Citation: Manaf, E.; Fitzgerald, K.;
Higginbotham, C.L.; Lyons, J.G.
Computer Vision System: Measuring
Displacement and Bending Angle of
Ionic Polymer-Metal Composites.
Appl. Sci. 2022, 12, 6744. https://
doi.org/10.3390/app12136744
Academic Editor: Eric Guibal
Received: 13 June 2022
Accepted: 1 July 2022
Published: 3 July 2022
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Article
Computer Vision System: Measuring Displacement and
Bending Angle of Ionic Polymer-Metal Composites
Eyman Manaf
1
, Karol Fitzgerald
1
, Clement L. Higginbotham
2
and John G. Lyons
1,
*
1
Faculty of Engineering & Informatics, Technological University of The Shannon: Midlands Midwest, Dublin
Road, N37 HD68 Athlone, Co. Westmeath, Ireland; eyman.research@gmail.com (E.M.); kfitzgerald@ait.ie (K.F.)
2
Materials Research Institute, Technological University of The Shannon: Midlands Midwest, Dublin Road,
N37 HD68 Athlone, Co. Westmeath, Ireland; chigginbotham@ait.ie
* Correspondence: sean.lyons@tus.ie
Featured Application: The proposed vision system can be used to measure the displacement and
bending angle of ionic polymer–metal composites (IPMCs).
Abstract:
A computer vision system for measuring the displacement and bending angle of ionic
polymer–metal composites (IPMC) was proposed in this study. The logical progression of measuring
IPMC displacement and bending angle was laid out. This study used Python (version 3.10) in
conjunction with OpenCV (version 4.5.5.64) for the development of the vision system. The coding
functions and the mathematical formulas used were elaborated on. IPMC contour detection was
discussed in detail, along with appropriate camera and lighting setups. Measurements generated
from the vision system were compared to approximated values via a manual calculation method.
Good agreement was found between the results produced by the two methods. The mean absolute
error (MAE) and root mean squared error (RMSE) for the displacement values are 0.068080668
and 0.088160652, respectively, and 0.081544205 and 0.103880163, respectively, for the bending angle
values. The proposed vision system can accurately approximate the displacement and bending angle
of IPMCs.
Keywords:
ionic polymer–metal composite (IPMC); computer vision; OpenCV; Python; Nafion;
displacement measurement; bending angle measurement
1. Introduction
Electroactive polymers (EAPs) are currently the closest in emulating natural muscles,
earning the moniker artificial muscle for some [
1
–
3
]. EAPs deform in response to an electric
field [
1
]. Known for their high power-to-weight ratio, EAPs are relatively new and require
extensive research to establish a grounded understanding of their basic principles and
what parameters control their electro-activation behaviour [
3
,
4
]. Ionic polymer–metal
composites (IPMCs) are a subset of EAPs known for their sensing and actuating abilities [
1
].
The general structure of an IPMC consists of a polymer membrane sandwiched between
metal electrodes. Nafion, a perfluorinated sulfonic-acid (PFSA) ionomer developed and
trademarked by DuPont, is commonly used as the polymer membrane for IPMCs, with
platinum as the electrodes [
1
]. One method of characterising IPMC behaviour is to measure
its displacement under voltage loading. This study looks at proposing a computer vision
system to measure this displacement along with its bending angle.
Measuring the displacement of IPMCs entails looking at the tip-to-tip displacement
of the composite under various voltage loadings, usually from 1 V to 10 V. Two meth-
ods of measuring displacement are generally found in literature: measurement using a
camera or using a laser displacement sensor [
5
–
16
]. Some studies combine both methods,
interchanging them depending on how large the displacement and bending angle is [17].
Appl. Sci. 2022, 12, 6744. https://doi.org/10.3390/app12136744 https://www.mdpi.com/journal/applsci
