Powered "underwater glider" has no external moving parts

The ROUGHIE underwater glider takes a dive Purdue University

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When scientists wish to gather oceanographic data over long distances – but without disturbing marine life – autonomous "underwater gliders" are often used. A new one is claimed to be highly maneuverable, yet it has no external propulsion or steering systems.

Developed by a team at Indiana's Purdue University, the torpedo-shaped autonomous underwater vehicle (AUV) is known as the Research Oriented Underwater Glider for Hands on Investigative Engineering – or ROUGHIE, for short. It descends and climbs within the water column by pumping water in or out of an integrated ballast tank, varying its buoyancy. This serves as a form of propulsion, since the vehicle moves up and down at an angle, going forward as it does.

It can control the angle at which it rises and falls by electrically sliding its battery fore and aft within its body. Doing so changes the AUV's horizontal center of weight, and thereby its pitch. Additionally, the rail-mounted battery and other internal components can be tilted together to the port or starboard sides, relative to the cylindrical outer shell. This produces a weight-shift to one side or the other, causing the vehicle to roll and thus turn in that direction.

Purdue UniversityAssoc. Prof. Nina Mahmoudian (center) and her student team, with a couple of ROUGHIE prototypes

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Like other underwater gliders, ROUGHIE could potentially remain at sea for weeks or even months between battery-charges, near-silently gathering data using a number of added mission-specific sensors. Unlike those other vehicles, however, its high maneuverability should allow it to operate within relatively close confines, including shallower water. According to its designers, whereas other gliders have a turning radius of about 33 feet (10 m), ROUGHIE can make turns within just 10 ft (3 m).

What's more, it should cost about one tenth as much to manufacture. Testing has been limited to swimming pools so far.

"We program ROUGHIE with flight patterns ahead of time, and it performs those patterns autonomously," says Assoc. Prof. Nina Mahmoudian, who began developing the AUV in 2012 when she worked at Michigan Technological University. "It can do standard sawtooth up-and-down movements to travel in a straight line, but it can also travel in circular patterns or S-shaped patterns, which it would use when patrolling at sea. The fact that it can perform these tasks within the confined environment of a swimming pool using nothing but internal actuation is incredibly impressive."

A paper on the technology was recently published in the journal Sensors.

ROUGHIE can be seen in action, in the video below.

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