Autonomous Underwater Vehicle Answers Arctic Challenges

October 12, 2011 - via JPT Online

12 October 2011—New frontiers in exploration are creating a need for new technology to meet the challenges of subsea data collection.

As part of the Woodside-operated Browse LNG Development, Fugro reported it will begin a deepwater autonomous underwater vehicle (AUV) survey. Woodside commissioned Fugro to undertake a detailed seabed mapping program, extending offshore from the project's proposed central processing facility, which will provide high quality data for the engineering process for the proposed subsea pipelines and other infrastructure, the company said.

Following the success of a similar project off northwest Australia last year, Fugro will use its Australia-based survey vessel, the 75 m Southern Supporter, and its regionally based Hugin 1000 AUV. The Kongsberg Maritime Hugin 1000 is a deepwater survey platform that enables multibeam echosounder, side-scan sonar, and sub-bottom profiling data gathering, the company said, powered by lithium polymer batteries with a survey endurance of up to 24 hours—ideally suited for this project.

Kongsberg's next-generation EM 2040 multibeam echosounder is available with the Hugin 1000; with improved resolution and a 6,000 m depth rating, it is a substantial improvement from the EM 2000, the company said; it also gives substantial advantages compared to the EM 3002 used in Hugin vehicles rated to 1,000 m.

The EM 2040 uses a single transducer system that gives a maximum 140° coverage sector; it has a large frequency range and can operate at 200, 300, or 400 kHz, the company said. At 400 kHz, the echosounder can operate on an internal trigger, resulting in ping rates of more than 20 Hz at low altitude. At low altitude with a 0.7° resolution and 25 μs pulse length, dynamic focusing, resolution, and sounding spacing is better than 10 cm by 10 cm, the company said. For example, the EM 2040 has so far been used on a Hugin 1000 operated by WTD71, a research institution under the German MoD, and with one of Kongsberg's own Hugin vehicles; and several sea trials were conducted last spring in Horten and Eckernförde in Germany, the company said.

Use of interferometric synthetic aperture sonar (HISAS 1030) in combination with the EM 2040, allows a high area coverage rate, which reduces survey time and thereby reducing overall operational risk and cost, according to paper OTC 22116-MS, titled “HUGIN Arctic Class AUV,” presented at the 2011 OTC Arctic Technology Conference. The vehicle’s enabling technologies for under-ice mapping include advanced collision avoidance algorithms developed specifically for under-ice operations, radio-through-ice communication and localization systems, and a doppler velocimeter log-aided internal navigation system designed for use on the North Pole without encountering polar magnetic numerical problems, the paper said. The system is configured in two ISO containers, 20 ft. and 10 ft., both insulated for Arctic climate, both shippable by land, air, and sea, and both insulated for Arctic climate, OTC 22116-MS said. It can be delivered with solutions for launch and recovery through a hole in the ice or a moonpool.

The increase in human activity in the Arctic requires a need for improved knowledge about the subsea Arctic, particularly with requirements for geophysical and bathymetric mapping of the seafloor in ice-covered areas, the paper said. Demand for this information is coming from various places, such as the US Minerals Management Service, national territory mapping, and academic research, OTC 22116-MS said. Traditioally, AUV surveys have provided substantial cost benefits for deepwater jobs while tow-body based survey systems have shown lower operational efficiency. But, AUVs are the only viable option in sub-ice projects, the paper said.

Arctic AUV applications include geophysical seabed mapping, offshore ice management, environmental monitoring, and marine research.

The Hugin 1000 has two sister models: the Hugin 3000, which is rated to 3,000 m, and the 4500 rated to 4,500 m. All the models are configurable to different payload configurations, and can propel themselves, handle unforeseen circumstances, navigate, and achieve mission objectives as set forth in a mission plan without human intervention.

The AUVs are equipped with acoustic communication links, facilitating various levels of human operator remote control, which is usually conducted from the same surface vessel that prepares, launches, and recovers the vehicle. The vehicles can either be operated in operator-supervised mode or full autonomous mode. The operator station includes a monitor and an operator panel with interfaces to payload operator stations, and vessel mounted sensors such as dGPS, HiPAP, ship attitude sensor, acoustic link, and radio frequency link systems.

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