Early Fault Diagnosis for Planetary Gearbox Based Wavelet Packet Energy and Modulation Signal Bispectrum Analysis

Abstract

The planetary gearbox is at the heart of most rotating machinery. The premature failure and subsequent downtime of a planetary gearbox not only seriously affects the reliability and safety of the entire rotating machinery but also results in severe accidents and economic losses in industrial applications. It is an important and challenging task to accurately detect failures in a planetary gearbox at an early stage to ensure the safety and reliability of the mechanical transmission system. In this paper, a novel method based on wavelet packet energy (WPE) and modulation signal bispectrum (MSB) analysis is proposed for planetary gearbox early fault diagnostics. First, the vibration signal is decomposed into different time-frequency subspaces using wavelet packet decomposition (WPD). The WPE is calculated in each time-frequency subspace. Secondly, the relatively high energy vectors are selected from a WPE matrix to obtain a reconstructed signal. The reconstructed signal is then subjected to MSB analysis to obtain the fault characteristic frequency for fault diagnosis of the planetary gearbox. The validity of the proposed method is carried out through analyzing the vibration signals of the test planetary gearbox in two fault cases. One fault is a chipped sun gear tooth and the other is an inner-race fault in the planet gear bearing. The results show that the proposed method is feasible and effective for early fault diagnosis in planetary gearboxes.

Gear Wear Process Monitoring Using a Sideband Estimator Based on Modulation Signal Bispectrum

“…To suppress noise and extract the fault-related sidebands accurately, MSB method is used in this study. According to the definition of MSB in the frequency domain, for gear vibration signal x(t) with corresponding Fourier transform (FT) X(f ), the MSB-SE can be defined in the frequency domain as [17][18][19].…”

“…Bispectrum analysis is a useful signal processing tool that has shown significant benefits over traditional spectral analyses due to its unique properties of nonlinear system identification, Gaussian noise elimination, and phase information retention [14][15][16][17][18][19][20][21]. Conventional bispectrum (CB) was applied to vibration signals for the detection of different degrees of tooth breakage of a two-stage helical gearbox and tooth crack [15].…”

“…The results showed reliable fault diagnosis and revealed that random noise can be suppressed effectively, being much better than that of the power spectrum (PS) and CB for diagnosing different seeded faults, such as tooth breakage and shaft misalignment [16]. MSB-SE-an extension of MSB analysis-was developed recently, and is used to achieve a simple representation for the complicated signal contents [17], which allows the small sidebands be estimated with a good degree of accuracy and hence produce more accurate and consistent diagnostic results [17][18][19][20]. Inspired by the works presented in [17,19], where MSB was successfully used for identifying both the presence and magnitude of the seeded faults, MSB method would be used to evaluate the natural gear wear monitoring and severity assessment-although it may be more challenging, as the wear process may induce vibration signature changes far weaker than tooth breakages.…”

Planetary gearbox fault diagnosis using an on-rotor MEMS accelerometer

“… Resample the sensors' data based on the frames. Many studies have shown that any type of fault in the planetary gearbox will lead to the development of mechanical vibrations, and by examining the changes in characteristic frequency spectrum around the mesh frequency and its harmonics, these faults can be detected and diagnosed [3]. Assuming that K is the number of planetary gears that are moving within the carrier, the characteristic vibration frequencies around the meshing frequency are unique for each type of planetary gearbox fault, as identified by [4].…”

“…Since the applications of planetary gearboxes are quite critical and their failure may cause shutdown of the entire train resulting in major economic losses, condition monitoring of planetary gearboxes has received significant attention from many researchers. To avoid any unexpected interruptions and accidents that might be caused by planetary gearbox failure [3,4]. , many studies have recently been carried out into the development of planetary gearbox condition monitoring and fault diagnosis.…”