EXACT NONLINEAR MODELLING USING SYMBOLIC LINEAR FRACTIONAL TRANSFORMATIONS

In this paper, a nonlinear modelling framework is presented that combines symbolic modelling and linear fractional transformation (LFT) techniques to obtain a nonlinear symbolic LFT representation. This modelling approach presents three clear advantages: (i) it provides a unifying framework for the different models that stem from the same nonlinear system, (ii) it allows for a highly structured representation of the various nonlinearities present in the system, and (iii) it is closely connected with other analysis and synthesis frameworks such as linear and linear parameter varying robust control and nonlinear systems analysis via describing functions.