Blade Tip Timing Signal Filtering Method Based on Sampling Aliasing Frequency Map

Abstract

The rotor blade is the core turbomachinery component with high failure risk. Thus, condition monitoring of blades is critical to ensure engine safety. Blade tip timing (BTT) is one of the most promising approaches to measure vibration, which is used for monitoring the health of blades. In reality, blade displacement contains several unwanted components that cause measurement uncertainty. However, because undersampling leads to spectrum aliasing, and the aliasing frequency changes with speed fluctuation, conventional filtering techniques fail to remove the portion of the signal that causes uncertainty. In this work, two filtering methods for the BTT signal are proposed based on sampling aliasing frequency (SAFE) map, namely, single-probe data detrending and tracking sliding bandpass filtering, which can extract synchronous vibration and denoise the reserved signal (asynchronous vibration) due to the clear distribution of different components in the SAFE map. The former eliminates the rotation frequency and its harmonic components by detrending of the BTT signal, whereas the latter effectively reduces the noise of the BTT signal by bandpass filters whose limit frequencies are adjusted according to sampling frequency and the trajectory in the SAFE map. Furthermore, the time-domain signal and the spectrum obtained by the orthogonal matching pursuit (OMP) algorithm are used to show the filtering effect. The effectiveness and interpretability of the proposed method are verified by simulation and experimental data.