| Electromagnetic tracking technology is particularly suitable for indoor environments. Because it hashigh precision and has no occlusion problem. Electromagnetic tracking system usually consists oftransmitter, receiver and processor. In the system, the coil carrying on current is often used aselectromagnetic positioning instrument. The coupled signal between receiver and transmitter is closelyrelated to the position and direction of the receiver. Therefore, the coupling signal can be extracted forpositioning work. But coupling signal is sensible to noise, it need to be amplified and filtered in highquality. Electromagnetic tracking technology generally uses magnetic dipole model which contains fivepositional parameters. It also uses a nonlinear algorithm to solve the target location equations. Therefore,the magnetic field model around the emitting coil, the signal generating and acquisition circuits, and thelocalization algorithm directly affects the positioning accuracy of the system.In order to realize the tracking of indoor moble robot in a wide range, an electromagnetic trackingsystem is correspondingly designed based on embedded system ARM(STM32). This system includes signaltransmitting unit, multi-axis coil receiving sensing unit and processor unit. Firstly, the system was realizedbased on STM32F103, an ARM micro-controller of ST, as well as signal processing circuits for amplifyingand filtering. Sinusoidal signal is amplified through the power amplifier circuit to stimulate emitting coil,and a specific frequency magnetic field is built. Three analog signals are obtained by amplifying andfiltering the signals sensed by three-axis sensor coil. Then, the analog-to-digital converters ofmicro-controller sample data. After data processing, calculation results are displayed in real time on theLCD screen.Secondly, we study the magnetic field model of a dipole and a coil carrying current and compar thesimilarities and differences between them. It is obtained that the model of a coil carrying current can bereplaced with that of a dipole in a certain case. After that, the magnetic dipole model is adopted forpositioning calculations based on Faraday’s law of electromagnetic induction. LM algorithm is used tosolve the nonlinear equations of electromagnetic tracking. In the case for its moving in the plane, ananalytic algorithm is deduced to solve the tracking equations.Lastly, a lot of simulations and experiments are conducted with LM algorithm and analytic method.The accuracy and real-time performance of this system was verified in the space tracking experiment. Theresults show that the moving objects can be localized precisely within the range of several meters betweenthe transmitter and the receivers in real time. |
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