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Controlling condensing temperature by controlling opening valve

I modified the code, and it works but I need to determine the gains because I just assumed them

alhabeeb_0-1724407969960.png

 

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Message 11 of 22
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Hi alhabeeb,

 


@alhabeeb wrote:

I modified the code, and it works


It looks much better now.

You should add a small wait inside the loop and limit the output range of the PID.

 

 


@alhabeeb wrote:

I need to determine the gains because I just assumed them


Yes. See my comment on step responses above...

 

You could also try to determine PID gains from analyzing your system:

  • heat capacity and massflow of the hot fluid
  • heat exchange rate and (thermal) delays in the cooler
  • input temperature and (max) massflow of tap water

After all it's a "simple" physical system! 😉

Best regards,
GerdW


using LV2016/2019/2021 on Win10/11+cRIO, TestStand2016/2019
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Message 12 of 22
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@GerdW  a écrit :

Hi alhabeeb,

 


@alhabeeb wrote:

I modified the code, and it works


It looks much better now.

You should add a small wait inside the loop and limit the output range of the PID.

 

 


@alhabeeb wrote:

I need to determine the gains because I just assumed them


Yes. See my comment on step responses above...

 

You could also try to determine PID gains from analyzing your system:

  • heat capacity and massflow of the hot fluid
  • heat exchange rate and (thermal) delays in the cooler
  • input temperature and (max) massflow of tap water

After all it's a "simple" physical system! 😉


Should I use case structure to add limits to PID?

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Message 13 of 22
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Hi alhabeeb,

 


@alhabeeb wrote:
Should I use case structure to add limits to PID?

No, you should read the LabVIEW help for the PID function…

Best regards,
GerdW


using LV2016/2019/2021 on Win10/11+cRIO, TestStand2016/2019
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Message 14 of 22
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@GerdW  a écrit :

Hi alhabeeb,

 


@alhabeeb wrote:
Should I use case structure to add limits to PID?

No, you should read the LabVIEW help for the PID function…


Ohh, Yes it is very straightforward.

Thanks

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Message 15 of 22
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@GerdW  a écrit :

To determine the PID gains you can do some step-response tests and apply the common rules on the step response measurements.

Thanks for all your support. I'm new to use Labview, and I know a little about the control. Would you give me more details about how to determine the gains? 

Thanks

 

Baqer

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Message 16 of 22
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Hi alhabeeb,

 


@alhabeeb wrote:
Would you give me more details about how to determine the gains? 

Have you tried to search for manuals (using your favorite web search) on your own? "Searching for relevant information" is basic knowledge for engineers!

 

I found this article easily…

Best regards,
GerdW


using LV2016/2019/2021 on Win10/11+cRIO, TestStand2016/2019
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Message 17 of 22
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I used this, and it worked with my system.

 

alhabeeb_0-1724662768793.png

 

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Message 18 of 22
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Hi alhabeeb,

 


@alhabeeb wrote:

I used this, and it worked with my system.


So you implemented a plain P-controller!?

 

This is (in my experience) VERY unusual for a thermodynamic system, involving heat exchangers with massflow-dependent properties!

Best regards,
GerdW


using LV2016/2019/2021 on Win10/11+cRIO, TestStand2016/2019
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Message 19 of 22
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Hi,

Right now my test bench is not completed, so I just attached a thermocouple on the tap water pipe to represents the (T_f_out) and run the VI. When  the T_f_out greter than the setpoint the valve opens and when it is lower the valve close. If the T_f_out high greter than the setpoint, the valve is full open.    

 

alhabeeb_0-1724665564051.png

 

alhabeeb_1-1724665626434.png

 

alhabeeb_2-1724665838695.png

 

 

 

 

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Message 20 of 22
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