On iterative feedback tuning for non-minimum phase plants

The Iterative Feedback Tuning (IFT) is a data-based method for the tuning of restricted-complexity con-trollers. In the classical formulation, the IFT aims at minimizing a certain model-reference criterion in which the reference-model is chosen by the user. This minimization is based on signal information only. In this paper we formulate a new criterion for the IFT method. In the new criterion some freedom is given to the reference-model in order to let it reproduce the features of the unknown plant (i.e. the delay and non-minimum phase zeros) which the controller should not attempt to change. It is shown that using the new criterion corresponds to giving more emphasis to the placement of the closed loop poles.