Research On Structural Deformation Reconstruction Technology Based On Fiber Grating Strain Sensing

With the rapid development of the modern aviation industry,higher and newer requirements have been imposed on the quality and efficiency of aircraft manufacturing.Due to the complex structure,large size and high stiffness requirements of the aircraft,the assembly quality of its parts and components is highly demanded based on the functional characteristics and working conditions of the aircraft,and the assembly quality of the aircraft is closely related to the accuracy of the assembly tooling.As a guarantee of aircraft assembly quality,high-precision measurements of small displacements and deformations in key areas of key components on the tooling are required,and the tooling parts have small size,large number,dense layout and the aircraft assembly process is complicated,so the displacement deformation is difficult to directly measure.Therefore,the measurement and displacement deformation reconstruction of key parts of tooling are the key research issues.This paper starts with the structural deformation measurement technology and combines the deformation reconstruction theory to research and analyze the existing measurement technology and deformation reconstruction theory,optimizes the existing measurement method,proposes new deformation reconstruction algorithms,and applies the research content to the deformation monitoring of the actual aircraft assembly tool locator.Main tasks as follows:1)The structure deformation measurement technology is studied.Based on the actual application conditions,the advantages and disadvantages of each measurement method are analyzed,and the fiber grating sensing method with outstanding advantages is selected.The principle of fiber grating sensing technology is analyzed and researched.The measurement error existing in fiber grating sensing technology is traced.A corresponding compensation method is proposed for the error.The validity of the error compensation method is verified through experiments.The deformation measurement technique in this paper also ensures the accuracy of strain information acquisition.2)Based on the research of structural deformation reconstruction theory at home and abroad,the inverse finite element method,modal method,Ko displacement theory and its algorithm are discussed and analyzed,and the advantages and disadvantages of the three theories are described.Because Ko displacement theory has the advantages of concise algorithm,high calculation accuracy and good real-time calculation,Ko displacement theory is selected as the research basis.3)Based on the problem that the structural root strain in the Ko displacement theory is difficult to obtain accurately,combined with theoretical analysis,the strain error minimization reconstruction algorithm,reconstruction algorithm based on beam bending theory and the root strain accurate derivation algorithm are proposed from three points of view: minimizing the root error of the structure,circumventing the strain measurement of the root of the structure and accurately solving the strain of the root of the structure.While preserving the simplicity and computational efficiency of the algorithm,the reconstruction error existing in the traditional Ko displacement theory is optimized and corrected.4)Using the aircraft assembly tool locator as the experimental object,a displacement and deformation reconstruction experiment system was built.By simulating the loading experiment of the actual working conditions,three optimization algorithms and the traditional Ko displacement theory algorithm were used to reposition the displacement deformation of the positioner.The reconstruction results are compared with the finite element simulation results and the measured displacement true values of the laser tracker.The root strain accurate derivation algorithm has outstanding reconstruction accuracy,and the reconstruction algorithm based on the beam bending theory is not widely applicable.Overall,the three optimization algorithms have effectively improved the reconstruction accuracy of the traditional Ko displacement theory algorithm to meet the needs of high-precision real-time deformation monitoring and reconstruction of the tool locator in place.