Servo Wiring and Tuning detailed How To example Mesa 7i77.

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7 years 2 months ago - 7 years 2 months ago #143607 by PCW
I would 1.
set all I terms to 0
set the P value low

Dial in FF1, its the most important tuning number for velocity mode drives
FF1 = 1 cannot be right unless the axis move at 10 IPS at 10V

You can also verify that the drives are operating in velocity mode
by setting the analog voltage to 0 (set P=0 in the calibrate menu)
The motors should hold position or drift slowly, and in any case resist
applied torque.

2. Do a halscope plot of commanded velocity and following error for a short move
Last edit: 7 years 2 months ago by PCW.

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7 years 2 months ago - 7 years 2 months ago #143610 by randypetersen
When I set P=0 on both my X and Y they both can easily be pushed.
They come up "Joint x following error"

When they have a value, like 50, then I can not push them.

At first I thought my ferror was set to small thinking I was pushing them then triggering a joint following error and then disabling the drivers so they could move.

Was that the expected behavior? or did I screw something up.

The machine is working, it's just I have to apply very little force to the motors, or I get following errors.

I wanted to check X and Y, since my X driver is a different brand/model than my y and z. I thought for sure that the odd driver would be the Z, because it had the brake and the screw drive. When I got the machine the odd driver " Advanced Motor Controls" was the X and the Y and Z were using the "Copley Controls" very possible I wrote that down wrong before I disassembled it.
Last edit: 7 years 2 months ago by randypetersen.

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7 years 2 months ago #143612 by PCW
Sounds like is it running in torque mode ( are there tachometers at all? )

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7 years 2 months ago #143613 by randypetersen
There is a "TACH" input on the driver, but I don't have anything connected to it, and I checked the old ribbon controller that was connected to the old controller and the TACH pin wasn't used either. Only thing coming from motor is Power and Encoder (i believe) and brake for Z.

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7 years 2 months ago #143627 by randypetersen
Having difficulty finding any servo tuning information on servos operating in TORQUE mode. Does anyone know of any tuning resources for me?
Thanks

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7 years 2 months ago #143628 by PCW
A _very_ rough guide is this (for a single PID loop/Axis)
Start with FF1=0 and FF2 = 0 and I=0

Chose a small amount of P (say 50 = full torque with 1/5" error)
Then increase D until it gets too "buzzy" and then back off about 30% on D
Then increase P until you get oscillations and again back off about 30%
Then adjust FF2 so that you neither overshoot or undershoot during
acceleration (the FF2 setting is inertia dependent so its better to do this with a typical table load)
Finally increase I until motion becomes unstable (Watch out for WIDE oscillations here)
and back off about 50%
The following user(s) said Thank You: randypetersen

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