Error Characteristics And Modeling Of Synchronous Measurement Based On Operational Modal Analysis

In recent years,structural health monitoring(SHM)has become increasingly important in the field of engineering,which mainly involves the detection,diagnosis and repair of structural conditions.Generally,the structural health status is evaluated according to the response data of the structure to environmental excitation,and the real-time physical status of the structure is monitored by the change of the structural system status relative to the environmental excitation.In the engineering field,the modal parameter identification under environmental excitation has received more and more attention.In the health monitoring of large structures,such as dams,bridges,high-rise buildings,etc.,the sensor acquisition nodes are generally distributed in each part of the main structure,and the sensor acquisition nodes have a certain degree of dispersion,so it is difficult to ensure the clock synchronization of the whole acquisition network.So there are some errors in the collected data.When there are errors in the collected data,the estimation of the modal state of the structure may be affected to a certain extent,which leads to the misjudgment of the structural state.When there are errors in the data collected by sensors,these errors not only reduce the accuracy of modal parameter identification,but also hinder the guarantee of structural health monitoring.In this thesis,the correlation function is derived from the response of the structure to replace the impulse response function,and the frequency response function with error(jitter factor)is derived,so as to establish the mathematical model.Then,the least square complex exponential method(LSCE)was used to identify the modal parameters of the structure,In depth analysis of the clock jitter factor,how does it affect the modal parameters.The specific error characteristics of the beam are analyzed by mathematical theory modeling,and the validity and rationality of the conclusion are verified by numerical example simulation.Then,the error characteristics in the actual environment are verified by the working modal parameter identification of the experimental beam structure.The main contents of this thesis are as follows: 1)According to NEx T theory,the modal parameters of the system are obtained by using the correlation function instead of the impulse response function.When "clock jitter" occurs to the acquisition node,the node data signal recorded by the system contains "clock jitter factor",and the mathematical model of operation modal parameter identification theory with "clock jitter factor" can be deduced according to relevant theories.2)By setting the corresponding parameters,the impulse response signal is constructed.According to the above modal parameter identification theory(least square complex exponential method),the simulation code is written through MATLAB,and the simulation results are compared with the theoretical derivation to verify the validity and rationality of the theoretical derivation model.3)A steel beam structure is constructed,and the vibration response signals of the selected reference points of the structure are collected under the action of impulse excitation(hammer knocking),and the collected signals are used as the data source for subsequent modal parameter analysis.The experimental results are compared with the theoretical derivation to verify the validity and reliability of the theoretical derivation.4)Through the analysis of the theoretical calculation value and the comparison and analysis of the experimental simulation results and experimental results,the conclusion is drawn and the rationality of the model is demonstrated.