Detecting and Quantifying the Nonlinear and Time-Variant Effects in FRF Measurements Using Periodic Excitations

Frequency response function (FRF) measurements are very often used to get a quick insight into the dynamic behavior of complex systems; even if it is known that these systems are only approximately linear and time-invariant. Therefore, it is important to detect and quantify the deviation from the ideal linear time-invariant framework that is inherent to the concept of an FRF. This paper presents a method to detect and quantify the nonlinear and time-variant effects in FRF measurements using periodic excitations. The proposed method can handle noisy input, noisy output data, and nonlinear time-variant systems operating in feedback.