Quote:
Originally Posted by Qbranch
How much resolution do the PWM outputs have? What frequency do they output at?
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Well if FIRST is planning on using the IFI Victors and doesn't find an alternative speed controller, we know the maximum effective resolution achievable on the Victors is 97 counts on either side 0. This despite the IFI RC's actual resolution of 127 counts on either side of 0.
Now, the 9403 has an update rate of 7us. Given that we have to vary our pulse by 1ms for a "full" range of control, that gives us about 143 counts of resolution over the full range. As opposed to the 255 counts on the IFI RC. (Presuming the IFI pulse work out to exactly 255 for 1-2ms variation) When you add in the Victor's deadband and only 97 output steps, you end up with an effective resolution of 54 output steps with the cRIO/9403/Victor combination.
I realize that we're not doing rocketry control systems here, for the most part anyways, but effectively halving our output resolution annoys me, as one or two counts can definitely affect how straight your robot's driving. Especially considering this is the Control System of Tomorrow and the motor control system now seems to be less capable than the Control System of Yesterday. I think following in NASCAR's Car of Tomorrow footsteps is taking the Overdrive theme just a bit too far.