Design of optimal output disturbance cancellation controllers for non-minimum phase plants via loop transfer recovery

The authors have recently shown that, despite the lack of the stabilizability of the extended plant, the standard loop transfer recovery (LTR) procedure can be used for the design of output disturbance cancellation controllers under the minimum phase assumption on plants. Application of the LTR technique to non-minimum phase plants is discussed in this paper. It is shown that, although the perfect recovery is impossible, the standard LTR procedure is useful for a class of non-minimum phase plants.