, LEAT Rapporteur
M. Raphael GILLARD Professeur à l’INSA de Rennes, IETR Rpporteur
M. Sébastien LAMBOT Professeur à l’Université Catholique de Louvain, Louvain Georadar Research Centre Rpporteur
M. Dominique LESSELIER Directeur de Recherche CNRS, L2S Examinateur
M. Lionel PICHON Directeur de Recherche CNRS, GeePs Examinateur
M. Jean-Michel GEFFRIN Ingénieur de Recherche CNRS, Institut Fresnel Examinateur
M. Régis GUINVARC'H Professeur à CentraleSupélec, SONDRA Invité


Dans ce travail de synthèse, je donne un aperçu de mes activités de recherche en électromagnétisme appliqué. Axées sur la modélisation comportementale, mes premières contributions visaient à proposer une passerelle entre la simulation numérique et la caractérisation expérimentale des antennes. Dans un deuxième temps, j’évoque mes apports dans le thème de la caractérisation d’antennes en champ proche à travers la méthode matricielle pour le calcul du champ lointain. Cette activité expérimentale est à l’origine de plusieurs collaborations nationales et internationales. Enfin, je développe mes travaux sur l’imagerie micro-onde appliquée au radar de sol. J’y présente les conclusions de la modélisation du problème direct par la méthode DGTD et la résolution du problème inverse par Linear Sampling Method. Les applications étudiées sont la détection des systèmes racinaires des arbres et la localisation de câbles souterrains en situation réelle. Les travaux de recherche sur l’imagerie du proche sous-sol sont pluridisciplinaires et constituent le point de convergence de mes activités précédentes y compris les développements antennaires dédiés au radar de sol.


Ps:Vous êtes cordialement invités au pot qui suivra dans la salle du conseil dans l'aile B4 du Bât. Breguet

Synthèse compositionnelle et efficace de contrôleurs pour les systèmes cyber-physiques

Adnane SAOUD
Soutenance de thèse de doctorat le 7 Octobre 2019, 15h00 à CentraleSupelec (Gif-sur-Yvette)

Lieu :  Bâtiment Eiffel - Amphi V

3, rue Joliot Curie - 91190 GIF-SUR-YVETTE


Composition du jury proposé : 

M. Antoine GIRARD CNRS Directeur de thèse
M. Laurent FRIBOURG ENS Paris-Saclay Co-directeur de thèse
M. Nacim RAMDANI Université d'Orléans Rapporteur
M. Murat ARCAK University of California, Berkeley Rapporteur
Mme Sophie TARBOURIECH CNRS - LAAS Examinateur
M. Sorin OLARU CentraleSupélec Examinateur
Mme Necmiye OZAY University of Michigan Examinateur
Mme Jana TUMOVA KTH Royal Institute of Technology Examinateur


Résumé : 

              Cette thèse porte sur le développement d'approches compositionnelles et efficaces de synthèse de contrôleurs pour les systèmes cyber-physiques (CPS). En effet, alors que les techniques de conception des CPS basées sur des modèles ont fait l'objet de nombreuses études au cours de la dernière décennie, leur scalabilité reste problématique. Dans cette thèse, nous contribuons à rendre de telles approches plus évolutives. La première partie est axée sur les approches compositionnelles. Un cadre général  pour le raisonnement compositionnel  en  utilisant  des  contrats  d’hypothèse-garantie est proposé. Ce cadre est ensuite combiné avec des techniques de contrôle symbolique et appliqué à un problème de synthèse de contrôleur pour des systèmes échantillonnés, distribués et multipériodiques, où l'approche symbolique est utilisé pour synthétiser un contrôleur imposant un contrat donné. Ensuite, une nouvelle approche de calcul compositionnel des abstractions symboliques est proposée, basée sur la notion de composition approchée et permettant de traiter des abstractions hétérogènes. La deuxième partie de la thèse porte sur des techniques efficaces d'abstraction et de synthèse de contrôleurs. Deux nouvelles techniques de calcul d’abstractions sont proposées pour les systèmes à commutation incrémentalement stables. La première approche est basée sur l'échantillonnage multi- niveaux où nous avons établi l'existence d'un paramètre optimal d'échantillonnage qui aboutit à un modèle  symbolique avec un  nombre minimal de transitions. La deuxième approche  est basée sur  un échantillonnage événementiel, où la durée  des transitions dans le modèle symbolique est  déterminée par  un  mécanisme  déclencheur, ce  qui   permet  de  réduire le conservatisme  par  rapport   au  cas périodique. La combinaison avec des techniques de  synthèse  de contrôleurs paresseux  est  proposée permettant  la  synthèse   à  un  coût  de  calcul   réduit.

              Enfin,   une   nouvelle   approche de synthèse paresseuse  a  été  développée   pour  les  systèmes  de transition monotones et  les
spécifications   de sécurité  dirigées.  Plusieurs études  de cas sont considérées  dans cette  thèse, telles que la régulation de la température  dans  les bâtiments, le  contrôle   des  convertisseurs  de  puissance,   le  pilotage   des véhicules et le contrôle  de la tension dans les micro-réseaux DC.

Mots-clés : méthodes compositionnelles, commande basée sur l'abstraction, contrats d'hypothèse garantie.


Control of automated vehicles and their influence on traffic

Séminaire le 3 Octobre 2019, 14h00 à CentraleSupelec (Gif-sur-Yvette) Salle des séminaires du L2S
Karl H. Johansson

Abstract: Automated and connected road vehicles enable large-scale control and optimisation of the transport system with the potential to radically improve fuel efficiency, decrease the environmental footprint, and enhance safety. In this talk we will focus on automated heavy-duty vehicle platooning, which is currently being implemented and evaluated by several truck manufacturers world-wide. We will discuss how to deploy feedback control of individual platoons utilising the cellular communication infrastructure and how such controlled platoons can be used improve overall traffic conditions. It will be argued that the average total variation of traffic density can be reduced and thereby creating incentives for platooning beyond fuel savings and driver support. Extensive experiments done on European highways will illustrate system performance and safety requirements. The presentation will be based on joint work with collaborators at KTH and at the truck manufacturers Scania and Volvo.

Biography: Karl H. Johansson is Professor at the School of Electrical Engineering and Computer Science, KTH Royal Institute of Technology. He received MSc and PhD degrees from Lund University. He has held visiting positions at UC Berkeley, Caltech, NTU, HKUST Institute of Advanced Studies, and NTNU. His research interests are in networked control systems, cyber-physical systems, and applications in transportation, energy, and automation networks. He has received several best paper awards and other distinctions from IEEE, IFAC and ACM. He has been awarded Distinguished Professor with the Swedish Research Council and Wallenberg Scholar with the Knut and Alice Wallenberg Foundation. He has received the Future Research Leader Award from the Swedish Foundation for Strategic Research and the triennial Young Author Prize from IFAC. He is Fellow of the IEEE and the Royal Swedish Academy of Engineering Sciences, and he is IEEE Distinguished Lecturer.

Control of automated vehicles and their influence on traffic

Séminaire le 3 Octobre 2019, 14h00 à CentraleSupelec (Gif-sur-Yvette) Salle des séminaires du L2S
Karl H. Johansson

Abstract: Automated and connected road vehicles enable large-scale control and optimisation of the transport system with the potential to radically improve fuel efficiency, decrease the environmental footprint, and enhance safety. In this talk we will focus on automated heavy-duty vehicle platooning, which is currently being implemented and evaluated by several truck manufacturers world-wide. We will discuss how to deploy feedback control of individual platoons utilising the cellular communication infrastructure and how such controlled platoons can be used improve overall traffic conditions. It will be argued that the average total variation of traffic density can be reduced and thereby creating incentives for platooning beyond fuel savings and driver support. Extensive experiments done on European highways will illustrate system performance and safety requirements. The presentation will be based on joint work with collaborators at KTH and at the truck manufacturers Scania and Volvo.

Biography: Karl H. Johansson is Professor at the School of Electrical Engineering and Computer Science, KTH Royal Institute of Technology. He received MSc and PhD degrees from Lund University. He has held visiting positions at UC Berkeley, Caltech, NTU, HKUST Institute of Advanced Studies, and NTNU. His research interests are in networked control systems, cyber-physical systems, and applications in transportation, energy, and automation networks. He has received several best paper awards and other distinctions from IEEE, IFAC and ACM. He has been awarded Distinguished Professor with the Swedish Research Council and Wallenberg Scholar with the Knut and Alice Wallenberg Foundation. He has received the Future Research Leader Award from the Swedish Foundation for Strategic Research and the triennial Young Author Prize from IFAC. He is Fellow of the IEEE and the Royal Swedish Academy of Engineering Sciences, and he is IEEE Distinguished Lecturer.

Statistique des estimateurs robustes pour le traitement du signal et des images

Madame Gordana DRASKOVIC
Soutenance de thèse de doctorat le 27 Septembre 2019, 10h00 à CentraleSupelec (Gif-sur-Yvette)

Lieu :

CentraleSupelec-Bâtiment Bouygues-3 rue Joliot Curie-91190 Gif-sur-Yvette-Salle : E.070 (Théâtre)


Composition du jury proposé :

M. Frédéric PASCAL CentraleSupélec Directeur de thèse
Mme Florence TUPIN Télécom Paris Co-directeur de thèse
M. Cédric RICHARD Université de Nice Sophia-Antipolis Rapporteur
M. Olivier MICHEL Grenoble INP Rapporteur
M. Patrick FLANDRIN CNRS-Ecole Normale Supérieure de Lyon Examinateur
Mme Michele SEBAG CNRS - Université Paris Sud Examinateur
M. Matthieu JONCKHEERE Universidad de Buenos Aires Invité

Résumé :
Un des défis majeurs en traitement radar consiste à identifier une cible cachée dans un environnement bruité. Pour ce faire, il est nécessaire de caractériser finement les propriétés statistiques du bruit, en particulier sa matrice de covariance. Sous l'hypothèse gaussienne, cette dernière est estimée par la matrice de covariance empirique (SCM) dont le comportement est parfaitement connu. Cependant, dans de nombreuses applications actuelles, tels les systèmes radar modernes à haute résolution par exemple, les données collectées sont de nature hétérogène, et ne peuvent être proprement décrites par un processus gaussien. Pour pallier ce problème, les distributions symétriques elliptiques complexes, caractérisant mieux ces phénomènes physiques complexes, ont été proposées. Dans ce cas, les performances de la SCM sont très médiocres et les M-estimateurs apparaissent comme une bonne alternative, principalement en raison de leur flexibilité par rapport au modèle statistique et de leur robustesse aux données aberrantes et/ou aux données manquantes. Cependant, le comportement de tels estimateurs reste encore mal compris. Dans ce contexte, les contributions de cette thèse sont multiples.
D'abord, une approche originale pour analyser les propriétés statistiques des M-estimateurs est proposée, révélant que les propriétés statistiques des M-estimateurs peuvent être bien approximées par une distribution de Wishart. Grâce à ces résultats, nous analysons la décomposition de la matrice de covariance en éléments propres. Selon l'application, la matrice de covariance peut posséder une structure particulière impliquant valeurs propres multiples contenant les informations d'intérêt. Nous abordons ainsi divers scénarii rencontrés dans la pratique et proposons des procédures robustes basées sur des Mestimateurs.
De plus, nous étudions le problème de la détection robuste du signal. Les propriétés statistiques de diverses statistiques de détection adaptative construites avec des M-estimateurs sont analysées. Enfin, la dernière partie de ces travaux est consacrée au traitement des images radar à synthèse d'ouverture polarimétriques (PolSAR). En imagerie PolSAR, un effet particulier appelé speckle dégrade considérablement la qualité de l'image. Dans cette thèse, nous montrons comment les nouvelles propriétés statistiques des M-estimateurs peuvent être exploitées afin de construire de nouvelles techniques pour la réduction du speckle.


Mots clés :
Estimation robuste, distributions CES, distribution de Wishart, détection du signal, images PolSAR, décomposition en éléments propres.

Cooperative Wireless Communications in the Presence of Limited Feedback

Soutenance de thèse de doctorat le 25 Septembre 2019, 10h00 à CentraleSupelec (Gif-sur-Yvette)

Cette soutenance aura lieu à CENTRALESUPELEC, Gif-sur-Yvette, Bâtiment Bouygues -Amphi sc.071 

Composition du jury:

Antoine BERTHET          CentraleSupélec                           Directeur de thèse

Raphaël VISOZ               Orange Labs                                 Encadrant de thèse

Karine AMIS                    IMT Atlantique Bretagne               Rapporteur

Didier LE RUYET            CEDRIC/LAETITIA CNAM            Rapporteur

Raymond KNOPP           EURECOM                                   Examinateur

Samson LASAULCE       CNRS                                           Examinateur



Abstract : 

A constant need for improved quality of wireless services has pushed the wireless technology and development of wireless networks to the point where they have became an integral part of our modern society. Exploiting an innovative concept such as cooperative communications is one possible avenue for answering the increasingly challenging demands from users, which is the main subject of this thesis. Its principle idea is to allow devices to share their available resources in power and/or bandwidth in order to mutually improve their transmission and reception.

Cooperation techniques have been studied for Multiple Access Multiple Relay Channel (MAMRC), consisted of at least two sources which communicate with a single destination with the help of at least two nodes which perform relaying functions (relaying nodes). A relaying node can be either a dedicated relay, which does not have its own message to transmit, or a source itself, which does have its own message and that can relay the messages of the other sources in some cases. All relaying nodes are assumed to operate in half-duplex mode, while all the channels experience slow (quasi-static) fading. Time Division Multiplexing (TDM) is assumed. First, the link adaptation algorithm is performed at the scheduler which is located at the destination. Sources transmit in turns in consecutive time slots during the first transmission phase. The second phase consists of a limited number of time slots for retransmissions. In each time slot, the destination schedules a node (being a source or a relay) to transmit redundancies, implementing a cooperative Hybrid Automatic Repeat reQuest (HARQ) protocol. Bidirectional limited control channels are available from sources and relays towards the destination to implement the necessary control signaling of HARQ protocols.

In the first part of the thesis, the focus is on design of centralized scheduling (node selection) strategies for the second phase. The scheduling decisions are made based on the knowledge of the correctly decoded source sets of each node, with the goal to maximize the average spectral efficiency under the given constraint of fairness. A scheduled node uses Joint Network and Channel Coding (JNCC) on its decoded source set. An information outage analysis is conducted and Monte-Carlo (MC) simulations are performed, which show that these strategies outperform the state of the art one based on the minimization of the probability of the common outage event after each time-slot.

In the second part of the thesis, a slow-link adaptation algorithm is proposed which aims at maximizing the average spectral efficiency under individual QoS targets for a given modulation and coding scheme (MCS) family. The defined utility metric is conditional on the node selection strategy that is used in the second phase. Channel Distribution Information (CDI) is reported to the destination in order to derive the source rates on a long-term basis, which is adapted to the scenario of fast changing radio conditions. Two variants of the algorithm are proposed, one where CDI, and the other where Channel State Information (CSI) of each link is reported to the destination in order to derive the source rates. They are adapted to scenarios with fast and slow changing radio conditions, respectively.

Discrete source rates are first determined using the ``Genie-Aided'' assumption, which is followed by an iterative rate correction algorithm. The resulting scheduling and link adaptation algorithm yields performance close to the exhaustive search approach as demonstrated by MC simulations. In addition, a fast-link adaptation algorithm is proposed, adapted to the scenario where the CSI of all links is reported to the destination.

In the third part of the thesis, performances of three different cooperative HARQ protocols are compared, with the goal to identify the one which offers the best trade-off between performance and complexity. Incremental Redundancy (IR) HARQ with single-user and multiuser encoding are considered, as well as the Chase Combining HARQ with single-user encoding. MC simulations demonstrate that IR-HARQ with single-user encoding offers the best trade-off between performance and complexity for a small number of sources in our setting. Additionally, a practical encoding and decoding scheme is proposed for a scenario where relaying nodes implement single-user encoding, and its performance has been evaluated using MC simulations. The encoding/decoding scheme is based on a turbo code in conjunction with the proposed link adaptation algorithm. The algorithm operates with a family of practical MCSs, where circular buffer is implemented to form transmission messages with desired coding rate.

Keywords: Relay-assisted cooperative communications, multi-source multi-relay wireless networks, centralized scheduling, node selection, slow-link adaptation, iterative rate correction, spectral efficiency, chase combining, incremental redundancy, HARQ, turbo codes.