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Machines Like Us

Underwater robots explore treacherous deep-ocean terrain

Saturday, 01 December 2012
by Melissa Pandika

n autonomous underwater vehicle is deployed from the Rachel Carson research vessel. A system developed by Stanford researchers and others helps AUVs better explore the ocean floor. Photo: Sarah Houts / Stanford University

Engineers at Stanford's Department of Aeronautics and Astronautics and the Monterey Bay Aquarium Research Institute have developed autonomous underwater vehicles that can photograph regions of the ocean floor that were once too risky for these robotic explorers.

Underwater robots just got smarter. Engineers at Stanford and the Monterey Bay Aquarium Research Institute (MBARI) have developed a system that allows autonomous underwater vehicles (AUVs) to better anticipate obstacles in their path, enabling them to safely photograph even treacherous, distant reaches of the ocean floor.

Taking a series of photographs of the same areas over time helps scientists monitor the seabed for change. For instance, a conservation biologist might want to observe how species and habitats in marine protected areas are recovering from bottom trawling, a commercial fishing method that involves dragging a weighted net spanning hundreds of square feet along the ocean floor.

Noting changes in species and habitats can also help measure climate change.

Photographing the ocean floor with underwater vehicles isn't new, but the software system developed by Sarah Houts, a doctoral candidate in Stanford's Aerospace Robotics Laboratory, would for the first time allow vehicles to autonomously image twisting ravines and other hazardous topographical features.

Until now, scientists could image these tricky spaces only by remotely steering a vehicle themselves from aboard a ship, an expensive, impractical operation for missions involving periodic monitoring of the seabed. "It allows much greater flexibility," said Stephen Rock, the director of the Aerospace Robotics Laboratory.

Researchers from the aquarium research institute have recently developed AUVs that can image the ocean floor on their own, but only where it's relatively level. But Rock and other researchers believe that the most interesting science lies hidden in steeply dropping canyons and other interesting terrain.

"We need to be able to get into the interesting areas," Rock said.

Knowing what to do

To design a system that allows a torpedo-shaped vehicle to navigate remote, hazardous underwater sites, take photographs and return intact, Houts built on the terrain-relative navigation (TRN) system developed by Rock and MBARI engineer Rob McEwen. TRN allows a vehicle to know its location by matching its altitude (its distance above the ocean floor) to an existing terrain map. But to ensure that the vehicle would emerge unscathed, Houts had to give it the ability to anticipate and avoid obstacles.