Abstract
For discrete-time non-minimum phase plants with feedback delays, we discuss two Loop Transfer Recovery (LTR) techniques applied at the plant output side. We show that the feedback property achieved by the formal application of the conventional LTR procedure can be achieved by the partial LTR technique which has a clear system-theoretic significance. By this fact, we can justify the use of the conventional LTR technique to a class of non-minimum phase plants. In addition, we point out that the partial LTR technique provides more freedom in shaping a target feedback property via the selection of disturbance model. We propose a simple technique exploiting this freedom. By a numerical example, we show that the proposed technique can be used to enhance robustness against uncertainties near a Nyquist frequency without significant change in low frequency characteristics.
