INTERPOLATION APPROACH TO HANKEL-NORM MODEL-REDUCTION FOR RATIONAL MULTIINPUT MULTIOUTPUT SYSTEMS

Hankel-norm model degree reduction problem is studied by the interpola tion approach. All-pass matrices that satisfy directional interpolatio n requirements are applied to this problem. Multi-input multi-output s ystems with rational transfer function are considered, for which a par ametrization of all approximations is derived for a specified value of the Hankel norm of the modeling error. The parametrization is express ed by only the pole locations, their directions, and the relevant dire ctions, which are all determined by a coprime factorization of the tra nsfer function matrix of the original system.