Research On Design Method Of Dynamic Vibration Absorber And Its Low Frequency Vibration Control Application

The mechanical equipment in the ship cabin will inevitably produce continuous vibration in operation.The medium and high frequency vibration will rapidly attenuate when it propagates to the water through the hull structure,which is characterized by the local vibration and sound radiation phenomena.It has little influence on the stealth performance of the ship.Low-frequency vibration not only has a small attenuation in long distance,but also is coupled with each other in the propagation that will produce adverse effects on reproductive capacity and migration of marine organisms.It is difficult to control the sound and vibration comprehensively.As one of the solutions to control the low frequency vibration,dynamic vibration absorber can effectively control the vibration of hull structure under the excitation of low frequency line spectrum.It has the advantages of simple structure,convenient installation,and low cost.In this paper,the ship structural of double bottoms is taken as the subject investigated,and the fixed-point theory optimization method based on curve fitting is used to design the the dynamic absorbers' parameters fixed on the ship structure of double bottoms.And according to the vibration absorption frequency based on structural excitation frequency and natural frequency respectively,the actual structure of the dynamic absorber is designed and manufactured.In addition,the layout scheme and the control scheme are studied.The main contents include:(1)For parameter design of additional dynamic absorber of continuous structure,the fixed-point theory optimization method based on curve fitting and the simulation optimization method based on genetic algorithm were studied.The simulation results show that the two methods could acquire vibration absorption effect well,and no significant effect between them.However,the simulation optimization method has a large calculation scale and is suitable for smaller calculation models.(2)The finite element model of double-deck bottom structure of a ship was established.Vibration response analysis results show that 33 Hz and 24 Hz were the main peak points of displacement response.Based on the fixed-point theory optimization method of curve fitting,the vibration absorption scheme at 33 Hz and 24 Hz frequencies of the model was designed.Among them,the combined vibration absorption scheme of 33 Hz and 24 Hz has remarkable effect.The simulation results show that the synthetic sound power of the inner and outer floor in 20?60 Hz band is reduced by 9.55 dB,and the effect of noise reduction is greater than that of the linear superposition of the two single frequency vibration absorption scheme.(3)The traditional genetic algorithm was improved.Taking the fixed-support plate model as the research object,the installation location optimizer of single vibration absorber and multi vibration absorber was introduced respectively and the optimization results were obtained.The simulation and experimental results show that the optimization method has better vibration control effect.The application of genetic algorithm to the installation location optimization of dynamic absorber is explored.(4)A rubber dynamic absorber was designed and manufactured.And the frequency adjustment range and the vibration reduction effect of rubber dynamic absorber were verified by experiments.The experimental results show that the rubber dynamic vibration absorber has a frequency regulation range of 45 Hz to 86 Hz and 158 Hz to 305 Hz,and in the vibration absorption experiment of the fixed plate,the peak value of the original frequency response function at the installation point is reduced by 21.8 dB.So the vibration reduction effect of the rubber dynamic absorber is remarkable;(5)A magnetic pole relative semi-active dynamic absorber was designed and manufactured.The electromagnetic stiffness of the ESAVA has good linearity,and the adjusting range of the electromagnetic stiffness is 70.1 kN/m.The natural frequency of the ESAVA can be adjusted from 24 Hz to 32 Hz by experiment.The experimental results are basically consistent with the simulation results.(6)The SIMULINK program based on frequency characteristic relation and phase difference semi-active control algorithm was written,which requires the control program to have the ability of fast identification and tracking of exciting force frequency.The results show that the semi-active control algorithm based on phase difference has more advantages.Then,the control time of the semi-active control algorithm based on phase difference is optimized in which the gain is adjusted according to the control stage.After the optimization,the total control time of the third frequency regulation process is reduced from 4.127 s to 2.758 s,which decreases by 33%,and the optimization effect is remarkable.