The Middle Size League is an official league of RoboCup. Two (soccer) teams made up of five autonomous robots, with dimensions up to 80 cm in height, 52 cm in diameter and 40 kg in weight, play on a field similar to a football field, but smaller in size (18 m x 12 m).
Robots have numerous sensors (cameras, gyros, sonar, etc.) and actuators (motors, kickers device, etc.), which enable them to play completely autonomously, without any human intervention. They also have wireless connection in order to communicate among themselves and with the referee.
As a rule, there are two referees: one regulates the game and the other interacts with a graphical interface. This interface makes robots aware of all fouls, cards, etc., that occur during the game.
This particular league attracts great public attention due to its multidisciplinary aspect. Developing a team of robots of this size poses mechanical and electronic challenges. On the other hand, autonomy restriction sets its own challenges in signal processing, control and artificial intelligence. The competitive scenario is regularly reviewed to ensure the challenge is adequate to the state of technology.