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Operational Modal Identification of Spacecraft Structures

Author: WangXuan
Tutor: SongHanWen
School: Fudan University
Course: Engineering Mechanics
Keywords: Spacecraft structure Operational Modal Analysis (OMA) Natural Excitation Technique(NExT) Stochastic Subspace Identification(SSI) Impulse Excitation
CLC: V414
Type: Master's thesis
Year: 2008
Downloads: 238
Quote: 3
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Abstract


Spacecraft structures are usually operating under very complex environment and subjected to some uncertain environmental excitations. So that it is costly and difficult to realize input and measurement of excitation of spacecrafts and their components. So that, the conventional modal test technology and analysis will face great difficulties. Operational modal analysis (OMA) can directly establish modal model and identify the structure parameters from the response data, the results are more suitable to the practical conditions. In addition, it is more suitable to identify modal parameters of the structure by the method of operational modal analysis, which is more accurate to reflect the operating condition of the structure.However, in the real engineering application, the structure is subjected to some non-steady environmental excitation besides random excitation. For example, the rockets launch, explosive device explosion, rockets separation and spacecraft going through the water surface. Therefore, the OMA can not be applied for them directly. With this background, author studies several issues such as the application scope of OMA, the application of OMA in spacecraft structures and a group of test of an aluminum plate under different operating status. Thesis focuses on several parts as following:1. Reviewed the development of the OMA, deduced the theoretical foundation of OMA in detail, then designed a group tests of a rectangular aluminum plate. By comparing the results identified by OMA and traditional mode analysis, verified the correctness and engineering applicability of the OMA under white noise excitation.2. Made a assumptions of non-time-varying in short period to deal with the typical slow-time-varying process of aerospace engineering fields. Thus, OMA can be applied to the Spacecraft structure under operating conditions. This method was successfully applied to identify modal parameters for two groups of engineering simulation data, achieved satisfactory results, verify the validity of OMA in engineering application.3. Proposed and proved a new OMA theory, which can be applied to the structures under environmental excitation including white noise and complex multi-point irregular impacts. Defined an algorithm of "correlation function" for attenuation signal, proved that NExT theory can also be applied to non-steady excitations by deriving the OMA algorithm under joint excitation environment. Several simulation examples and related test were proposed in this thesis to verify the correctness of the theory. So that author extends the OMA theory and expands the OMA application scope.

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CLC: > Aviation, aerospace > Aerospace ( Astronauts ) > Basic theory and experiments > Spacecraft structural mechanics
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