Spring uses in exoskeleton actuation design

Shiqian Wang, Wietse van Dijk, Herman van der Kooij

    Research output: Chapter in Book/Report/Conference proceedingConference contributionAcademicpeer-review

    84 Citations (Scopus)
    4 Downloads (Pure)


    An exoskeleton has to be lightweight, compliant, yet powerful to fulfill the demanding task of walking. This imposes a great challenge for the actuator design. Electric motors, by far the most common actuator in robotic, orthotic, and prosthetic devices, cannot provide sufficiently high peak and average power and force/torque output, and they normally require high-ratio, heavy reducer to produce the speeds and high torques needed for human locomotion. Studies on the human muscle-tendon system have shown that muscles (including tendons and ligaments) function as a spring, and by storing energy and releasing it at a proper moment, locomotion becomes more energy efficient. Inspired by the muscle behavior, we propose a novel actuation strategy for exoskeleton design. In this paper, the collected gait data are analyzed to identify the spring property of the human muscle-tendon system. Theoretical optimization results show that adding parallel springs can reduce the peak torque by 66%, 53%, and 48% for hip flexion/extension (F/E), hip abduction/adduction (A/A), and ankle dorsi/plantar flexion (D/PF), respectively, and the rms power by 50%, 45%, and 61%, respectively. Adding a series spring (forming a Series Elastic Actuator, SEA) reduces the peak power by 79% for ankle D/PF, and by 60% for hip A/A. A SEA does not reduce the peak power demand at other joints. The optimization approach can be used for designing other wearable robots as well.
    Original languageEnglish
    Title of host publication2011 IEEE International Conference on Rehabilitation Robotics
    Place of PublicationPiscataway, NJ
    Number of pages6
    ISBN (Electronic)978-1-4244-9862-8
    ISBN (Print)978-1-4244-9863-5
    Publication statusPublished - 29 Jun 2011
    EventIEEE 12th International Conference on Rehabilitation Robotics, ICORR 2011 - ETH Zurich , Zürich, Switzerland
    Duration: 29 Jun 20111 Jul 2011
    Conference number: 12

    Publication series

    NameIEEE International Conference on Rehabilitation Robotics
    ISSN (Print)1945-7898
    ISSN (Electronic)1945-7901


    ConferenceIEEE 12th International Conference on Rehabilitation Robotics, ICORR 2011
    Abbreviated titleICORR
    Internet address


    • Exoskeleton
    • Wearable robots
    • PEA
    • SEA
    • Spring
    • Actuation


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