An Autocorrelation Method for Asynchronous Vibration Feature Extraction in Blade Tip Timing

Engine compressor blades play important roles in aeroengine operation. They are easily injured by foreign objects due to direct contact with the outside air. Blade tip timing (BTT) is a non-contacting vibration measurement method for rotating blade health monitoring. However, the under sampled problem is an inevitable obstacle in the feature extraction of BTT signal. An alternative feature extraction method called autocorrelation method for asynchronous vibration analysis is proposed in this paper to identify the vibration amplitude and frequency of the under sampled BTT signal simultaneously. Based on the assumption of single frequency vibration, the signals collected by three probes are used to form two equations, and the vibration frequency and amplitude are obtained by solving them. Additionally, the discussion on the probe layout required by the proposed method is conducted. The verification using simulation signal (the noised signal with one frequency component) and experimental signal (signal collected under constant rotating speed) shows that the amplitude and frequency can be accurately extracted by the proposed method.