Lego® Sumobot

Note: All rules are subject to change without notice.

Name of Event: “There can be only one”
Number of Robots per Match: 2
Length of Match: 2 minutes
Robot Weight Limit: 2 pounds

Objective: To push or flip opponent’s robot out of a circular ring. The first robot to touch the floor outside of the ring loses. The last robot remaining in the ring wins.


1.0   Definition of the Sumo Match

1.1.      Definition

A match consists of two teams, each composed of one or more members.  Only one team member may approach the ring; all others must watch from the audience. In accordance with the game rules, each team competes on a Dohyo (sumo ring) with a robot that they have constructed themselves to the specifications in Section 2. Each match starts at the judge’s signal and continues until one team has earned two points. The judge then determines the winner of the match.


2.0   Technical Requirements for Lego® Sumobots

2.1.      Robot Specifications

  1. A robot must fit within a 12 x 12 inch square frame (no limit on height)
  2. The total mass of a robot must be equal to or under 2 pounds.
  3. A robot may expand in size after a match begins, but may not physically separate into pieces.
  4. All robots must be completely autonomous.
  5. The robot must be built entirely from LEGO® pieces in original factory condition without restriction on types or quantity.
  6.  The robot cannot be held together by any means other than standard LEGO® construction methods (no stickers, tape, glue, oil, ect…)
  7. The onboard computing device must be one of the following: Lego® Scout, Spybots, MicroScout, RCX or NXT programmable bricks. Homebrew sensors,    multiplexors and all other modifications to LEGO® elements are prohibited.
  8. Acceptable electrical parts include only:
    • Parts manufactured and distributed by LEGO®
    • EGO® licensed parts from third party manufacturers such as Hi Technic


2.2       Robot Restrictions

  1. No interfering with another robots sensor is allowed.
  2. No parts that could damage the ring are allowed.
  3. No parts that are intended to break the opponent’s robot are allowed.
  4. “Normal” pushes, bangs & lifting are not considered intent to damage.
  5. No devices that can store liquid, powder, gas or other substances for throwing at the opponent are allowed.
  6. No flaming devices are allowed.
  7. No devices projectiles are allowed.
  8. No sticky substances to improve traction are allowed. Tires and other components of the robot in contact with the ring must not be able to pick up and hold a standard A4 paper (80 g/m2) for more than two seconds.
  9. No devices to increase down force, such as a vacuum pumps or magnets are allowed.
  10. No edges may be sharp enough to scratch or damage the ring, other robots, or players.


3.0   Requirements for the Dohyo  (Sumo Ring)

3.1.      Dohyo Interior

The dohyo interior is defined as the playing surface surrounded by and including the black border line. Anywhere outside this area is called the dohyo exterior.

3.2.      Dohyo Specifications

  1. The ring is circular in shape with a 4’ diameter and made out of 1/8” painted white plywood.
  2. The border line is marked as a black 2 inch circular ring. The ring area extends to the outside edge of this circular line.
  3. For all given dohyo dimensions a tolerance of 5% applies.

3.3.      Doyho Exterior

A 4 foot clear space around the outer edge of the ring. This space can be of any color, material or shape as long as the basic concepts of these rules are not violated. This area, with the ring in the middle, is to be called the “ring area”. Any markings or parts of the ring platform outside the minimum dimensions will also be considered in the ring area.

4.0    Sumo Matches

4.1.      Format

Each “match” consists of 3 “rounds”.  Each round is 2 minutes, unless extended by the judges. The winner of each round is awarded 1 point. In the event of a tie no points are awarded for that round. The first robot to get 2 points is the winner of the match. In the event of a tie after 3 rounds, the judge may elect to flip a coin to decide which robot is superior, and declare it the winner.

Depending on how many robots participate one of the following elimination methodologies (in order of preference) will be used:

1. 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.

2. 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.

3. 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. Contestants have one minute to position their robot in the ring and to be ready to start. Robots that are not ready are given a warning and  an additional minute to prepare their robot. After a second warning the contestant forfeits the round and the opposing robot gets a point.

Once the robots are positioned, the judge announces the start of the round. The contestants immediately activate their robots and step away from the ring. They may not do anything more to control their robots until the round is over. The robots must not move for the first 4 seconds of the round.

4.2.      Points

A robot is declared the winner of a round and awarded 1 point when:

  1. The other robot starts to move before 4 seconds.
  2. The other robot is pushed or drives off the ring and any part of it is touching the floor below the ring (not the black line).
  3. The other robot stops moving for 10 seconds (it shall be considered not having the will to fight), or if it falls over “on the ring” and becomes immobilized in any way for 10 seconds. This is the case even if the first robot also stops moving or becomes immobilized during the 10 seconds.
  4. A Judge considers the other robot to be unsafe.

The round will be stopped and re-started when:

  1. Both robots are in a clinch or entangled and have not moved for 10 seconds, or move in the same orbit for 10 seconds, with no progress being made.
  2. Both
    robots stop (at the same time) and stay stopped for 10 seconds without touching each other.
  3. Both robots drive or are pushed/pulled out of the ring at about the same time, and it cannot be determined which touched the floor first.
  4. If it is not clear if progress is being made or not, the Judge can extend any of the rounds by 10 seconds for up to a total of 30 seconds each.

If there is no winner within 2 minutes, the match is declared a draw.

If the match is tied, the judges will decide which robot is the winner of the match.  The judges will take the following merits into consideration:

  1. Technical merits in movement and operation of each robot.
  2. Attitude of the players during the match

5.0   Check In & inspection

5.1.      Check In

Prior to the start of the tournament all teams will be required to check in and receive a team number.

5.2.      Robot Inspection

All robots will be measured, weighed, and inspected prior to approval for competition. The website will be used to determine if a part is an original Lego® element. If you plan to use any hard to find special pieces present a parts list with Lego® item numbers during inspection.

5.3.      Robot Software

No restriction on software used at this time.


6.0   Start, Stop, Resume, & End a Match

6.1.      Robot Placing

Upon the judge’s instructions, the two teams approach the ring and place their robots in the ring. The winning robot from the previous round places their robot in the ring second. In the first round the judge will assign which team places their robot first. A cross in the middle divides the sumo ring into 4 quadrants. Robots always have to be placed in 2 opposing quadrants. Each robot has to point in the opposite direction. The robots can be placed anywhere within the quadrant. The judge will remove the cross after positioning of the robots. After placing, the robots in the ring they may not be moved until after the round.

6.2.      Start

When both contestants are ready, the ring judge will signal the start of the round at which time the robots must be activated (the contestants must physically push a switch or button on the robot to activate the program). No movement can occur before the official start (no posturing). All robots are required to have a four second delay before moving otherwise they will be disqualified. Players must exit the Ring Area once the robots have been activated. Both robots must move to their respective edge of the circle before contacting the other robot.

6.3.      Stop, Resume

A. Should one robot become disabled (flipped on it’s back or side, for instance) and unable to move, the ring officials will award the victory to the remaining robot. If it is determined by the judge that both robots are stuck in an entanglement or deadlock for at least 10 seconds, the judge will call for a reset.

B. If the judge declares a reset, the clock is stopped, the robots are put back in starting positions, and the robots will be reactivated and clock restarted. A match is over after 2 minutes or after one “Win” occurs.

6.4.      End

The round will continue until one unit is disabled or removed from the ring. A robot is considered to be “removed” from the ring when any part of it falls off the edge and touches the floor. A robot whose body hangs over the edge is not considered off until it physically tips off the edge and touches the floor. Judgment of the ring officials is final. A robot that disables or removes the opponent gets a “Win” credited to it, and if a robot drives off the board and suicides, the other robot gets a “Win” credited to it.


7.0   Time of Match

7.1.      Duration

One Match will be last for a total of 6 minutes, starting and ending upon the judge’s command.

7.2.      Extension

An extended round, if called for by the judge, shall last for a maximum of 2.5 minutes.

7.3.      Time Keeping

The following are not included in the time of the Match:

  1. The time elapsed after the judge announces start and before the match resumes.
  2. The standard delay before the match resumes shall be 30 seconds.
  3. The time elapsed after a judge announces to stop the match and before the match resumes.


8.0    Violations

8.1.      Insults

A player who utters insulting words to an opponent or to a judge or puts voice messages in a robot to utter insulting words or writes insulting words on the body of a robot, or performs any insulting action, is in violation of  these rules.

8.2.      Minor Violations

A minor violation is declared if a player:

  1. Enters into the ring during the match, except when the player does so to take the robot out of the ring upon the judge’s announcement.
  2. Performs any of the following actions:
  3. Asked to stop the round without good reason.
  4. Takes more than 30 seconds before resuming the match, unless the judge announces a time extension.
  5. Delays in starting the robot after the judge signals the start of the round.
  6. Does or says that which disgraces the fairness of the match or his team.


9.0   Penalties

9.1.      Penalties

  1. Players who violate these rules by performing the deeds described in Sections 8.1 shall lose the match. The judge shall give two points to the opponent and order the violator to leave the ring. The violator is not honored with any rights.
  2. Each occasion of the violations described in Sections 8.2 shall be accumulated. Two of these violations shall give one point to the opponent.
  3. The violations described in Article 8.1 & 8.2 shall be accumulated only throughout one match.


10.0 Injuries and Accidents during the Match

10.1.      Request to Stop the Match

A player can request to stop the game when he/she is injured or his/her robot had an accident and the game cannot continue.

10.2.      Unable to Continue the Match

When the game cannot continue due to player’s injury or robot’s accident, the player who is the cause of such injury or accident loses the match. When it is not clear which team is such a cause, the player who cannot continue the game, or who requests to stop the game, shall be declared as the loser.

10.3.      Time Required to Handle Injury/Accident

Whether the game should continue in case of injury or accident shall be decided by the judges. The decision process shall take no longer than five minutes.


11.0 Declaring Objections

11.1.   Declaring Objections

  1. No objections shall be declared against the judges’ decisions.
  2. The lead person of a team can present questions to the judge, before the match begins, if there are any concerns in the exercising of these rules.


12.0 Miscellaneous

12.1    Flexibility of Rules

As long as the concept and fundamentals of these rules are observed, they shall be flexible enough to encompass the changes in the number of players and of the contents of matches. The local event organizer can make modifications or abolition of the rules as long as they are published prior to the event, and are consistently maintained throughout the event.

12.2    Rule Updates

Rule updates will be posted on the NoVa Sumobot web page. Teams are responsible for checking this site for changes, clarifications, and corrections prior to competing.

12.3    Consideration

Robots must have enough power and stamina to compete for potentially 12 to 36 minutes throughout the tournament. Please consider battery accessibility when designing your robot.

During a match no changes in programming or construction of the robot are allowed. Between matches programming and design changes are allowed but will require re-inspection prior to competing in the next match. All teams are honor bound to report changes to the inspection judges. If changes are made and not reported this will result in forfeiting that match.

At the end of each match, the contestants are responsible for making sure the ring is clean and ready for the next match to begin.

13.0 Liability

13.1    Robot Damage

Participating teams are always responsible for the safety of their robots and are liable for any accidents caused by their team members or their robots. The nature of this contest may cause accidental damage to participating robots. The ring will be elevated above the floor approximately 2 inches, which may cause some pieces to separate. All robots should be designed with this in mind.

13.2    Liability

NoVa Sumobot will not be responsible nor liable for any incidents and / or accidents caused by participating teams or their equipment. Each team member will be required to submit a waiver/hold harmless form during the check in process. This can be downloaded from the NoVa Sumobot website.