Experimental Demonstration of Complex Image Theory and Application to Position Measurement

Arumugam, Darmindra D.; Griffin, Joshua D.; Stancil, Daniel D.

doi:10.1109/lawp.2011.2136370

Cited by 38 publications

(46 citation statements)

References 10 publications

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“…The use of higher frequencies necessitates the use of complex image theory to account for induced eddy-currents within the nearby earth. By using complex image theory in our previous work, we showed a one-dimensional peak and RMS error of 23.01 and 11.74 cm, respectively, for distances between 1.3 and 34.2 m [1].…”

Section: Introductionmentioning

confidence: 79%

“…These previous measurements where limited as they were primarily conducted to determine the effect due to various frequencies, were conducted only for circumferential field coupling, and performed with a small group of 4 people. Our previous work is further limited due to a very short distance between the emitter and receiver, and that the group is only positioned to block the LoS and not located to surround the emitter or receiver [1].…”

Section: Introductionmentioning

confidence: 99%

“…Recently, a position and orientation measurement technique using magnetoquasistatic fields and complex image theory was shown to enable long range, one-dimensional [1] and twodimensional position [2] and orientation [3] measurements. In this technique, an electrically-small current loop was used to generate low-frequency magnetoquasistatic fields by using a frequency of approximately 360 kHz.…”

Section: Introductionmentioning

confidence: 99%

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Experimental study on the effects of groups of people on magnetoquasistatic positioning accuracy

Arumugam

Griffin

Stancil

et al. 2012

Proceedings of the 2012 IEEE International Symposium on Antennas and Propagation

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Position and orientation measurements have been demonstrated, recently, using low-frequency magnetoquasistatic fields and complex image theory for distances up to 50 m [1].The key motivation for using magnetoquasistatic fields is to enable accurate estimation of an object's position and orientation when near weakly conducting dielectric obstacles, e.g., groups of people. An example application is tracking an American football during game-play [1]. In this paper, we present measurements using the magnetoquasistatic technique to show that the presence of a large group of 25 people introduces a peak distance error of less than 4.5 cm for an emitter-receiver distance of 10 m. I. INTRODUCTIONRecently, a position and orientation measurement technique using magnetoquasistatic fields and complex image theory was shown to enable long range, one-dimensional [1] and twodimensional position [2] and orientation [3] measurements. In this technique, an electrically-small current loop was used to generate low-frequency magnetoquasistatic fields by using a frequency of approximately 360 kHz. This frequency is somewhat higher than conventional magnetic tracking techniques, which operate below 4 kHz [4], thus providing a much larger signal-tonoise ratio (SNR) and hence increased range. The use of higher frequencies necessitates the use of complex image theory to account for induced eddy-currents within the nearby earth. By using complex image theory in our previous work, we showed a one-dimensional peak and RMS error of 23.01 and 11.74 cm, respectively, for distances between 1.3 and 34.2 m [1].Because low-frequency magnetoquasistatic fields are not strongly perturbed by nearby weakly conducting dielectric bodies, this technique performs well in non line-of-sight (LoS) environments, such as around groups of people. To verify the insensitivity, we conducted preliminary measurements in [1] with a small group of people blocking the LoS between a vertical emitting and receiving loop with a circumferential field coupling. The result of this measurement showed a peak error of 1.1 cm for a frequency of 400 kHz, with an increase in measured error for higher frequencies and a peak error of 53 cm for a frequency of 13 MHz [1]. These previous measurements where limited as they were primarily conducted to determine the effect due to various frequencies, were conducted only for circumferential field coupling, and performed with a small group of 4 people. Our previous work is further limited due to a very short distance between the emitter and receiver, and that the group is only positioned to block the LoS and not located to surround the emitter or receiver [1].In this paper, we present measurements for a large group of 25 people over a much longer distance (10 m) with two different

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Section: Introductionmentioning

confidence: 79%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Experimental study on the effects of groups of people on magnetoquasistatic positioning accuracy

Arumugam

Griffin

Stancil

et al. 2012

Proceedings of the 2012 IEEE International Symposium on Antennas and Propagation

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“…Radio Frequency (RF) signals [2], sound waves [3], optical signals [4] or magnetic fields [5] have been used to determine location. By measuring the distance of the object to three or more known reference points, the object position can be estimated.…”

Section: A Existing Indoor Localization Systems and Their Challengesmentioning

confidence: 99%

A battery-free RFID-based indoor acoustic localization platform

Zhao

Smith

2013

2013 IEEE International Conference on RFID (RFID)

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Abstract-The ability to precisely localize RFID tags with low latency and low cost is desirable for applications such as inventory, asset tracking and robotic-manipulation of tagged items. However, because of multipath propagation effects, traditional RFID positioning methods based on RF Received Signal Strength Indication (RSSI) have limited accuracy (meter-scale) or require large numbers of reference tags and readers, which increases both latency and cost. Acoustic localization systems can be more precise, but typically require a battery-powered sensor platform, which both increases tag size, weight and limits tag lifetime. In addition, conventional acoustic localization systems are not integrated with existing RFID infrastructure. This paper presents a working prototype of a RFID-based system that localizes a custom battery-free, EPC Gen2-compatible UHF tag. The system uses the RFID communication channel for synchronization and inventory, and acoustic propagation delays for distance measurement.The system consists of a custom passive tag (WISP) with acoustic tone-detector that receives and times ultrasound signals, an off-the-shelf EPC Gen2 UHF RFID reader, and an array of ultrasonic beacons. By measuring the Time of Arrival (ToA) of the ultrasound, the passive WISP tag can determine its location relative to the ultrasonic beacons. Time synchronization between the tag being tracked and the ultrasonic beacons is accomplished by using a "spy WISP." The spy WISP listens to the RFID communication traffic between the reader and the tracked tag and triggers the ultrasonic beacons in a fashion that is synchronous with the RFID traffic.The localization performance of the prototype is characterized, and the tradeoffs among power consumption, precision, latency and range are discussed.

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“…For example, magnetic tracking has been used for eye tracking to diagnose Ménière's disease , positioning of wireless capsule endoscopes within the gastro-intestinal tract (Yang et al 2009), real-time organ-positioning during radiotherapy of cancer tumors (Iustin et al 2008), catheter tracking (Krueger et al 2005;Biosense Webster 2011), monitoring of heart valve prostheses (Baldoni and Yellen 2007), tongue movement tracking (Gilbert et al 2010;Wang et al 2013), tracking of lung segment movements (Leira et al 2012), and positioning of bone-embedded implants (Sherman et al 2007). Examples of non-medical applications of magnetic tracking include head tracking for helmet-mounted sights in military aircraft (Raab et al 1979), underground drilling guidance (Ripka et al 2012), augmented and virtual reality (Liu et al 2004), and tracking of the ball during an American football game (Arumugam et al 2011).…”

Section: Introductionmentioning

confidence: 99%

Convex optimization of measurement allocation for magnetic tracking systems

2016

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Magnetic tracking is a popular technique that exploits static and lowfrequency magnetic fields for positioning of quasi-stationary objects. One important system design aspect, which substantially influences the performance of the tracking system, is how to collect as much information as possible with a given number of measurements. In this work, we optimize the allocation of measurements given a large number of possible measurements of a generic magnetic tracking system that exploits time-division multiplexing. We exploit performance metrics based on the Fisher information matrix. In particular, the performance metrics measure worstcase or average performance in a measurement domain, i.e. the domain where the tracking is to be performed. An optimization problem with integer variables is formulated. By relaxing the constraint that the variables should be integer, a convex optimization problem is obtained. The two performance metrics are compared for several realistic measurement scenarios with planar transmitter constellations. The results show that the worst performance is obtained in the most distant parts of the measurement domain. Furthermore, measurement allocations optimized for worstcase performance require measurements in a larger area than measurement allocations optimized for average performance.

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Experimental Demonstration of Complex Image Theory and Application to Position Measurement

Cited by 38 publications

References 10 publications

Experimental study on the effects of groups of people on magnetoquasistatic positioning accuracy

Experimental study on the effects of groups of people on magnetoquasistatic positioning accuracy

A battery-free RFID-based indoor acoustic localization platform

Convex optimization of measurement allocation for magnetic tracking systems

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