Sony robots cooperate in robotic soccer games

These robots play rough. It's not uncommon for them to lose a tail or an ear. Scampering around the field on all fours, the Sony AIBO robots used in RoboCup are usually happy to fight for control of the ball. They did exactly that in July at the 2002 RoboCup competition, the world's only robotic soccer competition.

The Carnegie Mellon team, named CMPack'02, won the world championship in RoboSoccer at the competition held in Fukuoka, Japan. The CMPack'02 robots, which compete in the Sony legged robot league, won all games that they played in. The final match was versus team rUNSWift of the University of New South Wales (UNSW) from Australia. Though the game was a 3-3 tie, the CMU team won 2-1 in the penalty kick tiebreaker.

The CMDragons'02, CMU's team that competes in the small-sized league, won three out of four games in the round-robin competition, but lost to Roobots - from Australia - in the finals.

The Sony legged competition is open to teams that use the four-legged Sony AIBO robots, which Sony sells for $1299 on its website. The competition featured some changes in rules and setup from the previous year. The field of play was expanded by a factor of 1.5. Due to the larger field, the teams were allowed to use an additional robot, bringing each team up to a total of four robots. However, the larger field did cause some complications. The robots were no longer able to see the ball when it was on the opposite side of the field because the length of the field exceeded the range of the camera mounted on each robot.

However, the CMU team compensated for this by taking advantage of wireless communication. The robots communicated with each other via wireless cards. Then, if one robot was on the opposite side of the field and could see the ball, it could tell all of the other robots. The rUNSWift team had not added inter-robot communication abilities to their robots and had greater difficulty finding the ball.

Communication between robots also allowed them to be more strategic in their play. They could be aware of other players on the field and cooperate, for example, by passing the ball to another robot.

"They weren't six year-olds playing anymore. They wouldn't all run to the ball; some would stay in supportive or defensive positions," said Manuela Veloso, CMPack'02's leader and a professor in the School of Computer Science.

The CMU robots do a victory dance when they score during a game, a fun routine added during the middle of the competition. The event in Japan attracted many spectators, including large groups of school children.

"I think we had a lot of kids cheering for us because they wanted to see the dogs dance," said Sonia Chernova, a senior in computer science who implemented the celebration dance.

RoboCup teams often share algorithms and ideas. Information on the algorithms is sometimes published online and teams make use of it to improve performance. This helps to drive progress and competition to produce the best RoboSoccer team.

For example, the CMU team adopted the walking technique that the UNSW team pioneered. The robots walk on their forearms rather than directly on their feet because they have greater stability on the forearms. They are much less likely to fall over, which can be a major setback in a competition.

Many of the RoboCup teams use CMVision, the vision system invented at CMU. Some teams also use the localization algorithm developed by Veloso's team. Localization allows the robots to determine where on the field they are and where they are in relation to the ball.

The robots have several kick maneuvers - they have a head butt, a chest butt, and a "kick" in which the robot falls flat on its stomach in order to propel the ball. Though these techniques certainly are different from traditional human soccer, they are quite effective in the realm of RoboSoccer. The splayed fall flat kick is used when the robots are far from the goal because it is the most powerful kick.

The AIBO robots use a learning algorithm for calibration of the vision system, but do not use any learning approaches during gameplay.

"I would like to see them learn that if their current strategy isn't making progress they should try something new," said Doug Vail, a computer science doctoral student on the CMPack'02 team. In the future, machine learning algorithms could enable the robots to perform better in different game environments.

The official goal statement of RoboCup is to "by the year 2050, develop a team of fully autonomous humanoid robots that can win against the human world soccer champion team."

It is difficult to imagine a team of robots playing soccer against a human team. How would robots ever move as quickly or with as much dexterity? What would happen if a steel robot kicked a human player in the shin?

Veloso thinks the appearance and design of robots are going to change significantly over the next 50 years. Robots will become more human-like and will fit in better with humans. They could have artificial skin and a humanoid form.

"Robots have been seen as things needed to go into dangerous environments for humans. I claim that we will have robots around just being companions," said Veloso.

People sometimes wonder what useful applications robotic soccer has, besides that of beating the world's champion human soccer team. RoboCup has led to improvements in real-time perception and robotic teamwork.

Real-time perception is essential in any area where robots need to be able to perceive the environment and make decisions in real time. This is useful for almost all robots that need to navigate and make decisions in real time about how to react to the environment.

Robotic teamwork is important for situations where robots can work together to accomplish a task more quickly or effectively. According to Veloso, RoboCup has stimulated the relatively recent surge of interest in robotic teamwork.

Everyone, from the military to universities, is interested in researching ways for robots to work together. For example, the US Navy is researching methods of multi-robot coordination so that teams of robots can be used to explore the ocean to do tasks such as search for mines or track enemy ships.

Veloso's team is organizing the first American RoboCup Open to be held here at CMU. It will be held in the University Center from April 30 to May 4, 2003. The competition will allow teams from the US, Canada, Mexico, and South America to compete as a practice for the world competition in July. Germany and other countries have been holding Open competitions for the past several years, but there has not yet been a similar competition in the US.

Next year's RoboCup competition will take place in Padova, Italy in the first week of July.