Glossary · Control theory and process control
Ziegler–Nichols method
Also known as: Ziegler–Nichols tuning, Ziegler–Nichols rules
German: Ziegler-Nichols-Verfahren
In control engineering, the Ziegler–Nichols method is a set of empirical PID tuning rules published by Ziegler and Nichols in 1942, which derive controller parameters either from the ultimate gain and oscillation period of a loop or from the parameters of a step response.
- Control theory
In one sentence
The Ziegler–Nichols method derives PID parameters from the ultimate gain and period of a loop or from its step response.
Example
With the loop in P-only mode, the technician raises the gain until sustained oscillation appears at a gain of 4 and a period of 20 s, then calculates PI parameters from the Ziegler–Nichols table.
How it applies
- Commissioning: The closed-loop variant drives the loop to the edge of stability, which many processes can't tolerate. The open-loop (step response) variant is gentler. Relay auto-tuning finds the ultimate gain and period without pushing the loop to sustained oscillation by increasing gain.
- Engineering: Ziegler–Nichols settings aim at fast disturbance rejection and typically give aggressive, oscillatory responses. They are a starting point; many practitioners use more conservative rules afterward.
- Documentation: If the method is named in a commissioning procedure, include the safety preconditions for the test and the step of reviewing and softening the resulting parameters.
Ziegler–Nichols vs. auto-tuning
Ziegler–Nichols is a manual procedure with a table. Auto-tuning automates the test and calculation, and many auto-tuners use Ziegler–Nichols-type rules internally.