The Research Of Damage Identification Method Of Oil Derrick Based On The Principal Component Analysis Measured Frequency Response Functions

Oil drilling derrick is an important part of oil equipment. During the drilling process, the derrick may appear the damage because of many reasons. For many years, some accidents of derrick collapse have happened occasionally. In order to insure the security,integrity and the durability of the derrick, it is very necessary to evaluate the safety of the derrick. With the development of the detection technology, it has been possible to research a scientific, simple, applicable derrick damage identification method.This article elaborates the technology of structural damage identification domestic and foreign research present situation, Introduced each kind of theory and the research technique for structural damage identification. It focuses on the mathematical statistics of principal component analysis method. For frequency response function contains the richer and more reliable information of the structure from structural dynamic testing and the advantages of principal component analysis. A method of derrick damage identification is proposed based on the principal component analysis and multivariate control chart using frequency response functions as basic variables. Original data matrix is formed using frequency response function obtained from derrick dynamic test. With principal component analysis, the variable space dimensions of original data can be reduced. Then the characteristics of original data can be analyzed and extracted from lower dimension space using first several principal components which contain the most original data information. The derrick damages can be identified by separating the singular data in the control chart, which is formed using first several order principal components. In order to verify the reliability of the method, a derrick model was tested in nine kinds of damage cases from the dynamic test experiment. The result shows that the proposed method is reliable and has a good adaptability for non-linearity derrick under the noise environment. Since the proposed method does not need modal parameters and avoids the errors of modal extraction, it is straightforward and accurate for derrick damage identification.