This document discusses two methods for PID tuning using the Ziegler-Nichols method: the step input or open loop method and the critical gain-critical period or closed loop method. The step input method analyzes the response of a plant to a step input to determine delay time and time constant. These values are then used to calculate PID parameters according to Ziegler-Nichols formulas. The critical gain-critical period method increases the proportional gain with the integral and derivative terms set to zero until sustained oscillations occur, allowing determination of critical gain and period to again calculate PID parameters.

1. PID Tuning using Ziegler-Nichols
Method
Subject – Control System
Kaustubha H. Shedbalkar
8/16/2023 PID Tuning using Z- N method

2. Ziegler Nicholas Methods -
 Step Input method/ Open loop method.
 Critical gain - critical period method/ Close
loop method.
8/16/2023 PID Tuning using Z- N method

3. Step Input method/ Open loop
method
8/16/2023 PID Tuning using Z- N method

4. Step Input method/ Open loop
method
8/16/2023 PID Tuning using Z- N method

5. • In this method, we obtain experimentally the
response of the plant as shown in fig. This method
applies if the response to a step input exhibits an
S-Shaped curve.
• The S-Shaped curve may be characterized by two
constants, Delay time (L) & Time constant (T). It is
determined by drawing a tangent line at the
inflection point of S-Shaped curve & determining
the intersection of tangent line with time axis &
line K on Y-axis. The Ziegler-Nichols suggested, we
set the value of parameter Kp, Ti, Td according to
the formula shown in table.
8/16/2023 PID Tuning using Z- N method

6. Step Input method/ Open loop
method
8/16/2023 PID Tuning using Z- N method

7. Critical gain - critical period method/
Close loop method
8/16/2023 PID Tuning using Z- N method

8. Critical gain - critical period method/
Close loop method
8/16/2023 PID Tuning using Z- N method

9. 8/16/2023 PID Tuning using Z- N method
• In this method, suppose PID controller is used in
the system then Ti is set to infinity & Td is set to
zero. Using proportional control action only,
increase Kp from zero to critical value Kcr at which
the output first exhibits sustained oscillations.
• The critical gain Kcr & corresponding time period
Pcr are determined.
•The Ziegler-Nichols suggested, we set the value of
parameter Kp, Ti, Td according to the formula
shown in table.

10. Critical gain - critical period method/
Close loop method
8/16/2023 PID Tuning using Z- N method

11. Thank You.
8/16/2023 PID Tuning using Z- N method