A chatter detection method in milling based on grey wolf optimization VMD and multi-entropy features

In metal cutting processing, especially in the processing of low-rigidity workpieces, chatter is a crucial factor affecting many aspects such as surface quality, processing efficiency and tool life. In this paper, a novel online chatter detection method for milling processes is proposed. In this method, firstly, periodic signal and noise parts are filtered by comb filter and empirical mode decomposition (EMD), respectively. Then, signal reconstruction is performed on the intrinsic mode functions (IMFs) based on the Pearson correlation coefficient. GWO is applied to reconstruct the signal to obtain optimized parameters. Subsequently, the reconstructed signal is decomposed by VMD with the optimal parameters. To get the frequency band in rich chatter information, the energy entropy characteristics of each order IMFs are calculated and the IMFs with entropy values greater than 0.3 are chosen as the second reconstructed signal. Finally, the multiscale permutation entropy (MPE) and multiscale fuzzy entropy (MFE) of the selected IMFs are calculated. Based on the value range of entropy in each processing state, the optimal scale feature is selected. The analysis results show that the proposed method can effectively detect the milling processing state based on the best scale.