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Submitted by Showmark on Wed, 01/24/2007 - 05:42

I am using a 2143 controller. I have X and Z as a payoff and take up of fiber optic wire. My program consists of two threads for coarse and fine tension control. I currently have both motors tuned to KD=90 KP=9 KI=0 and while the system runs smoothly the responsiveness is low enough that my tension increases drastically however when I increase the values the motors begin growling. Is there anything else I can do that will allow for the fine tension control I need?

The tension program itself is as follows

#COARSE
GAX=Z
GRX=G
ZP=_TPZ
XP=_TPX
MFZ=ZP+@INT[SPEED/9]
ZN=_TPZ
XN=_TPX
DZ=ZN-ZP
DX=XN-XP
IF DZ0
G=DX/DZ
ENDIF
JP#COARSE
EN

#FINE
CORRECT=1500
JGX=0
BGX
#FLOOP
TENERR=(@RND[(TENSION*SCALE)*100]/100)-(@RND[(@AN[1]+.87)*100]/100)
JGX=TENERR*CORRECT
JP#FLOOP
EN

Thank you for your help.

Comments 1

Galil_AndyH on 01/25/2007 - 14:53

I do see a couple of issues with your code that might be causing your problem.

1. The loop for the #COARSE is too large. Jump to below the GA command, or set the new GR after the G=DX/DZ command and jump below the GR command.

2. Is it possible that the MF command is causing a bottle neck and not allowing the gear ratio to change quickly enough?

What we often do is just look for a change from the original position before changing the gear ratio. So for example:
[code]#COARSE
GAX=Z
GRX=G
ZP=_TPZ
XP=_TPX
#GEAR ;'NEW
ZN=_TPZ
XN=_TPX
JP#GEAR,XN=XP;'CHANGED (FROM MF)
DZ=ZN-ZP
DX=XN-XP
IF DZ<>0
G=DX/DZ
ENDIF
JP#GEAR ;'CHANGED
EN[/code]3. You may also want to monitor the values of JGX, TENERR. If they are changing greatly or oscillating, then the #FINE loop may be too active.

Concerning actual tuning; have you tried introducing any KI into the axes? Try a low IL and very low KI and see if that helps at all.

What might also help is to introduce a pole filter. This will allow you to increase the KP and KD. Start with a low number (high frequency) and work from there. If the system becomes unstable, you have increased the pole too much.

If you have questions about the pole filter, e-mail support@galilmc.com