After reading about David Cook's Bugdozer a year and a half
ago, I knew I wanted one of my own. Shockwave is a mini sumo that is the result
of a year's worth of building and planning. Initially, I wanted a box-like
robot that dropped a flap at the start of the match. However, testing
demonstrated that the flap touched "out" every time it approached the
edge.
Discarding this design, I went in favor
of a fifteen centimeter long robot with a wedge in front that dropped itself
down at the match's start. Unfortunately, the robots profile prevented me from
fitting all the necessary components inside. Furthermore, I couldn't get enough
weight on the wheels for my liking.
Accordingly, I considered cloning Bugdozer.
This solved all the problems that I had encountered with the previous designs.
Unexpectedly, two issues arose: first, I could no longer break the opponent's
traction (wedging under the opponent to get their wheels of the ring) and the
center of gravity became unacceptably high.
After a considerable amount of
brainstorming, I went for a six-wheel-drive, bidirectional, box like robot
that dropped a high friction pad in the front and in the rear. My strategy used
the pads to prevent opponent's wedge from sliding under my robot and employed
brute force (Maxon motors and six magnetic wheels) to out push them. I planned
on finishing this robot and taking it to the Robothon 2004, but they changed
the rules, disallowing magnetic mini sumos. So, I promptly shelved the project
and altered the design.
The new design conceived a low profile
wedge that didn't have enough room for me to fit in all the necessary
components. Even after reshaping the shell a little, I failed to solve the
problem. Actually, what I had in mind was a smaller version of Aftershock,
but with a 45 degree wedge (back then, I lacked the capability to cram the
necessary amount of components into a small space). After changing the
shape of the robot to become more like a right triangle, I had a design that
pleased me. Finally, a layout featuring enough room for the parts, could break
the opponents traction, fairly easy to build, and a good weight distribution.
Up until this point, my previous prototyped circuits consisted of logic chips.
The amount of components needed to build the circuits proved so large and
convoluted that they flooded three breadboards! Switching to BASIC Stamps verified
a wise choice indeed! I found out later that the robot's center of gravity attested
unacceptably high. Oh well. Fortunately, I learned early on the importance of
speed, unlike my earlier designs that were geared for increased torque. :-)
Shockwave's speed helped it defeat all the other competitors
in less than 5 seconds, save the first bout when it drove out of the ring due
to me not calibrating the sensors correctly. In all likelihood, I would not
have disassembled Shockwave, but later that Saturday evening, after the Junior
League mini sumo, I had the honor of facing Grant Mckee's robots Enders Wraith and
the partially running Solo.
Because of its marginal success against Mr. Mckees robots, I
knew I needed a more competitive design. The culprits causing my loses included
a dead edge sensor, a high center of gravity, and no front sensors. Looking
back, I regret disassembling Shockwave, as it got itself and I a lot of
attention rather quickly, look at this,
and this (thanks for your compliment, Chris)! Due to the
unusually long planning and building phase, this is probably the most
educational project I have undertaken so far.
