59 research outputs found
Détection et Reconnaissance des Gestes Emblématiques
Session "Atelier IHMA"National audienceDans cette contribution, nous présentons un système de reconnaissance en ligne de gestes emblématiques et son utilisation pour le contrôle d'un robot mobile. Ce système comporte quatre sous-systèmes : un premier qui permet de détecter la personne et d'extraire les mouvements de la partie supérieure de cette personne. Un second, permet d'isoler les mouvements, une troisième permet de reconnaître un des mouvements appris a priori. Enfin le dernier module, traduit les mouvements reconnus en termes de contrôle d'un robot mobile à roues. Dans notre approche, nous avons surtout traité du problème de la généralisation : faire l'apprentissage sur une base réduite de personnes et utiliser cette connaissance pour reconnaître n'importe quelle personne, indépendamment de sa morphologie, de son âge, de son sexe et de son positionnement par rapport au capteur. Nous détaillons les résultats obtenus pour la reconnaissance ainsi que l'utilisation du système dans des scenarios de contrôle d'un robot
SyTroN: a virtual classroom for collaborative and distant e-learning systemby teleoperating real devices
Distant E-learning is a main issue nowadays, and it is strongly motivated by social and economical considerations. The increased people mobility and the reduction of educational costs push to develop ad hoc solutions enabling to access to knowledge regardless to geographical situation and economical capabilities. These parameters should not be limits for good training: learning material's pertinence and efficiency have to remain the core of educational activities. In this paper we address the problem through SyTroN: a tele-learning system. This system combines virtual reality and teleoperation techniques to offer an open platform with two main objectives. The first one is to propose intuitive virtual classrooms/desks, including a real teacher supervision and supporting collaborative and individual distant learning. The second goal is to place learners in real conditions with remote connections to real devices allowing distant experimentations. Both goals participate to increase learning impacts and to reduce costs, that is, sharing costly real devices from anywhere at any time. After 5 years of development, our work has been validated by an extensive use at a high engineering school. In situ tests and learning impact studies have been done. They show some advantages and some drawbacks of our global solution
A unified SLAM solution using partial 3D structure
Good quality of environment mapping demands modelling the associated environment nearly to its 3D originality. This paper presents a unified Simultaneous Localisation And Mapping (SLAM) solution based on partial 3D structure. As compared to existing representations such as grid based mapping, the novelty of the proposed unified approach lies in estimation, representation and handling of compact partial 3D features-based map model for a team of robots that are working in an unknown environment with unknown poses. The approach replies on a camera to perceive the environment and a 2D laser sensor to generate a SLAM solution with partial 3D features based representation. Extended Kalman Filter (EKF) estimates the robot pose based on its motion model and map of the explored environment. The solution has been tested in an indoor environment on two identical custom-developed robots. Experimental results have demonstrated efficacy of the approach. The presented solution can be easily applied on a distributed/centralized robotic system with ease of data handling and reduced computational cost
Combination of pulsed laser ablation and inert gas condensation for the synthesis of nanostructured nanocrystalline, amorphous and composite materials
A new instrument combining pulsed laser ablation and inert gas condensation for the production of nanopowders is presented. It is shown that various nanostructured materials, such as regular metallic, semiconducting, insulating materials, complex high entropy alloys, amorphous alloys, composites and oxides can be synthesized. The unique variability of the experimental set-up is possible due to the reproducible control of laser power (pulse energy and repetition rate), laser ablation pattern on the target, and experimental conditions during the inert gas condensation, all of which can be controlled and optimized independently. Microstructure analysis of the as-prepared composite and amorphous Ni(60)Nb(40) nanopowders establishes the instrument's ability for the synthesis of materials with unique compositions and atomic structure. It is further shown that small variations of the synthesis parameters can influence materials properties of the final product, in terms of particle size, composition and properties. As an example, the laser power has been used to control the magnetic properties of amorphous Ni(60)Nb(40) nanopowders. A few selected examples of the manifold possibilities of the new synthesis apparatus are presented in this report together with detailed structural characterization of the produced nanopowders
Unveiling the Local Atomic Arrangements in the Shear Band Regions of Metallic Glass
The prospective applications of metallic glasses are limited by their lack of ductility, attributed to shear banding inducing catastrophic failure. A concise depiction of the local atomic arrangement (local atomic packing and chemical short‐range order), induced by shear banding, is quintessential to understand the deformation mechanism, however still not clear. An explicit view of the complex interplay of local atomic structure and chemical environment is presented by mapping the atomic arrangements in shear bands (SBs) and in their vicinity in a deformed Vitreloy 105 metallic glass, using the scanning electron diffraction pair distribution function and atom probe tomography. The results experimentally prove that plastic deformation causes a reduction of geometrically favored polyhedral motifs. Localized motifs variations and antisymmetric (bond and chemical) segregation extend for several hundred nanometers from the SB, forming the shear band affected zones. Moreover, the variations within the SB are found both perpendicular and parallel to the SB plane, also observable in the oxidation activity. The knowledge of the structural–chemical changes provides a deeper understanding of the plastic deformation of metallic glasses especially for their functional applications and future improvements
Denominators of Eisenstein cohomology classes for GL_2 over imaginary quadratic fields
We study the arithmetic of Eisenstein cohomology classes (in the sense of G.
Harder) for symmetric spaces associated to GL_2 over imaginary quadratic
fields. We prove in many cases a lower bound on their denominator in terms of a
special L-value of a Hecke character providing evidence for a conjecture of
Harder that the denominator is given by this L-value. We also prove under some
additional assumptions that the restriction of the classes to the boundary of
the Borel-Serre compactification of the spaces is integral. Such classes are
interesting for their use in congruences with cuspidal classes to prove
connections between the special L-value and the size of the Selmer group of the
Hecke character.Comment: 37 pages; strengthened integrality result (Proposition 16), corrected
statement of Theorem 3, and revised introductio
Simulation of an under-actuated fish-like robot controlled by an adaptive frequency oscillator inside a Karman Vortex Street
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