On 27 January 2011 03:01, Jon Elson <el...@pico-systems.com> wrote:

> (For completeness, FF0 is feedforward proportional to position, not a
> really helpful
> term.)

It seems to me that FF0 would be ideal for a closed-loop spindle speed
control PID.
The FF0 term gives you the PWM duty cycle directly proportional to
speed request, and then you can have an I term to make it accurate.

P is no use at all in this case, as setting VFD duty to zero once at
speed really doesn't have the right effect :-)

-- 
atp
"Torque wrenches are for the obedience of fools and the guidance of wise men"

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