Six Degrees Of Freedom Electromagnetic Tracking System

As a positioning device, six degrees of freedom electromagnetic tracking systemis widely used in many fields, such as augmented reality, portable laser scanner,computer-aided medical systems, minimally invasive surgery, medical teaching andmedical images. With the development of positioning technology, the communicationbetween people and computers become more flexible. Electromagnetic trackingsystem is unobstructed and flexible, so it is more widely used than other positioningsystems. In this paper an electromagnetic tracking system was designed. The drivingsignal of this system is an alternating square wave, so eddy current can be real-timeremoved. Furthermore, the positioning algorithm was improved.In this paper, the magnetic field of circular coil model and square coil model werecompared, it proved that the square coils can be approximated as a magnetic dipole.The relative error between an actual coil and equivalent dipole as a function ofdistance from the coil along the z-axis is given.The Ansoft Maxwell finite element analysis software was used for simulation ofcoils. Coils current, magnetic field distribution and Vector were concluded as a result,which provided a theoretical basis for the tracking system.The algorithms of Euler angle and quaternion method were compared analyzedwith anisotropic parameters. Based on anisotropic parameter, the position and attitudeparameters of the quaternion method were simultaneously solved. It simplified thesolving steps and reduced solution time.The hardware of electromagnetic tracking system was designed, including thetransmitting coils and the signal generating circuit, the driving circuit, themicrocontroller, and the receiving sensor, an amplifier circuit, A/D converter circuit.The magnetic induction of coils without or with ferrite core was compared and thehollow coils were chosen. Combining the characteristics of the receiving sensor andtransmitting signals, and the final receiving value was calculated.Finally, waveform diagrams of the experimental data were shown. The algorithmflowcharts of the three methods were given, and the calculated results of the severalalgorithms were compared.In this paper, Because of Alternating square wave, interference of outside the magnetic field and earth magnetic field can be real-time removed. The coil model wasanalyzed and simulation for the electromagnetic tracking system provided theoreticalsupport for the system.