10 C O M P L E X I T Y © 1998 John Wiley & Sons, Inc.

BY JOHN L. CASTI

RobosocFootball, robot style

© 1998 John Wiley & Sons, Inc., Vol. 4, No. 1CCC 1076-2787/98/01010-03

In January 1996, I was aimlessly milling about at a coffee break during the second annualArtificial Life & Robotics meeting in Beppu, Japan, when Jong-Hwan Kim, a researcherfrom South Korea, sidled up to me and began recounting his work on miniature robots.

Not being a roboticist myself, I listened with only mild curiosity until Kim mentioned thathe was trying to construct a team of robots that would play football (soccer, to the unculti-vated American ear and mind). All of a sudden my interest perked way up, as visions cameto mind of hoards of 3-inch-high robots swarming up and down a ping-pong-table-sizedplaying field. And, in fact, this is exactly what Kim had in mind—nothing short of an inter-national tournament analogous to the World Cup of football, but for robots rather thanRonaldos.

After hearing this visionary account of Kim’s electronic sporting ambitions, I replied sadlythat while I was fascinated by the idea of a coordinated collection of robots playing football,I wasn’t a robot builder myself and thus wouldn’t be able to participate in Kim’s tourna-ment. A pity, actually, as I found the whole idea of how to build both the hardware andsoftware to get a team of robots to play football an enormous challenge, one that I wouldhave been very interested to see worked out in the flesh, so to speak. To my great surprise,however, Kim immediately replied, “Well, it doesn’t matter that you don’t build robots. Youcan come and be the referee!” What a deal, I thought, and accepted this invitation on thespot before Kim could change his mind.

So it was that in November of that same year I gathered up my striped shirt and elec-tronic zapper to fry the brains of any cheating robot, and headed off to South Korea for thefirst Microrobot Soccer Tournament (MIROSOT).

THE MIROSOTThe MIROSOT, which involved 16 teams from 9 countries competing for the HanminjokCup, was held November 9–12, 1996, on the grounds of the Korean Advanced Institute ofScience and Technology (KAIST) in Taejon, South Korea. Each team consisted of three semi-autonomous robots. The rules of competition dictated that each competing robot’s me-chanics, vision system, and “brain” had to be packed into a cube no larger than 7.5 cm on aside. But unlike a real football field, the 130 cm x 90 cm rectangular playing field was boundedon all sides like an ice-hockey rink in order to prevent the “football,” an orange-painted golfball, from continually going out of bounds and interrupting play. TV cameras suspendedover the field continually gathered information about the location of all the players on thefield, the score, the amount of time remaining, and other facts about the state of play. Thisinformation was then broadcast to the competing robots by radio and was used by eachrobot to decide on its course of action at any moment. So the robots were semiautono-

John Casti received his Ph.D. inmathematics under Richard Bellmanat the University of SouthernCalifornia in 1970. He worked at theRAND Corporation in Santa Monica,California, and served on the facultiesof the University of Arizona, NYU,and Princeton before becoming one ofthe first members of the research staffat the International Institute forApplied Systems Analysis (IIASA) inVienna, Austria. In 1986 he left IIASAto take up his current post as aProfessor of Operations Research andSystem Theory at the TechnicalUniversity of Vienna. He is also aresident member of the Santa FeInstitute in Santa Fe, New Mexico,USA. In addition to numeroustechnical articles and a number ofresearch monographs, Professor Castiis the author of several volumes oftrade science, including ParadigmsLost, Searching for Certainty,Complexification, and Would-Be-Worlds.

C O M P L E X I T Y 11© 1998 John Wiley & Sons, Inc.

mous, in the sense that their behavior atany time was computed by themselves,using their robot-sized “brains.”

The MIROSOT was dreamt up by pro-fessors Jong-Hwan Kim and Ju-Jang Leeof KAIST, who thought a microrobot foot-ball game would play the same role instimulating the robot builder’s art thatplaying the game of chess serves as amotivator for the artificial intelligence(AI) community. It’s a problem combin-ing all the features needed to build real-istic robots—mechanics, sensors, intelli-gence—coupled with the spirit ofcompetition in a let’s-have-fun type ofsituation that everyone in the world caneasily understand and identify with. Thehope, of course, is that by discoveringhow to get a robot to move with agility,see with acuity, and think perceptively inthe limited context of a football game, itwill be possible to use the same tech-niques to build robots that solve other,more useful tasks. Here, of course, theanalogy with chess-playing and AI startsto break down, since in several decadesof trying, there’s not much evidence toindicate that the methods developed toget computers to play grandmaster-levelchess have any utility outside the specificdomain of the chessboard. But the robotbuilders at the MIROSOT were united inthe belief that their case is different, prob-ably because so many of the skills neededto play good robot football depend onhardware matters, such as mechanicalmotion and vision, rather than the purelyinformation-processing, software-basedissues that dominate computer chess-playing programs.

From a system-theoretic perspective,the interesting theoretical point of theoverall MIROSOT experiment is that foot-ball serves as a prototypical example ofwhat in the system theorist’s lexicon istermed a “complex, adaptive system.”These are systems composed of amedium-sized (a few hundred to a fewhundred thousand) number of individualagents that are both intelligent and adap-tive. This means that the agents take ac-tions based on rules and are adaptive inthat they are ready to change or inventnew rules to use if they see the old rulesaren’t working so well anymore. Further-more, in such systems no agent can see

everything; the agents must make theirchoices on the basis of only partial infor-mation about what anyone else in thesystem is doing.

PROBLEMS, PROBLEMS, PROBLEMS

T he MIROSOT gathering itself con-sisted of a scientific symposiumpiggy-backed on top of the actual

football tournament. In addition to ple-nary lectures on various aspects of the usesof computers and robots to simulate hu-man activities, the symposium was repletewith technical discussions of the variousapproaches employed by the competingteams to solve the problems arising in get-ting robots to play a decent game of soc-cer. These problems centered on threemajor areas: (1) mechanical problems in-volving how to get the robots to moveabout the field and to change directionsquickly in response to changing game con-ditions, (2) sensory problems concernedprimarily with seeing the ball and the otherplayers, and (3) strategic problems associ-ated with how the robot’s “brain” shouldprocess information so as to come up withsensible strategies and tactics to actuallywin a football game.

These problems make refereeing a ro-bot soccer game an experience in bothhumor and frustration. Often the robot’svision system gets confused by mislead-ing colors or swamped by information,leading to players pushing the ball intotheir own goal. At other times, goalkeep-ers stand as motionless as the Sphinxwhile the ball slowly rolls past them intothe cage. And if the referee were to reallyfollow the rules of either real or robotfootball, the number of offsides and pen-alties for “tripping” (i.e., running into theopponents) would be so great play wouldslow down to a glacial crawl. So a certainflexibility of interpretation of the rules isneeded just to keep things moving along.So, unlike computer chess, I don’t expectto see robot football players challengingtheir human masters anytime soon. Nev-ertheless, the skills shown by the teamsparticipating in this first MIROSOTshowed great potential for much morerefined play in the future.

The overriding problem faced by theteams entering the MIROSOT was not justhow to solve each of these problems sepa-

rately, but also how their suboptimal so-lutions should be used to optimally bal-ance each of these very different types ofquestions so as to encapsulate their so-lution to the problem of how to play foot-ball within a 3-inch cube. For example,the team from Newton Labs in Seattlechose to devote most of the space in theirrobots to the player’s mechanical motionand vision systems, implementing arather primitive playing strategy. As AnnWright, one of the developers of the New-ton Lab’s team noted in a TV interview,“We have a vision system that can updatethe player’s view of the game 60 times persecond. No other team in the tournamentcan do that.” Other teams, like the SOTYteam from KAIST, tried to compensate foran inferior visual system by implement-ing more elaborate playing strategiescoded into algorithms telling their play-ers how to plan their actions and react indifferent situations. As a result of thesebigger “brains,” however, such teams hadto compromise on the “physical” at-tributes of their players, such as speed ofmotion and visual acuity.

The one fundamental difficulty that allthe teams had to confront was the bar-rier one might term the “poverty ofpower” problem. To play the game, theplayers actually have to move from onephysical location to another. This im-poses a severe power consumption prob-lem on the designer, since the powerneeded to operate the robot’s mechanicsis considerable—especially since eachrobot has to carry its own power alongwith it in the form of a battery. So not onlydoes each robot have to have motors formotion, sensors for seeing, and a brainfor doing, it must also have batteries forpower. Current battery technology beingwhat it is, this power problem limited thelength of each half of the MIROSOTgames to five minutes.

So what kind of solutions to theseproblems separated the winners from thelosers in the MIROSOT? The answer is assimple as it is difficult to implement:Emphasize speed and vision at the ex-pense of brainpower. How appropriate!So here is one place where robot footballmakes contact with its real-world coun-terpart. It was clear from the very firstdemo game that opened the tournament

12 C O M P L E X I T Y © 1998 John Wiley & Sons, Inc.

that the team from Newton Labs wouldrun off with the championship trophy. Incontrast to most of the teams, whichtended to place relatively high emphasison strategic thinking as opposed to hard-ware, the boys and girls from Seattle allo-cated most of the space in their robots toa sophisticated motor control, coupledwith a superior vision system. By way ofcontrast, the strategy embodied in theNewton team’s robots was a very primi-tive one, consisting essentially of a high-level planner that plots a path for eachplayer, which is then implemented bylower-level controller that tells eachplayer what direction to move and atwhat speed. To give some indication ofhow superior the Newton team was totheir rivals, the scores of the four gamesthey played to win the championshipwere 13–0, 15–1, 19–0, and 20–0. By com-parison, the maximum number of goalsscored by any other team in the tourna-ment in any of the games was 8.

A TURING TEST FOR ROBOTS

So what can we say about the futureof robot football? Well, at present itappears to be in much the same situ-

ation that computer chess was in the1950s. In other words, laughable. But noone is laughing at the chess-playing pro-grams today, not even world championGarry Kasparov, who was beaten in a tour-nament with the reigning computerchampion, Deep Blue-II. Whether thissame scenario will unfold with computerfootball is debatable, as no one expects ro-

bots to ever take the field against their hu-man counterparts. But during a discussionat the MIROSOT, the idea was raised thatperhaps it would be interesting to intro-duce a new class of play, in which humanopponents controlled one of the compet-ing robot teams by using, for instance, ajoystick, Nintendo-style. This would thenintroduce a component of man-machinecompetition into the tournament, whichmany (including myself) feel would addspice to the tournament and serve to evenfurther motivate the robot builders. In anycase, everyone at the MIROSOT tourna-ment went home enthused about thewhole idea of robot football, vowing notto let the Newton Lab team get away withanother trophy at the next tournament.

In 1998, the competition was held inthe Cite de Science in Paris during thetime of the real World Cup. Robot foot-ball was an exhibit at the futuristic sci-ence museum this year.

As an amusing side note, at the veryend of the competitions (which lasted overa week) one of the directors of the Cité deScience said that the “spirit of Woodstock”had not been experienced there before.One of the features of the organization was24-hour access for the teams, which meantthere were enthusiastic young scientistsbeavering away around the clock duringthe tournament.

There were various categories in theMIROSOT (single-robot teams, three-per-side robot teams) of the 8-cm-cuberobots (that look like Rubik cubes onwheels). There was also the “Narasot” cat-

egory, which is really remarkable. In thiscategory are five-aside teams of amaz-ingly small, 4-cm-cube robots playingwith a ping-pong ball. The three-asidewinners came from Seoul University inSouth Korea, with the runners from thePolytechnic University of Sao Paulo inBrazil. The Korean robots really domi-nated the competition, being fast, verywell engineered, and very well controlled.However, a new feature emerged. Sincethe Korean robots were so fast and strong,they sometimes damaged the other ro-bots by crashing into them. So “charging”rules had to be enforced much morestrictly than had been the case in previ-ous tournaments. This represents a ma-jor new challenge, since the control nowmust have effective foul avoidance. Asbefore, however, the standards of play aregenerally quite primitive, often due topoor control. Most teams are clearly in-terested in the interaction of their intelli-gent agents. But there is not a lot of evi-dence of effective teamwork at themoment. In any case, robot football is anexcellent spur to get your robots workingtogether (assuming you can get themworking at all!).

Fortuitously, the next World Cup ofreal-world football is to be held jointly inSouth Korea and Japan in the year 2002.And I’m sure another MIROSOT will beheld then to coincide with the real WorldCup. Readers looking for more informa-tion about the MIROSOT may want toconsult its Web site, which is located atwww.mirosot.org.

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