Robotic Sumo Contest
Rules Created by David J. Perdue and Tim Rueger
Description: Robotic sumo is a competition where two robots, known as sumo-bots, attempt to push each other out
of an arena using mechanisms, cunning, and brute force. The arena for the contest is a 4-foot diameter circle, and
the time given for each round is 3 minutes. Your goal is to create a sumo-bot that can push its opponent out of the
arena before being pushed out of the arena by the competing sumo-bot.
Location and Time:
The Sumo-Bots: All participating robots, known as sumo-bots, must be constructed out of LEGO pieces only. They
must also be completely autonomous—that is, acting independently of humans.
Weight and Size: For all participating sumo-bots, the maximum weight allowed is 2 pounds. In addition, there are
maximum width and length specifications:
All sumo-bots must comply with these size limitations at the beginning of a bout, but can expand beyond these
limitations after the bout has begun.
Please note that your sumo-bot(s) will be checked for weight and size specifications before being admitted. You will be
given one chance to reduce your sumo-bot’s weight and/or size if it exceeds the 2-pound weight limit and/or the width
and length limits. Sumo-bots that fail to meet these specifications will not be allowed entry.
Allowed Parts: The robots for this robotic sumo competition revolve around the use of the Robotics Invention System
(RIS) and the RCX microcomputer contained in the RIS. Only stock Lego-manufactured parts may be used - no part
may be altered or modified. The allowed parts are:
The Programming: All contestants must use the standard firmware (versions 1.0 or 2.0) for their RCX—no custom
firmware please. Multiple programs on the RCX are allowed. If, during the event, any contestant deems it necessary to
change or update his or her program(s), he or she may do so, as long as the contestant’s sumo-bot is not currently
participating and is not currently needed on the arena. The programming languages, within the RCX’s standard
firmware, admitted are:
The Robotic Sumo Arena: The competition takes place in a circular arena 4 feet in diameter. The surface is painted
glossy white and is bordered with a black, glossy line 2 1/2 inches wide. The arena is made out of 3/4-inch BC grade
plywood sanded smooth on one side; the smooth surface will be used for the sumo-bots. During play, the arena will
be raised approximately 3 inches above ground.
Judging: The judges for the competition will be Tim Rueger, David Perdue, and a volunteer to be named at the
competition. A single judge will oversee each match. Tim will act as the primary judge. For matches where Tim
competes, David will be the active judge. For matches where both Tim and David compete, the volunteer will be the
active judge. In any match, the judge will have sole discretion and in any dispute the judge’s decision is final.
Prizes: The winner and runner up of the competition will receive Lego prizes. Prizes will have a retail value of
$30-$50, and will be announced prior to the competition.
At the beginning of a round, the sumo-bots will be placed approximately 5 inches apart from each other in a parallel
position. The sumo-bots must begin the round by moving in opposite directions; active searching is enforced in
this way. The judge of the round will verify with the current contestants that their sumo-bots are positioned on the
arena in a way which will result in them initially traveling in opposite directions. Please note the following:
Bouts within a round are over when the following happens:
Sudden Death: A sudden death is a 1-minute round whose purpose is to resolve which sumo-bot is the winner from
a previous, expired 3-minute regular round. In sudden death, both sumo-bots are repositioned and started remotely
by the judge as is normally done. If no sumo-bot is found to be a winner at the end of 1 minute, the judge will toss a
coin to determine the winner. All sumo-bots declared winner in sudden death will be judged by normal scoring
standards, except those determined by flipping a coin (see below).
A Replay: A replay is always initiated at the end of a bout if the 3-minute round isn’t up or if an entanglement has
occurred. A replay consists of stopping the clock, repositioning both sumo-bots, starting the sumo-bots, and then
turning the clock back on.
The End of the Round: After three victories, 3 minutes, or a sudden death, the round is declared over. Both sumo-
bots will be awarded points, and the sumo-bot with the most points will be awarded a win. Here is the point system:
The Determination of a Round: All rounds will be determined by a judge. All of the judge’s decisions are final. Any
participant who argues may be disqualified.
Various Rules: In addition to the main set of rules, there are a few other rules that must be recognized for the safety
and fairness of all participants:
Tournament play: The tournament will be conducted in two rounds: round-robin matches and a single-elimination
tournament. The winner of the single-elimination tournament will be declared champion.
Round-robin matches: Robots are separated randomly into small groups. Within a group, every robot plays every
other robot one time. Sizing of groups and the schedule of matches will be determined based on the number of
entries and announced prior to the match. Round-robin rounds are scored as described above. A robot’s final score
from the first round is the sum total of its scores in its round-robin matches.
Single-elimination tournament: Seeds in the tournament are determined by scores from the first round. If the
tournament bracket is not filled, entrants with the highest scores receive “byes” in the first round. Ties in seedings will
be broken randomly. Second-round matches are conducted as described above; the winner of the final match of the
single-elimination tournament is declared champion of the event. The loser of the final match will be declared runner-
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