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The goalkeeper robot has both special hardware and special software.
Thus, it does not switch positions or active modes like the others.
The goalkeeper's physical frame is distinct from that of the other
robots in that it is as long as allowed under the RoboCup-97 rules
(18cm) so as to block as much of the goal as possible. The
goalkeeper's role is to prevent the ball from entering the goal. It
stays parallel to and close to the goal, aiming always to be directly
even with the ball's lateral coordinate on the field.
Ideally, simply staying even with the ball would guarantee that the
ball would never get past the goalkeeper. However, since the robots
cannot accelerate as fast as the ball can, it would be possible to
defeat such a behavior. Therefore, the goalkeeper continually
monitors the ball's trajectory. In some cases it moves to the ball's
predicted destination point ahead of time. The decision of when to
move to the predicted ball position is both crucial and difficult, as
illustrated in Figure 8. Our goalkeeper robot currently
take into account the predicted velocity and direction of the ball to
select its moves.
Figure 8: Goalkeeping.
Sun Dec 7 06:55:46 EST 1997