FBG-Based Variable-Length Estimation for Shape Sensing of Extensible Soft Robotic Manipulators

TL;DR

This paper introduces a novel FBG-based variable-length estimation method for accurate shape sensing of extensible soft robots, overcoming the limitations of traditional FBG sensors in stretching range.

Contribution

It presents a new length sensor using a curved channel and a model-free filtering technique for simultaneous calibration and continuous length estimation.

Findings

Demonstrates high accuracy in length and shape sensing in experiments

Shows robustness in unstructured environments

Validates effectiveness through experimental results

Abstract

In this paper, we propose a novel variable-length estimation approach for shape sensing of extensible soft robots utilizing fiber Bragg gratings (FBGs). Shape reconstruction from FBG sensors has been increasingly developed for soft robots, while the narrow stretching range of FBG fiber makes it difficult to acquire accurate sensing results for extensible robots. Towards this limitation, we newly introduce an FBG-based length sensor by leveraging a rigid curved channel, through which FBGs are allowed to slide within the robot following its body extension/compression, hence we can search and match the FBGs with specific constant curvature in the fiber to determine the effective length. From the fusion with the above measurements, a model-free filtering technique is accordingly presented for simultaneous calibration of a variable-length model and temporally continuous length estimation of the robot, enabling its accurate shape sensing using solely FBGs. The performances of the proposed method have been experimentally evaluated on an extensible soft robot equipped with an FBG fiber in both free and unstructured environments. The results concerning dynamic accuracy and robustness of length estimation and shape sensing demonstrate the effectiveness of our approach.