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Nantes, France
Nantes, France

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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.


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.


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.


Bonnard R.,IRCCyN | Mognol P.,IRCCyN | Hascoet J.-Y.,IRCCyN
Virtual and Physical Prototyping | Year: 2010

Additive manufacturing is, nowadays, a higher process than most traditional processes (machining, etc.). But there still remains a domain where this process is not very competitive: that being its digital chain. Indeed, it is too poor in information to allow for the development of advanced additive manufacturing operations and therefore to compete with the traditional processes. This paper proposes to use the STEP-NC concept, which contains high-level information, in order to integrate the additive manufacturing processes in a complete STEP-NC digital chain in accordance with the norm work group committee ISO TC 184/SC 1. This paper proposes to develop this digital chain with a classical CNC controller, which is also present in machining equipment, and to hence benefit from their development possibilities. online © 2010 Taylor & Francis.


Boyer F.,IRCCyN | Renda F.,Khalifa University
Journal of Nonlinear Science | Year: 2016

In 1901, Henri Poincaré discovered a new set of equations for mechanics. These equations are a generalization of Lagrange’s equations for a system whose configuration space is a Lie group which is not necessarily commutative. Since then, this result has been extensively refined through the Lagrangian reduction theory. In the present contribution, we apply an extended version of these equations to continuous Cosserat media, i.e. media in which the usual point particles are replaced by small rigid bodies, called microstructures. In particular, we will see how the shell balance equations used in nonlinear structural dynamics can be easily deduced from this extension of the Poincaré’s result. In future, these results will be used as foundations for the study of squid locomotion, which is an emerging topic relevant to soft robotics. © 2016 Springer Science+Business Media New York


Kerbrat O.,IRCCyN | Mognol P.,IRCCyN | Hascoet J.-Y.,IRCCyN
Rapid Prototyping Journal | Year: 2010

Purpose - The purpose of this paper is to propose a methodology to estimate manufacturing complexity for both machining and layered manufacturing. The goal is to take into account manufacturing constraints at design stage in order to realize tools (dies and molds) by a combination of a subtractive process (high-speed machining) and an additive process (selective laser sintering). Design/methodology/approach - Manufacturability indexes are defined and calculated from the tool computer-aided design (CAD) model, according to geometric, material and specification information. The indexes are divided into two categories: global and local. For local indexes, a decomposition of the tool CAD model is used, based on an octree decomposition algorithm and a map of manufacturing complexity is obtained. Findings - The manufacturability indexes values provide a well-detailed view of which areas of the tool may advantageously be machined or manufactured by an additive process. Originality/value - Nowadays, layered manufacturing processes are coming to maturity, but there is still no way to compare these new processes with traditional ones (like machining) at the early design stage. In this paper, a new methodology is proposed to combine additive and subtractive processes, for tooling design and manufacturing. A manufacturability analysis is based on an octree decomposition, with calculation of manufacturing complexity indexes from the tool CAD model. © Emerald Group Publishing Limited.


Chablat D.,IRCCyN | Moroz G.,IRCCyN | Wenger P.,IRCCyN
Proceedings - IEEE International Conference on Robotics and Automation | Year: 2011

Parallel robots admit generally several solutions to the direct kinematics problem. The aspects are associated with the maximal singularity free domains without any singular configurations. Inside these regions, some trajectories are possible between two solutions of the direct kinematic problem without meeting any type of singularity: non-singular assembly mode trajectories. An established condition for such trajectories is to have cusp points inside the joint space that must be encircled. This paper presents an approach based on the notion of uniqueness domains to explain this behaviour. © 2011 IEEE.


Amine S.,IRCCyN | Tale Masouleh M.,Laval University | Caro S.,IRCCyN | Wenger P.,IRCCyN | Gosselin C.,Laval University
Mechanism and Machine Theory | Year: 2012

This paper deals with the singular configurations of symmetric 5-DOF parallel mechanisms performing three translational and two independent rotational DOFs. The screw theory approach is adopted in order to obtain the Jacobian matrices. The regularity of these matrices is examined using Grassmann-Cayley algebra and Grassmann geometry. More emphasis is placed on the geometric investigation of singular configurations by means of Grassmann-Cayley algebra for a class of simplified designs whereas Grassmann geometry is used for a matter of comparison. The results provide algebraic expressions for the singularity conditions, in terms of some bracket monomials obtained from the superbracket decomposition. Accordingly, all the singularity conditions can be enumerated. © 2011 Elsevier Ltd.


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.


Kotta U.,Tallinn University of Technology | Moog C.H.,IRCCyN | Tonso M.,Tallinn University of Technology
IFAC Proceedings Volumes (IFAC-PapersOnline) | Year: 2013

The state realization is called minimal if it is either accessible and observable or its state dimension is minimal. In the linear case those two definitions are equivalent, but not for nonlinear time-invariant systems. It is shown that definitions remain equivalent in case one is searching for minimal realization in a larger class of nonlinear time-varying systems. First, nonlinear realization theory is recasted for time-varying nonlinear systems. A necessary and sufficient realizability condition is given in terms of integrability of certain subspace. The mathematical tools used for this purpose are the algebraic approach of differential forms and the theory of the skew polynomial rings; these tools are again extended from time-invariant to time-varying systems. © IFAC.

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