Research And Development Of Virtual Instrument For Vibration Experimental Modal Analysis

With the experimental modal analysis technology is becoming more and more prominent in the field of structural dynamics, its application has been widely used. However, the cost of traditional experimental modal analysis software is very expensive and the technology secrecy is too high, but the virtual instrument has the advantages of a high cost performance, convenience and scalability. Therefore, based on virtual instrument technology, a set of experimental modal analysis system with low cost, good interaction and good expansibility is able to be developed, which not only can be used in practical engineering analysis, but also has a promotion effect on teaching and scientific research.In this paper, experimental modal analysis basic principle, data acquisition and trigger structure modeling method, the modal parameter identification algorithm and virtual instrument aspects are researched. Particular attention has been devoted to studying the software trigger technology and modeling technology of LabVIEW is deeply studied. Compared with the domestic and foreign experimental modal analysis system, this system adopts the software trigger mode instead of the hardware triggered mode in the data acquisition part, thus to realize the portability of the test system. The average technique in the frequency response test is adopted, to ensure the accuracy of the measured frequency response data.On the basis of studying the basic principle of the experimental modal analysis, the test procedure and the software of the test modal analysis at home and abroad, a system that integrated the geometric modeling function, the data collection function and the FRF function, the modal parameter identification function and the modal shape animation function was developed based on LabVIEW development platform. Among which, the model can be independently modeled by the system singly, and can be imported into the model by third party software in the geometric modeling part. We adopt FPDI parameter identification method which is more popular in the modal field, FDPI parameter identification method which has a good recognition effect in narrow band and LSCE parameter identification method which has better recognition function in a wider frequency band. Examples show that we can achieve a better recognition effect by using different modal parameter identification methods.At last, the hardware and software system are verified through the experimental modal analysis of simply supported beam, thin circular plate and motor bearing. Moreover, compared with ANSYS and ME'scope respectively. The result shows that the system is stable, effective and accurate that can be applied to the practical engineering projects of noncomplex structure, and can also be used as experimental modal analysis software for class teaching. Meanwhile, it can be used as a basic platform for further research and development of experimental modal analysis technology based on virtual instrument technology.