Research on time-frequency characteristics of electromagnetic signals from coal and rock blasting based on DBO-VMD filtering

The conventional vibration monitoring of mining and blasting operations is easily affected by the surrounding environment or monitoring system, which affects the monitoring effect. This paper proposes a blasting monitoring method based on electromagnetic signals and studies the time-frequency characteristics of blasting electromagnetic signals. Firstly, the signal decomposition method of DBO-VMD was proposed, and the optimal fitness function envelope entropy for VMD parameter optimization was obtained. This function can quickly lock the optimal parameter combination, avoid mode mixing phenomenon, and the decomposition effect is better than EMD; a denoising method based on the central frequency criterion was proposed to filter out high-frequency and low-energy components, and it was confirmed that the denoising performance of this method is more than 2 times better than EMD in terms of signal-to-noise ratio performance; it is found that the skewness is greater than 0, the kurtosis is between 0.9-4.6, the pulse index is between 3.7-6.1, and the frequency band is below 20 kHz, the signal energy is the largest when the main rupture event occurs, and the strongest component channel is below 10 kHz, and the amplitude of the signal component decreases rapidly with the rise of the channel, while the low-energy pulses in the non-rupture period are concentrated in the 0-4 kHz frequency band, and the overall frequency band of the signal is at very low frequency.