Re: Servo tunning?

It is a Servo lite system build by Mr. Bill.

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@p...> wrote:
>
>
> Torsten wrote:
>
> >I am just about done with my mill/drill conversion when I mounted
> >up the pulley for the ametec servo motors 600 oz/in I did some
> >test runs checking the strenght of the motors by holding on to
> >the pulleys by hand when rottating slowly.
> >I am very impressed with the tourqe on those motors I was not able
> >to hold them by hand.
> >When the motor is holding steady I was able to turn them about
> >2-3 degree ether way before the tourqe gets up to full power.
> >Logic would dictate that there has to be some movement but I would
> >like to try to get this down some.
> >
> Are you using Gecko 320 or 340 drivers? I have observed this, too,
> on a client's machine, but in his case, the motors deliver little
torque
> until they are moved 5 or more degrees!
>
> >The motor is using 250 quadrature encoders is this part of what
> >determends how much deflection one would have to put up with?
> >
> I assume that is a 250 cycle/rev encoder, giving 1000 quadrature
counts
> per rev? (250 counts/rev would be 62.5 cycles/rev, which can't
exist, so
> the first must be right.)
>
> >There are 2 adjustment options on the driver board gain and torque
> >limit, my question is will this be the right action to take and
> >is there a procedure on how to do it?
> >
> You want the gain as high as you can get it without causing
oscillation.
> There ought to be a loop compensation adjustment (or damping). You
> want the gain (basically a low-frequency open-loop gain setting) as
> high as possible to keep the constant error as small as possible.
> The loop compensation reduces high-frequency gain to keep the
> servo loop from trying to get movement faster than the mechanical
> inertia can respond.
>
> >What amount of deflection would be normal for a well tuned system?
> >Since this has about the same effect as backlash I wonder how much
> >of it I will be left with?
> >Do stepper motor have a advantage here it seams like they would not
> >experience this problem?
> >
> >
> I can say that my true servo system (encoder -> PC, PC -> DAC ->
servo amp)
> will hold within 2-3 encoder counts until you exceed the current
limit of
> the amp. So, that is .00005" x 3 = 0.00015". The Gecko drives are
supposed
> to work the same way, but I have seen results that indicate it may
not in
> some installations. We may still have problems in that setup that
cause
> this. The high resistance of the Ametek motors combined with low
> power supply voltage may also be to blame.
>
> Jon