I'm using PID and SSR to control temperature (60KW). I use PDM to have PWM signal for output PLC. I don't know how to choose the parameters of PID ( Kp, TN, TV, Y_Offset) to suitable with PDM. Because the input of PDM is from 0-32767 ( 0-100%). Somebody can help me!

first i would scale my in and output, to 100% using real.

then put the Kp on about 10

leave the rest zero.

start process.

if the temp gets steady put the Kp higher.

until the temp will oscilate maybe very slowly like hours.

this will give optimum Kp for this process.

then start with very long Ti as the process is very slow. like 120 minutes

reduce it slowly until oscilation again.

Do not use the D factor , your temp is too slow for it.

I chose Kp=10000 ; Ti= 10000 (s);Td =0; Y_offset = 10000. it was ok! but e= | PV-CV| is too high.

When i chose Kp= 10000 ; Ti=10000 (s); Td=0; Y_offset = 0, it was not ok!

So can you tell me what Y_offset mean in this case ( i mean in the PID function block of codesys) And how can i decrease e = |PV -CV|

Thanks,

Tung Bui Huy

Automation Engineer

when you put offset on the output the difference e will be high.

probably the K is too much for the proces.

Thanks for your support!

I will check it!