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Temperature control using PID

Hello 
My goal is to control the temperature of the water inside a pipe by using a valve. ( actually, this is only a part of my code).
I have used PID Autotuning (Temperature) VI for controlling the valve ( I understood for a process with delay this VI is proper with smith predictor). This process has a large delay because the sensor is far from heating source (boiler). (It is not possible to change the place of the sensor). I have measured plant parameters like dead time, time constant and process gain. 
Dead time is more or less 11 minutes and the time constant is also 12 minutes. My questions are:

1) Is it the correct VI for controlling this kind of process ?

2) For tuning of this PID what is the best method? I know Z-N method is common but in this case dead time is not less than half of the time constant. Cohen coon ? Internal Model Control Autotuning Method?

Any suggestion?

 

 



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Message 1 of 4
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Hello,

according to LabVIEW Help, the PID Autotuning (Temperature) VI seems to be the right choice for systems that contain significant dead time; it can be used to improve performance of not only temperature systems, but also other types of systems that contain dead time. This VI uses internal model control to compensate for dead time and tune the system. The Cohen-Coon Autotuning Method is similar to the Ziegler-Nichols method, but provides better results when the controller has a large deadtime relative to the time constant.

Hope this helps!

Regards,

Alessia

Message 2 of 4
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Does the boiler have a temperature sensor as well?

 

If so, two cascaded PID controllers might help.

 

Cascaded temperature control is actually an example on the PID controller Wikipedia page.

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No, unfortunately, the boiler does not have any temperature sensor

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