On an initial condition for a reduced-order model using a two-step iterative method

A two-step iterative algorithm we have proposed gives good approximation in the sense of an integral square-error of time response between an original system and a reduced-order model. A reduced-order model using the two-step iterative algorithm is affected by an initial condition. In this paper the reduced-order model using a denominator array expansion method is used the initial step reduced-order model in the two-step iterative algorithm. It is found that the resulting reduced-order model gives good approximation compared with other methods in the sense of integral square-error.