N.C. researchers build robot bats

By Jay Price - The (Raleigh, N.C.) News & Observer

RALEIGH, N.C. -- Someday one of the first acts of a rescuer searching for a missing aircraft or survivors in a collapsed building might be flinging dozens of bats into the air. The bats would have muscles of wire and flap away silently on wings of titanium alloy and silicon membrane.

N.C. State University researchers are building tiny, inexpensive robots that would mimic the still-mysterious flight skills of bats to maneuver inside small enclosed spaces, slip through dense forest or spread out in an evenly spaced flock to relay cell-phone signals from a lost hiker or conduct a search over a large area.

Scientists at NCSU's Department of Mechanical and Aerospace Engineering have built several prototypes of the equivalent of a bat's skeleton using metal alloys with startling properties and some of the growing body of data about how bats fly.

Because bats can do things like zip into the corner of a room and in three quick strokes be traveling in the opposite direction, they're a great model for tiny flying machines that must be more maneuverable than, say, tiny airplanes or rotary-wing craft, said Stefan Seelecke, an associate professor overseeing the project.

The idea was to take advantage of the work nature has already done in designing an elegant approach to flight, Seelecke said.

“There are about 900 kinds of bats, too, so there are a plenty of different (flight) characteristics among them,” he said. “They're a great template to work from.”

The thin body shells of the cyberbat prototypes and some of the wing “bones” are made of a light-weight plastic, shaped by computer. The outermost bones are made of a titanium and nickel alloy that scientists call a shape-memory metal because it provides a full range of natural motion — doing the job of joints, tendons and ligaments — then returns to its original position.

Gheorghe Bunget, a doctoral student in mechanical engineering who is building the bats, showed off the material Friday by bending one of the metal bones in half and releasing it. It sprang back undamaged.

Each “muscle” that moves a part of the wings, meanwhile, is made of a single strand of so-called smart metal wire half the diameter of a human hair. When heated, it rearranges its atoms and shrinks rather than expands as metals normally would. That means it can be made to contract like a muscle, then returns to its previous position when it cools.

The whole prototype weighs about as much as six paperclips.

Seelecke thinks that if the robot critters work they could be mass-produced and used in inexpensive flocks.

The researchers are finishing work on the joints, muscles and a silicon wing membrane, and by the end of summer should have a model that flaps its wings properly. They can then begin to gather data from its performance so that the motion can be optimized for flight. Next, they will need help from other scientists to develop a tiny computerized control system and an internal power source.

Bunget will present the research at a national engineers' conference in two months.

The NCSU engineers have gotten some help from a lab at Brown University in Rhode Island that specializes in studying the movement of bats' wings. It has gone so far as to put bats in wind tunnels.

Bats' wings are much more sophisticated than an airplane's or a bird's, said Daniel Riskin, a biologist doing post-doctoral research at the Brown bat lab. If you created a radio-controlled model of a bird's wings, he said, it would need perhaps two or three controls. If you did the same for a bat, you would need about 20 to govern all the ways it could move.