Linear model reduction using Hurwitz polynomial approximation

A new approach to stable reduced-order linear model construction is given, based on the concept of Hurwitz polynomial approximation. Pade approximants to the tangent function of a given large-degree Hurwitz polynomial are constructed, such that the corresponding low-degree polynomials are also Hurwitz. We prove a theorem to that effect and give methods for obtaining the reduced Hurwitz polynomials. Model reduction is achieved by first invoking this theorem and completing the reduction using the Pade equations. Two examples are given.