Magnetic Localization Method of Capsule Endoscope Based on Hybrid Model

Magnetic localization is an effective method for obtaining the pose of a wireless capsule endoscope (WCE) because it is able to provide the position and orientation of the magnet in places where visual methods are not available. In magnetic positioning, the magnetic dipole model is often used to calculate the magnetic field of a magnetic source. However, the magnetic field calculated by the magnetic dipole model introduces positioning errors when a permanent magnet is used as the magnetic source and the size of the permanent magnet cannot be ignored. In this article, a WCE localization method was proposed based on the combination of the magnetic dipole model and the analytical model. A cylindrical magnet was mounted in the WCE. The magnetic field of the magnet was calculated using the magnetic dipole model and the rough position of the magnet was estimated using the particle swarm optimization (PSO) algorithm; then, the magnetic field of the magnet was described using the analytical model and the estimated result of the PSO algorithm was used as the initial value of the Levenberg–Marquardt (L–M) algorithm to calculate the pose of the WCE. Experiments on static and dynamic localization of magnet were carried out in the localization system. The experimental results verified the feasibility of the proposed method.