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Title: Lower extremity joint angle tracking with wireless ultrasonic sensors during a squat exercise
Authors: Soh, Cheong Boon
Gunawan, Erry
Low, Kay-Soon
Thomas, Rijil
Qi, Yongbin
Keywords: DRNTU::Engineering::Electrical and electronic engineering
Issue Date: 2015
Source: Qi, Y., Soh, C., Gunawan, E., Low, K.-S., & Thomas, R. (2015). Lower extremity joint angle tracking with wireless ultrasonic sensors during a squat exercise. Sensors, 15(5), 9610-9627.
Series/Report no.: Sensors
Abstract: This paper presents an unrestrained measurement system based on a wearable wireless ultrasonic sensor network to track the lower extremity joint and trunk kinematics during a squat exercise with only one ultrasonic sensor attached to the trunk. The system consists of an ultrasound transmitter (mobile) and multiple receivers (anchors) whose positions are known. The proposed system measures the horizontal and vertical displacement, together with known joint constraints, to estimate joint flexion/extension angles using an inverse kinematic model based on the damped least-squares technique. The performance of the proposed ultrasonic measurement system was validated against a camera-based tracking system on eight healthy subjects performing a planar squat exercise. Joint angles estimated from the ultrasonic system showed a root mean square error (RMSE) of 2.85° ± 0.57° with the reference system. Statistical analysis indicated great agreements between these two systems with a Pearson’s correlation coefficient (PCC) value larger than 0.99 for all joint angles’ estimation. These results show that the proposed ultrasonic measurement system is useful for applications, such as rehabilitation and sports.
ISSN: 1424-8220
DOI: 10.3390/s150509610
Rights: © 2015 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license (
Fulltext Permission: open
Fulltext Availability: With Fulltext
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