PID problem (unstable)

[vedran]

Hi,

i have DAQ-6024E and the PID-Toolbox. I'm trying to build some PI-Controller for my DC-Motor. I set "range output" to 0-10V, my "setpoint" ist between 0 and 60W (u*i) and my "process variable" also ofcourse.

Problem: system is very unstable, sometimes to low and sometimes to high output. i have feeling that, when the PI- reach a null difference (setpoint=
process value) - then he starts again and not holding 0 - difference. K = 25 and Ti = 100 (i have tryed with 1000000, and 10, but nothing helps)

am i doing something really wrong?


thanx in advance

vedran


P.S.: Samples 100, Frequency 33Hz

[Brian_Beal]

Could you post your VI here? If there isn't anything wrong with your structure, then it is just a matter of tuning. Try the autotuning function. It has worked for me in the past. If you want to tune manually, start with just P, then add small amounts of I. By small, it could even be something like 0.020. It is hard to give advice without actually seeing the process.

[vedran]

Ok, there is it:

[Jochen]

This thread is a duplicate of this one in the LabVIEW forum.