All Years Seminars
[INMA] 2006-03-21 (14.00 pm) : "Ellipsoidal and Interval Techniques for State Estimation in Linear Dynamical Systems under Model Uncertainty"
At Euler building
Speaker :
Sergey Nazin (CESAME, previously Institute of Control Science, Moscow)
Abstract :
The unknown-but-bounded description of system uncertainty is a main
counterpart to its probabilistic characterization. This description forms
the set-membership approach to the different kinds of problems in control and
identification. My talk is devoted to the state estimation problem for
linear discrete-time dynamical systems under unknown-but-bounded
uncertainties. This problem is to characterize the set of all feasible
system state vectors that are compatible with the model structure,
measurement data and hypotheses on the perturbations. All points of this set
are the candidate solutions of the estimation problem. Since the set
obtained may become extremely complicated, its outer approximations by a
simpler sets like ellipsoids or interval vectors (boxes) are then customary
to use. Ellipsoidal and interval methods will be presented for state
estimation in the case of model uncertainty, which is a natural extension of
classical methods for deterministic models with unknown-but-bounded state
perturbations and measurement noise.
[INMA] 2006-03-16 (17.00 pm) : Colloquium CESAME/MAPA "Applications de la théorie des graphes pour l'analyse des réseaux métaboliques "
At Auditoire Ch.-J. de La Vallée Poussin (cycl 01)
Speaker :
Jacques Van Helden (ULB)
Abstract :
Les processus biologiques sont assurés par des interactions entre
différents types de molécule : métabolites (petites molécules),
protéines, acides nucléiques,
Les réactions métaboliques, qui
permettent de convertir des groupes de molécules en autres molécules,
ont été caractérisées depuis plus dun siècle par les biochimistes.
Plus récemment, les méthodes « à haut débit », ont permis la détection
systématique des interactions protéines-protéines ou protéines-ADN, à
léchelle dun génome. Les données accumulées peuvent être représentées
sous la forme de graphes dinteractions, regroupant plusieurs milliers
de nuds et darcs. Nous présenterons différentes méthodes qui sont mises
à contribution pour analyser les propriétés de ces graphes, afin dinférer
les propriétés biologiques des processus quils représentent. Nous
traiterons notamment de lanalyse topologique, de la détection de motifs,
et de linférence de voies métaboliques par recherche de chemins dans les
graphes de réactions.
[INMA] 2006-03-07 (14.00 pm) : "Smoothing techniques on Jordan algebras"
At Euler building
Speaker :
Michel Baes (CORE)
Abstract :
A spectral function on a formally real Jordan algebra is a
real-valued function that depends only on the eigenvalues of its
argument. One convenient way to create them is to start from a
function $f$ from $\mathbb{R}^r$ to $\mathbb{R}$ that is symmetric in the components
of its argument, and to define the function $F(u):=f(\lambda(u))$ where $\lambda(u)$ is
the vector of eigenvalues of $u$. A particular example of this construction is
given by functions of symmetric matrices that only depend on the
eigenvalues of its argument. We positively answer an open question proposed in the PhD thesis
of H. Sendov : "is it possible to compute the hessian of spectral functions on Jordan algebras?"
We then exploit this result to investigate how the power smoothing
techniques of Yu. Nesterov can in some instances be extended to
Jordan algebras. In particular, we propose a new algorithm to
minimize a sum of Euclidean norms and we perform its complexity
analysis.
[INMA] 2006-02-28 (14.00 pm) : "Non linear Finite Time Observer"
At Euler building
Speaker :
Frederic Sauvage (IMAP)
Abstract :
We propose a finite time observer for nonlinear systems that converges in finite time.
The key idea is to use the present and delayed estimates provided by two independent
classical observers taking advantage that the dynamics linearity allows to express the present
reconstruction error as a function of the delayed one.
[INMA] 2006-02-21 (14.00 pm) : "Estimation and enlargement of domains of attraction"
At Euler building
Speaker :
Bazanella, Alexandre
Abstract :
Establishing that an asymptotically stable equilibrium has a sufficiently large domain of attraction (DOA)
is crucial for its stability to have practical meaning. Hence, providing such sufficiently large DOA's is also
a major control objective to be pursued. In nonlinear systems theory, estimation of DOA's and control
design are most usually tackled by means of Lyapunov's direct method. The estimates of DOA's obtained
by means of Lyapunov analysis depend strongly on the particular Lyapunov function used and can be very
poor, which also diminishes its value as a control design tool in this context. In this seminar I will present
a numerical method, based on LMI's, to determine Lyapunov functions for rational nonlinear systems.
On the other hand, most Lyapunov based control design theory has been concerned with the achievement
of global asymptotic stability, which is sometimes impossible and most often unnecessary. I'll present some
results on LgV control and the more general interconnection and damping assignment (IDA) control design
method, concerning the enlargment of DOA's of open-loop stable equilibria. I will also present a dynamic
feedback scheme which inherits these properties and usually results in better performance than LgV and IDA
. Finally, applications to the real-time assessment and the enhancement of electric power systems security
will be presented.
Seminars
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