Journal of Rehabilitation Research & Development (JRRD)

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Volume 49 Number 1, 2012
   Pages 1138 — 1137

Abstract — Test method for empirically determining inertial properties of manual wheelchairs

Matthew R. Eicholtz, MS;1–2* Jayme J. Caspall, MS;1–2 Phuc V. Dao, MS;1–2 Stephen Sprigle, PhD, PT;2–3 Al Ferri, PhD1
1Department of Mechanical Engineering; 2Rehabilitation Engineering and Applied Research Laboratory, College of Architecture; and 3Department of Applied Physiology, Georgia Institute of Technology, Atlanta, GA

Abstract — The iMachine is a spring-loaded turntable used to measure inertial properties of irregularly shaped rigid bodies, specifically manual wheelchairs. We used a Newton-Euler approach to calculate wheelchair mass and center of mass (CM) location from static force measurements using load cells. We determined the moment of inertia about the vertical axis from the natural frequency of the system in simple harmonic motion. The device was calibrated to eliminate the effects of platform components on measurement error. For objects with known inertial properties, the average relative error of the mass and the CM coordinates (x and y) were 0.76%, 0.89%, and 1.99%, respectively. The resolution of the moment of inertia calculation depends on the ratio of test piece inertia to system inertia, such that the higher the ratio, the more accurate the measurements. We conducted a Gage Repeatability and Reproducibility (Gage R&R) test using three manual wheelchairs measured three times by three operators; the results showed that over 90% of the variance in inertia was caused by differences in the wheelchairs being measured. Gage R&R analysis indicated that measurement system operation was acceptable using criteria from the Automobile Industry Action Group for both inertia and mass measurements.

Key words: center of mass, free vibration, iMachine, mass, mathematical models, mechanical design, moment of inertia, rigid-body dynamics, simple harmonic oscillator, wheelchair testing.

View HTML  ¦  View PDF  ¦  Contents Vol. 49, No. 1
This article and any supplementary material should be cited as follows:
Eicholtz MR, Caspall JJ, Dao PV, Sprigle S, Ferri A. Test method for empirically determining inertial properties of manual wheelchairs. J Rehabil Res Dev. 2012;49(1):51–62.
http://dx.doi.org/10.1682/JRRD.2011.03.0045
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Last Reviewed or Updated  Wednesday, February 15, 2012 2:29 PM

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