Abstract
Planetary gearbox is widely used in various low-speed machines due to its large transmission ratio. However, the gears in a planetary gearbox are prone to the mechanical faults due to the complex dynamic heavy load. Vibration frequencies caused by an early tooth root crack of sun gear are usually difficult to accurately extract, so its fault diagnosis is one of the main challenges of planetary gearbox reliability. In this paper, a simplified tooth root crack model of sun gear is proposed, and then a rigid-flexible coupled dynamics model of the whole planetary gear system is constructed. By the numerical simulation, the fault frequencies caused by a tooth root crack of sun gear are obtained. A Variational Mode Decomposition (VMD) algorithm for the vibration frequency extraction is proposed. The measured vibration signals are decomposed into the sparse Intrinsic Mode Functions (IMFs) by the VMD, and then the IMFs are further analyzed by the spectral method to accurately extract the crack-induced frequency components. The experimental results show that the proposed dynamics model and VMD method are feasible; an error between the characteristic frequencies from the tested signal analysis and the theoretical calculation is less than 1%.
Highlights
Because of large transmission ratio and compact structure, the planetary gearbox is widely used in various low-speed heavy machines
Based on the tooth crack model, a whole dynamics model of planetary gear system can be built. ere are three kinds of dynamics model of planetary gear system: lumped parameter model [9, 10], finite element model [11], and rigid-flexible coupled model [12,13]. e lumped parameter model of a planetary gearbox was established, and the influence of the installation error of planet carrier on the vibration response was studied by Zhai et al [14]
Li and Zhu [34] applied the Variational Mode Decomposition (VMD) for the mechanical fault diagnosis; the results show that the VMD is better than Ensemble Empirical Mode Decomposition (EEMD) in signal decomposition effect
Summary
Because of large transmission ratio and compact structure, the planetary gearbox is widely used in various low-speed heavy machines. Ere are three kinds of dynamics model of planetary gear system: lumped parameter model [9, 10], finite element model [11], and rigid-flexible coupled model [12,13]. Liu et al [17] established a 3D finite element model of planetary gearbox and found that the effect of crack on the vibration response is mainly reflected in the frequency domain. Combined with the crack model, a rigid-flexible coupled model of planetary gear system with tooth crack of sun gear is constructed, and the dynamics simulation is designed to find the crack-induced signal frequency characteristics. In order to identify the crack from the tested vibration signals, a VMD-based signal analysis method is proposed to extract the featured frequency of tooth crack.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
