Abstract
In this work, a large deformation, non-linear semi-analytical model for an all-elastomer, capacitive tactile unit-sensor is developed. The model is capable of predicting the response of such sensors over their entire sensing range under the application of normal forces. In doing so the finite flat punch indentation model developed earlier is integrated with a capacitance model to predict the change-in-capacitance as a function of applied normal forces. The empirical change-in-capacitance expression, based on the parallel plate capacitance model, is developed to account for the fringe field and saturation effects. The elastomeric layer used as a substrate in these sensors is modeled as an incompressible, non-linear, hyperelastic material. More specifically, the two term Mooney-Rivlin strain energy function is used as a constitutive response to relate the stresses and strains. The developed model assumes both geometrical as well as material non-linearity. Based on the related experimental work presented elsewhere, the inverse analysis, combining finite element (FE) modeling and non-linear optimization, is used to obtain the Mooney-Rivlin material parameters. Finally, to validate the model developed herein the model predictions are compared to the experimental results obtained elsewhere for four different tactile sensors. Great agreements are found to exist between the two which shows the model capabilities in capturing the response of these sensors. The model and methodologies developed in this work, may also help advancing bio-material studies in the determination of biological tissue properties.
Highlights
Owing to advances in robotics and bionic technologies in the past few decades, tactile sensors have been the subject of intense attention [1,2,3]
The purpose of the current study is to develop a large-deformation, large-strain model capable of predicting the response of the fabricated sensors under the application of normal forces covering their full sensing range
Using the experimental results and non-linear curve fitting, the enhanced capacitance model based on the parallel plate capacitance theory was developed to account for the fringe field as well as saturation effects
Summary
Owing to advances in robotics and bionic technologies in the past few decades, tactile sensors have been the subject of intense attention [1,2,3]. In recent years, in addition to tactile sensor design and development, a lot of attention has been given to research in texture identification. In such works, the focus is on tactile information processing and tactile learning instead of the technological aspects of these devices. Watanabe et al [4] developed a multi-axial tactile sensor using micro-cantilevers embedded in a soft elastomeric layer. They showed that their proposed design is capable of identifying three various kind of papers. In another work by Friedl et al [6], the authors, inspired by the biology of Sensors 2018, 18, 3614; doi:10.3390/s18113614 www.mdpi.com/journal/sensors
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