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Construction of reduced order models using the conventional quasi-steady-state (QSS) or singular perturbation approach may not yield good low frequency approximations, especially if there is not a distinct time scale separation into slow and fast subsystems. An implicit QSS technique is proposed for general nonlinear models. The resulting reduced order model is accurate to first order in the perturbation parameter and its linearization is accurate to first order in frequency. An example is included showing the application of the proposed method to model reduction on a power plant evaporator. [DOI: 10.1115/1.2397153] Keywords: implicit quasi-steady state, model reduction, stiff systems, singular perturbation, power plant boiler, once through steam generator

An algorithm for calculating design bounds in multivariable quantitative feedback theory (QFT) tracking design is presented. The algorithm solves the problem of trade-off between on- and off-diagonal constraints.

The Perron-Frobenius root is used to measure the level of interaction in MIMO quantitative feedback design (QFT). A design approach to reduce interaction in uncertain plants via a precompensator is presented. A decentralized stability result applies if the interaction index can be made less than unity by design. [DOI: 10.1115/1.1343463]

To reduce the computational overhead in quantitative feedback theory (QFT) bound computation, only the (nonconvex) outside edge of a template should be used. This note presents an algorithm to calculate the nonconvex hull with minimum concave radius defined by the system specifications. [S0022-0434(00)01301-0]