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RESEARCH PAPERS

General Uncertainty Analysis for Manual Wheelchair Propulsion Dynamics and Development of an Instrumented Wheel

[+] Author and Article Information
M. Mallakzadeh

Department of Mechanical Engineering, The University of British Columbia, Vancouver V6T 1Z4, BC, Canadamallak@mech.ubc.ca

F. Sassani

Department of Mechanical Engineering, The University of British Columbia, Vancouver V6T 1Z4, BC, Canadasassani@mech.ubc.ca

J. Med. Devices 1(2), 140-150 (Oct 17, 2006) (11 pages) doi:10.1115/1.2735970 History: Received October 31, 2005; Revised October 17, 2006

Manual wheelchair propulsion (MWP) is an inefficient and physically straining process. A reliably fabricated and instrumented wheel can help researchers to accurately calculate the forces and moments exerted by the wheelchair users and propose strategies to improve MWP. In this study, an instrumented wheel is designed, fabricated, and validated by using general uncertainty analysis. A six-component transducer is used to measure three-dimensional forces and moments applied by the wheelchair user on the handrim. The output of the transducer are forces and moments, which are directly transmitted to a PC using a USB port. By developing the transformation equations, the actual forces and moments on the hand of the wheelchair user are calculated. The angular position of the hand on the handrim is calculated from the kinetic data obtained through the instrumented wheel, and the derived equations. The general uncertainty analysis method is used to calculate the uncertainty values for the variables of interest with the Taylor series expansions. An analysis of the results shows that it is possible to obtain reliable information for MWP by using the instrumented wheel. Most of the data have uncertainties under 5% during much of the propulsion phase, and the patterns and overall behavior of the results are comparable to published data.

Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Instrumented wheel: (a) side view; and (b) front view

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Figure 2

Initial position and orientation of global and two local coordinate systems on the instrumented wheel

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Figure 3

Encoder gear system

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Figure 4

The roller-rig and wheelchair before instrumentation

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Figure 5

Illustration of local loads after θ deg of wheel rotation

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Figure 6

Propulsion force components with respect to global and hand local coordinate systems

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Figure 7

Propulsion moment components with respect to global coordinate system

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Figure 8

Illustration of forces and moments applied on the handrim: (a) side view; and (b) front view

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Figure 9

Global propulsive moment and angular position of the hand with respect to global coordinate system

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Figure 10

Comparison of the hand moment in the z direction for three different iterations

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Figure 11

Global propulsive and hand moments in the z direction after three trials

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Figure 12

Uncertainties for local force components during a possible range for propulsion phase

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Figure 13

Uncertainties for local moment components during a possible range for propulsion phase

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Figure 14

Uncertainties for local and global force components during the propulsion phase

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Figure 15

Uncertainties for local and global moment components during the propulsion phase

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Figure 16

Uncertainty for angular position of hand during the propulsion phase

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Figure 17

Uncertainty for hand moment in z direction with respect to the local hand coordinate system during the propulsion phase

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Figure 18

Measured and predicted sample force components

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Figure 19

Measured and predicted sample moment components

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