System Overview

We used the same omnidirectional robots as in the global vision FU-Fighters team [4], but with a vision system mounted on top the robots. It consists of a small camera directed upwards, looking into a concave mirror that produces an omnidirectional view of the environment. Unlike most teams that use convex mirrors we took a concave mirror from a cheap flashlight.
Each robot is connected to an external computer via a wireless analog video link. The computer grabs the images and analyzes the video stream to extract information about the status of the game. The extracted local views are transmitted through a LAN to a fusion module that merges them to a global view. The reactive behavior control system now can either use a global view or a local view, as appropriate. For example, if a robot cannot detect the ball, but other robots can, the first can use the calculated global ball position. We adapted the global vision behavior to the special needs of local vision. For instance, if a robot cannot find the ball, then it searches the playing field looking for the ball. Here localization is an important issue. The scanning is coordinated among the robots, ensuring that the search is well distributed over the playing field. If a robot can detect the ball and the opponent goal, then the robot does not care about localization but focuses on relative movements. It tries to move behind the ball, and to direct the kicking mechanism towards the opponent goal.