Estimation of Time-Varying Ankle Joint Stiffness Under Dynamic Conditions via System Identification Techniques

Alejandro Moya Esteban*, R.C. van 't Veld, Christopher Pablo Cop, G.V. Durandau, M. Sartori, A.C. Schouten

*Corresponding author for this work

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

    1 Citation (Scopus)
    3 Downloads (Pure)

    Abstract

    An important goal in the design of next-generation exoskeletons and limb prostheses is to replicate human limb dynamics. Joint impedance determines the dynamic relation between joint displacement and torque. Joint stiffness is the position-dependent component of joint impedance and is key in postural control and movement. However, the mechanisms to modulate joint stiffness are not fully understood yet. The goal of this study is to conduct a systematic analysis on how humans modulate ankle stiffness. Time-varying stiffness was estimated for six healthy subjects under isometric, as well as quick and slow dynamic conditions via system identification techniques; specifically, an ensemble-based algorithm using short segments of ankle torque and position recordings. Our results show that stiffness had the lowest magnitude under quick dynamic conditions. Under isometric conditions, with fixed position and varying muscle activity, stiffness exhibited a higher magnitude. Finally, under slow dynamic conditions, stiffness was found to be the highest. Our results highlight, for the first time, the variability in stiffness modulation strategies across conditions, especially across movement velocity.
    Original languageEnglish
    Title of host publication2019 41st Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC)
    PublisherIEEE
    Pages2119-2122
    Number of pages4
    ISBN (Electronic)978-1-5386-1311-5
    DOIs
    Publication statusPublished - 7 Oct 2019
    Event41st International Engineering in Medicine and Biology Conference, EMBC 2019: Biomedical Engineering Ranging from Wellness to Intensive Care Medicine - CityCube Berlin, Berlin, Germany
    Duration: 23 Jul 201927 Jul 2019
    Conference number: 41
    https://embc.embs.org/2019/

    Conference

    Conference41st International Engineering in Medicine and Biology Conference, EMBC 2019
    Abbreviated titleEMBC
    CountryGermany
    CityBerlin
    Period23/07/1927/07/19
    Internet address

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