Identification of linear subsystem for simple block-oriented nonlinear systems working in closed-loop — Higher order spectra approach

In the paper a strategy for discrete-time model identification of linear dynamic subsystem in simple block-oriented nonlinear systems operating under feedback is presented. In the proposed procedure a discrete-time frequency response of this linear part is identified using integrated bispectra or trispectra. Based on the identified frequency response the corresponding rational parametric approximation is calculated. The nonlinear system is excited by higher-order non-gaussian multisine excitation during identification experiment designed in a special way. The discussion included in the paper is illustrated by simulation examples demonstrating properties and effectiveness of the given approach.