[Jared Russell]

We are just varying motor speed. Set the shooter up from different ranges, find a speed that works, and repeat until you have pretty good coverage of the field. Make that data into a table and set the motor to the power that corresponds with the given range (found by the camera or other means).

To compensate for battery variations, you will want to use a feedback loop to keep a constant velocity. We took a banner sensor and some reflective tape to make a primitive binary encoder. If the speed (ticks/sec) is too low, increase PWM value. If it's too high, decrease PWM value. The math is a little more complicated than that in actuality, but you get the idea (see the programming section; search for PID).

As a nice side effect of varying the power, the ball shooter recovers from the velocity drop after firing a ball more quickly (it detects that it has slowed down and gives the motor a higher PWM signal for a fraction of a second to compensate).

It is FAR simpler in hardware to build an adjustable speed shooter than an elevating one, even if the software is more complicated.