Mitigating Singularities in Control of Magnetic Capsule Endoscopes Using a Novel Nested Electromagnetic Coil System

Abstract

Magnetic actuation systems that utilize external electromagnetic coils present a promising approach for controlling untethered smallscale robots, notably in medical applications. However, these systems frequently experience control singularities that significantly affect the robots’ stability in specific areas of the workspace. In order to effectively mitigate these control singularities, this paper introduces a closed-loop control method using a novel nested electromagnetic coil system, leveraging finite element analysis-based magnetic field data and singularity solvers. The electromagnetic system is a 12-coil system with variable outer radius individually addressable coil stacks (VORIACS). Here, we experimentally evaluate the method for closed-loop trajectory tracking of a soft magnetic capsule endoscope (PillCam™) inside the VORIACS system at different magnetic field orientations. The results demonstrate that the VORIACS system with a singularity solver reduces root mean square position tracking errors of the PillCam™ by 46% to 50% and orientation tracking error by 41% to 42% compared to a standard 4-coil system. We further manipulate the PillCam™ for tracking a medical application-inspired complex trajectory, showcasing the system’s potential in precise control of magnetic devices for medical use.