Influence of calibration method and material on the accuracy of stress distribution measurement systems

Karsten Engel; Ulrich Hartmann; Wolfgang Potthast; Gert-Peter Brüggemann

doi:10.1515/bmt-2014-0158

Article

Influence of calibration method and material on the accuracy of stress distribution measurement systems

Karsten Engel , Ulrich Hartmann , Wolfgang Potthast and Gert-Peter Brüggemann

Published/Copyright: July 4, 2015

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From the journal Biomedical Engineering / Biomedizinische Technik Volume 61 Issue 3

Abstract

Biomechanical analyses of the stress distribution and the force transfer in the human knee are essential to better understand the aetiology of joint diseases. Accuracy studies of commonly used capacitive or resistive-based stress distribution measurement systems have led to severe problems caused by an inaccurate experimental setup. For instance, in one study, overestimations of the measured forces in the sensor’s centre were reported. Therefore, the primary aim of this study was to investigate the ability of capacitive and resistive-based sensors to measure forces in a homogenous pressure environment and the secondary goal was to analyse the influence of different calibration materials on the measurement accuracy. A Novel pressure vessel and metal indenters covered with different rubber materials were used in combination with a material testing machine to load the sensors. Four different linearly increasing nominal forces (925–3670 N) were applied and the deviations between the nominal and the measured forces were calculated. The capacitive measurement system showed errors between 1% and 7% in the homogenous pressure environment, whereas the errors of the resistive system were found to vary between 4% and 17%. The influence of the calibration material was observed to be greater for the resistive sensors (1–179%) than for the capacitive sensors (0.5–25%). In conclusion, it can be stated that – for the pressure measurement systems compared in this article – the capacitive one is less sensitive to the calibration method and the calibration material than the resistive system.

Keywords: biomechanics; calibration methods; contact stress distribution; Novel Pliance Kneepad sensor; Tekscan ISCAN Sensor

Corresponding author: Karsten Engel, Institute of Biomechanics and Orthopedics, German Sport University of Cologne, Am Sportpark Müngersdorf 6, 50933, Cologne, Germany, Phone: +49(0)221-4982-7630, Fax: +49(0)221–4971598, E-mail: k.engel@dshs-koeln.de

Acknowledgments

We thank Martin Küsel and Jürgen Geiermann from the precision engineering workshop for their technical aid and the construction of the pressure vessel.

Conflict of interest and funding: The authors did not receive any financial support or have personal relationships with other people or organizations that could inappropriately influence their work.

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Received: 2014-11-8

Accepted: 2015-6-10

Published Online: 2015-7-4

Published in Print: 2016-6-1

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Articles in the same Issue

https://doi.org/10.1515/bmt-2014-0158

Keywords for this article

biomechanics; calibration methods; contact stress distribution; Novel Pliance Kneepad sensor; Tekscan ISCAN Sensor