Research On Vibration Extraction Method Of Bridge Monitoring Radar Signal Based On Empirical Mode Decomposition

Radar monitoring bridge vibration is an important application direction of radar monitoring technology.Bridges vibrate under natural conditions and loads.Monitoring the vibration of Bridges can clarify the health of Bridges and ensure the safety of Bridges.Compared with the traditional monitoring method,using radar to monitor Bridges has the advantages of multi-monitoring points,all-weather,all-day,highprecision and so on.At present,many researchers have verified the feasibility of radar monitoring Bridges,but further research is still needed to extract vibration signals of Bridges in complex environments.For bridge vibration,there are two main vibration parameters to be extracted: vibration frequency and vibration deformation.Among the existing methods of vibration signal processing,Empirical Mode Decomposition(EMD)can carry out adaptive signal Decomposition,and this method is based on the time domain,simple and quick,Decomposition results have good properties,and is widely used.Therefore,based on empirical mode decomposition,radar vibration signal extraction in bridge monitoring is studied in this paper.The specific research contents are as follows:(1)The existing radar equipment and research work of bridge monitoring are sorted out,and the extraction research of partial radar vibration signals is introduced.Summarized based on the above two points,aiming at the bridge monitoring radar signal extraction,extraction and deformation frequency of the two problems,namely the complex environment of the bridge,a lot of noise and clutter exacerbate quadratic time-frequency analysis tool of crossover phenomenon,the vibration shape calculated according to the phase variables produce burr,jump to change wait for a phenomenon.The spectrum analysis and simulation of radar vibration signal model show that the spectrum of radar signal obeys Bessel function distribution under a certain amplitude wavelength ratio.At the same time,the noise characteristics and decomposition characteristics of EMD are simulated as the premise of this method.(2)The simulation shows that when using quadratic time-frequency tool to extract bridge frequency,the quadratic term problem of quadratic time-frequency tool itself is aggravated due to noise,environment and characteristics of radar vibration signal.To solve this problem,a time-frequency extraction method of bridge vibration frequency based on empirical mode decomposition and Wigner-Ville distribution is proposed in this paper.The method is divided into three steps,including preprocessing,EMD decomposition and Wigner-Ville Distribution(WVD)analysis.Pretreatment extract to the vibration of distance information,the EMD decomposition is separate the original signals in different frequency,to reduce the cross terms of WVD,whereas the last step WVD analysis can through the comparison of energy,calculate the fundamental frequency component,and show the component of the vibration frequency,the frequency to be read,reflect during the vibration process of degeneration.This method is an adaptive frequency extraction method,which can effectively reduce the cross term of WVD and reduce the influence of complex environment on frequency extraction.The effectiveness of the method is proved by analyzing the characteristics of bridge vibration radar signal and several experiments.(3)The simulation shows that when calculating deformations according to phase,phase mutation caused by noise and clutter will lead to burr and jump of deformations and affect the monitoring accuracy,so it is necessary to carry out de-noising and anticlutter processing.To solve this problem,a deformation extraction method based on empirical mode decomposition and non-local mean filtering is proposed in this paper.The Intrinsic Mode Functions(IMF)components are obtained by EMD decomposition of the time series signals from the original radar echo and correlation analysis of the decomposition results.Then,the filtering parameters of non-local Means(NLM)were determined adaptively by pre-processing and EMD decomposition results,and the IMF component dominated by noise was filtered.Finally,the reconstruction is carried out according to the relationship of EMD decomposition components,and the deformation are calculated according to the phase.This method can filter out the noise adaptively and reduce the error of deformation extraction effectively.The effectiveness of the method is verified by simulation and real bridge experiment.