joint0 following error fault

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12 years 9 months ago #42274 by southbayguy
Right now I can afford only one motor and drive so I am only trying to get the X axis (joint 0) going.
Gotta say this Linux CNC software is pretty darn good; it has just about worked out of the box.
I have a 31 oz-in Pittman servo motor running off an Advanced Motion Controls AZ12 drive being commanded by a */- 10V current command signal.
The system is stable, jogs at speed, holds position when stopped.
Here's my issue:

When I turn the shaft of the X motor while it is holding position, it fights me (which it should do) trying to stay where it is commanded to be.
If I muscle up on it a bit, get it .002 off position, it faults out with a joint 0 following error.

The .ini file for joint 0 has FERROR set to .020 ... so I don't see why it's faulting out at .002.
For fun, I edited the .ini file for joint 0 and set FERROR to 1.00, and re-started the application. Made no difference.

I'm thinking the software ignores the .ini file and gets a max following error parameter someplace else.
Does anyone have any guidance for me?
Thanks.

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12 years 9 months ago #42275 by PCW
Replied by PCW on topic joint0 following error fault
There are two following error settings:

FERROR and MIN_FERROR

The actual limit value chosen is proportional to
the current velocity with MIN_FERROR used at 0 velocity
and FERROR used at the maximum velocity.

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12 years 9 months ago #42282 by southbayguy
Okay ... so since my X motor is at zero velocity then the min following error parameter is used.
Thanks. Gotta go test.

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12 years 9 months ago #42307 by southbayguy
It works. Setting min following error = max following error = .020, I can crank on the motor shaft all I want (get to about .006 error) and no alarm. Thank you.

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12 years 9 months ago #42318 by andypugh

southbayguy wrote: It works. Setting min following error = max following error = .020, I can crank on the motor shaft all I want (get to about .006 error) and no alarm


The next step is to put in the correct values...

You typically do want max to be more than min, one sets the limit during rapids, and one during machining, and you have different levels of concern in each mode.

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10 years 4 months ago #75749 by chuchengbing
i have the same question with joint 0 following error, i don't think setting min_ferror = ferror is the answers to this question, the following error occurs when i want to set the value near approaching to zero. i check the pins of f-error,f-errored,pos-cmd,pos-cmd, i find it doesn't excel the f-error-lim. Do you have any answers? Thanks.

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