Helical Tendon-Driven Continuum Robot with Programmable Follow-the-Leader Operation

2026-01-19

AI Summary

This study addresses the challenge of imprecise placement of manually guided spinal cord stimulation electrodes in the ventral or lateral epidural space, which limits therapeutic efficacy for motor function recovery. To overcome this, the authors propose ExoNav, a tendon-driven continuum robot with a helical architecture that integrates insertion and rotation degrees of freedom for accurate navigation through complex spinal pathways. The design innovatively combines a helical configuration with a programmable Follow-the-Leader (FTL) strategy, supported by a Cosserat rod–based model that couples tendon actuation with deformation and incorporates a gravity compensation mechanism to optimize tendon tension under external loads. Experimental results demonstrate that four prototype variants achieve root-mean-square positioning errors as low as 1.33–2.33 mm, with a maximum path-following error of 3.75 mm in FTL mode, successfully reaching targeted ventral and lateral spinal cord regions as well as dorsal root ganglia in phantom models.

Technology Category

• Intelligent Robots: Motion and Path Planning
• Planning, Routing, and Scheduling: Mixed Discrete/Continuous Planning
• Humans and AI: Planning and Decision Support for Human-Machine Teams

Application Category

• Responsible Web: Machine-in-the-loop, human agency and autonomy
• User Modeling, Personalization and Recommendation: On-Device user modeling, personalization, and recommendation
• Systems and Infrastructure for Web, Mobile and WoT: Experiences and lessons learnt from Web-based algorithms and system deployments

Abstract

Spinal cord stimulation (SCS) is primarily utilized for pain management and has recently demonstrated efficacy in promoting functional recovery in patients with spinal cord injury. Effective stimulation of motor neurons ideally requires the placement of SCS leads in the ventral or lateral epidural space where the corticospinal and rubrospinal motor fibers are located. This poses significant challenges with the current standard of manual steering. In this study, we present a static modeling approach for the ExoNav, a steerable robotic tool designed to facilitate precise navigation to the ventral and lateral epidural space. Cosserat rod framework is employed to establish the relationship between tendon actuation forces and the robot's overall shape. The effects of gravity, as an example of an external load, are investigated and implemented in the model and simulation. The experimental results indicate RMSE values of 1.76mm, 2.33mm, 2.18mm, and 1.33mm across four tested prototypes. Based on the helical shape of the ExoNav upon actuation, it is capable of performing follow-the-leader (FTL) motion by adding insertion and rotation DoFs to this robotic system, which is shown in simulation and experimentally. The proposed simulation has the capability to calculate optimum tendon tensions to follow the desired FTL paths while gravity-induced robot deformations are present. Three FTL experimental trials are conducted and the end-effector position showed repeatable alignments with the desired path with maximum RMSE value of 3.75mm. Ultimately, a phantom model demonstration is conducted where the teleoperated robot successfully navigated to the lateral and ventral spinal cord targets. Additionally, the user was able to navigate to the dorsal root ganglia, illustrating ExoNav's potential in both motor function recovery and pain management.

Problem

• spinal cord stimulation
• continuum robot
• follow-the-leader
• epidural space
• steerable robotic tool

Innovation

• tendon-driven continuum robot
• follow-the-leader motion
• Cosserat rod modeling
• spinal cord stimulation
• programmable navigation