Mini Sumo

Chapter 1: Definition of a Match

Article 1 – Definition

A Sumo contest involves two contestants who operate robots, that they have made themselves, by having the robots push their opponent out of the sumo ring (Dohyo) according to the game rules presented here. The individual contest continues until two Yuko points are scored by one of the contestants.

The overall contest is structured using a double elimination tournament format, where each robot must lose two matches to be eliminated from the tournament.

Chapter 2: Dohyo Specifications

Article 2 – Definition of the Dohyo Interior

The dohyo interior is defined as the dohyo area surrounded by and including the border line.

Article 3 – Dohyo

A dohyo is a flat cylinder which is illustrated in the image below. The geometrical dimensions of the doyho are listed in the table below for the different robot divisions.


Division Diameter Height Border Width Starting Line Length Starting Line Width
3kg (R/C and Autonomous) 154 cm 5 cm 5 cm 20 cm 2 cm
Mini 77 cm 2.5 cm 2.5 cm 10 cm 1 cm
Micro (pending) 38.5 cm 1.25 cm 1.25 cm 5 cm 0.5 cm
Nano (pending) 19.25 cm 0.6 cm 0.63 cm 2.5 cm 0.25 cm
  • The dohyo can be made out of any material as long as the geometrical specifications are maintained.
  • The top surface must be flat and smooth with no dents, indentations, bumps, seams, creases, folds, edges, or any other defect that can interfere with the motion of the robot.
  • The color of the dohyo surface will be non-glossy black.
  • The starting lines (Shikiri-sen) are indicated as two parallel brown lines (color ratio = blue : red : yellow = 4 : 4 : 2). They are centered on the dohyo and the seperation distance between them is equal to the starting line length.
  • The outer edge of the dohyo, the border line, is indicated as a glossy-white colored circular ring with a width as defined in the table above with an outside diameter equal to the diameter of the dohyo. “On the border” is defined as being within the interior of the dohyo.
  • The referee can decide, at any time during the games, whether the dohyo can continue to be used or whether it should be replaced due to damage.

Article 4 – Dohyo Exterior

The exterior area of a dohyo extends at least 100 cm from the border line. The color of the exterior can be any color except white. There are no restrictions on the type of material that can be used or the shape of the exterior, as long as they do not violate the spirit of the rules.

Chapter 3: Robot Specifications

Article 5 – Specifications

The following table lists the size and weight limitations for both autonomous and remote control robots for the various robot weight divisions.

Division Length Width Height Max-weight
3kg (R/C and Autonomous) 20 cm 20 cm Unlimited 3 kg
Mini 10 cm 10 cm Unlimited 500 g
Micro (pending) 5 cm 5 cm 5 cm 100 g
Nano (pending) 2.5 cm 2.5 cm 2.5 cm 25 g
  • The robot must be able to fit inside a square box with a length and width as described in the table above.
  • The robot’s weight (including accessories) must not exceed the maximum weight for its weight division.
  • There are no restrictions on the type of control method used with autonomous robots.
  • There are no restrictions on the type of microprocessor or the amount of memory used in the robot.
  • There are no restrictions on the locomotion design. Examples include: wheels, tank-style treads, or walkers (including humanoid).
  • An autonomous robot should be designed to begin action no earlier than five seconds after the contestant presses the robot’s start button.
  • Applicable to R/C robots only:
    • The handheld wireless remote control unit is excluded from the weight limit per individual robot.
    • Usable frequencies are 27 MHz (channels 1 to 6), 49 MHz (channels 1 to 5), 50 MHz (channels 00 to 09), 75 MHz (channels 61 to 90), and 2.4 GHz spread spectrum.
    • Multiple remote-control units cannot be used per individual robot.
    • The robot must use an AM\FM frequency or 2.4 GHz DSM approved by the tournament officials for the receiver and transmitter.
    • Applicable to 2.4 GHz systems: The DSM transmitter and receiver must have its GUID code locked in via the binding process. This is required by the FCC to help prevent a collision of frequency channels and illegal use of a particular frequency channel at the same time by multiple controllers.
    • Applicable to an AM or FM system: The robot must allow operation on 3 different frequencies; legal primary and\or sub-frequencies. This is most likely achieved with detachable crystals in the transmitter\receiver pair. Tournament officials may require you to change your robot’s transmitter and receiver crystals due to frequency conflicts with other robots at any time during the tournament. It is your responsibility to provide the detachable crystals.

Article 6 – Restrictions on Robot Design

  • The robot will not include a device that obstructs the control of the opponent’s operation, such as a jamming device or strobe light.
  • The robot will not include any parts that might damage or deface the dohyo.
  • The robot will not include a device that insufflates (pour, spill, drop, ooze, eject, fire, shoot, squirt, etc) any liquid, powder, or gas.
  • The robot will not include an inflaming device.
  • The robot will not include a throwing device.
  • The robot will not include any part that fixes the robot to the dohyo surface and prevents it from moving (such as suckers, glue, and so on). The robot must always be able to move.

Chapter 4: Game Principles

Article 7 – Robot Divisions

3kg Sumo Division

  • This division is intended for any robot weighing 3kg or less and not exceeding the specifications listed in Article 5.
  • There will be two competition divisions, Remote-Control and Autonomous.
    • Remote-Control 3 kg Sumo Division:
      • This division is intended for remote-controlled sumo robots.
      • Autonomous robots are permitted to compete in this division.
    • Autonomous 3kg Sumo Division:
      • This division is intended for autonomous (self controlled) only robots.

Mini Sumo Division

  • This division is intended for any robot weighing 500g or less and not exceeding the specifications listed in Article 5.
  • Only Autonomous robots compete in this division.

Micro and Nano Divisions

  • These divisions are pending weight divisions for future events.
  • Existing robots are permitted to compete in any of the above contests.

Rumble Divisions

  • See Article 22.

Article 8 – Game Principles

  • A game consists of three matches of three minutes each. The first contestant to win two Yuko points is the winner of the game.
  • The contestant who has the most Yuko points at the end of the game will be judged as the winner.
  • When neither contestant receives any Yuko points, or both contestants have one Yoko point, the winner will be decided by the judges. The judge will select the winner based on which robot was the most aggressive robot. However, if no obvious superiority exists and a winner cannot be determined, an extra three-minute match can be played.

Chapter 5: Game Procedure

Article 9 – Beginning of the Game

Before the match, the contestants greet each other outside the dohyo following the chief referee’s instructions, then enter the dohyo. After that, the contestants put their robots on or behind their starting lines. No part of the robot can be placed in front of the starting line before the match begins.

  • Prior to the start of a match, the entire robot must fit inside a square box as defined for the weight class. At any time after the start of the match, the robot can expand outside these dimensions.
  • Autonomous Sumo Robots:
    • At the referee’s signal, the contestant can press the start button on the robot. The match begins five seconds after the referee’s signal. The contestant must exit the dohyo when the match begins.
  • Remote Controlled Sumo Robots:
    • At the referee’s signal, the contestant can begin to operate the robot with a remote-control unit.

Article 10 – End of the Game

The match ends when the referee calls the winner. Both contestants will thank each other for a fair and competitive match after removing their robots.

Article 11 – Game Cancellation and Rematches

A match will be stopped and a rematch will be started under the following conditions:

  • The robots are locked together in such a way that no more action appears to be possible or they rotate in circles several times.
  • Both the robots are moving, but they don’t appear they will ever contact each other.
  • Both robots touch the exterior of the dohyo at the same time.
  • Any other conditions under which the referee judges that no winner can be decided.
  • In case of a rematch, maintenance of competing robots is prohibited until a Yuko is observed, and the robots must be immediately put back to the location specified in Article 9.
  • If neither of the competing robots win nor lose after a rematch, the referee may reposition both robots to a specified location and restart. If even that does not yield a winner, the match may continue at any location decided by the referee, until the time limit is reached.

Chapter 6: Yuko (Effective) Points

Article 12 – Yuko Points

Under The following conditions a Yuko (effective) point is awarded:

  • When a robot ejects its opponent from the dohyo with a fair action. The robot is considered ejected the moment any part of the robot touches any part of the exterior of the dohyo. A robot hanging over the edge of the dohyo or touching any part of the cylindrical side of the dohyo is not considered ejected, and the robot is still in play.
  • When the opponent’s robot steps out of dohyo on its own (for any reason).
  • When the opponent’s robot is disqualified or has had more than one violation or warning.
  • When two Yusei points are given.
  • When a Yusei point is awarded when the opponent has already been given a warning.
  • Is awarded to a contestant when their opponent is given a second warning.

Article 13 – Yusei Points

The following condition is determined as Yusei (advantage) points:

  • When the opponent’s robot gets stuck on the border line and cannot move off the border line on its own.

Chapter 7: Violations and Penalties

Article 14 – Warnings

A contestant who takes any of the following actions will receive a warning:

  • The operator or any part of the operator (remote control, for example) enters the dohyo before the referee’s call ends the match.
  • Preparation for the restart of a match takes more than 30 seconds.
  • A remote-controlled robot begins action (physical expansion or moving) before the chief referee’s start signal.
  • An autonomous robot begins action (physical expansion or moving) within five seconds after the chief referee’s start signal.
  • Any other actions that may be deemed unfair occur.
  • When a contestant continues to complain (verbally or non verbally) about a referee’s decision, condition of the dohyo, or environment, after the officials have made an attempt to correct the problem.

When a contestant receives two warnings, the contestant’s opponent will be awarded one Yuko point.

Article 15-Violations

Any of the following actions is determined as a violation, and the offender’s opponent, or both robots, will get a Yuko point:

  • A part (or parts) of the robot that exceeds a weight of 10 grams is separated and dropped from the robot.
  • The robot stops moving on the dohyo for more than 10 seconds.
  • The robot emits smoke.

Article 16 – Loss by Violation

A contestant who takes any of the following actions will lose the game by violation:

  • A contestant does not attend the appointed dohyo when called at the beginning of the game.
  • A contestant ruins the game, such as by intentionally breaking, damaging, or defacing the dohyo.

Article 17 – Disqualification

A contestant who takes any of the following actions will be disqualified and forced to leave the game:

  • A contestant’s robot does not meet the robot specifications stated in Article 5.
  • A contestant makes a robot using a method restricted in Article 6.
  • A contestant displays unsportsmanlike behavior. For example, using violent language or slandering an opponent or a referee.
  • A contestant intentionally injures their opponent’s operator.

Chapter 8: Injury and Accidents

Article 18 – Request for Suspension

When a contestant is injured due to the operation of the robot or the robot has an accident, and the game cannot be continued, a suspension can be requested by the contestant.

A referee must take immediate action necessary to take care of this situation.

Chapter 9: Objections

Article 19 – Objections to the Referee

No objections to the judgment of the referee can be raised.

Article 20 – Objections to the Rules

A contestant who has an objection to the operating rules must express dissent to the Tournament Committee before the end of the game.

Chapter 10: Specifications of Robot Markings

Article 21 – Marks on the Robot

The robot must not be marked with any words, symbols, or images that are offensive to the general public.

Chapter 11: Others

Article 22 – Rumble

The rumble is a single sumo match with up to 16 different robots to determine which robot can remain on the dohyo after all the other robots have been pushed off the ring.

  • The rumble will be played on the same size, or next size larger, dohyo for the weight class.
  • The maximum number of robots on the dohyo at one time is 16.
  • Time limit is 5 minutes.
  • At the start, each robot must be a minimum of one robot diameter away from its nearest competitor.
  • A rumble match consists of only a single match. It is not a best 2 out of 3 match system like regular sumo matches.
  • When a robot is pushed off the dohyo, the operator must immediately remove, or turn off, the robot from the vicinity of the dohyo. The operator must not interfere with the operation of any robots still competing.
  • If more than one robot remains on the dohyo after the 5 minute time limit, the winner will be chosen by the judge using the criteria of which robot was the most agressive.
  • Remote control robots are not allowed to compete in an autonomous robot rumble.
  • Autonomous robots are permitted to compete in a remote control rumble (space permitting).
  • Lighter weight class robots are permitted to compete in a heavier weight class rumble (space permitting).

Article 23 – Modifications and Abolition of the Rules

Modifications or abolition of the rules are made by the decision of a general assembly of the Tournament Committees held according to the Rules of Tournament Committees.

The rules presented here follow the official Japanese Robot Sumo rules as of 7/4/2002. Main differences are the addition of different weight classes, the changing of the radio frequencies to frequencies that meet FCC regulations, clarifications to certain rules, clarification of R/C robot specifications, and changing the material of the Dohyo to any material.

The operating rules for all of the weight divisions are the same. The only difference between them are the sizes of the robots and sumo ring for the different weight classes, compliance of remote-control design to 3 frequencies (AM or FM systems), and starting conditions for remote-control and autonomous robots.

———————- New content as of 7-14-2022

Liability – Each contestant is fully responsible for any damage to person or property caused directly or indirectly by his or her robot.  The SRS, the event organizers, judges and other entrants are not responsible for damage caused by any competing robots.  Each contestant must sign the waiver of liability form prior to the competition.  A minor must have a guardian present to sign their waiver.

Please reference a copy of the waiver here that each contestant will need to sign in-person before competing.

Code of Conduct – All builders, handlers and spectators are expected to comply with our organization’s code of conduct, please reference these SRS rules here.

These SRS rules also apply to all event staff. Please keep the event fun and light-hearted for all, including the organizers and humans.