Lego Sumo Spring 2008

Contest Date: 
Sat, 05/03/2008

Lego Sumo
Contest Rules

Audience: Apprentice or Journeyman Level


Two self-controlled robots are placed in a ring and try to avoid falling out or avoid being pushed out by the opponent robot. The first robot that touches outside of the ring loses the round.  The first robot to win two rounds, wins the match.

Course Construction

Pound of Wood ready to put your robot down!The Lego Sumo ring is a 4 foot diameter, 3/4 inch thick wood disc.  This disc is surrounded by an exterior empty space at least 6 feet in diameter.  This space must not contain any people, objects, lights, or anything else that would distract or interfere with the robots.

The top surface of the ring is painted flat black with a 1” shiny white border. Two brown starting lines are each 1 centimeter in width (3/8 inch) by 25.6 centimeters (32 Lego studs) in length, centered 96 centimeters (16 Lego studs) from the middle of the ring.  Therefore, the starting lines are a total of 25.6 centimeters (32 Lego studs) apart from each other. 

The ring is raised slightly to make it easier to determine when a robot has been pushed out.  This vertical edge can be any color (white, black, or even unpainted).

The exterior space can be any color but white

Robot Construction

Lego Sumo robots follow the Chibots general robot guidelines with the following exceptions:

1.      Lego Sumo robots must have a mass of 1000 grams (2.2 pounds) or less.

2.      Lego Sumo robots must be made only of official or compatible Lego pieces. They also must use Lego processors

3.      Robots are not allowed to increase weight during a round.  For example, a helium-filled balloon cannot be used to lighten a robot during weigh in and then deflate during a round.

4.      At the start of each round, Lego Sumo robots must not exceed 25.6 centimeters (that is 32 Lego studs) in width and/or depth.

5.      Robots may expand to any size after starting. 

6.      No remote controls during the round.  So, it is acceptable to remotely control the robot before the beginning of the round (including a remote start button) and after the end of the round (including a remote stop button).

7.      There is no height limit, as soon as movement is allowed in a round, the robot may then twist, fall, and/or expand without size limits.

8.      Lego Sumo robots must not

·        Emit smoke or fire

·        Leak, stain, or soil

·        Disperse powder, grit, or grime

·        Spray, throw, or use projectiles

·        Jam, shock, or electromagnetically interfere with more than sensors

·        Snare, entangle, or employ nets/rope

·        Scratch, gouge, or scrape within reason.  This is a pushing contest so some scraping may occur.

·        Fly or generate lift to isolate itself from the ring surface.  The "no-fly" rule is not intended to prevent a robot from having a floating portion (such as a camera, sensor, flag, or distraction) nor to prevent jumping or other interesting behavior.  The robot qualifies as long as a major portion of the robot is generally available to be pushed out by the opponent robot.

·        Use suction, "sticky wheels", magnets, or other methods of increasing downward force.  If the robot is placed on a 8” x 8” index card and lifted up, index card should lift for no more than 3 seconds.

Electronics (sound or light emitters) or physical techniques (reflective or non reflective surfaces) that attempt to trick the opponents sensors are permitted, so long as they are not dangerous, do not discourage audience viewing (strobes, lasers), and do not result in permanent sensor damage.

Throughout the contest, the algorithms, settings, and components in the robot may be shaped, angled, or configured differently for facing each opponent and may be placed in different starting positions.  A reasonably identifiable core must remain and none of these changes are allowed to alter the robot beyond the qualification requirements.

Batteries and parts can be swapped during the contest, so long as a reasonably identifiable core robot remains consistent throughout and the mass does not exceed the mass recorded at the initial weigh in.  Upon entering the external area to begin a round, if an opponent or judge challenges the robot as now being non-qualifying or being more massive than at the initial weigh in, it will be re-measured.  

Robots are permitted to fall apart or split into multiple pieces / robots.  This includes leaving beacons or lures.  This rule encourages potentially creative or interesting designs, and it allows insignificant parts to be dislodged without automatically losing.  However, any piece that leaves the ring (purposely or not) causes the robot to lose the round.

Robots that wish to utilize video are permitted to receive unprocessed video frames (single or streaming) from an off-board video system.  The off-board setup must be outside of the 100 cm external area and must be accepted by the judges as not interfering with the contest.  This rule encourages innovation in robotic vision.

Contest Procedure

Pound of Wood barely squeezing in.Each robot is measured and inspected to verify qualification.  A digital scale will be used for determining mass.  For width and depth, a carefully measured box or cube is placed over the robot as shown.  Usually this box will be built of Legos to ensure the 32 Lego stud interior dimensions.  The robot must start each round of the contest in an orientation and physical position that would fit in the box.

As part of the qualification process, the robot will be required to play one match (i.e. three rounds) against a test one pound block of wood.  Like normal matches, failure to beat the test block in three minutes results in a tie round for the contestant.  The results determine seeding for the contest in the following order: fewest losses, most wins, and lowest initial weigh-in mass.  Top seed faces bottom seed.

Robots may be altered between rounds and matches, either for repairs, battery changes or reconfiguration.  A modified robot must still fit within the qualification parameters and not have a mass greater than the initial weigh-in mass.  The judge may re-examine the robot at any time to verify this.

Multiple entries, even identical ones, by a single builder are permitted.  The contestant must have a willing designate to operate one robot if two robots from the same builder play a match.  A builder may strategically forfeit rounds or matches to manipulate their entries payoff placement, during seeding or in the contest.

The robot that just won the prior round (or better-ranked robot if no prior round) is positioned first.  The builder may place the robot in any position, angle, or location on the ring except that no portion of the robot may cross the extended starting line nearest the contestant.

The second contestant may place his or her robot in any position, angle, or location on the ring except that no portion of the robot may cross the extended starting line nearest the contestant. The robot must fit within the required starting dimensions (20 cm x 20 cm).

After the initial placement of the first robot, it is not permissible to alter its starting position.

Each robot is started either manually or remotely.  Robots may have multiple start buttons, strategy switches or starting configurations to allow more than one opening move.  So long as the first robot's position is not altered (which would result in a warning), the contestants may alter settings or press buttons until the point at which the start button is pressed.  Upon starting, no additional control, commands, configuration, or information may be communicated to the robot.

Both contestants place their fingers on their robot's starting buttons and await the judge's signal.  If a problem is encountered before the judge says, "go", a contestant may alert the judge, without penalty, that the robot is not ready.  For example, a robot may fall or slip when a finger is place over the start button.

Upon pressing the start buttons, the contestants immediately leave the exterior area around the ring.  During the round, all people and objects must be kept out of the ring and exterior area to avoid distracting the robots or altering the outcome.

Upon pressing the start buttons, each robot must not move at all for five seconds. However, countdown lights, buzzers, sounds, or other entertaining motionless activities are allowed.

During the countdown, if the contestant notices their robot has failed to start its countdown, the contestant may alert the judge and halt the countdown.  Both robots are reset to start the round over.

The contestant is given a warning.

If a robot begins moving during the five-second period, the robot has committed a false start.  A warning is issued and both robots are reset to start the round over.

A second warning of any kind in a single round results in the robot losing that round.

A robot loses a round when any portion (including touch sensors, whiskers, scoops, or skirts) of the robot touches outside of the ring.  It does not matter if the robot falls out on its own or is pushed out.

The first robot touching outside of the ring loses, even if the second robot subsequently touches outside of the ring.  If the judge determines that both robots touched outside of the ring at the same time, the round is nullified and started over.

Touching the raised edge of the wall itself is also considered out.

If any piece of the robot, no matter how small or even if detached, touches outside of the ring, the robot is considered out.  For example, if a nut drops off a robot within the ring, the robot does not immediately lose. However, if the nut is then pushed out or rolls out, the robot loses.

If a robot lands outside the ring atop a whisker, scoop, or any portion of the opponent robot, the opponent robot is out.  This is consistent with the policy that the robot that touches outside first is out, even if the second robot subsequently touches outside the ring.

Starting to fall or breaking the plane of the ring is not considered out; some portion of the robot must actually touch outside the ring.

At any time after the five-second starting countdown is over, a contestant may choose to enter the exterior space or otherwise signal stoppage to the judge.  That contestant's robot loses the round.

A builder that communicates with a robot, attempts to distract (such as with an IR or laser emitter), or in any way attempts to interfere with the outcome is also considered signaling stoppage.

At the judge's discretion, the judge may choose to restart a round if:

·        Three minutes have expired

·        No progress has been made in some period of time

·        The robots fail to touch each other for some period of time

·        The robots are hopelessly entangled or otherwise deadlocked

·        Both robots fail to start or both contestants signal stoppage

At the judge's discretion, the judge may choose to end a round and choose the round winner if:

·        Smoke, fire, damage, or any other violation has occurred

·        No progress is likely to be made even if the round is restarted

·        The first robot to win two rounds, wins the match.

·        A match may also end if a contestant or robot is disqualified or otherwise unable to complete.

In the event that the judge cannot decide the winner of a round (for example if both robots seemed to fall out at the same time), the judge has the sole discretion to re-run the round or declare the winner based on lowest mass on the initial weigh-in.

Non-moving robots qualify.  No rounds shall be ended by the judge for a non-moving robot, although a contestant can still halt (forfeit) the round if desired.  However, in the event of a tie after three minutes, the most active robot shall be declared the winner of the round.

If it fails, the robot shall lose the entire match.  Two failures and the robot is disqualified from the contest.

Round Re-Tries:  In the event that the judge cannot decide the winner of a round (for example if both robots seemed to fall out at the same time), the judge has the sole discretion to re-run the round or declare the winner based on lowest mass on the initial weigh-in.


Depending on how many robots participate, the judges will decide between one of the following elimination methodologies (in order of preference):

·        Round Robin: Each robot faces every other robot, one at a time, in a match.  This is the preferred method of play, but will not be used if the judges decide time does not permit.

·        Double Elimination: Upon losing two matches, the robot is out of the contest.  The first round will pit the highest ranked robot against the lowest ranked robot.  The set of winning and losing robots from this first round will be pitted against each other in future rounds.  That is we will use a winners and a losers bracket.

·        Single Elimination: Upon losing a match, the robot is out of the contest.

The judges may decide to use Heats if too many contests are participating.  In a heat, the robots are divided into smaller groups and one of above methods is used within each group to organize one-on-one matches. The winners of each group advance and may compete using a different method from that point forward.

Rounds and matches are played in order and on time.  Upon being called to begin a round, the contestant has one minute to position their robot and to be ready to start.  Robots that are not ready (fail to start or fall from their starting positions) are given a warning.  Another minute is given.  A second warning forfeits the round.

In the event of a tie, a “sudden death round” may be required if the tie persists.  In this round, the two robots in questions will compete until one is victorious.

This page is a rule set for this general contest: