The transient vibration signals generated by the valve switch, pump start and stop operation of the complex hydraulic pipeline system are nonlinear, non-stationary, complex and high-noise, thus, the signal analysis and feature extraction encounter some difficulties. To address this problem, this article introduces a denoising method based on the parameter-optimized variational mode decomposition (VMD) method and the improved wavelet threshold (IWT). Firstly, the transient vibration signal was decomposed into multiple intrinsic modal functions (IMFs) by using the VMD after the optimized parameters of the improved grey wolf optimization algorithm (IGWO). The denoised signal was reconstructed by the effective IMFs denoised by the IWT, which were selected according to the selection principle of the effective IMF component. The results of the example verification showed that the denoising performance of the proposed method was significantly improved compared with the denoising methods such as denoising based on VMD and correlation coefficient, joint denoising based on VMD and wavelet soft threshold (VMD-WT(Soft)), denoising based on EMD and correlation coefficient, joint denoising based on EMD and wavelet soft threshold (EMD-WT(Soft)), joint denoising based on EMD and improved wavelet threshold (EMD-IWT), and it had excellent denoising effect on the transient vibration signal of the pipeline system.

IGWO;VMD;correlation coefficient;improved wavelet threshold;transient vibration signal