October 18, 2013
Building Better Robots Based On Natural Jellyfish Movement
Michael Harper for redOrbit.com - Your Universe Online
This past spring, researchers with the Virginia Tech College of Engineering unveiled Cyro, a robotic jellyfish roughly the size of a full-grown man. The robot borrowed swimming techniques from actual jellyfish and could one day be used by the military to autonomously survey the waters, map the sea floors and even monitor the changing climate.Understanding the way jellyfish move through the water was only part of the challenge of creating a robotic version, and now the team, in partnership with researchers from the Marine Biological Laboratory and Providence College, is explaining just how efficiently these jellyfish swim. Rather than exhaust their muscles by pulsing constantly, jellyfish use physics to help them move along. This smart movement allows these umbrellas of the sea to use about 48 percent less energy than other animals as they move around.
The authors of the new paper, published in the journal Proceedings of National Academy of the Sciences, are expected to continue research into robotic jellyfish and ultimately will help the US Navy as these devices come to life.
When observing a jellyfish, one notices a long pause in between the expansion and contraction of its body. The Virginia Tech researchers say it’s this moment of stillness which actually helps push the creature along. As it moves forward, its bell-shaped body creates a sort of “hole” behind it. When this hole is filled once more with water, it propels the jellyfish forward. Using this displacement, the jellyfish is able to let physics propel it as it expends as little energy as possible. In doing so, the swimmer can travel 30 percent farther with each stroke cycle compared to other swimmers, which must constantly expend energy to move.
“The fluid is helping the jellyfish to move and conserve the energy,” summarized Shashank Priya, professor of mechanical engineering at Virginia Tech. “The fluid is actually pushing them, and when that energy dissipates, they contract again.”
To study the jellyfish, Virginia Tech’s Colin Stewart created a computer model of the jellyfish, thereby allowing the team to study the animal in a simulated environment. According to Stewart, digitizing the way the animal moves is “remarkably difficult,” and he was left relying on a technique used by Hollywood directors to create CGI effects. Part of the difficulty, said Stewart, is the soft structure of the jellyfish. These soft edges of its muscular structure are hard to digitize and took some extra work.
With the model now complete, teams will place these computerized versions through a series of simulations to build a better robotic jellyfish. The newest versions of these jellyfish are much smaller than Cyro, and measure about the size of a human hand, as can be seen in a recent video. They’ve also been built in a variety of shapes, including one that more resembles a mushroom cap.
Even as Cyro was unveiled earlier this year, the researchers under Priya were eager to improve their design.
“We hope to improve on this robot and reduce power consumption and improve swimming performance as well as better mimic the morphology of the natural jellyfish,” explained Alex Villanueva, a doctoral student in mechanical engineering. “Our hopes for Cyro’s future is that it will help understand how the propulsion mechanism of such animal scales with size.”