Darmindra D. Arumugam

Decoupled Range and Orientation Sensing in Long-Range Magnetoquasistatic Positioning

A technique using magnetoquasistatic fields has been shown to enable accurate ranging in non-line-of-sight environments. Due to the nonlinear field coupling equations, the technique suffers when extended to 2-D and 3-D due to the coupling of range and orientation errors combined with the nonlinear convergence of the solution. Using a 2-axis transmit-receive concept, a theory is presented to decouple range and orientation. The results are linear orientation-invariant ranging and linear range-invariant orientation sensing. Measurements inverted using the decoupled equations demonstrate peak orientation-invariant range errors of 0.2-0.4 m for a range of up to over 40 m, and peak range-invariant orientation errors of 1°-7°.

Magnetic Field-Based Positioning Systems

This paper provides an introductory survey on the various systems that exploit magnetic fields for positioning. Such systems find applications in those scenarios, both indoors and outdoors, where global navigation satellite systems are not available or fail to provide information with the needed accuracy. While the main idea of using electromagnetic fields to provide position information dates back to the past century, new application-led research on this topic has emerged in recent years. Results have expanded the application range of magnetic positioning technologies and form now a domain of knowledge that enables realization of positioning systems applicable to indoor and outdoor environments. This paper provides the main characteristics of different positioning systems with focus on those solutions that are based on low-frequency magnetic fields. Some background theory is presented and positioning results from the literature are analyzed and compared.

An active position sensing tag for sports visualization in American football

Remote experience and visualization in sporting events can be significantly improved by providing accurate tracking information of the players and objects in the event. Sporting events such as American football or rugby have proved difficult for camera- and radio-based tracking due to blockage of the line-of-sight, or proximity of the ball to groups of players. Magnetoquasistatic fields have been shown to enable accurate position and orientation sensing in these environments [1]-[3]. In this work, we introduce a magnetoquasistatic tag developed for tracking an American football during game-play. We describe its integration into an American football and demonstrate its use in game-play during a collegiate American football practice.

Full-wave exact integral solutions of a current carrying loop in a general half-space

The full-wave exact integral solutions of a current carrying loop immersed in a general half-space is presented. The result is an eigenfunction reflection coefficient that is perfectly symmetric with respect to the interchange of the half-space mediums, which is in contrast to the traditional form of Sommerfelds original solution for the current loop above earth.

Magneto-Quasistatic Tracking of an American Football: A Goal-Line Measurement [Measurements Corner]

An American football was tracked using a long-range magneto-quasistatic position and orientation measurement system. A low-weight emitter that emitted a low-frequency quasistatic magnetic field was embedded within an American football. The emitter weighed a total of 26.5 g, which was within the manufacturing tolerance of an American football, and did not alter the dynamics of the ball. Measurements of a person carrying the football along the goal line of an American football field are described, along with a description of the construction of the magneto-quasistatic tracking system. The technique demonstrated measurements with a distance accuracy of 15 cm and an azimuthal orientation accuracy of 2.45° for measurements conducted along the goal line of an American football field.

Passive distance sensing through measurements of mode splitting in coupled magnetic resonators

The monostatic backscattered magnetoquasistatic field measured at the terminals of a resonant loop due to a nearby resonant loop can be modeled using coupled mode theory. Due to close proximity of the monostatic resonant loop and the nearby resonant loop, the backscattered energy is distributed over a set of two orthogonal modes of positive energy that can be described using classical coupled mode theory. The center frequencies of the two orthogonal modes are separated by an amount known as the coupled mode frequency split, which is strongly dependent on coupling and thus distance. Measurements of this frequency split is inverted for passive distance measurements with an RMS distance error of 1.5 cm for distances up to 1 m.

Effect of measurement noise on magnetoquasistatic position and orientation sensing

Magnetoquasistatic position and orientation errors due to measurement noise are quantitatively studied using theoretical field equations and added Gaussian noise.

Localization in planetary sub-surfaces using deep-sub-wavelength magnetoquasistatics

We propose a magnetoquasistatic (MQS) field-based technology that would enable localization and communication from surface to cave exploring robots. In this article, we focus on the localization aspect of the technology. The technique requires a minimum of two nodes, of which one is mobile and can be located in the sub-surface, whereas the second is located at a fixed location above the over-burden. To simplify the proof-of-concept, we use a fixed transmitter device located above the ground, and a mobile receiver device located within a cave system, below the over-burden. By sensing and inverting the MQS field detected at the receiver, we were able to solve for positions of the mobile receiver device.

Through-the-wall indoor tracking and navigation using deep-sub-wavelength magnetoquasistatics

Recent progress in magnetoquasistatic field-based techniques have enabled decoupled and linear solutions for position and orientation sensing in non-line-of-sight environments at short to long ranges above ground. By utilizing the deep-sub-wavelength regime of the MQS source, we describe a method to enable position sensing in the indoor environment. The technique enables accurate positioning of a mobile device within a few skin-depths into a heavy multi-path building environment.

Low-Latency 2d non-line-of-sight positioning using single-anchor magnetoquasistatic systems

Recent progress in magnetoquasistatic (MQS) positioning theory and techniques have resulted in short to long range two-dimensional (2D) positioning using a single-anchor device — a single fixed base-station device that enables 2D positioning of a mobile device, not relying on tri-angulation/lateration. These recent works demonstrate the ability to determine the position of a mobile device in 2D space over ranges of up to many tens of meters and in non-line-of-sight environment, due to use of MQS fields. One additional advantage of the recent theory and technique is that the solutions for range, azimuthal-direction, and orientation of the device are decoupled and can be solved in a low-latency environment. In this article, we demonstrate a low-latency solution for MQS positioning in a large 2D space.