Discretisation techniques for large deformation computational contact elastodynamics

The present thesis deals with large deformation contact problems of flexible bodies in the field of nonlinear elastodynamics. Special emphasis will be placed on a consistent spatial and temporal discretization. For the spatial discretization of the underlying bodies, the finite element method will be used. For the contact boundaries the collocation type node-to-surface method as well as the variationally consistent Mortar method will be applied

Simulation of conforming contact in real-time multibody dynamics using a volumetric force model

Programa Oficial de Doutoramento en Enxeñaría Naval e Industrial . 5015V01[Abstract] Simulation is a tool on the rise, especially in the industrial field. The usage of simulators grants the ability of studying, predicting and improving the behavior of a system, as well as designing a new one. In the case of mechanical processes simulators, the characterization of contacts and collisions between the different elements at play is one of the key factors to achieve a realistic simulation. If, furthermore, the simulator is designed to interact with machines or people, the need of real-time execution is imposed. Usually, these requirements produce a conflict of interest, since more complex algorithms demand larger execution times. Furthermore, all this is worsened by some application’s need of conforming contact simulation, this is, complex contacts where the size of the contact footprint is not negligible compared to the size of the bodies in collision. This work studies two methods suitable for conforming contact simulation and their possibilities to be used in real-time simulators are discussed.[Resumo] A simulación é unha ferramenta en auxe, especialmente no ámbito industrial. O emprego de simuladores otorga a capacidade de estudar, predecir e mellora-lo comportamento dun sistema, así como de deseñar un novo. No caso dos simuladores de procesos mecánicos, a caracterización do contacto e das colisións entre os diferentes elementos en xogo é un dos factores clave para conseguir unha simulación fidedigna. Se, ademáis, ésta está deseñada para interactuar con máquinas ou persoas, imponse a necesidade de que a execución da simulación sexa en tempo real. Xeralmente, estos requerimentos producen un conflicto de intereses, xa que algoritmos máis complexos esixen tempos de execución máis amplos. Ademáis, todo isto vese perxudicado pola necesidade dalgunhas aplicacións de simular contactos conformes, isto é, contactos complexos nos que o tamaño da pegada de contacto non é desprezable en comparación ó tamaño dos corpos en colisión. Neste traballo estúdianse dous métodos adecuados para simular contactos conformes e debátense as súas posibilidades para ser aplicados en simuladores en tempo real.[Resumen] La simulación es una herramienta en auge, especialmente en el ámbito industrial. El empleo de simuladores otorga la capacidad de estudiar, predecir y mejorar el comportamiento de un sistema, así como de diseñar uno nuevo. En el caso de los simuladores de procesos mecánicos, la caracterización del contacto y las colisiones entre los diferentes elementos en juego es uno de los factores clave para conseguir una simulación fidedigna. Si, además, ésta está diseñada para interactuar con máquinas o personas, se impone la necesidad de que la ejecución de la simulación sea en tiempo real. Generalmente, estos requerimientos producen un conflicto de intereses, ya que algoritmos más complejos exigen tiempos de ejecución más amplios. Además, todo esto se ve perjudicado por la necesidad de algunas aplicaciones de simular contactos conformes, esto es, contactos complejos en los que el tamaño de la huella de contacto no es despreciable en comparación al tamaño de los cuerpos en colisión. En este trabajo se estudian dos métodos adecuados para simular contactos conformes y se debaten sus posibilidades para ser aplicados en simuladores en tiempo real

Proceedings of the ECCOMAS Thematic Conference on Multibody Dynamics 2015

This volume contains the full papers accepted for presentation at the ECCOMAS Thematic Conference on Multibody Dynamics 2015 held in the Barcelona School of Industrial Engineering, Universitat Politècnica de Catalunya, on June 29 - July 2, 2015. The ECCOMAS Thematic Conference on Multibody Dynamics is an international meeting held once every two years in a European country. Continuing the very successful series of past conferences that have been organized in Lisbon (2003), Madrid (2005), Milan (2007), Warsaw (2009), Brussels (2011) and Zagreb (2013); this edition will once again serve as a meeting point for the international researchers, scientists and experts from academia, research laboratories and industry working in the area of multibody dynamics. Applications are related to many fields of contemporary engineering, such as vehicle and railway systems, aeronautical and space vehicles, robotic manipulators, mechatronic and autonomous systems, smart structures, biomechanical systems and nanotechnologies. The topics of the conference include, but are not restricted to: ● Formulations and Numerical Methods ● Efficient Methods and Real-Time Applications ● Flexible Multibody Dynamics ● Contact Dynamics and Constraints ● Multiphysics and Coupled Problems ● Control and Optimization ● Software Development and Computer Technology ● Aerospace and Maritime Applications ● Biomechanics ● Railroad Vehicle Dynamics ● Road Vehicle Dynamics ● Robotics ● Benchmark ProblemsPostprint (published version

Multiscale Coarse-Graining of the Protein Energy Landscape

A variety of coarse-grained (CG) models exists for simulation of proteins. An outstanding problem is the construction of a CG model with physically accurate conformational energetics rivaling all-atom force fields. In the present work, atomistic simulations of peptide folding and aggregation equilibria are force-matched using multiscale coarse-graining to develop and test a CG interaction potential of general utility for the simulation of proteins of arbitrary sequence. The reduced representation relies on multiple interaction sites to maintain the anisotropic packing and polarity of individual sidechains. CG energy landscapes computed from replica exchange simulations of the folding of Trpzip, Trp-cage and adenylate kinase resemble those of other reduced representations; non-native structures are observed with energies similar to those of the native state. The artifactual stabilization of misfolded states implies that non-native interactions play a deciding role in deviations from ideal funnel-like cooperative folding. The role of surface tension, backbone hydrogen bonding and the smooth pairwise CG landscape is discussed. Ab initio folding aside, the improved treatment of sidechain rotamers results in stability of the native state in constant temperature simulations of Trpzip, Trp-cage, and the open to closed conformational transition of adenylate kinase, illustrating the potential value of the CG force field for simulating protein complexes and transitions between well-defined structural states

Multibody dynamics 2015

This volume contains the full papers accepted for presentation at the ECCOMAS Thematic Conference on Multibody Dynamics 2015 held in the Barcelona School of Industrial Engineering, Universitat Politècnica de Catalunya, on June 29 - July 2, 2015. The ECCOMAS Thematic Conference on Multibody Dynamics is an international meeting held once every two years in a European country. Continuing the very successful series of past conferences that have been organized in Lisbon (2003), Madrid (2005), Milan (2007), Warsaw (2009), Brussels (2011) and Zagreb (2013); this edition will once again serve as a meeting point for the international researchers, scientists and experts from academia, research laboratories and industry working in the area of multibody dynamics. Applications are related to many fields of contemporary engineering, such as vehicle and railway systems, aeronautical and space vehicles, robotic manipulators, mechatronic and autonomous systems, smart structures, biomechanical systems and nanotechnologies. The topics of the conference include, but are not restricted to: Formulations and Numerical Methods, Efficient Methods and Real-Time Applications, Flexible Multibody Dynamics, Contact Dynamics and Constraints, Multiphysics and Coupled Problems, Control and Optimization, Software Development and Computer Technology, Aerospace and Maritime Applications, Biomechanics, Railroad Vehicle Dynamics, Road Vehicle Dynamics, Robotics, Benchmark Problems. The conference is organized by the Department of Mechanical Engineering of the Universitat Politècnica de Catalunya (UPC) in Barcelona. The organizers would like to thank the authors for submitting their contributions, the keynote lecturers for accepting the invitation and for the quality of their talks, the awards and scientific committees for their support to the organization of the conference, and finally the topic organizers for reviewing all extended abstracts and selecting the awards nominees.Postprint (published version

Modeling of ground excavation with the particle finite element method

The present work introduces a new application of the Particle Finite Element Method (PFEM) for the modeling of excavation problems. PFEM is presented as a very suitable tool for the treatment of excavation problem. The method gives solution for the analysis of all processes that derive from it. The method has a high versatility and a reasonable computational cost. The obtained results are really promising.Postprint (published version

Advanced human inspired walking strategies for humanoid robots

Cette thèse traite du problème de la locomotion des robots humanoïdes dans le contexte du projet européen KoroiBot. En s'inspirant de l'être humain, l'objectif de ce projet est l'amélioration des capacités des robots humanoïdes à se mouvoir de façon dynamique et polyvalente. Le coeur de l'approche scientifique repose sur l'utilisation du controle optimal, à la fois pour l'identification des couts optimisés par l'être humain et pour leur mise en oeuvre sur les robots des partenaires roboticiens. Cette thèse s'illustre donc par une collaboration à la fois avec des mathématiciens du contrôle et des spécialistes de la modélisation des primitives motrices. Les contributions majeures de cette thèse reposent donc sur la conception de nouveaux algorithmes temps-réel de contrôle pour la locomotion des robots humanoïdes avec nos collégues de l'université d'Heidelberg et leur intégration sur le robot HRP-2. Deux contrôleurs seront présentés, le premier permettant la locomotion multi-contacts avec une connaissance a priori des futures positions des contacts. Le deuxième étant une extension d'un travail réalisé sur de la marche sur sol plat améliorant les performances et ajoutant des fonctionnalitées au précédent algorithme. En collaborant avec des spécialistes du mouvement humain nous avons implementé un contrôleur innovant permettant de suivre des trajectoires cycliques du centre de masse. Nous présenterons aussi un contrôleur corps-complet utilisant, pour le haut du corps, des primitives de mouvements extraites du mouvement humain et pour le bas du corps, un générateur de marche. Les résultats de cette thèse ont été intégrés dans la suite logicielle "Stack-of-Tasks" du LAAS-CNRS.This thesis covers the topic of humanoid robot locomotion in the frame of the European project KoroiBot. The goal of this project is to enhance the ability of humanoid robots to walk in a dynamic and versatile fashion as humans do. Research and innovation studies in KoroiBot rely on optimal control methods both for the identification of cost functions used by human being and for their implementations on robots owned by roboticist partners. Hence, this thesis includes fruitful collaborations with both control mathematicians and experts in motion primitive modeling. The main contributions of this PhD thesis lies in the design of new real time controllers for humanoid robot locomotion with our partners from the University of Heidelberg and their integration on the HRP-2 robot. Two controllers will be shown, one allowing multi-contact locomotion with a prior knowledge of the future contacts. And the second is an extension of a previous work improving performance and providing additional functionalities. In a collaboration with experts in human motion we designed an innovating controller for tracking cyclic trajectories of the center of mass. We also show a whole body controller using upper body movement primitives extracted from human behavior and lower body movement computed by a walking pattern generator. The results of this thesis have been integrated into the LAAS-CNRS "Stack-of-Tasks" software suit