A cam-displacement transducer device for measuring bi plane prosthetic motion

Twiste, M; Rithalia, S; Kenney, LPJ

Abstract

An electromechanical system is described that comprises a cam and two linear displacement transducers for measuring
two-degree of freedom. This is aimed at quantifying the extent and pattern of both transverse rotation and longitudinal translation
that takes place during amputee gait at what is sometimes termed a ‘‘torque-shock absorbing adapter’’ located between the
prosthetic socket and foot.
Both types of motion are measured independently by mounting the cam around the adapter and the two transducers orthogonal
to one another with their spring loaded plungers moving separately against the cam’s perimeter and distal, flat face. The cam
geometry should be an arc of a spiral and not a circle for the angular displacement measurement to be linear in response to
rotation. Over a range of �18v for transverse rotation the maximum deviation of the ideal cam geometry away from an arc of a
circle is less than �0.5% of the transducers’ 10 mm stroke. The transducer’s linearity is �2% and itcould therefore be assumed
that this would be the dominant source of error. The theoretical predictions are supported by the calibration results, in which the
pattern of errors that are found in the transducers’ calibration can also be seen in the calibration of the cam.
# 2004 IPEM. Published by Elsevier Ltd. All rights reserved.

Citation

Twiste, M., Rithalia, S., & Kenney, L. (2004). A cam-displacement transducer device for measuring bi plane prosthetic motion. Medical Engineering and Physics, 26(4), 335-340. https://doi.org/10.1016/j.medengphy.2004.01.002

• Journal Article Type: Article
• Publication Date: Jan 1, 2004
• Deposit Date: Dec 21, 2010
• Journal: Medical Engineering & Physics
• Print ISSN: 1350-4533
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 26
• Issue: 4
• Pages: 335-340
• DOI: https://doi.org/10.1016/j.medengphy.2004.01.002
• Publisher URL: http://dx.doi.org/10.1016/j.medengphy.2004.01.002