While plesiosaurus are now extinct, modern engineers are taking inspiration from their method of swimming to a robotic vehicle.
Plesiosaurus were air-breathing marine reptiles with long necks and sleek bodies which thrived during the early to middle Jurassic Period, between 135 million to 120 million years ago. Plesiosaurus used four paddle-like flippers of nearly equal size and musculature to swim.
Today’s seafaring animals such as penguins, sea turtles and sea lions have evolved to rely on their larger and stronger front flippers for primary propulsion, while using their smaller back flippers for steering. Even though the plesiosaurus’ method of swimming has been superseded in nature, they were widespread and prolific in their time. The team of researchers from the University of Southampton were inspired to explore how swimming with four flippers might be advantageous compared to two.
Previously, the researchers used tandem flippers in a water tunnel and showed that the back flippers can achieve a significant performance boost by operating in the wake of the upstream flipper, increasing thrust by 60 percent and efficiency by 40 percent.
They are now working to apply this tandem-flipper enhancement to a swimming robotic vehicle. According to Gabriel Weymouth, an associate professor for the Southampton Marine and Maritime Institute at the University of Southampton, his team of students built a robotic vehicle, called Atlantis, based on the swimming style of plesiosaurus could enable highly efficient and manoeuvrable exploration of the ocean floor.
“The students built a fully autonomous robot from scratch and designed it to be powered using only two motors, one for each side,” Professor Weymouth said.
“To achieve this, each flipper pivots freely on its axle and requires no motors, sensors, or control systems. This greatly simplifies the mechanism and reduces the cost of the vehicle.”
The pivot of each flipper was optimised using open source fluid dynamics software to maximise efficiency and thrust. When tested, the researchers found the vehicle to be quite fast and highly manoeuvrable.
The work demonstrates that a very simple mechanism can be used to take advantage of the tandem flipper enhancement used by the plesiosaurs.
The researchers will continue to further optimise the design, control and flipper shapes of the vehicle, in an effort to develop the concept into a field-ready autonomous vehicle.
[Image: Atlantis in the water. Credit: GDP Atlantis/Kate Devereux, Angus Clark, Lucy Lowe, Nick Copsey, Abi Basham, Joe Watkins and Vincent Lam.]