AUV supports environmental monitoring, wide area surveys

Paul Boughton
Carl-Marcus Remén reports on a new generation of autonomous underwater vehicles in the international oil and gas market.

Saab has been developing advanced autonomous underwater vehicles (AUVs) and remotely operated vehicles (ROVs) and for more than 30 years. Development of underwater vehicles from Saab has been done in a modular and evolutionary way to create a flexible solution to fit different domains and customers. An important strategy for the development of these modular vehicles has been to minimise life cycle and ILS costs for the customer. And now the company has just launched a new generation of AUVs to the international oil and gas market the AUV62.

Configurable design

The AUV62 has been in operation since 2002 mainly in the defence sector as a mine detection and surveillance vehicle but has now added functions that could benefit many operations connected to the oil and gas domain. The AUV62 uses an easily configurable design which will give operators a whole new way to handle AUV operations.

The AUV62 can be equipped with sensors for reconnaissance, environmental monitoring and surveillance. The system is designed for long range autonomous reconnaissance over vast areas, to be used in various scenarios thanks to the modularity of this AUV.

Equipped with suitable sensor module the AUV62 can be used to support operations such as:

- Mapping an area prior to deploying pipelines and other seabed installations.

- Detect, track and inspect various underwater installations.

- Environmental monitoring.

This vehicle has even helped in Search and Rescue (SAR) operations finding lost bodies and equipment.

The basic module, used for all AUV62 configurations, is equipped with an electrical propulsion system including systems for navigation, communication and vehicle control.

For geographical location tracking the vehicle utilises multiple information sources, such as inertial measurement systems, GPS, Doppler velocity log and terrain aided navigation.

To stabilise the vehicle in the water volume and handle depth-dependent temperature and salinity variations the AUV62 are equipped with ballast modules enabling automatic control of the weight and centre of gravity of the AUV body, particularly at low speeds.

During or after runs, the system can be used to surface the vehicle for communication or recovery. To power the vehicle Saab uses different kinds of battery technologies - Lithium polymer, Lithium Ion and standard Led acid batteries which are integrated into a energy module. The possibility to add more than one battery module increases the operational range of the AUV62.

AUV62 is assembled with interchangeable, mission specific, payload modules. The modules contain all mission specific equipment such as sensors used to detect, track and survey pipelines and other submerged installations.

Typical sensor systems to fit into an AUV62 payload module are:

- Side looking sonar system for detection of objects on the seabed and in the water volume

- Synthetic aperture sonar (SAS) - For even higher image resolutions and area coverage capability.

- Sub-bottom profiler for objects or infrastructure buried in the sediments.

- MBES (Multi-Beam Echo Sounder) for seabed map generation.

- Magnetic Field Sensors for ferromagnetic objects on the seabed, in the water volume and buried in the sediments.

A combination of more than one type of sensor can increase the AUV62's capabilities - for example, using a payload module equipped with a MBES, the seabed profile can be scanned and recorded by the AUV62, creating an advanced layout of the operation area. By supplying the payload module with a Sub-bottom profiler, the structure of the sediment layers below the seabed can be categorised and documented.

The addition of an MBES to the same module enables studying the change of the seabed structure over time, relative to the firm basement.

A payload for environmental monitoring is equipped with a number of different sensors for physical, chemical and biological monitoring of the underwater environment.

The AUV62 is equipped with a state of the art on-board computer which facilitates advanced sensor signal processing, resulting in high resolution images of the seabed and detected objects.

Sensor information is recorded for later evaluation and can, in parallel, be transmitted by radio, WLAN or satellite communication. To extend the operational range a gateway buoy can be placed to relay information to and from the vehicle. To be able to process data inside the vehicle is unique and proves the AUV62 advantages against other AUVs on the market. To be able to deliver processed data with high resolution in a more rapid way will be a cost saving issue.

The design of the AUV62 makes it highly mobile and easy to launch and recovered by the use of dedicated equipment. The AUV62 has been launched and recovered from various platforms even shores and harbours using a standard boat ramp.

To minimise the pre-set time before launching the AUV62 has a complete tools box for mission planning, preparation and command/control. This software runs in a PC environment and uses the standard 'click and drag' functions. The operator can either have this function in a stand alone Laptop set or integrated into a more advance operators environment. The advantages with AUV62 with its modular design are:

- Reduced mission time - use the same vehicle for a variety of missions.

- More rapid sensor data evaluation capabilities - onboard processing.

- Operational flexibility - Customer can design own payload module.

- Reduced risks and improved safety.

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 Carl-Marcus Remén is with Saab Underwater Systems AB, Motala, Sweden.

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