On 10 August 2010 05:42, Don Stanley <[email protected]> wrote:

> The Spindle gear selected is 230 RPM max, but the
> spindle-rpm-cmd goes past that and is continually
> trying to run the spindle faster and faster.

What is your HAL setup for spindle speed control?

If you are running closed-loop with a PID then I suspect you might be
seeing the PWM going full negative in an attempt to slow the spindle
below the max supported by the VFD. I have this problem as the VFD
direction buttons are controlled by spindle-fwd and spindle-rev and
ignore the direction output of the PWM. If you are over-speed with
very low PWM, then the PID will switch to negative outputs, which
actually gives an increasing PWM duty cycle, and eventually the PID
goes to negative max, which gives full PWM, full speed, and a vain,
ignored, PWM direction signal.

If this is your problem, then the solution is probably to use comp and
mux2 HAL functions to to connect the PWM input value to zero when the
PID output is negative. (I don't think you really want to reverse the
spindle VFD if  the spindle is running faster than requested)

[FEATURE REQUEST] A negative limit so that we can have unipolar PID
would be nice.

-- 
atp

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