RE: Freqmod problems

["Pete Cook" <pete.cook-at-alltracorp.com>]

Question - Does Freqmod use encoders for feedback?
If so what are the PID Parameters?

I work on these machines (still as plasma cutters) and am familiar with them
with servos attached. The biggest problem I have seen is that most of the
drive systems are too small and don't handle the bounce that is inherent in
that type machine. If you try to drive tha machine without gearboxes in the
drive train yopu are going to need a whole lot more torque from your motors.

Pete

>
> Erie
>
> Hey I wonder if the following error problem with freqmod is
> related to
> the notion that we have explored before that if you run at the max,
> during accel you pile a few pulses into the following error
> buffer that
> can't get put back into motion.  You might try setting
>
> [TRAJ]
> ..
> MAX_VELOCITY =          1.67
>
> a little larger than
>
> [AXIS_0]
> ..
> MAX_VELOCITY =                  1.2
>
> for each axis.
>
> You should also set
>
> DEFAULT_ACCELERATION =  20.0
> MAX_ACCELERATION =      20.0
>
> much lower than default.
>
> HTH
>
> Ray
>
>
>
> On Tuesday 12 February 2002 09:11 am, Shelbyville Design & Signworks
> wrote:
> > specifics:
> >
> > Gantry router, 8' x 12' work area
> > rack & pinion drive
> > 23 frame stepper approx 200 oz-in or so, running halfstep,
> geared 40:1
> > with a 24 d.p. 30T pinion
> > (step size is about .00025, way to small for routing, but
> this project
> > started out with a real small
> > budget (wife holds the purse strings and we all know how
> that goes) and
> > the reducers were already on the machine)
> > gantry weight is approx 600 lbs +-
> >
> > (if you've ever seen a Heath/Esab plasma cutter, it's the
> same machine)
> >
> > running the table on Turbocnc I can achieve 150 IPM easily,
> > but no contstant contour.
> >
> > I am going to be removing the gear reduction and going to gecko 201
> > drives, with a 550 oz-in
> > motor on the x axis, dirctly driving a 20T pinion, it will
> increase the
> > step size to approx .0015, this should
> > help with the speed, but the biggest problem is inconsistent step
> > pulses (scope confirms this)
> > with this much inertia, it doesn't take alot to throw things out of
> > whack.
> >
> >
> > erie patsellis
> >
> >
> >
> > Shelbyville Design & Signworks
> > 1309 W. S. 7th Street
> > Shelbyville, IL 62565
> > (217)774-4444
> > visit our website at http://216.43.233.169
> >
> > ----- Original Message -----
> > From: "Hugh Currin" <currinh-at-oit.edu>
> > To: "Multiple recipients of list" <emc-at-nist.gov>
> > Sent: Monday, February 11, 2002 6:23 PM
> > Subject: Re: Freqmod problems
> >
> > > Erie:
> > >
> > > What type of machine are you using?  i.e. size steppers
> and drivers.
> > > I'll
> >
> > bet
> >
> > > someone on the list has an *.ini file they'd be willing
> to send you
> > > as a starting point.
> > >
> > > I have freqmod working with 760 oz-in motors, Camtronic
> drivers half
> > > stepping, 2:1 reduction timing belts on a bridgeport kneemill size
> >
> > machine.
> >
> > > Does this come close? It isn't optimum but may be a
> starting point.
> > > :-)
> > >
> > > Hugh Currin
> > > Klamath Falls, OR
> > >
> > > On Monday 11 February 2002 04:03 pm, you wrote:
> > > > am I the only one who has unsuccessfully tried to use
> > > > freqmod with steppers? no amount (I've spent at least 8
> > > > hours on this so far) of pid tuning seems to eliminate following
> > > > errors. Steppermod.o for now.
> > > >
> > > >
> > > > erie patsellis
>