 |
|
Publications, papers published in February 1999/communications publiées en février 1999
- 1
-
P. Apkarian and H. D. Tuan.
Relaxations of parametrized LMIs with control applications.
International Journal of Robust and Nonlinear Control,
9(2):59-84, February 1999.
A wide variety of problems in control system theory fall within the
class of parametrized linear matrix inequalities (LMIs), that is LMIs whose
coefficients are functions of a parameter confined to a compact set. However,
in contrast to LMIs, parametrized LMI(PLMIs) feasibility problems involve
infinitely many LMIs hence are very hard to solve. In this paper, we propose
several effective relaxation techniques to replace PLMIs by a finite set of
LMIs The resulting relaxed feasibility problems thus become convex and hence
can be solved by very efficient interior point methods. Applications of these
techniques to different problems susch as robustness analysis, or Linear
Parameter Varying (LPV) control are then thoroughly discussed and illustrated
by examples.
- 2
-
D. Alazard and P. Apkarian.
Exact observer based structures for arbitrary compensators.
International journal of Robust and Nonlinear Control,
9(2):101-118, February 1999.
In this paper some new techniques for détermining the observer based
or LQG form of any compensator with arbitary order are discussed. The
practical appeal of such tecniques is that they allow for a simplified
implementation and reduced memory storage of general controllers and offer
additional flexibility for hendling gain scheduling and input saturation
constraints as compensator states become meaningful variables. The derived
observed based controllers are input output equivalent to the original
controller but wxith and explicit separated estimation control structure.
Such structures involve both static control and estimation gains with an
extra Youla parameter that can be either static or dynamic. The proposed
techniques are applicable both in continuous and discrete time, to full order
controllers , that is controllers whose order is the same as the plant's
order but also to augmented and reduced order controllers whose oders are
greater or smaller respectively Necessary conditions to apply this general
controller equivalence principle are derived. The interest and practicality
of such techniques are then investigated with regards to the LQG implentation
of Hinfini and ù controllers classes or controllers that do not generally
enjoy ease of implementation.
- 3
-
E. Bensana, M. Lemaître, G. Verfaillie, and N. Bataille.
Sharing the use of a satellite under quota constraints: an overview
of methods.
In 2nd International Symposium on Spacecraft Ground Control and
Data Systems (SCDII), Foz do Iguaçu, Brazil, 8 - 12 February 1999. INPE.
The purpose of this paper is to present different methods to deal
with a decision problem characterized by the exploitation of an Earth
observation satellite which must be shared between the agents which cofunded
it. The problem is to decide on the daily selection of a subset of pictures
which could be taken the next day considering the satellite trajectory. This
subset must satisfy three kinds of constraints: physical problem (hard)
constraints; efficiency constraints, aiming at maximizing the satisfaction of
each agent; and a fairness constraint, which is ideally satisfied when each
agent receives an amount of the resource exactly proportional to its
financial contribution. Efficiency and fairness constraints are usually
antagonistic. Although fair division problems have received considerable
attention for a long time, especially from microeconomists, this specific
problem does not fall entirely within a classical approach, because the
candidate pictures may be incompatible and also because a picture is only of
value to the agent requesting it. We investigate and propose different ways
for solving this share problem: regulation, mono-objective optimization with
priority to fairness or to efficiency, multi-criteria optimization.
- 4
-
B. Cabon, S. de Givry, L. Lobjois, T. Schiex, and J. P. Warners.
Radio link frequency assignment.
Constraints, An International Journal, 4(1):79-89, February
1999.
The problem of radio frequency assignment is to provide communication
channels from limited spectral resources whilst keeping to a minimum the
interference suffered by those whishing to communicate in a given radio
communication network. This problem is a combinatorial (NP-hard) optimization
problem. In 1993, the CELAR (the French "Centre d'Électronique de
l'Armement") built a suite of simplified versions of Radio Link Frequency
Assignment Problems (RLFAP) starting from data on a real network. Initially
designed for assessing the performances of several Constraint Logic
Programming languages, these benchmarks have been made available to the
public in the framework of the European EUCLID project CALMA (Combinatorial
Algorithms for Military Applications). These problems should look very
attractive to the CSP community: the problem is simple to represent, all
constraints are binary and involve finite domain variables. They nevertheless
have some of the flavors of real problems (including large size and several
optimization criteria). This paper gives essential facts about the CELAR
instances and also introduces the GRAPH instances which were generated during
the CALMA project.
- 5
-
G. Verfaillie, E. Bensana, C. Michelon-Edery, and N. Bataille.
Dealing with uncertainty when managing an earth observation
satellite.
In 2nd International Symposium on Spacecraft Ground Control and
Data Systems - SCD II, Foz de Iguaçu (Brésil), 8 - 12 February 1999. INPE,
AEB.
The possible presence of clouds is the main origin of uncertainty
when managing earth optical observation satellites. Forgetting it can lead to
poor results in terms of really achieved photographs. In this paper, we show
how a mathematical approach, drawn from the Markov Decision Process
framework, allows us to define a rational way of taking in account this
uncertainty in the daily optimization process. Keywords : planning,
uncertainty, markov decision process.
|
