Quote:
Originally Posted by Alex.q
This makes sense to me, but I couldn't explain to a mentor why you wouldn't want to run the motor at its free speed. Why wouldn't it be consistent at its free speed? Is it just because there isn't much torque at that speed, so the motor might slow down more when it shoots a frisbee?
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If you run it open-loop at full voltage, three things happen:
1) The actual speed you get varies greatly as the battery voltage changes
2) It takes a long time for the motor to spin up to free speed
3) When the motor slows down due to a frisbee passing through, the motor doesn't have much torque at that high speed and so it takes longer to recover
Gearing your shooter wheel motor so that you can get the desired wheel speed when the motor is running at less than free speed*, and using some sort of closed-loop control of speed, solves all three of the above problems. A bang-bang controller is very easy to implement and works well for this application.
* ideally at 50%