Implementation of an Internet-based remote controller with guaranteed exponential stabilization

International audienceAn Internet-based remote control system is designed and implemented. The communication is based on the Master-Slave structure. The Master PC communicates with the Slave from about 40km away by UDP protocol. In order to guarantee the Master and Slave clocks to be synchronized, the NTP (Network Time Protocol) is used in both sides. The packets are sent together with time-stamps. The controller design (Master) relies on a remote observer that achieves a state prediction of the application (Slave), despite the variable communication delays. The Slave comprises a PC and a robot Miabot of Merlin company. Internet-based remote systems are subject to variable time delays (including communication and data-sampling delays). We have continuously tested the RTT (round-triptime) between the two PCs in the day-time and night-time by the protocol ICMP (Internet Control Message). From these tests, an evaluation of the maximal time delay is obtained. The structure allows one to guarantee an exponential stabilization performance, which is proven via a Lyapunov-Krassovski functional technique and involves the estimated delay upperbound. This means that the guaranteed decay rate is computed (via some LMI optimization) in relation to some maximal value of the communication delays. Of course, for greater delay values, the performance cannot be guaranteed anymore and an alternative solution has to be considered. In our system, we give a command for the robot to stop until the communication comes back to a sufficient quality

Networked control and observation for Master-Slave systems

2009, 350 p. 110 illus., Hardcover. ISBN: 978-0-387-85594-3This chapter concerns the design of a remote control loop constituted by a Slave system (with computing and energy limitations) and a Master computer, communicating via an Internet connection. In such a situation, the communication cost is reduced but the Quality of Service of the Internet connection is not guaranteed. In particular, when the Slave dynamics are expected to be fast enough, the network induces perturbations (delays, jitters, packet dropouts and sampling) that may damage the performance. Here, the proposed solution relies on a delay-dependent, state-feedback control, computed by the Master on the basis of an observer. This last estimates the present Slave's state from its past sampled outputs, despite the various delays. Then, the computing task is concentrated in the Master. The theoretical results are based on the Lyapunov-Krasovskii functional and the approach of LMI, which guarantee the stabilization performance with respect to the expected maximum delay of the connection. Two strategies are applied: one is a constant controller/observer gain strategy, which takes into account a fixed upperbound for the communication delay. The second strategy aims at improving the performance by adapting the gains to the available network QoS (here, with two possible upperbounds)

A gain scheduling strategy for the control and estimation of a remote robot via Internet

International audienceA gain scheduling strategy for the controller of a remote robot based on Internet and Bluetooth networks is designed and implemented. The Internet communication is based on the Master-Slave structure, UDP protocol. The Slave comprises a PC and a mobile robot, interconnected through the protocol Bluetooth. The Master is a second PC which realizes the remote control, the design of which is based on a remote observer achieving a state prediction of the robot (Slave), despite the variable communication delays, sampling and packets losses. The detected variable time delays serve as the switching signals. The gain scheduling state feedback controller is based on Lyapunov-Krasovskii functional and the approach of LMI, which guarantee the uniform stabilization performance

Output control with Internet-in-the-loop : An event-driven realization

International audienceThis work is devoted to the remote feedback control of a linear process with "Internet in the loop". In such a networked control situation, variable and unpredictable delays arise, which may decrease the global performance or destabilize the system. Our aim is to obtain the best performance despite the variation of the network QoS (quality of service). The considered application is based on a Master-Slave structure. The Slave is a light mobile robot, that receives the control data and sends its sampled position via a UDP protocol. A Master computer realizes the remote control, based on a remote observer and a state feedback. The global strategy is without buffers. The packets are time-stamped so the Master detects the variable time delays (the network QoS). This information is used to adapt its observer/controller gains and guarantee the best possible performances. The design of this gain scheduling strategy relies on Lyapunov-Krasovskii functionals with an LMI optimization which guarantees the stability even with packet losses. Experimental results are provided

Tautologies toponymiques : comment apprivoiser l’espace entre continuités et fractures

On ne peut réduire les tautologies – dénominations dont la forme condense deux expressions transmettant un seul et même concept – en toponymie à une simple question étymologique. Elles posent, au-delà de la nécessité de la motivation toujours renouvelée des désignations toponymiques, le problème des contacts entre populations et traduisent la façon dont ces contacts ont pu s’établir. A partir d’une réalité géomorphologique commune, soit la combinaison d’espace géophysique et anthropisé, langues et cultures différentes peuvent réaliser des partitions sémantiques visant à apprivoiser l’espace extralinguistique. L’étude des tautologies, s’inscrivant dans une succession historique liée à l’occupation des lieux, représente un outil permettant de repérer et formuler les enjeux de continuité et fracture qui se jouent dans nos sociétés contemporaines.Toponymic tautologies – denominations whose form condenses two expressions conveying one and the same concept – cannot be reduced to a simple etymological question. Beyond the need for an ever-renewed motivation for toponymic designations, they address the problem of contacts between populations and reflect the way these contacts have been established. From a shared geomorphological reality, i.e. the combination of geophysical and anthropized spaces, different languages and cultures can produce semantic partitions that aim to tame extra-linguistic space. The study of tautologies, which are part of a historical succession linked to the occupation of the places, represent a useful tool for identifying and formulating the issues of continuity and fracture that are at stake in our contemporary societies

Plant functional trait effects on runoff to design herbaceous hedges for soil erosion control

International audienceVegetation controls concentrated runoff and erosion in the European loess belt by increasing hydraulic roughness and sediment retention. Studies of plant effects on runoff velocity are usually based on a taxonomical characterisation and do not consider the effects of aboveground plant functional traits in attempts to understand soil erosion by water. This trait-based plant study investigates aboveground plant functional trait effects of herbaceous hedges on the hydraulic roughness to understand soil erosion. Eight aboveground morphological traits were measured on fourteen indigenous and perennial plant species (caespitose or comprising dry biomass in winter) from north-west Europe with a high morphological variability. For each trait, density-weighted traits were calculated. The effects of traits and density-weighted traits were examined using a runoff simulator with four discharges. The leaf density and area, as well as density-weighted stem and leaf areas, stem diameter and specific leaf area were positively correlated with the hydraulic roughness. Generalised linear models defined the best combinations of traits and density-weighted traits: (1) leaf density and leaf area, (2) density-weighted leaf area and density-weighted projected stem area, and (3) density-weighted leaf area and density-weighted stem diameter. Moreover, the effects of leaf density, leaf area and density-weighted specific leaf area, varied depending on the discharge. This study is one of the first characterisation of aboveground trait effects on hydraulic roughness and highlights that vegetation with large stem density, diameter and leaf area plays a significant role in minimising soil erosion. The selection of plant species can derive from these plant trait effects to design reconstructed herbaceous hedges to minimise soil erosion

Implementation of an Internet-controlled system under variable delays

International audienceThis work deals with the control and the observation of a remote system using Internet as a communication line. The process consists in a Slave part S, with poor computing capacity, connected to a Master M through the Internet. The internal times of both M and S are synchronized thanks to a common GPS clock. The global system must ensure some speed performance whatever the delay variations. The main technical restriction is that the delays are less than some known bound, even if the framework we consider takes into account the perturbations generated by the Internet communication delays, by the packet losses and by the sampling phenomenon as well. In what concerns the design of the observer and controller, most of the theorems to be used here refer to proofs given in [14], and this will allow for focussing on the implementation aspects

Variability of major fatty acid contents in Luxembourg dairy cattle

Common human health concerns and imminent needs for more sustainable nutrition patterns require from dairy industry and farmers a. o. a closer look at milk fatty acid (FA) profile. Therefore up to date calibration equations using mid-infrared (MIR) spectrometry were developed permitting the estimation of FA contents in bovine milk. The aim of this study was to estimate the variability of the major FA from data collected during the Luxembourg routine milk recording. A total of 148,296 milk samples with MIR-spectra were collected from October 2007 to January 2009 on 36,522 cows belonging to 5 breeds in 718 herds and scanned by Foss MilkoScan FT6000. The contents of saturated FA, monounsaturated FA, omega-9, short chain FA, medium chain FA, and long chain FA were obtained using Belgian MIR calibration equations. Analyzes were done by a multi-trait multi-lactation animal mixed models. Fixed effects were herd*test date, lactation stage lactation number, age*lactation number, and breed effect. Random effects were herd*year of calving, permanent environment within and across lactation, animal effect, and residual effect. Breed differences as well as lactation effects were observed. Our results showed moderate heritability values suggesting the existence of a FA genetic variability. The variability of the first Luxembourg breeding values was large enough to develop selection tools for improving the nutritional quality of bovine milk fat.Peer reviewe

L'environnement : une priorité pour l'agriculture : traiter et recycler les déchets

L'Institut de Recherche pour le Développement (IRD) a pour objectif la conduite de recherches avec des partenaires scientifiques des pays du Sud sur des thèmes importants pour le développement de ces pays. Depuis une quinzaine d'années, la dépollution et la valorisation des déchets agricoles et agro-industriels constituent l'un des trois principaux thèmes de recherche des microbiologistes regroupant leurs activités au sein d'un Programme de l'IRD intitulé "Utilisation de la biodiversité microbienne pour la valorisation des ressources tropicales". Ces recherches sont orientées d'une part vers les activités microbiennes anaérobies et la méthanisation, et d'autre part vers les processus microbiens dits de "fermentation en milieu solide" (FMS) impliquant principalement des champignons et des groupes bactériens tels que les bactéries lactiques. Ces deux orientations conditionnent le classement en trois grands groupes des résidus agricoles et agro-industriels pouvant constituer une source de pollution importante dans les pays du Sud et du Nord. Différents exemples de projets de recherche achevés ou en cours sont résumés en indiquant pour chacun d'eux (1) la nature du problème, (2) l'approche microbiologique du problème et (3) l'état de la valorisation pratique de ces résultats. Les recherches à l'IRD sur la méthanisation de sous-produits agricoles et agro-industriels tropicaux ont initialement été orientées vers la biodépollution. Les premiers travaux ont utilisé des consortiums microbiens non définis provenant de différents écosystèmes et adaptés aux produits à dépolluer. Ce n'est que récemment qu'un inoculum caractérisé a été utilisé avec succès. Ces travaux ont débouché soit sur la valorisation en milieu industriel, soit sur des essais en cours à l'échelle pilote... (D'après le résumé d'auteur