Best approach for feeding frisbee to shooter mechanism?

[jnaranjo]

We are a rookie team.
We have a linear shooter with a vertical magazine behind it. We are mounting a rod to a windshield wiper motor (DC motor), and controlling it with a Talon. This will hit the bottom frisbee in the magazine out to the shooter.

We are looking for the best way to control the motion of the wiper.
The obvious issue is that we control the DC motor with a rate between -1 and 1.

We've come up with a few ideas, and we are looking for feedback on what might work the best, or even if some of these won't work at all.

1. Put an absolute encoder on the wiper motor shaft, and have it give us the angle that the wiper is at. We would calculate the final desired angle, which would be a constant. We could use the current angle from the encoder and the desired angle in a PID Subsystem to get the wiper where we want and back to it's original position.

2. Do the same thing as the first one, but use a potentiometer to get the angle we need instead of an absolute encoder.

3. We could calculate the time we need to run the motors for to get the desired angle. We would figure out the distance that we need to cover, and possibly use an incremental encoder to get the velocity of the wiper.

4. Use a limit switch to detect when the wiper has reached it's final destination. It may be difficult to position this in a way that doesn't interfere with the shooter, and we are worried about hitting the switch with the wiper too hard.

Those are all the ideas we've got so far, good and bad.
Any input is sorely needed, since we are short on time. Thanks in advance!