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See detailThe generalized-alpha method in mechatronic applications
Bruls, Olivier ULg; Golinval, Jean-Claude ULg

in ZAMM-Zeitschrift fur Angewandte Mathematik und Mechanik (2006), 86(10 Sp. Iss. SI), 748-758

This paper presents an extension of the generalized-a time-integrator to mechatronic systems represented by coupled first and second-order DAEs. A simple reformulation of those equations as full second ... [more ▼]

This paper presents an extension of the generalized-a time-integrator to mechatronic systems represented by coupled first and second-order DAEs. A simple reformulation of those equations as full second-order DAEs allows the implementation of a monolithic integration scheme, so that the numerical dissipation properties are preserved, and second-order accuracy is obtained at least in the unconstrained case. The algorithmic parameters can be optimized either for the mechanical or the control subsystem. Two illustrative applications are treated in the fields of vehicle dynamics and robotics. [less ▲]

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See detailThe generalized-alpha scheme as a linear multistep integrator: Toward a general mechatronic simulator
Bruls, Olivier ULg; Arnold, Martin

in Journal Of Computational And Nonlinear Dynamics (2008), 3(4), 041007

This paper presents a consistent formulation of the generalized-alpha time integration scheme for mechanical and mechatronic systems. The algorithm can deal with a nonconstant mass matrix, controller ... [more ▼]

This paper presents a consistent formulation of the generalized-alpha time integration scheme for mechanical and mechatronic systems. The algorithm can deal with a nonconstant mass matrix, controller dynamics; and kinematic constraints. The theoretical background relies on the analogy with linear multistep formulas, which leads to elegant results related to consistency, order conditions for constant and variable step-size methods, as well as global convergence. Those results are illustrated for a controlled spring-mass system, and the method is also applied for the simulation of a vehicle semi-active suspension. [less ▲]

Detailed reference viewed: 165 (5 ULg)
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See detailThe generalized-alpha scheme as a linear multistep integrator: Towards a general mechatronic simulator
Bruls, Olivier ULg; Arnold, Martin

in Proceedings of the ASME 2007 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference (2007)

This paper presents a consistent formulation of the generalized-alpha time integration scheme for mechanical and mechatronic systems. The algorithm can deal with a nonconstant mass matrix, controller ... [more ▼]

This paper presents a consistent formulation of the generalized-alpha time integration scheme for mechanical and mechatronic systems. The algorithm can deal with a nonconstant mass matrix, controller dynamics, and kinematic constraints. The theoretical background relies on the analogy with linear multistep formulae, which leads to elegant results related with consistency, order conditions for constant and variable stepsize methods, as well as global convergence. The algorithm is applied for the simulation of a vehicle semi-active suspension. [less ▲]

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See detailThe generalized-alpha time-integration scheme for mechatronic systems with elastic components
Bruls, Olivier ULg

Conference (2006, May)

This talk concerns the numerical simulation of mechatronic systems, such as robots, machine-tools or modern vehicles. In general, a mechatronic system is composed of various technological components: a ... [more ▼]

This talk concerns the numerical simulation of mechatronic systems, such as robots, machine-tools or modern vehicles. In general, a mechatronic system is composed of various technological components: a mechanism, actuators, sensors, and control units. For critical applications, it is also necessary to account for elastic deformations in the mechanism. The generalized-alpha method has been initially developed for the dynamic simulation of flexible mechanical structures, which are represented by lightly damped second-order ODEs. Usually, those equations are obtained after a finite element spatial discretization, with the consequence that they are affected by a large number of high-frequency modes with a purely numerical origin. The generalized-alpha method has very interesting properties in this context, such as an adjustable amount of high-frequency numerical dissipation, A-stability, second-order accuracy, and a high level of computational efficiency. A mechanism with elastic components can be described using the nonlinear finite element formalism. Due to the presence of kinematic constraints, the equations of motion are second-order DAEs, and we shall consider the generalized-alpha method for the direct simulation of the index-3 problem. In particular, some results about the convergence and the stability of the algorithm will be discussed. Finally, a mechatronic system involves mechanical and non-mechanical components, and it is thus modelled as a mixed set of second- and first-order DAEs. We will show that those coupled equations of motion can also be solved in the time domain according to the generalized-alpha scheme. An important problem is then associated with the selection of the parameters of the method. The presentation will be illustrated by academic and non-academic applications, for example in vehicle dynamics and in robotics. [less ▲]

Detailed reference viewed: 200 (6 ULg)
Peer Reviewed
See detailGeneralizing Grasps Across Partly Similar Objects
Detry, Renaud ULg; Ek, Carl Henrik; Madry, Marianna et al

in IEEE International Conference on Robotics and Automation (2012)

Detailed reference viewed: 26 (1 ULg)
Peer Reviewed
See detailGeneralizing Task Parameters Through Modularization
Detry, Renaud ULg; Hjelm, Martin; Ek, Carl Henrik et al

Conference (2013)

Detailed reference viewed: 12 (2 ULg)
See detailGenerating Dicke states with photodetector arrays in trapped ions
Thiel, C.; von Zanthier, J.; Bastin, Thierry ULg et al

Poster (2006)

Detailed reference viewed: 1 (0 ULg)
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See detailGenerating evidence of governance contribution to health outcomes
Porignon, Denis ULg

Conference (2014, July 23)

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See detailGenerating informative trajectories by using bounds on the return of control policies
Fonteneau, Raphaël ULg; Murphy, Susan; Wehenkel, Louis ULg et al

in Proceedings of the Workshop on Active Learning and Experimental Design 2010 (in conjunction with AISTATS 2010) (2010, May)

We propose new methods for guiding the generation of informative trajectories when solving discrete-time optimal control problems. These methods exploit recently published results that provide ways for ... [more ▼]

We propose new methods for guiding the generation of informative trajectories when solving discrete-time optimal control problems. These methods exploit recently published results that provide ways for computing bounds on the return of control policies from a set of trajectories. [less ▲]

Detailed reference viewed: 37 (12 ULg)
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See detailGenerating random percolation clusters.
Bogaert, Jan ULg; Impens, I

in Applied Mathematics and Computation (1998), 91(2-3), 197-208

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See detailGenerating smooth surface meshes from labelled medical datasets
D'Otreppe, Vinciane ULg; Boman, Romain ULg; Ponthot, Jean-Philippe ULg

in Nithiarasu, Perumal; Löhner, Rainald; van Loon, Raoul (Eds.) et al CMBE11: 2nd International Conference on Computational & Mathematical Biomedical Engineering, 30 March - 1 April, 2011, Washington D.C. U.S.A. (2011, March 30)

In this article, an innovative procedure to create high quality triangular meshes from medical scans is proposed. The approach is based on an enhanced Marching Tetrahedra algorithm that extracts a ... [more ▼]

In this article, an innovative procedure to create high quality triangular meshes from medical scans is proposed. The approach is based on an enhanced Marching Tetrahedra algorithm that extracts a consistent multiple region surface mesh from a labelled volume data set; coupled with a surface reconstruction method to avoid typical staircase artifacts. Mesh smoothing and decimation algorithms are also revised to conform to the multiple material nature of the system as well as to adhere to the underlying volume data. The proposed method is well suited for subsequent volume mesh generation and finite element simulations. [less ▲]

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See detailGenerating smooth surface meshes from multi-region medical images
D'Otreppe, Vinciane ULg; Boman, Romain ULg; Ponthot, Jean-Philippe ULg

in International Journal for Numerical Methods in Biomedical Engineering (2012), 28(6-7), 642-660

Thanks to advances in medical imaging technologies and numerical methods, Patient-Specific Modelling is more and more used to improve diagnosis and to estimate the outcome of surgical interventions. It ... [more ▼]

Thanks to advances in medical imaging technologies and numerical methods, Patient-Specific Modelling is more and more used to improve diagnosis and to estimate the outcome of surgical interventions. It requires the extraction of the domain of interest from the medical scans of the patient, as well as the discretisation of this geometry. However, extracting smooth multi-material meshes that conform to the tissue boundaries described in the segmented image is still an active field of research. We propose to solve this issue by combining an implicit surface reconstruction method with a multi-region mesh extraction scheme. The surface reconstruction algorithm is based on multi-level partition of unity implicit surfaces which we extended to the multi-material case. The mesh generation algorithm consists in a novel multidomain version of the marching tetrahedra. It generates multi-region meshes as a set of triangular surface patches consistently joining each other at material junctions. This paper presents this original meshing strategy, starting from boundary points extraction from the segmented data, to heterogeneous implicit surface definition, multi-region surface triangulation and mesh adaptation. Results indicate that the proposed approach produces smooth and high-quality triangular meshes with a reasonable geometric accuracy. Hence, the proposed method is well suited for subsequent volume mesh generation and Finite Element simulations. [less ▲]

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See detailGenerating strong magnetic flux shielding regions in a single crystal of Bi 2 Sr 2 CaCu 2 O 8 using a blind hole array
Shaw, Gorky ULg; Bag, B.; Banerjee, S. S. et al

in Superconductor Science and Technology (2012), 25(9), 095016

Detailed reference viewed: 14 (3 ULg)
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See detailGeneration and Evaluation of New Product Ideas: Current Methods and Future Prospects
Choffray, Jean-Marie ULg; Galper, Morton

E-print/Working paper (1984)

In this paper, we review the current state of practise in the field of new product idea generation and evaluation. We introduce a new micro-computer based methodology aimed at managing creative sessions.

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See detailGénération automatique d'un modèle de bâtiment à partir d'un croquis
Demaret, Jean-Noël ULg; Leclercq, Pierre ULg

in Complexité(s) des modèles de l'architecture numérique : Actes du 5ème séminaire de Conception Architecturale Numérique (SCAN'12) (2012)

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See detailGénération automatique d'une base de données de silhouettes humaines au moyen d'un avatar humain tridimensionnel
Pierard, Sébastien ULg

Master's dissertation (2007)

Pour la conception de systèmes de vidéo-surveillance, il est avantageux d’avoir un système de détection automatique d’êtres humains. Certains de ces systèmes sont basés sur la reconnaissance de la forme ... [more ▼]

Pour la conception de systèmes de vidéo-surveillance, il est avantageux d’avoir un système de détection automatique d’êtres humains. Certains de ces systèmes sont basés sur la reconnaissance de la forme de silhouettes humaines. L’utilisation de méthodes d'apprentissage pour la reconnaissance nécessite une base de données de silhouettes humaines, dont il est intéressant d’automatiser la génération. Dans ce travail, nous utilisons un avatar humain tridimensionnel, celui du projet open-source MakeHuman, afin de générer automatiquement la base de données. Le choix des configurations (positions, orientations et poses) à donner à l’avatar pour obtenir une base de données adéquate est central. Dans un premier temps, nous tentons une étude de l’impact de modifications dans le mode tridimensionnel sur la silhouette. Cet impact est quantifié par la distance de Hausdorff. Parmi les modifications envisagées se trouvent le déplacement, la rotation et le changement de pose de l’avatar. Nous espérions déterminer, à partir de ces impacts, les pas par lesquels doivent varier les différents paramètres. Les configurations que doit prendre l’avatar, pour obtenir une base de données suffisamment riche sans être trop volumineuse, seront obtenues en prenant toutes les combinaisons des valeurs des différents paramètres. Le nombre de configurations est exponentiel en le nombre de degrés de liberté, ce qui rend l’approche inutilisable en pratique, même si nous sommes indifférents à la translation et à la mise à l’échelle des silhouettes. Dans un deuxième temps, nous avons opté pour une approche radicalement différente. Cette fois, nous n’espaçons plus les silhouettes, mais les poses. La position de l’avatar est fixée et il ne peut tourner qu’autour de l’axe vertical. Les poses sont choisies en effectuant des tirages aléatoires des différents paramètres. Cette approche aléatoire du problème a mené à l’élaboration d’un nouveau logiciel, Silhouette. Il est écrit en Java et une interface écrite en C lui permet, grâce à Java Native Interface d’exploiter efficacement le moteur de pose de MakeHuman. Parmi les fonctionnalités de Silhouette, notons la possibilité de restreindre les poses à un ensemble voulu, de ne générer que des silhouettes correspondant à des poses licites et d’annoter les silhouettes. Grâce au logiciel mis en place, nous avons été en mesure de générer diverses bases de données. Nous avons étudié l'impact de l'utilisation de celles-ci sur les performances d'un système de détection de personnes existant. Nous obtenons des résultats encourageants, 73% des silhouettes humaines étant correctement détectées. Un raffinement et un paramétrage soigneux de la méthode devraient mener à des résultats excellents. [less ▲]

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See detailGénération d'un maillage pour éléments finis à partir de fichiers de stéréolithographie – Une interface indépendante des formats CAO
Béchet, Eric ULg; Cuillière, Jean-Christophe; Trochu, François

in Maranzana, Roland (Ed.) De la CAO géométrique vers une CAO fonctionnelle: special cfao au quebec (2003)

Detailed reference viewed: 11 (1 ULg)
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See detailGénération d'un maillage pour éléments finis à partir de fichiers stéréolithographie (STL) : une interface indépendante des formats de CAO
Béchet, Eric ULg; Cuillière, Jean-Christophe; Trochu, François

in Revue internationale de CFAO et d'informatique graphique (2002), 17/1-2

The aim of the method proposed here is to show the possibility of generating adaptive surface meshes suitable for the finite element method, directly from an approximated boundary representation of an ... [more ▼]

The aim of the method proposed here is to show the possibility of generating adaptive surface meshes suitable for the finite element method, directly from an approximated boundary representation of an object created with CAD software. First, we describe the boundary representation, then we will show how to obtain a conforming sizeadapted mesh. The size adaptation is made considering geometrical approximation and with respect to an isotropic size map provided by an error estimator. The principle used to generate the mesh is based on the Delaunay method. Finally, we will show that not using the parametric representation of the geometrical model allows us to override some of the limitations of conventional meshing software that is based on an exact representation of the geometry. [less ▲]

Detailed reference viewed: 168 (23 ULg)
See detailGénération de maillages anisotropes à partir de fichiers stéréolithographie
Béchet, Eric ULg; Cuillière, Jean-Christophe; Trochu, François

Conference (2001)

Detailed reference viewed: 18 (3 ULg)