Wireless Tracking Technology And Its Application Based On Magnetic Sensor Array

The location and orientation of the wireless capsule endoscope inside the human body is very important for the gastrointestinal examination. To satisfy the requirement of the position and gesture information of endoscope, a magnetic localization and orientation system is built. The magnetic location is using the magnetic permeability of human body very close to that of the air. Compared with GPS positioning, visual positioning, ZigBee positioning and sound positioning, it has the advantages of high precision, simple operation and harmless to the human body.In this paper, a localization algorithm for tracking a magnet inside the capsule endoscope by 3-axis magnetic sensors array is proposed. In the algorithm, we use a linear algorithm to obtain the parameters of initial position. These parameters are used as the initial guess of the localization parameters in the nonlinear localization algorithm, and the nonlinear algorithm searches for more appropriate parameters that can minimize the objective error function.The system is made of a magnetic sensors array collecting the intensity of the magnetic field from a magnet in the capsule. In this paper, we try to optimize the sensor arrangement in the 3D space around the human body, to improve the tracking precision. Different sensor arrangement schemes are evaluated, and the tracking accuracy can be significantly increased with the appropriate arrangement.Magnetic location circuit are designed in this paper, which is composed of Honeywell 3-axis magnetic sensors, high performance analog multiplexers, low noisy amplifiers, 16 bits A/D converter, and ARM controller. In order to improve the accuracy of the sensor output, bias adjustment circuit and set/reset circuit are designed.