They Came, They Scanned and They Conquered

Robot soccer may seem frivolous, but it's not. It's actually a severe test of the limits of programming skills.
by Eric Mankin

ROBOT SOCCER players programmed by computer scientists at the School of Engineering's Information Sciences Institute (ISI) journeyed to Nagoya, Japan, in August for the first-ever "RoboCup" - and returned with one first place and one third-place prize, making world headlines as they did so.

ISI's "DreamTeam" - five toy trucks transformed into Pentium-powered soccer 'bots by an enthusiastic group of young programmers and engineers led by research professor Wei-Min Shen - tied for first place in the mid-sized division, and might have won outright with better batteries.

And in the simulation division, a test of pure programming that pitted virtual soccer teams against each other in a video game-like environment, "ISI Synthetic," or ISIS, captured third place in an extremely competitive field. ISIS was the work of another team of young ISI talent - including some DreamTeam members - led by artificial intelligence expert Milind Tambe.

"ISI has long been in the forefront of technology development," said Dean of Engineering Leonard M. Silverman. "Their success in RoboCup demonstrates that they are truly on the cutting edge of intelligent systems research."

ISI DIRECTOR Herbert Schorr noted that the USC teams defeated more experienced and better financed opponents.

"These victories were achieved by a few very talented researchers and students working on their own time with a shoestring budget," he said. "Their victories show that USC has the intellectual ability and creativity to compete successfully with the very best anywhere."

Robot soccer may seem whimsical, but it is actually a severe test of the limits of programming. Particularly since the striking success of the Nagoya event, robot soccer is likely to gain increasing recognition as a "standard problem" - a universal test that lets workers in many labs measure themselves against each other.

AS THE GROUP OF scientists who first proposed the problem noted in a 1995 initiative paper: "In order for a robot to actually perform in a soccer game, various technologies must be incorporated, including design principles of autonomous agents, multi-agent collaboration, strategy acquisition, real-time reasoning, robotics and sensor fusion. ... It is a task for a team of multiple, fast-moving robots under a dynamic environment."

To which Shen's team - consisting of Jafar Adibi, Rogelio Adobbati, Bongham Cho, Ali Erdem, Hadi Moradi, Behnam Salemi and Sheila Tejada - and their competition from the U.S., Japan, and Australia would add: Robot soccer is a task performed in an environment in which anything that can go wrong, will go wrong.

ISI played a leading role in planning RoboCup. The notion was first proposed in 1995, but took its final form in February at an international conference on intelligent agents held in Marina del Rey under the auspices of ISI. Here, the ground rules for the Aug. 24-28 event in Nagoya were discussed and finalized.

FIELDING THE ROBOT team was a substantial investment for ISI. The time the group spent on the robots was sandwiched in between more conventional academic and research pursuits. The robots each incorporated a $600 Pentium motherboard mounted on the $70 toy trucks, and the team itself had to travel to Japan to compete.

But Shen and many of the same team members had recently pulled off a robotics David vs. Goliath, placing second in a prestigious robot competition in Oregon with a clunky but superbly programmed robot named "Yoda" (see USC Chronicle, Sept. 9, 1996), "so ISI had some confidence in us," Shen said.

Teamwork helped. A majority of the team members are regular participants in a weekly soccer game in a park near ISI. They knew and trusted each other.

And Shen created a team organization that made full use of the talents of each member. While every person in the group specialized in an area - design, programming, interfaces, and so on - Shen also assigned custody of each robot to one person who was responsible for keeping it in perfect working order.

"The experience of actually having the robot, of taking it home with us sometimes, of traveling with it, was very important," said team member Salemi.

Salemi was responsible for designing the interface that connected the robot's brain to its "eyes" - a simple, low-resolution, low-speed, small-field-of-view Quick Cam camera - and its "legs," the two pairs of wheels, each driven by its own electric motor.

The trucks, manufactured by Nikko and found by chance at a local electronics outlet, proved perfect for the task: they were quick, powerful, stable and highly maneuverable. The control mechanism was simple, and easy for the computer to plug into.

The ISI DreamTeam was later stunned to learn that a competitor from Japan's Osaka University had independently used the same toy truck as the basis for its robot soccer players - though they had controlled and programmed it differently.

THE DREAMTEAM approach was unique. The robots - named Homer, Marge, Bart, Lisa and Maggie after The Simpsons cartoon characters - were autonomous, with all decisions being made on board each robot. This contrasted with, for example, the Osaka team, which had computers controlling the robots on the sidelines. The Osaka computers received visual input from the on-board camera via one radio frequency, and sent control signals to the robot via another - and suffered from continuing communication problems.

The autonomous concept was proved in one key area: "Our team was the only one that could dribble the ball," said Adobbati, who besides taking custody of "Homer" (whom the Argentine-born soccer enthusiast privately renamed "Diego"), did the programming for the two robots who specialized in defense.

The ISI teammates arrived in Japan with high hopes, but were frozen in horror when they saw their first opponents, from Uttori University in Japan.

The ultramodern metal shapes embodied the latest in robot propulsion technique. And they were massive: weighing more than 100 pounds, each robot took two handlers to bring it onto the floor.

"We thought, we are finished, we have no chance," recalled Adobatti.

But the Uttori robots, which won a special prize for design excellence, turned out to be fatally slow. The DreamTeam's Simpsons easily dribbled around them and won by a commanding 4-0 score, the most goals scored in a match. From that point on, the problems proved solvable - adjusting to lighting conditions different from those in practice, and learning to squeeze the most power possible out of the batteries.

BATTERIES PROVED the weakest link in the DreamTeam design. The crucial final match went into overtime - and when it ended, only two of the robots were still moving. The survivors prevented a score by Osaka, but first place had to be shared.

What surprised the ISI members was the degree of outside interest. The games were mobbed with spectators, "and many times, there were more reporters than players," Adobatti said. Team members were interviewed by representatives from American, French, English, German, Chinese and Japanese media. Shen was astonished to get a phone call from his parents, who live in China and had read about his exploits in their newspaper. (For a detailed account of the press coverage of RoboCup '97, see "USC in the News," USC Chronicle, Sept. 15).

USC HAS EVEN GAINED a competing robot soccer team by transfer. Graduate student Barry Werger arrived this fall from Brandeis University, following his major professor, Maya Mataric, who joined the computer science department this year. Werger's team won no medals in Nagoya but did defeat co-champions Osaka University 1-0 in an

unofficial match. Werger used off-the-shelf components "and concentrated on software," proudly noting that his defense was perfect. He plans to take an improved team to Paris for RoboCup '98.

The mid-sized robot league, in which the DreamTeam and Werger's robots competed, attracted the most media attention, but was not the only game in town. The simulation league, in which programs compete in a video game-like virtual environment, has long been a hotbed of activity in robot soccer, not the least because no hardware or robots are involved - programs can compete at long distance.

RoboCup '97 attracted 40 simulation league entries from all over the world. The USC ISIS entry, consisting of Tambe, Adibi (also on the DreamTeam), Yaser Alonaizon, Ali Erdem, Gal Kaminka, Ion Muslea, Marcelo Tallis and Stacy Marsella, proved extremely competitive.

While ISIS initially won a series of matches by lopsided scores, its later wins were marked by exciting, close games. Team member Kaminka, who traveled to Nagoya, said, "In less than a minute of game time, our agents went from a 1-0 loss to a 2-1 incredible win."

One of the keys to the success of ISIS was the teamwork on the field driven by software called STEAM, developed by Tambe for combat simulations in military training. The competition let ISI test STEAM's generality and reusability, and will lead to further refinement in the teamwork theory underlying the software.

The overall development of ISIS was based on the SOAR artificial intelligence architecture developed at ISI for uses including computer instruction and strategic war-gaming against human opponents.

ISIS' simulation soccer program was the best from the U.S., beating a team from Carnegie-Mellon for third place. It lost only one match, to a Japanese program. "We have to analyze the game and see why our defense broke down in this game," Tambe said after the match.

Tambe is looking forward to a U.S. simulation league championship to be held in 1998, followed by RoboCup '98 in Paris next summer. RoboCup '98, which will coincide with the World Cup soccer tournament, is expected to benefit from the accompanying media frenzy.

ISI has some work to do beforehand. "We believe we have demonstrated that our basic concept of autonomous robots works," Shen said. The team will be giving robots better eyes to scan the field without having to pivot, better programming, and, above all, a more reliable power supply.

But USC will be at the games. "I'm taking French this semester," Adobatti said.


DreamTeam members, from left, Behnam Salemi, Sheila Tejada, Wei-Min Shen, Rogelio Adobbati and Hadi Moradi show off the winning soccer robots.

Each soccer robot has its own onboard computer, connected to an "eye" - a simple, low-resolution, low-speed, small-field-of-view Quick Cam camera - and two pairs of wheels, each driven by its own electric motor. The toy trucks used as a base proved well-adapted to the task: they were quick, powerful, and highly maneuverable.