Time-Frequency Characteristics of Parachute Gun Shockwave Based on VMD-HT

During the ejection process of the fighter pilot, the parachute is shot out by the life-saving seat gun, which generates a shockwave that endangers human safety. In order to accurately and stably extract the time-frequency distribution characteristics, the shockwave signal is obtained through parachute gun shooting experiments, and features of the shockwave signal is extracted by using Variational mode decomposition and Hilbert transform methods (VMD-HT). VMD is a high sampling rate shockwave signal decomposition technique, which is suitable for analysing unsteady airborne parachute gun shooting shockwave signals. The HT method is used to accurately extract the relationship between time, instantaneous frequency and energy for the decomposed signal, and to obtain the marginal spectra. The analytic results show that the shockwave signal lasting 3ms has a significant energy concentration in the low frequency band of 0∽1kHz, which is important for the better protection of pilots.