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Simple PID loop


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Hi ,
I have been working with the PID loop and it seems very complicated.  I just want a simple PID loop (I'm anti auto tune) with manual mode (straight output) and automatic mode (with manual tuning)  and I've seen posts that seem to imply that this can be done.  
Would I used the Run PID function?   Or set the parameters in the config struct,  Load PID AutoTune Data, then save it? and then Run PID?   Would I use the PID AT Params or PID_Config struct or both?   I only need a PI controller - so would I need to set SP, PV, P, I, Control Valve, Reverse Action (Does this account for a negative sign in the PI values?),  and what else is mandatory at a minimum?  Do I need Sample Time, and the Input and Output Highs and Lows?   Is there a better way?  

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  • 5 months later...


As you mentioned you dont have to use PID Autotune. You can directly use the RUN PID Ladder element. 

when using the PID RUN , you will need to configure the struct PID Config (non -retained struct) - there you can enter the parameters you wish to use.

Once you got good results, you can use the save PID to save to the struct PID AT params (retained struct) .

When the PLC powers up you can load the parameters from the PID AT params to PID config.


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