Full-field mode shape estimation of a rotating structure subject to random excitation using a tracking continuously scanning laser Doppler vibrometer via a two-dimensional scan scheme

• Published in: Mechanical systems and signal processing Vol. 169; p. 108532
• Main Authors: Lyu, L.F., Zhu, W.D.
• Format: Journal Article
• Language: English
• Published: Berlin Elsevier Ltd 15.04.2022; Elsevier BV
• Subjects: Demodulation; Fast Fourier transformations; Fourier transforms; Improved demodulation method; Laser doppler vibrometers; Lasers; Modal analysis; Nonuniform rotating plate model; Operational modal analysis; Random excitation; Resonant frequencies; Rotation; Scanning; Tracking; Tracking continuously scanning laser Doppler vibrometer system; Two-dimensional scan scheme; Improved demodulation method; Two-dimensional scan scheme; Tracking continuously scanning laser Doppler vibrometer system; Random excitation; Operational modal analysis; Nonuniform rotating plate model
• DOI: 10.1016/j.ymssp.2021.108532
• ISSN: 0888-3270

•A nonuniform rotating plate model is developed for its operational modal analysis.•A two-dimensional scan scheme is developed for full-field measurement.•A tracking continuous scanning laser Doppler vibrometer system is developed.•A demodulation method is used for processing measurement of a rotating structure.•Full-field mode shapes of a rotating fan blade with constant speeds were estimated. A two-dimensional (2D) scan scheme is developed for a tracking continuously scanning laser Doppler vibrometer (CSLDV) system to scan the whole surface of a rotating structure subject to random excitation. A tracking CSLDV system is developed to track a rotating structure and sweep its laser spot on its surface. The measured response of the structure using the 2D scan scheme of the tracking CSLDV system is considered as the response of the whole surface of the structure subject to random excitation. The measured response can be processed by an operational modal analysis (OMA) method called the improved demodulation method based on a rigorous nonuniform rotating plate model to obtain modal parameters of the rotating structure, such as damped natural frequencies and undamped full-field mode shapes. Damped natural frequencies of the rotating structure are estimated from the fast Fourier transform of the measured response. Undamped full-field mode shapes are estimated by multiplying the measured response by sinusoids whose frequencies are estimated damped natural frequencies. Experimental investigation of the 2D scan scheme of the tracking CSLDV system and OMA method is conducted, and damped natural frequencies and undamped full-field mode shapes of a rotating fan blade with different constant speeds are estimated. It is theoretically and experimentally shown that damped natural frequencies of the rotating fan blade increases with its rotation speed.