Designing. a PID controller to. Regulate Liquid. level

Designing a PID controller
to Regulate Liquid level of a
Liquid Tank

Description
Tuning the gain of Proportional-Integral-Derivative
(PID) controller in a process control system is
exceptionally paramount
Correct tuning would help a control process
response without steady state error and overshoot.
Conventional gain tuning of PID controller
includes,
1. Ziegler-Nichols method
2. Cohen-Coon method

ZN tuning
Increase the gain by initially setting the plant
with the small gain till the oscillation starts to
occur.
ZN method is based on the frequency
response. The controller output is detected
by the linear oscillation.
This process utilizes two methods:
1. process reaction-curve method
2. Ultimate cycling method

Step response

Nyquist plot
 Kc = Gm = 10^ (18.1 / 20) = 8.03
 Pu = 2π / ωc = 2π / 0.173 = 36.300 sec.
The parameters are obtained for the ZN tuning method

Step response for each controller
Critical gain = 8