STANFORD (US) — New underwater vehicles can photograph regions of the ocean floor that were once considered too risky.
The vehicles’ software system—developed by Sarah Houts, a doctoral candidate in Stanford University’s Aerospace Robotics Laboratory—could 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,” says Stephen Rock, the lab’s director.
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 says.
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 Monterey Bay Aquarium Research Institute 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.
Using the terrain map, Houts calculated the optimal trajectories, as well as the vehicle’s optimal altitude, speed, and orientation at each point along the flight path, allowing the AUV to safely fly close to the ocean floor. The autonomous craft applies algorithms to steer itself around obstructions in its path.
“We’re saying, ‘Now that I know where I am, this is what you want to be doing here. This is how high you want to be, this is the angle you want,” Rock says.
The engineers recently ran a successful field test with the new AUV system in Monterey Bay, during which they programmed the vehicle to fly over a cliff at a constant altitude to ensure that it understands the commands they give it.
In another test planned for early next month, they’ll compare that flight path to the one the AUV takes when programmed with Houts’ algorithms.
Rock expects his group to begin running missions with the new system by next year.
Source: Stanford University