Feature 3 | ROVS AND AUVS Both sides of the surface
Pairing up an unmanned surface vessel with an underwater vehicle could extend survey periods and save the time and expense of hiring a support craſt to keep track of AUV positions. Stevie Knight reports
“A
UVs are reliant on GPS when on the surface,” explains Ioseba Tena, global business manager
for Sonardyne. “As soon as they dive, they are effectively lost. It is just a question of how lost…they have to come up to get a positioning fix.” Tena continues: “Until now, the answer
has been to follow them with a vessel fitted with an ultra-short baseline [USBL] transducer that sends an acoustic wave to the AUV, telling it where it is.” However, he says, if you can get an AUV
to operate ‘over the horizon’, without the need for crew on a support ship, it opens up the possibility of extended, long-duration missions, including those that require a great degree of accurate positioning. So, Sonardyne has collaborated
with partners L3 ASV (previously ASV Global) and the National Oceanography Centre (NOC) in an Innovate UK-funded project to create an unmanned surface/underwater vessel duo that can team up by themselves and work in tandem. The Autonomous Surface and
Sub-surface Survey System (ASSSS), which was recently demonstrated at
The AUV/ASV pairing, demonstrated at Loch Ness, Scotland: this combination of vehicles could extend survey periods without the need for onsite intervention
Loch Ness in Scotland, uses proven technology for its main building blocks. Riding the waves, L3 ASV’s established C-Worker 5 ASV type was used to relay GPS back to shore. The below-surface
The BlueComm optical modem, installed on the NOC’s ALR: the modem is designed to transmit subsea data, stream
video and perform tetherless vehicle control (credit: Sonardyne)
element comprised the NOC’s Autosub Long Range (ALR) AUV type, kitted out with video and side scan sonar devices.
Optical modem The vessels were paired via acoustic transceivers for communications and positioning: integrating
the surface vessel Sonardyne’s combined
inertial navigation system (INS) and Doppler Velocity Log (DVL) SPRINT- Nav into its existing equipment. But there was a further trick
up Sonardyne’s sleeve. “The other innovation that allows this to operate has been an optical modem,” says Tena,
“because, as the ALR gathers more and more data from its video or sonar inputs, the acoustic system just doesn’t have the bandwidth to transmit it.” Sonarydne’s BlueComm, on the other hand, has been specifically developed to transmit subsea data, stream video and perform tetherless vehicle control.
40 Ship & Boat International November/December 2018
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