# Design of a Clip-On Modular Tactile Sensing Attachment Based on Fiber Bragg Gratings: Theoretical Modeling and Experimental Validation

## TL;DR

This paper introduces a modular tactile sensing attachment for robots that can be easily swapped and provides accurate force measurements using fiber Bragg gratings.

## Contribution

The novel contribution is a clip-on tactile module with interchangeable sensor cores and a validated opto-mechanical model for force sensing.

## Key findings

- The opto-mechanical model predicts forces with less than 8% error across different module sizes.
- Case II (hollow PSC) has twice the force sensitivity of Case I (solid insert) but lower linearity.
- A new metric Q helps balance sensitivity, linearity, and dynamic lag in tactile perception.

## Abstract

Despite widespread modular tooling in robots and automated systems, tactile sensing lags behind, constrained by custom and non-interchangeable sensors. To close this gap, we developed a clip-on cylindrical tactile module that combines a snap-fit Clip-on Cap (CC) with a plug-in Sensor Core (PSC) hosting an array of force sensing and temperature-reference fiber Bragg gratings (FBGs). An opto-mechanical model relates Bragg wavelength shifts to external forces through parameterized dimensions and remains applicable across varied module sizes. Two loading configurations are examined: Case I, a PSC fitted with a compliant PSC-solid insert, and Case II, a hollow PSC. Experiments across both configurations validate the model, with prediction errors below 8%. Case II offers up to twice the force sensitivity of Case I, whereas Case I maintains slightly higher linearity (R2 > 0.95). We propose a metric, Q, for assessing the trade-off among sensitivity, linearity, and dynamic lag; analyses with this metric establish that softer solid inserts enhance tactile force perception. The CC–PSC pair can be rapidly swapped or detached to meet diverse application needs. These results provide a transferable design and modeling framework for equipping robots—or other automated systems—with universally deployable, clip-on tactile perception.