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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
    Vol. 31, num. 4, p. 497-517
    DOI: 10.1007/s11044-013-9398-z
    Date of publication: 2014-04-01
    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. The total impact interval is split into phases, each corresponding to a constant set of compressed springs responsible for an elastic potential energy. For each phase, a reduced inertia matrix associated with a set of contact points, and a reduced stiffness matrix obtained from the potential energy (associated with all contact points undergoing compression) are introduced. From these matrices, a modal analysis is performed yielding an all-analytical solution within each phase. The main difference between the redundant and nonredundant cases concerns the inertia and stiffness matrices for modal analysis. While in the former case, both are related to the total set of contact points (total contact space), in the latter one they are related to two subsets: a subset of independent points for the inertia matrix (independent contact space), and the total set for the stiffness matrix. A second difference concerns the calculation of the normal impulses generated at each contact point. For the nonredundant case, they can be directly obtained from the total incremental normal velocities of the contact points through the inertia and stiffness matrices. For the redundant one, they can be obtained by adding up their incremental values at each impact phase. This requires an updating of a new effective stiffness matrix depending on the contact points undergoing compression at each phase. Four planar application cases are presented involving a single body and a multibody system colliding with a smooth ground.

  • A weighted cost function to deal with the muscle force sharing problem in injured subjects: A single case study

     Serrancoli Masferrer, Gil; Font Llagunes, Josep Maria; Barjau Condomines, Ana
    Proceedings of the Institution of Mechanical Engineers. Part K, journal of multi-body dynamics
    Vol. 228, num. 3, p. 241-11
    DOI: 10.1177/1464419314530110
    Date of publication: 2014-09-01
    Journal article

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    The human body is an over-actuated multi-body system, as each joint degree of freedom can be controlled by more than one muscle. Solving the force-sharing problem (i.e. finding out how the resultant joint torque is shared among the muscles actuating that joint) calls for an optimization process where a cost function, representing the strategy followed by the central nervous system to activate muscles, is minimized. The main contribution of the present study has been the particular formulation of that cost function for the case of the pathological gait of a single subject suffering from anterior cruciate ligament rupture. Our hypothesis was that the central nervous system does not weight equally the muscles when trying to compensate for a lower limb injury during gait (in contrast to what is the usual practice for healthy gait where all muscles are weighted equally). This hypothesis is supported by the fact that muscle activity in injured individuals differs from that of healthy subjects. Different functions were tested until we finally came out with a cost function that was consistent with experimental electromyography measurements and inverse dynamics results for a subject suffering this particular pathology.

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

     Pamies Vila, Rosa; Font Llagunes, Josep Maria; Lugrís Armesto, Urbano; Cuadrado Aranda, Javier
    Mechanism and machine theory
    Vol. 75, p. 107-116
    DOI: 10.1016/j.mechmachtheory.2014.01.010
    Date of publication: 2014-05-01
    Journal article

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    A new parameter identification method for a three-dimensional foot-ground contact model is presented. The model is used to reproduce the relationship between the contact forces and the relative foot-ground displacements and velocities. The parameters of the contact model are estimated using the optimization method known as covariance matrix adaptation evolution strategy. An extended Kalman filter is implemented as a controller to compute a forward dynamic analysis of the foot motion using body segment parameters and the ankle joint wrench as input data. The aim of this work is to adjust the position and size of the contact elements (spheres) and the model parameters in order to obtain both, a predicted motion provided by forward dynamics as faithful as possible to the captured motion and a resultant foot-ground wrench (obtained through the foot-ground contact model) as close as possible to the measured foot-ground reactions. The results show that the obtained motion is really similar to the captured one and, moreover, the vertical force and the moments in the horizontal plane are in agreement with the experimental mesurments. However, the bristle friction model used for tangential forces provides lower level of agreement with the experimental data. (C) 2014 Elsevier Ltd. All rights reserved.

  • 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
    Vol. 17, num. 10, p. 1144-1156
    DOI: 10.1080/10255842.2012.738199
    Date of publication: 2014
    Journal article

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    Cervical spinal cord injury and acquired brain injury commonly imply a reduction in the upper extremity function which complicates, or even constrains, the performance of basic activities of daily living. Neurological rehabilitation in specialised hospitals is a common treatment for patients with neurological disorders. This study presents a practical methodology for the objective and quantitative evaluation of the upper extremity motion during an activity of daily living of those subjects. A new biomechanical model (with 10 rigid segments and 20 degrees of freedom) was defined to carry out kinematic, dynamic and energetic analyses of the upper extremity motion during a reaching task through data acquired by an optoelectronic system. In contrast to previous upper extremity models, the present model includes the analysis of the grasp motion, which is considered as crucial by clinicians. In addition to the model, we describe a processing and analysis methodology designed to present relevant summaries of biomechanical information to rehabilitation specialists. As an application case, the method was tested on a total of four subjects: three healthy subjects and one pathological subject suffering from cervical spinal cord injury. The dedicated kinematic, dynamic and energetic analyses for this particular case are presented. The resulting set of biomechanical measurements provides valuable information for clinicians to achieve a thorough understanding of the upper extremity motion, and allows comparing the motion of healthy and pathological cases.

  • Analysis of the body stability using biomechanical measurements. Comparison of two shoe models

     Font Llagunes, Josep Maria; Serrancoli Masferrer, Gil
    Date: 2014-01-23
    Report

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

     Lugrís Armesto, Urbano; Carlín, Jairo; Pamies Vila, Rosa; Font Llagunes, Josep Maria; Cuadrado Aranda, Javier
    Multibody system dynamics
    Vol. 30, num. 3, p. 247-263
    DOI: 10.1007/s11044-013-9363-x
    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.

  • Determinació de les variables crítiques que defineixen el confort en un calçat

     Barjau Condomines, Ana; Font Llagunes, Josep Maria; Pamies Vila, Rosa; Serrancoli Masferrer, Gil
    Date: 2013-07-15
    Report

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  • Diseño de una ortesis activa innovadora para la marcha de lesionados medulares incompletos mediante métodos de análisis y predicción de movimiento y modelos musculoesqueléticos complejos

     Pamies Vila, Rosa; Font Llagunes, Josep Maria; Agullo Batlle, Joaquim; Barjau Condomines, Ana; Serrancoli Masferrer, Gil
    Competitive project

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  • Human motion analysis of a healthy subject wearing active orthoses

     Romero Sánchez, Francisco; Pamies Vila, Rosa; Lugrís Armesto, Urbano; Alonso, Francisco Javier; Font Llagunes, Josep Maria; Cuadrado Aranda, Javier
    Reunión del Capítulo Español de la Sociedad Europea de Biomecánica
    p. 1
    Presentation's date: 2013-10-24
    Presentation of work at congresses

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    The use of active orthoses has become a powerful tool in medical rehabilitation roper operation depends on the coordination of different tasks, such as mechanical and control ler design. Since these devices are highly customized to the patient, simulation can help to streamline their development. The objective of this work is to present the progress of an ongoing national project carried out by three Spanish universities (UEx, UPC and UDC), aimed at building an innovative prototype of active orthosis for gait assistance and to develop a computer simulation tool to virtually test this type of devices.

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

     Cuadrado Aranda, Javier; Lugrís Armesto, Urbano; Pamies Vila, Rosa; Font Llagunes, Josep Maria
    International and National Conference on Machines and Mechanisms
    p. 1-8
    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.

    Abstract—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.

  • 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
    p. 1-10
    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.

  • Optimization problem formulation for predicting knee muscle and contact forces during gait

     Serrancoli Masferrer, Gil; Walter, Jonathan P.; Kinney, Allison L.; Fregly, Benjamin J.; Font Llagunes, Josep Maria
    International Symposium on Computer Simulation in Biomechanics
    p. 70-71
    Presentation's date: 2013-08-03
    Presentation of work at congresses

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  • Gait analysis of incomplete spinal cord injured subjects walking with an active orthosis and crutches

     Font Llagunes, Josep Maria; Romero Sánchez, Francisco; Lugrís Armesto, Urbano; Pamies Vila, Rosa; Alonso Sánchez, Francisco Javier; Cuadrado Aranda, Javier
    Congress on Numerical Methods in Engineering
    p. 1
    Presentation's date: 2013-06-26
    Presentation of work at congresses

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  • Configuration-dependent performance indicators for the analysis of foot impact in running gait

     Font Llagunes, Josep Maria; Pamies Vila, Rosa; Kövecses, József
    ECCOMAS Thematic Conference
    p. 31-32
    Presentation's date: 2013-07-02
    Presentation of work at congresses

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  • Application of a mixed displacement-pressure finite element formulation based on the absolute nodal coordinate framework to biomechanical problems

     Altarriba, Elias; Font Llagunes, Josep Maria; Mikkola, Aki M.
    Congress on Numerical Methods in Engineering
    p. 1
    Presentation's date: 2013-06-25
    Presentation of work at congresses

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  • Formulation to predict lower limb muscle forces during gait

     Serrancoli Masferrer, Gil; Walter, Jonathan P.; Kinney, Allison L.; Barjau Condomines, Ana; Fregly, Benjamin J.; Font Llagunes, Josep Maria
    Reunión del Capítulo Español de la Sociedad Europea de Biomecánica
    p. 1
    Presentation's date: 2013-10-24
    Presentation of work at congresses

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    The human body has more muscles than Degrees of Freedom (DoF), and that leads to indeterminacy in the muscle force calculation. This study proposes the formulation of an optimization problem to estimate the lower-limb muscle forces during a gait cycle of a patient wearing an instrumented knee prosthesis. The originality of that formulation consists of simulating muscle excitations in a physiological way while muscle parameters are calibrated. Two approaches have been considered. In Approach A, measured contact forces are applied to the model and all inverse dynamics loads are matched in order to get a physiological calibration of muscle parameters. In Approach B, only the inverse dynamics loads not affected by the knee contact loads are matched. With that approach, contact forces can be predicted and validated by comparison with the experimental ones. Approach B is a test of the optimization method and it can be used for cases where no knee contact forces are available

  • Design of an active stance-control knee-ankle-foot orthosis to assist the gait of incomplete spinal cord-injured subjects

     Font Llagunes, Josep Maria; Pamies Vila, Rosa; Romero Sánchez, Francisco; Alonso Sánchez, Javier; Lugrís Armesto, Urbano; Cuadrado Aranda, Javier
    Rehabilitation Robotics - Clinical Evidence and Technical Development
    p. 1
    Presentation's date: 2013-04-08
    Presentation of work at congresses

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  • On the use of multibody dynamics techniques for the inverse and forward dynamic analysis of human gait

     Pamies Vila, Rosa; Font Llagunes, Josep Maria; Lugrís Armesto, Urbano; Cuadrado Aranda, Javier
    Congress on Numerical Methods in Engineering
    p. 1
    Presentation's date: 2013-06-26
    Presentation of work at congresses

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  • Determination of the strategy for solving the muscle force sharing problem in patients suffering ACL rupture

     Serrancoli Masferrer, Gil; Font Llagunes, Josep Maria; Barjau Condomines, Ana
    Congress on Numerical Methods in Engineering
    p. 1
    Presentation's date: 2013-06-26
    Presentation of work at congresses

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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
    Vol. 28, num. 3, p. 257-282
    DOI: 10.1007/s11044-011-9300-9
    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.

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

     Alonso Sánchez, Javier; Romero Sánchez, Francisco; Pamies Vila, Rosa; Lugrís Armesto, Urbano; Font Llagunes, Josep Maria
    Multibody system dynamics
    Vol. 28, num. 1-2, p. 109-124
    DOI: 10.1007/s11044-011-9284-5
    Date of publication: 2012-08-01
    Journal article

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

     Pamies Vila, Rosa; Font Llagunes, Josep Maria; Cuadrado Aranda, Javier; Alonso Sánchez, Francisco Javier
    Mechanism and machine theory
    Vol. 58, p. 153-164
    DOI: 10.1016/j.mechmachtheory.2012.07.010
    Date of publication: 2012-12-01
    Journal article

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

     Pamies Vila, Rosa
    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.

  • 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 Armesto, Urbano; Cuadrado Aranda, Javier
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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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  • Dynamic analysis of foot models for human locomotion

     Gholami, Farnood; Font Llagunes, Josep Maria; Kövecses, József
    Joint International Conference on Multibody System Dynamics
    p. 64-65
    Presentation's date: 2012-06-01
    Presentation of work at congresses

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  • On the force sharing problem in patients suffering joint pain

     Serrancoli Masferrer, Gil; Font Llagunes, Josep Maria; Barjau Condomines, Ana
    Congress of the European Society of Biomechanics
    Presentation's date: 2012-07-03
    Presentation of work at congresses

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  • Two approaches to estimate foot-ground contact model parameters using optimization techniques

     Pamies Vila, Rosa; Font Llagunes, Josep Maria; Lugrís Armesto, Urbano; Cuadrado Aranda, Javier
    Joint International Conference on Multibody System Dynamics
    p. 90-91
    Presentation's date: 2012-06-01
    Presentation of work at congresses

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  • Design of an innovative gait-assistive active orthosis for incomplete spinal cord injured subjects based on human motion analysis

     Romero Sánchez, Francisco; Pamies Vila, Rosa; Lugrís Armesto, Urbano; Alonso Sánchez, Francisco Javier; Font Llagunes, Josep Maria; Cuadrado Aranda, Javier
    Reunión del Capítulo Español de la Sociedad Europea de Biomecánica
    p. 1
    Presentation's date: 2012-10-25
    Presentation of work at congresses

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

     Cuadrado Aranda, Javier; Lugrís Armesto, Urbano; Alonso Sánchez, Francisco Javier; Font Llagunes, Josep Maria
    Congreso Nacional de Ingeniería Mecánica
    p. 1-8
    Presentation's date: 2012-11-14
    Presentation of work at congresses

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  • Muscle forces adaptation in assisted walking using a powered SCKAFO

     Romero Sánchez, Francisco; Alonso Sánchez, Javier; HosseinNia, S. H.; Vinagre, Blas; Font Llagunes, Josep Maria
    Congress of the European Society of Biomechanics
    DOI: 10.1016/S0021-9290(12)70522-5
    Presentation's date: 2012-07-03
    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
    p. 105-106
    Presentation's date: 2012-05-30
    Presentation of work at congresses

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  • Dynamic analysis of walking with a powered stance-control knee-ankle-foot orthosis

     Font Llagunes, Josep Maria; Pamies Vila, Rosa; Alonso Sánchez, Javier; Cuadrado Aranda, Javier
    Congress of the European Society of Biomechanics
    DOI: 10.1016/S0021-9290(12)70515-8
    Presentation's date: 2012-07-03
    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 Armesto, Urbano; Cuadrado Aranda, Javier
    Congreso Nacional de Ingeniería Mecánica
    p. 1-8
    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

  • Clinical evaluation of the upper extremity motion in subjects with neurological disorders

     Lobo-Prat, Joan; Font Llagunes, Josep Maria; Medina-Casanovas, Josep; Angulo-Barroso, Rosa M.
    Congress of the European Society of Biomechanics
    DOI: 10.1016/S0021-9290(12)70292-0
    Presentation's date: 2012-07-02
    Presentation of work at congresses

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  • Robots humanoides i tecnologia per assistir la marxa humana

     Font Llagunes, Josep Maria
    Revista de tecnologia
    num. 4, p. 29-38
    DOI: 10.2436/20.2004.01.10
    Date of publication: 2011-10-01
    Journal article

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  • Application of multibody dynamics techniques to active orthosis design for gait assistance

     Pamies Vila, Rosa; Romero Sánchez, Francisco; Cuadrado Aranda, Javier; Lugrís Armesto, Urbano; Font Llagunes, Josep Maria; Alonso Sánchez, Francisco Javier
    Reunión del Capítulo Nacional Español de la Sociedad Europea de Biomecánica
    p. 40
    Presentation's date: 2011-11-10
    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 Sánchez, Francisco
    International Symposium on Applied Sciences in Biomedical and Communication Technologies
    p. 1-4
    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.

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

     Alonso Sánchez, Javier; Romero Sánchez, Francisco; Pamies Vila, Rosa; Lugrís Armesto, Urbano; Font Llagunes, Josep Maria
    EUROMECH Colloquium
    p. 1-16
    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.

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

     HosseinNia, S. Hassan; Romero Sánchez, Francisco; Vinagre, Blas M.; Alonso Sánchez, Francisco Javier; Tejado, Ines; Font Llagunes, Josep Maria
    ASME International Design Engineering Technical Conferences
    p. 1-9
    Presentation's date: 2011-08-29
    Presentation of work at congresses

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

     Font Llagunes, Josep Maria; Romero Sánchez, Francisco; HosseinNia, S.H.; Alonso Sánchez, Francisco Javier; Vinagre, Blas M.; Lugrís Armesto, Urbano
    Congreso Anual de la Sociedad Española de Bioingeniería
    p. 129-132
    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 Sánchez, Francisco; Alonso Sánchez, Francisco Javier; Cubero, J.; Font Llagunes, Josep Maria; Lugrís Armesto, Urbano; Vinagre, Blas; Hosseinia, H.
    Congreso Anual de la Sociedad Española de Bioingeniería
    p. 81-84
    Presentation's date: 2011-11-16
    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 Sánchez, Javier; Lugrís Armesto, Urbano
    IUTAM Symposium on Human Body Dynamics: From Multibody Systems to Biomechanics
    p. 68-81
    DOI: 10.1016/j.piutam.2011.04.007
    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
    p. 1-12
    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
    p. 1-7
    Presentation's date: 2011-07-05
    Presentation of work at congresses

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  • Dynamics and Energetics of Impacts in Crutch Walking

     Carpentier, Clément; Font Llagunes, Josep Maria; Kövecses, József
    Journal of applied biomechanics
    Vol. 26, num. 4, p. 473-483
    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.

  • Calibration for mobile robots with an invariant Jacobian

     Agullo Batlle, Joaquim; Font Llagunes, Josep Maria; Barjau Condomines, Ana
    Robotics and autonomous systems
    Vol. 58, num. 1, p. 10-15
    DOI: 10.1016/j.robot.2009.09.002
    Date of publication: 2010-01
    Journal article

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  • Modelització i anàlisi dinàmica de la marxa humana

     Pamies Vila, Rosa; Font Llagunes, Josep Maria
    Date: 2010-06-01
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