Model reduction by low frequency approximation of internally balanced representation

A modified balancing model-reduction method is proposed for frequency domain robust control system design. The reduced-order model is obtained by approximating the states of the weak subsystem of the balanced representation around zero frequency. Several properties and error bounds of the reduced model are derived. A critical comparison is made with B.C. Moore's (1981) reduced-order model obtained by direct truncation. A numerical example is included.<>