The Ziegler-Nichols open-loop tuning method allows you to use the delay time L and the time constant to calculate the gain, integral time, and derivative time. The transfer function of a PID controller is:
Es
Based on this method, we have the following transfer function of a PID controller:
G (PID) = 25 [4 + {1/x.s} + 2s]
(2)
Table 10-1
Ziegler-Nichols Tuning Rule Based on Step Response of Plant (First Method)
Type of Controller
Kp 2N 0.9 T L 1.2 T L
Ti
Ta
P
8
0
PI
L 0.3
0
PID
2L
0.5L
1) Use the table to find the values of T and L.
2) Find the transfer functions of the P and PI controllers.
3) Find the value of x in the given equation (2).