Build Your Own Combat Robot

302 Build Your Own Combat Robot
has higher priority than an object detector. The more sensors the bot has, the
better the information it can process to determine a better reaction.
You can also collect a time history of the data in order to predict where the opponent
will be, and then plan your attack based on the prediction. For example, if your
bot detects that its opponent is off to one side, it can conduct a preplanned attack
move, such as moving forward for 6 inches and then making a U-turn maneuver to
get behind its opponent, instead of just turning toward the opponent. This generally
requires a lot more processing power than a Basic Stamp. There are many
microcontrollers available today that have this type of capability, such as the MIT
Handyboard that uses the Motorola 68HC11 microcontroller, or the Robominds
(www.robominds.com) board that uses the Motorola 68332 microcontroller.
Traction Improvements
As stated earlier, weight and traction are very important in a sumo bot. Most mini
sumos are two-wheeled bots. In the international robot sumo class, there is a wide
range of two-, four-, and six-wheeled bots. And most of them have a single motor
directly driving each wheel. After the bot’s wheels have been modified to have the
highest possible coefficient of friction, and the bot is at its maximum weight, what
is left to increase its pushing power? Increase the robot’s apparent weight.
The way this is done is to add a vacuum system to the bottom of the bot. The
vacuum system then sucks the bot down to the sumo ring, thus increasing the forces
on the wheels, and increasing the pushing power of the bot (assuming the motors
don’t stall!). The rules of the contest prohibit sticking or sucking down to the
sumo ring; but if the robot can continuously move while it’s “stuck,” then the vacuum
system can be used because it doesn’t interfere with motion.
The Japanese make the best vacuum-based sumo bots. These bots are so good
that they can compete on a sumo ring that is upside down without falling off! One
of the drawbacks to the vacuum-based bots is that they can generate so much vacuum
that it literally tears the vinyl surface off the sumo rings. Under the rules of the contest,
if a bot damages the sumo ring, it is disqualified. Unfortunately, once the ring is damaged,
no other bot can use the ring. This is why most clubs specifically prohibit the
use of vacuum systems.
Robot Part Suppliers
There are several companies that sell parts to build sumo bots. Lynxmotion
(www.lynxmotion.com) sells enough parts to build complete and competitive
sumo bots. Figure 13-15 shows a photograph of a six-wheel-drive international
class sumo bot built by Jim Frye of Lynxmotion. This bot has a unique feature
where the front scoop deploys forward after the match starts, which makes it
easier for this bot to get underneath its opponent. This bot also uses a Basic