Leveraging Three Orthogonal Magnetic Field Sources for Localization of A Magnetic Capsule Endoscope with Unique Solution

This paper presents a novel localization method for magnetically actuated capsule endoscopy that uses three orthogonal magnetic field sources external to the capsule, and three magnetic field sensors and an inertial measurement unit (IMU) internal to the capsule to estimate the 6-DOF pose of the capsule with unique solution. One permanent magnet and two electromagnetic coils are used as the external magnetic field sources to generate static and time-varying magnetic fields with different frequencies, and their measurements from raw sensor readings are separated and extracted based on the Fast Fourier Transform (FFT) algorithm. Furthermore, we analyse the issue of multiple solutions that may occur when less than three orthogonal magnetic sources are used for localization. We preliminarily validate the proposed localization approach in simulation. Our method can achieve an average localization accuracy of 1 mm, 1° at an update rate of 150 Hz in a 0.2 x 0.2 x 0.2 m³ workspace below the actuator in the presence of sensor measurement noises and time delays, which shows its potential to be used for closed-loop control of the capsule.

I. Introduction

Wireless capsule endoscopy (WCE) is a promising technique for the imaging of the gastrointestinal tract, which can overcome the drawbacks of conventional endoscopy, such as long procedural duration, the difficulty of use, and pain caused [1]. However, existing WCE products cannot be actively controlled in the human body, which limits the use of the device in the long examination time and low flexibility. Several groups have been working on the simultaneous magnetic actuation and localization (SMAL) of WCE to realize active control of the internal capsule robot with an external permanent magnet [2]–[5].