The Design Of Experimental Modal Analysis System For Structure

Experimental modal analysis is based on the known system,and get the system frequency response function or impulse response function on the basis of mathematical processing between the input and output data,then obtain the modal parameters of the system through the modal parameter identification method.On the one hand,the experimental modal analysis has the advantages of good controllability,good test repeatability,high modal parameter identification accuracy and reliability,and plays an important role in structural design modification and damage identification,and has been widely applied.On the other hand,there are many excellent modal analysis software both at home and abroad,however,there is still a gap between domestic software and foreign countries.This article tracks and digest excellent foreign software and absorb its advantages.In this last respect,in order to meet the needs of mechanical structure design and mechanical fault diagnosis and improve operability and efficiency.In this paper,the front-end data acquisition and intermediate data processing are studied.A set of experimental modal analysis software is developed in this paper.The system has the characteristics of low cost and good interactivity.The main works and conclusions in this paper are as follows:The overall scheme design of the structural test modal analysis system is carried out in this paper,according to the actual demand of mechanical structure experimental modal analysis.It includes pre requirement analysis,system development platform selection,system overall framework construction,system function module division,data structure design and so on.The system hardware platform configuration and software target requirements are determined.According to the experimental modal analysis process,the system is divided into six functional modules: data acquisition module,structural modeling module,data processing module,parameter identification module,model verification module and vibration mode animation module.In this paper,the functional modules of the structural test modal analysis system are designed in detail.In view of the characteristics of the acquisition mode of the experimental modal analysis,the design of the acquisition parameter channel configuration is completed by imitating the acquisition module of the LMS system.The module of structural modeling refers to the existing mature software and designs the modeling method of coordinate input and substructure assembly.The data processing module deals with the acquisition of signals before identification,such as the calculation of frequency response functions.The parameter identification module integrates the PolyMax parameter identification method,which is highly recommended in recent years.The model verification module applies the modal decision criterion(MAC)to verify it;The vibration mode animation module realizes the adjustable animation form so as to display the various vibration modes of the structure.This paper has completed the system integration of six functional modules.A complete experimental modal analysis system is developed,and the experimental modal analysis experiment of the rectangular frame is carried out by using the system.The first five order natural frequencies and vibration modes of the frame structure obtained by the developed system.The developed system are compared with LMS Test.Lab modal analysis system.The results show that the system can effectively identify the modal parameters of the frame structure,and has higher recognition accuracy and recognition efficiency.The results verify the feasibility of using this system to test modal analysis and the feasibility of Engineering application.