Ziegler Nichols Tuning

For Ziegler Nichols Tuning, we use the step response of the open loop experiment.

Figure 9.2: Tangent approach to Ziegler Nichols Tuning

Table 9.1: Ziegler Nichols PID Settings

	$K_c$	$\tau _i$	$\tau _d$
P	1/RL
PI	0.9/RL	3L
PID	1.2/RL	2L	.5L

Table 9.1 gives the PID settings. In this approach too, for every open step test, K and $\tau$ are found and correlated as function of average temperature and PID settings are then found as functions of temperature.
Note: For a first order transfer function we assume

• $K_p$ $\approx$ K
• $\tau _p$ $\approx$ $\tau$