Identification and Instantaneous Frequency Estimation of Effective Vibration Signal for Pitch Gearbox

This article focuses on the little-studied pitch gearbox (PG). Due to the intermittent operation of the PG, there are currently no suitable methods for automatically identifying the effective vibration signal. The variable speed operation of the PG causes the amplitude of the effective vibration signal (EVS) to attenuate, rendering current instantaneous frequency (IF) estimation methods ineffective. To address these issues, the amplitude and frequency characteristics of each component in the vibration signal of the PG are analyzed. Then, a method for identifying the EVS is proposed, which combines high-pass filtering and moving median filtering (MMF). High-pass filtering removes low-frequency components. MMF removes broadband high-amplitude components. Finally, a method for estimating the IF of effective vibration signals based on the short-time fractional Fourier transform (STFrFT) is proposed. This method is accurate and not sensitive to amplitude. The experimental results show that the proposed method is superior to comparison methods in the accuracy of identification and estimation. Therefore, the proposed method lays a foundation for the monitoring and diagnosis of the PG.