Identification of rotating structures using autoresonance

Autoresonance (AR), a self-excitation technique which automatically excites systems at their natural frequencies, can be used as a quick and efficient method for modal testing of rotating structures. Such structures are characterized by speed-dependent eigenfrequencies and mode-shapes, due to the gyroscopic effect, and hence require a modal testing method with speed-tracking ability - such as AR. while the ability to identify the branches of the Campbell diagram was demonstrated in a previous work, it failed to distinguish between the forward and backward modes of the lower frequency modes, which are highly affected by the stiffness anisotropy of the bearings. The paper presents a method for modal identification of rotating structures supported by anisotropic bearings. The method not only detects the branches of the Campbell diagram, but also identifies the mode shapes and damping ratios. The analytical model is verified by numerical simulations.