A Single-Fiber Optical Frequency Domain Reflectometry (OFDR)-Based Shape Sensing of Concentric Tube Steerable Drilling Robots

TL;DR

This paper presents a novel shape-sensing method for steerable drilling robots using OFDR fiber technology, offering continuous, high-resolution strain measurement without complex integration, and validated through experiments.

Contribution

It introduces a new shape-sensing assembly using OFDR fiber integrated with a NiTi wire, enabling accurate shape sensing in steerable drilling robots without surface attachment.

Findings

Accurate shape sensing demonstrated in synthetic phantoms.

Robust performance during free-bending and drilling trajectories.

Enhanced spatial resolution compared to traditional methods.

Abstract

This paper introduces a novel shape-sensing approach for Concentric Tube Steerable Drilling Robots (CT-SDRs) based on Optical Frequency Domain Reflectometry (OFDR). Unlike traditional FBG-based methods, OFDR enables continuous strain measurement along the entire fiber length with enhanced spatial resolution. In the proposed method, a Shape Sensing Assembly (SSA) is first fabricated by integrating a single OFDR fiber with a flat NiTi wire. The calibrated SSA is then routed through and housed within the internal channel of a flexible drilling instrument, which is guided by the pre-shaped NiTi tube of the CT-SDR. In this configuration, the drilling instrument serves as a protective sheath for the SSA during drilling, eliminating the need for integration or adhesion to the instrument surface that is typical of conventional optical sensor approaches. The performance of the proposed SSA, integrated within the cannulated CT-SDR, was thoroughly evaluated under free-bending conditions and during drilling along multiple J-shaped trajectories in synthetic Sawbones phantoms. Results demonstrate accurate and reliable shape-sensing capability, confirming the feasibility and robustness of this integration strategy.