Root Crack Identification of Sun Gear in Planetary Gear System Combining Fault Dynamics with VMD Algorithm

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%.

Fault diagnosis of tooth surface spalling based on variational mode decomposition and maximum correlation kurtosis method

“…Figure 5 shows the change curve of the output centre frequency. The SSA optimises VMD convergence in the 13th generation, and the best parameter combination is [2141,10]. According to the optimisation results, the penalty factor size for the VMD parameters is set to 2141 and number of components is set to 10.…”

“…x y x y , , , , , 9 x , p x g displacement in the horizontal direction of the main and slave driving wheels; y , p y g is vertical displacement; , p q g q is the angle of the gear shaft. According to Newton's second law, the gear dynamics equation considering the influence of time-varying meshing stiffness, friction force, tooth clearance and other factors is derived, and its expression is shown as equation (10). The meanings of parameters in the figure 2 are listed in table 1.…”

“…Sharma et al [9] studied the extraction of weak fault features under variable speed conditions based on VMD. Fan et al [10] proposed a solar gear root-crack identification method for planetary gear systems by combining the fault dynamics with a VMD algorithm. In addition, Miao et al [11] proposed a new decomposition theory called FMD for mechanical fault feature extraction.…”

Gear fault detection method based on improved PSO and LSTM

“…Many scholars have applied LSTM to fault detection field and produced good results. For example, Fan Jiawei et al input the gear fault feature enhancement into the LSTM model for diagnosis [2] .…”

Iterative singular value decomposition-based in-band denoising approach with envelope order analysis for sun gear fault diagnosis of planetary system under varying speed

“…Meantime, the background noise will seriously mask the fault information, especially when the sensor is not installed near the faulty gear. 1 Therefore, to effectively extract the fault features from the measured signals at varying speed has attracted much attention. 2 In recent years, many methods have been proposed to solve the above problem.…”