202 research outputs found
Improving rotation behaviour of robotic structures for micro-assembly.
International audienceSerial micro-assembly requires high precision robots able to produce translations and rotations to position and orient objects during assembly. In micro-scale, the translation ranges required are typically up to the millimeter and can be obtained with smart devices (piezomotor, etc...). In the other hand, the rotation ranges stay identical to the macroscale (eg. 90°) and require standard guidings like ball bearings which induce disturbances on the linear position. Thus, the ability to produce high precision robots where translations and rotations are découpled is currently one of the major stake in microassembly. This paper deals with an original modeling of the coupling between rotation and linear position. The geometrical model is presented and two calibration methods are discussed. Our method were tested on a 3 DOF planar robotic systems and the coupling was reduced by 93 %
Culture "dynamique" : impact sur la reconstruction de tissus conjonctifs par génie tissulaire
Des millions de chirurgies de reconstruction sont réalisées chaque année pour remplacer les tissus endommagés. Grâce au génie tissulaire, il est possible de reconstruire du tissu conjonctif humain par la méthode d'auto-assemblage à partir des fibroblastes dermiques (FD) ou des cellules stromales/souches isolées du tissu adipeux (CSTA), sans biomatériau exogène. Dans le but d'optimiser la production des tissus, nous avons évalué l'impact d'une culture dynamique (milieu en mouvement constant) en utilisant une plate-forme agitatrice. Cette approche s'est traduite par la reconstruction de tissus conjonctifs humains 1,8 fois plus épais à partir des CSTA. De plus, cette approche a permis de réduire les délais de reconstruction tissulaire de 2 semaines, ainsi que la production d'équivalents tissulaires plus épais. Bref, la production de tissus conjonctifs humains est donc améliorée par la culture dynamique
Robotic micromanipulation for microassembly : modelling by sequencial function chart and achievement by multiple scale visual servoings.
International audienceThe paper investigates robotic assembly by focusing on the manipulation of microparts. This task is formalized through the notion of basic tasks which are organized in a logical sequence represented by a function chart and interpreted as the model of the behavior of the experimental setup. The latter includes a robotic system, a gripping system, an imaging system, and a clean environment. The imaging system is a photon videomicroscope able to work at multiple scales. It is modelled by a linear projective model where the relation between the scale factor and the magnification or zoom is explicitly established. So, the usual visual control law is modified in order to take into account this relation. The manipulation of some silicon microparts (400 μm×400 μm×100 μm) by means of a distributed robotic system (xyθ system, ϕz system), a two-finger gripping system and a controllable zoom and focus videomicroscope shows the relevance of the concepts. The 30 % of failure rate comes mainly from the physical phenomena (electrostatic and capillary forces) instead of the accuracy of control or the occultations of microparts
Autofocusing-based visual servoing : application to MEMS micromanipulation.
International audienceIn MEMS microassembly areas, different methods of automatic focusing are presented in the literature. All these methods have a common point. Thus, the current autofocusing methods for microscopes need to perform a scanning on all the vertical axis of the microscope in order to find the peak corresponding to the focus (sharpen image). Those methods are time consuming. Therefore, this paper presents an original method of autofocusing based on a velocity control approach which is developed and validated on real experiments
Estimating the 3D orientation of a microgripper by processing the focus data from the images delivered by a videomicroscope.
International audienceVisual servoing is a key technique to automate microassembly tasks since videomicroscope is widely use to recovery informations about the scene. The parts as well as the gripper should be tracked in the images which do not deliver a complete focused view of the objects because of the weakness of the depth-of-field. The paper investigates the problem of computing the 3D orientation of a rigid body by analysing the focus data extracted from the images of a videomicroscope. The solution is based on the shape-from-focus approach. But the modelling stage is simplified, instead of performing a 3D modelling, a 1D modelling is achieved which enables the estimation of the 3D orientation of the object. The concept is applied with success to the tips (70μm width and 1500μm length) of a gripper imaged by a 10 x videomicroscope
Curvature sensing using a hybrid polycarbonate-silica multicore fiber
We report on the development of a novel hybrid glass-polymer multicore fiber integrating three 80 µm polyimide-coated silica fibers inside a 750 µm polycarbonate cladding. By inscribing an array of distributed FBGs along each segment of silica fiber prior to the hybrid fiber drawing, we demonstrate a curvature sensor with an unprecedented precision of 296 pm/m−1 around 1550 nm, about 7 times more sensitive than sensors based on standard 125 µm multicore fibers. As predicted by theory, we show experimentally that the measured curvature is insensitive to temperature and strain. Also, a more precise equation to describe the curvature on a simple bending setup is presented. This new hybrid multicore fiber technology has the potential to be extended over several kilometers and can find high-end applications in 3D shape sensing and structural health monitoring
Herpes viruses in equine pathology: current knowledges and perspectives
In horses, several herpesviruses are responsible for more or less serious conditions, a large number
being subclinical. Two distinct viruses (EHV1 and EHV4) account for the majority of observable disorders
in this species, and are associated with serious economic repercussions. The virus of coital
exanthema is common and occurs in small foci generally self-regulating with simple control
methods. EHV2, with a predominantly respiratory tropism, is not yet recognised as a major pathogen
as it is rarely responsible on its own for serious signs in horses. Its role as a co-factor in respiratory
infections is currently being investigated, and its involvement in triggering inflammatory
reactions in the lungs has been suggested in recent studies. The impact of EHV 1 and EHV 4 in
equine health is very different, as these viruses are present worldwide and all year round. They are
involved in abortions, respiratory conditions, whether acute or subclinical (when they are associated
with poor performance), neonatal diseases, and nervous disorders. In severe equine viral rhinopneumonitis,
they can be fatal. Over the past 15 years, the semiology and epidemiology
approach to these herpes diseases has changed considerably. The development of diagnostic
methods, such as genic amplification (PCR), cryo-cutting or improved serological tests, has helped
practitioners dealing with these infections, which are a real calamity for horse breeders and trainers
alike. Progress has yet to be achieved, particularly in the genetic field, to get a clearer understanding
of the variations in field strains, the development of nervous forms, as well as the mechanisms
of viral reactivation and their consequences on abortion or respiratory infections. Finally,
medical prophylaxis is expected to bring enormous improvement, with the development of vaccines
against these three or four types of virus, protecting horses against their different forms of
expression.Plusieurs Herpèsvirus sont capables de provoquer chez le cheval des maladies plus ou moins graves avec
une grande part d’entre elles sévissant de façon sub-clinique. Deux virus distincts (EHV1 et EHV4), sont à
eux seuls responsables d’une majorité de troubles observables chez les équidés et ayant de graves répercutions
économiques. Le virus de l’exanthème coïtal est courant et sévit par petits foyers qui s’autorégulent
la plupart du temps avec des méthodes de lutte simples. Le virus EHV2, à tropisme principalement
respiratoire, n’est pas encore reconnu comme un agent pathogène majeur dans la mesure ou il induit
rarement seul, des manifestations graves chez le cheval. Ses rôles, en tant que co-facteur d’infections de
l’appareil respiratoire, reste en cours d’étude mais sa place dans le déclenchement de phénomènes
inflammatoires pulmonaires est parfois évoquée et suggérée par certains travaux récents. La situation de
la santé équine vis à vis des deux premiers virus cités est très différente puisque nous pourrons les retrouver
sur l’ensemble de la planète et toute l’année, impliqués dans les avortements, les maladies respiratoires
aiguës ou sub-cliniques (synonyme chez l’adulte de contre-performance), de maladies néonatales
ou de formes nerveuses et parfois mortelles dans les foyers sévères de rhinopneumonie. Ces 15 dernières
années, l’approche sémiologique et épidémiologique des ces maladies herpétiques ont beaucoup évolué
et la mise au point de méthodes de diagnostic telles que l’amplification génique (PCR), les coupes sur
organes ou l’amélioration des méthodes sérologiques aura permis aux praticiens de mieux appréhender
les foyers en élevage ou à l’entraînement, qui sont de véritables fléaux pour les éleveurs ou entraîneurs.
De nombreux progrès restent à accomplir dans le domaine génétique notamment, afin de mieux comprendre
les variations de souches sur le terrain et l’apparition de formes nerveuses de ces maladies ainsi
que les mécanismes de réactivation virale et les conséquences qu’ils entraînent sur les avortements ou les
maladies inflammatoires de l’appareil respiratoire. Enfin, il reste d’énormes avancées à attendre des progrès
de la prophylaxie médicale, qui devra proposer des vaccins protecteurs vis à vis de ces trois ou quatre
types de virus circulant et de leurs différentes formes d’expression chez l’animal
Autofocusing-based visual servoing : application to MEMS micromanipulation.
International audienceIn MEMS microassembly areas, different methods of automatic focusing are presented in the literature. All these methods have a common point. Thus, the current autofocusing methods for microscopes need to perform a scanning on all the vertical axis of the microscope in order to find the peak corresponding to the focus (sharpen image). Those methods are time consuming. Therefore, this paper presents an original method of autofocusing based on a velocity control approach which is developed and validated on real experiments
Emergence of novel equine arteritis virus (EAV) variants during persistent infection in the stallion: Origin of the 2007 French EAV outbreak was linked to an EAV strain present in the semen of a persistently infected carrier stallion
AbstractDuring the summer of 2007, an outbreak of equine viral arteritis (EVA) occurred in Normandy (France). After investigation, a link was suggested between an EAV carrier stallion (A) and the index premise of the outbreak. The full-length nucleotide sequence analysis of a study reference strain (F27) isolated from the lung of a foal revealed a 12,710 nucleotides EAV genome with unique molecular hallmarks in the 5′UTR leader sequence and the ORF1a sequence encoding the non-structural protein 2. The evolution of the viral population in the persistently infected Stallion A was then studied by cloning ORFs 3 and 5 of the EAV genome from four sequential semen samples which were collected between 2000 and 2007. Molecular analysis of the clones confirmed the likely implication of Stallion A in the origin of this outbreak through the yearly emergence of new variants genetically similar to the F27 strain
Equine herpesvirus diseases: relevance and limits of molecular tools
At least five equine herpesviruses are known to infect horses: three alpha herpesviruses (equine herpesvirus-
1, -3 and -4) and two gamma herpesviruses (equine herpesvirus-2 and -5). Equine herpesvirus-
1 is responsible for three clinical presentations: respiratory, abortigenic and neurological. This latter,
widely known as EHV-1 associated, myeloencephalopathy has been thoroughly investigated over the
past years. Most of the studies focused on the relation between the presence of a mutation in ORF
30 coding for DNA polymerase and the expression of the paralytic (neurological) form. Even if this
mutation seems to play a role, other factors related to the host and the environment are certainly
involved in the development of the disease. Equine herpesvirus-4 is better known as the rhinopneumonia
virus and is responsible for a large part of respiratory disorders in young foals. Equine herpesvirus-
3 is responsible for equine coital exanthema, whose transmission through the respiratory tract
is now proven. Equine herpesvirus-2 and -5 are associated with subclinical respiratory diseases in equine
athletes, even though their pathogenic role has yet to be clarified as they were detected in all continents
only relatively recently. The development of molecular genetic tools lead to major progress
in the detection of these viruses, but the differentiation between latent and infectious forms is still
unresolved. Although studies are currently performed on the typing of strains responsible for different
clinical presentations involving equine herpesviruses as well as in other equine viruses (influenza, equine
viral arteritis), there is no international consensus on a phylogenic tree for any of the 5 equine herpesviruses.
Further studies are definitely required to monitor and characterise the different strains
of EHV.Au moins cinq herpèsvirus
équins peuvent infecter le cheval: trois alpha-herpèsvirus (les herpèsvirus 1, 3 et 4) et
deux gamma-herpèsvirus (les herpèsvirus équins 2 et 5). L'herpèsvirus équin 1 est
responsable de trois formes cliniques: une forme respiratoire, une forme abortive et une
forme neurologique. Cette dernière, plus connue sous le nom de myéloencéphalopathie à HVE-1,
a fait l'objet de nombreuses études ces dernières années. La plupart des travaux ont porté
sur la relation entre la présence d'une mutation dans l'ORF 30 codant l'ADN polymérase et
l'expression de la forme paralytique. Si cette mutation semble jouer un rôle, d'autres
facteurs liés à l'hôte et à l'environnement participent certainement au développement de la
maladie. L'herpèsvirus équin 4 est plus connu sous le nom de virus de la rhinopneumonie et
est responsable d'une part importante des affections respiratoires chez les jeunes poulains.
L'herpèsvirus équin 3 est responsable de l'exanthème coïtal équin et l'on sait aujourd'hui
qu'il peut se transmettre par les voies respiratoires. Les herpèsvirus équins 2 et 5 sont
associés aux maladies respiratoires subcliniques du cheval athlète même si leur rôle reste à
préciser, leur découverte sur l'ensemble des continents étant relativement récente. Le
développement des outils de génétique moléculaire a permis de faire des progrès importants
dans la détection de ces virus même si un challenge demeure: différencier les formes
latentes des formes infectieuses. Si comme pour d'autres virus équins (ex: grippe, artérite
virale équine), des travaux sont réalisés pour typer les différentes souches responsables de
différentes formes d'expression de la maladie, il n'existe toujours pas de consensus
international sur un arbre phylogénique pour aucun de ces cinq herpèsvirus équins. Le suivi
et la caractérisation des différentes souches d'HVEs sont très certainement l'autre défi de
demain
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