Pade and Routh approximation in the time domain

A simple procedure is presented for obtaining reduced-order models for single-input-single-output systems which does not require the calculation of the eigenvalues and eigenvectors of the system matrix. Furthermore, the stability of the reduced-order model is guaranteed if the original system is stable. The procedure presented is a time-domain adaptation of Pad?? and Routh approximation methods, and does not transform the system equations to the frequency domain, Pad?? and Routh approximation methods. A numerical example is included.