An Overview of System Modelling in LFT Form

Abstract

This paper presents an overview of system modelling in LFT (Linear Fractional Transformation) form. An LFT form serves often to replace a bank of linearized models by a continuum of linear models to be employed to solve parametric analysis and design problems. In other cases, LFT models are special multidimensional realizations of parametric rational matrices. We discuss several approaches to generate LFT models, addressing both exact as well as approximate generation of LFT models. Many of existing generation methods tend to produce large order LFT realizations which are difficult to be handled when solving analysis and design problems. Therefore, a main focus of our presentation is on obtaining low order LFT models, by using both exact as well as approximate LFT models reduction techniques.