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Sensors 2017, 17(4), 713;

Model-Based Estimation of Ankle Joint Stiffness

Philips Chair for Medical Information Technology, RWTH Aachen University, Pauwelsstrasse 20, 52074 Aachen, Germany
Author to whom correspondence should be addressed.
Received: 16 January 2017 / Revised: 22 March 2017 / Accepted: 23 March 2017 / Published: 29 March 2017
(This article belongs to the Special Issue Wearable Biomedical Sensors)
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We address the estimation of biomechanical parameters with wearable measurement technologies. In particular, we focus on the estimation of sagittal plane ankle joint stiffness in dorsiflexion/plantar flexion. For this estimation, a novel nonlinear biomechanical model of the lower leg was formulated that is driven by electromyographic signals. The model incorporates a two-dimensional kinematic description in the sagittal plane for the calculation of muscle lever arms and torques. To reduce estimation errors due to model uncertainties, a filtering algorithm is necessary that employs segmental orientation sensor measurements. Because of the model’s inherent nonlinearities and nonsmooth dynamics, a square-root cubature Kalman filter was developed. The performance of the novel estimation approach was evaluated in silico and in an experimental procedure. The experimental study was conducted with body-worn sensors and a test-bench that was specifically designed to obtain reference angle and torque measurements for a single joint. Results show that the filter is able to reconstruct joint angle positions, velocities and torque, as well as, joint stiffness during experimental test bench movements. View Full-Text
Keywords: joint stiffness estimation; body-worn sensors; magnetic, angular rate and gravity sensors; BSN joint stiffness estimation; body-worn sensors; magnetic, angular rate and gravity sensors; BSN

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Misgeld, B.J.E.; Zhang, T.; Lüken, M.J.; Leonhardt, S. Model-Based Estimation of Ankle Joint Stiffness. Sensors 2017, 17, 713.

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