Unstationnary control of a launcher using observer-based structures

This paper deals with the design of a gain-scheduled controller for the attitude control of a launcher during atmospheric flight. The design is characterized by classical requirements such as phase/gain margins and flexible mode attenuations as well as time-domain constraints on the response of angle of attack to a worstcase wind profile. Moreover, these requirements must be fulfilled over the full atmospheric flight envelope and must be robust against parametric uncertainties. In order to achieve this goal, we propose a method based on minimal observer-based realizations of arbitrary stabilizing compensators. An original technique to assign the closed-loop dynamics between the state-feedback dynamics and the state-estimation dynamics is presented for the H∞ compensators case. The structure is used to mix various specifications through the Cross Standard Form(CSF) and to perform a smooth gain scheduling interpolation through an Euler-Newton algorithm of continuation

De l'utilisation de la structure estimation/commande pour le pilotage instationnaire d'un lanceur spatial

Dans cet article, nous nous intéressons au développement de techniques ayant trait à la mise sous forme LQG équivalente de correcteurs stabilisants. Dans un premier temps nous nous concentrerons plus particulièrement sur la transformation de correcteurs issus d'une synthèse Hinfinty. Nous proposons une méthode originale pour effectuer le choix des dynamiques d'estimation et de commande du correcteur équivalent en s'appuyant sur les résultats d'une synthèse H2. Puis nous proposerons une définition en temps discret de la Forme Standard de Passage (CSF) qui s'appuie également sur la paramétrisation de Youla sur la structure estimation /commande. Nous la présenterons en tant qu'outil méthodologique pour la mise en forme d'un problème multi-objectif. Nous mettrons en application la CSF sur le problème de pilotage d'un lanceur et nous montrerons l'intérêt de l'utilisation de la structure estimation/commande dans le cadre de l'inter-polation de correcteur pour le pilotage instationnaire

Gated networks: an inventory

Gated networks are networks that contain gating connections, in which the outputs of at least two neurons are multiplied. Initially, gated networks were used to learn relationships between two input sources, such as pixels from two images. More recently, they have been applied to learning activity recognition or multi-modal representations. The aims of this paper are threefold: 1) to explain the basic computations in gated networks to the non-expert, while adopting a standpoint that insists on their symmetric nature. 2) to serve as a quick reference guide to the recent literature, by providing an inventory of applications of these networks, as well as recent extensions to the basic architecture. 3) to suggest future research directions and applications.Comment: Unpublished manuscript, 17 page

Launcher attitude control: discrete-time robust design and gain-scheduling

In this paper, a robust multi-objective design for the control of a launcher during atmospheric flight is investigated. This approach is based on the Cross Standard Form formulation which allows to incorporate the various specifications of the launcher problem in a streamlined manner. An important feature of this approach is that a non-conventional LQG/LTR approach, required to satisfy time-domain specifications, can be embedded into a more general standard problem in order to account for frequency-domain robustness constraints. The specific form of this standard problem is also very interesting for gain scheduling

Stable continuous branching processes with immigration and Beta-Fleming-Viot processes with immigration

21 pagesInternational audienceBranching processes and Fleming-Viot processes are two main models in stochastic population theory. Incorporating an immigration in both models, we generalize the results of Shiga (1990) and Birkner et al. (2005) which respectively connect the Feller diffusion with the classical Fleming-Viot process and the alpha-stable continuous state branching process with the Beta(2-alpha, alpha)-generalized Fleming-Viot process. In a recent work, a new class of probability-measure valued processes, called M-generalized Fleming-Viot processes with immigration, has been set up in duality with the so-called M-coalescents. The purpose of this article is to investigate the links between this new class of processes and the continuous-state branching processes with immigration. In the specific case of the $\alpha$-stable branching process conditioned to be never extinct, we get that its genealogy is given, up to a random time change, by a Beta(2-alpha, alpha-1)-coalescent

Le Parlement et les citoyens

Ce numéro des Cahiers du CEVIPOF interroge les liens entre l’institution parlementaire et les électeurs entre deux élections à travers des contributions de politistes, historiens ou de praticiens. Une première partie met à jour différents types d’attitudes et de comportements des électeurs français vis-à-vis du Parlement. Elle permet de dépasser le constat connu d’une profonde défiance citoyenne pour éclairer différentes types de circulation entre élus et électeurs. La seconde partie questionne la façon des citoyens sont perçus, sollicités voire craints depuis le Parlement. Elle prend la mesure des multiples stratégies de communication des assemblées mais aussi de leur adaptation, parfois réticente, aux mouvements d’opinion, touchant par l’exemple aux règles éthiques, ou aux technologies modernes de l’information. Au final, ces contributions mettent à jour la profonde ambivalence du lien représentatif hors élections

Dark Optical Lattice of Ring Traps for Cold Atoms

We propose a new geometry of optical lattice for cold atoms, namely a lattice made of a 1D stack of dark ring traps. It is obtained through the interference pattern of a standard Gaussian beam with a counter-propagating hollow beam obtained using a setup with two conical lenses. The traps of the resulting lattice are characterized by a high confinement and a filling rate much larger than unity, even if loaded with cold atoms from a MOT. We have implemented this system experimentally, and obtained a lattice of ring traps populated with typically 40 atoms per site with a life time of 30 ms. Applications in statistical physics, quantum computing and Bose-Einstein condensate dynamics are conceivable.Comment: 4 pages, submitted to PR

Shortcomings of an idealized urbanity : ghost urban areas and the asynchronous territorial development of Hanoi

This paper examines the recent emergence, on the periphery of Hanoi, of large real estate projects that began construction during the 2000s but have now remained unfinished or, even when completed, largely uninhabited. These “ghost urban areas,” as the local press calls them, epitomize some of the problems which emerged in Hanoi when a model of urban development that aimed at realizing an imagined urban future, formulated by state planning agencies, encountered the highly speculative reality of Vietnam’s property market. Ghost urban areas reveal how the state’s planning orientations and discourse—conveying ideals of urban “modernity,” “civility,” and particularly “synchrony”—instead generated dysfunctional, incomplete, and disconnected places. Based on a survey of thirty-nine ghost urban areas, a cartographic analysis, interviews with key actors, and a critical study of policy documents, this paper reveals multiple scales and forms of what we call “asynchronous territorial developments.” Around Hanoi, these developments involve vast tracts of agricultural lands forcibly appropriated yet left fallow, planned infrastructure and amenities that stay unbuilt for indefinite periods of time, and housing units transacted multiple times among speculators but have remained largely uninhabited and out of reach for a majority of urban households. Ultimately, we interrogate how these various territorial asynchronies, both generated by and plaguing ghost urban areas, shape their livability and inhabitants’ experience