CAD-based approach for identification of elasto-static parameters of robotic manipulators

The paper presents an approach for the identification of elasto-static parameters of a robotic manipulator using the virtual experiments in a CAD environment. It is based on the numerical processing of the data extracted from the finite element analysis results, which are obtained for isolated manipulator links. This approach allows to obtain the desired stiffness matrices taking into account the complex shape of the links, couplings between rotational/translational deflections and particularities of the joints connecting adjacent links. These matrices are integral parts of the manipulator lumped stiffness model that are widely used in robotics due to its high computational efficiency. To improve the identification accuracy, recommendations for optimal settings of the virtual experiments are given, as well as relevant statistical processing techniques are proposed. Efficiency of the developed approach is confirmed by a simulation study that shows that the accuracy in evaluating the stiffness matrix elements is about 0.1%.Comment: arXiv admin note: substantial text overlap with arXiv:0909.146

Outils pour l’identification des paramètres de raideur des robots à l’aide d’un logiciel de CAO

This report proposes a CAD-based approach for identification of the elasto-static parameters of the robotic manipulators. The main contributions are in the areas of virtual experiment planning and algorithmic data processing, which allows to obtain the stiffness matrix with required accuracy. In contrast to previous works, the developed technique operates with the deflection field produced by virtual experiments in a CAD environment. The proposed approach provides high identification accuracy (about 0.1% for the stiffness matrix element) and is able to take into account the real shape of the link, coupling between rotational/translational deflections and joint particularities. To compute the stiffness matrix, the numerical technique has been developed, and some recommendations for optimal settings of the virtual experiments are given. In order to minimize the identification errors, the statistical data processing technique was applied. The advantages of the developed approach have been confirmed by case studies dealing with the links of parallel manipulator of the Orthoglide family, for which the identification errors have been reduced to 0.1%ANR COROUSS

Outils pour l’identification des paramètres de raideur des robots à l’aide d’un logiciel de CAO

This report proposes a CAD-based approach for identification of the elasto-static parameters of the robotic manipulators. The main contributions are in the areas of virtual experiment planning and algorithmic data processing, which allows to obtain the stiffness matrix with required accuracy. In contrast to previous works, the developed technique operates with the deflection field produced by virtual experiments in a CAD environment. The proposed approach provides high identification accuracy (about 0.1% for the stiffness matrix element) and is able to take into account the real shape of the link, coupling between rotational/translational deflections and joint particularities. To compute the stiffness matrix, the numerical technique has been developed, and some recommendations for optimal settings of the virtual experiments are given. In order to minimize the identification errors, the statistical data processing technique was applied. The advantages of the developed approach have been confirmed by case studies dealing with the links of parallel manipulator of the Orthoglide family, for which the identification errors have been reduced to 0.1%ANR COROUSS

A randomized kinodynamic planner for closed-chain robotic systems

Kinodynamic RRT planners are effective tools for finding feasible trajectories in many classes of robotic systems. However, they are hard to apply to systems with closed-kinematic chains, like parallel robots, cooperating arms manipulating an object, or legged robots keeping their feet in contact with the environ- ment. The state space of such systems is an implicitly-defined manifold, which complicates the design of the sampling and steering procedures, and leads to trajectories that drift away from the manifold when standard integration methods are used. To address these issues, this report presents a kinodynamic RRT planner that constructs an atlas of the state space incrementally, and uses this atlas to both generate ran- dom states, and to dynamically steer the system towards such states. The steering method is based on computing linear quadratic regulators from the atlas charts, which greatly increases the planner efficiency in comparison to the standard method that simulates random actions. The atlas also allows the integration of the equations of motion as a differential equation on the state space manifold, which eliminates any drift from such manifold and thus results in accurate trajectories. To the best of our knowledge, this is the first kinodynamic planner that explicitly takes closed kinematic chains into account. We illustrate the performance of the approach in significantly complex tasks, including planar and spatial robots that have to lift or throw a load at a given velocity using torque-limited actuators.Peer ReviewedPreprin

Three Essays in Comparative Political Economy

This thesis consists of three chapters. The first two chapters offer game theoretical models for different linkages between political parties and the citizens: programmatic linkage and clientelistic linkage. Empirical implications of these models are discussed using real world data on Turkey and USA through statistical analysis and simulation. The last chapter steps back from the specific strategies of political agents to examine in a more general context the concepts of institutional maintenance and institutional change

Algorithmes adaptatifs pour la simulation moléculaire

Les simulations moléculaires sont devenues un outil essentiel en biologie, chimie et physique. Malheureusement, elles restent très couteuses. Dans cette thèse, nous proposons des algorithmes qui accélèrent les simulations moléculaires en regroupant des particules en plusieurs objets rigides. Nous étudions d'abord plusieurs algorithmes de recherche de voisins dans le cas des grands objets rigides, et démontrons que les algorithmes hiérarchiques permettent d'obtenir des accélérations importantes. En conséquence, nous proposons une technique pour construire une représentation hiérarchique d'un graphe moléculaire arbitraire. Nous démontrons l'usage de cette technique pour la mécanique adaptative en angles de torsion, une méthode de simulation qui décrit les molécules comme des objets rigides articulés. Enfin, nous introduisons ARPS - Adaptively Restrained Particle Simulations ("Simulations de particules restreintes de façon adaptative") - une méthode mathématiquement fondée capable d'activer et de désactiver les degrés de liberté en position. Nous proposons deux stratégies d'adaptation, et illustrons les avantages de ARPS sur plusieurs exemples. En particulier, nous démontrons comment ARPS permet de choisir finement le compromis entre précision et vitesse, ainsi que d'obtenir rapidement des statistiques non biaisées sur les systèmes moléculaires.Molecular simulations have become an essential tool in biology, chemistry and physics. Unfortunately, they still remain computationally challenging. In this dissertation, we propose algorithms that accelerate molecular simulations by clustering particles into rigid bodies. We first study several neighbor-search algorithms for large rigid bodies, and show that hierarchy-based algorithms may provide significant speedups. Accordingly, we propose a technique to build a hierarchical representation of an arbitrary molecular graph. We show how this technique can be used in adaptive torsion-angle mechanics, a simulation method that describes molecules as articulated rigid bodies. Finally, we introduce ARPS - Adaptively Restrained Particle Simulations - a mathematically-grounded method able to switch positional degrees of freedom on and off. We propose two switching strategies, and illustrate the advantages of ARPS on various examples. In particular, we show how ARPS allow us to smoothly trade between precision and speed, and efficiently collect unbiased statistics on molecular systems.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF

Adaptive Physically Based Models in Computer Graphics

International audienceOne of the major challenges in physically-based modeling is making simulations efficient. Adaptive models provide an essential solution to these efficiency goals. These models are able to self-adapt in space and time, attempting to provide the best possible compromise between accuracy and speed. This survey reviews the adaptive solutions proposed so far in computer graphics. Models are classified according to the strategy they use for adaptation, from time-stepping and freezing techniques to geometric adaptivity in the form of structured grids, meshes, and particles. Applications range from fluids, through deformable bodies, to articulated solids

Automatic Flight Control Systems

The history of flight control is inseparably linked to the history of aviation itself. Since the early days, the concept of automatic flight control systems has evolved from mechanical control systems to highly advanced automatic fly-by-wire flight control systems which can be found nowadays in military jets and civil airliners. Even today, many research efforts are made for the further development of these flight control systems in various aspects. Recent new developments in this field focus on a wealth of different aspects. This book focuses on a selection of key research areas, such as inertial navigation, control of unmanned aircraft and helicopters, trajectory control of an unmanned space re-entry vehicle, aeroservoelastic control, adaptive flight control, and fault tolerant flight control. This book consists of two major sections. The first section focuses on a literature review and some recent theoretical developments in flight control systems. The second section discusses some concepts of adaptive and fault-tolerant flight control systems. Each technique discussed in this book is illustrated by a relevant example