TY - JOUR
T1 - Model-based estimation of knee stiffness
AU - Pfeifer, Serge
AU - Vallery, Heike
AU - Hardegger, Michael
AU - Riener, Robert
AU - Perreault, Eric J.
N1 - Funding Information:
Manuscript received January 11, 2012; revised April 3, 2012; June 18, 2012; accepted June 30, 2012. Date of publication July 11, 2012; date of current version August 16, 2012. This work was supported by the ETH Research Grant ETHIIRA, the Gottfried und Julia Bangerter-Rhyner Stiftung and the Swiss National Science Foundation through the National Centre of Competence in Research Robotics. The work of the author E. J. Perreault was supported by the NSF Program in Cyber-Physical Systems under Award 0939963. Asterisk indicates corresponding author.
PY - 2012
Y1 - 2012
N2 - During natural locomotion, the stiffness of the human knee is modulated continuously and subconsciously according to the demands of activity and terrain. Given modern actuator technology, powered transfemoral prostheses could theoretically provide a similar degree of sophistication and function. However, experimentally quantifying knee stiffness modulation during natural gait is challenging. Alternatively, joint stiffness could be estimated in a less disruptive manner using electromyography (EMG) combined with kinetic and kinematic measurements to estimate muscle force, together with models that relate muscle force to stiffness. Here we present the first step in that process, where we develop such an approach and evaluate it in isometric conditions, where experimental measurements are more feasible. Our EMG-guided modeling approach allows us to consider conditions with antagonistic muscle activation, a phenomenon commonly observed in physiological gait. Our validation shows that model-based estimates of knee joint stiffness coincide well with experimental data obtained using conventional perturbation techniques. We conclude that knee stiffness can be accurately estimated in isometric conditions without applying perturbations, which presents an important step toward our ultimate goal of quantifying knee stiffness during gait.
AB - During natural locomotion, the stiffness of the human knee is modulated continuously and subconsciously according to the demands of activity and terrain. Given modern actuator technology, powered transfemoral prostheses could theoretically provide a similar degree of sophistication and function. However, experimentally quantifying knee stiffness modulation during natural gait is challenging. Alternatively, joint stiffness could be estimated in a less disruptive manner using electromyography (EMG) combined with kinetic and kinematic measurements to estimate muscle force, together with models that relate muscle force to stiffness. Here we present the first step in that process, where we develop such an approach and evaluate it in isometric conditions, where experimental measurements are more feasible. Our EMG-guided modeling approach allows us to consider conditions with antagonistic muscle activation, a phenomenon commonly observed in physiological gait. Our validation shows that model-based estimates of knee joint stiffness coincide well with experimental data obtained using conventional perturbation techniques. We conclude that knee stiffness can be accurately estimated in isometric conditions without applying perturbations, which presents an important step toward our ultimate goal of quantifying knee stiffness during gait.
KW - Electromyography (EMG)
KW - knee joint impedance
KW - knee prosthetics
KW - load sharing
KW - muscle force estimation
KW - muscle short-range stiffness
KW - musculoskeletal modeling
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U2 - 10.1109/TBME.2012.2207895
DO - 10.1109/TBME.2012.2207895
M3 - Article
C2 - 22801482
AN - SCOPUS:84865489990
VL - 59
SP - 2604
EP - 2612
JO - IEEE Transactions on Biomedical Engineering
JF - IEEE Transactions on Biomedical Engineering
SN - 0018-9294
IS - 9
M1 - 6237517
ER -