Application of Time Descriptors to the Modified Hilbert Transform of Empirical Mode Decomposition for Early Detection of Gear Defects

Abstract

Diagnosis and fault detection in mechanical systems during their time-varying non stationary operation is one of the most challenging tasks. The paper presents a method for the early detection of gearbox defects based on the empirical mode decomposition (EMD) algorithm and a proposed modified Hilbert transform. The EMD technique decomposes the measured signal into oscillatory functions called Intrinsic Mode Functions (IMF). A numerical model of damaged gears is used for generating a modulated vibratory signal with repetitive shocks. The application of time descriptors "Talaf" and "Thikat" to different IMF decomposition levels of the modified Hilbert envelope gives good results for early detection of defects in comparison with the IMF of the original time signal and its traditional Hilbert envelope or with the wavelet decomposition.