Ecostruxure Machine Expert M241 PID Auto Tuning

[KarimSoliman]

Hello everyone,

I'm currently working on a project that adjusts the speed of a water pump based on the outlet pressure. I plan to use a PID controller for this purpose. However, I couldn't find any auto-tuning functionality within the project libraries. Manually tuning the PID parameters on-site would be quite time-consuming, so I'm looking for a way to implement auto-tuning using the PLC. Has anyone tackled something similar or have suggestions on how to approach this?

[BevanWeiss]

Have you seen the FAQ here?
https://www.se.com/in/en/faqs/FA309271/

I assume that this SoMachine functionality here was brought forward in the renaming to 'EcoStruxure Machine Expert'..

If there's additional loop complexity (i.e. variable number of pumps etc), then I've often found that auto-tuning can be problematic, and you really need to have some knowledge of how the PID does its magic (i.e. understanding the Proportional / Integral / Derivative terms, however they're calculated, and what things contribute to overall loop gain, and loop response).

[KarimSoliman]

I think this article is related to machine expert basic, i was wondering if there is auto tuning mode like this mentioned in the article but with machine expert.

[Bastian_Schmitz]

There is a autotune function for PID heating control integrated. 

https://product-help.schneider-electric.com/Machine%20Expert/V1.2/en/comtb/comtb/Function_Blocks/Fun... 

An other autotune is not integrated. With ESME Basic and ESME HVAC you will get an autotune function.

[freemanodu]

There is a autotune function for PID heating control integrated. 

https://product-help.schneider-electric.com/Machine%20Expert/V1.2/en/comtb/comtb/Function_Blocks/Fun... 

An other autotune is not integrated. With ESME Basic and ESME HVAC you will get an autotune function.

Etiket ekleHow and where can I download this library? It is not in my library.

[freemanodu]

There is a autotune function for PID heating control integrated. 

https://product-help.schneider-electric.com/Machine%20Expert/V1.2/en/comtb/comtb/Function_Blocks/Fun... 

An other autotune is not integrated. With ESME Basic and ESME HVAC you will get an autotune function.

[Bastian_Schmitz]

It is hidden here

[freemanodu]

Thank you very much, my problem is solved.

I was using v1.3, when I updated to v2.2, I was able to load the library from where you showed. Now I can add the function block.

[KarimSoliman]

So it is working only with heating application and not applicable with pump operation?

[Bastian_Schmitz]

Yes that is correct, but in the end I should not make a difference.

Because heating application will rise the output if the actual value is lower then the setpoint.

And in Booster pumping application the output will also rise if the actual value is lower then the setpoint. 

The process of the autotune mechanisme is the same. 

As alternativ you could ask ChatGPT or Copilot to creat a function for this purpose. 

Here an example 

FUNCTION_BLOCK FB_AutoTune_PID_ZN
VAR_INPUT
    xEn : BOOL; // Enable autotuning
    fSetpoint : REAL; // Setpoint in Bar
    fActual : REAL; // Actual pressure in Bar
END_VAR

VAR_OUTPUT
    fP : REAL; // Proportional gain
    fI : REAL; // Integral time
    fD : REAL; // Derivative time
END_VAR

VAR
    fError : REAL;
    fPrevError : REAL;
    fKu : REAL; // Ultimate gain
    fPu : REAL; // Oscillation period
    iWaveStep : INT;
    tStart : TIME;
    tNow : TIME;
    bOscillating : BOOL;
    tLastPeak : TIME;
    tCurrentPeak : TIME;
    bPeakDetected : BOOL;
END_VAR

IF xEn THEN
    fError := fSetpoint - fActual;

    // Simulate 3 wave steps to provoke oscillation
    CASE iWaveStep OF
        0:
            fKu := 1.0; // Initial guess
            tStart := TIME(); // Start time
            iWaveStep := 1;
        1:
            // Detect oscillation peak (simplified)
            IF fError > 0.05 AND NOT bPeakDetected THEN
                tLastPeak := tCurrentPeak;
                tCurrentPeak := TIME();
                bPeakDetected := TRUE;
                IF tLastPeak > T#0s THEN
                    fPu := REAL_TO_TIME(TIME_TO_REAL(tCurrentPeak - tLastPeak));
                    iWaveStep := 2;
                END_IF
            ELSIF fError < 0.01 THEN
                bPeakDetected := FALSE;
            END_IF
        2:
            // Apply Ziegler-Nichols closed-loop tuning rules
            fP := 0.6 * fKu;
            fI := fPu / 2.0;
            fD := fPu / 8.0;
            iWaveStep := 3;
    END_CASE
END_IF

TM241 isn´t the controller for pumping applications. Regarding to this point such a function is missing. 

[KarimSoliman]

Dear Bastian,

Thanks for your support and your kind replies.

[AlbertoJD2]

Glad to hear the update fixed it! I had a similar issue on v1.x before too, jumping to v2.2 definitely makes things smoother. Curious, which function block did you end up using?