Abstract
Traditional modal testing has difficulty accurately identifying the ultralow-frequency modes of flexible structures. Ultralow-frequency excitation and vibration signal acquisition are two main obstacles. Aiming at ultralow-frequency modal identification of flexible structures, a modal testing method based on Digital Image Correlation method and Eigensystem Realization Algorithm is proposed. Considering impulse and shaker excitation are difficult to make generate ultralow-frequency vibration of structures, the initial displacement is applied to the structure for excitation. The ultralow-frequency accelerometer always has a large mass, which will change the dynamics performance of the flexible structure, so a structural vibration response was obtained through the Digital Image Correlation method. After collecting the free-decay vibration signal, the ultralow-frequency mode of the structure was identified by using the Eigensystem Realization Algorithm. Ground modal tests were conducted to verify the proposed method. Firstly, a solar wing structure was adopted, from which it was concluded that the signal acquisition using Digital Image Correlation method had high feasibility and accuracy. Secondly, an ultralow-frequency flexible cantilever beam structure which had the theoretical solution was employed to verify the proposed method and the theoretical fundamental frequency of the structure was 0.185 Hz. Results show that the Digital Image Correlation method can effectively measure the response signal of the ultralow-frequency flexible structure, and obtain the dynamics characteristics.
Highlights
Accepted: 20 December 2021With the development of aerospace technology, large-scale flexible structures with ultralow-frequency modal characteristics [1,2,3,4], such as solar panels and developable trusses [5], have been widely applied
This paper proposes an ultralow-frequency flexible structure modal identification method based on the Digital Image Correlation method (DIC) method
DIC method method is selected to they are released released synchronously, and is selectedsystem, to measure measure is respectively applied by the ultralow-frequency flexible structure excitation and the distance and pixel resolution, Among them, each node shooting camera is shown in the distance and pixel resolution, Among them, each node shooting camera is shown in they are released synchronously, and the appropriate DIC method is selected to measure
Summary
With the development of aerospace technology, large-scale flexible structures with ultralow-frequency modal characteristics [1,2,3,4], such as solar panels and developable trusses [5], have been widely applied. The non-contact measurement method does not need to attach the sensor to the test piece, fundamentally eliminates the influence of additional mass, and has the advantage of high measurement sensitivity. Digital Image Correlation method (DIC) is an emerging vibration measurement method in recent years It has the advantages of not affecting the dynamic performance of the structure under test and saving the cost of modal measurement. For the vibration test of ultralow-frequency flexible structures, Trebună et al [26] used the DIC method to excite the steel fan blades with white noise signals for modal analysis, and used the frequency domain decomposition method to determine the mode from the output power spectral density matrix. This paper proposes an ultralow-frequency flexible structure modal identification method based on the DIC method. The theoretical results are compared to verify the feasibility and accuracy requirements of the ground modal test system for the dynamic characteristics of the flexible structure designed in this paper
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