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Single-Fiber Optical Frequency Domain Reflectometry Shape Sensing of Continuum Manipulators with Planar Bending

Mobina Tavangarifard, Wendy Rodriguez Ovalle, Farshid Alambeigi

TL;DR

The paper tackles the challenge of real-time shape sensing in continuum manipulators by proposing a single-Fiber OFDR-based Shape Sensing Assembly (SSA) that attaches an OFDR fiber to a flat NiTi wire and integrates into a 170 mm soft CM. Through calibration and testing on C- and J-shaped bending, the approach yields high reconstruction accuracy, with sub-millimeter to low-millimeter tip and shape errors, and demonstrates the benefits of distributed sensing over multi-node FBG implementations. The key contributions include a geometry-optimized SSA design, a practical calibration procedure yielding a robust curvature–strain model, and a compact, manufacturable integration into a soft CM. These results highlight the method’s potential for accurate, scalable shape sensing in minimally invasive and soft-robotic applications, enabling improved control and safety in constrained environments. Future work will explore dynamic shape sensing and operation in obstructed environments to extend applicability.

Abstract

To address the challenges associated with shape sensing of continuum manipulators (CMs) using Fiber Bragg Grating (FBG) optical fibers, we feature a unique shape sensing assembly utilizing solely a single Optical Frequency Domain Reflectometry (OFDR) fiber attached to a flat nitinol wire (NiTi). Integrating this easy-to-manufacture unique sensor with a long and soft CM with 170 mm length, we performed different experiments to evaluate its shape reconstruction ability. Results demonstrate phenomenal shape reconstruction accuracy for both C-shape (< 2 mm tip error, < 1.2 mm shape error) and J-shape (< 3.4 mm tip error, < 2.3 mm shape error) experiments.

Single-Fiber Optical Frequency Domain Reflectometry Shape Sensing of Continuum Manipulators with Planar Bending

TL;DR

The paper tackles the challenge of real-time shape sensing in continuum manipulators by proposing a single-Fiber OFDR-based Shape Sensing Assembly (SSA) that attaches an OFDR fiber to a flat NiTi wire and integrates into a 170 mm soft CM. Through calibration and testing on C- and J-shaped bending, the approach yields high reconstruction accuracy, with sub-millimeter to low-millimeter tip and shape errors, and demonstrates the benefits of distributed sensing over multi-node FBG implementations. The key contributions include a geometry-optimized SSA design, a practical calibration procedure yielding a robust curvature–strain model, and a compact, manufacturable integration into a soft CM. These results highlight the method’s potential for accurate, scalable shape sensing in minimally invasive and soft-robotic applications, enabling improved control and safety in constrained environments. Future work will explore dynamic shape sensing and operation in obstructed environments to extend applicability.

Abstract

To address the challenges associated with shape sensing of continuum manipulators (CMs) using Fiber Bragg Grating (FBG) optical fibers, we feature a unique shape sensing assembly utilizing solely a single Optical Frequency Domain Reflectometry (OFDR) fiber attached to a flat nitinol wire (NiTi). Integrating this easy-to-manufacture unique sensor with a long and soft CM with 170 mm length, we performed different experiments to evaluate its shape reconstruction ability. Results demonstrate phenomenal shape reconstruction accuracy for both C-shape (< 2 mm tip error, < 1.2 mm shape error) and J-shape (< 3.4 mm tip error, < 2.3 mm shape error) experiments.
Paper Structure (15 sections, 6 equations, 8 figures, 2 tables)

This paper contains 15 sections, 6 equations, 8 figures, 2 tables.

Table of Contents

  1. INTRODUCTION
  2. Methodology
  3. Sensor Design and Assembly
  4. SSA Geometry Design
  5. Fabrication Process
  6. SSA Calibration Procedure
  7. Continuum Manipulator Design and Fabrication
  8. Shape Sensing Procedure and Experiments
  9. Evaluation Metrics
  10. Results
  11. Calibration Results
  12. C-Shape Bending Results
  13. J-Shape Bending Results
  14. Discussion
  15. Conclusion

Figures (8)

  • Figure 1: An overview of the used the sensorized CM with the OFDR-based SSA. Figure also shows the SSA structure modeled as a composite beam.
  • Figure 2: Fabrication setup used to mount the OFDR fiber on a flat NiTi wire.
  • Figure 3: (a) Calibration jig used to calibrate the SSA, (b) C-shape SS jig, and (c) J-shape SS jig used to perform SS procedure.
  • Figure 4: (a) Strain-curvature plot in the negative bending direction; (b) Average calibration strain measurements along the OFDR SSA for ten considered curves.
  • Figure 5: C-shape bending strain and radius of curvature along the length of the SSA.
  • ...and 3 more figures