CONSTRAINED OPTIMAL PADE MODEL-REDUCTION

A frequency-domain multipoint Pade approximation method is given that produces optimal reduced order models, in the least integral square er ror-sense, which are constrained to match the initial rime response va lues of the full and reduced systems for impulse or step inputs. It is seen to overcome a perceived drawback of the unconstrained optimal mo dels, i.e., that they do not guarantee a proper rational reduced order transfer function for a step input. The method is easy to implement w hen compared to existing constrained optimal methods, and consists of solving only linear sets of equations in an iterative process. It is a lso seen to be a natural extension of an existing optimal method. Nume rical examples are given to illustrate its application.