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Vol. 37 No. 1, January/February 2000
Pages 81 - 88

A technique for quantifying the response of seated individuals to dynamic perturbations

Derek G. Kamper, PhD; Thomas C. Adams, MA; Steven I. Reger, PhD; Mohamad Parnianpour, PhD; Kamran Barin, PhD; Maureen A. Linden, MS

Biomedical Engineering Center, Ohio State University, Columbus, OH 43210; Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL 60611; Department of Rehabilitation Medicine, Cleveland Clinic Foundation, Cleveland, OH 44195; Department of Industrial Systems Engineering, Ohio State University, Columbus, OH 43210; Department of Otolaryngology, Ohio State University, Columbus, OH 43210; Department of Rehabilitation Technology, Helen Hayes Hospital, West Haverstraw, NY 10993

Abstract--A technique is presented for monitoring the seated postural stability and control of human subjects. Estimates are made of the locations of the subject's center of pressure (CPS) and projection of the center of mass (CMNP) from moment balance equations using measured force and acceleration data. The CPS and CMNP indices describe the stability of the subject, independent of the chair, even in the presence of perturbations. The measurement system was evaluated for both rigid objects and human subjects situated in a wheelchair undergoing displacement. Estimated CMNP was within ±5 mm of the actual value for static loads. For human subjects, the average correlation coefficient between the estimated CMNP signal and that computed from video data was 0.90; however, transient overestimation of displacement was seen during subject acceleration. The technique could help to better assess seated stability in dynamic environments, such as those experienced by wheelchair users in motor vehicles.

Key words: center of mass, center of pressure, seating, stability.

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