Stable partial Padé approximations for reduced-order trnsfer functions

While the Padé approximation can often be used to produce good reduced-order transfer functions, the method suffers from the disadvantage that a stable reduced order-model is not always obtained for an original model that is stable. A method is described for obtaining stable partial Padé approximation reduced-order models. The method permits the determination of the effect of changes in the coefficients in the partial Padé approximation on the poles of the reduced-order transfer function by means of standard root locus plots.