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    Design of an optimum torque actuator for augmenting lower extremity exoskeletons in biomechanical framework

    , Article 2011 IEEE International Conference on Robotics and Biomimetics, ROBIO 2011 ; 2011 , Pages 1979-1983 ; 9781457721373 (ISBN) Safavi, S ; Ghafari, A. S ; Meghdari, A ; Sharif University of Technology
    Abstract
    This research presents virtual prototyping and performance evaluation of a series elastic torque actuator developed for augmenting lower extremity exoskeletal systems employing biomechanical framework. For this purpose, experimental kinematical data of the lower extremity were collected for walking and backpack load carrying. Forward dynamics simulation of the movements under investigation is performed in a biomechanical framework consisting of a musculoskeletal model with ten degrees-of-freedom actuated by eighteen Hill-type musculotendon actuators per leg to perform the muscle functional analysis. Muscle torque analysis results employed for optimal design and selection of components in the... 

    A model for flexi-bar to evaluate intervertebral disc and muscle forces in exercises

    , Article Medical Engineering and Physics ; Volume 38, Issue 10 , 2016 , Pages 1076-1082 ; 13504533 (ISSN) Abdollahi, M ; Nikkhoo, M ; Ashouri, S ; Asghari, M ; Parnianpour, M ; Khalaf, K ; Sharif University of Technology
    Elsevier Ltd  2016
    Abstract
    This study developed and validated a lumped parameter model for the FLEXI-BAR, a popular training instrument that provides vibration stimulation. The model which can be used in conjunction with musculoskeletal-modeling software for quantitative biomechanical analyses, consists of 3 rigid segments, 2 torsional springs, and 2 torsional dashpots. Two different sets of experiments were conducted to determine the model's key parameters including the stiffness of the springs and the damping ratio of the dashpots. In the first set of experiments, the free vibration of the FLEXI-BAR with an initial displacement at its end was considered, while in the second set, forced oscillations of the bar were... 

    Biomechanical analysis of actin cytoskeleton function based on a spring network cell model

    , Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 231, Issue 7 , 2017 , Pages 1308-1323 ; 09544062 (ISSN) Ghaffari, H ; Saidi, M. S ; Firoozabadi, B ; Sharif University of Technology
    SAGE Publications Ltd  2017
    Abstract
    In this study, a new method for the simulation of the time-dependent behavior of actin cytoskeleton during cell shape change is proposed. For this purpose, a three-dimensional model of endothelial cell consisting of cell membrane, nucleus membrane, and main components of cytoskeleton, namely actin filaments, microtubules, and intermediate filaments is utilized. Actin binding proteins, which play a key role in regulating actin cytoskeleton behavior, are also simulated by using a novel technique. The actin cytoskeleton in this model is more dynamic and adoptable during cell deformation in comparison to previous models. The proposed model is subjected to compressive force between parallel micro... 

    How does the central nervous system address the kinetic redundancy in the lumbar spine? Three-dimensional isometric exertions with 18 Hill-model-based muscle fascicles at the L4-L5 level

    , Article Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine ; Volume 224, Issue 3 , 2010 , Pages 487-501 ; 09544119 (ISSN) Rashedi, E ; Khalaf, K ; Nassajian, M. R ; Nasseroleslami, B ; Parnianpour, M ; Sharif University of Technology
    2010
    Abstract
    The human motor system is organized for execution of various motor tasks in a different and flexible manner. The kinetic redundancy in the human musculoskeletal system is a significant property by which the central nervous system achieves many complementary goals. An equilibrium-based biomechanical model of isometric three-dimensional exertions of trunk muscles has been developed. Following the definition and role of the uncontrolled manifold, the kinetic redundancy concept is explored in mathematical terms. The null space of the kinetically redundant system when a certain joint moment and/or stiffness are needed is derived and discussed. The aforementioned concepts have been illustrated,... 

    Biomechanical analysis for the study of muscle contributions to support load carrying

    , Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 224, Issue 6 , 2010 , Pages 1287-1298 ; 09544062 (ISSN) Selk Ghafari, A ; Meghdari, A ; Vossoughi, G. R ; Sharif University of Technology
    Professional Engineering Publishing  2010
    Abstract
    The objective of this study was to quantify individual muscle function differences between level walking and backpack load carriage at the same speed by using a muscle-actuated forward dynamics simulation. As experimental investigations have revealed that backpack loads of up to 64 per cent of an individual's body mass have little effect on the sagittal plane gait kinema-tics, further biomechanical analyses are necessary to investigate the contributions of individual muscle coordination strategies to achieve a given motor task by mechanical power generation, absorption, and transference to each body segment. A biomechanical framework consisting of a musculoskeletal model actuated by 18...