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Originally Posted by TimCraig
Be advised that the response of the Victor speed controllers is HIGHLY nonlinear with respect to the PWM input values. From my tests, it's essentially exponential, that is, linear when plotted on semilog paper. The actual curve is dependent on robot weight, wheel friction, drive train friction, etc, so your mileage may vary. On our robot we get about 90% of speed at 44% of PWM range. I've attached a picture of the measured data.
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The following thread goes into a lot about why the graph looks like that.
http://www.chiefdelphi.com/forums/sh...tor+non-linear
The following graph shows the response of the speed controller when connected to a purely resistive load (and is linked towards the end of the above thread).
http://www.saratogarobotics.com/php-...showpage&pid=1. The response of the Victor speed controllers is linear in the range that IFI designed it for:
http://ifirobotics.com/forum/viewtopic.php?t=317. The problem is that you are driving a non-linear system.