Micro Sumo — Official Rules

1. Definition of the Sumo Match

1.1 Definition

A match is fought between two teams, each with one or more members. Only two members may approach the ring: the operator and the assistant. Others must watch from the audience. Under these rules, each team competes on a Dohyo (sumo ring) with a self-built robot meeting Section 2. The match starts on the judge’s command and continues until a contestant earns two Yuhkoh points. The judge determines the winner. After the match, the operator and assistant return to the assigned room and await the next game.

2. Requirements for Robots

2.1 General Specifications

• Any design is allowed unless limited by Section 2.2.
• Robot must fit within a 50 × 50 × 50 mm cube at start.
• Total mass at start must be under 100 g.
• The robot may expand after the match begins, but may not separate into multiple pieces and must remain a single centralized robot. Feet must not expand. Parts totaling < 5 g falling off do not cause a loss.
• Robots are fully autonomous; all control must be onboard.
• A visible competition number (provided by organizers) must be affixed to the outer shell.

2.2 Restrictions

• Robot must have an IR start/kill interface operable by the judge. On kill, motor power must shut down. The IR start module must be present and functional at inspection and in all matches; otherwise the team is disqualified. Teams may implement their own receiver or use the organizer module (see Appendix 3).
• No jamming (e.g., IR LED flooding).
• No components intended to damage the ring or opponent; normal pushing is allowed.
• No liquids, powders, gases, flames, or projectile devices.
• Sticky traction prohibited. Contact surfaces must not pick up and hold an A4 sheet (80 g/m²) for more than 2 s.
• Downforce devices (vacuum, magnets) are not allowed in Micro Sumo (permitted only in Mega Sumo).
• Blade and any expansion must not be white.

3. Dohyo (Sumo Ring)

3.1 Interior

The dohyo interior is the playing surface including the border line. Everything outside is the dohyo exterior.

3.2 Specifications

• Ring: circular, wood 12.5 mm thick, painted black, diameter 385 mm.
• Border line: white circular ring, width 12.5 mm.
• Platform height: 700–1000 mm.
• Dimensional tolerance: ±5%.
• Starting lines (Shikiri-Sen): 50 × 10 mm.

3.3 Exterior

A suitable safety area surrounds the ring (“ring area”); color and material are at organizer discretion.

3.4 Match format on the ring

• One match: best of 3 rounds within 3 minutes unless extended by judges.
• First to two Yuhkoh wins the match. If time expires and one team holds one Yuhkoh, that team wins.
• No winner in time → possible extended match (first Yuhkoh wins), judge’s decision, lots, or rematch.
• If robots get stuck, see 6.1.
• If a robot fails to start, one restart is allowed; if it fails again, the point is awarded to the opponent.
• If a hand-aimed repeater is used, no restart is granted for a failure to start; responsibility lies with the team.

3.5 Course of the Competition

Important: One person may be operator for a maximum of 2 robots for the entire contest.

• Robots are split into groups. Competition proceeds via groups → quarterfinals → semifinals → finals (groups best-of-3; finals may be best-of-5). Three referees (one principal, two assistants). Decisions are unanimous and final; arguing decisions may lead to disqualification.
• Same-team robots meeting in playoffs must play; no arranged advancement.
• Group order randomized after opening; schedule posted online and in team rooms. If too few teams for groups, a knockout bracket is used with random seeding.
• No breaks during a match. Between matches, repairs and reprogramming are allowed.
• Teams stay in assigned rooms and only move when called to the waiting area near the arena.
• Homologation is performed for robots about to start; they remain in the waiting area.
• Follow the schedule. Do not be late. If called and you do not arrive within 5 minutes, the robot is disqualified.
• One operator and one assistant allowed in the waiting/game area per team.
• Protective eyewear and gloves are mandatory in the game area and checked at homologation. Missing gear may yield a Yuhkoh to the opponent or disqualification.
• Up to 1 minute between rounds for cleaning and configuration (without touching once placed).
• Robots may not be touched once placed until the judge instructs after the fight.

3.6 Homologation (Technical Inspection)

At event start

• Verify competition number on the robot and photograph it clearly.
• Dimension check using a bottomless 53 × 53 × 53 mm frame (fits 50 mm cube with tolerance).
• Weighing: ≤ 100 g.
• Verify IR start/kill operation.

Before every match

• Dimension check with 53 × 53 × 53 mm frame.
• Weighing: ≤ 100 g.
• Verify visible number and protective gear.

After homologation, the first queued teams remain near the arena; others return to their room.

4. Start, Stop, Resume, End

4.1 Robot placing

• On judge instruction, operators place robots simultaneously and retreat to the safe area.
• All parts must be behind the Shikiri-Sen; no part may cross toward the opponent.
• Placement must be within the vertical projections of both starting lines. Incorrect placement → re-position.

4.2 Start

The judge starts each round with an IR start signal; robots start immediately (no delay). Start occurs only after the operator/assistant are in the safe area. Leaving the safe area without approval may cost a point or cause disqualification.

4.3 Stop / Resume

Only the judge stops/resumes the match and announces when to place, retreat, and collect robots.

4.4 End

The match ends when the judge declares so. Teams recover robots. After recovery, the decision is final; no objections accepted.

5. Time of Match

• Duration: up to 3 minutes per match.
• Extension: if called by the judge, up to 3 minutes.

6. Scoring

One Yuhkoh point shall be given when:

• A team legally forces the opposing robot to touch outside the ring.
• The opposing robot touches outside on its own.
• The opposing robot leaves the ring surface completely (even if the attacker later exits).
• The opposing robot is damaged and cannot continue (declared by its representative).
• If both exit together, the pushed robot loses the round.

Judges’ decision factors (if required)

• Technical merit in movement/operation.
• Penalty points incurred.
• Players’ attitude and fair play.

6.1 Stoppages & Rematches

• Non-start: one restart; if repeated, point to opponent.
• Entangled/orbiting ~10 s with no progress: one restart. If repeated, the robot that moves more and shows will to fight wins.
• Fast vs. slow robot stuck > 5 s: one restart. If repeated, the faster attacking robot wins the round.
• Two fast robots stuck > 5 s: one restart. If repeated, the more aggressive/faster robot wins.
• If a robot has 1 point and the next round has no winner, only 2 rematches are allowed. If still no winner, the robot with 1 point wins the match.
• No progress / simultaneous stop for 5 s without contact: the first to stop is deemed lacking will to fight → opponent gets a Yuhkoh. Judge may extend up to 30 s to assess progress.
• Both touch outside at about the same time and first contact cannot be determined: rematch.

6.2 Repairs & interruptions

• No repairs during a match.
• No battery change/charge during a match.
• No blade change during a match.
• No reprogramming during a match (pre-fight tactic selection is allowed).
• If the blade detaches, it may not be reattached during the match.
• A. The robot must start and finish the entire match without modification (except tactic selection) and may not leave the competition area.
• B. Max 1 minute between rounds to clean and configure.
• C. Battery/service/part replacement allowed only after the match and before the next match.
• D. If a robot breaks and cannot continue, the opponent wins; no repair allowed mid-match.

7. Violations

7.1 General

Any deeds described in Sections 2.2, 7.2, or 7.3 constitute a violation.

7.2 Insults

Insulting opponents or judges (spoken, audio from robot, or written on robot), or any insulting action, is a violation.

7.3 Protective Gear & Safe Area

• Operator/assistant not wearing mandatory gear during a match.
• Failure to retreat to the safe area or disobeying referee instructions.
• Missing/non-functional start/stop module → disqualification.

7.4 Minor Violations (warnings)

• Entering the ring during a match (except after a Yuhkoh and as instructed). Includes any body part or tools entering to support the body.
• Requesting to stop without valid reason.
• Taking > 60 s to resume without judge’s extension.
• Actions contrary to fair play.
• Leaving the waiting area without informing officials/referee.

Accumulating 2 warnings awards one Yuhkoh to the opponent or may result in disqualification depending on severity.

8. Penalties

• Violations under 2.2, 7.2, 7.3 → match loss; opponent receives two Yuhkoh; violator must leave the area.
• Minor violations under 7.4 accumulate; two warnings → one Yuhkoh to the opponent.
• Accumulation applies within a single match.

9. Objections

• No objections against judges’ decisions.
• Rule-application doubts may be raised by the operator to the Committee before the match ends. If no Committee is present, raise to the judge before match end.

10. Flexibility of Rules

As long as core concepts are observed, organizers may modify or abolish rules provided changes are published prior to the event and applied consistently.

11. Liability

• Teams are responsible for their own safety and that of their robots and are liable for any accidents they cause.
• The Relativity Robotics Challenge organization and staff are not responsible or liable for incidents/accidents caused by teams or their equipment.

Appendix 1 — Protective Gear

• Protective eyewear: lateral and frontal protection against minor mechanical shocks; translucent lenses; may be worn over regular glasses.
• Gloves: protection against mechanical shocks, flames, heat, humidity, cold, toxic waste.
• Not considered protective gear: sunglasses, latex medical gloves, regular textile gloves, ski gloves.

Appendix 2 — Team’s Folder

• Numbers for each robot
• Participation diplomas
• Badges for team members
• Info about team rooms and competition area map
• Promotional materials
• Explanation of group formation
• Maps for team rooms and the competition areas

Appendix 3 — Remote Start & Stop

Details about start modules: startmodule.com

Module overview

• Powered by 5V or 3.3V. Four pins: VCC, GND, Start, Kill.
• Kill pin may be monitored to cut motor power on stop (recommended for safety).
• Green LED indicates start/stop reception or error.
• On power-up the green LED must be OFF (ready). If ON, ask the referee to press Stop and power-cycle the robot.

Signal semantics

• Start pin: 0 on power-on; goes 1 on start; returns 0 on stop.
• Kill pin: 1 on power-on/start; goes 0 on stop (use to disable motor power path if implemented).

Pseudocode (template)

robot_ready = false
initial = digitalRead(START_PIN)
if initial == 1:
  # Error: should be 0 at power-on
  while True:
    pass  # lockout until power-cycle
else:
  robot_ready = True

# Wait for start
state = 0
while state == 0:
  state = digitalRead(START_PIN)

# Run until stop
if state == 1 and robot_ready:
  while digitalRead(START_PIN) == 1:
    # fight logic
    pass
  # On stop, halt safely and lock out
  while True:
    pass