CN106885529A - A kind of long-distance distributed optical fiber spatial attitude monitors sensor and engineering implementation method - Google Patents

Abstract

The invention provides a long-distance distributed optical fiber spatial attitude monitoring sensor and an engineering realization method. The long-distance distributed optical fiber spatial attitude monitoring sensor is embedded with four 90-degree circumferential layouts in the thermoforming process of polymer composite ribs. Single-mode strained fiber, a loose-jacketed single-mode temperature fiber, and a bundle of seven-filament reinforced steel strands. The single-mode strain optical fiber measures the longitudinal strain in four directions of the sensor, the single-mode temperature optical fiber measures the ambient temperature and corrects the strain, and reconstructs the spatial attitude of the sensor segmentally based on the strain-curvature and differential geometric relations. The long-distance distributed optical fiber spatial attitude monitoring sensor of the present invention is deployed in large-scale structures such as roadbeds and submarine optical cables, and can monitor tens of kilometers of structural strain. Based on the conversion from strain to curvature, online monitoring of the overall attitude of the structure can be realized. The safety monitoring and evaluation of the system has important engineering significance.

Description

A long-distance distributed optical fiber space attitude monitoring sensor and engineering implementation method

technical field

The invention belongs to the field of structural monitoring, and relates to a long-distance distributed optical fiber space posture monitoring sensor and an engineering realization method.

Background technique

Linear structures such as long-distance pipelines, submarine optical cables, and long-distance roadbeds are major infrastructures, and their normal operations are closely related to the national economy and life. These long-distance linear structures are affected by human factors, natural disasters, and environmental changes during their long-term service, and large deformations that affect structural safety will occur, eventually leading to structural failure. For example, pipe deformation and pipe explosion caused by excessive foundation settlement, driving irregularity or derailment accidents caused by uneven subsidence of the roadbed, submarine optical cable breakage and power failure caused by tides, ship anchoring and hanging cables, etc., have caused certain property damages. losses and casualties. Structural failure is a damage evolution process. It is of great engineering significance to use effective means to monitor structural deformation, grasp the overall posture of the structure, evaluate the safety status of the structure, and provide early warning of disasters and accidents.

At present, most of these major infrastructures have established structural safety monitoring or detection systems, mainly including manual inspection, local deformation (longitudinal strain or settlement) monitoring, GPS deformation monitoring, and fully distributed longitudinal strain monitoring. Manual inspection is a detection technology, which has disadvantages such as long manual detection cycle, high labor intensity, and the detection effect is related to the quality of the detection personnel; local deformation monitoring technology, such as local fiber grating technology and single point settlement sensor can only monitor the local shape of the structure , not suitable for full-scale monitoring of long-distance linear engineering; GPS deformation monitoring belongs to surface deformation monitoring, and also cannot cover long-distance linear structures. Distributed optical fiber Brillouin sensing technology has the characteristics of long test distance, anti-electromagnetic field interference, and good durability. It has been applied in long-distance and large-volume structural safety monitoring. However, most distributed sensors currently focus on structural longitudinal stress For strain testing, and for the monitoring of structural space form, multiple distributed optical fiber sensors need to be deployed at the same time, resulting in high cost and difficulty in monitoring system integration. For long-distance linear structure safety monitoring, there is an urgent need for a long-distance distributed spatial attitude monitoring sensor that meets the needs of engineering installations. At present, there are relevant literatures reporting the use of discrete fiber grating sensors to monitor the spatial attitude of small-scale structures (Zhu Xiaojin, Lu Meiyu, Zhao Xiaoyu, etc., Algorithm and Visual Analysis of 3D Reconstruction of Space Manipulator Vibration Form, Journal of System Simulation, 2009, 21( 15): 4706-4709), this method has only a few discrete measuring points, it is difficult to carry out large-scale structure space attitude monitoring, and the research on using distributed optical fiber Brillouin sensing technology to carry out large-scale structure space attitude monitoring has not yet been found. reports.

Contents of the invention

Aiming at the deficiencies of the prior art, the present invention provides a long-distance distributed optical fiber spatial attitude monitoring sensor and an engineering implementation method. The sensor combines four single-mode optical fibers, a single-mode optical fiber with a loose sheath and a bundle of 7 The steel strand is embedded in a polymer composite bar with a diameter of 5-8mm, and four single-mode optical fibers are used as strain sensing optical fibers to measure the strain and temperature information of the corresponding position of the optical fiber; the engineering implementation method is to analyze the strain test data in the sensor Perform temperature correction and mutation recognition processing, and analyze the spatial attitude of the sensor in sections and regions based on the strain-curvature geometric relationship.

In order to achieve the above object, technical scheme of the present invention is:

A long-distance distributed optical fiber space attitude monitoring sensor, including four single-mode strain optical fibers 1, a single-mode temperature optical fiber with a loose sheath 2, a bundle of seven-filament steel strands 3, polymer composite ribs 4, two An optical fiber junction box 5 and two transmission optical cables 6.

The single-mode strained optical fiber 1 , single-mode temperature optical fiber 2 and seven-filament steel strand 3 are arranged inside the polymer composite rib 4 during the thermoforming process of the polymer composite rib 4 .

The four single-mode strained optical fibers 1 are circumferentially arranged in the polymer composite rib 4 at intervals of 90 degrees, 1.5mm away from the outer circumference of the polymer composite rib 4, and each single-mode strained optical fiber 1 is used as a strain sensing element in the sensor. The unit is used for strain testing and strain-curvature attitude reconstruction in four directions: up, down, left, and right. A single-mode temperature optical fiber 2 with a loose sheath and a bundle of seven-filament steel strands 3 with a diameter of 2 mm are arranged in the middle of the polymer composite rib 4, and the single-mode temperature optical fiber 2 is located on the center line; The single-mode temperature optical fiber 2 is used as the temperature sensing unit in the sensor to test the ambient temperature and the temperature compensation of the 4 strain sensing units; the seven-wire steel strand 3 is used to enhance the tensile and shear strength of the sensor. The two ends of the polymer composite rib 4 are connected with the optical fiber distribution box 5 , and the optical fibers in the optical fiber distribution box 5 are fused together to form an optical path, which is connected with the transmission optical cable 6 .

The polymer material in the polymer composite rib 4 is a material with good durability such as polyethylene and polypropylene, which is compounded with glass fiber in the thermoforming process. According to monitoring requirements, the inner diameter of the polymer composite rib 4 is 5- 8mm.

The engineering implementation method using the above-mentioned long-distance distributed optical fiber space attitude monitoring sensor includes the following steps:

In the first step, long-distance distributed optical fiber spatial attitude monitoring sensors are deployed in the structure, and the structure cooperates with the deformation.

In the second step, the four single-mode strain optical fibers 1 in the long-distance distributed optical fiber space attitude monitoring sensor measure the initial strain values in four directions of the i-th measuring point in real time.

In the third step, the single-mode temperature optical fiber 2 with a loose sheath performs temperature correction on the initial strain values tested by the four single-mode strain optical fibers 1, the corrected strain value is differentiated from the initial strain value of the sensor, and the strain mutation is calibrated in sections region, based on the strain-curvature relationship, the spatial pose of the sensor is reconstructed piecewise.

The effect and benefit of the present invention are that the long-distance distributed optical fiber spatial attitude monitoring sensor directly measures the strain in 4 directions of the sensor through the four internal single-mode optical fibers, and analyzes the spatial form of the sensor based on the strain-curvature geometric relationship. The single-mode fiber of the sheath only measures the ambient temperature, and the strain values measured by the four single-mode fibers are temperature compensated. Long-distance distributed optical fiber spatial attitude monitoring sensors are deployed in linear structures such as long-distance pipelines, submarine optical cables, and roadbeds, and can directly obtain spatial geometric deformation information of corresponding structures, which is of great significance to the safety monitoring and evaluation of structures.

Description of drawings

Figure 1 is a schematic diagram of the structure of a long-distance distributed optical fiber space attitude monitoring sensor.

Fig. 2 is a sectional view along plane A-A.

Fig. 3 is a schematic diagram of the i-th micro-segment of the long-distance distributed optical fiber space attitude monitoring sensor; (a) is the structure diagram of the i-th micro-segment of the sensor in the unstressed state; (b) is the i-th micro-segment of the sensor under stress Schematic diagram of the force state.

In the figure: 1 single-mode strain optical fiber; 2 single-mode temperature optical fiber; 3 seven-wire steel strand; 4 polymer composite rib; 5 optical fiber junction box; 6 transmission optical cable.

detailed description

The specific embodiments of the present invention will be described in detail below in conjunction with the technical solutions and accompanying drawings.

Figure 1 is a schematic diagram of the structure of a long-distance distributed optical fiber space attitude monitoring sensor.

The long-distance distributed optical fiber spatial attitude monitoring sensor uses four single-mode strain optical fibers 1 as strain sensing units and arranges them in the polymer composite rib 4 at intervals of 90 degrees in the circumferential direction during the thermoforming process of the polymer composite rib 4 1.5 mm away from the outer circumference of the polymer composite rib 4; at the same time, a single-mode temperature optical fiber 2 with a loose tube and a 7-wire steel strand 3 with a diameter of 2 mm are laid at the center of the polymer composite rib 4 , the outlet end is connected to the optical fiber junction box 5, and the optical fibers in the optical fiber junction box 5 are connected to each other to form an optical path and welded with the transmission cable 6, wherein the diameter of the polymer composite rib 4 can be 5-8mm according to the monitoring requirements. A single-mode temperature optical fiber 2 with a loose sheath is used as a temperature sensing unit, and a 7-wire steel strand 3 with a diameter of 2mm is a strengthening unit of the sensor.

Fig. 3 is a working schematic diagram of the ith micro-segment of the long-distance distributed optical fiber space attitude monitoring sensor.

The long-distance distributed optical fiber space attitude monitoring sensor is arranged in the structure and deforms cooperatively with the structure. In figure (a), the length of the i-th micro-segment of the sensor is L _i , and the diameter of the sensor is D. Figure (b) is a schematic diagram of the ab section of the sensor when the i-th micro-segment of the sensor is bent. The strains measured in real time at the i-th measuring point of the four strain sensing units are ε _ai , ε _bi , ε _ci , and ε _di . From the deformation geometric relationship, we can know that:

L _i =ρ _abi ×α _abi (1)

In formulas (1)-(3), k _abi , ρ _abi , and α _abi are the curvature, deflection, and central angle corresponding to the arc when the _microunit deforms, respectively; Deformation amount.

As deduced above, the curvature k _cdi of the cd profile when the i-th micro-segment of the sensor is bent, the derivation result is as follows:

In the formula, ρ _cdi is the deflection of the cd profile when the ith micro-segment of the sensor is bent.

In the actual engineering of the long-distance distributed optical fiber space attitude monitoring sensor, when the ambient temperature changes, it is also necessary to perform temperature correction on the test strain of the four strain sensing units. The temperature sensitivity coefficient of the temperature sensing unit in the sensor is K _T , and the strain sensitivity coefficient of the strain sensing unit is K _ε . In figure (b), the temperature measurement point increment of the i-th micro-element of the sensor is ΔT _i , then the Brillouin frequency shift increment Δf _ti =ΔT _i ×K _T , the strain sensing unit in the sensor simultaneously senses the temperature and stress load, The overall Brillouin frequency shift increment is ΔF _i analyzed by the fiber optic Brillouin demodulator without distinction, then the stress-induced Brillouin frequency shift increment is: Δf _εi = ΔF _i -Δf _ti , and the corresponding strain Increment (sensing strain value of the sensing unit) ε=Δf _εi /K _ε , substituting into formula (3) and formula (4) can get the curvature value after temperature correction.

The long-distance distributed optical fiber space attitude monitoring sensor monitors the curvature values k _abi , k _cdi in two directions of the sensor, and converts the curvatures in the two directions into space curvature According to the above derivation process, the spatial curvature at any measuring point position of the sensor can be obtained i=1-n, n is the number of strain measuring points of the sensor, and then based on the mathematical differential geometric relationship, using the spatial curvature information and the distance of the sensor measuring point to reconstruct the spatial attitude of the sensor, that is, the coordinates of the i-th measuring point of the known sensor (x _i , y _i , z _i ) and the curvature components k _abi , k _cdi of the i-th point, based on the geometric deformation relationship of the sensor, the coordinates of the (i+1)th measuring point (x _i+1 , y _{i +1} , z _i+1 ), and then reconstruct the entire position information of the sensor.

In the engineering application of the long-distance distributed optical fiber attitude monitoring sensor and engineering implementation method, before the space strain curvature is converted, the strain value of the sensing unit in the sensor needs to be preprocessed in addition to the temperature correction, and the strain value temperature correction is completed. Afterwards, the difference is made with the initial strain value of the sensor, and the region with a significant increase in strain is segmented, and then the above attitude reconstruction is performed in segments.

Claims (4)

1. A long-distance distributed optical fiber spatial attitude monitoring sensor is characterized in that, the long-distance distributed optical fiber spatial attitude monitoring sensor comprises four single-mode strain optical fibers (1), a single-mode optical fiber with a loose sheath Mode temperature optical fiber (2), a bundle of seven-filament steel strands (3), polymer composite ribs (4), two optical fiber distribution boxes (5) and two transmission optical cables (6); The single-mode strained optical fiber (1), single-mode temperature optical fiber (2) and seven-filament steel strand (3) are arranged inside the polymer composite rib (4) during the thermoforming process of the polymer composite rib (4); The four single-mode strained optical fibers (1) are circumferentially arranged in the polymer composite ribs (4) at intervals of 90 degrees, 1.5 mm from the outer circumference of the polymer composite ribs (4), and each single-mode strained optical fiber (1 ) as the strain sensing unit in the sensor, used for strain testing and strain-curvature attitude reconstruction in the four directions of structure up, down, left, and right; a single-mode temperature optical fiber (2) and a bundle of seven The wire steel strand (3) is arranged in the middle of the polymer composite rib (4), and the single-mode temperature optical fiber (2) is located on the center line; the single-mode temperature optical fiber (2) is used as the temperature sensing unit in the sensor. It is used to test the ambient temperature and the temperature compensation of the 4 strain sensing units; the seven-wire steel strand (3) is used to enhance the tensile and shear strength of the sensor; the two ends of the polymer composite rib (4) It is connected with the optical fiber distribution box (5), and the optical fibers in the optical fiber distribution box (5) are fused with each other to form an optical path, and connected with the transmission optical cable (6); The inner diameter of the polymer composite rib (4) is 5-8mm. 2. A kind of long-distance distributed optical fiber space posture monitoring sensor according to claim 1, is characterized in that, the polymer material in the described polymer composite rib (4) is polyethylene, polypropylene, after thermoforming In the process, polymer materials are combined with glass fibers. 3. A long-distance distributed optical fiber spatial attitude monitoring sensor according to claim 1 or 2, characterized in that the diameter of the seven-wire steel strand (3) is 2mm. 4. The engineering realization method of a kind of long-distance distributed optical fiber space posture monitoring sensor described in claim 1 or 2 or 3, is characterized in that the following steps: In the first step, long-distance distributed optical fiber spatial attitude monitoring sensors are deployed in the structure, and the structure cooperates with the deformation; In the second step, the four single-mode strain optical fibers (1) in the long-distance distributed optical fiber space attitude monitoring sensor measure the initial strain values in four directions of the i-th measuring point in real time; In the third step, the single-mode temperature optical fiber (2) with a loose sheath performs temperature correction on the initial strain values tested by the four single-mode strain optical fibers (1), and the corrected strain values are differentiated from the initial strain values of the sensor to obtain Segmentally calibrate the strain mutation region, based on the strain-curvature relationship, segmentally reconstruct the spatial attitude of the sensor.