Balanced truncation preserving poles in a specified disk

In this paper, a model reduction method for linear time invariant stable system whose poles locate in a specified disk on the complex left half plane is considered. In this reduction method the domain in which the poles of the original system locate is preserved. This method is based on the balanced truncation technique that is often used for reducing high order stable system by a low order stable one. A lot of properties of the balanced truncation technique are maintained. Furthermore, the error bound is evaluated using Hankel singular values of the original system.