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Now showing items 1 - 8 of 8

  • Bond graph model of extensor mechanism of finger based on hook–string mechanism

    Vaz, Anand   Singh, Kanwalpreet   Dauphin-Tanguy, Geneviève  

    Highlights • A bond graph model of the extensor mechanism of a human finger has been developed and simulated. • Tendon topology of the Winslow’s rhombus is considered as a hook-string subsystem. • The model emulates grazing action of soft tendons along surfaces of rigid phalanges as they move. • Normal contact force as well as friction between tendon and curved bone profile is modeled. • Nonlinear behavior of tendons (4-element Hill's muscle model) and presence of cartilage in synovial joints is accounted for. Abstract Biomechanical modeling of a finger is a challenging task especially due to excursion and gliding of tendons along bone geometry, the presence of articular cartilage between mating phalanges, nonlinear viscoelastic properties, load specific change in properties of tendons and complexity of deformable tendinous network (Winslow's rhombus) of the extensor mechanism. In this work, a bond graph model of the extensor mechanism of a finger is developed. Tendons are considered as deformable strings and assumed to pass through hooks fixed at predetermined points on rigid phalanges. This enables them to remain clinging to the phalanx surface while sliding on it, and retain network topology during the movement of phalanges. Word bond graph objects (WBGOs) are developed for dynamics of phalanges, hook–string interaction, normal reaction and frictional forces, and coupling of phalanges in rotation as well as translation, etc. Friction losses and extension of tendons due to applied load are accounted for. Study of motion and tension in tendons, joint variables, location of hooks and characteristics of individual tendons can be conveniently carried out based on the bond graph model. This has been effectively demonstrated through computer simulations.
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  • [ASME ASME 2008 9th Biennial Conference on Engineering Systems Design and Analysis - Haifa, Israel (July 7–9, 2008)] Volume 2: Automotive Systems; Bioengineering and Biomedical Technology; Computational Mechanics; Controls; Dynamical Systems - A Bond Graph Model for the Actuation Mechanism of Musculo-Skeletal Joints

    Vaz, Anand   Singh, Kanwalpreet   Dauphin-Tanguy, Genevieve  

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  • A Simplified Model for Contact Mechanics of Articular Cartilage and Mating Bones Using Bond Graph

    Pathak, Arvind Kumar   Vaz, Anand  

    Articular cartilage is a soft tissue between the mating bones of a synovial joint. It prevents direct contact while facilitating load carriage and lubrication with very low friction and wear. Modeling of a synovial joint involves nonuniform geometry of mating bones, available from point cloud data, separated by cartilage. This work proposes a simplified yet efficient model of a ball dropped in a bowl lined with a cartilage layer, to emulate the contact mechanics between mating bones. Multibond graph submodels for the ball and bowl are used to represent their rigid body mechanics. The nature of the intervening cartilage layer is characterized by a nonlinear C-field. Simulation code has been written algorithmically, directly from the bond graph model. Results indicate that the proposed model holds significant promise for applications in biomechanics.
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  • An alternative model for contact interaction of mating bones with soft articular cartilage at synovial joints

    Pathak, Arvind Kumar   Vaz, Anand  

    Modeling of contact interaction at a synovial joint involves irregular mating bones separated by a soft cartilage layer, conventionally modeled using Finite Element. This work proposes an alternative simplified model, to emulate the contact mechanics between mating bones and cartilage layer. The concept of the model is explained using an example of a ball dropped in a fixed bowl lined with a cartilage layer. The surface geometries of the ball and bowl are represented as point clouds. Multibond graph submodels have been developed for the system comprising the mechanics of the soft cartilage undergoing interaction between the rigid body mechanics of the ball and the bowl. The functional role of the intervening cartilage layer is modeled by nonlinear stiffness and damping characteristics. Contribution of varying contact areas in the development of forces is considered. Numerical simulation based on the bond graph model validates that this alternative model captures the behavior of the cartilage layer effectively during contact interaction. In addition, it holds significant promise for other applications in biomechanics and robotics. (C) 2020 Elsevier Ltd. All rights reserved.
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  • Bond graph modeling of a 3-joint string-tube actuated finger prosthesis

    Mishra, Neeraj   Vaz, Anand  

    In prosthetic systems, the mechanism, sensing and actuation systems, and controls are some of the important areas which require modeling and analysis. Causal representation based on power transactions provides better understanding of interactions between these subsystems. A unified approach is therefore required to deal with the dynamics of such systems. Bond graph offers such a unified approach to the dynamics of such biomechanical systems. The concept of Word Bond Graph Objects (WBGOs) provides several advantages in modeling such large systems, including: compact representation; facilitation of understanding of energetic and causal interactions between component subsystems; algorithmic, quick and easy object oriented programming for numerical simulations. The approach had been applied earlier to develop models for a class of hand prosthesis. This work is an elaborate extension to a redundant under-actuated three-joint string-tube based finger prosthesis for a partially impaired hand. It systematically explains the dynamics of behavior of the mechanism, interactions at translational and revolute couplings between rigid phalanges, and, string-tube based joint actuation principles involved in this class of prosthesis through simulations of the bond graph models. (C) 2017 Elsevier Ltd. All rights reserved.
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  • [ASME ASME 2012 11th Biennial Conference on Engineering Systems Design and Analysis - Nantes, France (Monday 2 July 2012)] Volume 4: Advanced Manufacturing Processes; Biomedical Engineering; Multiscale Mechanics of Biological Tissues; Sciences, Engineering and Education; Multiphysics; Emerging Technologies for Inspection - Design and Development of an Instrument for Measurement of Biting Force in Human Beings

    Vaz, Anand   Jha, Mayank Shekhar   Seth, Rishi   Saxena, Ambuj  

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  • A Bond Graph Approach to the Analysis of Prosthesis for a Partially Impaired Hand

    Vaz, Anand   Hirai, Shinichi  

    A system dynamics approach, based oil bond graphs, is presented for the analysis of prosthetic devices for a partially impaired hand. The partial impairment implies that the hand has lost one or more fingers but retains the ability of its remaining natural fingers. It is shown that the existing natural joints can be used for the actuation of prosthetic finger joints and enable performance of tasks that would not have been possible otherwise. This is a challenging task as motion has to be transmitted from the remaining natural joints to the prosthetic joints. The joint axes move with respect to each other during performance of tasks and do not have any fixed relative orientation. In this work, basic concepts for the actuation of the prosthesis required,for such tasks are developed systematically. Based on these concepts, Bowden cable based joint actuation mechanisms for transmission of motion from natural Joints to corresponding prosthetic joints are presented and analyzed. The analysis of dynamics of the resulting under-actuated prosthesis with joint actuation mechanism is based oil bond graph models that are systematically developed. Using these models, system equations are derived and numerical simulations performed for the analysis. One- and two-joint actuated prototypes of the prosthesis have been presented and effectively demonstrate the proposed concepts.
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  • Development of trajectory and force controllers for 3-joint string-tube actuated finger prosthesis based on bond graph modeling

    Mishra, Neeraj   Vaz, Anand  

    The bond graph modeling and simulation of a redundant underactuated three-joint string-tube based prosthetic finger mechanism in the unlike configuration, for a class of prosthesis for a partially impaired hand, was presented for the implementation of the concept of opposition space for prehensile tasks. This work is its extension and systematically develops the structural basis and models for trajectory and force control schemes. The models emulate the abstract virtual domain of the intended task and the Central Nervous System (CNS), which provides control commands to the natural active finger joints, for the tracking control of desired position and force trajectories. The model for force control tracking has been developed systematically by utilizing the concept of causality from the bond graph model, where the motion of an infinitesimal mass is used as a trajectory input command for the generation of the desired force at the fingertip-object interface. The control models derived from their respective bond graphs do not require inverse kinematics to be worked out, and have been validated through simulations. (C) 2019 Elsevier Ltd. All rights reserved.
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