Logix 5000 For Air/Fuel Curves

Yoda_the_Teckie

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• Jun 24, 2020

• #1

I am about to be upgrading several compressor engines to Logix 5000 and I am looking for the best, proven, ways to program in the various curves. I believe that this can best be accomplished using a lookup table function, but I have not personally done that before.

Any advice?

Thanks!

 

drbitboy

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• Jun 24, 2020

• #2

What is your desired accuracy?


If they are smooth, I would suggest a Chebyshev approach, converted to a polynomial.


What is the coding environment e.g. ST? Ladder?

 

Yoda_the_Teckie

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• Jun 24, 2020

• #3

The programming can be done in ladder or ST.

The accuracy of the curve needs to be pretty tight. We use the air/fuel curve to control ignition timing.

 

drbitboy

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• Jun 24, 2020

• #4

Does it look like the plot on page 18 here: https://www.osti.gov/servlets/purl/841083? Or the plot on page 10?




Maybe a better question is, what are you measuring, and what are you controlling?

 

Phrog30

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• Jun 24, 2020

• #5

Have you noticed the FGEN instruction? It's only in function block and ST, no ladder.

 

drbitboy

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• Jun 24, 2020

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Phrog30 said:

Have you noticed the FGEN instruction? It's only in function block and ST, no ladder.

Click to expand...

Ooh, nice.

 

Yoda_the_Teckie

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• Jun 24, 2020

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drbitboy said:

Does it look like the plot on page 18 here: https://www.osti.gov/servlets/purl/841083? Or the plot on page 10?




Maybe a better question is, what are you measuring, and what are you controlling?

Click to expand...

It looks very much like that curve. And the formulas contained in that paper are exactly what i am looking for.

So, we are controlling engine ignition timing according to the air/fuel curve, exhaust manifold temp curves, etc. There are around 4 curves that are used. They work on a low signal select control scheme. So, basically I am looking for any way to program a curve into the PLC and have it produce an result that can be scaled and output.

 

Yoda_the_Teckie

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• Jun 24, 2020

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drbitboy said:

Ooh, nice.

Click to expand...

I have not looked at that yet. I will look at it as soon as I get the chance.

Thanks!