Lower Extremity Joint Angle Tracking with Wireless Ultrasonic Sensors during a Squat Exercise.
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.
School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore. qiyo0001@e.ntu.edu.sg.
Yongbin
Y
Qi
School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore. ecbsoh@ntu.edu.sg.
Cheong Boon
CB
Soh
School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore. egunawan@ntu.edu.sg.
Erry
E
Gunawan
School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore. ekslow@ntu.edu.sg.
Kay-Soon
KS
Low
School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore. rijil001@e.ntu.edu.sg.
Rijil
R
Thomas
D001696:Biomechanical Phenomena; D015374:Biosensing Techniques / Q000379:methods*; D015444:Exercise / Q000502:physiology; D006801:Humans; D007596:Joints / Q000502:physiology; D035002:Lower Extremity / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology; D014465:Ultrasonics / Q000379:methods*