SERVO 09.2013 27
If the movies have taught us anything, it's that chopping a futuristic death
robot's leg off does not significantly diminish its capacity to hunt
Now, there’s a real robot who can work when “injured.” This
bot has a five-legged gait that moves it along at 18 cm/s, as
compared to the undamaged 26 cm/s gait. Not bad,
considering that an unmodified five-legged gait had it limping
along at just 8 cm/s.
The cool thing about this recovery model is that it
doesn't require any specific information about what parts
are malfunctioning or missing. Instead, it's just got a known
model of how it's supposed to work, and if the actual
performance that it measures is less efficient, it starts
searching for new behaviors.
To get all sciencey about it:"The robot will thus be able to sustain a functioning behavior when damage occurs by
learning to avoid behaviors that it is unable to achieve in the real world." Umm ... are we sure this is a good thing?
WHEGS GONE WILD
This little legged robot from Johns Hopkins is
quick. It can travel at over 30 body lengths every
second, which works out to over two meters per
second (or four and a half miles an hour). If you were
travelling at 30 body lengths every second, you'd be
going 122 miles an hour. Yeah. Think about that.
This robot — which still doesn't have a name — is
very compact (just 6. 5 x 5. 5 x 1 centimeter), and
according to its creators is quite possibly "the fastest
legged robot of its size." Whether or not this really is a
legged robot (or a quadruped) is perhaps debatable.
These are wheel-legs, more commonly known as
They're wheels in that there's rotary motion going on, but they're also legs in that there are discrete
points of contact with the ground. To some extent, whegs offer the best of both worlds. They can be
directly driven with conventional motors, and allow for high speed and efficiency while simultaneously
providing traction over rough terrain and obstacles. Plus, you can easily swap them out and by making them
out of springy materials, you can give your robot some compliance.
What makes this robot wicked fast is the fact that it's got four independent drive motors — each one
of which has a power-to-weight ratio that's absolutely bananas. Only six millimeters in size each, the motors
output 1.5 watts of power at 40,000 RPM, driving the individual whegs through 16:1 planetary gearheads.
They're not cheap (hundreds of dollars each), but they make for one crazy little robot. Of course,
independently driven whegs make the robot smaller, lighter, simpler to steer, and generally more efficient
Unfortunately, the current generation of this robot isn't capable of taking advantage of all of the power
that the motors offer. Even at top speed, it's only using about 0.60 watt — less than half of what the motors
can output — since increasing wheel speed causes the robot to bounce along the ground, decreasing its
actual speed. There's a lot of potential for swapping in some new whegs up to 35 mm in length (about twice
as long as those currently on the robot) "which might produce even faster running speeds and the ability to
navigate very large obstacles or challenging terrain, with a robot that still fits in your hand."