2 research outputs found
The analysis of nonlinear systems in the frequency domain using Nonlinear Output Frequency Response Functions
The Nonlinear Output Frequency Response Functions (NOFRFs) are a concept which provides a new extension of the
well-known concept of the Frequency Response Function (FRF) of linear systems to the nonlinear case. The present study
introduces a NOFRFs based approach for the analysis of nonlinear systems in the frequency domain. It is well known that a
nonlinear system can, under rather general conditions, be represented by a polynomial type Nonlinear Auto Regressive with
eXogenous input (NARX) model. From the NARX model of a nonlinear system under study, the NOFRFs based approach
for the frequency analysis of nonlinear systems involves solving a set of linear difference equations known as the
Associated Linear Equations (ALEs) to determine the system nonlinear output responses and then the NOFRFs of the
system up to an arbitrary order of nonlinearity of interests. The results enable a representation of the frequency domain
characteristics of nonlinear systems by means of a series of Bode diagram like plots that can be used for nonlinear system
frequency analyses for various purposes including, for example, condition monitoring, fault diagnosis, and nonlinear modal
analysis