Shape Sensing and Tip Tracking via Reciprocating Magnet in the Soft Continuum Robot
Pingyu Xiang, Zexi Zhao, Hongye Zhang, Yue Wang, Rong Xiong, Haojian Lu
AI summary
Problem
Nonlinear deformations and hyper-redundant degrees of freedom in soft continuum robots make precise full-body shape sensing and tip tracking difficult, while existing methods are often costly, complex, or lack continuous tip accuracy.
Approach
The method hydraulically drives a single permanent magnet to reciprocate along the robot's internal channel while an external magnetic sensor array continuously localizes it, using time-multiplexed data to reconstruct the backbone shape and track the tip pose.
Key results
- Magnet travel speed reaches 6.5 cm/s in guide channels
- Average position error under 2 mm and orientation error under 3°
- Real-time pose estimation computed in under 25 ms per frame
- Successful closed-loop tip control demonstrated on a pneumatic prototype
Why it matters
Offers a practical, low-cost, and high-precision feedback solution for safe and accurate control of soft continuum robots in medical and industrial applications.
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 hyper- redundant 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 hydraulic- driven reciprocating magnet strategy, integrated with magnetic localization, to enable both shape sensing and tip pose esti- mation 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.