Sweden: AUV/ROV capable of multiple tasks including intervention, touch down monitoring

Double Eagle Mk III, the newest member of Saab Bofors Underwater Systems' ROV/ AUV family, is due out for first delivery next year.

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Double Eagle Mk III, the newest member of Saab Bofors Underwater Systems' ROV/ AUV family, is due out for first delivery next year.

Over the last three years, said company ROV Systems Program Director Sven-Inge Svensson, various navies have part-financed improvements in the Double Eagle line. They have traditionally used the units for mine hunting, but the same components used by the navies are also available for commercial applications. And the navies' stringent reliability requirements can only benefit the oil patch, Svensson added.

Untethered mode

The Mk III is a step up from the Mk II in its improved battery and navigation systems. The unit, complete with increased payload interface, will be able to operate in both the tethered and untethered mode to 500-m water depth. As an AUV, it can operate continuously for 10 hours on batteries.

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The Double Eagle Mk III PVDS, set for delivery in 2003, traces its origins back to the Sea Twin of 1987, the McArov AUV from 1990, the 1996 debut of the Double Eagle Mk II, and the Double Eagle Mk II PVDS in 2000.
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"But the point of this vehicle is that it's going to be able to do both ROV and AUV operations," said Jan Siesjö, system manager for ROV systems.

The prototype is being built at Saab's plant in Motala, Sweden.

The 3-m long Mk III, which runs on automatic pilot whether in tethered or autonomous mode, features a surface control unit, a power converter unit, automatic tension control winch, tether, deck cradle, handling system, tether protection system, and portable operator control board. The bolstered power system adds some pounds to the Mk III, bringing its weight to approximately 1,300 lbs.

Underwater re-charging

Tethered, the unit will clip along at a speed of 4 knots in 300-m water depth. To allow the Mk III to operate as needed as an AUV, Saab developed a docking method with mateable connectors and sensors in the tether. The Mk III, which has a range of 4 km in tethered mode and 50 km-plus in AUV mode, is dockable and rechargeable underwater. Applications include survey work, long-range intervention, and touch-down monitoring.

"We have been into this type of system for quite a while," said Siesjö. "We feel that technology around sensors and batteries is to the point where it is reasonable to build AUVs on a commercial basis."

Saab sees the docking system central to the Mk III design as an intermediate step. The next version, Mk IV, will probably not be tethered, Svensson said.

For more information, contact Sven-Inge Svensson, Saab Bofors Underwater Systems. Tel: +46 141 22 47 50, fax: +46 141 22 44 59, email: sven-inge.svensson@dynamics.saab.se.

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