Seminar

Topic: AUVs

AUVsAutonomous

Underwater Vehicle

What Are AUVs?

An autonomous underwater vehicle (AUV) is a robot which travels underwater without requiring input from an operator. AUVs constitute part of a larger group of undersea systems known as unmanned underwater vehicles, a classification that includes non-autonomous remotely operated underwater

vehicles (ROVs) – controlled and powered from the surface by an operator/pilot via an umbilical or using remote control. In military

applications AUVs are more often referred to simply as unmanned undersea vehicles (UUVs)

And..

Autonomous Underwater Vehicles (AUV), also known as unmanned underwater vehicles, can be used to perform underwater survey missions

such as detecting and mapping submerged wrecks, rocks, and obstructions that pose a hazard to navigation for commercial and recreational vessels. The AUV conducts its survey mission without

operator intervention. When a mission is complete, the AUV will return to a pre-programmed location and the data collected can be downloaded and processed in the same way as data collected by shipboard systems

*What’s the difference between an AUV and a Remotely Operated Vehicle (ROV)?

AUVs operate independently of the ship and have no connecting cables.

How it Works? Visual Representation

Underwater Vehicles

Under water vehicles are broadly classified of 3 types; the names are used interchangeably sometimes.

1

• Remote operated vehicle(RUVs)

2

• Unmanned underwater vehicle(UUVs)

3

• Autonomous Underwater Vehicle(AUVs)

Early AUVs

• The first AUV was developed at the Applied Physics Laboratory at the University of Washington as early as 1957 by Stan Murphy, Bob Francois and later on, Terry Ewart. The "Special Purpose Underwater Research Vehicle", or SPURV, was used to study diffusion, acoustic transmission, and submarine wakes.

• Other early AUVs were developed at the Massachusetts Institute of Technology in the 1970s. 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

Basic 2 - Dimensional Structure

• The vehicle is 21" (53 cm) in diameter, and about 8 ft. (2.5 m) long.

• It weighs about 450 lbs. (200 kg).• It is capable of operating at water depths up to

4500 m with a nominal velocity of 3 kts (1.5 m/s). In a survey mode it has a maximum range of about 50 km i.e. (31.0686).

3 – Dimensional Structure

Parts of AUV!

Various Parameters of the AUVs

Sensor Systems & ProcessingNavigationsPropulsionPower & EnergyCommunications Autonomy

Sensor Systems & Processing• An AUV is simply a platform on which to mount sensors and

sensing systems. Initial efforts to develop AUV technology was more concerned about the basic technologies required to allow reliable vehicle operation. As that reliability was achieved, sensors were added to the vehicle system to acquire data from the ocean environment

• Typical sensors include: compasses depth sensors side-scan SONAR magnetometers thermistors

Navigation• AUVs can navigate using an underwater acoustic positioning system. When

operating within a net of sea floor deployed baseline transponders this is known as LBL navigation.

• When a surface reference such as a support ship is available, ultra-short baseline (USBL) or short-baseline (SBL) 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.

• Inertial navigation is a dead reckoning type of navigation system that computes its position based on motion sensors. Once the initial latitude and longitude is established, the system receives impulses from motion detectors that measure the acceleration along three or more axes enabling it to continually and accurately calculate the current latitude and longitude.

• Its advantages over other navigation systems are that, once the starting position is set, it does not require outside information, it is not affected by adverse weather conditions and it cannot be detected or jammed.

Propulsion• AUVs can rely on a number of propulsion techniques, but propeller based

thrusters or Kort nozzles are the most common by far. These thrusters are usually powered by electric motors and sometimes rely on a lip seal in order to protect the motor internals from corrosion.

Power & Energy• Most AUVs in use today are powered by rechargeable batteries (lithium

ion, lithium polymer, nickel metal hydride etc.), and are implemented with some form of Battery Management System.

• 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 aluminium based semi-fuel cells, but these require substantial maintenance, require expensive refills and produce waste product that must be handled safely.

• An emerging trend is to combine different battery and power systems with Ultra-capacitors.

• Endurance of AUVs has increased from a few hours to 10s of hours. Some systems now contemplate missions of days and, a very few, of years. This extended endurance, however, is at the expense of sensing capability, as well as very limited transit speeds.

Communications

• In the underwater environment acoustic communications is probably the most viable communication system available to the system designer.

• Some development programs have investigated and evaluated other technologies such as laser communication at short range and relatively noise free communications over larger ranges using RF current field density techniques.

• In the past 10 years there has been significant advances in acoustic communications such that relatively low error rate communications is possible over ranges of kMs at bit rate of a few kbps [Comms]. This remains an active area of investigation.

Autonomy

• In the 1980s there was effort placed into understanding how to give an AUV a level of intelligence necessary to accomplish assigned tasks. Issues such as intelligent systems architectures design, mission planning, perception and situation assessment were investigated.

• These are all hard problems and there were few successes that led to in-water evaluation. As the capabilities required by the first generation AUVs became clear, the tasks the AUVs were to perform seemed not to demand a high level of intelligent behaviour. In fact many of the tasks being assigned to today’s AUVs required only a list of pre-programmed instructions to accomplish a task. For this reason, there has not been a significant level of development, recently, that is focused on AUV autonomy.

• The problem of autonomy still remains unsolved. There have been some successes with other autonomous systems, but those advances have not been brought into the AUV community. There are very few programs funded to address these issues and the problem remains.

• As AUV operations increase, it will become apparent that more investigation is needed. This will again emphasize the need for more development along the lines of making AUV systems more intelligent and better able to adapt to the environment within which they exist.

Applications Of AUVsCommercial Applications

The oil and gas industry uses AUVs to make detailed maps of the seafloor before they start building subsea infrastructure; pipelines and sub sea completions can be installed in the most cost effective manner with minimum disruption to the environment.

The AUV allows survey companies to conduct precise surveys of areas where traditional bathymetric surveys would be less effective or too costly.

Military Applications A typical military mission for an AUV is to map an area to determine if

there are any mines, or to monitor a protected area for new unidentified objects.

AUVs are also employed in anti-submarine warfare, to aid in the detection of manned submarines.

Research Applications

Scientists use AUVs to study lakes, the ocean, and the ocean floor. A variety of sensors can be affixed to AUVs to measure the concentration of various elements or compounds, the absorption or reflection of light, and the presence of microscopic life.

Additionally, AUVs can be configured as tow-vehicles to deliver customized sensor packages to specific locations.

Investigation Applications

Autonomous underwater vehicles, for example AUV ABYSS, have been used to find wreckages of missing airplanes, e.g. Air France Flight 447

AUV – 150 from INDIA

• AUV (Autonomous Underwater Vehicle) - 150 is an unmanned underwater vehicle (UUV) being developed by Central Mechanical Engineering Research Institute (CMERI) scientists in Durgapur in the Indian state of West Bengal. The project is sponsored by the Ministry of Earth Sciences and has technical assistance from IIT-Kharagpur.

• The vehicle was built with the intent of coastal security like mine counter-measures, coastal monitoring and reconnaissance.

• AUV 150 can be used to study aquatic life, for mapping of sea-floor and minerals along with monitoring of environmental parameters, such as current, temperature, depth and salinity.

• It can also be useful in cable and pipeline surveys. It is built to operate 150 metres under the sea and have cruising speed of up to four knots.

AUV- 150

Characteristics of AUV - 150Structure

• AUV-150 is cylindrical-shaped with streamlined faring to reduce hydrodynamic drag. It is embedded with advanced power, propulsion, navigation, and control systems.

• The UUV includes a pressurized cabin which is necessary for the diving and flotation system to work properly; this also helps to increase its sealing power against water leakage into the cabin.

• The AUV 150 weighs 490 kg, is 4.8 metres long and has a diameter of 50 cm.Control system

• The AUV is autonomous, that is automatic and self-controlled. It has an on-board computer that can be pre-programmed to dive to pre-set depths, move along pre-set trajectories, and return to the base after completing the assigned tasks. A remote control option is provided in order to perform special tasks.

Propulsion• It is propelled by water-jet propulsion which comprises thrusters for generating

motion in different directions to control surge, sway, heave, pitch, and yaw, while preventing the vehicle from rolling. Two arrays of cross-fins have also been fixed at the two ends to provide additional stability to the AUV.

Navigation• The autonomous vehicle is equipped with a number of navigational equipment to

locates its own geographical position Such as inertial navigation system, depth sonar, altimeter, Doppler velocity log, global positioning system through ultra-short baseline system and forward looking sonar to facilitate obstacle evasion and safe passage.

Payload• It is equipped with an underwater video camera that can send wireless video

pictures from underwater to a monitor above water surface along with side scan sonar.

• The submarine is equipped with CTD or conductivity-temperature-depth recorder and several sensors that can measure orientation, current and speed.

Communication• For smooth communication and distant intervention, the vehicle is equipped with

hybrid communication system: it uses radio frequency while on surface and acoustic under water.

Power• The vehicle uses a Lithium polymer battery and can operate up to depths of 150

metres at speeds of 2-4 knots.

AUV Manufacturers!

• Kongsberg Maritime

• Hydroid (now a wholly owned subsidiary of Kongsberg Maritime)

• Bluefin Robotics

• Teledyne Gavia (previously known as Hafmynd)

• International Submarine Engineering (ISE) Ltd.

Research & Development

• Current AUV development programs are, in many cases, being supported by funding that results from the political process as opposed to market need or technical merit. This, however, is a current reality within which development of AUV technology advances.

• Although these programs are very visible due to the level of activity, it is short sited to over emphasize some of these activities over smaller, less advertised work.

• There are a number of organizations in the USA, and elsewhere, actively working on important research problems.

• As mentioned above, there is much to be understood regarding technologies such as Autonomy, Energy, Navigation, Sensors, and Communications. These are very much open research topics

Evolving Markets

• At this point in time we are seeing a number of markets beginning to form. Although not clearly defined the level of enthusiasm of a number of individuals and organizations suggests that we will see many opportunities for commercializing AUV technology over the next few years.

• Individual companies, as well as teams of organizations, have begun efforts to make operational AUVs part of the oil & gas industry toolkit. Missions have been defined, contracts let, vehicle systems designed, and fabrication of the operational systems begun.

• The next fewyears will provide insight into the real capability of the commercial AUV

The Future of AUV Technology• AUV technology has followed a path not unlike other

technologies. It has gone through stages where academic curiosity was followed by research investigation and prototype development.

• Applications have recently surfaced that seem to have sufficient financial backing to develop operational systems. Certainly the timing of AUV technology was good. It has been able to leverage its development by utilizing many technologies developed for other markets.

• The next five years will see the expansion of AUV technology into the commercial marketplace. The size of that market is unclear but the move into the marketplace has begun. There are still many important research investigations to be undertaken. Autonomy is probably the most important issue to be addressed but others, such as those described above, certainly must be addressed.

• It is clear that the limit to the capability of any AUV is the amount of energy it has on board. There have been many discussions that suggest that fuel cell technology has reached a point where it may well be possible to use this technology in AUV systems.

• The increase in endurance will be substantial. Is this the “silver bullet” for AUVs? I would suggest that there is no “silver bullet,” but rather a continuum of activity that spans a wide spectrum. Basic research into some of the enabling technologies must be supported.

• The development of operationally reliable systems must be undertaken. Unique markets where AUV technology can make a significant impact must be identified. Most important, the AUV community must educate the user community of the future about AUV systems capabilities and operational reliability