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PID autotuning help

Hi,

 

is there something wromg with my control model simulation in the attached vi? I tried to autotune the two cascaded controllers I have but I can't seem to even get that working...

 

Any help would be greatly appreciated. Thanks

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Hello Hendrick,

 

This is Andrew Brown, an Applications Engineer from National Instruments. In order to help with your PID control model simulation, I would like to ask some general troubleshooting questions:

 

1. Are you starting from a set of LabVIEW programs / functions? If so, can you please point me to them?

2. Are you interfacing with any physical devices / hardware with this code?

3. When you say that the autotuning isn't working, is the program failing or are the results just incorrect?

4. Could you give a brief overview of the system you are modeling?

 

I will be happy to help troubleshoot your program. However, I am unable to run the LabVIEW program you provided due to missing functions such as "PID Autotuning.vi" and "CD Convert Simulation to Control Design.vi".

 

 Some basic resources for troubleshooting LabVIEW programs are Debugging Tools in NI LabVIEW and Debugging Tips and Tricks. Please let me know if you have questions about these resources or about troubleshooting your program.

 

Regards,

 

Andrew Brown

Software Engineer
National Instruments
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@Andrew B wrote:

I will be happy to help troubleshoot your program. However, I am unable to run the LabVIEW program you provided due to missing functions such as "PID Autotuning.vi" and "CD Convert Simulation to Control Design.vi".


Hi Andrew - you're at NI, you have access to all the LabVIEW add-on toolkits, right?  You may want to install them.  "PID Autotuning" is part of the PID toolkit.  The other missing components are part of the Control Design and Simulation module.

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The way that your VI is configured will not update your PID gains with the new auto-tuned values. Take a look at the General Auto PID Simulator VI example to see how the autotune VIs work with local variables. 

John B.
Embedded Networks R&D
National Instruments
Certified LabVIEW Developer
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Hi,

 

I've attached an updated version of the .vi but I'm stull unable to tune the PIDs (I have added sinusoidal disturbances to this model). I have followed the updating of the PID gains from the example. Thanks

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It seems like it is auto-tuning, but the process variable is changing very slowly. I'm going to play with it a little bit to see if I can get some better performance. I suspect that we just need to change the relay gains.

John B.
Embedded Networks R&D
National Instruments
Certified LabVIEW Developer
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