bots IN BRIEF
JUMP TO IT
Jumping can be a great way to get around. It's far more efficient than
flying and much more versatile than driving or walking or crawling.
Jumping robots need a big burst of power to get off the ground, but after
20,000 jumps’ worth of analysis, researchers at Georgia Tech have
found a secret that makes robotic hops ten times more efficient: It's a
stutter (a little jump) right before the first big jump.
That's it. That's the secret. It's simple, but it makes a huge difference.
Daniel Goldman, one of the authors on a paper published in Physical
Review Letters, explains:
“If we time things right, the robot can jump with a tenth of the
power required to jump to the same height under other conditions. In
the stutter jumps, we can move the mass at a lower frequency to get off
the ground. We achieve the same takeoff velocity as a conventional jump,
but it is developed over a longer period of time with much less power.”
How much less power you ask? Up to ten times less. The jump takes
longer to make because of the initial hop that's required, but that seems
like a small price to pay to keep your robot bouncing ten times longer on
the same amount of power.
This trick works with "pogo stick" jumping robots which are bots
that use springs to store energy. Georgia Tech built themselves the most simple jumping robot possible to run their
experiments; it consists of a leg, a spring, and an actuating mass. They expected to find that the optimal jumping strategy would
be related to the resonant frequency of the system, but after ten thousand tests or so, it turned out that frequencies above
and below the resonance led to optimal jumping. That's where the stutter jump comes from.
You can check out the robot at http://crablab.gatech.edu/pages/
jumpingrobot/ Demo.html for yourself. It’s a nifty little interactive part of the
website that lets you virtually mess around with the jumping robot used in these
The researchers plan to keep on experimenting with this robot on a variety
of surfaces, including sand and disaster-type environments.
A linear motor was attached to an air bearing for near
frictionless 1D motion. Due to the weight of the air
carriage, the apparatus was slanted to an angle of
θ = 75° to reduce the gravity load on the motor to 0.276 g.
Total mass load on the spring: m = 1.178 kg
Spring stiffness: k = 5. 8 kN/m
Damping ratio: ζ 0.01 (from video tracking data of free
Lift-off was detected at a rate of 1,000 Hz by reading the
voltage of a circuit that would open and close at the
interface of the bottom of the spring and the metal base.
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