manta ray robot

Manta ray robots glide through water like their real-life counterparts

Image credit: reuters

An underwater robot that looks and moves like a manta ray using only single motors and flexible fins has been developed by Singapore researchers.

Manta rays are known as one of nature’s most efficient and graceful swimmers and their unique propulsion method has long fascinated scientists.

It allows them to cruise through even turbulent seas, flapping their pectoral fins effortlessly to drive water backwards.

Academics have spent years trying to mimic the wing-like movements of rays’ pectoral fins - but Chew Chee Meng of the National University of Singapore says it’s the first to use single motors for each fin and rely on the interplay of fluid and fin.

Bio-locomotion has been studied for about 30 years but there is still a lot of work to be done on understanding the fluid flow around bio-robotic fins and the interaction between fluid and structure in flexible fins such as Chew’s manta ray robot.

By creating a passive fin from a single PVC sheet, rather than trying to mimic its movements with a series of motors and joints, Chew’s team found the robot interacted more naturally and efficiently with its environment.

“You’re not fighting against the hydrodynamics of the system,” said Chew.

The robot, dubbed MantaDroid, has a flat black PVC body with ray-like fins and two rear rudders, which moves through water like its natural counterpart.

Chew said the fin’s passive flexibility allows it to interact naturally with the water, propelling it at a speed of 0.7 metres per second, to cover about twice its body length.

The Singaporean team went through 40 different fin designs over two years before settling on using flexible PVC sheets.

The MantaDroid can swim for up to 10 hours. Chew and his team from the university’s engineering faculty plan to test the robot in sea waters and incorporate more modes of movement into its fin mechanism.

He said the team is also working on a ray twice the size of the 35cm original, and believes such robots would be useful for studying marine biodiversity, gathering hydrographic data and underwater search efforts.

The MantaDroid is part of a growing field of biomimetics, which applies learning about natural systems and robotics to the design of new vehicles, said Thomas Atwood, executive director of the US National Robotics Education Foundation.

Robots such as the ray, he said, could help carry out underwater mapping and ocean bed surveys, besides military reconnaissance.

Another recent example of biomemetics includes a new type of stretchable surface with programmable 3D texture morphing inspired by the skin of the octopus and the cuttlefish. 

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