DYNAMIC MODELING AND VIBRATION AND NOISE REDUCTION OF AUTONOMOUS UNDERWATER VEHICLES BASED ON RESONANCE CHANGER

In this paper, the vibration-acoustic model of the autonomous underwater vehicle (AUV) with nonlinear bearings is proposed based on the research background of vibration noise suppression and its concealment improvement. By finding the optimal design parameters of resonance changer (RC), the vibration and sound power level generated by the shell is minimized to achieve the purpose of anti-resonance. Firstly, the FEM of double-beam system with propeller-shaft-shell by Lagrange method is established. The nonlinear factors of bearing based on Hertz contact theory are added, and then the acoustic dipole radiation field model is derived according to the principle of sound propagation. Secondly, the Runge-Kutta method is used. The dynamic characteristics are analyzed by post-processing signals such as time domain response, spectrum, bifurcation diagram and amplitude-frequency response. Finally, the shell sound power level as the cost function is used and the parameters of the RC are designed. By comparing the two supports of nonlinear bearing and linear spring, it is found that the main trend of the sound power level of AUV shell under the former is distributed along the linear spring, which is lower, and reaches the peak in the corresponding resonance region. In addition, the results show that the RC can greatly reduce the resonance response amplitude and sound power level, noteworthily, the effect is the most significant at the resonance frequency design point. The frequency at the resonance frequency design point does not be shifted, however, the resonance frequency has a certain offset in other individual intervals in addition to reduction of the maximum resonance amplitude value. The theoretical model of this paper reveals the dynamic response characteristics of AUV and the influence law of parameters. The research results can provide new improvement ideas for the optimization design of vibration and noise reduction of AUV, and have certain theoretical guiding significance.