June 17, 2008 -- Marine creatures have communicated with each other for millions of years. Now swimming robots can too.
Three robofish, each 20 inches long and weighing just over six pounds, have been equipped with acoustic transmitters to communicate wirelessly with each other while underwater.
The robofish, created by University of Washington researcher Kristi Morgansen, could eventually monitor the migrations of large mammals and the diffusion of environmental pollutants.
"When the robofish are underwater we can't communicate with them." said Morgansen. "They have to be very independent."
Actual fish can communicate (albeit primitively) using an organ known as the lateral line, which runs down each side of the body and detects movement and vibration in the water via waves of physical pressure, or sound waves.
The robofish, which swim like regular fish by using a flapping tail instead of a rotating propeller, communicate by using acoustic modems, pinging sound waves to each other.
More familiar forms of above-water communications, like radio waves, don't work well under water. In freshwater, a radio signal can only travel about 10 feet. In saltwater, radio signals travel even shorter distances.
Trailing a long wire can create radio waves that travel farther, but they are only practical on large submarines.
Besides the acoustic modems, the robofish are also equipped with pressure sensors (to monitor depth) and a 3D compass, all powered by nickel-metal hydride rechargeable batteries.
The current trio of robofish are limited to a small test pool at the University of Washington in Seattle and can't be put into the ocean.
The next batch of robofish, expected to arrive next year, should venture into the waters of Puget Sound, where the researchers expect they will be able to track anything from large whales to microscopic environmental contaminants.
All the researchers will have to do is walk to the beach and drop the robofish in the water, said Morgensen. The onboard microprocessors and sensors will do the rest.
But, just because the robofish can think independently, doesn't mean they are fully autonomous.
Every 20 minutes or so (settings are adjustable) the next generation robofish would resurface to communicate with home base using a satellite link. At this point they would upload their data to the researchers and download any additional instructions. They could operate for up to six months at a time before returning home or being picked up by researchers in a boat, said Morgansen
James Tangorra, a researcher at Drexel University who studies bio-inspired designs, thinks that the robofish could help scientists track schools of fish.
"Fish-like propulsion might be more efficient, faster, and silent, allowing us to operate next to animals," said Tangorra.
Related Links:
Eric Bland's blog: Interior Design
University of Washington, Nonlinear Dynamics and Control Lab
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