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Nantes, France

Briat C.,KTH Royal Institute of Technology | Sename O.,CNRS GIPSA Laboratory | Lafay J.-F.,IRCCyN
International Journal of Control | Year: 2011

The design of reduced order observer for linear parameter varying (LPV) time-delay systems is addressed. Necessary conditions guaranteeing critical structural properties for the observation error dynamics are first provided through nonlinear algebraic matrix equalities. An explicit parametrisation of the family of observers fulfilling these necessary conditions is then derived. Finally, an approach based on linear matrix inequalities is provided and used to select a suitable observer within this family, according to some criterion; e.g. maximisation of the delay margin or guaranteed suboptimal ℒ2-gain. Examples from the literature illustrate the efficiency of the approach. © 2011 Taylor & Francis. Source


Delfieu D.,IRCCyN | Sogbohossou M.,University Abomey Calavi
2013 International Conference on Control, Decision and Information Technologies, CoDIT 2013 | Year: 2013

The unfolding process of Petri Nets produces a set of causal nets where nodes are conditions or events and arcs express relations of causality, conflict or concurrency called branching processes. We propose in this paper an algebra and reduction rules allowing to extract informations, relation on events and a canonic representation of branching processes. © 2013 IEEE. Source


Balesdent M.,French National Center for Space Studies | Berend N.,ONERA | Depince P.,IRCCyN
Journal of Spacecraft and Rockets | Year: 2012

Optimal design of launch vehicles is a complex process that gathers a series of disciplines. The classical method used to solve such problems consists in decomposing the problem into the different disciplines and in associating a global optimizer and disciplinary analyzers (multidiscipline feasible method, most used in launch vehicle design). This paper presents a new multidisciplinary design optimization method based on a transverse decomposition of the design process adapted to the multistage launch vehicle architecture. The proposed bilevel method splits up the optimization process into different flight phases and performs the different stage optimizations either sequentially or concurrently. Thus, the proposed approach transforms the global multidisciplinary design optimization problem into the coordination of elementary multidisciplinary design optimization problems and moves the problem complexity from the system level to the subsystem level. Three formulations of this method are proposed and compared with the multidiscipline feasible method on a multistage launch vehicle design problem. The proposed method allows the dimension of the search domain and the number of constraints at the system level to be reduced. In that way, this approach makes the use of heuristic methods such as the genetic algorithms more efficient in solving the large-scale highly nonlinear launch vehicle design problem. Copyright © 2012 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. Source


Gautier M.,CNRS Research Institute of Communication and Cybernetics of Nantes | Janot A.,ONERA | Jubien A.,IRCCyN | Vandanjon P.O.,IFSTTAR
Proceedings of the IEEE Conference on Decision and Control | Year: 2011

This paper deals with joint stiffness identification with only actual motor force/torque data instead of motor and load positions. The parameters are estimated by using the DIDIM method which needs only input data. This method was previously validated on a 6 DOF rigid robot and is now extended to flexible systems. The criterion to be minimized is the quadratic error between the measured actual motor force/torque and the simulated one. The optimal parameters are calculated with the Nelder - Mead simplex algorithm. An experimental setup exhibits the experimental identification results and shows the effectiveness of our approach. © 2011 IEEE. Source


Le Meur O.,University of Rennes 1 | Ninassi A.,Technicolor R and D | Le Callet P.,IRCCyN | Barba D.,IRCCyN
Signal Processing: Image Communication | Year: 2010

The aim of this study is to understand how people watch a video sequence during free-viewing and quality assessment tasks. To this end, two eye tracking experiments were carried out. The video dataset is composed of 10 original video sequences and 50 impaired video sequences (five levels of impairments obtained by a H.264 video compression). A first experiment consisted in recording eye movements in a free-viewing task. The 10 original video sequences were used. The second experiment concerned an eye tracking experiment in a context of a subjective quality assessment. Eye movements were recorded while observers judged on the quality of the 50 impaired video sequences. The comparison between gaze allocations indicates the quality task has a moderate impact on the visual attention deployment. This impact increases with the presentation number of impaired video sequences. The locations of regions of interest remain highly similar after several presentations of the same video sequence, suggesting that eye movements are still driven by the low level visual features after several viewings. In addition, the level of distortion does not significantly alter the oculomotor behavior. Finally, we modified the pooling of an objective full-reference video quality metric by adjusting the weight applied on the distortions. This adjustment depends on the visual importance (the visual importance is deduced from the eye tracking experiment realized on the impaired video sequences). We observe that a saliency-based distortion pooling does not significantly improve the performances of the video quality metric. © 2010 Elsevier B.V. Source

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