All Years Seminars
[INMA] 2006-02-14 (14.00 pm) : "Robust and Feed-forward Controller Optimization by Iterative Feedback Tuning"
At Euler building
Speaker :
Hynek Prochazka (CESAME )
Abstract :
Iterative Feedback Tuning (IFT) is an iterative procedure for controller optimization. It is useful mainly for tuning of badly adjusted low-order controllers to upgrade its performance. Desired controller performance is expressed in terms of a criterion. The criterion is typically constructed with two terms: one reflecting a desired tracking property, the second one restricting control action energy. The IFT procedure does not require a plant model; only closed-loop system experiments are necessary to estimate a
gradient of the criterion function.
Although the main application of IFT is controller tuning (optimization starting from an initial controller), it is successfully used for model-free and model-based controller design as well. The IFT procedure was primarily developed for tuning of single-input single-output (SISO) one-degree-of-freedom or two-degree-of-freedom discrete-time controllers.
This presentation:
- Recalls basic IFT
- Presents new developments made on IFT to improve robustness of optimized controllers and to tune controller with feed-forward disturbance rejection.
- Shows realization of the IFT in an interactive software tool made for Electricité de France.
- Gives two application examples to illustrate using of the new theory in practice.
[INMA] 2006-01-31 (14.00 pm) : "Stability Analysis of a Vision-Based Control Design for an Autonomous Mobile Robot"
At Euler building
Speaker :
Jean-Baptiste COULAUD
(CESAME)
Abstract :
We propose a simple control design allowing
a mobile robot equipped with a camera to track a line on the ground.
The control algorithm as well as the image processing algorithm are very simple.
We discuss the existence and the practical stability of an equilibrium trajectory of the robot when tracking
a circular reference line. We then give a complementary analysis for arbitrary
reference lines with bounded curvature. Experimental results confirm the theoretical analysis.
[INMA] 2006-01-19 (17.00 pm) : Colloque MAPA/CESAME - Nonlinearity and controllability
At Bât.de Hemptinne, Aud.Ch. de la Vallée Poussin (CYCL 01)
Speaker :
Jean-Michel Coron (Université de Paris-Sud)
Abstract :
For finite dimensional control systems, one knows many powerful sufficient conditions for local controllability of
a nonlinear control system.
This is not the case in infinite dimension, where, roughly speaking, the only known general result is that, if the linearized
control system at an equilibrium is controllable, then the nonlinear control system is locally controllable at the
equilibrium.
We present in this talk some new methods to get controllability results for some control systems modeled by partial
differential equations even if the linearized control system around the equilibrium is not controllable.
[INMA] 2005-12-20 (14.00 pm) : Transforming vision into a geometrically optimal reach plan
At Auditoire Euler
Speaker :
Blohm, Gunnar
Abstract :
A fundamental question in neuroscience is how the brain
transforms visual signals into accurate reach commands.
Many theories exist, but the complete three-dimensional
(3D) geometry linking the eyes to the head and shoulder
has never been formally modeled for reaching. Here, I
developed such a model and tested it experimentally against
the predictions of one popular alternative, the direct
transformation hypothesis, which assumes that reach plans
in eye coordinates can be used directly to control the limb.
My new model optimally accounted for the 3D orientations of
the eyes and head. In contrast, a 3D version of the direct
transformation hypothesis predicted large reaching errors.
These error patterns were never observed in human subjects.
This demonstrates that the brain uses internal estimates of
eye and head configurations to optimize the reach plan and
places constraints on algorithms that attempt to use brain
signals for the neural control of arm prostheses.
I will start introducing the neurophysiological and behavioral
background of visuo-motor transformations and provide some details
about the mathematical formalism (dual quaternions) I used for the
modeling part of this study. Dual quaternions are usually utilized
in image analysis and robotic control because of their advantageous
mathematical and numerical properties. They represent a unified
formalism describing translations and rotations but avoiding the
non-commutativity problems of rotations. At the end of the presentation,
I will also spend some time discussing the implications of this work on
our understanding of visuo-motor transformations.
[INMA] 2005-12-13 (15.15 pm) : Application of asymptotic expansions to calculate equivalent surfaces stresses and heat flux in 2D induction heating systems
At Auditoire Euler
Speaker :
Francois Bioul (CESAME)
Abstract :
In induction heating processes the radio frequency ac electric
current imposed inside the inductor(s) generates an alternating
electromagnetic field in the ambient gas and within a very thin
layer located beneath the surface of all bounding electrically
conducting components. Since the electromagnetic field can only penetrate
into a thin magnetic skin located beneath the surface inside the conductors,
the generated heat and stresses are concentrated in this region. If the skin
depth is relatively small, equivalent stresses and heat flux - to be imposed at
the conductor surface - can be calculated from the electromagnetic field expansions
by solving the Navier-Stokes and energy equations with asymptotic expansions
and applying an adapted evaluation technique.
Seminars
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