18-04-2011, 02:16 PM
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1 INTRODUCTION
Due to extreme difficulty in gathering sub aquatic observations, very little is known about the oceans and their inhabitants. We do know, however that the oceans are an extremely complex and an equally important part of the world in which we live. They cover the majority of the planet's surface, influence our climate, host countless species of plants and animals, and are home to important geological processes. Since they are notoriously difficult to study, they present one of the final frontiers for exploration. Since the underwater environment is very dark and musky much of its biology and geology must be studied at very close range. At greater distances, even powerful lights fail to illuminate a scene sufficiently. The goal of Autonomous Underwater Vehicles (AUVs) is to improve underwater robot technology in order to enable more scientific exploration of the oceans.
1.1 AUV
With the increase in the interest in the environment and developments in technology, the concept of using autonomous underwater vehicles (AUVs) for oceanic data collection is emerging as a means of achieving a breakthrough in the exploration and exploitation of the Worlds oceans and climatic prediction.
An Autonomous Underwater Vehicle (AUV) is a robot which travels underwater. AUVs constitute a part of a larger group of undersea systems known as Unmanned Underwater Vehicles(UUV), a classification that includes non-autonomous Remotely Operated underwater Vehicles (ROVs) - controlled and powered from the surface by an operator or pilot via an umbilical.
Autonomous Underwater Vehicles (AUVs) are unmanned, untethered, self-propelled platforms which have the potential to revolutionize our access to the oceans and to address the critical problems faced by the marine community such as underwater search, rescue, mapping, climate change assessment, underwater inspection, marine habitat monitoring, shallow water mine counter measures and scientific studies in deep ocean areas.
Recent trends in AUV technology are moving towards reducing the vehicle size and improving it’s deploy ability to reduce the operational costs. There are undergoing large number of future operations that involve a fleet of small AUVs become financially and technologically feasible. Certainly the timing of AUV technology is good. It has been able to leverage its development by utilizing many technologies developed for other markets. AUVs are capable of gathering scientific observations without direct interaction of human operators and other applications.
1.2 WIRELESS COMMUNICATION IN AUV
While wireless communication technology today has become part of our daily life, the idea of wireless undersea communications may still seem far-fetched. However, research has been active for over a decade on designing the methods for wireless information transmission under water.
Human knowledge and understanding of the world’s oceans, which constitute the major part of our planet, rests on our ability to collect information from remote undersea locations. The major discoveries of the past decades, such as the remains of Titanic, or the hydro-thermal vents at bottom of deep oceans, were made using cabled submersibles.
Although such systems remain indispensable if high-speed communication page link is to exist between the remote end and the surface, it is natural to wonder what one could accomplish without the burden and cost of heavy cables. Together with sensor technology and vehicular technology, wireless communications will enable new applications ranging from environmental monitoring to gathering of oceanographic data, marine archaeology, and search and rescue missions.
Localization, navigation, and communication are three primary requirements for AUVs. In getting AUVs to solve problems comprehensively, a key issue is communication. Employing a powerful wireless communication network, AUVs have a multitude of applications in oceanography, environmental monitoring, and underwater resource studies, etc.
2 HISTORY AND DEVELOPMENT OF AUV
2.1 HISTORY OF AUVs
The concept of a submersible vehicle is not a new idea. The first American submarine was called “Turtle.” It was built at Saybrook, Connecticut in 1775 by David Bushnell and his brother, Ezra. The Turtle was a little egg-shaped wooden submarine held together by iron straps.
In November 1879, the Reverend George W. Garrett designed, what was considered to be the world's first practical powered submarine, the “Resurgam”. It was built at the Brittannia Engine Works and Foundry of J. B. Cochran in Birkenhead, England and was powered by a Lamm 'fireless' steam engine, and could travel for some ten hours on power stored in an insulated tank.
After these historic underwater vehicles, there have been many more submersibles developed and used operationally for a number of different tasks. With these submarines, came the development of torpedoes. Torpedoes are truly the first Autonomous Underwater Vehicles (AUVs).
Some of the first AUVs were developed by the Applied Physics Laboratory at the University of Washington as early as 1957. The "Special Purpose Underwater Research Vehicle" (SPURV), was used to study diffusion, acoustic transmission, and submarine wakes.
Although there are a number of AUV-like systems that were considered prior to the 1970s, most of them were never used for extended periods of time or discussed in open literature. Since that time a great deal of development has occurred.
Other early AUVs were developed at the Massachusetts Institute of Technology in the 1970s. One of these, “Odyssey IV” is on display in the Hart Nautical Gallery in MIT. At the same time, AUVs were also developed in the Soviet Union.
2.2 DEVELOPMENT STAGES OF AUV
The chronicle development of AUV began in the 1960s. A few AUVs vehicles are built mostly to focus on very specific applications or data gathering. During the 1970s, a number of test beds were developed. The University of Washington APL developed the UARS and SPURV vehicles. The University of New Hampshire’s Marine Systems Engineering Laboratory (now the Autonomous Undersea Systems Institute) developed the EAVE vehicle, an open space-frame AUV. This was a time of experimentation with technology in hopes of defining the potential of these autonomous systems. There were some successes and many failures.
The vision shared by the development community far exceeded the technology available to implement that vision. In the 1980s there were a number of technological advances that greatly affected AUV development. Small, low power computers and memory offered the potential of implementing complex guidance and control algorithms on autonomous platforms. Advances in software systems and engineering made it possible to develop complex software systems able to implement the vision of the system developers. The decade 1980-90 was indeed the turning point for AUV technology.
Fig. 1: A possible time-tables for the transition of AUV technology from prototype systems to operational vehicle systems is described by the characteristic “S” curve associated with the introduction of new techno logy into the market place.
During the decade 1990 – 2000, AUVs grew from proof of concept test beds into first generation operational systems able to be tasked to accomplish defined objectives. A number of organizations around the world undertook development efforts focused on various operational tasks. Potential users surfaced and helped to define mission systems necessary to accomplish the objectives of their data gathering programs. This decade also identified new paradigms for AUV utilization such as the Autonomous Oceanographic Sampling System (AOSN) and provided the resources necessary to move the technology closer to commercialization.
Actual growth of commercial markets for AUVs is credited to the decade2000 -2010. As this decade begins, the utilization of AUV technology for a number of commercial tasks is obvious. Programs are underway to build, operate and make money using AUVs. Markets have been defined and are being assessed as to viability. This is the decade that sees AUV technology moving from the academic and research environment into the commercial mainstream of the ocean industry. There are still technological problems to be solved. The economic viability of the technology has still to be proven. The AUV must be proven in an operational regime in order for the technology to continue its advance and for industry to embrace its potential.
2.3 CATEGORIZATION OF AUVS
There are different types of underwater vehicles. One method of categorizing these vehicles is to identify them as members one of two classes of vehicles; manned and unmanned systems.
Manned systems can be described simply as falling into two sub-classes; military submarines and non-military submersibles such as those operated to support underwater investigations and assessment. The Unmanned submersibles also fall in to a number of different sub-classes. The simplest and most easily described are those submersibles that are towed behind a ship. They act as platforms for various sensor suites attached to the vehicle frame.
A second type of submersible system is called a Remotely Operated Vehicle (ROV). An ROV is a tethered vehicle. The tether supplies power and communication to the ROV and is controlled directly by a remote operator.
A third type of unmanned submersible is an Unmanned Underwater Vehicle (UUV). This untethered vehicle contains its own onboard power, but is controlled by a remote operator via some type of a wireless communication link. An AUV is an undersea system containing its own power and controlling itself while accomplishing a pre-defined task.
A further distinction between the AUV and UUV is that AUV requires no communication during its mission whereas UUV requires some level of communication for it to complete its mission.
2.4 AUV TECHNOLOGY
Over the years, the focus of technology development has changed as new ideas surfaced to address technology problems. Some of the problems have been solved, others remain that must be addressed, and some other previously unrecognized problems have surfaced. It is hard to list all those technologies that are needed for AUV systems. But the following list represents many of the technologies that have been addressed over the past three decades.
Autonomy
Energy
Navigation
Sensors
Communications
The interesting aspect of this list is that although there have been advances in these technical areas, a number of these technologies still remain the “technology long poles” associated with AUV systems. Limits in these technologies limit the capability of AUV systems. Some of the technology “Long Poles” are as follows:
Autonomy / Cooperation / Intelligent Systems and Technologies
Energy Systems / Energy management
Navigation
Sensor Systems and Processing
3D Imaging
Communications
