Quote:
Originally Posted by Cal578
If the wheels are coupled, such as a chain running around both, then they also must be at the same speed, so you only need one encoder total.
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If you're quite certain that you're only interested in shooting with a particular ratio (I would be, in your shoes), then I would advise coupling the wheels anyway... It may require a little extra work and about .5-2 pounds, but it would give you a mechanically defined ratio. I expect this could provide you some of the following benefits:
- Increased shot accuracy
- Need for only one encoder to precisely control shot speed/rotation
- Both motors are used to power both wheels (if one wheel takes more load, the second wheel and the two motors can all instantaneously apply energy to the more heavily loaded wheel)
- May allow you to "downgrade" one or both motors to Mini CIMS (which actually have a higher free speed, which many have touted as making them better for shooters, as it seems that higher torque (and certainly power) are less necessary for shooters)
- May allow you to remove one motor entirely
So, in my mind, the ideal solution is to chain/belt the two wheels together... seems that may actually improve your shooter, enable the PID tuning to be simpler, and to remove the need for the second encoder.
If of course you really can't add a mechanical coupling, the debate for 1 or 2 encoders is opened back up...
Really, it seems like the debate is there only because of a difference in goals... one side says 1 encoder is good enough, while the other says the improvement 2 brings is actually quite important! This all depends on your requirements... if you're aiming to be one of those "field-length snipers" I'm personally skeptical that 1 encoder is "good enough." If you're instead shooting from the front or side of the pyramid, it does seem like 2 would be overkill...