A Single-Fiber Optical Frequency Domain Reflectometry (OFDR)-Based Shape Sensing of Concentric Tube Steerable Drilling Robots
2026-03-18 • Robotics
Robotics
AI summaryⓘ
The authors developed a new way to sense the shape of flexible drilling robots using a technology called Optical Frequency Domain Reflectometry (OFDR), which measures strain continuously along a fiber. They combined an OFDR fiber with a flat nickel-titanium wire to create a shape sensing device that is placed inside the drilling tool, protecting it during operation. This approach avoids the need to stick sensors onto the outside of the tool, which is common in other methods. Tests showed that their design can accurately track the shape of the drill during complex movements, proving it works well and is reliable.
Concentric Tube Steerable Drilling RobotsOptical Frequency Domain ReflectometryShape Sensing AssemblyNiTi wireFlexible drilling instrumentStrain measurementFiber optic sensorsShape sensingSawbones phantom
Authors
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.