What, where and when? – New opportunies for marine autonomous operaons
Seabed benchmark offshore Oregon, USA posioned by USV (Image courtesy of C. David Chadwell/WHOI ROV Jason)
a highly scalable network with potenal applicaons for a wide range of end‐users. In one such case, Innovate UK funding has supported ASV Ltd, the Naonal Oceanography Centre and Sonardyne Internaonal Ltd to develop this capability on long endurance USV and AUV for extended seabed survey and/or monitoring applicaons. One of the challenges in this situaon is how to efficiently transfer large volumes of data from the AUV to the USV without having to make a physical connecon. To address this need, another emergent technology, underwater opcal telemetry, is being employed. With the ability to transfer data at speeds equivalent to domesc
With the emergence of more autonomous (and intelligent) behaviours and long endurance vehicles, the range of applicaons for MAS has been growing steadily and with it, a range of different approaches to dealing with data telemetry, posioning and ming. While wideband digital acouscs remains at the heart of this, the ability to ghtly integrate acousc ranging and Doppler Velocity Logs (DVL) with Ineral Navigaon Systems (INS) is delivering increased precision and capability for MAS, while sparse Long BaseLine (LBL) techniques, ulising a small number of seabed transponders to constrain INS errors, can further increase navigaon precision. Indeed this capability is now mature enough to supersede stac laser scanning setups with sub‐cenmetric accuracy mapping projects from a mobile vehicle.
No less demanding, but employing different techniques, the capability of a USV to precisely posion and collect data from seabed transponders is being used for measuring tectonic crustal deformaon. These studies employ a surface plaorm fied with integrated GPS and Atude and Heading Reference Systems (AHRS) to acouscally range to the seabed transponders, and by doing this over an extended period of several days, non‐coherent errors, such as lateral sound speed gradients, to be minimised through averaging, resulng in sub‐cenmetric seabed posioning in several thousands of metres depth. The advent of long endurance USVs has dramacally reduced the costs of such studies, which previously used ships, while the latest generaon of low‐ power autonomous monitoring transponders can support uninterrupted seabed observaon studies in excess of a decade.
Between these two extremes of scale, new technologies are also laying the foundaons for deployment of underwater ‘system of systems.’ The latest generaon of subsea vehicle transponders are now not only capable of simultaneous posioning from, and telemetry with, a surface‐mounted Ultra‐Short BaseLine (USBL) system, but also telemetry with other vehicles and seabed assets. With the USBL mounted on a USV, this constutes the basis of
broadband over ranges in excess of 100 metres, this game‐changing technology is enabling new modes of operaon, and as well as supporng such ‘burst’transfers of data, it can also be used to support other applicaons requiring connuous high band‐width transmissions such as HD video.
NOC Autosub Long Range with Opcal and Acousc Communicaons (image courtesy of NOC)
Overall, the modern suite of posioning, communicaon and ming technologies now provides industry with a credible range of choices for operang MAS, which are not predicated on the need for constant high bandwidth transmissions between vehicle and operator. Instead, the growing potenal of independent and truly autonomous MAS operaons can be supported by data and posioning systems tailored to meet the end‐user’s informaonal needs, although implicit in this is clear definion and priorisaon of the volume and meliness of data streams required for both control and sensing funcons of these systems.
Geraint West
Global Business Manager – Oceanographic, Sonardyne Internaonal Ltd
Society of Marime Industries Handbook & Members’ Directory 2018 27
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