Browsing by Author "Hsieh, Hong-Jung"

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A method for estimating subject-specific body segment inertial parameters in human movement analysis
(2011-04-01)
Chen, Sheng-Chang
;
Hsieh, Hong-Jung
;
Lu, Tung-Wu
;
Tseng, Ching-Huan
;
機械工程學系
An optimization-based, non-invasive, radiation-free method was developed for estimating subject-specific body segment inertial properties (BSIPs) using a motion capture system and two forceplates. The method works with accurate descriptions of the geometry of the body segments, subject-specific center of pressure (COP) and kinematic data captured during stationary standing, and an optimization procedure. Twelve healthy subjects performed stationary standing in different postures, level walking and squatting while kinematic and forceplate data were measured. The performance of the current method was compared to three commonly used predictive methods in terms of the errors of the calculated ground reaction force, COP and joint moments using the corresponding predicted BSIPs. The current method was found to be capable of producing estimates of subject-specific BSIPs that predicted accurately the important variables in human motion analysis during static and dynamic activities. With the differences in the BSIPs from the current method, the mean COP errors were less than 5 mm during stationary standing postures, while those from the existing comparative methods ranged from 11 to 25 mm. During dynamic activities, the existing methods gave COP errors three times as large as the proposed method, with up to 2.5 times RMSE in joint moments during walking. Being non-invasive and using standard motion laboratory equipment, the current method will be useful for routine clinical gait analysis and relevant clinical applications, particularly in patient populations that are not targeted by the existing predictive methods. (C) 2011 Elsevier B.V. All rights reserved.
A new device for in situ static and dynamic calibration of force platforms
(2011-04-01)
Hsieh, Hong-Jung
;
Lu, Tung-Wu
;
Chen, Sheng-Chang
;
Chang, Chia-Min
;
Hung, Chinghua
In human motion analysis, in situ calibration of the force plate is necessary to improve the accuracy of the measured ground reaction force (GRF) and center of pressure (COP). Few existing devices are capable of both static and dynamic calibration of the usually non-linear GRF and COP errors, while are also easy to move and/or set up without damaging the building. The current study developed a small device (160 cm x 88 cm x 43 cm) with a mass of 50 kg, equipped with auxiliary wheels and fixing suction pads for rapid deployment and easy set-up. A PC-based controller enabled quick movement and accurate positioning of the applied force to the calibration point. Static calibration at 100 validation points and dynamic calibration of a force plate were performed using the device. After correction by an artificial neural network (ANN) trained with the static data from another 121 points, the mean errors for the GRF were all reduced from a maximum of 0.64% to less than 0.01%, while those for the COP were all reduced from a maximum of about 1.37 mm to less than 0.04 mm. For dynamic calibration, the mean errors for the GRF were reduced from a maximum of 0.46% to less than 0.28%, while those for the COP were reduced from a maximum of 0.95 mm to less than 0.11 mm. The results suggest that the calibration device with the ANN method will be useful for obtaining more accurate GRF and COP measurements in human motion analysis. (C) 2011 Elsevier B.V. All rights reserved.