Highly Accurate Ultrasonic Positioning and Tracking Systems

240 Pages·2015·3.58 MB·English

Highly Accurate Ultrasonic
Positioning and Tracking Systems
by
Mohammad Omar Khyam
A thesis submitted in fulfilment of the requirements
for the degree of
Doctor of Philosophy
SCIENTIA
MANU ET M E N T E
School of Engineering and Information Technology
The University of New South Wales
Canberra, Australia
August, 2014
Originality Statement
‘I hereby declare that this submission is my own work and to the best of my
knowledge and belief, it contains no material previously published or written by
another person, nor material which to a substantial extent has been accepted for
the award of any other degree or diploma at UNSW or any other educational
institution, except where due acknowledgement is made in the thesis. Any contri-
bution made to the research by colleagues, with whom I have worked at UNSW
or elsewhere, during my candidature, is fully acknowledged. I also declare that
the intellectual content of this thesis is the product of my own work, except to
the extent that assistance from others in the project’s design and conception or in
style, presentation and linguistic expression is acknowledged.’
Signed.............................................
Date........................
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Dedication
My late father; the best man that I have ever known.
Not forgetting my mother, the living encouragement for me
My wife Mutmainnah Hasib, who is constantly very supportive to all my plans
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Acknowledgements
“Patience is not passive waiting. Patience is active acceptance of the process
required to attain your goals and dreams.”–Ray Davis
Thanks to
• God, the Almighty, Alhamdulillah, for bestowing His unlimited Mercy and Bless-
ings on me to accomplish this task.
• My supervisor, Associate Professor Dr. Mark Pickering, for his continuous guid-
ance and encouragement throughout my PhD journey. His energy and enthusiasm
still continue to amaze me. Whenever I have felt down, I could simply knock on
his door and discuss different issues. During the countless discussions I had with
him, I always felt that I was his only student, although he had about ten students.
He has always given me the courage to continue and see my work until the end.
I have learnt many things from him, which will indeed be useful for my future
career. Without his assistance this thesis would not have been possible.
• My co-supervisor, Senior Lecturer, Dr. Andrew Lambert, for his help and sup-
port throughout my PhD candidature.
• Dr. Jahangir Alam, for his valuable directions in my research and for his closest
guideline.
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• Denise Russel for proofreading my thesis.
• The University of New South Wales for supporting me with Tuition Fee Remis-
sion Scholarship, Completion Scholarship and Post-graduate Research Support
Schemes.
• All the UNSW, Canberra, school office members for their cordial assistance
throughout my research journey.
• Dr. Apel Mahamud, as my local guardian in Australia.
• Younger, elders, and friends in the University and community who have made
my life in the Australian Capital Territory fruitful and pleasurable.
• My house mates Habibullah Habib, Md Asikuzzaman and Mohiuddin Ahmed
for their support like family members.
• Mutmainnah Hasib, my wife, for being so understanding about the life of a
graduate student. I will happily support her in whatever she decides to pursue for
the rest of our lives.
• My brother and sister, for giving me their unconditional support.
• The amazing lady my mother, the living encouragement for me. She has always
been with me with her prayers and well wishes.
• My late father, for teaching me the value of education. He would have been the
happiest person today, if he would have been alive. May Allah rest him in peace
and place him in heaven!
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Abstract
Localizationis the process of determining thecurrent locationof a target(s) within
given coordinates using a location system. The localization process has two main
phases: firstly, the measurement phase, that establishes a relationship in terms of
the distance and/or angle between the targets(s) to be localized and the system
infrastructure; and secondly, the positioning phase, that exploits the measured in-
formationtocalculatetheabsoluteorrelativelocationcoordinatesofthetarget(s).
So far the most widely used positioning system is the Global Positioning System
(GPS). However, in a GPS system, the receiver requires line-of-sight (LOS) recep-
tionfromdifferent satellites, which isusuallydifficult toobtainindoors. Therefore,
as there is a need for alternate location systems in these GPS-obstructed environ-
ments, indoor positioning has drawn considerable attention from both academia
and industry. Indoor environments, which are characterized by obstacles such as
walls, floors, ceilings, and furniture, provide countless opportunities for a wide
range of applications requiring different levels of accuracy. High-accuracy applica-
tions, such as gait analysis, usually use optical motion capture systems (MCSs),
which are cost-prohibitive for many users, and also require complex arrangements
of expensive equipment. In addition, they are responsive to changes in lighting
and shadow. Therefore, with the aim of overcoming these limitations, ultrasonic
positioning systems (UPSs) have drawn considerable attention. Usually, a narrow-
band UPS uses either a single tone or narrowband chirp signal in the measurement
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phaseinwhichaccurateestimationsofdistance, throughtime-of-flight(TOF)tech-
niques, are fundamental. Generally, cross-correlation, which produces a peak at
the time delay between a transmitted and received signal, is considered the opti-
mal TOF estimation technique. Since their accuracy depends on the width of the
correlation peak, which is inversely proportional to the signal’s bandwidth, these
systems can only be said to be highly accurate if the reflected or multipath signal
at the receiver is separated in time by more than the width of the correlation peak;
otherwise, errors are introduced into the system. To improve the accuracy of such
systems, the bandwidth of the signal must be increased, which increases the cost
of the system. In the first part of this thesis, a new phase-correlation-based TOF
estimation technique, that uses a narrowband chirp signal working in a closely
spaced multipath environment, is proposed. In this system, the correlation peak
becomes narrower byvirtually, rather thanphysically, increasing thesignal’sband-
width, which reduces system cost. The performance of the proposed method is
evaluated experimentally.
As the correlation technique finds matches between transmitted and received
signals, both signals need to be stored at the receiver, which increases hardware
cost and computational complexity. In the second part of this thesis, firstly,
to solve the limitations of the correlation technique, a narrowband orthogonal
frequency division multiplexing (OFDM)-based TOF technique is introduced in
which the TOF is estimated based on a pre-defined threshold. The proposed tech-
nique has advantages in terms of computational complexity and hardware cost
when compared to the correlation technique, as in this approach TOF estimation
decisions are made using threshold detection and only the received signal needs
to be stored. An additional feature of this technique is that it has good noise
cancelation properties. In the positioning phase, existing UPSs generally use the
lateration algorithm to obtain a target’s location information. For the accurate
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positioning of reference points in an indoor environment, it is logistically simpler
if they are installed in a fixed plane. This means that the distances between the
reference points will usually be smaller than the distances between the reference
points and the target(s). In this configuration, when lateration is used for posi-
tioning target(s), the surfaces of the spheres centered at the reference points will
be almost parallel. This results in larger errors in the positions of the intersect-
ing points of the spheres for directions tangential to the surfaces of the spheres
than for those normal to these surfaces. This phenomenon is known as dilution of
precision (DOP). To overcome this DOP problem, a steepest descent optimization
algorithm is proposed. The proposed algorithm places the reference points at po-
sitions which best correspond to their measured distances from the target utilizing
a three-dimensional (3D) rigid-body transformation. An additional feature of this
algorithm is that it allows errors to be ignored in the distance measurements of the
receivers corresponding to one complete cycle of the transmitted signal. Experi-
mental results demonstrate the improvement obtained by the proposed methods
over the traditional lateration based positioning systems that use cross-correlation
techniques with a transmitted chirp signal.
Finally, when UPSs use single tone or narrowband chirp signals, they cannot
simultaneouslylocalizemultipletargetsduetosignalinterference. Thisisgenerally
overcome by either using the time division multiplexing (TDM) technique, which
reduces thepositioning updaterate, or introducing a broadbandtransducer, which
increases system cost. In the last part of this thesis, the proposed OFDM-based
steepest descent optimization algorithm is first extended to handle multiple target
positioning utilizing the orthogonal property of the OFDM signal. Since TDM
techniques and broadband transducers are not required, this system can maintain
the single target system update rate without increasing system cost. For the
positioning of a moving target(s), most of the existing localization systems use the
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matched filtering technique, where a bank of correlators is used to estimate the
Doppler shift associated with the target’s movement. This requirement increases
computational complexity and system cost. The proposed OFDM-based steepest
decent optimization algorithm is further extended for tracking a moving target.
The Doppler shift is estimate by introducing a pilot carrier to the transmitted
OFDM signal. As it does not require matched filters to estimate the Doppler
shift, the proposed system does not require extra computational complexity or
system cost. The accuracy of the proposed system is compared with an optical
motion capture system, Vicon, and it is shown to have the same order of precision
while incurring less cost and complexity.
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Contents
Declaration i
Dedication ii
Acknowledgements iii
Abstract v
List of Figures xv
List of Tables xix
List of Abbreviations xx
1 Introduction 1
1.1 Applications of Indoor Positioning Systems . . . . . . . . . . . . . . 4
1.2 Advantages of US over EM Wave . . . . . . . . . . . . . . . . . . . 5
1.3 Motivation and Contributions . . . . . . . . . . . . . . . . . . . . . 6
1.4 List of Publications . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2 Background and Related Work 12
2.1 Localization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.2 Location System Architectures . . . . . . . . . . . . . . . . . . . . . 14
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