[robocup-small] Regarding the dribbler

[Michael Babish]

>Change 1:
> 
> The dribbling distance will be set at 500mm for both active and passive
> dribblers.

It was my understanding that we wanted to limit the dribblers for two reasons:

1) We didn't want a single robot to be able to move the ball all the way down the field.
2) We didn't want to escalate the "dribbler war", where each team built stronger and stronger dribblers.

Please let me know if I am missing any other reasons.

The distance requirement certainly addresses the first problem, however it does not address the second problem.  Teams can still build incredibly powerful dribblers to keep possession of the ball when they really need it, and near the goal, 500mm can be enough for a single robot to outmaneuver the goalie.  I watched the Cornell highlights from 2002 (unfortunately, I can't find it online anywhere) and most of the goals were scored by a dribbling maneuver that was less than half-a-meter.

To be honest, I believe that this rule change *did* help to slow down the "dribbler war", but I don't think it solves the problem completely.  By 2002 (the last time I participated in the RoboCup competition) the dribblers were already enormously powerful.  Personally, I like the idea of limiting the robots to just horizontal dribblers.  I worked with the Cornell 2000 robots, which had only horizontal dribblers, and I think they had a nice balance between having some ball control, but not total ball control.

I agree with Jacky that dribblers are not necessary for receiving a pass - a passive shock absorber on the robot would accomplish the same thing.  However, the dribbler does offer many useful options:

1) The robot can slow down with the ball.  This is something real soccer players can do.  It is not possible without a dribbling mechanism.
2) The robot can steal the ball from an opponent robot.  Before dribblers, most robots would simply spin as fast as possible to strip the ball away from the opposing team.  This resulted in a loose ball (which, on the current field, would probably in play stoppage and a throw-in)
3) The robot can turn with the ball.  In fact, this is probably possible without a dribbler, but the dribbler makes it significantly easier.

Anyway, to summarize, I think the distance dribbling rule helps somewhat, but I think that disallowing the vertical dribblers would be a more elegant solution.

- Michael Babish
Cornell University
2000, 2001, 2002