Navy, Virginia Tech partner on robotic jellyfish to monitor seas

That thing you see in the ocean one day might not really be a monster jellyfish that mutated to the size of a human being, but rather the outcome of a university project to develop a autonomous robot for the U.S. Navy.

Researchers at the Virginia Tech College of Engineering have been working on a life-like, autonomous robotic jellyfish that has the dimensions, 5 feet, 7 inches in length and weighing 170 lbs., of a human being, an April 3 university news release said.

The prototype robot builds on previous work on the same concept that was unveiled in 2012. The new robot, nicknamed Cyro, is far bigger than the earlier robot, known as RoboJelly, which was the size of a regular jellyfish encountered along beaches. Shashank Priya, a Virginia Tech professor of mechanical engineering, has been leading the research efforts made possible with Navy funding.

The larger model allows for more payload, longer duration and longer range of operation, the researchers said. “Biological and engineering results show that larger vehicle have a lower cost of transport, which is a metric used to determine how much energy is spent for traveling," said Alex Villanueva, a doctoral student in mechanical engineering working under Priya.

Both projects are part of a multi-university,$5 million project funded by Naval Undersea Warfare Center and the Office of Naval Research. The goal of the research program is to place self-powering, autonomous machines in waters for the purposes of surveillance and monitoring the environment. In addition, the robots envisioned will be able to handle other missions such as studying aquatic life, mapping ocean floors, and monitoring ocean currents.

Jellyfish are attractive candidates to mimic because of their ability to consume little energy owing to a lower metabolic rate than other marine species, according to the researchers. What's more, they appear in wide variety of sizes, shapes and colors, allowing for several designs.

They also inhabit every major oceanic area of the world and are capable of withstanding a wide range of temperatures in both fresh and salt waters, the researchers noted. Most species are found in shallow coastal waters, but some have been found in depths 7,000 meters below sea level.

Other universities in the project are Providence College, R.I., the University of California at Los Angeles, the University of Texas at Dallas, and Stanford University. Priya’s team is building the jellyfish body models, integrating fluid mechanics and developing control systems, Virginia Tech said.

Cyro is modeled and named after the jellyfish cyanea capillata, Latin for “lion’s mane jellyfish,” with “Cyro” derived from “cyanea” and “robot,” the researchers said. As with its predecessor, this robot is in the prototype stage, years away from use in waters. A new prototype model already is under construction at Virginia Tech’s Durham Hall, where Priya’s Center for Energy Harvesting Materials and Systems is based.

Work is ongoing to improve on the robot by reducing its power consumption and improving its swimming performance, as well as better copying the morphology of the natural robot, Villanueva said. “Our hopes for Cyro’s future is that it will help understand how the propulsion mechanism of such animal scales with size," Villanueva said.

A stark difference exists between the larger and smaller robots, the researchers said. Cyro is powered by a rechargeable nickel metal hydride battery, whereas the smaller models were tethered, they said. Experiments have also been conducted on powering jellyfish with hydrogen but there is still much research to be done in that area.

In both cases, the jellyfish must operate on their own for months or longer at a time as engineers likely won’t be able to capture and repair the robots, or replace power sources, the researchers said.

The robot can maneuver in water by a rigid support structure with direct current electric motors which control the mechanical arms that are used in conjunction with an artificial mesoglea, or jelly-based pulp of the fish’s body, creating hydrodynamic movement, the researchers said.

With no central nervous system, jellyfish instead use a diffused nerve net to control movement and can complete complex functions, the researchers said. A parallel study on a bio-inspired control system is in progress which will eventually replace the current simplified controller.

As with the smaller models, Cyro’s skin is comprised of a thick layer of silicone, squishy in one’s hand, the researchers said. It mimics the sleek jellyfish skin and is placed over a bowl-shaped device containing the electronic guts of the robot. When moving, the skin floats and moves with the robot, looking weirdly alive.

 

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