Pokeball: A 3D positioning system using magnetism

Abstract

We present a 3D positioning system called Pokeball, which uses a single-source magnetic sphere. The system comprises three mutually orthogonal coils and an Arbitrary Waveform Generator (AWG) to generate the designated signals. By applying Frequency Division Multiplexing (FDM), Pokeball generates two rotating magnetic fields with different frequencies of phase-quadrature current signals. The positioning object is equipped with a three-axis magnetoresistive sensor that measures the strength of the magnetic field and extracts the results into two signals with different frequencies. The phases of the two signals are used to determine the elevation and azimuth angles, while the amplitudes of the signals are used to calculate the distance between the source and the object. Then, based on the calculations, the location of the object is determined. The results of a comprehensive set of experiments demonstrate that Pokeball can achieve an accuracy of less than 40 cm for positioning errors in its effective positioning range. Moreover, Pokeball does not require site surveys, and it is robust against radio interference and environmental obstructions. Our approach has a great deal of potential for use in a wide range of applications, such as mobile systems, wearable computing devices, and location-based applications, where an instantaneous and accurate indoor 3D positioning system is essential.