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 Professor of Mechanical Engineering at Johns Hopkins University,
Rajat Mittal, says he now sees spider crickets as much more than
pests. He says their design principles could aid in the development
of small, nimble robots, with the ability to move across rough
terrain such as earthquake rubble.
Spider crickets are said to leap a distance equal to about 60 times
their body length. And so the question Mittal asked himself was;
"How after jumping this really long distance, how do these animals
manage to control their posture so that they can land on their
feet?"
Mittal and Emily Palmer, an undergraduate research assistant in the
department of mechanical engineering, have studied the intricacies
of the critters' jumps for more than eight months using high-speed
cameras to capture their motion.
"Videos were taken at frame rates that were in excess of 300, 400
frames per second. So that really allowed us to really break down
their entire jump and slow it down and really start to view every
aspect from take-off to the flight and the landing," said Mittal.
Not only was the photography a challenge, but Palmer said it was a
challenge getting "good jumps" from their subjects. Poking crickets
while they were in a plexiglass enclosure encouraged them to jump,
but the details like distance and trajectory were inconsistent.
"We like to track the position of the center of mass which is pretty
much the cricket's stomach, their head and their tail for the entire
jump. And then for one frame in the jump we, like to track those
three points as well as every joint of the cricket's body. So that's
a lot of points to track. And since the crickets are so small, we
need to have very accurate tracking software."
The footage from three cameras was slowed down, and with the help of
software called Matlab, they were able to track the crickets' leaps
and landings.
Mittal said he was surprised to see the insects' jumps were similar
to that of a ballet dancer, but more importantly, they managed to
land on their feet.
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He said they tend to pull everything back in a very streamlined
posture. "After that they go into a mode where they fling their
limbs out. And they start to try to balance themselves in the air
and try to affect the rotation in the air and kind of keep
themselves stable. So all of those very nicely choreographed
movements absolutely bring to mind kind of watching a beautiful
ballet," the professor said.
According to the researchers, the slow-motion video showed that
during flight, the crickets used their limbs to stabilize their
posture and prepare for a safe landing.
Three-dimensional models were created with a software called Maya,
depicting how each insects' body parts move during a leap and
touchdown.
"This kind of a jumping mode of locomotion is very effective when
you're trying to travel through very complicated terrains. For
example, the aftermath of an earthquake where you have all kinds of
rubble," said Mittal, adding extraterrestrial terrain could benefit
from such robots. "Mars could be an example for instance where
jumping could actually be much more effective than anything else,"
he said.
The team presented its findings recently at the 68th annual meeting
of the American Physical Society's Division of Fluid Dynamics in
Boston.
Mittal said that with six to eight more months of research and a
better understanding of crickets' movements, his team may work with
a roboticist to "try to harness some of the principles that we are
finding here."
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