Planification de trajets pour un véhicule à guidage automatique holonome à parcours libre

Les véhicules à guidage automatique (Automated Guided Vehicule - AGV) sont de plus en plus répandus dans le milieu industriel. Ces véhicules permettent le transport automatisé des biens dans une usine, ce qui libère de la main d’œuvre qui peut réaliser des tâches ayant une plus grande valeur ajoutée. Récemment, certains manufacturiers ont débuté la mise en marché d'AGV holonomes. Ces derniers peuvent se déplacer latéralement, libérant l'orientation du véhicule pendant ses mouvements. Ce degré de liberté supplémentaire n’est toutefois pas géré par les planificateurs de trajectoires existants. En absence d’obstacles pour limiter la rotation de l’AGV, ce dernier a tendance à pivoter de manière erratique lorsqu’il se déplace. Cela entraîne un inconfort chez les personnes à proximité et peut endommager une charge fragile placée sur le véhicule. Aussi, les logiciels existants ne permettent pas à un utilisateur de communiquer au véhicule les règles de circulation spécifiques à un milieu de travail. Les travaux présentés dans ce mémoire se découpent en trois volets. D’abord, un planificateur global, qui trouve un trajet composé d’une suite de points de cheminement (combinaison d’une position et d’une orientation) entre un point de départ et un point d’arrivée, est décrit. Ce planificateur est livré sous la forme d’un paquet pouvant être utilisé directement avec les logiciels de navigation existant dans l’environnement du Robotic Operating System (ROS). L’algorithme utilise des intervalles d’orientation au lieu de valeurs discrètes afin de réduire le nombre de nœuds dans le graphe A*. Ensuite, un planificateur local existant dans ROS est modifié pour les besoins des AGV holonomes. Il permet de calculer les commandes de vitesses qui doivent être adoptées par l’AGV afin de suivre le trajet calculé par le planificateur global. Il est livré comme une version discrète d’un paquet ROS et remplace l’original. Le bon fonctionnement des planificateurs est validé en simulation et sur un véritable AGV. Enfin, une preuve de concept en simulation est réalisée pour la gestion des règles de circulation. Une interface permet de définir des comportements par zones, qui sont ensuite encodées dans des grilles d’occupation et sauvegardées sur le robot. Un logiciel de navigation adapté se réfère ensuite à ces grilles pour ajouter la bonne orientation au trajet et pour circuler aux bons endroits. Ce projet de recherche a montré qu’il est possible d’exploiter l’holonomie d’un AGV dans un logiciel de navigation intégré à la pile de navigation ROS originale. Toutefois, certains enjeux demeurent au niveau du planificateur local qui tente d’établir un compromis entre le suivi exact du trajet et la progression vers le but. Comme travaux futurs, il serait intéressant d’ajouter la gestion de l’interaction avec les systèmes de sécurité présents sur les véhicules industriels

Understanding patchy landscape dynamics: Towards a landscape language

International audiencePatchy landscapes driven by human decisions and/or natural forces are still a challenge to be understood and modelled. No attempt has been made up to now to describe them by a coherent framework and to formalize landscape changing rules. Overcoming this lacuna was our first objective here, and this was largely based on the notion of Rewriting Systems, also called Formal Grammars. We used complicated scenarios of agricultural dynamics to model landscapes and to write their corresponding driving rule equations. Our second objective was to illustrate the relevance of this landscape language concept for landscape modelling through various grassland managements, with the final aim to assess their respective impacts on biological conservation. For this purpose, we made the assumptions that a higher grassland appearance frequency and higher land cover connectivity are favourable to species conservation. Ecological results revealed that dairy and beef livestock production systems are more favourable to wild species than is hog farming, although in different ways. Methodological results allowed us to efficiently model and formalize these landscape dynamics. This study demonstrates the applicability of the Rewriting System framework to the modelling of agricultural landscapes and, hopefully, to other patchy landscapes. The newly defined grammar is able to explain changes that are neither necessarily local nor Markovian, and opens a way to analytical modelling of landscape dynamics

ODAS: Open embeddeD Audition System

Artificial audition aims at providing hearing capabilities to machines, computers and robots. Existing frameworks in robot audition offer interesting sound source localization, tracking and separation performance, but involve a significant amount of computations that limit their use on robots with embedded computing capabilities. This paper presents ODAS, the Open embeddeD Audition System framework, which includes strategies to reduce the computational load and perform robot audition tasks on low-cost embedded computing systems. It presents key features of ODAS, along with cases illustrating its uses in different robots and artificial audition applications

Diagnosis of an Inertial Measurement Unit Based on Set Membership Estimation

International audienceThis paper compares two diagnostic techniques applied to MEMS sensors of an Inertial Measurement Unit (IMU). The sensors considered in this study are a triaxis accelerometer and a triaxis magnetometer. Note that rate gyros measurements are not considered here. The goal of the IMU is to sense the attitude of a rigid body on which it is embedded. The measurement equations are non-linear in the attitude parameters which are first estimated from five over six measurements. Then, each measurement equation together with the estimated parameters, provides an predicted measurement. Lastly, the residual is computed and analyzed with a signature table to detect and isolate the fault. Two estimation techniques are implemented. The first approach is based on parameter estimation with nonlinear optimization technique while the second one makes use of set membership estimation

Grassland management assessments.

<p>Compilation of the five landscape pattern indices for the four landscape scenarios: random (<i>A</i>), intensive dairy and beef livestock production (<i>B</i>), extensive dairy and beef livestock production (<i>C</i>), and hog production (<i>D</i>) systems. Indices concern heterogeneity indices (diversity and connectivity) as well as grassland area indices. Favourable index values in terms of grassland management are shown in bold. The last scenarios <i>E</i> and <i>G</i> are given in the text and not listed here, as they concern rather different landscape managements.</p

A patchy landscape sequence with its changing topology.

<p>A simple patchy landscape viewed by its patch mosaic (a) and its topological graph (b) at time step t, and at time step t+1 (c and d). The node properties displayed in the graph are the main patch attribute (the land cover, in gray scale), and the patch surface (the disc size). Vertical arrows represent time changes of the landscape (1a, 1c) and dashed horizontal arrows represent the link between geometrical mosaics and topological graphs (1b, 1d). Here, merges and random (land cover) rotations, both with a probability p = 0.5, have been applied between the two time steps.</p

The landscape language syntax.

<p>Here is the proposed syntax used in this paper and describing the rewriting rules to be applied on landscape units. It is an exhaustive view of symbols used in this work on landscape dynamics with the DYPAL landscape modelling platform.</p

A Novel Approach for Quantifying Cancer Cells Showing Hybrid Epithelial/Mesenchymal States in Large Series of Tissue Samples: Towards a New Prognostic Marker

In cancer biology, epithelial-to-mesenchymal transition (EMT) is associated with tumorigenesis, stemness, invasion, metastasis, and resistance to therapy. Evidence of co-expression of epithelial and mesenchymal markers suggests that EMT should be a stepwise process with distinct intermediate states rather than a binary switch. In the present study, we propose a morphological approach that enables the detection and quantification of cancer cells with hybrid E/M states, i.e. which combine partially epithelial (E) and partially mesenchymal (M) states. This approach is based on a sequential immunohistochemistry technique performed on the same tissue section, the digitization of whole slides, and image processing. The aim is to extract quantitative indicators able to quantify the presence of hybrid E/M states in large series of human cancer samples and to analyze their relationship with cancer aggressiveness. As a proof of concept, we applied our methodology to a series of about a hundred urothelial carcinomas and demonstrated that the presence of cancer cells with hybrid E/M phenotypes at the time of diagnosis is strongly associated with a poor prognostic value, independently of standard clinicopathological features. Although validation on a larger case series and other cancer types is required, our data support the hybrid E/M score as a promising prognostic biomarker for carcinoma patients.info:eu-repo/semantics/publishe