Inhaul cable based on optical fiber technology and cable force measuring method thereof

Abstract

The invention discloses an inhaul cable based on an optical fiber technology and a cable force measuring method thereof, and the method comprises the steps: obtaining the monitoring data and state data of the inhaul cable, carrying out the temperature compensation of the monitoring data, obtaining a temperature compensation wavelength, correcting the temperature compensation wavelength, obtaining a first correction wavelength, correcting the first correction wavelength, obtaining a second correction wavelength, and obtaining the cable force of the inhaul cable. Determining a first inhaul cable force according to the second correction wavelength, constructing an inhaul cable force measurement model, optimizing the inhaul cable force measurement model according to the cable force error, and inputting monitoring data and state data of a to-be-measured inhaul cable into the optimized inhaul cable force measurement model to obtain a cable force measurement result. The inhaul cable based on the optical fiber technology is installed on a structure to obtain light wave signals, the light signals are processed, the cable force of the inhaul cable is calculated, and the cable force of the inhaul cable is measured in the using process of the inhaul cable based on the optical fiber technology.

Description

Technical Field

[0001] The invention relates to the field of nondestructive testing, and in particular to a cable and a cable force measurement method based on optical fiber technology. Background Art

[0002] As a key load-bearing component in large bridges and tall structures, accurate measurement of cable force is crucial for the safety monitoring and assessment of the structure. Traditional cable force measurement methods have problems such as measurement accuracy being greatly affected by the environment and complex installation and maintenance. Fiber optic technology, as an emerging sensing technology, has the characteristics of small size, light weight, and strong anti-electromagnetic interference. These excellent characteristics have promoted the development of cable force measurement technology based on fiber optic technology, which is of great significance for the health monitoring of major structures.

[0003] Fiber Bragg Grating (FBG) sensors are strain and temperature cross-sensitive monitoring elements. In practical applications, there are still problems such as FBG fragility and easy breakage, and low monitoring range. It is necessary to innovate the protection method and layout of FBG. In addition, the accurate FBG wavelength-cable force relationship is the key to effective cable force measurement, but the cable force measurement is not only affected by temperature changes, but also by environmental noise, wind speed, structural deformation, cable scale and other factors. The above factors have difficulties in data post-processing, such as complex data types, large data volume and complex calculation process. Combined with machine learning technology to capture the complex relationship between monitoring data, state data and real cable force, it can accurately predict the cable force. Therefore, a cable and its cable force measurement method based on optical fiber technology is designed to overcome the shortcomings of the detection accuracy of the existing cable force measurement device and method, so as to improve the accuracy and efficiency of cable force measurement, and provide strong support for the structural health monitoring of large bridges and tall structures. Summary of the invention

[0004] The object of the present invention is to provide a cable and a cable force measurement method based on optical fiber technology.

[0005] To achieve the above object, the present invention is implemented according to the following technical solutions:

[0006] The present invention comprises the following steps:

[0007] Acquire monitoring data and status data of the cable, and pre-process the monitoring data and the status data; the status data includes environmental status data and structural status data;

[0008] Performing temperature compensation on the monitoring data to obtain a temperature compensation wavelength, obtaining an environmental impact factor according to the environmental state data, and correcting the temperature compensation wavelength to obtain a first corrected wavelength;

[0009] Determine a scale influence coefficient, determine a scale influence factor according to the structural state data and the scale influence coefficient, and correct the first correction wavelength to obtain a second correction wavelength;

[0010] Determine a first cable force according to the second corrected wavelength, and construct a cable force measurement model according to the first cable force, the environmental influencing factor, and the scale influencing factor;

[0011] The cable force measurement model is optimized according to the cable force error, and the monitoring data and status data of the cable to be measured are input into the optimized cable force measurement model to obtain the cable force measurement result.

[0012] Furthermore, the method of performing temperature compensation on the monitoring data to obtain a temperature compensation wavelength includes:

[0013] The calibration experiment of the single-rib force measuring element is carried out to control the stress and temperature changes of the main single-rib force measuring element and the temperature change of the auxiliary single-rib force measuring element to obtain the test calibration data. The binary surface fitting equation of strain and temperature is solved according to the test calibration data. The expression is:

[0014]

[0015] b=(H T +H) -1 ·H T ·T

[0016] where ε ij is the two-dimensional surface fitting equation of strain, T ij is the binary surface fitting equation of temperature, and the corresponding state is ε ij or T ij When taking the calibration value, the wavelength change of the main single-rib force measuring element is Wavelength variation of auxiliary single-rib force measuring element i is the set stress state, j is the set temperature state, a=[a0,a1,a2,a3,a4,a5] T 、b=[b0,b1,b2,b3,b4,b5] T is the constant coefficient of the bivariate surface fitting equation, is the calibration point data matrix, k ε is the strain sensitivity coefficient, k T is the temperature sensitivity coefficient;

[0017] The main single-rib force measuring element is used to make the stressed cable, and the auxiliary single-rib force measuring element is used to make the temperature compensation element. The strain and temperature values ​​are calculated according to the binary surface fitting equation of strain and temperature and the wavelength change monitoring value. The strain and temperature data are fitted and reconstructed according to the optical fiber sensing principle to obtain the temperature compensation wavelength.

[0018] Further, the method for obtaining the first corrected wavelength includes:

[0019] The state data is input into the environmental impact function to obtain the environmental impact factor, and the temperature compensation wavelength is corrected by the environmental impact factor to obtain the first corrected wavelength. The expression is:

[0020]

[0021] Effect1 is the environmental impact factor, w1, w2, and w3 are the weights of the environmental impact factors, N0 is the environmental noise limit, N1 is the current environmental noise, a is the bridge vibration acceleration, v is the bridge vibration velocity, and w is the wind speed. is the angle between the wind direction and the longitudinal direction of the bridge, λ1 is the first corrected wavelength, λ0 is the initial wavelength of the optical fiber, and λ w is the temperature compensation wavelength.

[0022] Furthermore, the method for obtaining the scale influence coefficient includes:

[0023] The scale influence coefficient includes the spiral angle influence coefficient and the stress level influence coefficient;

[0024] The static tensile test and finite element simulation test of the single-rib force measuring element were carried out respectively, and the stress level of the single-rib force measuring element and the helical winding angle of the optical fiber were adjusted to obtain the tensile test data and simulation data. The tensile test data and simulation data were fitted to obtain the helical angle influence coefficient and the stress level influence coefficient, and the expression is:

[0025]

[0026] where δ θ is the helical angle influence coefficient, c1, c2, c3, c4 are constant coefficients obtained by data fitting, θ is the fiber winding helical angle, δ σ is the stress level influence coefficient, is the fiber stress, E g is the elastic modulus of the optical fiber, K εg is the strain sensitivity of the optical fiber, c5 is the proportionality coefficient, and c6 is the nonlinear index.

[0027] Further, the method for obtaining the second corrected wavelength includes:

[0028] According to the structural status data, the user utilization coefficient and the size coefficient are calculated respectively. According to the scale influence coefficient, the user utilization coefficient and the size coefficient, the use scale influence factor is determined. The expression is:

[0029]

[0030] Effect2=[h1(δ θ +δ σ )+h2δ use ]cos(2πδ size )

[0031] where δ use is the user usage coefficient, δ size is the size coefficient, Effect2 is the usage scale influence factor, d1 and d2 are the user usage coefficient weights, d3 is the size coefficient weight, h1 and h2 are the usage scale influence factor weights, M 1use is the number of fiber optic interrogator channels used, M 1max M is the maximum number of channels of the fiber optic interrogator. 2use is the number of sensor connections in a single channel, M 2max is the maximum number of sensors connected in a single channel, L max is the access optical fiber length, L use is the length of the monitoring optical fiber segment, r g is the fiber radius, r a is the groove radius, r m is the radius of the base rib;

[0032] The second corrected wavelength is obtained by correcting the first corrected wavelength using the scale influence factor, and the expression is:

[0033]

[0034] Wherein λ2 is the second corrected wavelength, λ1 is the first corrected wavelength, and λ0 is the initial wavelength.

[0035] Furthermore, the method for determining the first cable force according to the second corrected wavelength includes:

[0036] Determine the proportional relationship between the optical fiber strain at the unglued fixed part of the spiral groove of the matrix reinforcement and the reinforcement surface strain, the expression is:

[0037]

[0038] a=1+L2 / 2L1

[0039]

[0040] Where β is the strain transfer rate, which indicates the proportional relationship between the strain of the unfixed optical fiber in the middle and the strain on the surface of the reinforcement, a is the gauge ratio coefficient, L2 is the optical fiber length in the middle gauge section, L1 is the optical fiber length at the fixed end, k is the material coefficient, G j is the shear modulus of the adhesive at the fixed end, r j is the adhesive radius;

[0041] The first cable force is determined according to the strain transfer rate, optical fiber output wavelength, cable material and size parameters. The expression is:

[0042]

[0043] Where F1 is the first cable force, E m is the elastic modulus of the reinforcement, A c is the cross-sectional area of ​​the cable, n is the number of single-reinforcement force measuring elements in the cable, λ 2i is the second corrected wavelength of the i-th single-tendon force measuring element in the cable, λ 0i is the initial wavelength of the i-th single-tendon force measuring element in the cable, μ is the cable structural coefficient, d i is the distance from the center of the i-th single-reinforcement force measuring element in the cable to the center of the cable, R is the radius of the cable, and A c is the cross-sectional area of ​​the cable, A m is the cross-sectional area of ​​the single-rib force measuring element.

[0044] Furthermore, the method for constructing the cable force measurement model includes:

[0045] The cable force deviation is calculated based on the measured cable force and the first cable force, and the cable force deviation, measured cable force, first cable force, scale influencing factor and environmental influencing factor are combined into a comprehensive data set. The comprehensive data set is divided into a training set and a test set in a ratio of 7:3 using the random forest algorithm.

[0046] A cable force measurement model is constructed based on the comprehensive data set, and the cable force measurement model includes an input layer, a base model layer, a strategy layer and an output layer;

[0047] The base model layer is used to predict the cable force according to the data rules of the comprehensive data set. The base models include linear regression model, decision tree model and BP neural network model.

[0048] The linear regression model is responsible for capturing the linear relationship between the input data characteristics and the measured cable force, and the input characteristics are standardized to ensure the stability of the model;

[0049] The decision tree model is responsible for capturing the nonlinear relationship between the input data characteristics and the measured cable forces. The maximum depth is set to prevent overfitting, and cross-validation is used to determine the optimal depth.

[0050] The BP neural network model is responsible for capturing the complex nonlinear relationship between the input data features and the measured cable forces. It uses the ReLU activation function, dropout to prevent overfitting, and the early stopping method to determine the number of training rounds.

[0051] The strategy layer is used to integrate the output of the base model layer, perform feature engineering and model fusion, and output the cable force prediction results;

[0052] The particle swarm optimization algorithm is used to optimize the hyperparameters of the cable force measurement model according to the error between the cable force prediction results of the test data and the measured cable force.

[0053] Furthermore, the method for optimizing the cable force measurement model according to the cable force error includes:

[0054] Initialize the population size N and the maximum number of iterations T, and perform chaotic mapping on the search sub-population. The expression is:

[0055]

[0056] where x t is the particle position after chaos mapping, x t0 is the particle position before chaotic mapping, q is a chaotic random number in [0,1], and p is 0.4;

[0057] Calculate the fitness of the particle's position, set the fitness threshold γ, and calculate the contraction-expansion coefficient based on the fitness value difference. The expression is:

[0058]

[0059] in is the contraction-expansion coefficient, is the maximum contraction-expansion coefficient, is the minimum contraction-expansion coefficient, T is the maximum number of iterations, t is the current number of iterations, rand(·) is the random perturbation, and Fitness i,t is the fitness of particle i at the corresponding position in the tth iteration, g is the fitness of the position of the global optimal particle;

[0060] Update the individual optimal position p of the particle i,t+1 , the global optimal position g t+1 and the average optimal position m best , update the particle position, the expression is:

[0061]

[0062] where x i,t+1 is the position update of particle i at the t+1th iteration, x i,t is the position of particle i at the tth iteration, ζ and z are random numbers in [0,1], and v is the adjustment parameter in [0,1];

[0063] Determine whether the particle has crossed the boundary. When the particle crosses the boundary, perform chaotic boundary mutation. The expression is:

[0064]

[0065] where x' i,t+1 is the position of particle i after the position of particle i crosses the boundary at the t+1th iteration after the chaotic boundary mutation, maxx t+1 is the upper boundary of the particle swarm in the t+1th iteration, min x t+1 is the lower boundary of the particle swarm in the t+1th iteration, is the chaotic map random number of the t+1th iteration, is the random number of the chaotic map of the tth iteration, s = 0.2;

[0066] Calculate the cable force error of the search particle, the expression is:

[0067]

[0068] Error i,t+1 is the error of particle i at the t+1th iteration, o is a random number in [0,1], F i ' ,t+1 is the cable force prediction result of particle i at iteration t+1, F i is the measured cable force of particle i, χ is the flight coefficient, τ is the attenuation factor, is the inertia weight, w is the modulation constant, is the standard deviation of the first normally distributed random number k, is the standard deviation of the second normal distribution random number l, is the flight parameter;

[0069] Iterate continuously until the cable force error is minimized or the maximum number of iterations is reached;

[0070] The monitoring data and status data of the cable to be measured are input into the optimized cable force measurement model to obtain the cable force measurement results.

[0071] On the other hand, a cable based on optical fiber technology includes: ordinary reinforcement material, a single-reinforcement force measuring element and HDPE protective glue; the HDPE protective glue is wrapped around the outside of the ordinary reinforcement material and the single-reinforcement force measuring element; the single-reinforcement force measuring element includes an optical fiber, an adhesive fixing end and a base reinforcement material; a spiral groove is provided on the base reinforcement material; the optical fiber is wound and arranged inside the spiral groove; the optical fiber is fixed inside the spiral groove in the form of a long gauge length through the adhesive fixing end; the optical fiber between the adhesive fixing ends is engraved with a grating area; there are multiple grating areas on the optical fiber of the single-reinforcement force measuring element; the grating areas are connected in series; the port of the optical fiber is connected to an external fiber grating demodulator.

[0072] The beneficial effects of the present invention are:

[0073] The present invention is a cable and a cable force measurement method based on optical fiber technology. Compared with the prior art, the present invention has the following technical effects:

[0074] The present invention provides a cable force measurement method based on optical fiber technology. By temperature compensation, constructing environmental influence factors and using scale influence factors, correcting wavelengths, calculating cable forces, constructing models, and optimizing model steps, the efficiency and accuracy of cable force measurement based on optical fiber technology can be improved. The cable force measurement is made intelligent, which can greatly save resources, and can realize the measurement of the cable force of the cable to be measured. The cable force measurement of the cable to be measured can be performed quickly and in real time with high accuracy, providing strong technical support for the cable force measurement of the cable, which is of great significance to the development of structural health monitoring and safety assessment in the field of civil engineering.

[0075] The present invention provides a cable based on optical fiber technology. When manufacturing a single-reinforcement force measuring element, a spiral groove is provided on a base reinforcement material and the optical fiber is arranged inside the spiral groove, thereby effectively protecting the optical fiber and improving the survival rate of the optical fiber in the single-reinforcement force measuring element. The optical fiber is spirally wound and arranged with a long gauge length, thereby reducing the strain sensitivity of the optical fiber and improving the monitoring range of the single-reinforcement force measuring element, thereby facilitating the development of structural monitoring of large-span and high-stress bridge cables. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] Figure 1 A flowchart of the steps of a cable force measurement method based on optical fiber technology of the present invention;

[0077] Figure 2 A schematic diagram of a cross-sectional view of a cable based on optical fiber technology provided by the present invention;

[0078] Figure 3 A schematic diagram of a single-reinforcement force measuring element of a cable based on optical fiber technology provided by the present invention;

[0079] Figure 4 A schematic diagram of the deployment of optical fibers of a single-reinforcement force measuring element of a cable based on optical fiber technology provided by the present invention;

[0080] Figure 5 A schematic cross-sectional view of a single-reinforcement force measuring element of a cable based on optical fiber technology provided by the present invention;

[0081] In the figure: 1-ordinary reinforcement; 2-single reinforcement force measuring element; 3-adhesive fixing end; 4-spiral groove; 5-optical fiber; 6-base reinforcement; 7-HDPE protective glue; 8-grid area. DETAILED DESCRIPTION

[0082] The present invention is further described below by means of specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention but are not intended to limit the present invention.

[0083] The present invention provides a cable and a cable force measurement method based on optical fiber technology, comprising the following steps:

[0084] like Figure 1 As shown, in this embodiment, a cable force measurement method based on optical fiber technology includes:

[0085] Acquire monitoring data and status data of the cable, and pre-process the monitoring data and the status data; the status data includes environmental status data and structural status data;

[0086] Performing temperature compensation on the monitoring data to obtain a temperature compensation wavelength, obtaining an environmental impact factor according to the environmental state data, and correcting the temperature compensation wavelength to obtain a first corrected wavelength;

[0087] Determine a scale influence coefficient, determine a scale influence factor according to the structural state data and the scale influence coefficient, and correct the first correction wavelength to obtain a second correction wavelength;

[0088] Determine a first cable force according to the second corrected wavelength, and construct a cable force measurement model according to the first cable force, the environmental influencing factor, and the scale influencing factor;

[0089] The cable force measurement model is optimized according to the cable force error, and the monitoring data and status data of the cable to be measured are input into the optimized cable force measurement model to obtain the cable force measurement result.

[0090] In this embodiment, the method of performing temperature compensation on the monitoring data to obtain a temperature compensation wavelength includes:

[0091] The calibration experiment of the single-rib force measuring element is carried out to control the stress and temperature changes of the main single-rib force measuring element and the temperature change of the auxiliary single-rib force measuring element to obtain the test calibration data. The binary surface fitting equation of strain and temperature is solved according to the test calibration data. The expression is:

[0092]

[0093] b=(H T +H) -1 ·H T ·T

[0094] where ε ij is the two-dimensional surface fitting equation of strain, T ij is the binary surface fitting equation of temperature, and the corresponding state is ε ij or T ij When taking the calibration value, the wavelength change of the main single-rib force measuring element is Wavelength variation of auxiliary single-rib force measuring element i is the set stress state, j is the set temperature state, a=[a0,a1,a2,a3,a4,a5] T 、b=[b0,b1,b2,b3,b4,b5] T is the constant coefficient of the bivariate surface fitting equation, is the calibration point data matrix, k ε is the strain sensitivity coefficient, k T is the temperature sensitivity coefficient;

[0095] The main single-rib force measuring element is used to make the stressed cable, and the auxiliary single-rib force measuring element is used to make the temperature compensation element. The strain and temperature values ​​are calculated based on the strain and temperature binary surface fitting equation and the wavelength change monitoring value. The strain and temperature data are fitted and reconstructed according to the optical fiber sensing principle to obtain the temperature compensation wavelength.

[0096] In the actual evaluation, the monitoring data of the single-reinforcement force measuring elements in two cables at different positions of a bridge are collected (the data of one of the sensors is taken for the main single-reinforcement force measuring element): Cable A: main single-reinforcement force measuring element (initial wavelength 1545.1110nm, output wavelength 1549.8258nm), auxiliary single-reinforcement force measuring element (initial wavelength 1545.0154nm, output wavelength 1545.0043nm); Cable B: main single-reinforcement force measuring element (initial wavelength 1544.9399nm, output wavelength 1548.7103nm), auxiliary single-reinforcement force measuring element (initial wavelength 1545.1024nm, output wavelength 1545.1018nm);

[0097] According to the binary surface fitting equation obtained from the calibration experiment, the temperature compensation wavelength of the main single-reinforcement force measuring element of cable A is 1549.8298nm, and the temperature compensation wavelength of the main single-reinforcement force measuring element of cable B is 1548.7389nm through fitting and reconstruction through monitoring data.

[0098] In this embodiment, the method for obtaining the first corrected wavelength includes:

[0099] The state data is input into the environmental impact function to obtain the environmental impact factor, and the temperature compensation wavelength is corrected by the environmental impact factor to obtain the first corrected wavelength. The expression is:

[0100]

[0101] Effect1 is the environmental impact factor, w1, w2, and w3 are the weights of the environmental impact factors, N0 is the environmental noise limit, N1 is the current environmental noise, a is the bridge vibration acceleration, v is the bridge vibration velocity, and w is the wind speed. is the angle between the wind direction and the longitudinal direction of the bridge, λ1 is the first corrected wavelength, λ0 is the initial wavelength of the optical fiber, and λw is the temperature compensation wavelength;

[0102] In the actual evaluation, the environmental data of a bridge were obtained: the machine working environment noise limit is 55dB, the current environmental noise is 68dB, and the bridge vibration acceleration is 0.5m / s 2 , bridge vibration speed 6mm / s, wind speed 10m / s, angle between wind direction and bridge longitudinal direction 45°;

[0103] Taking w1=2, w2=0.8, w3=0.8, the environmental impact factor Effect1=0.6351 is calculated, and the first corrected wavelengths of cable A and cable B are calculated to be 1549.7052nm and 1548.6386nm respectively.

[0104] In this embodiment, the method for obtaining the scale influence coefficient includes:

[0105] The scale influence coefficient includes the spiral angle influence coefficient and the stress level influence coefficient;

[0106] The static tensile test and finite element simulation test of the single-rib force measuring element were carried out respectively, and the stress level of the single-rib force measuring element and the helical winding angle of the optical fiber were adjusted to obtain the tensile test data and simulation data. The tensile test data and simulation data were fitted to obtain the helical angle influence coefficient and the stress level influence coefficient, and the expression is:

[0107]

[0108] where δ θ is the helical angle influence coefficient, c1, c2, c3, c4 are constant coefficients obtained by data fitting, θ is the fiber winding helical angle, δ σ is the stress level influence coefficient, is the fiber stress, E g is the elastic modulus of the optical fiber, K εg is the strain sensitivity of the optical fiber, c5 is the proportionality coefficient, and c6 is the nonlinear index;

[0109] In the actual evaluation, the helix angle of the optical fiber in the single-rib force measuring element 1 of cable A and cable B is 15°, c1=0.01, c2=0.05, c3=0.1, c4=0.1, and the helix angle influence coefficient is 3.1 calculated according to the above formula; c5=0.5, c6=1.2, the optical fiber elastic modulus is 72 GPa, the strain sensitivity coefficient is 1.2025 pm / με, and the stress level influence coefficient is -1.4673 calculated according to the above formula.

[0110] In this embodiment, the method for obtaining the second corrected wavelength includes:

[0111] According to the structural status data, the user utilization coefficient and the size coefficient are calculated respectively. According to the scale influence coefficient, the user utilization coefficient and the size coefficient, the use scale influence factor is determined. The expression is:

[0112]

[0113] Effect2=[h1(δ θ +δ σ )+h2δ use ]cos(2πδ size )

[0114] where δ use is the user usage coefficient, δ size is the size coefficient, Effect2 is the usage scale influence factor, d1 and d2 are the user usage coefficient weights, d3 is the size coefficient weight, h1 and h2 are the usage scale influence factor weights, M 1use is the number of fiber optic interrogator channels used, M 1max M is the maximum number of channels of the fiber optic interrogator. 2use is the number of sensor connections in a single channel, M 2max is the maximum number of sensors connected in a single channel, L max is the access optical fiber length, L use is the length of the monitoring optical fiber segment, r g is the fiber radius, r a is the groove radius, r m is the radius of the base rib;

[0115] The second corrected wavelength is obtained by correcting the first corrected wavelength using the scale influence factor, and the expression is:

[0116]

[0117] Where λ2 is the second corrected wavelength, λ1 is the first corrected wavelength, and λ0 is the initial wavelength;

[0118] In the actual evaluation, the maximum number of channels of the fiber Bragg grating demodulator is 16, the current number of channels in use is 16, the maximum number of sensor connections in a single channel is 30, the current number of sensor connections in a single channel is 10, the monitoring section fiber length is 20.70m, the access fiber length is 25m, d1=d2=0.1, and the user utilization coefficient calculated according to the above formula is 0.3522; d3=5, the fiber radius is 62.5μm, the groove radius is 1mm, and the matrix rib radius is 3.5mm. The size coefficient calculated according to the above formula is 0.9845;

[0119] Taking h1=h2=0.5, the scale influence factor is calculated according to the above formula as 0.9877. Substituting the scale influence coefficient, user usage coefficient and size coefficient into the formula, the second corrected wavelengths of cable A and cable B are calculated to be 1549.6386nm and 1548.6331nm respectively.

[0120] In this embodiment, the method for determining the first cable force according to the second corrected wavelength includes:

[0121] Determine the proportional relationship between the optical fiber strain at the unglued fixed part of the spiral groove of the matrix reinforcement and the reinforcement surface strain, the expression is:

[0122]

[0123] a=1+L2 / 2L1

[0124]

[0125] Where β is the strain transfer rate, which indicates the proportional relationship between the strain of the unfixed optical fiber in the middle and the strain on the surface of the reinforcement, a is the gauge ratio coefficient, L2 is the optical fiber length in the middle gauge section, L1 is the optical fiber length at the fixed end, k is the material coefficient, G j is the shear modulus of the adhesive at the fixed end, r j is the adhesive radius;

[0126] The first cable force is determined according to the strain transfer rate, optical fiber output wavelength, cable material and size parameters. The expression is:

[0127]

[0128] Where F1 is the first cable force, E m is the elastic modulus of the reinforcement, A c is the cross-sectional area of ​​the cable, n is the number of single-reinforcement force measuring elements in the cable, λ 2i is the second corrected wavelength of the i-th single-tendon force measuring element in the cable, λ 0i is the initial wavelength of the i-th single-tendon force measuring element in the cable, μ is the cable structural coefficient, d i is the distance from the center of the i-th single-reinforcement force measuring element in the cable to the center of the cable, R is the radius of the cable, and A c is the cross-sectional area of ​​the cable, A m is the cross-sectional area of ​​the single-rib force measuring element;

[0129] In the actual evaluation, the fiber length of the middle gauge section of the single-reinforcement force measuring element of cable A is 60 mm, and the fiber length of the adhesive fixed end is 40 mm. The fiber length of the middle gauge section of the single-reinforcement force measuring element of cable B is 120 mm, and the fiber length of the adhesive fixed end is 40 mm. The shear modulus of the adhesive is 1296 MPa, and the radius of the adhesive layer is 500 μm. The strain transfer rates of the single-reinforcement force measuring elements on cables A and B are calculated to be 78.54% and 72.10% respectively.

[0130] The elastic modulus of the reinforcement is 155.56 GPa, and the cross-sectional area of ​​the cable is 1423.93 mm 2 Three single-reinforcement force measuring elements are set in the cable, and 10 FBG sensors are set on each optical fiber. Combined with the FBG sensor data on the other single-reinforcement force measuring elements on cables A and B, the first cable forces of cables A and B are calculated to be 1075.91 kN and 943.56 kN respectively.

[0131] In this embodiment, the method for constructing the cable force measurement model includes:

[0132] The cable force deviation is calculated based on the measured cable force and the first cable force, and the cable force deviation, measured cable force, first cable force, scale influencing factor and environmental influencing factor are combined into a comprehensive data set. The comprehensive data set is divided into a training set and a test set in a ratio of 7:3 using the random forest algorithm.

[0133] A cable force measurement model is constructed based on the comprehensive data set, and the cable force measurement model includes an input layer, a base model layer, a strategy layer and an output layer;

[0134] The base model layer is used to predict the cable force according to the data rules of the comprehensive data set. The base models include linear regression model, decision tree model and BP neural network model.

[0135] The linear regression model is responsible for capturing the linear relationship between the input data characteristics and the measured cable force, and the input characteristics are standardized to ensure the stability of the model;

[0136] The decision tree model is responsible for capturing the nonlinear relationship between the input data characteristics and the measured cable forces. The maximum depth is set to prevent overfitting, and cross-validation is used to determine the optimal depth.

[0137] The BP neural network model is responsible for capturing the complex nonlinear relationship between the input data features and the measured cable forces. It uses the ReLU activation function, dropout to prevent overfitting, and the early stopping method to determine the number of training rounds.

[0138] The strategy layer is used to integrate the output of the base model layer, perform feature engineering and model fusion, and output the cable force prediction results; feature engineering uses polynomial feature expansion and PCA to improve the nonlinear expression and generalization capabilities of the model, and uses the Stacking integration method to input new features into the meta-learner for prediction. The meta-learner uses a logistic regression algorithm;

[0139] The particle swarm optimization algorithm is used to optimize the hyperparameters of the cable force measurement model according to the error between the cable force prediction results of the test data and the measured cable force.

[0140] In this embodiment, the method for optimizing the cable force measurement model according to the cable force error includes:

[0141] Initialize the population size N and the maximum number of iterations T, and perform chaotic mapping on the search sub-population. The expression is:

[0142]

[0143] where x t is the particle position after chaos mapping, x t0 is the particle position before chaotic mapping, q is a chaotic random number in [0,1], and p is 0.4;

[0144] Calculate the fitness of the particle's position, set the fitness threshold γ, and calculate the contraction-expansion coefficient based on the fitness value difference. The expression is:

[0145]

[0146] in is the contraction-expansion coefficient, is the maximum contraction-expansion coefficient, is the minimum contraction-expansion coefficient, T is the maximum number of iterations, t is the current number of iterations, rand(·) is the random perturbation, and Fitness i,t is the fitness of particle i at the corresponding position in the tth iteration, g is the fitness of the position of the global optimal particle;

[0147] Update the individual optimal position p of the particle i,t+1 , the global optimal position g t+1 and the average optimal position m best , update the particle position, the expression is:

[0148]

[0149] where x i,t+1 is the position update of particle i at the t+1th iteration, x i,tis the position of particle i at the tth iteration, ζ and z are random numbers in [0,1], and v is the adjustment parameter in [0,1];

[0150] Determine whether the particle has crossed the boundary. When the particle crosses the boundary, perform chaotic boundary mutation. The expression is:

[0151]

[0152] where x' i,t+1 is the position of particle i after the position of particle i crosses the boundary at the t+1th iteration after the chaotic boundary mutation, maxx t+1 is the upper boundary of the particle swarm in the t+1th iteration, min x t+1 is the lower boundary of the particle swarm in the t+1th iteration, is the chaotic map random number of the t+1th iteration, is the random number of the chaotic map of the tth iteration, s = 0.2;

[0153] Calculate the cable force error of the search particle, the expression is:

[0154]

[0155] Error i,t+1 is the error of particle i at the t+1th iteration, o is a random number in [0,1], F i ' ,t+1 is the cable force prediction result of particle i at iteration t+1, F i is the measured cable force of particle i, χ is the flight coefficient, τ is the attenuation factor, is the inertia weight, w is the modulation constant, is the standard deviation of the first normally distributed random number k, is the standard deviation of the second normal distribution random number l, is the flight parameter;

[0156] Iterate continuously until the cable force error is minimized or the maximum number of iterations is reached;

[0157] Input the monitoring data and status data of the cable to be measured into the optimized cable force measurement model to obtain the cable force measurement result;

[0158] In the actual evaluation, the measured cable forces of cable A and cable B are 960 kN and 890 kN respectively. The cable force errors calculated by combining the first cable force are 12.07% and 6.02% respectively. The cable force measurement model is optimized according to the cable force error and iterated continuously until the cable force error is less than 3%. The monitoring data and status data of the cables to be measured are input into the optimized cable force measurement model to obtain the cable force measurement results of cable A and cable B, which are 988.32 kN and 914.65 kN respectively.

[0159] like Figures 2 to 5 As shown, in this embodiment, a cable based on optical fiber technology includes: ordinary reinforcement material 1, single reinforcement force measuring element 2 and HDPE protective glue 7; the HDPE protective glue 7 is wrapped around the outside of the ordinary reinforcement material 1 and the single reinforcement force measuring element 2; the single reinforcement force measuring element 2 includes an optical fiber 5, an adhesive fixing end 3 and a base reinforcement material 6; a spiral groove 4 is provided on the base reinforcement material 6; the optical fiber 5 is wound and arranged inside the spiral groove 4; the optical fiber 5 is fixed inside the spiral groove 4 in the form of a long gauge length through the adhesive fixing end 3; the optical fiber 5 between the adhesive fixing ends 3 is engraved with a grating area 8; a plurality of grating areas 8 are engraved on the optical fiber 5 of the single reinforcement force measuring element 2; the grating areas 8 are connected in series; the port of the optical fiber 5 is connected to an external fiber grating demodulator.

[0160] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A cable force measurement method based on optical fiber technology, characterized in that: The following steps are involved: S1, obtaining monitoring data and status data of the cable, and preprocessing the monitoring data and the status data; the status data includes environmental status data and structural status data; S2, performing temperature compensation on the monitoring data to obtain a temperature compensation wavelength, obtaining an environmental impact factor according to the environmental state data, and correcting the temperature compensation wavelength to obtain a first corrected wavelength; S3, determining a scale influence coefficient, determining a scale influence factor according to the structural state data and the scale influence coefficient, and correcting the first correction wavelength to obtain a second correction wavelength; S4, determining a first cable force according to the second corrected wavelength, and constructing a cable force measurement model according to the first cable force, the environmental influencing factor and the scale influencing factor; S5. Optimizing the cable force measurement model according to the cable force error, and inputting the monitoring data and status data of the cable to be measured into the optimized cable force measurement model to obtain the cable force measurement result.

2. According to claim 1, a cable force measurement method based on optical fiber technology is characterized in that: The method for performing temperature compensation on the monitoring data to obtain a temperature compensation wavelength comprises: The calibration experiment of the single-rib force measuring element is carried out to control the stress and temperature changes of the main single-rib force measuring element and the temperature change of the auxiliary single-rib force measuring element to obtain the test calibration data. The binary surface fitting equation of strain and temperature is solved according to the test calibration data. The expression is: where ε ij is the two-dimensional surface fitting equation of strain, T ij is the binary surface fitting equation of temperature, and the corresponding state is ε ij or T ij When taking the calibration value, the wavelength change of the main single-rib force measuring element is Wavelength variation of auxiliary single-rib force measuring element i is the set stress state, j is the set temperature state, a=[a0,a1,a2,a3,a4,a5] T 、b=[b0,b1,b2,b3,b4,b5] T is the constant coefficient of the bivariate surface fitting equation, is the calibration point data matrix, k ε is the strain sensitivity coefficient, k T is the temperature sensitivity coefficient; The main single-rib force measuring element is used to make the stressed cable, and the auxiliary single-rib force measuring element is used to make the temperature compensation element. The strain and temperature values ​​are calculated according to the binary surface fitting equation of strain and temperature and the wavelength change monitoring value. The strain and temperature data are fitted and reconstructed according to the optical fiber sensing principle to obtain the temperature compensation wavelength.

3. The method for measuring cable force based on optical fiber technology according to claim 1, characterized in that: The method for obtaining the first corrected wavelength comprises: The state data is input into the environmental impact function to obtain the environmental impact factor, and the temperature compensation wavelength is corrected by the environmental impact factor to obtain the first corrected wavelength. The expression is: Effect1 is the environmental impact factor, w1, w2, and w3 are the weights of the environmental impact factors, N0 is the environmental noise limit, N1 is the current environmental noise, a is the bridge vibration acceleration, v is the bridge vibration velocity, and w is the wind speed. is the angle between the wind direction and the longitudinal direction of the bridge, λ1 is the first corrected wavelength, λ0 is the initial wavelength of the optical fiber, and λ w is the temperature compensation wavelength.

4. According to claim 1, a cable force measurement method based on optical fiber technology is characterized in that: The method for obtaining the scale influence coefficient includes: The scale influence coefficient includes the spiral angle influence coefficient and the stress level influence coefficient; The static tensile test and finite element simulation test of the single-rib force measuring element were carried out respectively, and the stress level of the single-rib force measuring element and the helical winding angle of the optical fiber were adjusted to obtain the tensile test data and simulation data. The tensile test data and simulation data were fitted to obtain the helical angle influence coefficient and the stress level influence coefficient, and the expression is: where δ θ is the helical angle influence coefficient, c1, c2, c3, c4 are constant coefficients obtained by data fitting, θ is the fiber winding helical angle, δ σ is the stress level influence coefficient, is the fiber stress, E g is the elastic modulus of the optical fiber, K εg is the strain sensitivity of the optical fiber, c5 is the proportionality coefficient, and c6 is the nonlinear index.

5. The method for measuring cable force based on optical fiber technology according to claim 1, characterized in that: The method for obtaining the second corrected wavelength comprises: According to the structural status data, the user utilization coefficient and the size coefficient are calculated respectively. According to the scale influence coefficient, the user utilization coefficient and the size coefficient, the use scale influence factor is determined. The expression is: Effect2=[h1(δ θ +d σ )+h2δ use ]cos(2πδ size ) where δ use is the user usage coefficient, δ size is the size coefficient, Effect2 is the usage scale influence factor, d1 and d2 are the user usage coefficient weights, d3 is the size coefficient weight, h1 and h2 are the usage scale influence factor weights, M 1use is the number of fiber optic interrogator channels used, M 1max M is the maximum number of channels of the fiber optic interrogator. 2use is the number of sensor connections in a single channel, M 2max is the maximum number of sensors connected in a single channel, L max is the access optical fiber length, L use is the length of the monitoring optical fiber segment, r g is the fiber radius, r a is the groove radius, r m is the radius of the base rib; The second corrected wavelength is obtained by correcting the first corrected wavelength using the scale influence factor, and the expression is: Wherein λ2 is the second corrected wavelength, λ1 is the first corrected wavelength, and λ0 is the initial wavelength.

6. The method for measuring cable force based on optical fiber technology according to claim 1, characterized in that: The method for determining the first cable force according to the second corrected wavelength comprises: Determine the proportional relationship between the optical fiber strain at the unglued fixed part of the spiral groove of the matrix reinforcement and the reinforcement surface strain, the expression is: a=1+L2 / 2L1 Where β is the strain transfer rate, which indicates the proportional relationship between the strain of the unfixed optical fiber in the middle and the strain on the surface of the reinforcement, a is the gauge ratio coefficient, L2 is the optical fiber length in the middle gauge section, L1 is the optical fiber length at the fixed end, k is the material coefficient, G j is the shear modulus of the adhesive at the fixed end, r j is the adhesive radius; The first cable force is determined according to the strain transfer rate, optical fiber output wavelength, cable material and size parameters. The expression is: Where F1 is the first cable force, E m is the elastic modulus of the reinforcement, A c is the cross-sectional area of ​​the cable, n is the number of single-reinforcement force measuring elements in the cable, λ 2i is the second corrected wavelength of the i-th single-tendon force measuring element in the cable, λ 0i is the initial wavelength of the i-th single-tendon force measuring element in the cable, μ is the cable structural coefficient, d i is the distance from the center of the i-th single-reinforcement force measuring element in the cable to the center of the cable, R is the radius of the cable, and A c is the cross-sectional area of ​​the cable, A m is the cross-sectional area of ​​the single-rib force measuring element.

7. The method for measuring cable force based on optical fiber technology according to claim 1, characterized in that: The method for constructing the cable force measurement model comprises: The cable force deviation is calculated based on the measured cable force and the first cable force, and the cable force deviation, measured cable force, first cable force, scale influencing factor and environmental influencing factor are combined into a comprehensive data set. The comprehensive data set is divided into a training set and a test set in a ratio of 7:3 using the random forest algorithm. A cable force measurement model is constructed based on the comprehensive data set, and the cable force measurement model includes an input layer, a base model layer, a strategy layer and an output layer; The base model layer is used to predict the cable force according to the data rules of the comprehensive data set. The base models include linear regression model, decision tree model and BP neural network model. The linear regression model is responsible for capturing the linear relationship between the input data characteristics and the measured cable force, and the input characteristics are standardized to ensure the stability of the model; The decision tree model is responsible for capturing the nonlinear relationship between the input data characteristics and the measured cable forces. The maximum depth is set to prevent overfitting, and cross-validation is used to determine the optimal depth. The BP neural network model is responsible for capturing the complex nonlinear relationship between the input data features and the measured cable forces. It uses the ReLU activation function, dropout to prevent overfitting, and the early stopping method to determine the number of training rounds. The strategy layer is used to integrate the output of the base model layer, perform feature engineering and model fusion, and output the cable force prediction results; The particle swarm optimization algorithm is used to optimize the hyperparameters of the cable force measurement model according to the error between the cable force prediction results of the test data and the measured cable force.

8. The method for measuring cable force based on optical fiber technology according to claim 1, characterized in that: The method for optimizing the cable force measurement model according to the cable force error comprises: Initialize the population size N and the maximum number of iterations T, and perform chaotic mapping on the search sub-population. The expression is: where x t is the particle position after chaos mapping, x t0 is the particle position before chaotic mapping, q is a chaotic random number in [0,1], and p is 0.4; Calculate the fitness of the particle's position, set the fitness threshold γ, and calculate the contraction-expansion coefficient based on the fitness value difference. The expression is: in is the contraction-expansion coefficient, is the maximum contraction-expansion coefficient, is the minimum contraction-expansion coefficient, T is the maximum number of iterations, t is the current number of iterations, rand(·) is the random perturbation, and Fitness i,t is the fitness of particle i at the corresponding position in the tth iteration, g is the fitness of the position of the global optimal particle; Update the individual optimal position p of the particle i,t+1 , the global optimal position g t+1 and the average optimal position m best , update the particle position, the expression is: where x i,t+1 is the position update of particle i at the t+1th iteration, x i,t is the position of particle i at the tth iteration, ζ and z are random numbers in [0,1], and v is the adjustment parameter in [0,1]; Determine whether the particle has crossed the boundary. When the particle crosses the boundary, perform chaotic boundary mutation. The expression is: where x' i,t+1 is the position of particle i after the chaotic boundary mutation after the position of particle i crosses the boundary in the t+1th iteration, max x t+1 is the upper boundary of the particle swarm in the t+1th iteration, min x t+1 is the lower boundary of the particle swarm in the t+1th iteration, is the chaotic map random number of the t+1th iteration, is the random number of the chaotic map of the tth iteration, s = 0.2; Calculate the cable force error of the search particle, the expression is: Error i,t+1 is the error of particle i at the t+1th iteration, o is a random number in [0,1], F i ′ ,t+1 is the cable force prediction result of particle i at iteration t+1, F i is the measured cable force of particle i, χ is the flight coefficient, τ is the attenuation factor, is the inertia weight, w is the modulation constant, is the standard deviation of the first normally distributed random number k, is the standard deviation of the second normal distribution random number l, is the flight parameter; Iterate continuously until the cable force error is minimized or the maximum number of iterations is reached; The monitoring data and status data of the cable to be measured are input into the optimized cable force measurement model to obtain the cable force measurement results.

9. A cable based on optical fiber technology, used to perform the method according to any one of claims 1 to 8, characterized in that: include: Ordinary reinforcement material, single reinforcement force measuring element and HDPE protective glue; the HDPE protective glue is wrapped around the outside of the ordinary reinforcement material and the single reinforcement force measuring element; the single reinforcement force measuring element includes an optical fiber, an adhesive fixing end and a base reinforcement material; a spiral groove is provided on the base reinforcement material; the optical fiber is wound and arranged inside the spiral groove; the optical fiber is fixed inside the spiral groove in the form of a long gauge length through the adhesive fixing end; the optical fiber between the adhesive fixing ends is engraved with a grating area; there are multiple grating areas on the optical fiber of the single reinforcement force measuring element; the grating areas are connected in series; the port of the optical fiber is connected to an external fiber grating demodulator.

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