Modular FBG Bending Sensor for Continuum Neurosurgical Robot

Abstract

We present a modular sensing system to measure the deflection of a minimally invasive neurosurgical intracranial robot: MINIR-II. The MINIR-II robot is a tendon-driven continuum robot comprised of multiple spring backbone segments, which has been developed in our prior work. Due to the flexibility of the spring backbone and unique tendon routing configuration, each segment of MINIR-II can bend up to a large curvature (≥100 m −1) in multiple directions. However, the shape measurement of the robot based on tendon displacement is not precise due to friction and unknown external load/disturbance. In this regard, we propose a bending sensor module comprised of a fiber Bragg grating (FBG) fiber, a Polydimethylsiloxane (PDMS) cylinder, and a superelastic spring. The grating segment of the FBG fiber is enclosed inside a PDMS cylinder (1 mm in diameter), and the PDMS cylinder is bonded with the superelastic spring in series. The deflection or bending of the robot backbone segment is translated into an axial loading in the superelastic spring, which applies tension to the FBG; therefore, by measuring the peak wavelength shift of the FBG, the bending angle can be estimated. This paper describes the design, fabrication, and kinematic aspects of the sensor module in detail. To evaluate the proposed concept, one such sensor module has been tested and evaluated on the MINIR-II robot.

Movement Detection in Soft Robotic Gripper Using Sinusoidally Embedded Fiber Optic Sensor

“…Different kinds of FBG are designed and demonstrated for temperature, strain, bending, curvature, stretching and torsion sensing. Soft sensors based on FBG have also been used for strain and temperature sensing [8], shape reconstruction [18,[26][27][28] and curvature measurements [20,29]; however, they are essentially non-stretchable due to the stiffness of glass optical fiber. Previously, we demonstrated a fiber optic stretchable sensor by embedding an FBG in a sinusoidal configuration at an off-set position in a silicone film [30,31].…”

Learning to Detect Collisions for Continuum Manipulators Without a Prior Model

“…In recent years, FBG optical sensors have offered advantages over other sensing methods such as not requiring a direct line of sight, high streaming rate (up to 1 KHz), and minimal effects on compliance and compactness. FBG sensors have been used for shape, force, and torsion sensing in applications with CMs, biopsy needles, catheters, and other flexible medical instruments [7,8,9,12,13,14,19]. To this end, we implement our proposed method on a CM previously developed for MIS applications, equipped with FBG sensors for shape estimation [15,16,17].…”

Fibre Bragg Grating (FBG)-based force and pose sensing for endoscopic robotic systems

“…Similarly, there are two approaches to improve motion accuracy of a surgical robot: 1) elongation modeling of TSMs for motion compensation [15,25,44]; 2) direct motion sensing at the tooltip, including vision-based pose tracking [45][46][47], photosensor [48], electro-conductive yarn [49], magnetic sensors [50], and FBG sensors [51][52][53][54][55][56].…”

“…FBG sensor has recently become promising for bending sensing in flexible surgical manipulators [51,52], e.g., continuum neurosurgical robot [53,54] and steerable needle [55,56], due to its small size, flexibility, high sensitivity, and simplicity. Sheng et al…”

“…However, this sensor has a maximum measurable angle of 29° and an apparent hysteresis problem. Rahman et al developed a bending sensor module to capture the deflection of the MINIR-II robot by embedding an FBG within a Polydimethylsiloxane cylinder and attaching a superelastic nitinol spring [54]. The sensitivity varies from 3 pm/degree in the range of 0 to 20° to 5-7 pm/degree for 20° to 50°.…”