Loop Transfer Recovery Techniques for Time-Delay Systems with Non-Minimum Phase Lumped Part

Abstract

For a plant consisting of a lumped non-minimum phase part and an output delay, we discuss LTR (Loop Transfer Recovery) techniques for designing a predictor-based LQG controller. We focus our attention to the feedback property achieved at the plant output side. We show that a feedback property recovered by the formal application of the conventional LTR procedure can be achieved by the partial LTR technique which has a clear system-theoretic meaning. This fact provides a theoretical justification of the formal application of the conventional LTR technique to a plant including finite unstable zeros and a time delay. In addition, we point out that the partial LTR technique provides more freedom in shaping target feedback properties. We propose a simple technique exploiting this freedom. A numerical example is given to illustrate usefulness of the proposed technique.