Robots under water

One of the toughest challenges for a robot is working at the bottom of the ocean. James Mitchell Crow looks at how scientists are solving those problems.

Stefan Williams with an autonomous underwater vehicle. His submersible robots have a pair of optical cameras whose output can be combined to create a 3D map of the ocean floor.. – University of Sydney

Is there a harder environment for a robot to work in than the bottom of the sea? “I think it’s a pretty tough thing to do,” says Stefan Williams, who leads the research into underwater robots at the Australian Centre for Field Robotics in Sydney. But he gets little sympathy from his colleagues. “The airborne guys say, if something goes wrong you just stop and float to the surface – we fall out of the sky!”

Light can’t penetrate far through water, nor can GPS satellite signals. But perhaps the biggest challenge is the high pressures. Earlier this year, US researchers from Woods Hole Oceanographic Institute lost contact with their deep sea unmanned vehicle Nereus while it was 9990 metres below the surface. Much of Nereus did float up again, but in tiny pieces. The operators suspect Nereus imploded.

Williams’ robots aren’t designed to go so deep. They are mapping the uncharted seafloor around Australia. Researchers don’t know what’s down there - the robots have to build up their own model of their environment on the fly. Williams’ robots have become part of a federally funded research program called the Integrated Marine Observing System.

His undersea robots have a pair of optical cameras whose output can be combined to create a 3D map of the ocean floor. He’s created advanced algorithms to process the reams of data generated on each dive. Much of this data is used by biologists studying undersea ecosystems – and how they are changing over time, especially as the ocean warms.

For instance the sea floor off north east Tasmania was once home to vast kelp forests, but large sea urchins are moving south as waters warm, and these hungry beasts have laid waste to swathes of kelp.

The challenge for biologists trying to understand the scale of the problem is that during the day the urchins hide away in cracks, only coming out to feed at night. It is very challenging for people to dive, but Williams’ robot doesn’t care what time of day it is.

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