Identification Of Acceleration Harmonic For An Electro-Hydraulic Servo Shaking Table Based On Wavelet Analysis

Electro-hydraulic servo vibration table is a kind of important equipment for vibration test,which is widely used in engineering field,because it has strong load ability and can produce large vibration force and large displacement vibration.Therefore,in-depth study of electro-hydraulic servo shaking table has important theoretical and practical value.In this paper,according to the harmonic components which lead to the distortion of acceleration response signal in the sinusoidal vibration test of vibration table,how to construct the harmonic identification system by wavelet analysis is studied.The purpose of this paper is to provide harmonic component information for harmonic suppression.Thus,the waveform distortion of the response signal is reduced and the reproduction precision of the acceleration response signal is improved.Firstly,the status quo of research and application of vibration table at home and abroad and the research results of harmonic identification method in related fields are analyzed,and the control system model of hydraulic power mechanism of electro-hydraulic servo vibration table is established.A three-state controller is designed to meet the requirements of system bandwidth.Then a real-time test system based on Matlab\ xPC Target is used to test the sinusoidal vibration of the vibration table,and the data of the sine vibration test is obtained.The experimental waveform shows the serious distortion of the response signal,including not only the fundamental frequency response signal,but also the integral harmonic component.The total harmonic distortion(THD)is used to measure the response.The degree of distortion of the signal waveform.In order to eliminate the harmonic component,the distortion of the signal is reduced,and the harmonic component in the acceleration response signal needs to be identified.Secondly,the unique advantages of wavelet analysis in signal processing are studied,and the equivalence between wavelet transform two-scale equation and filter bank is proved,which shows the effectiveness of wavelet analysis in dividing spectrum.For harmonic signals,the wavelet filter bank can be used to get the signals in different frequency bands first,then the amplitude can be estimated by the correlation function method,and the phase can be estimated by the Chirp-Z transform method.Through the analysis of the experimental data,it is shown that the multi-resolution filter bank is used to process the signal first,then the amplitude is estimated by the correlation function,and the Chirp-Z transform is used to estimate the phase of the signal,which can obtain more accurate identification results.Thirdly,based on the modern control theory,the state space model of acceleration response signal is established to solve the problem that only wavelet analysis algorithm is used to identify harmonics with low precision.The wavelet function is combined with the neural network to form the wavelet neural network.This signal model is combined with wavelet neural network,and the harmonic identification model of acceleration response signal is constructed.The validity of the identification model is verified by simulation experiment.Finally,the harmonic identification experiment is carried out on the acceleration response signal data obtained from sinusoidal vibration test by using the established identification system.The validity of the identification algorithm is verified by experimental data,and the harmonic identification system composed of signal state space model and wavelet neural network learning algorithm is verified and analyzed.It is proved that the identification model based on wavelet neural network has sufficient harmonic identification precision and can meet the needs of shaking table test system.