GE PACSystems RX7i

Chapter 7. PID Built-In Function Block
GFK-2950C February 2018 361
7.6.2 Setting Loop Gains Using the Ziegler and Nichols Tuning
Approach
This approach provides good response to system disturbances with gains producing an amplitude
ratio of 1/4. The amplitude ratio is the ratio of the second peak over the first peak in the closed loop
response.
1. Determine the three process model parameters, K, T
p
and T
c
for use in estimating initial PID loop
gains.
2. Calculate the Reaction rate:
R = K/T
c
3. For Proportional control only, calculate Kp as:
Kp = 1/(R * T
p
) = T
c
/(K * T
p
)
For Proportional and Integral control, use:
Kp = 0.9/(R * T
p
) = 0.9 * T
c
/(K * T
p
) Ki = 0.3 * Kp/T
p
For Proportional, Integral and Derivative control, use:
Kp = G/(R * T
p
) where G is from 1.2 to 2.0
Ki = 0.5 * Kp/T
p
Kd = 0.5 * Kp * T
p
4. Check that the Sample Period is in the range
(T
p
+ T
c
)/10 to (T
p
+ T
c
)/1000