PID Autotune

[romario86]

Hello could you help me, 

I have mashine flow heater and I need regulate a temp of water via PID. 

But my PID not working good. 

I did Auto tune, but PID output still hold same value, and auto tune take 1 hour without any results and without 

change of PID output value. 

My PID working nearly same. PID set some value and still hold it. no influence on output temperature. 

Do you have any idea where can be problem. 

 

I have now for example 50°C as set temp, and output temp is 57°C 

Its not good regulation, and PID still hold for example 40% power

 

'My progam is in Czech language, but maybe somebody help me. 

PID parameters you can find in subrutine Vypocty>13network 

Configuration is in main routine. 

 

Thanks for help Romario

709_SW_39161RJv1.vlp

[Joe Tauser]

As you've seen, Autotune doesn't always work so well.  It will get your parameters kind of close, but it sounds like you'll have to finish tuning manually.

 

If the output temperature is fairly steady (not oscillating), then the P value is OK.  Increasing P will make the system more stable but slower, decreasing P will speed things up but it may go out of control.   

 

Once it's stable, try setting your D value to zero and then cut the I value in half and see what happens.  If it doesn't go down enough then reduce the I value some more.

 

Joe T.