DocumentCode :
139581
Title :
Identification of ankle joint stiffness during passive movements — A subspace linear parameter varying approach
Author :
Tehrani, Ehsan Sobhani ; Jalaleddini, Kian ; Kearney, Robert E.
Author_Institution :
Dept. of Biomed. Eng., McGill Univ., Montréal, QC, Canada
fYear :
2014
fDate :
26-30 Aug. 2014
Firstpage :
1603
Lastpage :
1606
Abstract :
This paper describes a novel method for the identification of time-varying ankle joint dynamic stiffness during large passive movements. The method estimates a linear parameter varying parallel-cascade (LPV-PC) model of joint stiffness consisting of two pathways: (a) an LPV impulse response function (IRF) for intrinsic mechanics and (b) an LPV Hammerstein cascade with time-varying static nonlinearity and a time-invariant linear dynamics for the reflex pathway. A subspace identification technique is used to estimate a statespace representation of the reflex stiffness dynamics. Then, an orthogonal projection decouples intrinsic from reflex response and subsequently identifies an LPV-IRF model of intrinsic stiffness. Finally, an LPV model of the reflex static nonlinearity is estimated using an iterative, separable least squares method. The LPV method was validated using experimental data from two healthy subjects where the ankle was moved passively by an actuator through its range of motion first without and then with perturbations. The identification results demonstrated that (a) the dynamic response of the intrinsic pathway changes systematically with joint position; and (b) the static nonlinearity of the reflex pathway resembles a half-wave rectifier whose threshold decreases and gain increases as ankle is moved to dorsiflexed position.
Keywords :
biomechanics; biomedical measurement; bone; elastic constants; least squares approximations; state-space methods; LPV Hammerstein cascade; LPV impulse response function; LPV-PC model; ankle joint stiffness identification; dorsiflexed position; half-wave rectifier; intrinsic mechanics; linear parameter varying parallel-cascade model; passive movements; reflex pathway; reflex static nonlinearity; reflex stiffness dynamics; separable least squares method; state-space representation; subspace identification technique; subspace linear parameter varying approach; time-invariant linear dynamics; time-varying ankle joint dynamic stiffness; Biological system modeling; Electromyography; Joints; TV; Torque; Trajectory; Vectors;
fLanguage :
English
Publisher :
ieee
Conference_Titel :
Engineering in Medicine and Biology Society (EMBC), 2014 36th Annual International Conference of the IEEE
Conference_Location :
Chicago, IL
ISSN :
1557-170X
Type :
conf
DOI :
10.1109/EMBC.2014.6943911
Filename :
6943911
Link To Document :
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