## How to tune a PID with ZN method.

### xiao (view profile)

on 10 Feb 2014

Hi, guys, I'm playing on SIMULINK recently but have come across a bit problems. To tune a PID controller using Zeiglur-Nichols Method, we need to set Ki Kd to 0 and keep changing the value of Kp(Kcu) until it starts "oscillating". My first question is what does "oscillating" mean. Cz I realize that no matter how much the Kp(Kcu) is, the shape of the scale is always oscillation.

And then, after we determine the oscillating Kcu, we use the table, Kp=0.6Kcu, tauI=Pu/2, tauD=Pu/8. My second question is what is tauI, and tauD? Do they just mean Ki and Kd? Is it OK for me just type the calculated Kp, tauI and tauD into the P,I,D controllers as the final values? Or, do I need to multiply the value of tauI and tauD by Kp, to get Ki and Kd as final ones?

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