Research On Hilbert-Huang Transform For Structural Dynamic Parameters Identification

The dynamic characteristic parameter of the structure is an important parameter to study its vibration characteristics.It provides the basis for the optimization of the structural dynamics analysis,troubleshooting and structural dynamic characteristics.Currently,there are many kinds of methods of dynamic parameter identification of the time-invariant system.However,the methods of identifying the dynamic characteristic parameters of the time-variant system are still limited,and many problems need to be solved further.In this paper,the time-variant system is the object,and the dynamic characteristic parameters of the system is the target.The Hilbert-Huang Transform(HHT)is used to identify the dynamic characteristic parameters of the time-variant system.The paper provides the verification mean and the correction basis for the modeling analysis of the time-variant system.1.Comprehensively review the classical identification methods of the dynamic characteristic parameters,including time domain methods and frequency domain methods.It summarizes its development history,advantages and disadvantages and their respective scope of application.The research progress on the current dynamic parameter identification method of the time-variant structure is introduced.Four methods of time-frequency analysis and their application in the field of dynamic characteristic parameter identification are briefly narrated.The development and application of HHT are summarized.2.Introduces the fundamental definitions of Hilberttransform,analytic signal and instantaneous frequency.The important concepts involved in HHT,including single component signal,Intrinsic mode function(IMF),empirical mode decomposition(EMD)and Hilbert spectrum analysis are briefly described.The results of HHT and Fourier analysis are compared.It proposes new ideas and methods for applying HHT to structural dynamicparameter identification.The paper presents a method to solve the end effect of HHT when it processes the vibration signal-the method of smooth fitting and extrapolation.The paper presents a method to solve the modal aliasing when it processes the vibration signalcontaining noise-the method of parameter reorganization of IMF.The results of simulation study show that the two methods are effective.3.Derives the method of dynamicparameter identification of linear time-variant and single-degree-of-freedom structures based on HHT.According to the good effect of EMD in extracting single-order transient component,the method is extended to the parameter identification of multi-degree-of-freedom structures.The results of simulation study show that the method is effective.4.Design an test of the standard beam through different media to verify the method of dynamicparameter identification of linear time-variant structures based on HHT.The test piece is a straight beam with a rectangular cross section.First select the appropriate size of the beam by test,then use the traditional method to identify the dynamicparameters of the beam,as a reference value.Identify the dynamicparameters by the free vibration response in the process of the beam falling based on the method proposed in this paper,comparing with the results of the "static" test.It verifies the correctness of the method in this paper.The method is applied to the dynamic analysis of a downhill missile-car system and the effluent process of a submarine-launched missile.The instantaneous frequency of the structure is recognized with good effect.