A time-domain piecewise calculation method of a time-varying isolation platform

Improving low-frequency isolation performance and suppressing resonance transmission under the time-varying excitation are essential requirements for suppressing the vibration of underwater vehicles. Based on the vibration energy dispersion characteristics of time-varying systems in the frequency domain, the author proposed a time-varying isolation platform (TVIP) in previous research to broaden the low-frequency isolation range and suppress resonance. The time-varying distribution of isolators makes it difficult to separate spatial and temporal variables, so previous work only verified the isolation effect of TVIP through numerical solutions without delving into the mechanism of suppressing resonance. The existing time-varying structural dynamics calculation methods are difficult to solve this problem. This manuscript proposes a time-domain segmented computation (TDPC) method for analyzing the time-varying vibration characteristics of TVIP. The mechanism of suppressing resonance energy transfer in TVIP has been analyzed, which involves the disruption of the steady-state establishment process and the interaction between free modes. By comparing with finite element (FE) simulation results, it has been verified that this calculation method is effective for solving the response of the TVIP. The proposed time-domain piecewise calculation (TDPC) method not only simulates the dynamic evolution process of forced and free vibrations, but also greatly reduces computation time. The experimental and calculation results both confirm that the time-varying isolation distribution changes the inherent characteristics of the isolation system and reduces resonance energy transfer. The resonance frequency variation leads to the scatter of vibration energy in frequency domain. The influences of the isolator movement speed and path on the resonance peak are discussed. The vibration suppression effect of the TVIP under the multifrequency excitations is discussed. The results indicate that increasing the movement speed and resonance frequency variation range is beneficial for suppressing resonance transmission. The TVIP under multifrequency excitation can suppress low-frequency resonance and suit time-varying excitation situations.