Batoid rays, such as stingrays and manta rays, are among nature’s most
elegant swimmers. They are fast, highly maneuverable, graceful, energy efficient,
can cruise, bird-like, for long distances in the deep, open ocean, and rest on
the sea bottom.

“They are wonderful examples of optimal engineering by nature,”
said Hilary Bart-Smith, an associate professor of mechanical and aerospace
engineering in the University of Virginia’s School of Engineering and Applied
Science.

Bart-Smith and her colleagues at three other universities are trying to
emulate the seemingly effortless, but powerful, swimming motions of rays by
engineering their own ray-like machine modeled on nature.

They are designing an autonomous underwater vehicle (AUV) that someday may
surpass what nature has provided as a model. The vehicle has potential commercial
and military applications, and could be used for undersea exploration and
scientific research.

Sometimes called bio-mimicry—the attempt to copy nature—Bart-Smith calls her
work “bio-inspired.”

“We are studying a creature to understand how it is able to swim so
beautifully, and we are hoping to improve upon it,” she said. “We are
learning from nature, but we also are innovating; trying to move beyond
emulation.”

Bart-Smith’s team, which includes researchers at U.Va., Princeton
University, the University of California-Los Angeles, and West Chester
University, are modeling their mechanical ray on the cow-nosed ray, a species
common to the western Atlantic and Chesapeake Bay.

The team members, who are experts in marine biology, biomechanics, structures,
hydrodynamics, and control systems, have created a prototype molded directly
from a real cow-nosed ray. By studying the motions of living rays in the field
and the laboratory and through dissection, this prototype attempts to replicate
the near-silent flaps of the wing-like pectoral fins of a ray, to swim forward,
turn, accelerate, glide, and maintain position.

“Biology has solved the problem of locomotion with these animals, so we
have to understand the mechanisms if we are going to not only copy how the
animal swims, but possibly even to improve upon it,” Bart-Smith said.

Her team is trying to achieve optimal silent propulsion with a minimum input
of energy.

The mechanical ray is remotely controlled by researchers through computer
commands. 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.

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 scientists, or as a surveillance tool for the military. It
also could be scaled up, or down, to serve as a platform carrying various
payloads, such as environmental monitoring instruments. For example, it
possibly could be used for pollution monitoring, such as tracking the locations
of underwater oil spills.

And because the vehicle looks and behaves like a common sea creature, it
likely would operate in the sea without affecting natural creatures or their
habitats.

Source: University of Virginia