Rslogix5000 PID oscillating between 0 and 100 percent

[p_logix]

Hello all,

I cant figure out why my PID is oscillating between 0 and 100 percent. My set point is steady and whenever I take my PID out of software manual and put it in auto my CV jumps from 0 to 100 percent. We had a problem where a bus bar blew up and caused our network to go down. The program and gains have not changed.

Any ideas?

-Thanks

 

[labeledas]

So it goes nuts in auto. And worked before. Is your pv steady. Any noise on the line since the mishap.

 

[p_logix]

I got it. I had to set the output limit high to 99% the back to 100 %. And the PID took off. I found a technote through RA KB.

 

[proof]

Hello all,

I cant figure out why my PID is oscillating between 0 and 100 percent. My set point is steady and whenever I take my PID out of software manual and put it in auto my CV jumps from 0 to 100 percent. We had a problem where a bus bar blew up and caused our network to go down. The program and gains have not changed.

Any ideas?

-Thanks

You aren't clear.
You have it in manual at 0, then put it in Auto and it swings from 0 to 100 and then back to 0, or just go from 0 to 100? If it swings back and forth, try reducing your P and I gains by half until it quits swinging.

 

[p_logix]

You aren't clear.
You have it in manual at 0, then put it in Auto and it swings from 0 to 100 and then back to 0, or just go from 0 to 100? If it swings back and forth, try reducing your P and I gains by half until it quits swinging.

PV was steady and so was the set point. The controller turns into bang-bang control.


I figured it out. It was swinging back and forth 0 to 100%. It is actually a software problem with Rockwell PIDs. The work around fix is to make a small change to the output limit high hit apply then put it back to the original setting hit apply then the PID starts working. So I went from 100% to 99.99999% then back to 100% while in software manual. After putting it back in auto the PID controller wakes up and starts working.

Thanks