THIS
MONTH:
Discuss this article in the
SERVO Magazine forums at
http://forum.servomagazine.com
The Cobra
Strikes Again
THE WIRING SNAKE PIT.
www.servomagazine.com/index.php?/magazine/article/september2012_TwinTweaks
Last time, we had the opportunity to introduce the Cobra chassis from Fingertech Robotics. As with any
project, however, our initial endeavors with the Cobra
left plenty of room for improvement. The process of
optimization is often just as important as the initial
design, and we knew that the Cobra chassis deserved
more effort on our behalf to unlock the kit’s true
competitive potential. In particular, we wanted to see if
this bot — trained for the mini Sumo dohyo since its
inception — would be able to broaden its horizons and
serve as an expandable platform for electronics
experimentation. Even though Cobras aren’t known for
SNAKE EYES.
68 SERVO 09.2012
their sharp hearing, we thought an ultrasonic sensor
would be a great way to see if the Cobra chassis could
support more than just a low wedge and a killer drive
train.
The Snake Pit
We think it is important for a roboticist to take pride
in their work. This is why we give our robots names like
Gog and MO, and it’s also a major motivator to take risks,
try new designs, and find success inside and outside of
competition. With our first crack at the Cobra chassis last
time, we were left with a bit of a lumbering behemoth
that couldn’t escape the feeling of being a first draft.
To review, last time we got our hands on the Cobra
mini Sumo chassis. The low profile chassis comes with
high friction rubber wheels, a steel and Garolite base, and
four Spark gearmotors with a mighty 50:1 ratio. The
Cobra chassis is clearly designed to give competitive
roboticists an edge in the mini Sumo competition — the
chassis is low, heavy, powerful, and has the perfect mini
Sumo footprint. We also acquired two TinyESCs —
electronic speed controllers for the motors that are
necessary when your brain doesn’t include onboard motor
drivers.
With all of that awesomeness, the Cobra chassis is
only missing one thing — a brain! Last time, we
transplanted the brain from our Mark III Sumo robot from
Junun Robotics. The physical mounting and power
requirements were not a perfect match, but we were able
to Frankenstein them together and get a final product
