Shape Sensing and Tip Tracking Via Reciprocating Magnet in the Soft Continuum Robot

Abstract

Soft continuum robots, attributable to inherently compliant trunks and shape manipulability, have been widely deployed in complex scenarios requiring safe human-robot interaction. However, their nonlinear deformations and hyperredundant degrees of freedom pose substantial challenges for full-body shape sensing and closed-loop control of the end effector. A low-cost yet accurate feedback solution is thus highly desirable. To address this, we present a hydraulicdriven reciprocating magnet strategy, integrated with magnetic localization, to enable both shape sensing and tip pose estimation of soft continuum robots, thereby facilitating precise closed-loop control. The proposed approach time-multiplexes a single magnet under different operational phases to fulfill two functions: full-body shape reconstruction and tip pose tracking. We validate the effectiveness of the reciprocating magnet system on a pneumatic manipulator prototype with two active degrees of freedom. Experimental results show that the magnet can travel through the guide channel at a maximum speed of 6.5 cm/s, achieving average errors of less than 2 mm in position (1.1% of the robot’s length), 3◦ in orientation for shape sensing and tip pose estimation. Using this sensing strategy, we demonstrate a simple closed-loop control on the soft continuum robot. Owing to its simplicity, low cost, and high precision, the proposed method holds promise as a practical alternative for state feedback in soft continuum robots.