Servo Hum (Was: Two Q's...)

> If these motors are sitting loose on the bench you may just be

hearing

> some standing wave sort of rattle. This can happen with loose

motors

> that have very low inertial loads.

I think this might be the case. I tried backing off on the gain but
this didn't reduce the motor noise. In fact, reducing the dampening
actually had more of an effect on the noise. With reduced
dampening, I had to reduce the gain, almost to the lowest setting,
which is not really good since I could stop the motor with my
fingers and cause a fault condition with the gain so low.

Bascailly, the hum starts at a specific RPM (almost like a switch,
one second quiet, and the next humming). I could make the hum start
at a lower RPM by loading the motor with my fingers.

For reference, gain is set to just past 50% and the dampening set a
little further than that on my gecko.

Even with the noise, things work fine, but I'll know more once I
strap them to the mill (if it will ever get off backorder and get
here already).

For reference, can mistuning the servodrive result in a stituation
that will damage the motor or the servodrive itself?

As always, thanks again to everyone,
Jake

--- In CAD_CAM_EDM_DRO@y..., Ray Henry <rehenry@u...> wrote:
>
> Oops. Input and output scale are the number of pulses per unit
distance.
> They are not a measure of the gain of the axis. Axis gain (P) is
> disabled with steppermod so that will not help you a bit.
>
> With your slow pc steppermod is the one to use. If you set the
number of
> pulses per unit and max velocity to high, steppermod will cause
your pc
> to crash or be really erratic. Short of that you should be okay.
>
> If these motors are sitting loose on the bench you may just be
hearing
> some standing wave sort of rattle. This can happen with loose
motors
> that have very low inertial loads.
>
> HTH
>
> Ray
>
> BTW -- Freqmod does not use external feedback but it does use the
tuning
> parameters P -> FF2. Smdromod does use encoder feedback from the
> Kulaga/Mauch ISA board.
>
>
>
> On Friday 09 August 2002 10:00 am, you wrote:
> > Message: 9
> >    Date: Fri, 09 Aug 2002 10:31:59 -0000
> >    From: "jbordens" <jake@a...>
> > Subject: Re: Two Q's: Servo Hum and FreqMod issues
> >
> > Norm,
> >
> > Hmm, my output/input scale is already pretty high (20000).
> > StepperMod is working well for me, so I can stick to it. ;)
> > I just thought that FreqMod's behavor was a bit odd.  I suspect
its
> > looking for a closed loop which just isn't there, but as far as I
> > can tell, my settings are right.
> >
> > Mariss,
> >
> > I'll play with my gain a bit.  I guess when I tuned them my pulse
> > generator wasn't putting out enough pulses to really get the
motor
> > spinning fast enough to hum/rumble.  Now that I'm hooked to real
> > software, I get the hum.