Characterizing the Resilience and Sensitivity of Polyurethane Vision-Based Tactile Sensors

TL;DR

This paper compares polyurethane and silicone gels in vision-based tactile sensors, demonstrating polyurethane's increased robustness and suitability for high-load, rugged applications despite reduced sensitivity at low forces.

Contribution

It introduces a systematic characterization protocol for resilience and sensitivity of polyurethane-based VBTS, highlighting polyurethane's advantages over silicone in durability.

Findings

Polyurethane provides higher durability under load and abrasion.

Sensitivity at low forces is reduced with polyurethane compared to silicone.

Polyurethane sensors have an increased effective force range.

Abstract

Vision-based tactile sensors (VBTSs) are a promising technology for robots, providing them with dense signals that can be translated into a multi-faceted understanding of contact. However, existing VBTS tactile surfaces make use of silicone gels, which provide high sensitivity but easily deteriorate from loading and surface wear. We propose that polyurethane rubber, a typically harder material used for high-load applications like shoe soles, rubber wheels, and industrial gaskets, may provide improved physical gel resilience, potentially at the cost of sensitivity. To compare the resilience and sensitivity of two polyurethane gel formulations against a common silicone baseline, we propose a series of repeatable characterization protocols. Our resilience tests assess sensor durability across normal loading, shear loading, and abrasion. For sensitivity, we introduce learning-free assessments of force and spatial sensitivity to directly measure the physical capabilities of each gel without effects introduced from data and model quality. We also include a bottle cap loosening and tightening demonstration to validate the results of our controlled tests with a real-world example. Our results show that polyurethane yields a more robust sensor. While it sacrifices sensitivity at low forces, the effective force range is largely increased, revealing the utility of polyurethane VBTSs over silicone versions in more rugged, high-load applications.