Closed-loop frequency-based identification method for Hammerstein type plants with a transport delay using a relay feedback

This paper proposes a new closed-loop frequency based method for parametric identification of Hammerstein type plants with a transport delay. The method is a generalization of Ziegler Nichols´ (ZN) experiment, with relay added in the control loop. It provides a simultaneous estimation of the parametric model of the plant dynamic, value of the time delay and a point by point relationship between input and output of the nonlinear part of the plant, which need not to be symmetrical. No extra equipment is needed, except the relay and a low pass filter.