How to convert PID value From Omron E5-AN-HT to use in C_CU function block.
I am quite new to ABB DCS system. Currently I am finishing off my first Freelance project for a chemical processing factory. I have a bit of problem with one of the PID loop. This loop is quite tricky to tune.
I tried self tune FB for several hours with verry little luck as the valve keep dancing and tempreature goes up and down after the process is completed.
The system in question have an omron E5-AN-H to takecare of the loop which used to be very stable. The omron have the value inside the controller as:
P = 38.5
I = 183
D = 314
How do I take those number and convert it to the format that C_CU block understand?
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OK, I dont know the answer to your question, but it looks like the Omron gain is actually "PB" so the Freelance gain is probably 100/38.5 = about 3.0 , the Integral time is likely 183 seconds and also D=314 seconds
But your post points to a serious issue that cannot be resolved by "tuning" the loop. A temperature loop should be stable. If the temperature "keeps dancing up and down" and auto tuning or manual bump tests do not produce consistent results then you likely have a faulty valve or some other physical problem in the plant.
Stop trying to tune this loop. You are wasting your time. Get the valve inspected and repaired. I would expect the the valve is suffering from some significant backlash and probably sticking as well. Once the valve is repaired you can try tuning again. You also need to go inspect the temperature transmitter and ensure it is installed properly and in a location that gives consistent and relaiable measurement. Remember, the MOST important tuning tool is a decent pair of boots - Go look at the plant.
OK so the current tuning values on the Omron are relatively stable and the problem shows up when you connect the Freelance controller ?
I'm going to revise my previous answer about PID settings since I finally did what I always tell everyone else to do and RTFM ... and yes, you should have done this too :)
The PB settings depend on which input channel you are using ...Temperature input: 0.1 to 3240.0 C or F in units of 0.1 C or F
Analog input: 0.1% to 999.9%FS (in units of 0.1% FS)
The I and D Units for the Omron are 0.1 Secs not Seconds.
So the correct conversion of I and D is (probably)
I=18.3 seconds, D=31.4 seconds
Converting P is less clear. Its 100/38.5 * some scaling factor. Where the scaling factor is likely either 1 or 3240/100 for Temperature or 999.9/100 for Analog input. Which gives you a choice of P=3, P=1 or P=0.3. Given that your current Freelenace PID settings are highly unstable it is pretty likely for a temperature controller P=1 and for an "analog" controller P=0.3
Also, there is not much detail on what algorithm the Omron controller uses. For example it would be nice to know if it uses a serial or parallel PID. Given that the Omron has a choice of user selected scan rates for the PID ~hopefully~, the PID settings are not dependent on the scan rate of the controller. You could probably check the control period of the Omron and run the Freelance controller at the same rate to be sure.