LQG/LTR technique for discrete-time systems with time-delays

The authors consider the problem of loop-transfer recovery using prediction estimators for square minimum phase discrete-time systems with time delays. The recovered loop transfer matrix at the plant input coincides with the loop transfer matrix obtained with the optimal digital regulator having d-sample controller delays described by T. Mita (1985). Hence, the results of T. Ishihara (1988) can be used to analyze the robustness properties of the recovered control system. A procedure which is the dual of this procedure can be derived for recovery with respect to the plant output