On the Collaboration of an Automatic Path-Planner and a Human User for Path-Finding in Virtual Industrial Scenes

This paper describes a global interactive framework enabling an automatic path-planner and a user to collaborate for finding a path in cluttered virtual environments. First, a collaborative architecture including the user and the planner is described. Then, for real time purpose, a motion planner divided into different steps is presented. First, a preliminary workspace discretization is done without time limitations at the beginning of the simulation. Then, using these pre-computed data, a second algorithm finds a collision free path in real time. Once the path is found, an haptic artificial guidance on the path is provided to the user. The user can then influence the planner by not following the path and automatically order a new path research. The performances are measured on tests based on assembly simulation in CAD scenes

On a multiscale strategy and its optimization for the simulation of combined delamination and buckling

This paper investigates a computational strategy for studying the interactions between multiple through-the-width delaminations and global or local buckling in composite laminates taking into account possible contact between the delaminated surfaces. In order to achieve an accurate prediction of the quasi-static response, a very refined discretization of the structure is required, leading to the resolution of very large and highly nonlinear numerical problems. In this paper, a nonlinear finite element formulation along with a parallel iterative scheme based on a multiscale domain decomposition are used for the computation of 3D mesoscale models. Previous works by the authors already dealt with the simulation of multiscale delamination assuming small perturbations. This paper presents the formulation used to include geometric nonlinearities into this existing multiscale framework and discusses the adaptations that need to be made to the iterative process in order to ensure the rapid convergence and the scalability of the method in the presence of buckling and delamination. These various adaptations are illustrated by simulations involving large numbers of DOFs

The variational theory of complex rays for the calculation of medium-frequency vibrations

A new approach called the ``variational theory of complex rays’’ (VTCR) is developed for calculating the vibrations of weakly damped elastic structures in the medium-frequency range. Here, the emphasis is put on the most fundamental aspects. The effective quantities (elastic energy, vibration intensity, etc.) are evaluated after solving a small system of equations which does not derive from a finite element discretization of the structure. Numerical examples related to plates show the appeal and the possibilities of the VTCR

Enhanced goal-oriented error assessment and computational strategies in adaptive reduced basis solver for stochastic problems

This work focuses on providing accurate low-cost approximations of stochastic ¿nite elements simulations in the framework of linear elasticity. In a previous work, an adaptive strategy was introduced as an improved Monte-Carlo method for multi-dimensional large stochastic problems. We provide here a complete analysis of the method including a new enhanced goal-oriented error estimator and estimates of CPU (computational processing unit) cost gain. Technical insights of these two topics are presented in details, and numerical examples show the interest of these new developments.Postprint (author's final draft

Vérification et validation de modèles dédiées à des quantités d'intérêt

National audienceNous présentons une démarche générale, basée sur les concepts de problème adjoint et d'erreur en relation de comportement, visant à construire des modèles de simulation optimisés pour la prédiction de quantités d'intérêt. En l'illustrant sur un problème d'élasticité linéaire multi-paramétré, nous montrons comment cette démarche permet le contrôle robuste de toute la chaîne de modélisation, depuis l'expérience jusqu'à la résolution numérique, afin d'assurer que la valeur d'une quantité locale dimensionnante soit calculée avec précision. Dans ce cadre, nous nous focalisons en particulier sur : (i) la vérification des simulations menées par la méthode des éléments finis ; (ii) le contrôle des modèles réduits issus de la technique PGD; (iii) le recalage optimal des paramètres du modèle à partir de mesures expérimentales

Recent advances in the control of PGD-based approximations

International audienceIn this work, we define a verification procedure that enables to build guaranteed PGD-reduced models for linear elliptic or parabolic problems depending on many parameters. It is based on the general concept of constitutive relation error and provides for strict bounds on both global error and error on outputs of interest. Furthermore, it helps driving adaptive strategies by assessing contributions of various error sources. Consequently, virtual charts that may be constructed from the PGD approximate solution can be certified. Technicalities and performances of the control approach, in particular when dealing with a large set of model parameters, are detailed on a transient thermal problem