Examinando por Materia "Cinemática inversa"
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Ítem Computational Geometry in Medical Applications(Universidad EAFIT, 2016) Cortés Acosta, Camilo Andrés; Ruíz Salguero, Óscar Eduardo; Flórez Esnal, JuliánÍtem Experiment design in compliant mechanisms and kinematic identification of parallel mechanisms(Universidad EAFIT, 2010) Restrepo Arango, David; Ruíz Salguero, Oscar EduardoThis article discusses a procedure for force-displacement modeling compliant mechanisms by using a design of computer experiments methodology -- This approach produces a force-displacement meta-model that is suited for real-time control of compliant mechanisms -- The term meta-model is used to represent a simplified and efficient mathematical model of unknown phenomena -- The meta-modeling of compliant mechanisms is performed from virtual experiments based on factorial- and space-filling design of experiments -- The procedure is used to model the quasi-static behavior of the HexFlex compliant mechanism -- The HexFlex is a parallel compliant mechanism for nano-manipulation that allows six degrees of freedom of its moving stage -- The meta-model of the HexFlex is calculated from experiments with the Finite Element Method (FEM) -- The obtained meta-model for the HexFlex is linear for the range of movement of the mechanism -- The accuracy of the meta-model was calculated conducting a set of computer experiments with random uniform distribution of the input forces -- Three criteria were calculated in each displacement direction (x, y, z, θx, θy, θz) comparing the meta-model prediction with respect to the results of the virtual experiments: 1. maximum of the absolute value of the error, 2. relative error, and 3. root mean square error -- The maximum errors were founded adequate with respect to demanding manufacturing tolerances (absolute errors) and lower than errors reported by other authors (relative errors)Ítem Finite Element Modeling of Composite Materials using Kinematic Constraints(Universidad EAFIT, 2009-12) Barschke, Merlin; Uribe, David; Ruíz, Óscar E.; Jensen, Jens; López, Carlos; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEEl propósito de este artículo es presentar simulaciones del comportamiento de materiales compuestos basado en restricciones cinemáticas entre las mismas fibras y entre las fibras y la resina circundante -- En la revisión de literatura, los autores han encontrado que las restricciones cinemáticas no han sido plenamente explotadas para modelar materiales compuestos, probablemente debido a su alto costo computacional -- El propósito de este artículo es exponer la implementación y resultados de tal modelo, usando Análisis por Elementos Finitos de restricciones geométricas prescritas a los nodos de la resina y las fibras -- Las descripciones analíticas del comportamiento de materiales compuestos raramente aparecen -- Muchas aproximaciones para describir materiales compuestos en capas son basadas en la teoría de funciones C1 Z y C0Z, tal como la Teoría Clásica de Capas (CLT) -- Estas teorías de funciones contienen significativas simplificaciones del material, especialmente para compuestos tejidos -- Una aproximación hibrida para modelar materiales compuestos con Elementos Finitos (FEA) fue desarrollada por Sidhu y Averill [1] y adaptada por Li y Sherwood [2] para materiales compuestos tejidos con polipropileno de vidrio -- Este artículo presenta un método para obtener valores para las propiedades de los materiales compuestos -- Tales valores son usados para simular las fibras reforzadas tejidas aplicando elementos de capas en el software ANSYS -- El presente modelo requiere menos simplificaciones que las teorías C1Z y C0Z -- En el artículo presente, a diferencia del modelo Li–Sherwood, el tejido es modelado geométricamente -- Una Representación por la Frontera (B-Rep del modelo “Hand”) con genus 1 (con geometría compleja) fue usada para aplicar restricciones geométricas a las capas de resina, fibra, etcétera, mostrando que es apropiada para simular estructuras complejas -- En el futuro, las propiedades no–lineales de los materiales deben ser consideradas, y el trabajo experimental requerido debe ser realizadoÍtem Inverse kinematics for upper limb compound movement estimation in exoskeleton-assisted rehabilitation(Hindawi Publishing Corp., 2016-05-16) Cortés, Camilo; De los Reyes-Guzmán, Ana; Scorza, Davide; Bertelsen, Álvaro; Carrasco, Eduardo; Gil-Agudo, Ángel; Ruíz-Salguero, Óscar; Flórez, Julián; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAERobot-Assisted Rehabilitation (RAR) is relevant for treating patients affected by nervous system injuries (e.g., stroke and spinal cord injury) -- The accurate estimation of the joint angles of the patient limbs in RAR is critical to assess the patient improvement -- The economical prevalent method to estimate the patient posture in Exoskeleton-based RAR is to approximate the limb joint angles with the ones of the Exoskeleton -- This approximation is rough since their kinematic structures differ -- Motion capture systems (MOCAPs) can improve the estimations, at the expenses of a considerable overload of the therapy setup -- Alternatively, the Extended Inverse Kinematics Posture Estimation (EIKPE) computational method models the limb and Exoskeleton as differing parallel kinematic chains -- EIKPE has been tested with single DOFmovements of the wrist and elbow joints -- This paper presents the assessment of EIKPEwith elbow-shoulder compoundmovements (i.e., object prehension) -- Ground-truth for estimation assessment is obtained from an optical MOCAP (not intended for the treatment stage) -- The assessment shows EIKPE rendering a good numerical approximation of the actual posture during the compoundmovement execution, especially for the shoulder joint angles -- This work opens the horizon for clinical studies with patient groups, Exoskeleton models, and movements types --Ítem Kinematic identification of parallel mechanisms by a divide and conquer strategy(2010) Durango, Sebastián; Restrepo, David; Ruíz, Óscar; Restrepo-Giraldo, John; Achiche, Sofiane; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEThis paper presents a Divide and Conquer strategy to estimate the kinematic parameters of parallel symmetrical mechanisms -- The Divide and Conquer kinematic identification is designed and performed independently for each leg of the mechanism -- The estimation of the kinematic parameters is performed using the inverse calibration method -- The identification poses are selected optimizing the observability of the kinematic parameters from a Jacobian identification matrix -- With respect to traditional identification methods the main advantages of the proposed Divide and Conquer kinematic identification strategy are: (i) reduction of the kinematic identification computational costs, (ii) improvement of the numerical efficiency of the kinematic identification algorithm and, (iii) improvement of the kinematic identification results -- The contributions of the paper are: (i) The formalization of the inverse calibration method as the Divide and Conquer strategy for the kinematic identification of parallel symmetrical mechanisms and, (ii) a new kinematic identification protocol based on the Divide and Conquer strategy -- As an application of the proposed kinematic identification protocol the identification of a planar 5R symmetrical mechanism is simulated -- The performance of the calibrated mechanism is evaluated by updating the kinematic model with the estimated parameters and developing simulationsÍtem Symmetrical Observability of Kinematic Parameters in Symmetrical Parallel Mechanisms(Editora Edgard Blücher Ltda., 2014-05) Durango, S.; Restrepo, D.; Ruíz, O.; Restrepo-Giraldo, J.; Achiche, S.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAEThis article presents an application of symmetry group theory in kinematic identification of parallel mechanisms of nlegs legs -- Kinematic Identification implies the estimation of the actual geometrical parameters (as opposed to nominal ones) of a physical mechanism -- For a symmetric mechanism, KI requires configuring sets of leg positions with symmetrical observability – This article presents as main contributions: (i) a conjecture that allows mapping the symmetries of the mechanism into the active-joint workspace, (ii) a set of necessary conditions to express leg parameters in coordinate systems which allow symmetrical observability, and (iii) a procedure for exploiting symmetries in pose selection for kinematic identification of symmetrical parallel mechanisms -- For the kinematic identification itself, we adopt a divide-and-conquer (DC) identification protocol -discussed by us in another publication- in which each leg of the mechanism is independently identified by using the inverse calibration method -- In this article we emphasize how to exploit the symmetries existent in (nlegs − 1) legs of the parallel mechanism allowing to apply to other legs the symmetry-transformed sample protocol used for the kinematic identification of a reference leg -- The symmetrical observability of sets of leg parameters allows to reduce the costs of the pose selection procedure by a factor of (1/nlegs) compared to a complete DC procedure in which the poses of each leg are selected independently -- The pose selection is carried out only for the reference leg -- For the (nlegs−1) remaining legs the poses are dictated by symmetry operations performed onto the poses of the reference leg -- An application of the symmetrical observability is presented through the simulated kinematic identification of a 3RRR symmetrical parallel mechanism