Magnetic Tracking System with Capability of Automatic Magnetic Moment Measurement

Magnetic tracking technologies have a promising application in detecting the real-time position and attitude of a capsule endoscope. However, most of them need to measure the magnetic moment of a permanent magnet (PM) embedded in the capsule accurately in advance, which can cause inconvenience to practical application. To solve this problem, this paper proposes a magnetic tracking system with the capability of measuring the magnetic moment of the PM automatically. The system is constructed based on a 4 × 4 magnetic sensor array, whose sensing data is analyzed to determine the magnetic moment by referring to a magnetic dipole model. With the determined magnetic moment, a method of fusing the linear calculation and Levenberg-Marquardt algorithms is proposed to determine the 3D position and 2D attitude of the PM. The experiments verified that the proposed system can achieve localization errors of 0.48 mm, 0.42 mm, and 0.83 mm and orientation errors of 0.66°, 0.64°, and 0.87° for a PM (∅10 mm × 10 mm) at vertical heights of 5 cm, 10 cm, and 15 cm from the magnetic sensor array, respectively.