Research Of Multichannel Experimental Modal Analysis Based On Virtual Instrument Technology

Experimental modal analysis is an important method to identify the structural parameters, and it also plays an important role in structure dynamic design and fault diagnosis. The system of modal analysis based on traditional instruments has disadvantages such as high price, single function, bad expansibility and so on, which make it unable to meet the demand for popularizing generally. It has great teaching and engineering value to develop a multichannel experimental modal analysis system which has low costs and good using performance with virtual instrument technology.The paper has done many researches on the algorithms of modal parameter estimation, model order determination and real or unreal modal identification. Based on the comprehensive analysis of Ensemble Empirical Mode Decomposition (EEMD) and Stochastic Subspace Identification (SSI), the paper proposed EEMD-SSI by combining the two methods. The measured signals are first decomposed into several intrinsic mode functions by using EEMD, then the decomposed data are used as the input of SSI to identify the modal parameters. The example shows that this method can improve the algorithm accuracy and reduce the difficulties of modal identification for users.Based on virtual instrument technology and modal analysis theory, a multichannel experimental modal analysis system is developed on the platform of Lab VIE W. It integrates global orthogonal polynomial method, SSI, and EEMD-SSI. The system has functions of real-time data acquisition, display, storage, replay and modal analysis. It can complete the whole process of modal test with hammering method or in environment-stimulation condition, including structural model inputs and mode animation. The system is easy to expand with friendly interface and good cost performance.Finally, two practical application examples have been given to test and verify the system’s software and hardware. Results show that the system runs stably and reliably, the software algorithm is correct and effective. The system can be used to analyze certain structure’s modal parameters. It can also be used as the basis of further studies about modal analysis theory.