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An Autonomous Underwater Vehicle (AUV) is a robot which travels
underwater. Sometimes called Unmanned Underwater Vehicles, these devices are
powered by batteries or fuel cells and can operate in water as deep as 6000
meters. Advances in propulsion systems and power source technology give these
robotic submarines extended endurance in both time and distance.
Picture taken from the HSV Swift by an employee of Bluefin Robotics Corporation
during a US Navy exerciseSome of the first AUVs were developed at the
Massachusetts Institute of Technology in the nineteen seventies. One of these is
on display in the Hart Nautical Gallery in MIT. At the same time, AUVs were also
developed in the Soviet Union (although this was not commonly known until much
later). In military applications, AUVs are also known as Unmanned Undersea
Vehicles (UUVs). They should not be confused with ROVs which are similar
unmanned undersea vehicles that are controlled and powered from the surface by
an operator/pilot via an umbilical.
The oil and gas industry uses AUVs to make detailed maps of the seafloor before
they start building subsea infrastructure. The detailed maps from the AUVs
allows the Oil Companies to install pipelines and sub sea completions in the
most cost effective manner with the minimum disruption to the environment. A
typical military mission for an AUV is to map an area to determine if there are
any mines. Scientists use AUVs to study the ocean and the ocean floor.
Although not currently operational, there are several designs of AUV that are
capable of subsea intervention (interaction with subsea structures) as opposed
to fly-by data collection. The development of subsea processing in deep and
ultra deep offshore oilfields and their cost of maintenance will be the most
likely Ťdrivers to make these vehicles routinely operational.
Primarily oceanographic tools, AUVs carry sensors to navigate autonomously and
map features of the ocean. Typical sensors include compasses, depth sensors,
sidescan and other sonars, magnetometers, thermistors and conductivity probes. A
demonstration at Monterey Bay in California in September 2006 showed that a 21
inch diameter AUV can tow a 300 feet long hydrophone array while maintaining a 3
knot cruising speed.
Bluefin-12 AUV with a Buried Object Scanning Sonar (BOSS) integrated in two
wings. This picture was taken in January 2005 off the coast of Florida during
engineering trials.Today, most AUVs work in conjunction with surface vessels for
navigational purposes, although ultra-low-power, long-range variants such as
underwater gliders are becoming capable of operating unattended for weeks or
months in littoral and open ocean areas, periodically relaying data by satellite
to shore, before returning to be picked up.
AUVs can navigate inside a net of acoustic beacons; this is known as Long Base
Line (LBL) navigation. When a surface reference such as a support ship is
available, Ultra-short baseline (USBL) positioning is used to calculate where
the subsea vehicle is relative to the known (GPS) position of the surface craft
by means of acoustic range and bearing measurements. When it is operating
completely autonomously, the AUV will surface and take its own GPS fix. Between
position fixes and for precise maneuvering, an inertial navigation system
onboard the AUV measures the acceleration of the vehicle and Doppler velocity
technology is used to measure rate of travel. A pressure sensor measures the
vertical position. These observations are filtered to determine a final
navigation solution.
Most AUVs in use today are powered by rechargeable batteries (lithium ion,
lithium polymer, nickel metal hydride etc). Some vehicles use primary batteries
which provide perhaps twice the endurance -- at a substantial extra cost per
mission. A few of the larger vehicles are powered by aluminum based semi-fuel
cells.
Hundreds of different AUVs have been designed over the past 20 or so years, but
only a few companies sell vehicles in any significant numbers. The small REMUS
100 AUV developed by Woods Hole Oceanographic Institution in the US and now
marketed by Hydroid, Inc. is the most popular AUV in the military and scientific
markets today. In the oil and gas industry, the larger Norwegian HUGIN 3000 AUV
developed by Kongsberg Gruppen and Norwegian Defence Research Establishment (FFI)
dominates. Other notable AUV manufacturers include Bluefin Robotics in the US
and International Submarine Engineering Ltd. in Canada.
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