Vibration Control And Parameter Optimization Of Dynamic Vibration Absorber Based On Real-time Frequency Identification

With the development of technology,there are more and more buildings such as large-span buildings and footbridges.It has high strength under the action of static load,but under the strong external effects such as earthquake,strong wind and human-induced vibration,it will cause huge vibrations,which will not only shorten the life of the building,but even cause the structure to collapse.The traditional dynamic vibration absorber is a vibration damping device commonly used for structural vibration control.It mainly consists of springs,masses and damping elements.When its frequency matches the natural frequency of the controlled structure,it can have a good vibration reduction effect.However,during long-term use,the frequency drift phenomenon occurs in the controlled structure,and the vibration damping effect of the traditional dynamic vibration absorber is seriously weakened.To this end,a new type of variable frequency dynamic vibration absorber device based on magnetorheological elastomer is proposed.Magnetorheological elastomer(referred to as MRE)is a new type of magnetorheological smart material.Its shear modulus can change with the applied magnetic field,thereby changing the stiffness of the dynamic vibration absorber and adjusting the current of the variable frequency dynamic vibration absorber.This is of great significance for improving the defects of traditional dynamic vibration absorbers.This article discusses the research status and applications of MRE and dynamic vibration absorbers,introduces the relevant theories of MRE.The optimal design method of traditional dynamic vibration absorber based on Den Hartog fixed-point theory and the key factors affecting its vibration reduction performance are discussed in detail.A method based on Fourier transform(FFT)Hilbert-Huang transform(HHT)and natural excitation technology(NEx T)was used to identify the natural frequency of the main structure,and a real-time frequency identification method for the controlled structure was proposed,then established a real-time frequency identification model based on Simulink was established,and used a pedestrian bridge as an example to verify the theoretical validity of the method.By studying the physical characteristics of the MRE and the characteristics of the variable frequency dynamic vibration absorber,the structure and parameters of the variable frequency dynamic vibration absorber are determined,and the real-time tracking process of the variable frequency dynamic vibration absorber for the frequency of the fixed steel beam is proposed.By changing the mass to change the natural vibration frequency of the controlled structure,under different number of mass blocks,the vertical vibration control test of the fixed steel beam by the variable frequency dynamic vibration absorber based on real-time frequency identification was completed.Compared with the traditional dynamic vibration absorber,the results show that when the frequency of the fixed steel beam is changed,the variable frequency dynamic vibration absorber can still maintain a better control effect.At the same time,the correctness of the real-time frequency identification method is also verified through experiments.Based on the LQR active control algorithm,the theoretical formula of the optimal dynamic vibration absorber is proposed,and compare the damping control effect of the optimal dynamic vibration absorber based on Den Hartog fixed-point theory and LQR control algorithm design under rectangular pulse excitation and sinusoidal excitation.The simulation results show that the two optimal dynamic vibration absorbers(based on displacement and acceleration response)based on the LQR control algorithm have similar performance and are slightly better than those based on the Den Hartog fixed-point theory.