Robofish needs almost no juice to glide

MICHIGAN STATE (US) — A robotic fish equipped with an array of sensors can glide long distances using little to no energy.

The robofish, which can gather data on water temperature and quality, can also swim.

“Swimming requires constant flapping of the tail,” says designer Xiaobo Tan, associate professor of electrical and computer engineering at Michigan State University, “which means the battery is constantly being discharged and typically wouldn’t last more than a few hours.”

Xiaobo Tan’s lastest verison of the robotic fish swims in a tank in his lab. (Credit: G.L. Kohuth)

Electrical engineering doctoral students Feitian Zhang (left) and Jianxun Wang work on Grace, the robotic fish. (Credit: G.L. Kohuth)

The disadvantage to gliding, he explains, is that it is slower and less maneuverable.

“This is why we integrated both locomotion modes—gliding and swimming—in our robot,” Tan adds. “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.”

The robot’s ability to glide is achieved through a pump that pushes water in and out of the fish, depending on if the scientists want the robot to ascend or descend.

Also, the robot’s battery pack sits on a kind of rail that moves backward and forward, in sync with the pumping action, to allow the robot to glide through water on a desired path.

The robotic fish is named Grace, which stands for “Gliding Robot ACE.”

Late last year Tan and his team took Grace for a test drive on the Kalamazoo River, where it exceeded all expectations.

“She swam at three sites along the river and wirelessly sent back sensor readings,” Tan says. “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.”

The KalamazooRiver is the site of a 2010 oil spill. Interestingly, the robot’s crude oil sensor had some readings upriver from where the spill occurred, although the readings downstream from the spill site were higher.

Underwater gliders, or seagliders, are becoming more common in oceanography. In fact, one traveled all the way across the Atlantic Ocean in late 2009.

One major difference in Grace is that, aside from its swimming capability, it is about 10 times smaller and lighter than a commercial underwater glider.

The National Science Foundation supported the work.

Source: Michigan State University