Page 17: of Marine Technology Magazine (Mar/Apr 2021)

utonomous underwater vehicles have become versatile tools for exploring the seas. Purdue

University researchers are studying means to optimize the design, aiming to deliver a highly

A maneuverable, low-cost underwater glider that operates silently, with components and sensors that can be easily swapped out or added according to a wide range of mis- sion speci? cations.

“Our goal is persistent operation of mobile robots in chal- lenging environments,” said Nina Mahmoudian, associate professor of mechanical engineering. “Most underwater ro- bots have limited battery life and must return back after just a few hours. For long-endurance operations, an underwater glider can travel for weeks or months between charges but could bene? t from increased deployment opportunities in high-risk areas.”

An underwater glider differs from other marine robots be- cause it has no propeller or active propulsion system. It chang- es its own buoyancy to sink down and rise up, and to propel itself forward. Although this up-and-down approach enables very energy-ef? cient vehicles, it presents problems: the ve- hicles are slow and not maneuverable, especially in shallow water.

When deployed from shore or from a boat, ROUGHIE pumps water into its ballast tanks to change its buoyancy and provide initial glide path angle. To control its pitch, the vehicle’s bat- tery subtly shifts its weight forward and backward, acting as its own control mechanism. To steer, the entire suite of inner components are mounted on a rail that rotates, precisely con- trolling the vehicle’s roll. The design is modular and adaptable for a variety of applications.

“This is a totally unique approach,” Mahmoudian said. “Most underwater gliders can only operate in deep oceans and are not agile for con? ned spaces. ROUGHIE has a turning radius of only about 10 feet, compared to an approximately 33-foot turn radius of other gliders.”

EMPOWERING world leader in electric underwater robotics www.marinetechnologynews.com 17

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