Continuum Robot Shape Estimation Using Magnetic Ball Chains

TL;DR

This paper introduces a novel, low-cost magnetic ball chain method for real-time shape sensing of continuum robots, enhancing medical procedures with accurate internal visualization.

Contribution

It proposes using magnetic ball chains encased in a flexible sleeve for shape sensing, including a model, analysis, and experimental validation.

Findings

Maximum tip position error of 7.1% of total length

Average tip position error of 2.9% of total length

Effective shape estimation demonstrated in experiments

Abstract

Shape sensing of medical continuum robots is important both for closed-loop control as well as for enabling the clinician to visualize the robot inside the body. There is a need for inexpensive, but accurate shape sensing technologies. This paper proposes the use of magnetic ball chains as a means of generating shape-specific magnetic fields that can be detected by an external array of Hall effect sensors. Such a ball chain, encased in a flexible polymer sleeve, could be inserted inside the lumen of any continuum robot to provide real-time shape feedback. The sleeve could be removed, as needed, during the procedure to enable use of the entire lumen. To investigate this approach, a shape-sensing model for a steerable catheter tip is derived and an observability and sensitivity analysis are presented. Experiments show maximum estimation errors of 7.1% and mean of 2.9% of the tip position with respect to total length.