Figure 5. Response Curve for Ziegler-Nichols Method.
For instance, if the step response of the plant model can be measured through an experiment, the output signal can be recorded as sketched in Fig. 5, from which the parameters of k, L, and T (or a, where a = kL/T ) can be extracted by the simple approach shown. More sophisticated curve fitting approaches can also be used. With L and a, the Ziegler– Nichols formula in Table 1 can be used to get the controller parameters.