Reef robocop

Co­ral-killing starfish are in the sights of a new ro­bot army that’s be­ing tri­alled on the Great Bar­rier Reef.

Australian Geographic - - Contents - STORY BY DAVID LEVELL

DOZENS OF UNDERSEA ro­bots could soon be comb­ing the north­ern Queens­land wa­ters, tak­ing on a ma­jor threat to the Great Bar­rier Reef – co­ral-eat­ing crown-of-thorns starfish (COTS) plagues.

Crown-of-thorns starf ish ( Acan­thaster planci) out­breaks are a lead­ing cause of co­ral loss on the Great Bar­rier Reef (GBR), and in 2015 Matthew Dun­babin and Feras Day­oub, roboti­cists from the Queens­land Univer­sity of Tech­nol­ogy, tested a promis­ing so­lu­tion – an au­ton­o­mous div­ing ma­chine called a COTSbot (see op­po­site). These can lo­cate and iden­tify the rogue starf ish un­der wa­ter and kill them with toxic, but en­vi­ron­men­tally friendly, in­jec­tions of bile salts.

Now tri­als are un­der­way of a vastly im­proved ver­sion of the COTSbot called RangerBot, funded largely by a $750,000 grant from Google’s Im­pact Chal­lenge pro­gram. And the early re­sults look so good that plans are un­der­way to sub­stan­tially scale up the project.

The lat­est ro­bot cruises at about 1.2m above the seabed, search­ing for the starf ish by pro­cess­ing up to 10 pho­tos a sec­ond. “We’ve got hun­dreds of thou­sands of images of starf ish, and we’ve trained RangerBot to recog­nise only crown-ofthorns,” Matthew says. “Our de­tec­tion sys­tem is about 99.4 per cent ac­cu­rate. We have ver y strict thresh­olds. If the ma­chine has any doubt, it won’t in­ject. Later we re­view the pho­tos it doubted to fur­ther im­prove our sys­tem.”

RangerBot swims lower than the pro­to­type COTSbot, tak­ing it closer to its starf ish tar­gets and im­prov­ing the ac­cu­racy of its ro­bot vi­sion or ‘im­age-based au­to­mated in­spec­tion tech­nol­ogy’.

Rate of pro­cess­ing was a key chal­lenge. “It re­quires se­ri­ous com­pu­ta­tion but we’re lim­ited by the power we can carry on board – even a lap­top’s too big,” Matthew says. “We’ve had to op­ti­mise soft­ware and hard­ware to run in real time.” Hav­ing iden­tif ied a crown-ofthorns starf ish, the ro­bot hov­ers about 90cm above it and in­jects the so­lu­tion, which kills the starf ish within 24 hours. It in­jects for about a sec­ond then quickly re­tracts so it doesn’t get caught on co­ral.

The orig­i­nal COTSbot was pow­ered by a small, soft drink bot­tle–sized air cylin­der that lasted for about 100 in­jec­tions. “With RangerBot, the hy­draulics use an elec­tric mo­tor, with sea wa­ter driv­ing the inf la­tion,” Matthew says, “so you don’t have to ref ill gas bot­tles.”

An even big­ger ad­vance was re­plac­ing COTSbot’s acous­tic nav­i­ga­tion sen­sors with a purely vis­ual sys­tem This makes RangerBot seven times cheaper to build, and much smaller. RangerBot’s bat­ter­ies are dif­fer­ent, too. Matthew says, “With COTSbot we had to recharge bat­ter­ies in situ, but the new RangerBot has re­mov­able bat­tery pods. On a boat, you can take the bat­tery out – with­out turn­ing it off – and put an­other one in, which meets our goal of an eight-hour op­er­a­tional day.”

An­other in­no­va­tion re­sponds to the crown-of-thorns’ life­style. “One of the big prob­lems is there are not enough crown-of-thorns starf ish vis­i­ble dur­ing the day,” Matthew says. “A lot of the time they’re hid­ing un­der­neath corals where we can’t get them.” RangerBot’s in­built light­ing means it can op­er­ate at night, when they come out to graze in the open.

Built to dive to 100m, RangerBot can travel about 14km in an eight-hour day (with a bat­tery change half­way). Its new sin­gle-shot in­jec­tion was a prior in­ven­tion, made in 2014 by James Cook Univer­sity re­searchers, to re­place the 20 or so in­jec­tions pre­vi­ously needed to kill a sin­gle starf ish.

That devel­op­ment a lone meant COTS-culling hu­man divers, who are still the main means of con­trol for the starf ish when they’re in plague pro­por­tions, be­came 250 per cent more ef­fi­cient.

RangerBot’s po­ten­tial to sup­port hu­man divers tar­get­ing crown-of-thorns is ob­vi­ous, but its ca­pa­bil­i­ties don’t stop at starf ish-zap­ping.

Matthew says co­ral-health mon­i­tor­ing, wa­ter sam­pling and f ish sur­veys are tasks RangerBot could also take on.

Roboti­cists (L–R) Feras Day­oub, Matthew Dun­babin and Peter Corke with their starfish-killing COTSbot that started the ro­bot rev­o­lu­tion now set to help con­trol the crown-of-thorns starfish (above) on the GBR.

Newspapers in English

Newspapers from Australia

© PressReader. All rights reserved.