There is something unnatural lurking in the waters of
the port of Gijon, Spain, and researchers are tracking its every move.
It is not some bizarre new form of marine life, but an autonomous
robotic fish designed to sense marine pollution, taking to the open
waves for the first time.
"With these fish we can find exactly
what is causing the pollution and put a stop to it right away," explains
Luke Speller, a scientist at the British technology firm BMT and the
leader of SHOAL, a European project involving universities, businesses
and the port of Gijon, which have joined forces to create the fish.
Currently the port relies on divers to
monitor water quality, which is a lengthy process costing €100,000 per
year. The divers take water samples from hundreds of points in the port,
then send them off for analysis, with the results taking weeks to
return. By contrast, the SHOAL robots would continuously monitor the
water, letting the port respond immediately to the causes of pollution, such as a leaking boat or industrial spillage, and work to mitigate its effects.
The SHOAL fish are one and a half
metres long, comparable to the size and shape of a tuna, but their
neon-yellow plastic shell means they are unlikely to be mistaken for the
real thing. A range of onboard chemical sensors detect lead, copper and
other pollutants, along with measuring water salinity. They are driven
by a dual-hinged tail capable of making tight turns that would be
impossible with a propeller-driven robot.
They are also less noisy, reducing the
impact on marine life. The robots are battery powered and capable of
running for 8 hours between charges. At the moment the researchers have
to recover them by boat, but their plan is that the fish will return to a
charging station by themselves.
Working in a group, the fish can cover
a 1 kilometre-square region of water, down to a depth of 30 metres.
They communicate with each other and a nearby base-station using very
low-frequency sound waves, which can penetrate the water more easily
than radio waves. However, this means the fish have a low data
transmission rate and can only send short, predefined messages. "It's a
good solution, but it requires thinking carefully about what data to
transmit and how to use that data," says Kristi Morgansen, a roboticist at the University of Washington, who was not involved in the research.
Navigation relies on a related system
that communicates with four "pingers" at the corners of the port, which
act much like GPS satellites for the fish. If one fish senses pollution
in an area it can call the others to create a detailed map of high and
low concentrations around it, helping port authorities to locate the
exact source of the pollutant.
Versions of the fish have been working
successfully in the lab for a few years now, but trialling them in a
real-life port has proved more difficult. Rough weather has often
prevented the researchers from venturing out on the waves, though
Speller says the fish would be fine as they can simply dive below the
water. But depth has also been a problem – the waterproofing on one
component is unable to withstand the pressure at 30m underwater, so it
requires a last-minute replacement.
Thankfully the fish are fitted with a
variety of safety features if something goes wrong, such as airbags that
inflate to make the fish surface, and a GPS and cellphone chip in the
fin so that a distressed fish can send its location details to Speller's
phone via text message.
Having demonstrated that the fish can
sense pollution and communicate underwater, the SHOAL group now plans to
commercialise the design and sell it to other ports in Europe and the
rest of the world. The prototypes currently cost around £20,000 each,
but mass production should bring that price down.
Speller plans to do more than just
track pollution, however – the fish's modular design makes it easy to
swap the chemical sensors for other applications. "I like to see the
fish as platform for other things that can be done in the sea, such as
search and rescue, helping divers, and port security."
Morgansen says that underwater gliders
have proved successful in monitoring open waters, but they cannot move
within the tight spaces of a port or harbour. This means nimbler
fish-inspired robots like SHOAL's may be the way forward. "I think the
use of agile underwater robots for monitoring water systems will happen
in most ports in the not-distant future."
No comments:
Post a Comment