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

Thanks Mariss,

I do have a faster machine available, and I'll give that a go and
report back here to let you know. Thanks again. You're the best.

To nonrelated questions, if I may:

#1 - Is the err/res pin tristated? The docs don't say specifically
but I'd like to hook the err/res pin up to a tristate pin on a PIC.
I'm looking to monitor/set the err/res pin from a small PIC thats
part of my Estop circuit.

And #2 - I asked this in an earlier post, but I'll ask again. What
is the 6 pin header near the test points for? Do you guys have a
test harness that hooks there?

The reason I ask is that I'd really like to somehow be able to hook
up to the test points through that small hole there in the case.
I'm wondering if I could biuld some sort of connector through the
hole in the case that would connect to the test points (or maybe to
the 6-pin header?) ;)

thanks again guys. And thanks Mariss. I'll try a faster PC. ;)

Jake

--- In CAD_CAM_EDM_DRO@y..., "mariss92705" <mariss92705@y...> wrote:
> Hi,
>
> A badly tuned servo can break out into oscillation and rapidly
> overheat the motor. Just short of that, it may "hum" for a second
or
> so after any direction or load change.
>
> I don't think that is what's happening here though. This could be
the
> result of poorly spaced step pulses. The motor faithfully tries to
> follow them; the resultant acceleration / deceleration causes the
hum
> you hear. The tipoff is the abrupt change from no hum to hum at a
> certain speed.
>
> I don't know your CPU speed. If it is slow, you may wish to try it
> again with a faster PC if you have one.
>
> Mariss
>
> --- In CAD_CAM_EDM_DRO@y..., "jbordens" <jake@a...> wrote:
> > > 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.