An LQG/LTR control system design is formulated for a feedwater heater train with output time delay. This approach involves factoring the feedwater healer train plant into nonniinimum and minimum phase components to allow the design of a robust controller lor the minimum phase component of the plant using the LQG/LTR technique (minimum phase method). The nonminimum phase component lakes ihe form of an allpass Tiller containing the rhp zeroes of the first-order approximation of the lime delay

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... onent. Using (his nonmimmum phase all-pass filler, certain singular-value multiplicative error bounds can be established to obtain a stable control system when using the LQG/LTR design technique on the minimum phase component of the plant. New analysis methods using singular values are integrated into ihc conventional singular-value performance and stability robustness analysis procedure. These new analysis methods allow computation of the maximum allowable lime delay before instability occurs for both SISO and M1MO control systems.