Jellyfish-mimicking robots could be built to service future offshore wind farms in place of the underwater remotely operated vehicles (Rovs) used today in order to protect often rich ecological maritime environments at project sites, according to a new study out of the UK.
Starting from Rovs’ need for “efficient, long-distance navigation across open stretches of water” and the ability to “handle tasks requiring high manoeuvrability close to submerged structures”, a team at the University of Southampton is developing a new-look design based on the jellyfish’s “pulse-jet swimming mode” rather than flapping fins, which until now has been the main inspiration for this type of service unit.
“Both types of robot [long distance and high manoeuvrability] are effective, but few robots combine efficient travel with high manoeuvrability. That means most aquatic robots are too clumsy and clunky to support the offshore industry without also harming the undersea environment,” team leaders Thierry Bujard and Gabriel Weymouth wrote in a recent article in Science Robotics.
“Indeed, with the expansion of offshore developments to increasingly fragile environments, even state-of-the-art marine robots are struggling to cope with the complexity of their missions.
“The pulse-jet swimming mode favoured by jellyfish is widely regarded as the world’s most efficient underwater propulsion mechanism, offering a more compelling technological solution that’s far easier for roboticists to imitate.”
A marine machine concept based on pulse-jetting – which is powered by the cyclic expansion and contraction of a hollow cavity of the jelly-fish’s body that drives ingestion and expulsion of water to propel the creature – could answer both the need for long-haul travel and dexterity in completing complex tasks offshore, the researchers believe.
“Despite its simplicity, this swimming strategy can result in incredible agility as well as being highly energy efficient. The fastest squid can travel up to eight metres per second using a pulse-jet system, while the Aurelia aurita [moon jellyfish] is known to be the most efficient swimmer on the planet.
“By copying these organisms when we build underwater robots, we can design new underwater vehicles capable of combining high manoeuvrability with unmatched efficiency.
“In our recent research, we developed a new bio-inspired robot that can match the propulsive efficiency of the Aurelia aurita. To do this, we mimicked the key principle that enables jellyfish to achieve their high propulsive efficiency.”
The envisage jelly-fish-inspired robot, which would be run off an “elastic propulsive system” based on inner chamber that expands and collapses “umbrella-like”, when tank-tested was found to speed-up as it pulsed.
“The efficiency of a system that propels itself, be it mechanical or biological, is based on an equation that combines the power absorbed, the speed of the system and its mass. When applied to our robot, that equation put our robot jellyfish on par with the Aurelia aurita jellyfish,” said the researchers.
Though a fleet of these new-look marine machines is some way off, the Bujard-Weymouth team see their industrial logic is compelling: “After millions of years of evolution, aquatic creatures should offer models to help address the weaknesses of the current crop of underwater robots.”