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ZN Method

The Ziegler-Nicholas or ZN method is a technique for tuning PID controllers invented in 1942. It can be used for both open and closed loop systems. For closed loop systems, the ZN method increases the proportional gain from zero until sustained oscillations occur, then uses the critical gain Kc and oscillation period Pc to calculate the integral and derivative gains. The ZN method provides robust tuning and good disturbance rejection but can produce large gains and overshoots. It has been applied to control systems like programmable logic controllers and single tank water level control.

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92 views2 pages

ZN Method

The Ziegler-Nicholas or ZN method is a technique for tuning PID controllers invented in 1942. It can be used for both open and closed loop systems. For closed loop systems, the ZN method increases the proportional gain from zero until sustained oscillations occur, then uses the critical gain Kc and oscillation period Pc to calculate the integral and derivative gains. The ZN method provides robust tuning and good disturbance rejection but can produce large gains and overshoots. It has been applied to control systems like programmable logic controllers and single tank water level control.

Uploaded by

Vishnuboy Vishnu
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Ziegler-Nicholas Method

Description

The Ziegler-Nicholas or well known as ZN method is a method for tuning PID controllers. This method
was invented in 1942 by 2 employees of Taylor Instruments, Ziegler and Nicholas. This method can be
used for both open loop and closed loop methods. For the open loop tuning, the response parameters
are delay time, L and time constant, T. For the closed loop system, this method is designed to give an
overshoot up to 25%. The tuning steps for closed loop system are reducing the integrator and derivative
gains to 0, then increase the Kp value from 0 to some critical value Kp=Kcr at which sustained oscillations
happens. If no, another method should be carried out. Lastly, note the K cr value and corresponding
period of sustained oscillation, Pcr. The control parameters for both open and closed loop system are
shown in table 1 and 2 respectively.[1]

Table 1 : Z-N method for open loop system Table 2 : Z-N method for closed loop system

Advantage & Disadvantage

Advantage[2] Disadvantage[3]
More robust method Produce bigger value of gain and overshoot
Best disturbance rejection Not suitable for all applications because it only
works for closed systems with sustained
oscillations.
Suitable for plants that rendered unstable under Dependence on non-reality because to obtain a
proportional control. good tuning, it depends completely on
proportional measurement to estimate I and D
controllers.
Quick and straight forward method Approximations for the Kc, Ti, and Td values might
not be entirely accurate for different systems.

Application

 Used in microcontrollers based systems such as programmable logic controllers[4]


 Used in single tank water level dynamic control system[5]
Reference

[1] B. Copeland, “The Design of PID Controllers using Ziegler Nichols Tuning,” Retrieved, March, no.
March, pp. 1–4, 2008, [Online]. Available:
http://educypedia.karadimov.info/library/Ziegler_Nichols.pdf.
[2] J. Bennet, A. Bhasin, J. Grant, and W. C. Lim, “PIDTuningClassical - ControlsWiki,” University of
Michigan, 2007.
https://web.archive.org/web/20080616062648/http://controls.engin.umich.edu:80/wiki/index.p
hp/PIDTuningClassical#Ziegler-Nichols_Method (accessed Oct. 22, 2020).
[3] D. Acquisition et al., “Ziegler-Nichols Tuning Rules for PID,” TechTeach, no. July, pp. 10–13, 2016,
Accessed: Oct. 22, 2020. [Online]. Available: http://www.mstarlabs.com/control/znrule.html.
[4] T. Yucelen, O. Kayma, and S. Kur, “Self Tuning PID Controller Using Ziegler Nichols Method for Pr
ogr ammable Logic Controller s.”
[5] Z. L. Edaris and S. Abdul-Rahman, “Performance comparison of PID tuning by using Ziegler-
Nichols and Particle Swarm Optimization approaches in a water control system,” J. Inf. Commun.
Technol., vol. 15, no. 1, pp. 203–224, 2016, doi: 10.32890/jict2016.15.1.10.

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