Cyro – large robotic jellyfish

A group of researchers at the Virginia Tech College of Engineering, who previously developed a small robotic jellyfish Robojelly, developed its larger version and named it Cyro – a name derived from “cyanea” and “robot”. The cyanea part of the name originates from cyanea capillata (Lion’s mane jellyfish) – the largest known species of jellyfish it was modeled from.

Jellyfish are interesting to mimic since they use little energy, and could be used to develop less detectable vehicles. They appear in wide variety of sizes, shapes and colors, allowing various 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. Most species are found in shallow coastal waters, but some have been found in depths 7,000 meters below sea level.

Led by Shashank Priya, professor of mechanical engineering at Virginia Tech, the team is building the jellyfish body models, integrating fluid mechanics and developing control systems. Inspired by Lion’s mane jellyfish, they developed a robot with 1.7m (5 foot 7 inches) in length and 77kg (170 pounds) in weight.

“A larger vehicle will allow for more payload, longer duration and longer range of operation”, said Alex Villanueva of St-Jacques, New-Brunswick, Canada, and a doctoral student in mechanical engineering working under Priya. “Biological and engineering results show that larger vehicles have a lower cost of transport, which is a metric used to determine how much energy is spent for traveling.”

As with the smaller models, Cyro’s skin is comprised of a thick layer of silicone. It mimics the sleek jellyfish skin and is placed over a bowl-shaped device containing the electronic guts of the robot. Its body consists of 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.

Cyro is powered by a rechargeable nickel metal hydride battery, whereas the smaller models were tethered. The researchers also carried experiments where they tried to power the robotic jellyfish with hydrogen, but there is still much research to be done in that area.

“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”, said Villanueva. “Our hopes for Cyro’s future is that it will help understand how the propulsion mechanism of such animal scales with size.”

According to researchers, Cyro showed its ability to swim autonomously while maintaining a similar physical appearance and kinematics as the natural species. The robot is able to simultaneously collect, store, analyze, and relay sensory data. This autonomous operation in shallow water conditions is already a big step towards demonstrating the use of these creatures.

With no central nervous system, jellyfish instead use a diffused nerve net to control movement and can complete complex functions. Researchers are performing a parallel study on a bio-inspired control system that could eventually replace the current simplified controller.

Once fully developed, these robots could be used as self-powering, autonomous machines in waters for the purposes of surveillance and monitoring the environment, in addition to other uses such as studying aquatic life, mapping ocean floors, and monitoring ocean currents.