Autonomous Underwater Vehicle

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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 exercise

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 building 5 at MIT. In military applications, they are also known as Unmanned Undersea Vehicles (UUVs). They should not be confused with ROVs which are similar unmanned undersea vehicles that are controlled 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 drivers 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.