A High-Sensitivity Fiber Bragg Grating-Based Distal Force Sensor for Laparoscopic Surgery

This paper presents a Fiber Bragg Grating (FBG)-based distal force sensor with a high sensitivity and a relatively large measurement range to provide force feedback for laparoscopic surgery. The proposed sensor design mainly consists of a force-sensitive flexure, one tightly suspended optical fiber embedded with an FBG sensing element and a contact head. The proposed flexure has been miniaturized based on improvement and optimization of a parallel structure form and a serial cantilever beam-based structure to achieve an excellent axial linear force-deformation relationship and a large measurement range. The optical fiber adopts a two-point pasting method, and has been tightly stretched and glued along the flexure's central line to achieve improved sensitivity and avoid FBG chirping failure. Finite element method (FEM)-based simulation has been performed to investigate both static and dynamic performances of the proposed design. The simulation-enabled optimization has been implemented to achieve optimal structural parameters and enhanced sensitivity. The optimized design has been prototyped and calibrated to demonstrate an excellent linearity with a small linearity error of 0.14% and achieve a high resolution of 21mN within a measurement range of [0, 12N]. The further optimized version with the removal of small deformation constraint can reach a higher resolution of 9.3 mN within an operating range of [0, 7N]. Dynamic loading experiments have been conducted to validate the effectiveness of the proposed designs.