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Defoort M.,Ecole Centrale Lille | Floquet T.,Ecole Centrale Lille | Kokosy A.,ISEN | Perruquetti W.,Ecole Centrale Lille
2007 European Control Conference, ECC 2007 | Year: 2015

This paper presents a decentralized architecture for the navigation of a formation of autonomous mobile robots evolving in an uncertain environment with obstacles. The motion planning scheme consists in decentralized receding horizon controllers that reside on each vehicle to achieve coordination among formation agents. The advantage of the proposed algorithm is that each vehicle only requires local knowledge of its neighboring vehicles. The main requirement for designing a conflict free trajectory that satisfy the coupling constraints, in a decentralized way, is that each robot do not deviate too far from its assumed trajectory designed without taking into account the coupling constraints. Having established an open loop control strategy for motion planning, an effective saturated closed-loop controller based on integral sliding mode for trajectory tracking is presented. Finally, some simulation results demonstrate the effectiveness, real-time and high robustness properties of the proposed architecture. © 2007 EUCA. Source

Rolland S.A.,University of Swansea | Mosbah P.,ISEN | Gethin D.T.,University of Swansea | Lewis R.W.,University of Swansea
Powder Technology | Year: 2012

The powder forming industry looks to produce parts of increasing geometrical complexity as it is seen as a very efficient production process. This offers new challenges as three-dimensional states of stress are induced. In particular, granular and porous materials respond very differently to tensile and compressive stresses. Since experiments conducted in the 1990s, little exploration of the Lode dependency of powders was carried out. The present work investigates the effect of Lode dependency through numerical simulation, aiming to establish whether it affects the outcome of a compaction cycle and whether further experimental study of the phenomenon may be justified. To this effect, a Lode dependent model was developed and implemented in a finite element code, then two case studies were carried out. The results show that there is little impact on the density contours within the components and the stress levels during the compaction. As the parts are ejected from the die, surface stress levels are affected and this is of great interest when studying the onset of defects in powder compacts. © 2011 Elsevier B.V. Source

Launay H.,Lille University of Science and Technology | Parent B.,ISEN | Page A.,University of Strasbourg | Hanoulle X.,Lille University of Science and Technology | Lippens G.,Lille University of Science and Technology
Angewandte Chemie - International Edition | Year: 2013

Kinetics determined by NMR: Whereas most measurements of kinetic parameters of a ligand-protein complex use displacement of the ligand, protein displacement can give accurate off-rates in solution (see picture). Analytical and simulation results are given for the apparent off-rate obtained by protein displacement. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Kaddouri S.,Florida Atlantic University | Beaujean P.-P.J.,Florida Atlantic University | Bouvet P.-J.,ISEN | Real G.,Florida Atlantic University | And 2 more authors.
IEEE Journal of Oceanic Engineering | Year: 2014

Hermes is an asymmetrical point-to-point underwater acoustic modem designed for short-range operations at very high bit rates in ports and shallow waters using broadband acoustic signaling (262-375 kHz). In exploring the possible conversion of Hermes into a multiple-input-multiple-output (MIMO) device, single-carrier phase-modulated spread-spectrum sequences were used for channel estimation and deconvolution purposes. It clearly appeared that the channel estimation and deconvolution routines were quite sensitive to rapid time changes in the acoustic channel impulse response (CIR), which usually reflects the presence of Doppler spread produced for the most part by moving boundaries and oscillating sensors. In this paper, the authors study the least square (LS) channel estimation routine ability to track the time-varying nature of the impulse response using broadband, single-carrier pseudonoise (PN) sequences transmitted by a single source and collected by a single receiver. In addition, the authors evaluate a trend estimation technique, based on the empirical modal decomposition (EMD) method applied to the LS estimate of the CIR. Simulated data produced with a Rayleigh channel model and experimental data collected in a marina are used. This paper shows that the channel estimation method can estimate the time-varying impulse response of the acoustic channel with a high resolution of both time and delay (down to 7 $\mu$s) at the expense of high computational requirements. In analyzing the time variation of the main and secondary echoes for a signal-to-noise ratio (SNR) of 32 dB, simulated results indicate that the root mean square error (RMSE) between theoretical and LS estimated response is 7.8% for the main path with an equivalent Doppler spread of 10 Hz and 15.7% for the second path with an equivalent Doppler spread of 15 Hz. Applying the trend estimation technique to the LS CIR greatly reduces this error, down to 2.9% for the main path and to 4.7% for the second path. The experimental data clearly show that the routine can closely track the time variations of the main echo and provide a meaningful estimate of the Doppler spread. © 2013 IEEE. Source

Vettier B.,French National Center for Scientific Research | Amate L.,ISEN | Garbay C.,French National Center for Scientific Research
Frontiers in Artificial Intelligence and Applications | Year: 2012

In this paper, we propose a normative Multi-Agent System to handle uncertainty in a monitoring application. It is based on the assertion that no single most-likely situation should be considered, thus requiring the management of multiple concurrent hypotheses. A decision is then made by comparing these hypothesized situations to requirements and expectations, thus detecting potential problems. This system uses a large knowledge base of interconnected situation models on several levels of abstraction. It is centered around the need to constantly reconsider which hypotheses should be evaluated, with regards to both the current data from the sensors and wider requirements in terms of efficiency and specific focus from an expected scenario. We propose both a generic concept, and a more specific system for human health monitoring, using ambulatory physiological sensors. © 2012 The Authors and IOS Press. Source

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