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Abstract

There is an inherent risk of loss that accompanies any operations of Autonomous
Underwater Vehicle (AUV) technology. This complexity and risk are increased for
AUV missions that are conducted beneath ice and in harsh environmental conditions
(i.e. extreme cold, compromised visibility, etc.). Risk-based methodologies
have been developed to quantify the risk of loss for specific AUV platforms prior to
deployments. Their goal is to identify and mitigate where possible the significant
contributors (technical or otherwise) to the overall risk of a specific operation. Not
surprisingly, there is an abundant amount of literature related to successful AUV
missions; however, there has been very little published work related to AUV loss.
Specifically, this author is not aware of any examples of a developed procedure to
employ during an AUV loss event to date, much less specific algorithms developed
to locate a missing AUV. This is a subset of the AUV tracking or positioning that
is rarely given specific treatment.
The motivating problem is based on the loss event of an AUV during polar
operations. For example, (i) the vehicle might navigate outside of its predefined
spatial area through some fault or error, or, (ii) its mission involves over-thehorizon
operations, i.e. beyond the range of standard acoustical tracking technologies.
In either circumstance, at the end of its pre-programmed mission, the
AUV fails to return to the base station. Such an eventuality defines the need for
reliable, long-range acoustic tracking capability that is able to coarsely localize the
AUV and subsequently enable communications and/or recovery of the AUV.
The thesis describes a novel approach for an acoustic positioning system for
AUV localization in harsh environments with non-standard acoustic challenges
that can be implemented using only basic acoustic technology, a basic singlebeacon,
single-hydrophone (SBSH) system. Inversive geometric techniques are
applied for source localization of a one-way traveling, asynchronous acoustic signal.
This differs from the usual methods of spherical, two-way direct flight measurement
based on time of arrival (TOA), or hyperbolic, one-way time difference of arrival
(TDOA) target tracking for transmission based on a purely Euclidean geometry.
This is a novel approach to the problem of localizing an AUV.
A second method of solving the non-linear system of equations that arise
from the problem using the SBSH approach is derived. Both methods, the novel
Apollonian inversion geometry localization (AIGL) and the non linear system localization
(NLSL), are evaluated in simulation and using live field data. It will be
shown that the novel algorithm performs comparable to the standard method of
solving the nonlinear systems resulting from a SBSH approach. Furthermore, in
certain situations it improves the localization result.

Item Type:	Thesis - PhD
Authors/Creators:	Lewis, RS
Keywords:	Novel under ice AUV acoustic localization algorithm
Copyright Information:	Copyright 2015 the Author
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