# Polymer-Based Self-Calibrated Optical Fiber Tactile Sensor

## TL;DR

This paper introduces a polymer-based optical fiber tactile sensor that accurately measures normal and shear forces while accounting for object size, enhancing robotic tactile sensing capabilities.

## Contribution

It presents a novel self-calibrated tactile sensor using anisotropic optical fibers to decouple forces and calibrate based on object size, improving measurement accuracy.

## Key findings

- Force measurement accuracy: 0.15N (normal), 0.17N (X shear), 0.18N (Y shear)
- Object size measurement accuracy: 0.4mm within 5-12mm range
- Effective force and size reconstruction at robotic arm tip

## Abstract

Human skin can accurately sense the self-decoupled normal and shear forces when in contact with objects of different sizes. Although there exist many soft and conformable tactile sensors on robotic applications able to decouple the normal force and shear forces, the impact of the size of object in contact on the force calibration model has been commonly ignored. Here, using the principle that contact force can be derived from the light power loss in the soft optical fiber core, we present a soft tactile sensor that decouples normal and shear forces and calibrates the measurement results based on the object size, by designing a two-layered weaved polymer-based optical fiber anisotropic structure embedded in a soft elastomer. Based on the anisotropic response of optical fibers, we developed a linear calibration algorithm to simultaneously measure the size of the contact object and the decoupled normal and shear forces calibrated the object size. By calibrating the sensor at the robotic arm tip, we show that robots can reconstruct the force vector at an average accuracy of 0.15N for normal forces, 0.17N for shear forces in X-axis , and 0.18N for shear forces in Y-axis, within the sensing range of 0-2N in all directions, and the average accuracy of object size measurement of 0.4mm, within the test indenter diameter range of 5-12mm.