A Tri-Axial FBG-Based Force Sensor at the Tool Tip of a Continuum Manipulator for Single-Port Access Surgery

Abstract

Abstract— The absence of force feedback remains a major bottleneck in the development of robotic laparoendoscopic single-site (R-LESS) surgery, reducing the control precision of surgical instruments and increasing the risk of tissue damage. To address this challenge, we propose a miniature triaxial force sensor based on Fiber Bragg Grating (FBG), featuring high precision, nonlinear decoupling capability, and seamless integration with the tool tip of a continuum manipulator for singleport access surgery. The sensor features a monolithic elastic body with a dumbbell-shaped groove, where four FBGs are symmetrically arranged at 90◦ intervals around the circumference to form a redundant measurement unit, thereby enhancing sensing accuracy. A novel Whale Migration Algorithm Based Kernel Extreme Learning Machine (WMA-KELM) is introduced to address the nonlinear coupling influences arising from manipulator integration, demonstrating superior accuracy and robustness compared to conventional methods. Experimental results show that within the ranges of axial force [0 N, 5 N] and radial force [-2.5 N, 2.5 N], the maximum full-scale (FS) error is less than 1% in all dimensions, the maximum RMSE is 0.0308 N, and the maximum repeatability error is within ±0.24%. These results validate the force sensor integrated with the continuum manipulator, and the proposed algorithm is effective and reliable.