Development of a fully flexure-based prosthetic hand

Luis Alberto Garcia Rodriguez

    Research output: ThesisPd Eng Thesis

    279 Downloads (Pure)

    Abstract

    Most people that require assistive devices such as prosthetic hands are located in developing countries. Two basic requirements for prosthetic hands have been identified: affordability; and, acceptance of the device. Additive manufacturing offers the opportunity for local, low-cost manufacturing with the possibility to achieve acquisition cost below 3,000 USD. Moreover, the acceptance of the device is related to its weight, its cosmetic appearance and its capability to perform a power medium wrap, which is the most common grasp during activities of daily living.
    Current flexure-based hands lack support stiffness through out large range of deflections and power grasping capacity while performing power grasps, particularly at the metacarpophalangeal joint.
    The focus of this study is to design a fully flexure-based hand which can perform successfully a power medium wrap. Special attention is given to the metacarpophalangeal joint since it presents the biggest challenge.
    The concept of the fully flexure-based hand is studied in detail. Needs of the users are identified and are translated to requirements. The technical performance metrics
    are associated with: acquisition costs, power grasping force, and capability to grasp the most common objects. These metrics are addressed at the component level.
    The presented flexure mechanisms follow a bottom-up approach from the component level to the fully flexure-based hand system. A monolithic, 3D-printed, fully
    flexure-based hand has potential to scale-up production of custom devices by minimizing assembly, which ultimately benefits the total acquisition costs of the assistive
    device.
    At this component level, a methodology is developed to determine the optimal flexure layout and the corresponding design parameters for an anthropomorphic metacarpophalangeal joint. This methodology uses an implementation of the Nelder-Mead algorithm to optimize the hinges towards maximum grasping force. In total, five flexure layouts are investigated: the Leafspring, the Solid-Flexure Cross Hinge, the Three-Flexure Cross Hinge, the Hole Cross Hinge, and the Angled Three-Flexure Cross
    Hinge.
    In addition, an overload-protection mechanism is proposed to mitigate the effects of low support stiffness in flexure-based fingers at larger ranges of motion.
    Original languageEnglish
    Awarding Institution
    • University of Twente
    Supervisors/Advisors
    • Brouwer, Dannis Michel, Supervisor
    Award date22 Jun 2018
    Place of PublicationEnschede
    Publisher
    Print ISBNs978-90-365-4580-8
    DOIs
    Publication statusPublished - 22 Jun 2018

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