PID with 5i25/7i76 and DG4S Servodrive

Good afternoon,

Im trying to control small stages (50mm run) XZ config. with

LinuxCNC 2.6.4 on UBUNTU 12.04 LTS

For the Hardware I have:

* 5i25/7i76 Plug-and-go kit

* 160 V and 35A Servodrive requiring STEP/DIR signals

* 24VDC Servomotor

* glass scale incremental encoder that closes the loop to the servodrive.

I have made all necessary connections and did the PID tuning with stable results by using the PID tuning software that comes with the servodrive.

I ran pncconf with the 5i25 firmware: 7i76x1 (firmware manually added with information and files I found in this forum. THANK YOU).

The result so far is as follows:

I start LinuxCNC with no issues but when I jog move the motor, the movement occurs but the sound is not nice, it is as if the PID tuning in not done.If I let the testing of the pncconfig run the motor back and forth about 6mm, the motor and wiring seem to overheat and also the sound in not correct, again, as if the PID settings were not correct, however if I unplug LinuxCNC and move the motor with the servodrive PID tuninig software once more, it moves correctly and it also sounds correct.

Since I´m new to this, I hope my questions make sense.

1. Do I have to run some kind of PID tuning inside Pncconfig itsef? I have looked all menus and I could not find out how.
2. If my procedure is not correct can someone point me in the right direction to configure this type of hardware?


Jorge

Are you running the servo drive from 24VDC?

If this is simply a open loop step/dir system (no encoder feedback to linuxcnc)
this is most likely a drive tuning issue

The 24VDC powers the servomotor through the servo drive, the servo drive itself is powered by 5V coming from the 7i76 card.

It is a closed loop Step/Dir system, the encoder is connected to the servodrive. (not to the card)

Jorge

I would call that an open loop step/direction system since
the scale position is not brought back to linuxcnc to close a position loop

With an open loop step/direction system, all tuning is done in the drive
except step generation tuning

Plotting the stepgenerator command and feedback (with Halscope)
will allow you to determine if theres something wrong with the drives tuning
or the stepgenerator tuning (less likely).

These are the pins to plot for axis 0:

axis.0.motor-pos-fb
axis.0.motor-pos-cmd

I'm new to this so now I know this is also called an open loop. Thank you.

Since trying different things did not help to improve the movement of the motor I decided to go back and check the wiring once more. I found out that the connections were correct but the wiring diagram WAS NOT!

The wiring diagram seems to be an old version or something.

I rewired everything by continuity checks and now everything is running smooth.

The motor does not make any noise, it does not show any position errors and the linear stage moves like if it was levitating!.

Also the current consumption is within the motor specs, not as before.

Great! now I will set the limit switches.