Multivariable VRFT: an approach for systems with non-minimum phase transmission zeros

In this paper we discuss an approach for the Virtual Reference Feedback Tuning (VRFT) for multivariable systems with non-minimum phase transmission zeros. We also present some possible choices for the reference model which satisfy the internal stability constraint. It is shown that with the addition of all-pass filters in the cost function one can find the optimal controller parameters without altering the cost function minimum and avoiding dealing with an unstable filter - which are two major limitations of the current multivariable VRFT approaches. Simulation examples show the applicability of the proposed formulation.