When using the ball collection behavior, the robot considers a line from the target position to the ball's current or predicted position, depending on whether or not the ball is moving. The robot then plans a path to a point on the line and behind the ball such that it does not hit the ball on the way and such that it ends up facing the target position. Finally, the robot accelerates to the target. Figure 4(a) illustrates this behavior.
Figure 4: Single-agent behaviors to enable team collaboration
(a) Ball collection (aiming for a pass or to the goal); (b) Ball
interception (receiving a pass).
When using the ball interception behavior (Figure 4(b)), on the other hand, the robot considers a line from itself to the target position and determines where the ball's path will intersect this line. The robot then positions itself along this line so that it will be able to accelerate to the point of intersection at the same time that the ball arrives.
In practice, the robot chooses from between its two ball handling routines based on whether the ball will eventually cross its path at a point such that the robot could intercept it towards the goal. Thus, the robot gives precedence to the ball interception routine, only using ball collection when necessary. When using ball collection, it actually aims at the ball's predicted location a fixed time in the future so as to eventually position itself in a place from which it can intercept the ball towards the target.