A method for correcting laser deflection meter measurement results based on a finite element model

Abstract

The application provides a laser deflection instrument measurement result correction method based on a finite element model, and belongs to the technical field of measurement instrument measurement result correction, which comprises the following steps: constructing a viscoelastic pavement model; calculating a deflection parameter measurement value Y of the laser deflection instrument on the viscoelastic pavement model; calculating a standard deflection parameter measurement value Y0 of a falling weight deflectometer on the viscoelastic pavement model; calculating deflection correction parameters ρ under the action of various environmental factors through the deflection parameter measurement value Y and the standard deflection parameter measurement value Y0; screening out m environmental condition influence factors which have a greater influence on the measurement result of the laser deflection instrument; establishing a laser deflection instrument measurement result correction model; and correcting the measurement result of the laser deflection instrument according to the laser deflection instrument measurement result correction model. The measurement result of the laser deflection instrument is corrected, the accuracy of the measurement result of the laser deflection instrument is improved, and it is ensured that the measurement result does not affect the accuracy of subsequent modulus back calculation.

Description

Technical Field

[0001] This invention belongs to the field of measurement result correction technology for measuring instruments, and relates to the correction technology of high-speed deflectometers, specifically a method for correcting measurement results of laser deflectometers based on a finite element model. Background Technology

[0002] Laser deflectometers are instruments specifically designed to measure minute road surface deflections. Their measurement accuracy is typically on the order of micrometers. Laser deflectometers are characterized by simple operation, high precision, stable readings, small size, and light weight, making them widely used in road surface deflection measurement.

[0003] However, laser deflectometers are currently mainly used on straight roads with good traffic conditions. Due to limitations in site conditions and vehicle operation, field testing with laser deflectometers is difficult, and the repeatability of test results is poor. This is especially true for viscoelastic pavements with minimal road deformation, where strict control of testing conditions cannot be guaranteed in field testing. Variations in environmental factors such as road surface temperature, pavement thickness, and vehicle speed lead to inaccurate laser deflectometer measurements, which in turn affect the accuracy of subsequent modulus calculations. Summary of the Invention

[0004] To address the problem described above where laser deflectometers produce inaccurate measurement results during viscoelastic pavement testing due to the inability to guarantee strict control of test conditions in field experiments, this invention proposes a laser deflectometer measurement result correction method based on a finite element model.

[0005] This invention quantifies the impact of external environmental factors such as vehicle speed, road surface temperature, surface layer thickness, and base layer thickness on the measurement results of a laser deflectometer. It utilizes a finite element modeling method to obtain finite element road deflection response models of pavement materials under different combined environmental conditions and non-uniformly distributed moving loads. Furthermore, it employs data fitting to match the correction coefficient model of the laser deflectometer, improving the accuracy of the measurement results and ensuring that the measurement results do not affect the accuracy of subsequent modulus back-calculation. The specific technical solution is as follows:

[0006] A method for correcting laser deflectometer measurement results based on a finite element model includes the following steps:

[0007] 1) Construct a viscoelastic pavement model;

[0008] 2) Under various environmental factors, a laser deflectometer was used to conduct a simulation test on the deflection of a viscoelastic pavement model, and the measured value Y of the deflection parameter of the viscoelastic pavement model was calculated.

[0009] 3) Using a falling weight deflectometer as the standard measuring instrument, the reference temperature of the falling weight deflectometer was set to 21.1℃ and the reference speed was set to 0km / h. A simulation test was conducted on the deflection of a viscoelastic pavement model using the falling weight deflectometer, and the standard deflection parameter Y0 of the viscoelastic pavement model was calculated. The deflection correction parameter ρ under various environmental factors was calculated using the deflection parameter Y and the standard deflection parameter Y0.

[0010] 4) Based on the measured value Y of the deflection parameter, the decision tree algorithm is used to screen out m environmental condition influencing factors that have a significant impact on the laser deflectometer measurement results;

[0011] 5) Using the deflection correction parameter ρ calculated in step 3) as the dependent variable and the environmental condition influencing factors selected in step 4) as the independent variables, calculate the fitting parameters A, a, b, c, and d using numerical fitting methods. Since the fitting parameters A, a, b, c, and d are dimensionless, establish a correction model for the laser deflectometer measurement results:

[0012]

[0013] In the formula, ζ is the correction coefficient; X1, X2, X3 and X4 are different environmental factors; v is the reference speed, km / h; T is the reference temperature, °C; H1 is the reference thickness of the surface layer, cm; H2 is the reference thickness of the base layer, cm;

[0014] 6) Correct the laser deflectometer measurement results using the correction model based on the laser deflectometer measurement results.

[0015] Further specifying, the calculation formula for the deflection correction parameter ρ under the influence of multiple environmental factors, obtained by calculating the deflection parameter measurement value Y and the standard deflection parameter measurement value Y0, is as follows:

[0016]

[0017] Further specifying, the various environmental factors include road surface temperature, vehicle speed, surface layer thickness, and base layer thickness, where X1 is vehicle speed in km / h; X2 is road surface temperature in °C; X3 is surface layer thickness in cm; and X4 is base layer thickness in cm.

[0018] Furthermore, the viscoelastic pavement model in step 1) is constructed based on the dynamic simulation test data of the surface material, the structural parameters of the finite element model of the surface material, and the parameters of the surface material.

[0019] Further specifying, the numerical fitting in step 5) is based on the principle of orthogonal distance regression and is performed using Excel spreadsheet software, JMP data analysis software, or Origin data processing software.

[0020] Further specifying, the selection criteria for the m environmental condition influencing factors that have a significant impact on the laser deflectometer measurement results in step 4) are: after processing using the decision tree algorithm, environmental condition influencing factors with a contribution rate greater than 0.1 are selected.

[0021] Further specifying, m ≤ 3.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] This invention presents a method for correcting laser deflectometer measurement results based on a finite element model. It utilizes the finite element method to construct a viscoelastic pavement model, then employs a decision tree algorithm to determine environmental factors that significantly influence the laser deflectometer measurement results. Finally, based on these environmental factors and data fitting methods, a correction model for the laser deflectometer measurement results is established. This invention quantifies the impact of various environmental factors, including vehicle speed, road surface temperature, surface layer thickness, and base layer thickness, on the laser deflectometer measurement results. The established correction model improves the accuracy of the laser deflectometer measurement results, ensuring that the measurement results do not affect the accuracy of subsequent modulus back-calculation. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the process of the laser deflectometer measurement result correction method based on the finite element model of the present invention.

[0025] Figure 2 Loading characteristic diagram for simulating the deflection of a viscoelastic pavement model using a falling weight deflectometer.

[0026] Figure 3 A comparison chart of the laser deflectometer measurement results before and after correction with the standard deflection parameter measurements from a falling weight deflectometer;

[0027] Figure 4 This is a comparison chart of the absolute errors of the laser deflectometer measurement results before and after correction. Detailed Implementation

[0028] The technical solution of the present invention will be further explained and described below with reference to the accompanying drawings and embodiments, but the present invention is not limited to the embodiments described below.

[0029] Example

[0030] See Figure 1 This embodiment presents a method for correcting laser deflectometer measurement results based on a finite element model, which includes the following steps:

[0031] 1) Constructing a viscoelastic pavement model; The viscoelastic pavement model in this embodiment is based on a finite element model; specifically, the viscoelastic pavement model is constructed based on dynamic simulation test data of the surface layer material, the finite element model structural parameters of the surface layer material (see Table 1), and the surface layer material parameters (see Tables 2, 3, and 4); The initial model uses SMA-13 ​​as the surface layer material, asphalt layer thickness of 16cm, base course thickness of 38cm, subbase course thickness of 20cm, and foundation thickness of 5m; The finite element model structural parameters of the surface layer material, the shear modulus parameters of the surface layer material, the WLF equation related parameters of the surface layer material, and the Rayleigh damping related parameters of the surface layer material are respectively shown in Tables 1-4 below:

[0032] Table 1: Structural parameters of the finite element model of the surface layer material

[0033] Material Layer Young's modulus (MPa, 20℃) Poisson's ratio <![CDATA[Density (kg / m 3 )]]> SMA-13 surface layer 1750 0.35 2400 Two-layer lime sand grassroots 10000 0.25 2100 lime soil Subbase 2000 0.35 1900 subgrade foundation 250 0.40 1900

[0034] Table 2: Shear modulus parameters of surface layer materials

[0035]

[0036]

[0037] In the table, τ m G refers to the relaxation time of each branch in the generalized Maxwell model. m The shear modulus refers to the shear modulus of each branch in the generalized Maxwell model.

[0038] Table 3: Relevant parameters of the WLF equation for surface layer materials

[0039] type <![CDATA[T ref (℃)]]> <![CDATA[C1]]> <![CDATA[C2]]> SMA-13 21.1 10.9 116.3

[0040] In the table, SMA-13 ​​refers to the surface layer material; T ref C1 and C2 refer to the reference temperature used in the WLF equation, and the regression coefficients in the WLF equation.

[0041] Table 4: Rayleigh damping parameters of surface material

[0042] Surface type Characteristic frequency 1 Characteristic frequency 2 α β SMA-13 16.977Hz 17.759Hz 0.867959877 0.002878858

[0043] In the table, SMA-13 ​​refers to the surface layer material; α and β refer to the scaling factors in the Rayleigh damping model.

[0044] 2) Referring to Table 5, under various environmental factors, a laser deflectometer was used to simulate the deflection of the viscoelastic pavement model, and the measured value Y of the deflection parameter of the viscoelastic pavement model was calculated.

[0045] In this embodiment, various environmental factors include road surface temperature, vehicle speed, surface layer thickness, and base layer thickness. Seven values ​​for each environmental factor are taken for scanning all combinations. The parameter settings are shown in Table 5. The deflection parameter measurement value Y of the viscoelastic pavement model is calculated by the laser deflectometer, with the unit being 0.01 mm. Finally, 2401 sets of deflection parameter measurement values ​​Y are obtained for screening.

[0046] Table 5: Parameter values ​​affected by various environmental factors

[0047] Road surface temperature / °C 20 25 30 35 40 45 50 Vehicle speed / kph 40 50 60 70 80 90 100 Surface layer thickness / cm 12 14 16 18 20 22 24 Base layer thickness / cm 18 22 26 30 34 38 42

[0048] 3) Using a falling weight deflectometer as the standard measuring instrument, the reference temperature of the falling weight deflectometer was set to 21.1℃ and the reference speed was set to 0km / h. A simulation test was conducted on the deflection of a viscoelastic pavement model using the falling weight deflectometer, and the standard deflection parameter Y0 of the viscoelastic pavement model was calculated. The deflection correction parameter ρ under various environmental factors was calculated using the deflection parameter Y and the standard deflection parameter Y0.

[0049] In this embodiment, the formula for calculating the deflection correction parameter ρ under various environmental factors using the measured deflection parameter Y and the standard deflection parameter Y0 is as follows:

[0050]

[0051] The loading area of ​​the falling weight deflectometer was set as a uniformly distributed single circle with a radius of 15 cm. To represent the characteristics of impact loading, the load of the falling weight deflectometer was set as a half-sine load P = 0.567sin(πt / 0.03), where the period of the half-sine load T = 0.03s. The standard deflection parameter measurement value Y0 = -5.396 / 10μm was obtained at 0.015s. This value was compared with the measurement values ​​obtained in step 2) under various environmental factors to obtain the correction parameters. (See also...) Figure 2 To simulate the load change process of a single FWD loading, the load peak of 0.567 MPa was reached at 0.015 s.

[0052] 4) Based on the measured value Y of the deflection parameter, the decision tree algorithm is used to screen out the m environmental condition factors that have a greater impact on the measurement results of the laser deflectometer, such as vehicle speed, road surface temperature, surface layer thickness, base layer thickness, etc.

[0053] Specifically, this step is as follows: Based on the 2401 sets of deflection parameter measurement values ​​Y obtained in step 3), the decision tree algorithm in data mining is used to screen out the environmental condition influencing factors that have a significant impact on the laser deflectometer measurement results from the 2401 sets of deflection parameter measurement values ​​Y. Among them, the contribution rates of road surface temperature, vehicle speed, surface layer thickness, and base layer thickness to the laser deflectometer measurement results are 0.377, 0.116, 0.493, and 0.013, respectively. Environmental condition influencing factors with a contribution rate greater than 0.1 are screened out, and the corresponding items of road surface temperature, vehicle speed, and surface layer thickness are retained, that is, m=3 in this embodiment. The contribution rates of X1 are 0.116, X2 is 0.377, and X3 is 0.493.

[0054] 5) Using the deflection correction parameter ρ calculated in step 3) as the dependent variable and the environmental condition influencing factors selected in step 4) as the independent variables, calculate the fitting parameters A, a, b, c, and d using numerical fitting methods. Since the fitting parameters A, a, b, c, and d are dimensionless, establish a correction model for the laser deflectometer measurement results:

[0055]

[0056] In the formula, ζ is the correction coefficient; X1, X2, X3, and X4 are different environmental factors. Specifically, X1 is the vehicle speed (km / h); X2 is the road surface temperature (°C); X3 is the surface layer thickness (cm); X4 is the base layer thickness (cm); v is the reference speed (km / h); T is the reference temperature (°C); H1 is the reference surface layer thickness (cm); and H2 is the reference base layer thickness (cm). Among these, v (reference speed), T (reference temperature), H1 (reference surface layer thickness), and H2 (reference base layer thickness) are known quantities.

[0057] Specifically, the reference speed v is 70 km / h, the reference temperature T is 21.1℃, the reference thickness H1 of the surface layer is 16 cm, and the reference thickness H2 of the base layer is 38 cm. Using the deflection correction parameter ρ as the dependent variable and the environmental condition influence factor as the independent variable, the fitting parameters A, a, b, and c were calculated using numerical fitting methods to be 0.314, -0.879, 0.321, and 0.926, respectively. The final corrected model for the laser deflectometer measurement results is as follows:

[0058]

[0059] 6) Correct the laser deflectometer measurement results using the correction model based on the laser deflectometer measurement results.

[0060] The numerical fitting in step 5) is based on the orthogonal distance regression principle and is performed using Excel spreadsheet software, JMP data analysis software, or Origin data processing software. The orthogonal distance regression principle is a calculation principle known to those skilled in the art. Preferably, the numerical fitting in this embodiment is based on the orthogonal distance regression principle and is performed using Origin data processing software.

[0061] In step 4), the selection criteria for the m environmental factors that have a significant impact on the laser deflectometer measurement results are as follows: after processing using the decision tree algorithm, environmental factors with a contribution rate greater than 0.1 are selected.

[0062] Where m ≤ 3, specifically, it can be m = 1, m = 2 or m = 3.

[0063] See Figure 3 and Figure 4 Based on 300 pairs of test data from the G2 Yihuaijiang Expressway, using the TSD (maximum deflection value) test results as the original value and the standard deflection parameter measurement value (FWD) measured by the falling weight deflectometer as the benchmark value, the laser deflectometer measurement result correction model of this embodiment is applied to correct the laser deflectometer measurement results. After correction, the average absolute error before correction of 2.5 is reduced to the average absolute error after correction of 2.01; the maximum absolute error before correction of 18.7 is reduced to the maximum absolute error after correction of 10.73. That is, the correction effect of the laser deflectometer measurement result correction model of this invention on the laser deflectometer measurement results is very significant, improving the accuracy of the laser deflectometer measurement results and ensuring that the measurement results will not affect the accuracy of subsequent modulus back calculation.

Claims

1. A method for correcting laser deflectometer measurement results based on a finite element model, characterized in that, Includes the following steps: 1) Construct a viscoelastic pavement model; 2) Under various environmental factors, a laser deflectometer was used to conduct a simulation test on the deflection of a viscoelastic pavement model, and the measured value Y of the deflection parameter of the viscoelastic pavement model was calculated. 3) Using a falling weight deflectometer as the standard measuring instrument, the reference temperature of the falling weight deflectometer was set to 21.1℃ and the reference speed was set to 0km / h. A simulation test was conducted on the deflection of a viscoelastic pavement model using the falling weight deflectometer, and the standard deflection parameter Y0 of the viscoelastic pavement model was calculated. The deflection correction parameter ρ under various environmental factors was calculated using the deflection parameter Y and the standard deflection parameter Y0. 4) Based on the measured deflection parameter Y, the decision tree algorithm is used to screen out m environmental condition influencing factors that have a significant impact on the laser deflectometer measurement results; 5) Using the deflection correction parameter ρ calculated in step 3) as the dependent variable and the environmental condition influencing factors selected in step 4) as the independent variables, calculate the fitting parameters A, a, b, c, and d using numerical fitting methods. Since the fitting parameters A, a, b, c, and d are dimensionless, establish a correction model for the laser deflectometer measurement results: In the formula, ζ is the correction coefficient; X1, X2, X3 and X4 are different environmental factors; v is the reference speed, km / h; T is the reference temperature, °C; H1 is the reference thickness of the surface layer, cm; H2 is the reference thickness of the base layer, cm; 6) Correct the laser deflectometer measurement results using the correction model based on the laser deflectometer measurement results.

2. The finite element model-based correction method of laser deflector measurements according to claim 1, wherein, The formula for calculating the deflection correction parameter ρ under various environmental factors using the measured deflection parameter Y and the standard deflection parameter Y0 is as follows:

3. The finite element model-based correction method of laser deflector measurements according to claim 1, wherein, The various environmental factors include road surface temperature, vehicle speed, surface layer thickness, and base layer thickness, where X1 is vehicle speed in km / h; X2 is road surface temperature in °C; X3 is surface layer thickness in cm; and X4 is base layer thickness in cm.

4. The finite element model-based correction method of laser deflection meter measurements of claim 1, wherein, The viscoelastic pavement model in step 1) is constructed based on the dynamic simulation test data of the surface material, the structural parameters of the finite element model of the surface material, and the parameters of the surface material.

5. The finite element model based correction method of laser deflector meter measurements of claim 1, wherein, The numerical fitting in step 5) is based on the principle of orthogonal distance regression and is performed using Excel spreadsheet software, JMP data analysis software, or Origin data processing software.

6. The method for correcting laser deflectometer measurement results based on a finite element model as described in claim 1, characterized in that, In step 4), the selection criteria for the m environmental condition influencing factors that have a significant impact on the laser deflectometer measurement results are as follows: after processing using the decision tree algorithm, environmental condition influencing factors with a contribution rate greater than 0.1 are selected.

7. The finite element model-based correction method of laser deflector measurements according to claim 6, wherein, The m≤3.

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