The WOA-VMD Combined with Improved Wavelet Thresholding Method for Noise Reduction in Sky Screen Target Projectile Signals

Aiming at the problem of low signal-to-noise ratio of the projectile signal output by the sky screen sensor, the symmetrical characteristics of the projectile signal and the noise sources were analyzed, and a joint denoising method of variational mode decomposition (VMD) and wavelet threshold based on the whale optimization algorithm (WOA) was proposed. This method employs the whale optimization algorithm (WOA) to globally optimize the key parameters of variational mode decomposition (VMD), namely the number of modes K and the penalty factor α, to obtain the optimal parameter combination that minimizes the envelope entropy. The original projectile signal is adaptively decomposed through the optimal VMD parameters. The variance contribution rate is used to screen the decomposed intrinsic mode function to retain the IMF component containing the projectile signal information and improve the signal-to-noise ratio of the projectile signal. Then, a wavelet threshold function is introduced to conduct secondary denoising processing on the selected modal components, further improving the signal-to-noise ratio of the projectile signal. Through noise reduction experiments on the measured projectile signals, it is proved that the signal-to-noise ratio of the signals has been significantly improved, indicating that this method can suppress noise while retaining the effective signal of the projectile to the greatest extent, laying a foundation for the recognition of projectile signals of the sky screen target.