Hybrid Tendon and Ball Chain Continuum Robots for Enhanced Dexterity in Medical Interventions

TL;DR

This work introduces a hybrid two-section continuum robot that merges a proximal tendon-actuated tube with a distal magnetically actuated ball chain to create a dexterous workspace capable of approaching a target from arbitrary directions. By combining a Cosserat-rod-based tendon model with a magnetic-ball-chain energy minimization framework, the authors derive both a full mechanics-based solution and simplified sequential/closed-form kinematics, enabling efficient design and control. Experimental validation demonstrates mean tip errors around 3% of robot length and validates a dexterous workspace that enables multi-directional tip approaches, while also revealing tube-ball-chain coupling effects that influence accuracy. The proposed framework offers a pathway to clinically relevant steerable catheters with enhanced maneuverability, and sets the stage for future work in coupled mechanics and real-time control for medical interventions.

Abstract

A hybrid continuum robot design is introduced that combines a proximal tendon-actuated section with a distal telescoping section comprised of permanent-magnet spheres actuated using an external magnet. While, individually, each section can approach a point in its workspace from one or at most several orientations, the two-section combination possesses a dexterous workspace. The paper describes kinematic modeling of the hybrid design and provides a description of the dexterous workspace. We present experimental validation which shows that a simplified kinematic model produces tip position mean and maximum errors of 3% and 7% of total robot length, respectively.

Figures (6)

• Figure 1: Hybrid robot comprised of proximal tendon-actuated section and distal telescoping magnetic ball-chain section.
• Figure 2: Hybrid model parameters. Proximal section, $l_t$, is assumed constant curvature with radius of curvature $\rho$ under tension $F$. Extended ball chain, $l_c$, is assumed linear in field direction $\pmb B$.
• Figure 3: Dexterous workspace. (a) Side view orientation angle range, $\alpha_M$, as function of $x$. (b) Front view orientation angle, $\beta_M$, as function of $x$. (c) $\alpha_M$ and $\beta_M$ as a function of $x$. Dexterous workspace lies in range $d_c \le x \le r_d - d_c$
• Figure 4: Experiment set up for Front View magnetic field rotations about the $\pmb{x}$ axis.
• Figure 5: Side view experimental results for configurations with (a) smallest error; (b) largest error.