Michel Fliess

LIX – Palaiseau

7 décembre 2023, 14.30
Salle X133
Campus Toulon

Atténuer les congestions internet grâce aux outils de l’automatique

Active Queue Management (AQM) for mitigating Internet congestion has been addressed via various feedback control syntheses, especially P, PI, and PID regulators, by using a linear approximation where the round trip time, i.e., the delay, is assumed to be constant. This constraint is lifted here by using a nonlinear modeling with a variable delay, introduced more than 20 years ago. This delay, intimately linked to the congestion phenomenon, may be viewed as a flat output. All other system variables, especially the control variable, i.e., the packet loss ratio, are expressed as a function of the delay and its derivatives: they are frozen if the delay is kept constant. This flatness-like property, which demonstrates the mathematical discrepancy of the linear approximation adopted until today, yields also our control strategy in two steps: Firstly, designing an open-loop control, thanks to straightforward Flatness-Based Control (FBC) techniques, and secondly, closing the loop via Model-Free Control (MFC) in order to take into account severe model mismatches, like, here, the number of TCP sessions. Several convincing computer simulations, which are easily implementable, are presented and discussed.

Alessandro Scagliotti

TUM Munich

30 novembre 2023, 14.00
Salle X133
Campus Toulon

Ensemble optimal control: ResNets, diffeomorphisms approximation and
Normalizing Flows

In the last years it was observed that Residual Neural
Networks (ResNets) can be interpreted as discretizations of control
systems, bridging ResNets (and, more generally, Deep Learning) with
Control Theory. In the first part of this seminar we formulate the task
of a data-driven reconstruction of a diffeomorphism as an ensemble
optimal control problem. In the second part we adapt this machinery to
address the problem of Normalizing Flows: after observing some samplings
of an unknown probability measure, we want to (approximately) construct
a transport map that brings a “simple” distribution (e.g., a Gaussian)
onto the unknown target distribution. In both the problems we use tools
from $\Gamma$-convergence to study the limiting case when the size of
the data-set tends to infinity.

This talk is based on the papers

Deep Learning approximation of diffeomorphisms via linear-control systems.

Normalizing flows as approximations of optimal transport maps via
linear-control neural ODEs

Hassan Haghighi


12 octobre 2023, 14.00
Salle des commissions
Campus St. Jérôme

Path Planning According to the Fault Tolerance and Modeling. Application in: Autonomous Emergency Landing for Aircraft

 In the field of controlling complex systems, a key focus is on developing strategies to handle technical, dynamic, structural defects, and faults. This study analyzes equation stability and state-space structure changes to identify stable system poles despite the presence of defects. Additionally, it employs Dubin’s equations to swiftly devise emergency landing routes. To implement in a case study project, we construct sample sets of stable poles for the system according to the defects and calculate corresponding path as admissible set. From these samples, we design a path planning system to select specific points. Our concept integrates Dubin’s path for emergency landings, enabling an optimization system to choose from admissible stable routes.

Swann Marx

L2SN (UMR CNRS 6004) Nantes

27 avril 2023, 14.00
Salle des commissions
Campus St. Jérôme

Singular perturbation analysis for a coupled KdV-ODE system

This talk will be about the singular perturbation analysis of
a Korteweg-de Vries equation, which is a nonlinear PDE modeling waves on
shallow water surfaces, coupled with an ODE. The coupled system may
admit different time-scales, and this particular feature will be taken
into account when analysing the asymptotic stability of the coupled
system. To introduce our methodology, we will first explain how it can
be applied on scalar ODEs. We will then give some insights on the
difficulties when applying it on already known coupled PDE-ODE systems.
Finally, we will show how one can apply this methodology for the KdV-ODE
system under consideration. This talk is based on a joint work with
Eduardo Cerpa, professor at the Universidad Catolica de Chile.

Térence Bayen

LMA (Avignon)

19 janvier 2023, 11.00
Salle X 133
Campus Toulon

A hybrid maximum principle including regional switching parameters.

 In this presentation, we consider a Mayer optimal control problem where the controlled system is defined over a partition of the euclidean space, and we assume that the dynamics depends on some additional regionally switching parameter. This means that the parameter should remain constant as long as the trajectory belongs to a given stratum, but, in contrast with optimal control problems including (constant) parameters, it is now authorized to change its value each time the system enters into a new stratum. This framework is motivated by several applications arising in the context of aerospace engineering or in epidemiology (typically when a loss of control occurs). In this presentation, we give the necessary optimality conditions in this framework in the spirit of a hybrid maximum principle. The necessary optimality conditions involve a jump of the covector at the interface between two strata and also an averaged gradient condition related to the regionally switching parameter. We shall also give some insights how to obtain such a result using needle’s type variations. 

Eugenio Pozzoli

Eugenio Pozzoli

20 octobre 2022, 14.30
Salle X 133
Campus Toulon

Contrôlabilité des systèmes quantiques en dimension infinie

L’étude des propriétés de contrôlabilité d’un système quantique joue un rôle important dans les applications en physique et en chimie, comme par example la spectroscopie et l’information quantique. Les questions que j’aborderai dans cet exposé sont principalement deux : (i) le système (fermé) peut-il être contrôlé parmi tous ses états ? (ii) quels états peuvent être atteints en temps petit ? La question (i) est un problème de contrôlabilité bilinéaire (globale). La question (ii) est un problème d’accessibilité bilinéaire en petit temps, lié au problème du temps minimal. Dans le cadre où l’état évolue dans un espace infini-dimensionnel, je présenterai quelques réponses aux questions (i) en utilisant des approximations fini-dimensionnelles avec des contrôles périodiques et (ii) en utilisant une technique de saturation issue du contrôle géométrique avec des contrôles pas bornés. Je montrerai aussi des applications de ces résultats au contrôle de la dynamique rotationelle des molécules, vues comme des corps rigides quantiques.

Patrick Siarry

Patrick Siarry

02 Juin 2022, 14.00
salle des commissions
Campus St. Jérôme

Quelques travaux sur les métaheuristiques en optimisation continue

Dans cet exposé, nous présentons tout d’abord le cadre général de l’optimisation continue « difficile »: après une brève description de quelques applications typiques, nous soulignons les difficultés propres aux problèmes continus.
Nous décrivons ensuite quelques pièges de l’adaptation des métaheuristiques à des problèmes à variables continues.
Puis nous présentons, à titre d’illustration, les méthodes que nous avons proposées pour adapter deux métaheuristiques : le recuit simulé et les algorithmes de colonie de fourmis.
Nous décrivons ensuite quelques travaux récents en optimisation dynamique.
Enfin, nous présentons notre contribution relative à l’optimisation par essaim de particules.

Mohamed Bouri

Mohamed Bouri
Rehabilitation and Assistive Robotics (REHAssist) Research Group.
Ecole Polytechnique Fédérale de Lausanne (EPFL)

09 Septembre 2021, 10.00
salle des commissions
Campus Saint-Jérôme, Marseille

Exosquelettes des membres inférieurs: une solution pour la promotion et la rééducation de la marche.

Dr Mohamed Bouri is a roboticist, specialized in the development and 
control of complex robotics structures. He leads the research group 
« Rehabilitation and Assistive Robotics (REHAssist) » at Ecole 
Polytechnique Fédérale de Lausanne (EPFL). His research focuses on 
« Medical robotics » for rehabilitation, lower limb exoskeletons and 
surgical applications.

Yacine Chitour

Yacine Chitour


21 Novembre 2019, 14.00
salle des commissions
Campus St. Jérôme

Finite time stabilization for chains of integrators

In this talk, I will present various techniques of stabilization in finite time for perturbed and unperturbed chains of integrators. These issues arise in sliding mode control.
Joint work with M Harmouche and S Laghrouche.

Gabriel Wainer

Gabriel Wainer
Carleton University


21 Octobre 2019, 14.00
salle des commissions
Campus St. Jérôme

Discrete-Event Modeling and Simulation Methodologies: Past, Present and Future

Modeling and Simulation methods have been used to better analyze the behavior of complex physical systems and it is now common to use simulation as a part of the scientific and technological discovery process. M&S advanced thanks to the improvements in computer technology, which, in many cases, resulted in the development of simulation software using ad-hoc techniques.

Formal M&S appeared in order to try to improve the development task of very complex simulation systems. Some of these techniques proved to be successful in providing a sound base for the development of discrete-event simulation models, improving the ease of model definition and enhancing the application development tasks; reducing costs and favoring reuse.

The DEVS formalism is one of these techniques, which proved to be successful in providing means for modeling while reducing development complexity and costs. DEVS model development is based on a sound theoretical framework. The independence of M&S tasks made possible to run DEVS models on different environments (personal computers, parallel computers, real-time equipment, and distributed simulators) and middleware.

We will present a historical perspective of discrete-event M&S methodologies, showing different modeling techniques. We will introduce DEVS origins and general ideas, and compare it with some of these techniques. We will then show the current status of DEVS M&S, and we will discuss a technological perspective to solve current M&S problems (including real-time simulation, interoperability and model-centered development techniques). We will show some examples of the current use of DEVS, including applications in different fields.

We will finally show current open topics in the area, which include advanced methods for centralized, parallel or distributed simulation, the need of real-time modeling techniques, and our view in these fields.