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|These two robots Striker and Sweeper were built as a two-robot team to compete in a "Robotic Volleyball" competition which was held in Sheffield England, as part of the British Association for Science Annual exhibition,
on the 13th of September 1999. Although it was called volleyball the court was 2.4m x 2.4m divided into 2 halves and the "net" was a 6mm high ridge between the halves. Each team could have two robots that could communicate using the Lego RCX IR transmit/receive capabilities. (The full rules can be read in the technical report).
The two robots that I built I named striker and sweeper. The sweeper had two roles, one to sweep the ball from the center of the pitch to the edges of the court and also to defend the line against attacks. The strikers role was to collect the ball from the edges of the court and kick it over the line. The first attempts at building robots were to use the IR sensors that came with the Lego Mindstorms and also use the fact that the court had a black to white colour gradient to navigate around the court. However the sensors were not accurate enough to localize the robot and got lost very fast. Therefore the final two robots used the physical court to navigate, i.e. the striker used the Lego micro-switches to keep itself following the court outside wall and the sweeper used mechanics to keep itself tight against the 6mm ridge "net".
To enable the sweeper to reach all of the court a tail mechanism flipped out from behind the robot which was dragged along the court sweeping the ball to the edges. The tail had to flip out only after the matches started as there was an initial foot-print size of 40cmX40cm allowed per robot stated in the rules.
The sweepers role of defending was carried out using non-Mindstorms sonar sensors to detect any movement in the opponents court and track the object along the front line.
The two robots also communicated during the match.