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:
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
>Ray,Actually, this is not true for half step, or at least, the half step
>
>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.
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....