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  • Combining vibrational linear-by-part dynamics and kinetic-based decoupling of the dynamics for multiple smooth impacts with redundancy

     Barjau Condomines, Ana; Agullo Batlle, Joaquim; Font Llagunes, Josep Maria
    Multibody system dynamics
    Date of publication: 2014-04
    Journal article

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    This article proposes a simple linear-by-part approach for perfectly elastic 3D multiple-point impacts in multibody systems with perfect constraints and no friction, applicable both to nonredundant and redundant cases (where the normal velocities of the contact points are not independent). The approach is based on a vibrational dynamical model, and uses the so called ¿independent contact space.¿ Two different time and space scales are used. At the macroscale, the impact interval is negligible, and the overall system configuration is assumed to be constant. Consequently, the inertia and Jacobian matrices appearing in the formulation are also constant. The dynamics at the contact points is simulated through stiff springs undergoing very small deformations and generating system vibrations at the microscale.

  • Parameter identification method for a three-dimensional foot¿ground contact model

     Pamies Vila, Rosa; Font Llagunes, Josep Maria; Lugrís, Urbano; Cuadrado, Javier
    Mechanism and machine theory
    Date of publication: 2014-05-01
    Journal article

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  • Validation of the inverse dynamic analysis of human gait using a forward dynamics approach

     Pamies Vila, Rosa; Font Llagunes, Josep Maria
    ASME International Conference on Multibody Systems, Nonlinear Dynamics, and Control
    Presentation's date: 2013-08-06
    Presentation of work at congresses

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    One of the aims of the dynamic analysis of human gait is to know the joint forces and torques that the musculoskeletal system produces during the motion. For this purpose, an 18 segment 3D model with 57 degrees of freedom is implemented. The analysis of a captured motion can be addressed by means of forward or inverse dynamic analyses. In this work, both analyses are computed using multibody dynamics techniques. The forward dynamic analysis is carried out with the aim of simulating the movement of the multibody system using the results of the inverse problem as input data. Since the inverse analysis is solved using a dynamically consistent methodology, the forward dynamic analysis allows us to simulate up to the 90% of the gait cycle without any controller. After that, a proportional derivative (PD) controller is implemented to stabilize the system, which gets to simulate the complete captured motion. Moreover, the dynamic contribution of the controller is really low and the simulated motion is extremely close to the original one. The methodology presented allows us to validate the correctness of the inverse dynamics analysis and it is an intermediate step towards the prediction problem: it requires dynamical consistency too, but the uncertainties involved in the problem are lower than in a predictive approach.

  • Formulation to predict lower limb muscle forces during gait

     Serrancoli Masferrer, Gil; Walter, J.P.; Kinney, A.L.; Barjau Condomines, Ana; Fregly, Benjamin J.; Font Llagunes, Josep Maria
    Reunión del Capítulo Español de la Sociedad Europea de Biomecánica
    Presentation's date: 2013-10-24
    Presentation of work at congresses

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  • Forward dynamics for gait analysis as an intermediate step to motion prediction

     Cuadrado, Javier; Lugrís, Urbano; Pamies Vila, Rosa; Font Llagunes, Josep Maria
    International and National Conference on Machines and Mechanisms
    Presentation's date: 2013-12-18
    Presentation of work at congresses

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    Human motion prediction through computational simulation can serve as a tool to anticipate the result of surgery or to help in the design of prosthetic/orthotic devices. The latter is the motivation in a project being run by the authors, devoted to the design of an active stance-control knee-ankle-foot orthosis (SCKAFO) as an assistive device for the gait of incomplete spinal cord injured (SCI) subjects. Optimization is a well-suited technique to tackle the human motion prediction problem, and several approaches have been proposed in the literature. However, no matter which is the used approach, the implementation of these methods represents a great challenge in terms of both convergence and efficiency. Therefore, the authors intend to firstly address the analysis of a certain measured motion through forward dynamics, which can be considered as an intermediate step towards the prediction problem, since it requires dynamical consistency too, but does not suffer from the same high amount of uncertainty. Consequently, a systematic study of the different alternatives to obtain, through forward dynamics, the drive efforts at joint level that produce a certain known motion is started in this paper. Three model-based control methods have been implemented for the gait of a healthy subject, and their performances have been compared.

  • Solution methods for the double-support indeterminacy in human gait

     Lugrís, Urbano; Carlín, Jairo; Pamies Vila, Rosa; Font Llagunes, Josep Maria; Cuadrado, Javier
    Multibody system dynamics
    Date of publication: 2013-04-01
    Journal article

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    There is a growing interest in predicting the gait motion of real subjects under virtual conditions, e.g., to anticipate the result of surgery or to help in the design of prosthetic/orthotic devices. To this end, the motion parameters can be considered as the design parameters of an optimization problem. In this context, determination of the joint efforts for a given motion is a required step for the subsequent evaluation of cost function and constraints. In the double-support phase of gait, the ground reaction forces include twelve unknowns, rendering the inverse dynamics problem indeterminate if no force plate data are available. In this paper, several methods for solving the inverse dynamics problem of the human gait during the double-support phase, using force plates or not, are presented and compared.

    There is a growing interest in predicting the gait motion of real subjects under virtual conditions, e.g., to anticipate the result of surgery or to help in the design of prosthetic/ orthotic devices. To this end, the motion parameters can be considered as the design parameters of an optimization problem. In this context, determination of the joint efforts for a given motion is a required step for the subsequent evaluation of cost function and constraints. In the double-support phase of gait, the ground reaction forces include twelve unknowns, rendering the inverse dynamics problem indeterminate if no force plate data are available. In this paper, several methods for solving the inverse dynamics problem of the human gait during the double-support phase, using force plates or not, are presented and compared.

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    Aplicación de técnicas de dinámica multicuerpo al diseño de ortesis activas para ayuda a la marcha  Open access

     Cuadrado, Javier; Lugrís, Urbano; Alonso Sánchez, Francisco Javier; Font Llagunes, Josep Maria
    Congreso Nacional de Ingeniería Mecánica
    Presentation's date: 2012-11-14
    Presentation of work at congresses

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    A linear-by-part approach for dissipative multiple-point collisions in smooth multibody systems with perfect constraints  Open access

     Barjau Condomines, Ana; Agullo Batlle, Joaquim; Font Llagunes, Josep Maria
    Joint International Conference on Multibody System Dynamics
    Presentation's date: 2012-05-30
    Presentation of work at congresses

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    Estimación de los parámetros del modelo de contacto pie-suelo en la marcha humana  Open access

     Pamies Vila, Rosa; Font Llagunes, Josep Maria; Lugrís, Urbano; Cuadrado, Javier
    Congreso Nacional de Ingeniería Mecánica
    Presentation's date: 2012-11-14
    Presentation of work at congresses

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    En el campo de la biomecánica existe un interés creciente en la predicción de la marcha humana. Para poder determinar cómo se moverá un sistema debido a las fuerzas y momentos que se aplican sobre él (análisis dinámico directo) es necesario modelar adecuadamente la interacción del sistema con el entorno. En el caso de la marcha humana, esto exige la modelización de la interacción entre el pie y el suelo. Con este propósito, se propone un modelo tridimensional continuo de contacto pie-suelo. Los parámetros dinámicos del modelo se estiman mediante técnicas de optimización. En este estudio se utilizan dos modelos biomecánicos. Por un lado el modelo de cuerpo entero y por el otro el modelo de pie. La fuerza y el par en el tobillo obtenidos mediante un análisis dinámico inverso de la marcha utilizando el sistema de cuerpo entero (de 57 grados de libertad) son utilizados como datos de entrada en el modelo de pie para realizar el análisis dinámico directo con el que se estiman los parámetros del modelo de contacto. Para validar los resultados, se ha comparado el movimiento y las fuerzas de contacto obtenidos mediante la simulación dinámica directa con los medidos en el laboratorio.

    Premio al Mejor Trabajo de Investigación Básica en el XIX Congreso Nacional de Ingeniería Mecánica

  • Analysis of different uncertainties in the inverse dynamic analysis of human gait

     Pamies Vila, Rosa; Font Llagunes, Josep Maria; Cuadrado, Javier; Alonso Sánchez, Francisco Javier
    Mechanism and machine theory
    Date of publication: 2012-12-01
    Journal article

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  • Dynamic analysis of impact in swing-through crutch gait using impulsive and continuous contact models

     Font Llagunes, Josep Maria; Barjau Condomines, Ana; Pamies Vila, Rosa; Kövecses, József
    Multibody system dynamics
    Date of publication: 2012-09-01
    Journal article

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    The dynamics associated with the impact of the crutch with the ground is an important topic of research, since this is known to be the main cause of mechanical energy loss during swing-through gait. In this work, a multibody system representing a subject walking with crutches is used to investigate the behavior of two different contact models, impulsive and continuous, used for impact analysis. In the impulsive (discrete) approach, the impact interval is considered to be negligible and, therefore, the system configuration is constant. The postimpact state is directly obtained from the preimpact one through algebraic equations. In the continuous approach, the stiffness and dissipation characteristics of the contact surfaces are modeled through nonlinear springs and dampers. The equations of motion are integrated during the impact time interval to obtain the postimpact state, which, in principle, can differ from that obtained by means of the impulsive approach. Although both approaches have been widely used in the field of biomechanics, we have not found any comparative study in the existing literature justifying the model chosen for impact analysis. In this work, we present detailed numerical results and discussions to investigate several dynamic and energetic features associated with crutch impact. Based on the results, we compare the implications of using one contact model or the other.

  • New biomechanical model for clinical evaluation of the upper extremity motion in subjects with neurological disorders: an application case

     Lobo-Prat, Joan; Font Llagunes, Josep Maria; Gómez-Pérez, Cristrina; Medina-Casanovas, Josep; Angulo-Barroso, Rosa M.
    Computer methods in biomechanics and biomedical engineering
    Date of publication: 2012-11-27
    Journal article

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  • Application of Multibody Dynamics Techniques to the Analysis of Human Gait  Open access

     Pamies Vila, Rosa
    Defense's date: 2012-12-21
    Department of Automatic Control, Universitat Politècnica de Catalunya
    Theses

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    La tesi que es presenta tracta l’estudi cinemàtic i dinàmic de la marxa humana mitjançant tècniques de dinàmica de sistemes multisòlid. Per a aquest propòsit, s’utilitzen dos models biomecànics: un model pla format per 11 segments i 14 graus de llibertat i un model tridimensional format per 18 segments i 57 graus de llibertat. La formulació dinàmica multisòlid ha estat desenvolupada en coordenades mixtes (naturals i relatives). La marxa de l’individu s’enregistra al laboratori utilitzant un sistema de captura del moviment mitjançant el qual s’obté la posició de cadascun dels 37 marcadors situats sobre el cos del subjecte. Les dades de posició es filtren utilitzant un algorisme basat en el singular spectrum analysis (SSA) i les coordenades naturals del model es calculen mitjançant relacions algebraiques entre les posicions dels marcadors. Posteriorment, un procés de consistència cinemàtica assegura les restriccions de sòlid rígid. El processament cinemàtic continua amb l’aproximació de les posicions mitjançant corbes B-spline d’on se n’obtenen, per derivació analítica, els valors de velocitat i acceleració. En una anàlisi dinàmica inversa de la marxa humana, s’acostumen a utilitzar com a dades d’entrada els paràmetres antropomètrics (geomètrics i inercials) dels segments, les dades cinemàtiques i les mesures de les plaques de força. En contraposició al que fan la majoria d’autors, en aquesta tesi, les mesures de les plaques de força no són utilitzades directament en l’anàlisi sinó que només s’usen per solucionar el problema del repartiment del torsor resultant de les forces de contacte durant la fase de doble suport. En aquesta fase, els dos peus es recolzen sobre el terra i les mesures cinemàtiques són insuficients per determinar el torsor en cada peu. El nou mètode de repartiment que es proposa (anomenat contact force plate sharing, CFP) és una de les aportacions de la tesi i destaca pel fet que permet determinar un conjunt de forces i moments dinàmicament consistents amb el model biomecànic, sense haver de modificar-ne les coordenades cinemàtiques ni afegir forces o moments residuals en algun dels segments. Encara dins l’àmbit de l’estudi dinàmic invers, s’ha analitzat la sensitivitat dels parells articulars a errors comesos en estimar els paràmetres antropomètrics, a errors que poden contenir les mesures de les plaques de força i a errors que es poden cometre en el processament cinemàtic de les mesures. L’estudi permet concloure que els resultats són molt sensibles als errors cinemàtics i a les forces mesurades per les plaques, sent els errors en els paràmetres antropomètrics menys influents. La tesi també presenta un nou model tridimensional de contacte peu-terra basat en el contacte esfera-pla i els seus paràmetres s’estimen mitjançant dos enfocaments diferents basats en tècniques d’optimització. El model s’utilitza com un mètode alternatiu per solucionar el problema del repartiment durant la fase de doble suport en dinàmica inversa, i també s’utilitza en simulacions de dinàmica directa per estimar les forces de contacte entre el model biomecànic i el seu entorn. En l’anàlisi dinàmica directa és necessària la implementació d’un controlador que està basat, en aquest cas, en el filtre de Kalman estès. Les contribucions més importants de la tesi, en el cas de l’anàlisi dinàmica inversa, es centren en el mètode CFP i en l’ús del model de contacte per solucionar el repartiment de forces de contacte en la fase de doble suport. Referent a l’anàlisi de la influència dels errors en les dades d’entrada del problema dinàmic invers, la modelització estadística dels errors conjuntament amb la pertorbació conjunta de més d’un paràmetre antropomètric a la vegada (mantenint constant l’alçada i el pes de la persona) és també una novetat. Per altra banda, el model de contacte presentat és també una contribució original. En l’estat de l’art actual no es troben models que usin dades reals capturades al laboratori i que a la vegada s’utilitzin per solucionar el problema de repartiment en el doble suport i per simular el contacte peu-terra en una anàlisi dinàmica directa. Finalment, el fet de desenvolupar un model que s’utilitzi tant per a l’anàlisi dinàmica directa com inversa és també una de les aportacions d’aquesta tesi. Tot i que les dues anàlisis, per separat, són temes de recerca comuns en l’àmbit de la Biomecànica, es troben a faltar estudis que comprovin la validesa dels resultats que se n’obtenen. En aquesta tesi, els resultats de la dinàmica inversa s’han utilitzat com a dades d’entrada de l’anàlisi dinàmica directa, el resultat de la qual (el moviment) ha pogut ser comparat amb el que s’obté de la captura del laboratori (entrada de la dinàmica inversa). D’aquesta manera, el cercle es tanca i es pot verificar la validesa tant dels models com dels resultats obtinguts.

    This thesis presents the kinematic and dynamic study of human motion by means of multibody system dynamics techniques. For this purpose, two biomechanical models are used: a 2D model formed by 11 segments with 14 degrees of freedom, and a 3D model that consists of 18 segments with 57 degrees of freedom. The movement of the subject is recorded in the laboratory using a motion capture system that provides the position along time of 37 markers attached on the body of the subject. Position data are filtered using an algorithm based on singular spectrum analysis (SSA) and the natural coordinates of the model are calculated using algebraic relations between the marker positions. Afterwards, a kinematic procedure ensures the kinematic consistency and the data processing continues with the approximation of the position histories using B-spline curves and obtaining, by analytical derivation, the velocity and acceleration values. This information is used as input of an inverse dynamic analysis. Differing to most published works, in this thesis the force plates measurements are not used directly as inputs of the analysis. When both feet contact the ground, kinematic measurements are insufficient to determine the individual wrench at each foot. One of the contributions of the thesis is a new strategy that is proposed to solve the this indeterminacy (called corrected force plate sharing, CFP) based on force plates data. Using this method, a set of two contact wrenches dynamically consistent with the movement are obtained with no need neither to add residual wrenches nor to modify the original motion. Also in the IDA field, the sensitivity of the joint torques to errors in the anthropometric parameters, in the force plate measurements and to errors committed during the kinematic data processing is studied. The analysis shows that the results are very sensitive to errors in force measurements and in the kinematic processing, being the errors in the body segment parameters less influential. A new 3D foot-ground contact model is presented and its parameters are estimated using optimization techniques. The model is used as an alternative method to solve the mentioned sharing problem during the double support phase and it is also used, in a forward dynamic analysis, to estimate the contact forces between the biomechanical model and its environment. The forward dynamic simulation requires the implementation of a controller that is based, in this case, on the extended Kalman filter. The most important contributions of the thesis in IDA are focused on the CFP sharing method and regarding the analysis of the influence of errors in input data on the inverse dynamics results, the statistical modelling of the uncertainties together with the perturbation of more than one parameter at same time (remaining height and weight as a constant parameters) is also new in the literature. Moreover, the presented foot-ground contact model is also original. In the current state of the art, there are no models that use real data captured in the laboratory to solve the contact wrench sharing problem during the double support phase. Furthermore, there are few studies simulating the foot-ground interaction in a forward dynamic analysis using a continuous foot-ground contact model. Finally, developing a model that is used for both forward and inverse dynamic analysis is a relevant aspect of the methodology used. Although the two approaches separately are common research topics in the field of biomechanics, a small number of studies prove the validity of the obtained results. In this thesis, the results of the inverse dynamics are used as input data for the forward dynamic analysis, and the results of the latter (the motion) have been compared with the motion capture in the laboratory (input of the inverse dynamics analysis). Thus, the circle has been closed which allows us to validate the accuracy of both the models and the obtained results.

  • Multi-scale biomechanical study of transport phenomena in the intervertebral disc  Open access

     Malandrino, Andrea
    Defense's date: 2012-07-26
    Department of Automatic Control, Universitat Politècnica de Catalunya
    Theses

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    Intervertebral disc (IVD) degeneration is primarily involved in back pain, a morbidity that strongly affects the quality of life of individuals nowadays. Lumbar IVDs undergo stressful mechanical loads while being the largest avascular tissues in our body: Mechanical principles alone cannot unravel the intricate phenomena that occur at the cellular scale which are fundamental for the IVD regeneration. The present work aimed at coupling biomechanical and relevant molecular transport processes for disc cells to provide a mechanobiological finite element framework for a deeper understanding of degenerative processes and the planning of regenerative strategies. Given the importance of fluid flow within the IVD, the influence of poroelastic parameters such as permeabilities and solid-phase stiffness of the IVD subtissues was explored. A continuum porohyperelastic material model was then implemented. The angles of collagen fibers embedded in the annulus fibrosus (AF) were calibrated. The osmotic pressure of the central nucleus pulposus (NP) was also taken into account. In a parallel study of the human vertebral bone, microporomechanics was used together with experimental ultrasonic tests to characterize the stiffness of the solid matrix, and to provide estimates of poroelastic coefficients. Fluid dynamics analyses and microtomographic images were combined to understand the fluid exchanges at the bone-IVD interface. The porohyperelastic model of a lumbar IVD with poroelastic vertebral layers was coupled with a IVD transport model of three solutes - oxygen, lactate and glucose - interrelated to reproduce the glycolytic IVD metabolism. With such coupling it was possible to study the effect of deformations, fluid contents, solid-phase stiffness, permeabilities, pH, cell densities of IVD subtissues and NP osmotic pressure on the solute transport. Moreover, cell death governed by glucose deprivation and lactate accumulation was included to explore the mechanical effect on cell viability. Results showed that the stiffness of the AF had the most remarkable role on the poroelastic behavior of the IVD. The permeability of the thin cartilage endplate and the NP stiffness were also relevant. The porohyperelastic model was shown to reproduce the local AF mechanics, provided the fiber angles were calibrated regionally. Such back-calculation led to absolute values of fibers angles and to a global IVD poromechanical behavior in agreement with experiments in literature. The inclusion of osmotic pressure in the NP also led to stress values under confined compression comparable to those measured in healthy and degenerated NP specimens. For the solid bone matrix, axial and transverse stiffness coefficients found experimentally in the present work agreed with universal mass density-elasticity relationships, and combined with continuum microporomechanics provided poroelastic coefficients for undrained and drained cases. The effective permeability of the vertebral bony endplate calculated with fluid dynamics was highly correlated with the porosity measured in microtomographic images. The coupling of transport and porohyperelastic models revealed a mechanical effect acting under large volume changes and high compliance, favored by healthy rather than degenerated IVD properties. Such effect was attributed to strain-dependent diffusivities and diffusion distances and was shown to be beneficial for IVD cells due to the load-dependent increases of glucose levels. Cell density, NP osmotic pressure and porosity were the most important parameters affecting the coupled mechano-transport of metabolites. This novel study highlights the restoration of both cellular and mechanical factors and has a great potential impact for novel designs of treatments focused on tissue regeneration. It also provides methodological features that could be implemented in clinical image-based tools and improve the multiscale understanding of the human spine mechanobiology.

  • Mixed displacement-pressure brick element formulation based on the absolute nodal coordinate formulation

     Altarriba, Elias; Font Llagunes, Josep Maria; Mikkola, Aki M.
    Date of publication: 2012-09-26
    Book

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  • Premi al millor treball de recerca bàsica del XIX Congreso Nacional de Ingeniería Mecánica

     Pamies Vila, Rosa; Font Llagunes, Josep Maria; Lugrís, Urbano; Cuadrado, Javier
    Award or recognition

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  • Premis Projecte de Fi de Carrera Fundación Universia per a l'estudiantat de la UPC 2011

     Font Llagunes, Josep Maria; Arroyo, Guillermo
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  • A simple approach to estimate muscle forces and orthosis actuation in powered assisted walking of spinal cord-injured subjects

     Alonso, Javier; Romero, Francisco; Pamies Vila, Rosa; Lugrís, Urbano; Font Llagunes, Josep Maria
    Multibody system dynamics
    Date of publication: 2012-08-01
    Journal article

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    Hybrid modeling and fractional control of a SCKAFO orthosis for gait assistance  Open access

     HosseinNia, S. Hassan; Romero, Francisco; Vinagre, Blas M.; Alonso Sánchez, Francisco Javier; Tejado, Ines; Font Llagunes, Josep Maria
    ASME International Design Engineering Technical Conferences
    Presentation's date: 2011-08-29
    Presentation of work at congresses

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  • Simulation and design of an active orthosis for an incomplete spinal cord injured subject

     Font Llagunes, Josep Maria; Pamies Vila, Rosa; Alonso, Javier; Lugrís, Urbano
    IUTAM Symposium on Human Body Dynamics: From Multibody Systems to Biomechanics
    Presentation's date: 2011-06-06
    Presentation of work at congresses

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    A linear approach for multiple-point impact in multibody systems  Open access

     Agullo Batlle, Joaquim; Barjau Condomines, Ana; Font Llagunes, Josep Maria
    European Congress on Computational Methods in Applied Sciences and Engineering
    Presentation's date: 2011-07-06
    Presentation of work at congresses

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    Parametric analysis of impact configurations in crutch walking  Open access

     Gholami, Farnood; Kövecses, József; Font Llagunes, Josep Maria
    European Congress on Computational Methods in Applied Sciences and Engineering
    Presentation's date: 2011-07-05
    Presentation of work at congresses

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  • A simple approach to estimate muscle forces and orthosis actuation in powered assisted walking of spinal cord-injured subjects

     Alonso, Javier; Romero, Francisco; Pamies Vila, Rosa; Lugrís, Urbano; Font Llagunes, Josep Maria
    EUROMECH Colloquium
    Presentation's date: 2011-03-10
    Presentation of work at congresses

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    Simulation of walking in individuals with incomplete spinal cord injuries (SCI) wearing an active orthosis is a challenging problem from both the analytical and the compu-tational points of view, due to the redundant nature of the simultaneous actuation of the two systems. The objective of this work is to quantify the contributions of muscles and active or-thosis to the net joint torques, so as to assist the design of active orthoses for SCI. The func-tional innervated muscles of SCI patients were modeled as Hill-type actuators, while the idle muscles were represented by stiff and dissipative elements. The orthosis was included as a set of external torques added to the ankles, knees and hips to obtain net joint torque patterns sim-ilar to those of normal unassisted walking. The muscle-orthosis redundant actuator problem was solved through a physiological static optimization approach, for which several cost func-tions and various sets of innervated muscles were compared.

  • A powered lower limb orthosis to assist the gait of incomplete spinal cord injured patients

     Font Llagunes, Josep Maria; Romero, Francisco; HosseinNia, S.H.; Alonso Sánchez, Francisco Javier; Vinagre, Blas M.; Lugrís, Urbano
    Congreso Anual de la Sociedad Española de Bioingeniería
    Presentation's date: 2011-11-16
    Presentation of work at congresses

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    This paper addresses the mechanical design and control of a new active stance-control knee-ankle-foot orthosis. The orthosis is intended to provide gait assistance for incomplete spinal cord injured patients with functional hip muscles, but partially denervated knee and ankle muscles. This device consists of a passive compliant joint that constrains ankle plantar flexion, along with a powered knee unit that prevents knee flexion during stance and controls flexion-extension during swing. For this purpose, the knee joint incorporates a controllable mechanical locking system and an electrical DC motor. Based on human walking biomechanics, a hybrid control model is proposed. This model takes into account the parameters of the orthosis and the characteristics of the gait cycle, which is divided in eight different phases. A fractional order controller is designed following decision based control techniques.

  • EMG signal smoothing using singular spectrum analysis

     Romero, Francisco; Alonso Sánchez, Francisco Javier; Cubero, J.; Font Llagunes, Josep Maria; Lugrís, Urbano; Vinagre, Blas; Hosseinia, H.
    Congreso Anual de la Sociedad Española de Bioingeniería
    Presentation's date: 2011-11-16
    Presentation of work at congresses

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  • A powered lower limb orthosis for gait assistance in incomplete spinal cord injured subjects

     Font Llagunes, Josep Maria; Arroyo, Guillermo; Serrancoli Masferrer, Gil; Romero, Francisco
    International Symposium on Applied Sciences in Biomedical and Communication Technologies
    Presentation's date: 2011-10-28
    Presentation of work at congresses

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    The paper deals with the mechanical design of a new active stance-control knee-ankle-foot orthosis (SCKAFO). The orthosis is intended to provide gait assistance for incomplete spinal cord injured patients that present functional hip muscles, but partially denervated knee and ankle muscles. It consists of a passive compliant joint that constrains ankle plantar flexion, along with a powered knee unit that prevents knee flexion during stance and controls flexion-extension during swing. For this purpose, the knee joint incorporates a controllable mechanical locking system and an electrical DC motor that actuate independently. The prototype is equipped with different sensors (plantar sensors and angular encoders) for control purposes. They are used to identify the main events defining the gait phases and to provide feedback measurements for the motor control system.

  • Robots humanoides i tecnologia per assistir la marxa humana

     Font Llagunes, Josep Maria
    Revista de tecnologia
    Date of publication: 2011-10-01
    Journal article

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  • Two approaches for the dynamic analysis of impact in biomechanical systems

     Font Llagunes, Josep Maria; Barjau Condomines, Ana; Pamies Vila, Rosa; Kövecses, József
    Symposium on Brain, Body and Machine
    Presentation's date: 2010-11-11
    Presentation of work at congresses

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    Two main approaches are used when studying impact problems involving rigid bodies: impulsive and compliant. In an impulsive approach, the impact time interval is considered to be negligible, and so the system configuration is assumed to be constant. The final mechanical state can be obtained directly from the initial one by means of algebraic equations and energy dissipation assumptions. In a compliant approach, the colliding surfaces are modeled through nonlinear springs and dampers, and the differential equations of motion are integrated to solve the forward dynamics. In this paper, the performance of the two approaches is compared in two biomechanical application examples.

  • Efectos del error en las mediciones de la fuerza de contacto pie-suelo en el análisis dinámico inverso de la marcha humana

     Pamies Vila, Rosa; Font Llagunes, Josep Maria; Cuadrado, Javier; Alonso Sánchez, Francisco Javier
    Congreso Nacional de Ingeniería Mecánica
    Presentation's date: 2010-11-03
    Presentation of work at congresses

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  • Comparison of impulsive and compliant contact models for impact analysis in biomechanical multibody systems

     Font Llagunes, Josep Maria; Kövecses, József; Pamies Vila, Rosa; Barjau Condomines, Ana
    International Conference on Multibody System Dynamics
    Presentation's date: 2010-05-25
    Presentation of work at congresses

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    Two approaches are used when studying impact problems: impulsive ones and compliant ones. In an impulsive approach, the time interval where the collision takes place is considered to be negligible, and so the system configuration is assumed to be constant. The final mechanical state of the colliding system is obtained directly from the initial one through algebraic equations and energy dissipation assumptions. In a compliant approach, the colliding surfaces are modelled through springs and dampers (usually nonlinear), and the equations of motion are integrated during the impact time interval to obtain the final state. Though both approaches have been widely used in the field of biomechanics, no comparative study can be found in the literature that could justify choosing one or another. In this paper, we present both approaches and compare them when applied to two examples related to gait problems: a passive walker and a simple model of crutch locomotion. We will show that the results are really close whenever nonsliding conditions are assumed at the impact points.

  • Influence of input data errors on the inverse dynamics analysis of human locomotion

     Pamies Vila, Rosa; Font Llagunes, Josep Maria; Cuadrado, Javier; Alonso Sánchez, Francisco Javier
    International Conference on Multibody System Dynamics
    Presentation's date: 2010-05-25
    Presentation of work at congresses

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    Inverse dynamic techniques are used in gait analysis to calculate the net joint moments that the musculoskeletal system produces during human locomotion. Errors present in the input data may affect significantly the results of the inverse dynamics problem. In this work, the influence of inaccuracies in body segment parameters (BSP) and ground reaction force measurements on the obtained results is analyzed. The uncertainties in these data are computer-generated as perturbations added to their actual values. On the one hand, the uncertainties in BSP are modelled as statistical errors using zero-mean Gaussian distributions. On the other hand, inaccurate ground reaction forces are represented adding a percentage of error to the theoretical force. Errors present in the ground reaction forces allow to estimate the uncertainty introduced to the analysis when ambiguous force plate measurements are used as input parameters. The paper presents detailed results and discussions to quantify the effects of the above errors on the inverse dynamics analysis. The several simulations carried out show that the results are more sensitive to errors in the ground contact forces –when these are used– than in the body inertial parameters.

  • Diseño de una órtesis activa para ayuda a la marcha de lesionados medulares

     Font Llagunes, Josep Maria; Arroyo, Guillermo; Alonso Sánchez, Francisco Javier; Vinagre, Blas M.
    Congreso Nacional de Ingeniería Mecánica
    Presentation's date: 2010-11-04
    Presentation of work at congresses

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  • Cálculo de esfuerzos musculares en la marcha humana mediante optimización estática-fisiológica

     Alonso Sánchez, Francisco Javier; Galán-Marín, G.; Salgado, D.R.; Pamies Vila, Rosa; Font Llagunes, Josep Maria
    Congreso Nacional de Ingeniería Mecánica
    Presentation's date: 2010-11-03
    Presentation of work at congresses

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  • Análisis dinámico de impactos en sistemas mecánicos de topología variable

     Font Llagunes, Josep Maria; Kövecses, József
    Congreso Nacional de Ingeniería Mecánica
    Presentation's date: 2010-11-05
    Presentation of work at congresses

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  • Access to the full text
    Some aspects of heel strike impact dynamics in the stability of bipedal locomotion  Open access

     Ros, Javier; Font Llagunes, Josep Maria; Kövecses, József
    Asian Conference on Multibody Dynamics
    Presentation's date: 2010-08-26
    Presentation of work at congresses

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  • Calibration for mobile robots with an invariant Jacobian

     Agullo Batlle, Joaquim; Font Llagunes, Josep Maria; Barjau Condomines, Ana
    Robotics and autonomous systems
    Date of publication: 2010-01
    Journal article

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  • Millor expedient de la promoció

     Font Llagunes, Josep Maria
    Award or recognition

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  • APLICACIÓN DE TÉCNICAS DE DINÁMICA MULTICUERPO AL DISEÑO DE ORTESIS ACTIVAS PARA LA AYUDA A LA MARCHA

     Pamies Vila, Rosa; Barjau Condomines, Ana; Agullo Batlle, Joaquim; Serrancoli Masferrer, Gil; Font Llagunes, Josep Maria
    Participation in a competitive project

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  • Dynamics and Energetics of Impacts in Crutch Walking

     Carpentier, Clément; Font Llagunes, Josep Maria; Kövecses, József
    Journal of applied biomechanics
    Date of publication: 2010-11
    Journal article

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    The impulsive dynamics associated with the impact of the crutch with the ground is an important topic of research, since this is known to be the main cause of energy loss during crutch gait. In this article, a foursegmental 2D model based on anthropometric body segment parameters is used to analyze various dynamics aspects of such impact. For this purpose, a novel formulation based on the decomposition of the tangent space of the biomechanical system to two subspaces associated with the constrained and admissible motions is developed. Detailed numerical analysis is presented to discuss the effects of body configuration and crutch length on the kinetic energy redistribution, velocity change and impulsive contact forces generated. The conclusions reached via this analysis give guidelines for optimal crutch selection or crutch-use teaching that can be applied to injured subjects. For instance, to reduce energy consumption which leads to a reduction of muscular fatigue.

  • New Method That Solves the Three-Point Resection Problem Using Straight Lines Intersection

     Font Llagunes, Josep Maria; Agullo Batlle, Joaquim
    Journal of surveying engineering (ASCE)
    Date of publication: 2009-05
    Journal article

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  • Consistent triangulation for mobile robot localization using discontinuous angular measurements

     Font Llagunes, Josep Maria; Agullo Batlle, Joaquim
    Robotics and autonomous systems
    Date of publication: 2009-09
    Journal article

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  • Dynamics of non-ideal topology transitions in multibody mechanical systems

     Font Llagunes, Josep Maria; Kövecses, József
    ASME International Design Engineering Technical Conferences
    Presentation's date: 2009-09-02
    Presentation of work at congresses

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  • Analytical and experimental studies of the dynamics of variable topology systems

     Font Llagunes, Josep Maria; Kövecses, József
    Date of publication: 2009
    Book chapter

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  • Analysis of topology changes in multibody systems

     Font Llagunes, Josep Maria; Kövecses, József
    ECCOMAS Thematic Conference Multibody Dynamics
    Presentation's date: 2009-07-01
    Presentation of work at congresses

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    Mechanical systems with time-varying topology appear frequently in natural or human-made artificial systems. The nature of topology transitions is a key characteristic in the functioning of such systems. In this paper, a concept to decouple kinematic and kinetic quantities at the time of topology transition is used. This approach is based on the use of impulsive bilateral constraints and it is a useful tool for the analysis of energy redistribution and velocity change when these constraints are suddenly established. Two examples of systems with time-varying topology are analyzed: a bipedal walking system and a dual-pantograph robotic prototype making contact with a stiff environment. Detailed numerical and experimental analysis to gain insight into the dynamics and energetics of topology transitions is presented.

  • Análisis de la marcha humana, modelos y parámetros antropométricos

     Pamies Vila, Rosa; Font Llagunes, Josep Maria
    Date: 2009-05
    Report

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  • Analytical and experimental studies of the dynamics of variable topology systems

     Font Llagunes, Josep Maria; Kövecses, József
    ASME/IFToMM International Conference on Reconfigurable Mechanisms and Robots
    Presentation's date: 2009-06-22
    Presentation of work at congresses

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    Mechanical systems with time-varying topology appear frequently in various applications. The nature of topology transition is a key characteristic in the performance of such systems. In this paper, a concept to decouple kinematic and kinetic quantities at the time of topology transition is used. This approach relies on the use of impulsive bilateral constraints and it is a useful tool for the analysis of energy redistribution and velocity change when these constraints are suddenly established. Based on this concept, two examples of systems with time-varying topology are analyzed: a bipedal walking system and a dual-pantograph robotic prototype interacting with a stiff environment. Detailed numerical and experimental analysis to gain insight into the dynamics and energetics of topology transitions is presented.

  • An Eigenvalue Problem for the Analysis of Variable Topology Mechanical Systems

     Kövecses, József; Font Llagunes, Josep Maria
    Journal of computational and nonlinear dynamics
    Date of publication: 2009-07
    Journal article

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  • Dynamics and energetics of a class of bipedal walking systems

     Font Llagunes, Josep Maria; Kövecses, József
    Mechanism and machine theory
    Date of publication: 2009-11
    Journal article

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  • Efficient Dynamic Walking: Design Strategies to Reduce Energetic Losses of a Compass Walker at Heel Strike

     Font Llagunes, Josep Maria; Kövecses, József
    Mechanics based design of structures and machines
    Date of publication: 2009-07
    Journal article

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