real tests needed was Re: true closed loop vs. hobby closed loop

Jon,

The POSITION ERROR test point on the G320 is the difference between
commanded position and actual position. This shows very easily on a
scope as a 40mV per motion increment error. You can literally count
the position error "steps" on the scope trace.

Again, what is the policy regarding the "Files" and "Photos" section
of this group? The "upload" function no longer exists. I'm asking
because I would have liked to upload some scope pics pertaining to
this thread.

Mariss

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@p...> wrote:
>
>
> ballendo wrote:
>
> >Mariss,
> >
> >I'm glad you've posted this. Now to get some REAL info we need
this
> >same test done with a MACHINE attached. Nothing like some added
mass
> >to affect the numbers...
> >
> >Because I'm pretty sure everyone here is accelerating more than
just
> >the motor rotor...
> >
> >Ballendo
> >
> >P.S. Even better would be to add your scope to a drive that's
> >installed in a BP retrofit, or a large gantry table, and then run
the
> >drive through some typical toolpaths. Repeat also on smaller
> >machines. THEN we'd really know how things stood up for
comparison.
> >Which would be a good thing, IMO. As you say, nothing like
actually
> >measuring something. (IN its intended use...)
> >
> >We could perhaps get Jon E to do the same with his servo amps, and
> >then this whole issue would move from the theoretical to the
> >practical... (Perhaps someone with rutex's too?)
> >
> >
> I have an old one posted on my web pages, see
> http://jelinux.pico-systems.com/servo.html
>
> You can't compare the actual vs. commanded position because the
actual
> trace covers the commanded. But, obviously, the servo drive is
closely
> following the trajectory it is supposed to take. This was done at
90 IPM.
> This WAS taken from an underpowered servo drive on a Bridgeport
> milling machine.
>
> Jon