Magnetoquasistatic Position and Orientation Tracking
Matthew Trotter (Disney Research Pittsburgh) Joshua Griffin (Disney Research Pittsburgh) Dan Stancil (North Carolina State University) David Ricketts (North Carolina State University) Darmindra Arumugam (Jet Propopulsion Laboratory) Michael Sibley (Tait Towers) Daniel Kotovsky (University of Florida)
The goal of this project is to determine the position and orientation of a light-weight, low-frequency transmitter using quasistatic magnetic fields in environments where line-of-sight occlusions and multipath propagation reduce the accuracy of conventional optical and high-frequency wireless tracking systems. This technology could be used in many applications including athlete tracking, video game control, and handheld device localization; however, the current application is tracking an American football. A small transmitter integrated into the football induces a quasistatic magnetic field that is sensed by receivers stationed around the field. With at least five unique measurements of the magnetic field, the three-dimensional (3D) position and orientation of the ball can be determined using complex image theory to account for ground effects. This system has several advantages including immunity to multipath propagation, unaffected by line-of-sight occlusions caused by groups of people, and minimum complexity on the person/object to be tracked.
An instrumented American football with the outer leather covering removed. A class-E oscillator (transmitter) and loop antenna are shown.
A cutaway of an American football showing the proposed location of the embedded loop antenna, transmitter circuit, and battery. These components are placed between the inner air bladder and the outer leather covering and are held in place by the pressure of the air bladder.
Eight loop antennas are positioned around one end of an American football field.
Selected frames from a run play are shown to compare the true path of the ball (yellow line) to the estimated path of the ball (orange line). The true position of the ball was visually estimated by the position of the player’s feet.
The final frame from a run play comparing the true path of the ball (yellow line) to the estimated path of the ball (orange line). The true position of the ball was visually estimated by the position of the player’s feet.
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