Mantabot – manta ray biomimicry for underwater vehicles

Inspired by batoid fishes, such as stingrays and manta rays, researchers from University of Virginia (U.Va.) and their colleagues from 3 other universities are developing an autonomous underwater vehicle that emulates the seemingly effortless but powerful swimming motions of rays. The vehicle has potential commercial and military applications, and could be used for undersea exploration and scientific research.

Although they seem graceful while they glide in the water, rays are fast, highly maneuverable, energy-efficient, and well adapted to cruise on long distances in the deep, open ocean, and rest on the sea bottom. Led by Hilary Bart-Smith, an associate professor of mechanical and aerospace engineering in the U. Va.’s School of Engineering and Applied Science, the researchers modeled their mechanical ray on the cow-nosed ray – a species common to the western Atlantic and Chesapeake Bay.

“They are wonderful examples of optimal engineering by nature,” said Bart-Smith. “We are studying the creature to understand how it is able to swim so beautifully, and we are hoping to improve upon it. We are learning from nature, but we also are innovating; trying to move beyond emulation.”

Aside researchers at U.Va., the team consists out of members from Princeton University, the University of California-Los Angeles and West Chester University. They used their expertise in marine biology, biomechanics, structures, hydrodynamics and control systems, to create a prototype of the bioinspired autonomous underwater vehicle.

In order to create the prototype, they molded its shape directly from a real cow-nosed ray. The plastic body of the vehicle contains electronics and a battery, while the flexible silicone wings contain rods and cables that expand and retract and change shape to facilitate what is essentially underwater flight. This feature enables the prototype to replicate the near-silent flaps of the wing-like pectoral fins of a ray, to swim forward, turn, accelerate, glide and maintain position.

The mechanical ray is remotely controlled by researchers via computer commands. Bart-Smith’s ultimate goal is to engineer a vehicle that would operate autonomously, and could be deployed for long periods of time to collect undersea data for environmental monitoring. Due to the fact the vehicle looks and behaves like a common sea creature, it could operate in the sea with less impact on natural creatures or their habitats.

One of the goals the researchers are trying to achieve is to create optimal silent propulsion with a minimum input of energy – a feature suitable for lower impact on the natural creatures around it, as well as for a stealthy surveillance tool for the military.