6-D Spatial Localization of Wireless Magnetically Actuated Capsule Endoscopes Based on the Fusion of Hall Sensor Array and IMU

This paper introduces a novel 6 degrees of freedom (6-D) spatial localization for wireless magnetically actuated capsule endoscopes (WMACEs) based on multi-sensor fusion. A WMACE integrated with an inertial measurement unit (IMU) sensor is developed, which enables wireless transmission of video and sensor data. A Hall sensors array is designed to measure the magnetic field generated by the WMACE for acquiring its 6-D pose under external magnetic actuation. The angle between the direction of the WMACE's magnetic moment and the gravity direction measured by the IMU is set initially as 90°, which, based on multi-sensor data fusion, solves the problem that the rotation around the magnetization axis cannot be acquired by Hall sensors array and that the rotation around the gravity axis cannot be measured by the IMU. In addition, eight pose detection algorithms and two data-fusion filters are experimentally compared for analyzing and selecting the optimal approach for the 6-D localization of the WMACE. The experimental results indicate a high accuracy for 6-D pose detection, with a mean absolute error of 1.463 mm for 3-D position and 0.419° for 3-D orientation, with the height between the capsule and the Hall sensor array ranging from 25 mm to 72 mm.