CAD CAM EDM DRO - Yahoo Group Archive

Re: Microstepping thru the Tulips

on 2006-08-13 18:44:08 UTC
It is normal for drivers running a stepper motor
above the corner frequency to never reach the
specified coil current before the next step comes
along. The result is that a micro-stepping drive
will seem to act more like a full step drive at
higher speeds. This is normal and is above the
dreaded resonance ranges. When the step rate
drops to somewhere that resonance and micro-steps
matter, the relationship between the PWM or chop
rate and the step frequency once again allows
real micro-stepping currents to be established.

Regards,
Steve Stallings



--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Phil Mattison"
<mattison20@...> wrote:
>
> Perhaps, but a 100KHz microstep rate and a 20KHz PWM frequency
implies that
> the coil current is modified five times in a single cycle of the
PWM, which
> is absurd. In that case, the PWM (or chopper, whatever) cannot
produce the
> power modulation that is supposed to be the big deal with
microstepping. Any
> microstep rate above the PWM frequency renders it meaningless. What
you end
> up with in practice is a single-step driver.
> --
> Phil Mattison
> http://www.ohmikron.com/
>
> ----- Original Message -----
> From: Mariss Freimanis <mariss92705@...>
> To: <CAD_CAM_EDM_DRO@yahoogroups.com>
> Sent: Sunday, August 13, 2006 12:48 PM
> Subject: [CAD_CAM_EDM_DRO] Re: Microstepping thru the Tulips
>
>
> > I have thought a little about the relationships you mentioned over
> > the years.:-) I'll just cover the step frequency vs. PWM frequency
> > thing:
> >
> > I think you misunderstand PWM works. Microstepping frequency and
PWM
> > frequency are completely unrelated. This thought experiment may
help
> > to straighten it out:
> >
> > I think you agree that 400 Hz step rate on a full-step drive
results
> > in a 100Hz current waveform frequency. The full-step sequence
repeats
> > after 4 full steps after all. This modulates OK on a 20kHz PWM
for a
> > motor speed of 120RPM.
> >
> > A 250-microstep drive needs a 100kHz step pulse frequency to get a
> > speed of 120RPM. The current waveform frequency is still the same
and
> > it still modulates OK.
> >
> > 100kHz is way above the PWM frequency but the PWM never sees it.
It
> > only sees the resulting 100Hz reference, the same as for the full-
> > step drive. This also modulates OK on a 20kHz PWM.
> >
> > Mariss
> >
> >
> >
> > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Phil Mattison"
> > <mattison20@> wrote:
> > >
> > > I've seen a lot of comments about microstepping on this board
as if
> > it is
> > > the best thing since sliced bread. I wonder how many people have
> > thought
> > > about the relationships between step rate, PWM frequency and
motor
> > > inductance. Since microstepping supposedly uses the PWM chopper
to
> > regulate
> > > current into something like a sine wave to improve motor
> > performance, it
> > > stands to reason that if the step rate gets anywhere near the
PWM
> > frequency
> > > that theory goes out the window. Also, the motor coil inductance
> > puts an
> > > upper bound on the step rate at which the PWM does anything at
all.
> > Exactly
> > > what those limits are depends on the combination of motor
> > inductance, power
> > > supply voltage, chopper switching speeds and probably several
other
> > factors
> > > with less impact. So to say that more microstepping is better
than
> > less is
> > > like saying that blue is better than orange.
> > > --
> > > Phil Mattison
> > > http://www.ohmikron.com/
> > >
> >
> >
> >
> >
> >
> >
> >
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> >
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Discussion Thread

Phil Mattison 2006-08-13 11:35:32 UTC Microstepping thru the Tulips Mariss Freimanis 2006-08-13 12:50:54 UTC Re: Microstepping thru the Tulips turbulatordude 2006-08-13 13:57:07 UTC Re: Microstepping thru the Tulips Mariss Freimanis 2006-08-13 15:18:28 UTC Re: Microstepping thru the Tulips Wayne C. Gramlich 2006-08-13 18:08:18 UTC Re: Microstepping thru the Tulips Phil Mattison 2006-08-13 18:21:29 UTC Re: [CAD_CAM_EDM_DRO] Re: Microstepping thru the Tulips Steve Stallings 2006-08-13 18:44:08 UTC Re: Microstepping thru the Tulips Mariss Freimanis 2006-08-13 19:18:36 UTC Re: Microstepping thru the Tulips Jon Elson 2006-08-13 22:17:06 UTC Re: [CAD_CAM_EDM_DRO] Re: Microstepping thru the Tulips John Dammeyer 2006-08-13 23:54:31 UTC RE: [CAD_CAM_EDM_DRO] Re: Microstepping thru the Tulips lcdpublishing 2006-08-14 04:44:35 UTC Re: Microstepping thru the Tulips Graham Stabler 2006-08-14 05:04:52 UTC Re: Microstepping thru the Tulips Phil Mattison 2006-08-14 08:36:25 UTC Re: [CAD_CAM_EDM_DRO] Re: Microstepping thru the Tulips Steve Stallings 2006-08-14 09:18:00 UTC Re: Microstepping thru the Tulips turbulatordude 2006-08-14 09:33:08 UTC Re: Microstepping thru the Tulips Mariss Freimanis 2006-08-14 17:39:57 UTC Re: Microstepping thru the Tulips Dennis Schmitz 2006-08-14 19:41:24 UTC Re: [CAD_CAM_EDM_DRO] Re: Microstepping thru the Tulips turbulatordude 2006-08-14 19:48:01 UTC Re: Microstepping thru the Tulips Mariss Freimanis 2006-08-14 20:21:07 UTC Re: Microstepping thru the Tulips Henrik Olsson 2006-08-15 02:58:01 UTC Re: [CAD_CAM_EDM_DRO] Re: Microstepping thru the Tulips turbulatordude 2006-08-15 07:23:23 UTC Re: Microstepping thru the Tulips Phil Mattison 2006-08-15 08:27:33 UTC Re: [CAD_CAM_EDM_DRO] Re: Microstepping thru the Tulips lcdpublishing 2006-08-15 08:55:36 UTC Re: Microstepping thru the Tulips Les Newell 2006-08-15 09:26:27 UTC Re: [CAD_CAM_EDM_DRO] Re: Microstepping thru the Tulips Les Newell 2006-08-15 09:32:56 UTC Re: [CAD_CAM_EDM_DRO] Re: Microstepping thru the Tulips Mariss Freimanis 2006-08-15 10:16:27 UTC Re: Microstepping thru the Tulips Graham Stabler 2006-08-15 12:13:26 UTC Re: Microstepping thru the Tulips Mariss Freimanis 2006-08-15 13:37:34 UTC Re: Microstepping thru the Tulips Graham Stabler 2006-08-15 16:03:35 UTC Re: Microstepping thru the Tulips Paul Kelly 2006-08-15 17:43:39 UTC RE: [CAD_CAM_EDM_DRO] Re: Microstepping thru the Tulips Mariss Freimanis 2006-08-15 20:00:13 UTC Re: Microstepping thru the Tulips Graham Stabler 2006-08-16 02:18:22 UTC Re: Microstepping thru the Tulips Les Newell 2006-08-16 02:26:25 UTC Re: [CAD_CAM_EDM_DRO] Re: Microstepping thru the Tulips turbulatordude 2006-08-16 08:53:07 UTC Re: Microstepping thru the Tulips Les Newell 2006-08-16 09:22:23 UTC Re: [CAD_CAM_EDM_DRO] Re: Microstepping thru the Tulips