Pid slc500

Hi all..

I've been reading through many of the posts on this Forum, lucky i found similar problem in-regard to PID Loop and concerning PID process control in RSLogix 500. I have developed a programmed the control incorporating all that I've gathered ideas on this site, however I am not getting the PID Loop to fully functional and control my intended process and wanted to ask a help from you and to all great mentors here in this forum, Did i something miss on my program?

Thanks a lot and for your patience..

however I am not getting the PID Loop to fully functional and control

Click to expand...

A little more info about the above would help someone help you.

From what you have posted your PID instruction should be on a unconditional rung.( remove the GEQ amd LIM). If you want to check the process variable for a valid value do it on a rung above the PID.

It also would be best to post the whole program, it's .RSS file ( zip it first)

Mickey said:

From what you have posted your PID instruction should be on a unconditional rung.( remove the GEQ amd LIM). If you want to check the process variable for a valid value do it on a rung above the PID.

Click to expand...

Hi, Thanks a lot for the reply,

I tried to removed the GEQ and LIM, but still the same, Scaled Error of PID still 0.

Please see the attach file of Plctalk.zip..Please do changes if their something that i missed.

Thanks a lot in advance.

your PV is coming from N7:100 ... why? ... that appears to be a static number – NOT a number from an analog input ... (did you just type this number in for testing?) ...

your PID has a setpoint of 600 ... the PID sees your PV as a scaled value of 983 ...

basic answer:

since your PV is already above the SP, then the PID is trying to DECREASE the output (the CV) ... currently it has the output turned completely off ...

suggestion: type in a series of smaller and smaller numbers at N7:100 ... once the PV goes below the SP, then you will probably see some output action from your PID ...

Mickey is right – in RSLogix500 systems your PID must be on an UNCONDITIONAL rung in order to give you good results ...

DISCLAIMER: swamped with work right now – this is just a quick glance ... I'll write more later if possible ...

Mickey said:

A little more info about the above would help someone help you.

From what you have posted your PID instruction should be on a unconditional rung.( remove the GEQ amd LIM). If you want to check the process variable for a valid value do it on a rung above the PID.

It also would be best to post the whole program, it's .RSS file ( zip it first)

Click to expand...

Ron Beaufort said:

your PV is coming from N7:100 ... why? ... that appears to be a static number – NOT a number from an analog input ... (did you just type this number in for testing?) ...

your PID has a setpoint of 600 ... the PID sees your PV as a scaled value of 983 ...

basic answer:

since your PV is already above the SP, then the PID is trying to DECREASE the output (the CV) ... currently it has the output turned completely off ...

suggestion: type in a series of smaller and smaller numbers at N7:100 ... once the PV goes below the SP, then you will probably see some output action from your PID ...

Mickey is right – in RSLogix500 systems your PID must be on an UNCONDITIONAL rung in order to give you good results ...

DISCLAIMER: swamped with work right now – this is just a quick glance ... I'll write more later if possible ...

Click to expand...

Hi,

Yup, N7:100 is link in the HMI so that i can easily manipulate the simulation analog input in the HMI.

I tried SP greater than PV based on the E=SP-PV, but still the same no output even the Scaled error still zero, did i missed something on the PID?

and also i tried to removed the GEQ and LIM but still the same..maybe there something that i missed.

Thanks a lot.

Post your corrected program, the one the above screen shot is from.

Save the program while it's in the run mode.

In the downloads area there a file called hotrod.zip. It has ml1500 and slc500 PID examples in it.