Position and Orientation Measurements using Magnetoquasistatic Fields

The wireless position tracking problem is of increasing relevance to the society today, owing to applications such as navigation, security, and asset tracking. Despite numerous technological advances, radio based position location systems such as global positioning systems (GPS), ultrawide band (UWB) systems, and radio frequency identification (RFID) systems suffer reduced performance in non-line-of-sight (NLoS) environments and when in proximity to lossy dielectric bodies. These drawbacks limit their use for some applications, such as contact sports, in which the line-of-sight (LoS) to the device may be blocked by player’s bodies and the device held close to their body. A promising solution for position tracking in the presence of lossy dielectric bodies is the use of low-frequency, quasistatic magnetic fields instead of propagating radio waves. Because most lossy dielectric bodies such as the human body interact weakly with magnetoquasistatic fields, proximity to and blockage of the LoS by a person or groups of people should not significantly perturb the magnetoquasistatic field, leading to obvious benefits when used for wireless position tracking. In this dissertation, we begin by showing that magnetoquasistatic fields are an excellent technique to measure distances between an emitter and receiver. When used with multiple receivers or emitters, this technique can be generalized to twoand three-dimensional position and orientation measurements. By measuring fields at short intervals (or continuously), the measured positions and orientations provide an effective tracking of the emitter or receiver, and in turn the tracking of any object mounted onto the emitter or receiver. Since the emitter is close to a conducting half-space (earth), secondary fields due to induced eddy currents in this half-space must be considered. We present an experimental demonstration of complex image theory, and show that it can be used to describe the secondary fields created due to the induced eddy currents in the earth. A system to enable position and orientation measurement and tracking, close to the half-space, is designed, built, tested, and used for the one-, two-, and three-dimensional case, with application to the position and orientation tracking of an American football during game-play. By conducting a series of measurements, we demonstrated a onedimensional distance measurement accuracy of better than 24 cm (55 cm) for up to about 34 m (50 m), and a two-dimensional average and median geometric position error of 0.73 m and 0.57 m, respectively. By conducting three-dimensional position and orientation experiments, we found a three-dimensional average and median geometric position error of about 0.5-0.8 m, an average azimuthal orientation (φ) error of about 2-3, and an average inclination orientation (θ) error of about 8-10.