by the aerodynamics of flying insects, a project to build a wee
winged robot takes off
By Robert Sanders,
UC Berkeley engineers
with the Center for Information Technology Research in the Interest of Society (CITRIS), aiming to build a robotic fly the size of a quarter have attained
a major milestone with the creation of a tiny wing that flaps like
a real fly wing and generates lift.
conception of the micromechanical flying insect. It rests
on a tripod of solar panels, has polyester wings and stainless
steel struts to flap and rotate the wings. Courtesy
brings them closer to their goal of having, by the end of 2003,
a robot weighing a tenth of a gram - less than the weight of a paper
clip - that lifts off the ground and hovers.
thing for us has been to build a wing mechanism which can
both flap and rotate simultaneously at 150 times per second,
the same speed as a fly's wings beat," said Ronald Fearing,
professor of electrical engineering at UC Berkeley and the
principal investigator for the project. "What we've shown
is that we've got force in at least one direction, which is
an important milestone."
scheme to build a miniature winged robot is one of many innovative
projects underway at CITRIS, which is headquartered
at UC Berkeley and one of four California Institutes for Science
A robotic fly
like this, which the team calls a micromechanical flying insect
or MFI, could be used in search and rescue or reconnaissance - "keeping
people out of harm's way," Fearing said - or even, as he said facetiously,
to seek and destroy insect pests in a field of corn.
"There's a big
gap between the traditionally engineered robot, which is very slow,
heavy, dangerous and expensive, and what nature builds, which is
lightweight, fast, high-performance and very robust," he said. "It's
these capabilities of natural systems that we wanted to capture
in a mechanical system."
A flying robot
also avoids a big problem of miniature legged and wheeled robots.
"They get stuck in the shag carpeting," he said.
which is funded by the Defense Advanced Research Projects Agency
and the Office of Naval Research, is possible because of recent
discoveries about the way flies flap their wings and achieve the
great maneuverability required for acrobatic feats like landing
on the ceiling. Much of this has been discovered by Michael Dickinson,
professor of integrative biology at UC Berkeley and a recent MacArthur
"genius" award winner.
the last of three key ingredients necessary to make a fly fly,"
These wing motions
are delayed stall, which enables beating wings to have a high angle
of attack and high lift at the same time; wing rotation at the bottom
and top of the stroke, which, like the backspin on a baseball, gives
more lift; and wake capture, whereby a wing gets extra lift by swishing
back through air it set in motion on the previous stroke.
"These are the
main aerodynamic secrets for flying insects with beating wings at
this size scale," Fearing said. "This aerodynamic breakthrough is
going to make the MFI possible."
Fearing, professor of electrical engineering
The goal of Fearing's
project, which began in 1998, is to duplicate these wing motions
in a fly-sized robot and, with proper computer control, get the
device to fly stably under its own control without crashing into
In the past three
years, he and his team have miniaturized many pieces of the MFI,
including the motors. The most recent achievement was a wing-drive
thorax composed of thin sheets of stainless steel that, when cut
and folded into "beams," turn out to be extremely strong. Two hinged
beams are attached as struts to each wing, with a piezoelectric
motor driving them. When they move together, the wing flaps; when
they move out of sync, the wing rotates.
"The wings can't
do fancy figure eights or ovals, but they can do simple things,
like flap and rotate," Fearing said.
The wings, about
half an inch long, 1/20 the thickness of a sheet of paper and made
of lightweight polyester, look like miniature paddles, and give
the fly a wingspan of about one inch.
Still to come
is a lightweight power source, probably solar panels integrated
into the robot's tripod legs, perhaps a gyroscope to tell up from
down, and a light sensor. A microprocessor with a small operating
system, called TinyOS, has already been developed at UC Berkeley
for devices of this size.
MFI would carry sensors chosen for a specific use. "Because of the
revolution in MEMS (microelectromechanical systems), something this
small could carry quite a few instruments," Fearing said. "A nose
to track pollution plumes, a very low-power communications system,
a lightweight imaging device to snap pictures. The electronics and
sensing is more advanced now than the robot."
All this for
a few dollars in materials, Fearing predicts. A commercial version
of the MFI could be on the market in 10 years, he said.
"We really have
a unique team working on this project," Fearing said, "a whole variety
of engineers - mechanical, electrical, computer and materials scientists
- all taking inspiration from our biology colleagues."