CN-116164659-B - Tube structure morphology inversion method for leading in angular deviation coefficient and strain field pre-reconstruction

Abstract

The invention discloses a tube structure morphology inversion method for leading in angular deviation coefficients and strain field early reconstruction, which comprises the following steps of arranging high-density weak reflection grating distributed optical fiber sensors on the surface of a cylindrical tube structure in a spiral mode, carrying out cylindrical tube structure strain field inversion based on the angular deviation coefficients, leading in the high-density weak reflection grating distributed optical fiber sensors, reconstructing inversion tube structure morphology based on the strain field early, and further improving accuracy of cylindrical tube structure morphology inversion by adopting a variable lift angle layout method.

Inventors

• ZENG JIE
• WANG YUNSONG
• XU JIHONG
• ZHU QINGFENG
• ZHAO YUEQI
• LU RUIXIN
• SUN YANGYANG

Assignees

• 南京航空航天大学

Dates

Publication Date

20260505

Application Date

20221226

Claims (2)

1. 1. The pipe structure morphological inversion method for leading in the angular deviation coefficient and the strain field pre-reconstruction is characterized by comprising the following steps of: The method comprises the steps that firstly, a high-density weak reflection grating distributed optical fiber sensor with a fixed lift angle or a variable lift angle is spirally arranged on the surface of a cylindrical tubular structure; Fixing an elevation angle, pasting and arranging a density weak reflection grating distributed optical fiber sensor on the surface of a tested cylindrical tubular structure fixedly supported by a single end in a spiral mode, taking the circle center of a circular tube at the cross section of a solid support end as an origin, taking the connecting line of a sensor path and the cross section and the origin as a polar axis, establishing a column coordinate system (r, theta, h) by taking the axial direction of the circular tube as a vertical coordinate axis, wherein h is a vertical coordinate, and if projection of any point at the cross section of the solid support end under the coordinate system is made, r and theta are the polar diameter and the polar angle of the point, and the sensor laying path meets the following conditions under the column coordinate Wherein θ 0 is an independent variable, D T is the outer diameter of the cylindrical tubular structure to be measured, L is the length of the tubular structure, Is the helix path lead angle; Changing an elevation angle, pasting and arranging a density weak reflection grating distributed optical fiber sensor on the surface of a tested cylindrical tubular structure fixedly supported by a single end in a spiral mode, taking the circle center of a cross section circle of a circular tube at a solid support end as an origin, taking the connecting line of a sensor path and the cross section intersection point and the origin as a polar axis, establishing a column coordinate system (r, theta, h) by taking the axial direction of the circular tube as a vertical coordinate axis, wherein h is a vertical coordinate, and if projection of any point at the cross section of the solid support end under the coordinate system is made, r and theta are the polar diameter and polar angle of the point, and the sensor laying path meets the following conditions under the column coordinate Wherein h N-1 is the h coordinate of the end of the N-1 th turn, For the initial angle of ascent, The inversion precision of the space deformation can be effectively improved when the cost is limited, the optical fiber length is limited, the demodulation capability is limited, the computer calculation force is limited or the calculation time is required to be faster by adopting the layout scheme; Developing inversion of cylindrical tubular structure strain field based on angular deviation coefficient introduction and high-density weak reflection grating distributed optical fiber sensor (2-1) The axial strain epsilon 1 of the sensor measured by the high-density weak reflection grating distributed optical fiber sensor distributed along the spiral line has the following corresponding functional relation with the axial strain epsilon of the cylindrical tubular structure: Calculating axial strain distribution information of the surface of the cylindrical structure according to the sensing path direction strain by an inverse function of the Poisson ratio; (2-2) dividing the surface of the pipe to be measured into N T sections so that any point P m (r m ,θ m ,h m of the N T +1(0≤n T ≤N T -1 section on the surface of the pipe can be satisfied The middle line of the section is as follows: (2-3) based on Optical Frequency Domain Reflection (OFDR), strain distribution data of a plurality of points on the sensing path can be measured, If there are n known points of strain measured by the sensors in the n T +1 th interpolation, the calculated half variance γ ij ,γ ij between the i (1. Ltoreq.i. Ltoreq.n) th point P i (r i ,θ i ,h i and the j (1. Ltoreq.j. Ltoreq.n) th point P j (r j ,θ j ,h j can be expressed as: Wherein E is a mathematical expectation, ε i is the strain value of the ith sensing point, ε j is the strain value of the jth sensing point; (2-4), defining k d as an angular deviation coefficient, can be expressed as: Wherein delta theta is the angle difference between each point and the middle line of the section; (2-5), definition For the apparent distance between the ith point and the jth point, satisfy Fitting r ij to the model by means of an exponential model in a model representative of the semi-variational function The relation of the obtained half variation function r (d A ) is that any one of the surfaces of the tested pipe fitting meets the requirement Points of (2) P 0 (r 0 ,θ 0 ,h 0 ) as the point to be estimated, the apparent distance between each sensing point and the point to be estimated can be calculated according to the above-mentioned apparent distance calculation method Further obtaining a half variance gamma i0 between the known point and the unknown point; (2-6), calculating a weight coefficient matrix W= [ W 1 ,w 2 ,…,w n ] T , W meeting the following conditions Wherein w i is the weight coefficient of the i-th known point, and the strain estimated value of the point to be estimated is calculated by the traditional Kriging interpolation method Satisfy the following requirements Taking enough points to be estimated in the interpolation of the section, and repeating the process to calculate the strain value of each point to be estimated, thereby realizing the satisfaction of Inversion of the strain field in the range, so that the axial strain field along the surface of the cylindrical tubular structure can be reconstructed after N T sections of interpolation; step three, reconstructing the structural shape of the inversion tube based on the strain field in advance According to the method in the second step, firstly, carrying out the strain field pre-reconstruction of the cylindrical tubular structure to obtain the strain distribution and response information of the high-spatial resolution structure, and further carrying out the morphological inversion of the cylindrical tubular structure on the basis of obtaining the global strain distribution of the monitoring object in advance; (3-1), inversion in the extraction step two Wherein the method comprises the steps of Strain along the axial direction of the cylindrical tubular structure at θ=0, Strain along the axial direction of the tubular structure at θ=180°, Strain along the axial direction of the tubular structure at θ=90°, Strain along the axial direction of the tubular structure at θ=270°; (3-2) implementing temperature self-compensation of a single sensing path based on the following method Since the temperature difference between any point to be estimated P (r 0 ,θ 0 ,h 0 ) and the point Q (r 0 ,π+θ 0 ,h 0 ) is small, the method comprises the following steps: ε Pw -ε Qw ＝2ε Pw Wherein ε Pw is the strain due to bending at point P and ε Qw is the strain due to bending at point Q, and the inversion method is as described above Satisfy the following requirements Wherein the method comprises the steps of For bending to produce strain, ε F is a temperature-induced spurious strain, and therefore (3-3), The strain is a function of distance h from the anchor (i.e., vertical) as determined by the relationship of strain-curvature-displacement, namely: Wherein w X 、w Y is a flexible line equation of bending in the X direction and the Y direction of the cylindrical tubular structure respectively, and space deformation inversion based on a strain-curvature-displacement re-integration algorithm is realized.
2. 2. The method for inverting the morphology of the tube structure with the introduction of the angular offset coefficient and the strain field pre-reconstruction according to claim 1, which is characterized by comprising the following steps: step one, the helix angle of the spiral path 45 °; step two (2-1) is a function relationship between the axial strain epsilon 1 of the sensor and the axial strain epsilon of the cylindrical tubular structure, which is measured by the high-density weak reflection grating distributed optical fiber sensor distributed along the spiral line:

Description

Tube structure morphology inversion method for leading in angular deviation coefficient and strain field pre-reconstruction Technical Field The invention belongs to the field of structural health monitoring based on an optical fiber sensor, and particularly provides a tube structure morphology inversion method for leading in angular deviation coefficient and strain field early reconstruction. Background The deformation monitoring of the circular tube structure has important research significance in the monitoring fields of air refueling flexible pipelines, unmanned aerial vehicle wing spars, tunnels based on inclinometer pipes or highway slope soil bodies and the like, however, the deformation monitoring of the circular tube structure is generally monitored by adopting paired sensing paths at present, wherein each pair of paths can only monitor deformation in one direction, a large number of sensors are used, and the strain on the surface of the circular tube cannot be monitored comprehensively. The deformation reconstruction of the tube structure based on the conventional distributed optical fiber sensor generally needs one or two sensing paths which are symmetrically arranged to carry out two-dimensional morphological inversion, and a single sensing path cannot carry out temperature compensation and is easily interfered by strain generated by tension and compression, so that the accuracy is lower. In addition, the sensing paths in the symmetrical layout form can reach higher precision, but in order to cover different quadrant monitoring areas of the cylindrical surface as much as possible, more optical fiber sensing paths distributed along the axial direction of the tubular structure are required to be distributed, so that the testing cost is increased, and the burden of a demodulator is increased. And each group of symmetrically distributed optical fiber sensors can only perform deformation inversion in one direction, and cannot directly extract spatial position information. The multi-core optical fiber can also be based on Frenet frame or minimum rotation frame method and other algorithms, and can realize three-dimensional deformation inversion of a single path, but the multi-core sensor used by the method has relatively high cost, complex algorithm and high demodulation difficulty. For monitoring tubular structural members, for example Tian Hao, an OFDR sensor based on a spiral layout is used for monitoring corrosion of reinforcing steel bars, the OFDR sensor with the spiral layout is commonly used for monitoring strain, temperature and the like of the tubular structural members, but a technology for monitoring deformation of a cylindrical tubular structure by adopting a spiral layout form is rarely adopted. Kerling interpolation has been applied to tube structure surface strain field inversion, such as Hu Xitao barrel section strain field reconstruction and load position identification schemes. However, the scheme cannot realize deformation monitoring of the structural member, and strain inversion is realized only in a part of the cylinder. Compared with the prior method of reconstructing discrete deflection based on discrete strain measurement point information and then carrying out interpolation fitting, the scheme of reconstructing the strain field and directly inverting all deflection information can realize the inversion of the structure space deformation of the measured pipe with temperature compensation on one sensing path under the condition of maintaining higher precision, thereby reducing the consumption of optical fibers and occupying the number of channels of a demodulator. In addition, the patent provides the concept of the angle deviation coefficient, and further improves the strain inversion precision by utilizing the piecewise interpolation, so that the method has extremely high practical application value. Disclosure of Invention The invention aims to realize the inversion of the tube structure morphology with temperature compensation by utilizing a single OFDR sensor, comprising the inversion of a strain field and the inversion of spatial deformation. The invention provides a solid spiral sensor layout circular tube form inversion method based on strain field early reconstruction and angular offset coefficient introduction, which comprises the following steps: The method comprises the steps that firstly, a high-density weak reflection grating distributed optical fiber sensor with a fixed lift angle or a variable lift angle is spirally arranged on the surface of a cylindrical tubular structure; Fixing an elevation angle, pasting and arranging a density weak reflection grating distributed optical fiber sensor on the surface of a tested cylindrical tubular structure fixedly supported by a single end in a spiral mode, taking the circle center of a circular tube at the cross section of a solid support end as an origin, taking the connecting line of a sensor path and the cross section and