Qualitative Analysis of Stable Reduced Order Models for Interval Systems Using Mixed Methods

摘要

A large number of problems are available for complex higher order systems. These systems are difficult to analyze and synthesize. Therefore it is needful to approximate higher order models to lower order models. Interval systems have constant coefficients which are uncertain within a finite range. In this paper, the frequency domain reduction methods are applied for reducing the order of interval systems. The three mixed methods are considered for reducing the linear dynamic interval systems. In these mixed methods, denominators of the reduced models are obtained by using differentiation method while the numerators of the reduced models are obtained by using differentiation, factor division, and pade approximation methods. The novel feature of the proposed methods is that it guarantees the stability of reduced order models if the original interval systems are stable. In addition, the mixed methods are compared qualitatively in terms of integral square error and integral absolute error to know about the best method among three mixed methods. Numerical examples are given to show the effectiveness of the mixed methods.