Estimation of time-varying ankle joint stiffness under dynamic conditions via system identification techniques

Estimation of time-varying ankle joint stiffness under dynamic conditions via system identification techniques

Esteban, Alejandro Moya (University of Twente)
Van 'T Veld, Ronald C. (University of Twente)
Cop, Christopher P. (University of Twente)
Durandau, Guillaume (University of Twente)
Sartori, Massimo (University of Twente)
Schouten, A.C. (TU Delft Biomechatronics & Human-Machine Control; University of Twente)

2019

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.

http://resolver.tudelft.nl/uuid:686c3dae-5707-4639-beda-e64f9c7fce0d

https://doi.org/10.1109/EMBC.2019.8856423

IEEE, Piscataway, NJ, USA

2020-04-07

978-1-5386-1311-5

Proceedings of the 41st Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC 2019)

EMBC 2019, 2019-07-23 → 2019-07-27, Berlin, Germany

Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.

Institutional Repository

conference paper

© 2019 Alejandro Moya Esteban, Ronald C. Van 'T Veld, Christopher P. Cop, Guillaume Durandau, Massimo Sartori, A.C. Schouten