Soccer Rules

RoboCupJunior is a project-oriented educational initiative for students up to the age of 19. It is an exciting way to understand science and technology through hands-on experiences with electronics, hardware and software. RoboCupJunior also offers oportunities to learn about teamwork while sharing ideas with friends. The development of study materials and innovative teaching methods is among RoboCupJunior's aims.

The RoboCupJunior (RCJ) Soccer challenge is a competition for youngsters to design, program and strategize autonomous soccer-playing robots. Two different kinds of fields, named Soccer A and Soccer B, may be used at a tournament.

The Soccer A playing-field is 122 cm by 183 cm. Its corners are flattened, as shown in the schematic above.

The width of each goal is 45 cm, centered on each of the shorter sides of the playing-field. The goal is 14 cm high. It has a cross-bar on top (to prevent robots from entering the goal). The interior of the goal, including floor, walls and cross-bar, is painted yellow or blue (one goal yellow, the other blue). The exterior is painted black.

The Soccer B playing-field is 122 cm by 183 cm. Around the field is an out-area of 30 cm width. Total dimensions of the field, including the out-area, are 182 cm by 243 cm. The field is marked by a white line between 10 mm and 20 mm width. The line is part of the field.

The width of each goal is 60 cm, centered on each of the shorter sides of the playing-field. The goal is 10 cm high. It has a cross-bar on top (to prevent robots from entering the goal). The interior of the goal, including floor, walls and cross-bar, is painted yellow or blue (one goal yellow, the other blue). The exterior is painted black.

The floor of the playing-field consists of green carpet on top of a hard surface. Walls are placed all around the field, including behind the goals and, if applicable, the out-area. The height of the walls is 14 cm. They are painted matte black.

There are five neutral spots defined in the field. One is in the center of the field. The other four are adjacent to each corner, located 45 cm along the long edge of the field, aligned with each goal post towards the middle of the field (from the goal post). The spots are marked black.

A 60 cm diameter center circle is drawn on the field. It is a thin black marker line. It is there for referees and captains as a guidance during kick-off.

Soccer A: In front of each goal there is a 30 cm wide and 75 cm long penalty area.

Soccer B: In front of each goal there is a 30 cm wide and 90 cm long penalty area.

The penalty areas are marked by a white line between 10 mm and 20 mm width. The line is part of the area. A robot is inside the penalty area when it is completely inside.

The fields should be placed in such a way that the influence of external infrared light is as low as possible and the Earth's magnetic field is disturbed as little is possible. Perfect conditions cannot be guaranteed, however. Teams must come to tournaments prepared to calibrate their robots based on the lighting and magnetic conditions at the venue.

Robots

Each team is allowed to have at most two robots. The substitution of robots within a team or with other teams is forbidden. Robots are not allowed to be coloured yellow or blue, in order to avoid confusion with the goal colours. Yellow or blue parts used in the construction of the robot must either be occluded by other parts from the perception by other robots or be taped/painted with a neutral colour. The robot must not emit infrared light. However, infrared distance sensors may be used as long as they do not affect other robots. Infrared light reflecting materials must not be used on the outside. If robots are painted, they must be painted matte. Minor parts are irrelevant as long as robots are not affected. The (supposedly) affected team has the burden of proof that it is affected.

The use of remote control of any kind is not allowed. Robots must be started manually by humans and be controlled autonomously. Robots are not allowed to use any kind of communication during game play unless the communication between two robots is via Bluetooth class 2 or class 3 (range approximately 20 metres). Teams are responsible for their communication. The availability of frequencies cannot be guaranteed.

Robots must be constructed and programmed in a way that their movement is not limited to one dimension (i.e. one axis). They must be able to move in all directions, e.g. by turning. Robots must respond to the ball in a direct forward movement. For example, it is not enough to basically just move left and right in front of its own goal; it must also move directly toward the ball in a forward movement. Robots must be constructed and programmed in such a way that they do not enter the goal. Robots are allowed to make use of the cross-bar.

All robots must have a stable handle to hold and to lift them. The handle must be easily accessible, for example on top of the robot. The handle must not be used for mounting components of the robot.

Robots will be measured in an upright position with all parts extended. A robot's dimensions must not exceed the following limits:

Size (diameter): Ø 22.0 cm

Height: 22.0 cm (the handle of the robot may exceed this height)

Weight: Open League - 2.4 kg; Light Weight League - 1.1 kg (the weight of the robot includes its handle)

Ball-capturing zone: 3.0 cm

Voltage: Open League - 15.0 V; Light Weight League - 12.0 V

Taking into account the way the power packs of a robot are connected (parallel or series), the total nominal voltage of all power packs and all connected power packs used by a robot cannot exceed 15.0 V for Open League and 12.0V for Light Weight League. Voltage pumps are not permitted. Each robot must be equipped with accessible terminals to verify the voltage of each power pack, unless the nominal voltage is obvious by looking at the robot, its power packs and connections.

The ball-capturing zone is defined as any internal space created when a straight edge is placed on the protruding points of a robot. This means that the ball must not enter the concave hull of a robot by more than 3 cm. Furthermore, it must be possible for another robot to take possession of the ball.

Robots must be constructed exclusively by student members of the team. Mentors, teachers, parents or companies may not be involved in the design, construction and assembly of robots. For the construction of the robots, any robot kit or building block may be used as long as the design and construction are primarily and substantially the original work of the team. This means that commercial kits may be used but must be substantially modified by the team. It is neither allowed to mainly follow a construction manual, nor to just change insignificant parts. Indications of violations are the use of commercial kits that can basically only be assembled in one way, or the fact that robots from different teams, built from the same commercial kit, all look basically the same.

Robots must be constructed in such a way that they can be started by the captain without the help of another person. Robots must be programmed exclusively by student members of the team. Mentors, teachers, parents or companies must not be involved in the programming and debugging of robots. For the programming of the robots, any programming language, interface or integrated development environment (IDE) may be used. The use of programs that come included with a commercial kit (especially sample programs or presets) or substantial parts of such programs are not allowed. It is not allowed to use sample programs - even if they have been modified.

Proof must be supplied by each team that their robots match these regulations, e.g. detailed documentation or log book. Teams may be interviewed about their robots and the development process, at any time during a tournament. During an interview, at least one member from each team must be able to explain particulars of the team's robots, especially regarding its construction and programming. An interviewer may ask the team for a demonstration. The interviewer may also ask the team to write a simple program during the interview, to verify that the team is able to program its robot.

Robots that do not match the above regulations are not allowed to play. If violations are detected during a running game, the team is disqualified from that game. If similar violations occur repeatedly, the team can be disqualified from the tournament.

Game Play

Each game will consist of two halves. The duration of each half is 10 minutes. There will be a 5-minute break between the halves. The game clock will run for the duration of the halves without stopping (except when the referee wants to consult an official). The game clock will be run by the referee or an assistant. Teams should be at the table 5 minutes before their game starts. Teams can be penalized one goal per minute, at the referee's discretion, if they are late for the game start. If a team does not report within 5 minutes of the game start, it forfeits that game and the winning team is awarded a 5-0 win.

Each team must have a captain. The captain is the person responsible for communication with the referee. The team can replace its captain during the competition. The captain is not allowed to wear any yellow or blue clothes that can be seen by the robots (to avoid interference with the goal colour.) The referee can require the team captain to change clothes or to be replaced by another team member if interference with goal colour is suspected.

At the start of the first half of the game, the referee will toss a coin. The team mentioned first in the draw shall call the coin. The winner of the toss can choose either to kick off first, or which end to kick to. The loser of the toss will decide the other option. After the first half, teams will switch sides. The team not kicking off in the first half of the game will kick off to begin the second half of the game.

Each half of the game begins with a kick-off. All robots must be located on their own side of the field. All robots must be halted. The ball is positioned by the referee in the centre of the field. The team kicking off places their robots on the field first. Robots cannot be placed nor remain behind the goal line or in the out area. Robots cannot be moved once they have been placed. The team not kicking off will now place their robots on the defensive end of the field. All robots on the team not kicking off must be at least 30 cm away from the ball (that means outside the centre circle). The referee may adjust the placement of the robots. On the referee's command (usually by whistle), all robots will be started immediately by each captain. Any robots that are started early will be removed by the referee from the field and treated as damaged robots.

Except for the kick-off, human interference (e.g. touching the robots) during the game is not allowed unless explicitly permitted by the referee. Violators can be disqualified from the game.

A robot cannot hold a ball. Holding a ball means taking full control of the ball by removing all of its degrees of freedom. Examples for ball holding include fixing a ball to the robot's body, surrounding a ball using the robot's body to prevent access by others, encircling the ball or somehow trapping the ball with any part of the robot's body. If a ball stops rolling while a robot is moving or a ball does not rebound when rolled into a robot, it is a good indication that the ball is trapped. The only exception to holding is the use of a rotating drum that imparts dynamic back spin on the ball to keep the ball on its surface. Such a device is called a dribbler. Other players must be able to access the ball.

A goal is scored when the whole of the ball is inside the goal or if it strikes the back wall of the goal. The robot moving first into the penalty area completely (with every part if it) on a team's defending side is designated as goalie until a part of it leaves the penalty area. Within the penalty area, the goalie has priority. Attacking robots are not supposed to push the goalie in any way. If the attacker and the goalie touch each other and at least one of them has physical contact with the ball, the ball will be moved to the nearest unoccupied neutral spot immediately. If a goal is scored as a result of this pushed-situation, it will be disallowed.

Lack of progress occurs if there is no progress in the gameplay for a reasonable period of time and the situation is unlikely to change. Typical lack of progress situations are when the ball is stuck between robots or between the robot and the wall, or no robot is able to detect the ball at its location. The referee will call 'lack of progress' and will move the ball to the nearest unoccupied neutral spot. If this does not solve the lack of progress, the referee can move the ball to different neutral spots.

In Soccer B, the ball is considered as out if it is entirely outside the playing area. If a ball is out, the referee will reposition the ball on a neutral spot. The captain of the team whose robots did not touch the ball last can choose between the two neutral spots on the half of the field where the ball went out. If one of these neutral spots is occupied by a robot, the captain can choose to reposition the ball to the centre of the field. The decision of the captain must be made immediately by pointing to a neutral spot. If the captain does not decide immediately, the referee will choose a neutral spot instead.

If a robot is damaged, it has to be taken off the field and must be fixed before it can play again. A damaged robot must remain off the field for at least one minute. A robot is damaged especially when:

it does not respond to the ball
it continually moves into the goal
it turns over on its own accord
it is stuck to a wall or a corner and cannot free itself

After a robot has been fixed, it will be placed on the unoccupied neutral spot nearest to where it was taken off, and not directly aiming towards the ball. A robot can only be returned to the field if the damage has been repaired. Only the referee decides whether a robot is damaged. A robot can only be taken off or returned with the referee's permission.

If both robots from the same team are deemed damaged during game play, the clock continues and the remaining team gets one initial goal and rests while waiting for the opponent's return to play. The remaining team will also get one additional goal for each minute the opponent's robots remain damaged. After five minutes of absence, the team with no functional robots forfeits the game. However, these rules only apply when neither of the two robots was damaged as a consequence of a breach of the rules by the other team.

Multiple defense occurs if more than one robot from the defending team enters its penalty area and substantially affects the game. The robot farther from the ball will be moved to the centre neutral spot. If multiple defence happens repeatedly, the robot will be deemed damaged.

In principle, a game will not be stopped. The referee can stop the game if there is a situation on or around the field which the referee wants to discuss with an official of the tournament, or if the ball malfunctions and a replacement is not readily available. When the referee has stopped the game, all robots must be stopped and remain on the field untouched. The referee may decide whether the game will be continued/resumed from the situation in which the game was stopped or by a kick-off.

It is expected that the aim of all teams is to play a fair and clean game of robot soccer. It is expected that all robots will be built with consideration to other participants. Robots are not allowed to cause deliberate interference with or damage to other robots during normal game play. Robots are not allowed to cause damage to the field or the ball during normal game play. Humans are not allowed to cause deliberate interference with robots or damage to the field or the ball.

All participants are expected to behave themselves. All movement and behaviour are to be of a subdued nature within the tournament venue. Mentors (teachers, parents, chaperones and other adult team-members) are not allowed in the student work area unless it is explicitly but temporarily permitted by a member of the organizing committee. Only participating students are allowed to be inside the work area. Mentors must not touch, build, repair or program any robots. The substitution of robots during the competition within the team or with other teams is forbidden.

An understanding that has been a part of world RoboCup and RoboCupJunior competitions is that technological and curricular developments should be shared with other participants during and after the competition.

It is expected that all participants - students, mentors and parents alike - will respect the RoboCupJunior mission. It is not whether you win or lose, but how much you learn that counts!

Teams who violate the code of conduct can be disqualified from the tournament. It is also possible to disqualify and exclude from further participation in the tournament only a single person or a single robot. In less severe cases of violations of the code of conduct, a team will be given a warning by showing it a yellow card. In severe or repeated cases of violations of the code of conduct a team can be disqualified immediately without a warning by showing it the red card.

All decisions during the game are made by the referee or the referee assistant, who are in charge of the table, the field, and the persons and objects surrounding it. During game play, the referee's decisions are final. Any argument with a referee or the assistant can result in a warning. If the argument continues or another argument occurs, this may result in immediate disqualification from the game. At the conclusion of the game, the referee will ask the captains to sign the score sheet. By signing the score sheet, the captains accept the final score on behalf of the entire team.

Rule clarification may be made by members of the RoboCupJunior Soccer Technical Committee, if necessary even during a tournament. If special circumstances (such as unforeseen problems or capabilities of a robot) occur, rules may be modified by members of the RoboCupJunior Soccer Technical Committee, if necessary even during a tournament. Each RoboCupJunior competition may have its own regulatory statutes to define the procedure of the tournament (for example the superteam system, game modes, the inspection of robots, interviews, schedules, etc.). Regulatory statutes become a part of this rule.

Pulsed IR Soccer Ball

Answering to the request for a soccer ball for RCJ tournaments that would be less sensitive to interfering lights, less energy consuming and mechanically more robust, the RCJ Soccer Technical Committee defined the following technical specifications with the special collaboration of EK Japan and HiTechnic. Balls complying with this specification have now completely replaced the old unmodulated IR balls used until recently (2010). Producers of these balls must apply for a certification process upon which they can exhibit the RCJ-compliant label and their balls used in RCJ tournaments. Balls with these specifications can be detected using a specific sensor from HiTechnic (IRSeeker V2 - information on distance and direction) but also common IR remote control receivers (TSOP1140, TSOP1240, GP1UX511QS, ... - on-off detection with a possible gross indication of distance).

IR light: The ball emits infra-red (IR) light of wavelengths in the range 920 - 960 nm, pulsed at a square-wave carrier frequency of 40 kHz. The ball should have enough ultra bright, wide angle LEDs to minimize unevenness of the IR output.

Diameter: The diameter of the ball shall be in the range 74 - 80 mm. A well-balanced ball shall be used.

Drop test: The ball must be able to resist normal game play. As an indication of its durability, it should be able to survive, undamaged, a free-fall from 1.5 metres onto a hardwood table or floor.

Modulation: The 40 kHz carrier output of the ball shall be modulated with a trapezoidal (stepped) waveform of frequency 1.2 kHz. Each 833-microsecond cycle of the modulation waveform shall comprise 8 carrier pulses at full intensity, followed (in turn) by 4 carrier pulses at 1/4 of full intensity, four pulses at 1/16 of full intensity and four pulses at 1/64 of full intensity, followed by a space (i.e. zero intensity) of about 346 microseconds. The peak current level in the LEDs shall be within the range 45 - 55 mA. The radiant intensity shall be more than 20mW/sr per LED.

Battery life: If the ball has an embedded rechargeable battery, when new and fully charged it should last for more than 3 hours of continuous use before the brightness of the LEDs drops to 90% of the initial value. If the ball uses replaceable batteries, a set of new high-quality alkaline batteries should last for more than 8 hours of continuous use before the brightness of the LEDs drops to 90% of the initial value.

Coloration: The ball shall be neutral in colour. In particular, it must not have any green, blue or yellow coloration (to avoid confusion with the colours of the field and goals).