CAD CAM EDM DRO - Yahoo Group Archive

Re: [CAD_CAM_EDM_DRO] Re: stepper vs. servo

Posted by Harvey White
on 2004-02-12 11:44:40 UTC
On Thu, 12 Feb 2004 09:52:06 -0000, you wrote:

>Ray,
>
>A bit more:
>
>A stepper is just a syncronous motor run using square waves (At the
>fullstep resolution). In other words, the square waves are as close
>as you can get to a sine wave using only on and off.
>
>When you go to 1/2 step, you add another level of current control,
>and the input waveform gets another step, and is a little closer to
>the sine wave ideal. As you go up in microsteps, you keep refining
>the input waveforms by adding steps/levels towards ideal sine waves.

Actually, this is not true for half step, or at least, the half step
that I know.

The trick in half step is to have two adjacent pole pieces actuated,
so that the balance point for the rotor is half way between. The
waveforms are still square waves, they just overlap in time.

You can do quarter stepping by providing four points, full 1,
intermediate A, full 1 and full 2, intermediate B, and full 2. This
sequence will repeat. The amount of overlap, time wise, or if the
waveform is continually chopped, the duty cycle of the waveform, will
give intermediate A and B the relative strengths of pole 1 and pole 2
needed to position the step halfway between full 1 and (full 1 and
full 2).

While you can run the motor with stepped square waves, I'm not sure
that there is an advantage, since the drivers will dissipate the least
current when saturating, and the scheme above has the drivers
saturating. It seems to me that a stepped square wave, while
possible, would be a more complicated driver.

Harvey


>
>At some point, you're back running a synchronous motor with sine
>waves...
>
>Ballendo
>
>P.S. Our typical steppers will run just fine at 72 rpms, using a
>capacitor on one coil, and fed by 60 cycle ac. (infinite
>microsteps<G>)
>
>--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Raymond Heckert" <jnr@a...>
>wrote:
>> Has anybody ever designed a micro-stepping driver that outputs
>> approximations of sine/cos to two adjacent coils. I understand
>that you
>> develop max torque at any rpm, up to the max (which is higher than
>the
>> square-wave input). Is this true? How much would it take to
>develop,
>> assuming no one already has? BTW does anybody know anything about
>Don
>> Lancaster's (tenaja.com) Magic Sine Waves, and if they can be
>applied to
>> this application.
>>
>> RayHex
>>
>> ----------
>> > From: Jon Elson <elson@p...>
>> >
>> > Given the Gecko 320 as the driver for the servos, I think there
>are a
>> > couple of significant advantages over steppers. First, the
>servos are
>> > usually capable of a greater speed range, while steppers rapidly
>lose
>> > torque at higher speeds. With servos, you rarely have to worry
>about
>> > resonance issues. You don't say whether you will use belts, rack
>and
>> pinion
>> > or leadscrews to drive this machine, but the servo will likely
>provide
>> > smoother motion, and be less perturbed by some backlash in the
>mechanics.
>> > Steppers can go wild when rack and pinion drive is used, and
>rattle the
>> > gears
>> > something awful. Finally, if you lose a step with a stepper
>drive, you
>> > won't know it until you measure the finished part. With the
>gecko 320,
>> > it won't allow small errors to build up, and will fault if the
>drive
>> binds
>> > up or crashes. This can be sensed by the computer and cause it
>to stop
>> > all axes.
>> >
>> > Jon
>
>
>
>
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Discussion Thread

plastiguy 2004-02-09 18:41:27 UTC stepper vs. servo bull2003winkle 2004-02-09 19:49:34 UTC Re: stepper vs. servo Jon Elson 2004-02-09 21:24:17 UTC Re: [CAD_CAM_EDM_DRO] stepper vs. servo ballendo 2004-02-09 21:59:06 UTC Re: stepper vs. servo Albee Tang 2004-02-09 21:59:07 UTC Re: [CAD_CAM_EDM_DRO] Re: stepper vs. servo Roy J. Tellason 2004-02-09 22:35:39 UTC Re: [CAD_CAM_EDM_DRO] Re: stepper vs. servo Les Newell 2004-02-10 00:55:07 UTC Re: [CAD_CAM_EDM_DRO] Re: stepper vs. servo John Johnson 2004-02-10 05:22:09 UTC Re: [CAD_CAM_EDM_DRO] stepper vs. servo Peter Renolds 2004-02-10 06:01:12 UTC Re: [CAD_CAM_EDM_DRO] Re: stepper vs. servo - H Bridge question Jon Elson 2004-02-10 07:47:46 UTC Re: [CAD_CAM_EDM_DRO] Re: stepper vs. servo Stan Aarhus 2004-02-10 07:49:36 UTC Re: [CAD_CAM_EDM_DRO] stepper vs. servo ballendo 2004-02-10 07:50:14 UTC DIY servo drive? was Re: stepper vs. servo Jon Elson 2004-02-10 08:02:47 UTC Re: [CAD_CAM_EDM_DRO] Re: stepper vs. servo bank haam 2004-02-10 09:47:15 UTC Re: [CAD_CAM_EDM_DRO] DIY servo drive? was Re: stepper vs. servo Mariss Freimanis 2004-02-10 11:36:49 UTC DIY servo drive? was Re: stepper vs. servo dchristal2 2004-02-10 13:32:47 UTC Re: stepper vs. servo ballendo 2004-02-10 16:59:46 UTC Re: stepper vs. servo ballendo 2004-02-10 17:02:13 UTC Re: stepper vs. servo ballendo 2004-02-10 17:03:03 UTC Re: stepper vs. servo Roy J. Tellason 2004-02-10 17:51:24 UTC Re: [CAD_CAM_EDM_DRO] Re: stepper vs. servo Jon Elson 2004-02-10 21:23:22 UTC Re: [CAD_CAM_EDM_DRO] Re: stepper vs. servo Roy J. Tellason 2004-02-10 21:42:58 UTC Re: [CAD_CAM_EDM_DRO] Re: stepper vs. servo Tony Jeffree 2004-02-11 02:17:12 UTC Re: [CAD_CAM_EDM_DRO] Re: stepper vs. servo Les Newell 2004-02-11 02:31:50 UTC Re: [CAD_CAM_EDM_DRO] Re: stepper vs. servo Les Newell 2004-02-11 02:43:21 UTC Re: [CAD_CAM_EDM_DRO] Re: stepper vs. servo Raymond Heckert 2004-02-11 19:23:21 UTC Re: [CAD_CAM_EDM_DRO] stepper vs. servo Robert Campbell 2004-02-11 19:40:12 UTC Re: [CAD_CAM_EDM_DRO] stepper vs. servo bull2003winkle 2004-02-11 20:35:58 UTC Re: stepper vs. servo Jon Elson 2004-02-11 20:51:18 UTC Re: [CAD_CAM_EDM_DRO] stepper vs. servo Jon Elson 2004-02-11 21:02:29 UTC Re: [CAD_CAM_EDM_DRO] Re: stepper vs. servo ballendo 2004-02-12 09:03:44 UTC Re: stepper vs. servo ballendo 2004-02-12 09:04:03 UTC microstepping was Re: stepper vs. servo Harvey White 2004-02-12 11:44:40 UTC Re: [CAD_CAM_EDM_DRO] Re: stepper vs. servo Chris Cain 2004-02-12 16:44:15 UTC RE: [CAD_CAM_EDM_DRO] microstepping was Re: stepper vs. servo JanRwl@A... 2004-02-12 20:42:04 UTC Re: [CAD_CAM_EDM_DRO] microstepping was Re: stepper vs. servo ballendo 2004-02-13 06:36:22 UTC Re: stepper vs. servo turbulatordude 2004-02-13 07:26:28 UTC Re: stepper vs. servo ballendo 2004-02-13 07:51:51 UTC microstepping was Re: stepper vs. servo Harvey White 2004-02-13 08:34:30 UTC Re: [CAD_CAM_EDM_DRO] Re: stepper vs. servo Mariss Freimanis 2004-02-13 10:11:40 UTC Re: stepper vs. servo Jon Elson 2004-02-13 10:15:17 UTC Re: [CAD_CAM_EDM_DRO] Re: stepper vs. servo Mariss Freimanis 2004-02-13 10:59:38 UTC Re: stepper vs. servo Jon Elson 2004-02-13 18:46:24 UTC Re: [CAD_CAM_EDM_DRO] Re: stepper vs. servo ballendo 2004-02-14 07:46:52 UTC Re: stepper vs. servo ballendo 2004-02-14 07:46:53 UTC Re: stepper vs. servo Harvey White 2004-02-14 08:43:17 UTC Re: [CAD_CAM_EDM_DRO] Re: stepper vs. servo Mariss Freimanis 2004-02-14 12:31:32 UTC Re: stepper vs. servo ballendo 2004-02-15 11:45:06 UTC Chopper methodology was Re: stepper vs. servo ballendo 2004-02-15 11:45:07 UTC Stepper Mid band resonance Help! please... jeffalanp 2004-02-15 12:22:14 UTC Re: Stepper Mid band resonance Help! please... Mariss Freimanis 2004-02-15 13:02:29 UTC Chopper methodology was Re: stepper vs. servo Mariss Freimanis 2004-02-15 13:22:53 UTC Re: Stepper Mid band resonance Help! please... zephyrus@r... 2004-02-15 16:33:25 UTC Re: Chopper methodology was Re: stepper vs. servo Mariss Freimanis 2004-02-15 17:05:54 UTC Chopper methodology was Re: stepper vs. servo turbulatordude 2004-02-15 22:20:30 UTC Re: stepper vs. servo - hundreds of microsteps turbulatordude 2004-02-15 22:40:08 UTC Re: stepper vs. servo - Allegro and ignoring the edges.... Jon Elson 2004-02-16 09:39:54 UTC Re: [CAD_CAM_EDM_DRO] Re: stepper vs. servo - hundreds of microsteps Mariss Freimanis 2004-02-16 10:48:05 UTC Re: stepper vs. servo - Allegro and ignoring the edges.... ballendo 2004-02-16 10:52:22 UTC Chopper methodology was Re: stepper vs. servo jmkasunich 2004-02-16 14:07:51 UTC Re: Stepper Mid band resonance Help! please... Mariss Freimanis 2004-02-16 14:22:28 UTC Re: Stepper Mid band resonance Help! please... jmkasunich 2004-02-16 14:38:26 UTC Re: stepper vs. servo - Allegro and ignoring the edges.... jmkasunich 2004-02-16 14:41:11 UTC Re: Stepper Mid band resonance Help! please... ballendo 2004-02-16 15:25:25 UTC Re: Stepper Mid band resonance Help! please... Jon Elson 2004-02-16 22:01:46 UTC Re: [CAD_CAM_EDM_DRO] Re: stepper vs. servo - Allegro and ignoring the edges.... Mariss Freimanis 2004-02-17 07:14:02 UTC Re: stepper vs. servo - Allegro and ignoring the edges.... turbulatordude 2004-02-17 08:09:24 UTC Re: stepper vs. servo - Allegro and ignoring the edges.... Mariss Freimanis 2004-02-17 09:27:33 UTC Re: stepper vs. servo - Allegro and ignoring the edges.... Jon Elson 2004-02-17 19:28:16 UTC Re: [CAD_CAM_EDM_DRO] Re: stepper vs. servo - Allegro and ignoring the edges....