Gravity Balancing Flexure Springs for an Assistive Elbow Orthosis

Martin Tschiersky*, Edsko E.G. Hekman, Dannis Michel Brouwer, Just L Herder

*Corresponding author for this work

    Research output: Contribution to journalArticleAcademicpeer-review

    22 Citations (Scopus)
    122 Downloads (Pure)


    In this paper, we propose a flexure spring based gravity compensation device which provides assistance to lift the forearm. Three different spring designs are obtained and evaluated. The synthesis method to obtain these is explained in detail and an experimental evaluation validates the desired gravity balancing properties. It is found that in comparison to a flexure spring with constant thickness, a variable thickness distribution along the spring leads to a drastic reduction of its width, which amounts to 81 % in the presented case, and offers an energy to weight ratio that is 94 % higher. Employing a nested spring design further increases the storable elastic energy of the variable thickness design by 145 % through utilization of the otherwise unused space within the original spring envelope. A proof-of-concept prototype is built to illustrate a practical implementation. The presented synthesis method provides a tool to obtain gravity balancing flexure springs that offer a promising solution for the design of assistive devices which aim to be both wearable and inconspicuous.
    Original languageEnglish
    Article number8770277
    Pages (from-to)177-188
    Number of pages12
    JournalIEEE Transactions on Medical Robotics and Bionics
    Issue number3
    Publication statusPublished - Aug 2019


    • arm support
    • assistive orthosis
    • flexure spring
    • Gravity balancing
    • wearable device


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