NAPS: a Nomadic and Accurate Positioning System

International audienceProviding accurate pose estimation over time in various and unknown environments is a key component to the realization of autonomous missions where an absolute positioning system (like GPS) is not available. A lot of work has been done in that field where Simultaneous Localization And Mapping systems (SLAM) are still highly environment-dependent and computationally expensive. However, a major issue in SLAM solutions is the drift that appears in their odometry, due to error accumulation in the successive pose estimates. This may imply significant errors in the environment reconstruction or mission success. In this paper, a Nomadic and Accurate Positioning System (NAPS), based on the collaboration of mobile robots and their mutual sensing, is proposed. The originality and advantage of our solution is to provide a motion capture system with the nomadic ability. The result is environment-independent, computationally efficient, accurate and mobile. The system follows one or several mobile robots (explorers) and provides accurate positioning all along their mission. The NAPS is described as well as its moving process, and its accuracy is confirmed through a series of experiments, validating the whole approach

Chronique de la Section Vendéenne

Daugé R. Chronique de la Section Vendéenne. In: Norois, n°10, Avril-Juin 1956. pp. 243-246

Systèmes Cyber-Physiques autonomes et communicants en milieux inconnus :Application à l’exploration par robots mobiles

Thèse confidentielle jusqu'au 31 décembre 2021This document retraces all the work and contributions made in the context of autonomous robotic exploration of unknown environments. An analysis of the state of the art has led us to move away from the classical paradigms of simultaneous positioning and mapping (SLAM) algorithms. These approaches require a heavy parameterization that can only be mastered by specialists. In addition, current systems are all subject to the problem of data association. The proposed positioning system is inspired by ancestral techniques of techniques of surveyors, as well as the measurement in active cooperation between ships and lighthouses. Therefore, the use of several robots measuring their relative positions collaboratively, thus forming a positioning network has allowed to build a robust positioning system, independent of the environment. This work presents the evaluation of the system, as well as its application to cartography, leading to the implementation of a complete SLAM system. Several original algorithms allowing the optimization of the placement of elements forming the positioning network in space are also presented. The presented work has thus led to a functional prototype, tested and evaluated in real world.Ce document retrace l’ensemble du travail et des contributions effectuées dans le cadre de l’exploration robotique autonome d’environnements inconnus. Une analyse de l’état de l’art nous a poussé à nous éloigner des paradigmes classiques des algorithmes de positionnement et cartographie simultanés (SLAM en anglais). Ces approches nécessitent en effet un lourd paramétrage maîtrisable uniquement par des spécialistes. De plus, les systèmes actuels sont tous soumis au problème d’association de données. Le système de positionnement proposé s’inspire ainsi de techniques ancestrales de géomètres, ainsi que de la mesure en coopération active entre les bateaux et les phares. Ainsi, l’emploi de plusieurs robots mesurant collaborativement leurs positions relatives, formant ainsi un réseau de positionnement a permis de construire un système de positionnement robuste, indépendant de l’environnement. Ce travail présente l’évaluation du système, ainsi que son application à la cartographie, conduisant à la mise en place d’un système de SLAM complet. Des algorithmes originaux permettant l’optimisation du placement des éléments formant le réseau de positionnement dans l’espace sont également présentés. Le travail présenté a ainsi abouti à un prototype fonctionnel, testé et évalué dans des conditions réelles

Impact neurobiologique de la séparation mère/nouveau-né chez le rongeur

Chez les mammifères, les liens entre la mère et le nouveau-né sont d’une importance fondamentale dans le développement harmonieux de la progéniture. Cela rend les modèles murins de séparation mère/nouveau-né d’un grand intérêt dans le cadre des hypothèses neuro-développementales des affections psychiatriques. Des séparations longues tendent à installer, chez le raton devenu adulte, des troubles anxieux, « dépressifs », et une conduite de dépendance aux drogues. Les analyses neurobiologiques montrent une perturbation de nombreux systèmes neuronaux limbiques, en particulier neuropeptidergiques, dont l’explication pourrait se trouver dans l’impact du stress précoce sur le développement cérébral. La mise en place de modèles prenant en compte les facteurs environnementaux précoces pourrait contribuer à une meilleure prévention/prédiction des troubles mentaux et améliorer nos stratégies thérapeutiques

A new free volume model for dynamic viscosity of dense fluids versus pressure and temperature. Extension to a predictive model for not very associative mixtures

cited By 4International audienceThis article presents the extension of a viscosity model to mixtures. This model, based on the free volume concept, has been previously validated for pure dense components. This model involves three physical constants for each pure compound. If the viscosity is known at a reference pressure and temperature it is sufficient to use two constants per pure compound. The model has been adapted in order to obtain a predictive expression able to represent with accuracy the pressure-temperature variations of the dynamic viscosity of a mixture knowing only the characteristic parameters of each pure compound and the composition. The database used contains 3440 data points relative to 15 binaries, 4 ternaries and I system with more than three constituents. The model's results are also compared with those calculated from the very well-known Grunberg and Nissan's mixing law, and Katti and Chaudhri's mixing law

Liens entre microbiote intestinal et comportement de type anxiodépressif chez le rongeur

International audienc

The CCK(2) agonist BC-264 decreases predatory fear freezing at high but not low dosages in PVG hooded rats during initial exposure to a cat.

BC-264 a CCK(2) agonist reverses chronically developed habituated predatory fear freezing behavior in PVG hooded rats. However, the acute effects of BC264 have not been previously examined. The effects of BC-264 (0.1-30microg/kg) on the mean percentage of PVG hooded rat freezing during an initial first time 20min cat exposure were calculated. At higher doses (15 or 30microg/kg) but not lower doses (0.1-1microg/kg) BC264 statistically significantly decreased freezing compared to control (p<0.001)