Identification of non-linear dynamics using higher order frequency response functions

An experiment is designed to identify input-output relations of a mechanical positioning system with excitation amplitude dependent mechanical behavior. When evaluated in the frequency domain, these relations constitute a fingerprint of the dynamical behavior of the system. Since the commonly used FFT based techniques for Frequency Response Function (FRF) estimations require stationary signals, an alternative technique is introduced. With a digital filtering based technique fixed frequency higher order can be estimated as function of time dependent excitation levels. The paper describes the data processing techniques and shows measurement results of the higher order FRFs of a system with strong amplitude dependent mechanical behavior caused by a friction induced resonance.