THIS
MONTH:
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Big Trouble in
the Little
Dohyo
THE COBRA MINI SUMO CHASSIS KIT.
www.servomagazine.com/index.php?/magazine/article/july2012_TwinTweaks
For the past few months, we’ve pitted sensors against each other in honor of the upcoming Olympic games,
which will finally kick off at the end of the month. This
time, we thought it would be a great idea to take a look at
one of the most time-honored robotic events of all time:
the mini Sumo competition. In particular, we have the
opportunity to look at a starter kit perfect for the aspiring
mini Sumo master: the Cobra Mini Sumo Chassis from
Fingertech Robotics. To get the chassis ready for action, we
would have to find our inner Frankenstein and track down a
suitable brain. We hoped the result would be more Eva and
less Young Frankenstein. With our soldering iron instead of
scalpel, we set about our surgical saga.
Rise of the Cobra
68 SERVO 07.2012
The mini Sumo competition is a classic robotics event
featured in everything from the massive RoboGames to
small local events. The object of the event is simple: Push
your opponent out of the ring. The field (or dohyo, to use
the historical terminology) is generally a black circle with a
white outline, with a radius that varies depending on the
weight class of the competitors (for the mini Sumo weight
class, the diameter of the dohyo is 77 cm). Sumo robots
generally must comply with width, length, height, and
weight requirements (for the mini Sumo weight class, the
robot can have a max length of 10 cm, a max width of 10
cm, and there is no height limitation; the weight maximum
is 500 g). Other than that, the design possibilities for Sumo
bots are pretty wide open (except you can’t have
flamethrowers or magnets or jammers or anything too
crazy). Sumo is more a study in optimization than wild off-the-wall designs. While combat robots might brandish saws,
jaws, and spinning drums, the sweeter science of Sumo has
a more focused objective than wanton destruction. Pushing
your foe out of the ring effectively requires a specific
combination of traction, a low center of gravity, and a low
wedge. As much as we personally dislike wedges in combat
robotics, they are an intuitive choice for mini Sumo, and the
similarity of the basic robot designs makes for an interesting
comparison of ideas. Who has the best traction? The best
motors? Who was able to save weight on their batteries to
more optimally distribute it with ballast? We always like to
think of the excitement of combat robotics as inherent in
the opportunity to test your ideas against someone else’s,
and Sumo competitions provide plenty of opportunity for
optimization.
