Robotic fish glides almost indefinitely

Posted by Ken Kola

Michigan State University scientists say their latest robot fish can glide almost forever, using little to no energy, while gathering data on water quality.

"Swimming requires constant flapping of the tail, which means the battery is constantly being discharged and typically wouldn't last more than a few hours," says " says Xiaobo Tan, MSU associate professor of electrical and computer engineering.

The disadvantage to gliding, he said, is that it is slower and less maneuverable than normal swimming, leading the team to incorporate both types of motion.

"Such integration also allows the robot to adapt to different environments, from shallow streams to deep lakes, from calm ponds to rivers, with rapid currents," says Tan.

The robot's ability to glide is achieved through a newly installed pump that pushes water in and out of the fish, depending on whether the robot is ascending or descending. In addition, the robot's battery pack sits on a kind of rail that moves backward and forward in sync with the pumping action, allowing the robot to glide on the desired path.

The robotic fish, dubbed Grace, has already been for a test drive on the Kalamazoo River.

"She swam at three sites along the river and wirelessly sent back sensor readings," says Tan. "I'm not sure, but we may have set a world record - demonstrating robotic fish-based sampling with commercial water-quality sensors in a real-world environment."

Grace isn't the first underwater glider: indeed, one traveled all the way across the Atlantic Ocean in late 2009. Grace, though, has the ability to swim as well and is also about 10 times smaller and lighter.