All Years Seminars
[INMA] 2015-06-16 (14.00) : Numerical optimal control on Lie groups with applications to constrained motion planning of multiple vehicles in SE(3)
At Euler building (A002)
Speaker :
Alessandro Saccon (Eindhoven University of Technology (TU/e))
Abstract : The Lie group Projection Operator Approach is a recently developed iterative algorithm for solving continuous-time optimal control problems on Lie groups. In the talk, we will discuss the main ideas lying behind this numerical method. In particular, we will detail the role played by the second covariant derivative of a map between Lie groups in obtaining a linear-quadratic approximation to the optimal control problem. This approximation is key to compute the descent direction at each iteration of the algorithm. The implementation of this numerical method on a computer requires the integration of the system dynamics and of a differential Riccati equation (DRE) associated with the linear-quadratic approximation of the optimal control problem. Numerical examples will be provided to demonstrate the effectiveness of the numerical method and its quadratic converge rate to local minima satisfying the second order sufficient conditions (SSC) for optimality. The application of the algorithm to solving minimum energy constrained motion planning problems or multiple vehicles will conclude the talk.
[INMA] 2015-05-05 (14.00) : System identification in the behavioral setting
At Euler building (A002)
Speaker :
Ivan Markovsky (ESAT/KULeuven )
Abstract : System identification is a fast growing research area that encompasses a broad range of problems and solution methods. It is desirable to have a unifying setting and a few common principles that
are sufficient to understand the currently existing identification methods. The behavioral approach to systems theory and control, put forward in the mid 80's, is such a unifying setting. Till recently,
however, the behavioral approach lacked supporting numerical solution methods. In the last 10 years, the structured low-rank approximation setting was used to fulfill this gap. In this talk, we summarize recent
progress on methods for system identification in the behavioral setting and pose some open problems. First, we show that errors-in-variables and output error system identification problems are equivalent to Hankel
structured low-rank approximation. Then, we outline three generic solution approaches: 1) methods based on local optimization, 2) methods based on convex relaxations, and 3) subspace methods. A specific example
of a subspace identification method---data-driven impulse response computation---is presented. In order to achieve the desired unification, the classical ARMAX identification problem should also be formulated as
a structured low-rank approximation problem. This is an outstanding open problem.
[INMA] 2015-04-28 (14.00) : Les mathématiques arabes, passerelles entre les cultures euro-méditerranéennes
At Sciences 10
Speaker :
Ahmed Djebbar (CNRS, Université des Sciences et Technologies de Lille, ex-ministre algérien de l'Education et de la Recherche)
Abstract : Partant des recherches réalisées ces dernières décennies sur l'histoire des activités scientifiques arabes entre le VIIIe et le XVe siècle, la conférence
se propose de présenter les éléments essentiels concernant la circulation, autour de la Méditerranée, d'une partie importante des savoirs et des savoir-faire mathématiques,
hérités des civilisations antérieures au VIIIe siècle ou produits dans les foyers scientifiques de l'empire musulman. Nous donnerons également un aperçu sur les contacts
et les échanges qui ont accompagné cette circulation, à différents moments et plus particulièrement à partir du XIIe siècle, faisant des activités mathématiques une des
plus belles opportunités du dialogue interculturel entre les sociétés de la rive sud et celles de la rive nord de la Méditerranée.
[INMA] 2015-04-21 (14.00) : On set theory methods for dynamical systems: stability analysis, controller synthesis and construction of invariant sets
At Euler building (A002)
Speaker :
Nikolaos Athanasopoulos (UCL)
Abstract : Tools from set theory involving reachability mappings and different variants of invariant sets in the state space, are systematically being used for
stability analysis and controller synthesis, especially for systems under input/state constraints and complex specifications. In this talk, two contributions
among these lines will be discussed, concerning a) the stability analysis and control synthesis problem for discrete time homogeneous inclusions and
b) the construction of new property preserving monotonic sequences of invariant sets for constrained systems. The theoretical results will be illustrated
to relevant classes of systems in control, such as linear discrete and continuous-time systems, cone-wise linear systems, switched systems under constrained
switching and time-delay systems.
[INMA] 2015-03-31 (14.00) : Bayesian networks, Information-theoretic networks and Probabilistic logic
At Euler building (A002)
Speaker :
Patrick Meyer (ULg)
Abstract : In this talk, causality concepts that are used in Bayesian networks inference will be connected to information-theoretic network inference algorithms used in Systems Biology. The latter approaches have a good trade-off accuracy-computational complexity. However, a promising improvement, centered around a statistical version of the logical implication, will be introduced in the last part of this talk.
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