All Years Seminars
[INMA] 2009-10-13 (14.00) : Robust Optimal Control of Finite-time Distributed Parameter Systems
At Euler building
Speaker :
Richard
BRAATZ (University of Illinois at Urbana-Champaign)
Abstract :
Most products of high value such as in the pharmaceuticals, microelectronic, and nanotechnology industries are manufactured in a series of processing steps that operate over finite time.
These processes are usually distributed parameter systems in which tight control is required. Computationally efficient methods are proposed for the robust optimal control of finite-time distributed
parameter systems (DPS), in which robustness is ensured for either deterministic or stochastic parametric uncertainties. In the deterministic case, the effects of uncertainties on the states and product
quality are quantified by power series expansions combined with linear matrix inequality or structured singular value analysis. In the stochastic case, the effects of uncertainties are quantified by power
series or polynomial chaos expansions followed by Monte Carlo simulation. The robust performance analysis have been incorporated into fixed or model predictive control algorithms. The approaches
are illustrated for several applications problems.
[INMA] 2009-10-08 (16.30) : Colloquium CESAME-MAPA - Espaces de surfaces et catégories de surfaces (conjecture de Mumford)
At Auditoire Ch.-J. de La Vallée Poussin (cycl 01)
Speaker :
Michel
WEISS (Aberdeen)
Abstract :
Soit M l'espace des surfaces connexes, orientées, de genre g, plongées dans l'espace euclidien de dimension n.
On suppose que g et n sont très grands. L'espace M est très loin d'être simplement connexe.
Toutefois la conjecture de Mumford, dans une formulation contemporaine, est une description de
la meilleure approximation de M par un espace simplement connexe. Selon la conjecture celle-ci s'obtient
à partir de M par un procédé de "scanning". L'étude de certaines catégories de surfaces a beaucoup contribué à la preuve
de la conjecture.
[INMA] 2009-10-06 (14.00) : Fast computation on SO(3) of optimal oriented bounding box
At Euler building
Speaker :
CHANG Chia-Tche
GORISSEN Bastien (CESAME)
Abstract :
Photorealistic realtime rendering and physically correct simulations of
3D scenes are at the bleeding edge of what can be done with today's
computers. Such applications involve collision detection and visibility
tests using methods based on oriented bounding boxes (OBB) enclosing 3D
objects. Joseph O'Rourke published in 1985 an algorithm that computes the
exact solution in cubic time, but is extremely hard to implement. In
practice, faster PCA-based and brute force heuristics are used. The
computation of the minimal-volume OBB is formulated as an unconstrained
optimization problem on the rotation group SO(3). It is solved using a
hybrid method combining the genetic and Nelder-Mead algorithms. This
method is analyzed then compared to the current state-of-the-art, and it
turns out to be either faster or more accurate.
[INMA] 2009-09-29 (14.00) : New model of gaze tracking in 2D: Novel architecture with independent gaze and head controllers
At Euler building
Speaker :
Daye, Pierre
Abstract :
Reorienting our gaze recruits both eye and head movements to achieve a
common goal. During a gaze movement, the head may also be voluntarily
moved for some other purpose, e.g., to align the mouth with food.
Currently, two mechanisms are proposed to explain the coordination of
eye and head movements. In the first, a central gaze controller
pre-computes a desired eye and head displacement to execute a gaze
movement. This model can generate independent movements for the head and
gaze but, because of its structure, it can not compensate for
perturbations of the head during the gaze change. In the second, a gaze
controller sends the same command to the eye and the head, and a gaze
feedback loop compensates for any errors or perturbations during the
gaze change. However, this model can not generate independent movements
of the head. We propose a novel approach for coordinated eye and head
control in which there are separate controllers, for gaze and head,
rather than for gaze alone or for eye and head. In this model, the gaze
controller drives both the eye and the head. Gaze feedback through the
cerebellum compensates for perturbations by acting only on the eye.
Thus, in this model the eye only serves gaze, and can not be directed to
an arbitrary goal.
[INMA] 2009-09-22 (14.00) : Stiefel Manifolds and their Applications
At Euler building
Speaker :
Absil, Pierre-Antoine
Abstract :
Stiefel manifolds, or sets of orthonormal p-frames in R^n, are named after Eduard Stiefel (1909-1978),
who analyzed their topology in the 1930s. This presentation will be a reiteration of a talk that was part of the celebration
of Stiefel's 100th birthday at ETH Zurich. We will count dimensions, describe tangent spaces, visualize embedded and
quotient geodesics, and touch upon applications such as principal component analysis, Lyapunov exponent computation,
and blind source separation.
Seminars
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