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Shallow-Water Surveys with a Fleet Of Heterogeneous Autonomous Vehicles
REP-AUV10 Experiment Demonstrates Potential Ways To Enhance AUV Capabilites, Develop Interoperable Systems

By Ricardo Martins
Scientific Researcher
Underwater Systems and Technology Laboratory

João Borges de Sousa
Laboratory Head
Underwater Systems and Technology Laboratory
Porto University
Porto, Portugal

Carlos Carvalho Afonso
Lieutenant Commander
Portuguese Navy
Base Naval do Alfeite, Portugal

The Recognized Environmental Picture 2010 experiment was devised by the NATO Undersea Research Centre (NURC) and was to take place in the Alboran Sea with participants from 10 nations representing 27 organizations. The goals of this sea trial included centralized operation of a large and heterogeneous fleet of gliders and AUVs, and the utilization of autonomous vehicles and respective command and control software for battle-space characterization, with a focus on mine warfare-related research.

Due to unforeseen logistics problems, the event had to be replanned, and the AUV experiments ceased to be a priority. The parties involved in the AUV-related experiments then chose to organize a new event to take place in the coastal waters of Setúbal, Portugal, in July 2010 that focused mainly on AUV operations.

This event, REP-AUV10, was made possible due to a memorandum of understanding established in 2007 between Porto University and the Portuguese Navy. This agreement built on the successful deployment of AUVs from Porto University during the Swordfish 2006 exercise of the Portuguese Navy and targets the development of unmanned vehicle systems, with special emphasis on AUVs. This was the case of the SeaCon project, which was funded by the Portuguese Ministry of Defense under this memorandum of understanding.

The main objective of this project consisted of the development of an open and low-cost AUV system for training and improvement of concepts of operation for shallow waters. The system will also be used by the Portuguese Navy to test and evaluate underwater technologies in a cost-effective manner and to develop specialized underwater warfare know-how, namely in mined environment warfare.

REP-AUV10 Objectives
The REP-AUV10 experiment was organized and planned by the Portuguese Navy in cooperation with Porto University, the Naval Undersea Warfare Center Newport (NUWC), the Naval Research Laboratory and NURC. Also participating in the event were SeeByte (Edinburgh, Scotland), OceanScan-MST (Porto, Portugal), OceanServer Technology Inc. (Fall River, Massachusetts) and YSI Inc. (Yellow Springs, Ohio).

The main objectives of the event were to assess the endurance, durability and navigational performance of low-cost man-portable AUVs; experiment with novel safety and emergency strategies; extend the communication range of autonomous vehicles by using fixed and mobile gateways; explore the intricacies of deploying a hybrid fleet of AUVs; validate and interpret remotely sensed data; assess the relative fidelity of this data compared with data acquired on scene and on ships; and shore launching and recovery of AUVs.

To support the event, the Portuguese Navy deployed the NRP Bacamarte, a Bombarda-class landing craft utility ship built by the Portuguese Navy that has been in service since August 1985. The ship is used in operational training of naval units, for recovering torpedoes and towing artillery targets. Recently, it has also been used to combat pollution and was deployed in the Prestige and Nautila missions. Since 2009, the ship has been routinely employed to support the AUV operations of the Mine Warfare Detachment of the Portuguese Navy.

NURC participated in the event by producing remote-sensing bathymetry. The Naval Research Laboratory provided 72-hour forecasts for environmental modeling of sonar performance, general environmental characterization and thresholding for AUV operations. This information was uploaded daily to a dedicated FTP site created for the event.

During the event, YSI Inc. collected daily CTD profiles with its CastAway CTD for comparison with the data collected by the AUVs. Two industrial containers were installed on the NRP Bacamarte to support AUV operations and house command and control centers. A dive team supported operations.

Participating AUVs
A total of 10 autonomous vehicles from different institutions and manufacturers were deployed during the event. These are each briefly described here:

The Gavia Defense AUV. Developed by Teledyne Gavia ehf (Kópavogur, Iceland), the Gavia Defense AUV is a highly modular vehicle targeted at defense and law enforcement applications. Modules can be installed or replaced in the field in a matter of minutes. The Portuguese Navy purchased two vehicles of this class in 2009 for mine countermeasures and search-and-rescue missions. The mission life cycle of these vehicles is managed by the Gavia Control Centre software program or alternatively by SeeByte's SeeTrack.

Iver2 AUV. The Iver2 series, developed by OceanServer, is designed for shallow-water surveys. During the event, NUWC operated three Iver2 vehicles and OceanServer operated one. The mission life cycle of these vehicles was managed by the Vector'Map software program.

SeaCon AUV. Based on evolutions of the Light Autonomous Vehicle developed by Porto University, the SeaCon AUV is targeted at innovative standalone or networked operations for applications in mine warfare, oceanography, mapping and rapid environmental assessment. State-of-the-art command, control and communications technologies enable new concepts of operation supporting mixed-initiative interactions with human operators. The mission life cycle is managed by the Neptus software framework. Innovations of the SeaCon system include networked operations, interoperability, mixed-initiative operations and open system architecture. Two SeaCon AUVs were operated by Porto University.

Swordfish ASV. Used both as a mobile gateway for underwater communications and surveying, the Sword'fish is an autonomous surface vehicle (ASV) based on an ocean-going catamaran equipped with two thrusters. This vehicle was developed by Porto University and is used both as a mobile gateway for underwater communications and as an autonomous survey vehicle. During a survey, Swordfish streams sonar data and video in real-time to the base station. The mission life cycle of this vehicle is managed by the Neptus software framework.

The rectangle marks the zone in which REP-AUV10's area of operations was established. The area, one nautical mile west of Praia da Lixeira in Set'bal, Portugal, has a minimum depth of 10 meters and a maximum depth of 60 meters.

Isurus AUV. Developed by Porto University, Isurus is a modified version of a REMUS-class AUV, built by the Woods Hole Oceanographic Institution (Woods Hole, Massachusetts), for low-cost and lightweight operations in coastal waters. Under the hood, Isurus uses the same computational architecture as the SeaCon AUV. The mission life cycle of this vehicle is managed by the Neptus software framework.

The Manta Gateway
Also developed by Porto University, the Manta Gateway is a centralized communications hub for maritime assets that supports several types of wireless networks. The system is capable of transparently routing data between heterogeneous network links, balancing bandwidth and range. An HSDPA/GSM modem provides a direct connection to the Internet in territorial waters, allowing real-time data publishing to the web. Two Wi-Fi devices (2.4 and 5 gigahertz) provide a low-cost solution for high-throughput and medium-range (4.5 kilometers) communications. One acoustic modem is installed for low-bandwidth and long-range underwater communications. Routing and store-and-forward capabilities are implemented with the aid of the delay tolerant networking reference implementation. The system is fully portable and can be used standalone, as well as on buoys, rigid-hulled inflatable boats and ships.

During REP-AUV10, the Manta Gateway was installed on the NRP Bacamarte, Swordfish and two small buoys. The gateways were deployed in a straight line at 1.5-kilometer intervals, beginning with one on the NRP Bacamarte, to create a high-bandwidth and dynamic network, where nodes come and go. All gateways used omnidirectional antennas and have a nominal range radius of four kilometers. However, the SeaCon AUVs can only communicate with the gateways at close range (i.e., less than one kilometer, preferably 750 meters). Without this constraint, the network spanned an area of 12 by four kilometers; with this constraint, it spanned an area of 4.5 by 1.5 kilometers.

REP-AUV10 took place near Praia da Lixeira in Setúbal, Portugal. The area of operations was rectangular, with dimensions of four by 2.5 nautical miles (including an additional 0.25 miles on each side for a safeguard area), and was situated approximately one nautical mile west from the beach. This area has a minimum depth of 10 meters, a maximum depth of 60 meters and the sea state varies between calm and moderate. Several fish nets exist in the area, some of which are unmarked.

The operational area was subdivided into seven 0.5-by-2.5-square-nautical-mile rectangles that were named A through G. The NRP Bacamarte was anchored in the middle of area D, and each day a set of subareas was assigned to each team. Area D was also reserved for experimental operations.

The beaches near the area of operation were difficult to reach by land and in order to perform beach launchings, the NRP Bacamarte had to land on the beach. This maneuver was executed twice and allowed for the NUWC team to deploy its AUVs from the beach, with subsequent recovery from the ship at a later time.

The partition of the operating area into zones for each institution proved correct under normal behaviors, and the reaction to emergencies proved timely and efficient. However, integrating planning procedures may lead to a better utilization of the available manned and unmanned assets in emergency procedures, such as looking for assets that were temporarily lost. GSM technology proved very useful and inexpensive to localize vehicles in coastal waters. To continue this article please click here.

Ricardo Martins became a researcher at Porto University's Underwater Systems and Technology Laboratory in 2005, where he develops the software used in all of its autonomous vehicles. In cooperation with the NATO Undersea Research Centre, he also develops software to improve underwater acoustic communications. He has consulted with the Portuguese Navy on autonomous vehicles since 2008.

João Borges de Sousa is a lecturer at the Electrical and Com'puter Engineering Department at Porto University and the head of the Underwater Systems and Technologies Laboratory. His research interests include unmanned vehicles, control architectures, control and coordination. He has authored more than 200 publications, including 20 journal papers.

Lt. Cmdr. Carlos Afonso graduated from the Portuguese Naval Academy in 1994. He served as an anti-submarine warfare officer aboard frigates and was an instructor at the academy for five years. He is in charge of the Minewarfare Office of the Portuguese Training and Evaluation Center and is responsible for the Portuguese Mine Countermeasures AUV Program. He is also the Portuguese Navy's project manager for SeaCon.

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