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

Alejandro Moya Esteban, Ronald C. Van 'T Veld, Christopher P. Cop, Guillaume Durandau, Massimo Sartori, Alfred C. Schouten

Research output: Chapter in Book/Conference proceedings/Edited volumeConference contributionScientificpeer-review

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 publicationProceedings of the 41st Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC 2019)
Place of PublicationPiscataway, NJ, USA
PublisherIEEE
Pages2119-2122
ISBN (Electronic)978-1-5386-1311-5
DOIs
Publication statusPublished - 2019
EventEMBC 2019: 41st Annual International Conference of the IEEE Engineering in Medicine and Biology Society - Berlin, Germany
Duration: 23 Jul 201927 Jul 2019
Conference number: 41st

Conference

ConferenceEMBC 2019
CountryGermany
CityBerlin
Period23/07/1927/07/19

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