AMC DC Servo drive adjustments explained

Called AMC and as always, talked to a great guy.
Just wanted to post this summary so as to make it available to anyone
looking for same.
Pot 1, Loop Gain, is the one responsible for responsiveness of the motor to error in commanded parameter (speed in my case, as I run in velocity mode). To adjust it, turn it clockwise until the motor starts vibrating when commanded zero. Then back out 1-2 turns. Gunner pretty much said the same thing.
Pot 3, Reference Gain, has nothing to do with stability of the servo system and represents only the proportion of how much speed you get for a given volts input. Fully clockwise it means 100% available speed.
I will make some adjustments tonight based on that, so as to get a stable system operating at top performance. During tuning, I turned down Ref gain, for no good reason as it turns out. So my motors do not operate at top speed avaliable from the drive.
i
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wrote:

It sure is refreshing when the support people actually provide some support.
This is all very good news - that the adjustments appear so easy to accomplish. Not that I'm not interested in Karl & Tim's more scientific approach - I've designed a few controllers over the years and this is STILL interesting stuff, but it's nice to see that Gunner's more nuts & bolts method will get you close enough*. But what do the other pots do (there are five, if I remember correctly)?
* Wouldn't it be great if Gunner could just stick to what he knows?
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On 07/23/2010 12:47 PM, Ignoramus7608 wrote:

Ha! That's what I figured.

Well....
It has nothing to do with the stability of the _drive_, but it affects the overall gain of the position servo. When you change the setting on that pot it'll change the gain that EMC 'sees'. Turning up the gain on that pot has the same effect as turning up all the gains in EMC.
So, set it such that the voltage range of the drive, without topping out in speed, matches the voltage range that EMC will send. Then don't ever touch it -- putting inspection paint on it to seal it would not be a bad idea, or even a drop of beeswax.

--

Tim Wescott
Wescott Design Services
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wrote:

Thats not really necessary..and he WILL need to retune it in about 2 yrs after the electronics have aged a smidge. Well..at least in less than 4 yrs.
And its very "voltage" responsive...IE..if the voltage you feed the electronics changes...so will the outputs. I see clients moving a machine from one side of the factory to the other..or to another site..one site may be 224volts..the other may be 245volts..and it does..does change things. Still runs fine..but may run slower, or with less accuracy.
Gunner

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On Fri, 23 Jul 2010 14:47:43 -0500, Ignoramus7608

Did they tell you how to adjust Test Offsets? Very critical for proper and clean movements.
Gunner
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You seem very knowledgeable here. I've turned it till it drifts left, then turned it till it drifts right. Split the difference. Is this correct?
BTW, I have a Z servo that will vibrate on occasion. Used to be only once in a great while, now once out of ten jogs. I just give it a nudge to stop. But, I need to retune this, someday; when I get one of those round tuits.
Karl
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On Fri, 23 Jul 2010 18:49:48 -0500, "Karl Townsend"

Correct in theory. Put a volt meter on...hummm 3 and 4 (pins on the header connector) and set the last pot on the right... for IRRC...Zero Volts. As you jog in opposite directions...it will go +/-,,,,but it should go to the same voltage ..just plus/minus
The OmniTurn has a screen that shows both test offset and following error that allows one to tweak the amps while watching the screen.
Im so used to using that screen..Im having a stroke moment trying to remember the method without the screen.

Back off the far left gain pot a couple turns and see what it does.
Here is the owners manual for most of the early versions..
http://omniturnfactorydirect.com/OmniTurn_Manual_G3_100128.pdf
Download it and go to section 6 and check the data for the AMC amps and tuning. It may be of some assistance.
Gunner

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...

Say, i scanned the gcode section trying to get to section 6. Omniturn has a great write up here. Much better than the fanuc yellow manual I go by. Of course, some Gcodes are different so i can't just copy it.
Karl
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On Sat, 24 Jul 2010 09:31:30 -0500, "Karl Townsend"

Ayup..each manufacture has different Gcodes, particularly canned cycles and whatnot, but some of the stuff is pretty much common. Mike did a very good job trying to make sure end users understood what was going on, and why.
I had a small hand in some of the manual as well..but very small.
I had a slightly larger hand in writing some of these....
http://www.omni-turn.com/Pages/Technical%20support/Tech%20support%20page.html
Stuff like this....
http://www.omni-turn.com/Pages/Technical%20support/AMC%20amp%20adjustment.html
http://www.omni-turn.com/Pages/Technical%20support/OmniTurn%20amps%20-%20Tuning.html
http://www.omni-turn.com/Media/PDFs/Spindle%20repair%20procedure%20LR.pdf
And a fair number of the other stuff....shrug
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wrote:

And I see they posted the new Generation 4 manual..which is mostly backwardly compatable with most of the older machines.
EXCEPT for older Servo Amps..it only covers the OmniTurn/Glentek servos. Damn..why the hell...never mind.....
http://omniturnfactorydirect.com/OmniTurn_Manual_G4_100611.pdf
Check out the G code listing on page...hummm 1.22 or somewhere about there.
Gunner
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They did not tell me that, but I would ilke to know!
i
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