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

Yash Kulkarni, Mobina Tavangarifard, Daniyal Maroufi, Mohsen Khadem, Justin E. Bird, Jeffrey H. Siewerdsen, Farshid Alambeigi

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.

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

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.
Paper Structure (10 sections, 5 equations, 7 figures, 1 table)

This paper contains 10 sections, 5 equations, 7 figures, 1 table.

Table of Contents

  1. Introduction
  2. Shape Sensing Assembly and Steerable Drilling Robotic System
  3. Shape Sensing Assembly Fabrication and Calibration
  4. A Cannulated Concentric Tube Steerable Drilling Robot
  5. Experimental Evaluation and Results
  6. Free-Space Bending Test
  7. Drilling Experiments in Sawbones Phantoms
  8. Evaluation Metrics
  9. Discussion
  10. Conclusion and Future Work

Figures (7)

  • Figure 1: Conceptual illustration of the Sensorized CT-SDR compared to a conventional rigid drilling tool. Zoomed in view highlights the individual components of the CT-SDR. A cross-sectional view shows the proposed OFDR-based SSA passing 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.
  • Figure 2: Rendered image of the Sensorized CT-SDR with labeled dimensions of its individual components. A zoomed-in view highlights the OFDR SSA and its dimensions in both top view and isometric view. The off-axis drill bit phenomenon is illustrated in the rendered image and further supported by an actual photograph of the drill bit, which also includes dimensional annotations.
  • Figure 3: (A) Calibration jig with slots of varying radii of curvature. (B) Measured strain data collected in both positive and negative direction by OFDR SSA for various radii of curvature based on custom jig measurement.
  • Figure 4: Calibration between strain and radius of curvature for the SSA in both positive and negative bending directions.
  • Figure 5: Experimental Setup consisting of a KUKA Robot arm, Fluoroscopic X-Ray machine, Cannulated CT-SDR, and the OFDR shape sensor and interrogator. Close up views of the sensor inside the flexible drilling instrument is shown along with a zoomed in view of the flexible drilling instrument with dimensions and the NiTi tubes.
  • ...and 2 more figures