2702 discussed at great length building a dedicated goalie bot, but eventually decided against it due to the seductive attraction of scoring.
Since we're not going to use these ideas, maybe someone else could:
-Deploy upward-facing ultrasonic sensors 20" on right side of the robot
-Have either multiple upward-facing deployable blockers at left side of robot (near wall), or one mobile blocker (on a track of some sort), with deployable blockers 20" outwards from the front and back of the bot.
-If the ultrasonics detect a ball passing overhead, deploy the appropriate blocker cylinder
-Design robot to be extremely long, to maximize the real estate for installing blocker cylinders.
We figured a robot optimized for goalie duty could very effectively block about 7ft of goal area. If using ultrasonics or some other mechanism to detect incoming balls, it could block those 7ft during auton, and then the driver could probably be extremely effective in teleop blocking the single incoming opponent ball.
Ideas we had that would be dependent on rule interpretation:
-Deploy the blockers timed such that they imparted a hard upwards punch to approaching balls, potentially tossing them out of the arena (we decided this was likely illegal. Even if deemed to be non-POSSESSION, there's another rule that bans repeated removal of an opponent's ball). This meant that if automatic, the blockers would have to be deployed extremely quickly after the ultrasonics detected the ball in order for the blocker to be there in time.
-Have a skirt of carpet-contacters. The goalie rule simply says that the robot must remain in contact with the carpet of the goalie zone. A large number of 20" things that hung from the robot and contacted the carpet in the goalie zone would mean the robot could also partially play defense on the low goals.
Some quick sketches:
http://jdraw.it/draw/225eaa - diagram of the carpet contacters - view is from the top
http://jdraw.it/draw/d29eb5 - view of the blockers from the front - dotted are undeployed blockers. Imagine this robot has wheels as well.