Rotating blades are functional components in aero-engines. Due to harsh working conditions, blades are prone to failure. Monitoring blade condition is urgently required to ensure safety. Blade tip timing (BTT) is a promising vibration measurement technique for rotating blades owing to its non-contact and efficiency. However, its inherent undersampling hinders the subsequent parameter identification for condition monitoring and fault diagnosis. In this paper, we proposed a single-probe BTT method based on sampling aliasing frequency (SAFE) distribution, which minimizes hardware requirements. Unlike traditional time-frequency (TF) distribution, SAFE distribution presents the relation between sampling frequency and aliasing frequency. We revealed that the parameters including engine order (EO) and natural frequency to be identified are equal to the slope and intercept of the line in SAFE distribution. To construct SAFE distribution, the traditional TF methods were extended by introducing adaptive window-length/scale related to sampling frequency. Simulation and experiment verify the effectiveness of the proposed method.

blade tip timing;extended time-frequency analysis;sampling aliasing frequency;parameter identification