Fanuc servo questions again

[JoeM1]

Gentlemen,
More questions about Fanuc servos, with a PowerMate H as the motion controller.

I have gotten as far as getting motion out of the three servos that have been causing issues.

The gain was way too high, causing them to oscillate and eventually a hi current fault would be generated.

The thing is, this is a rotational axis that can have no overshoot. It can also not have a soft stop. (should not be able to turn by hand).

I have been experimenting with different gains.
I also lengthened the deceleration parameters so that we were not "hitting the brakes" hard. This got rid of the overshoot, but it still has a really soft stop. You can turn it by hand.

Also a related question:

How do you tune this servo system? It has red-cap servos and this PowerMate H motion controller. I do not have the full Fanuc HMI, just the little DPI handheld. Is there a auto-tune function?

All assistance is very welcome.

 

[Steve Bailey]

Have you selected the correct motors in parameter 2020? The Power Mate H startup guide GFK-1383 has a table of parameter 2020 values corresponding to the middle four characters of motor model number (A06B-xxxx-Byzz). If you need to change, you must first set parameter 2000#1 from 1 to zero. Then after changing a value in parameter 2020 you need to cycle power There are default tuning settings for each motor. Also check parameter 2021 which is the load inertia ratio.
Parameter 1825 is servo loop gain. It defaults to 3000. Raise the value if response is sluggish. Lower the value if the axis oscillates.

 

[JoeM1]

Steve,
Thank You.
This was very helpful and successful.
This was one more step in the right direction.