A method for obtaining geometric parameters of hidden targets based on multiple resonance information of ground penetrating radar echo

Abstract

The application discloses a hidden target geometric parameter acquisition method based on ground penetrating radar echo multiple resonance information and belongs to the field of radar signal processing. At present, commonly used ground penetrating radar hidden target parameter acquisition methods are mostly based on imaging algorithms or three-dimensional reconstruction methods of first scattering of ground penetrating radar echo targets, and the algorithm complexity is high. The application fully excavates the multiple resonance echo mechanism generated in the process of detecting targets by the ground penetrating radar, establishes a target geometric parameter acquisition model based on internal harmonics and external harmonics, directly obtains the geometric parameter information of the hidden target from the time domain diagram of the multiple resonance echo, provides a new method for target detection and estimation of the ground penetrating radar, and effectively solves the technical problems of great difficulty in target analysis and geometric parameter estimation in the existing ground penetrating radar echo.

Description

Technical Field

[0001] This invention relates to radar signal processing technology, specifically to a method for obtaining the geometric parameters of a hidden target based on multiple resonance information of ground-penetrating radar echoes. Background Technology

[0002] With the rapid development of my country's economy and society, the country's transportation infrastructure has entered a construction boom. Reports indicate that by the end of 2020, the total length of highways in my country had reached 5.19 million kilometers. Due to the complexity of road construction and the increasing operational time of roads and bridges, the road surface and subgrade are constantly subjected to the weight of the land, traffic loads, rainwater erosion, and other external stimuli, leading to abnormal defects such as loosening, cracks, potholes, and collapses. These become significant hidden dangers to road traffic safety. Regular inspection and maintenance are essential for existing highways and bridges that have been in long-term use. Cracks in roads are common, and early cracks are small in width, shallow in depth, and short in length, having a relatively small impact on road surface quality. However, if they are not detected and assessed in time, they will gradually deteriorate, seriously affecting road quality. Often, defects in highways and bridges are hidden and cannot be observed by the naked eye. Therefore, effectively detecting and acquiring hidden defects, and promptly identifying and assessing potential hazards, is of great significance for serving economic and social development and ensuring the safe and convenient travel of the people.

[0003] Currently, ground-penetrating radar (GPR) technology is commonly used for detecting hidden defects in highway subgrades. GPR is characterized by high efficiency, continuous operation, speed, high resolution, and non-destructive testing, and has been widely applied in non-destructive testing of infrastructure such as highways, urban roads, and tunnels. It has also become a key technology for evaluating engineering quality. GPR detection technology is primarily based on B-scan scanning. The resulting scan images are typically obtained through multi-directional and multi-angle measurements of the same scene, and the target image is reconstructed based on the surrounding dielectric environment to determine the target's relative position. However, it cannot distinguish targets of different materials based on signal amplitude or hyperbolic peak values. Furthermore, calculating the geometric dimensions of various hidden defects beneath the road surface, such as voids, cracks, and cavities, remains difficult, and the technology has not yet reached full practical application.

[0004] This invention addresses the challenge of target analysis in ground-penetrating radar (GPR) echo data by combining a method for obtaining the geometric parameters of hidden targets based on multiple resonance information of GPR echoes. The method directly calculates the target's geometric parameters from the time domain by using the internal and external resonances in the echo data. Summary of the Invention

[0005] This invention fully explores the mechanism of multiple resonance echoes generated by ground-penetrating radar (GPR) for target detection, and establishes a target geometric parameter acquisition model based on internal and external harmonics. It directly obtains the geometric parameter information of hidden targets from the time-domain plot of multiple resonance echoes, providing a new method for GPR target detection and acquisition, and effectively solving the technical problems of high difficulty in target analysis and geometric parameter acquisition in existing ground-penetrating radar echoes.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] (1) Collect ground-penetrating radar echo data, and perform preprocessing on the echo data, including adjusting the time and depth zero points and removing direct waves. The specific process is as follows:

[0008] (1-1) In a series of echo data f0(t), find the time t that maximizes the amplitude energy of f0(t). max ,Right now:

[0009] t max ={tf0(t)=max[abs(f0(t))]}

[0010] Then extract the raw echo data The data at each time point is deleted, where ΔT is the time width of the radar transmitted waveform. Thus, the echo obtained after adjusting the zero point of the time depth is...

[0011] (1-2) Remove the direct wave information from the transmitting antenna to the receiving antenna from the echo data whose time depth zero point has been adjusted;

[0012] (2) By comparing the polarity of the peaks and troughs of the ground-penetrating radar echo with the absolute values ​​of the energy values ​​or reflection coefficients, the internal and external resonances in the electromagnetic wave echo are determined. The specific process is as follows:

[0013] (2-1) Based on the polarity of the peaks and troughs of the ground-penetrating radar echo, if the polarity of the first reflected wave is the same as that of the incident wave, then the relative permittivity of the target is less than that of the background. If the polarity of the subsequent reflected wave is opposite to that of the first reflected wave, then it is an internal resonant echo; if the polarity of the subsequent reflected wave is the same as that of the first reflected wave, then it is an external resonant echo.

[0014] (2-2) Based on the polarity of the peaks and troughs of the ground-penetrating radar echo, if the polarity of the first reflected wave is opposite to that of the incident wave, then the relative permittivity of the target is greater than that of the background. Furthermore, the polarity of subsequent reflected waves is opposite to that of the first reflected wave. Considering that in highway structures, if the dielectric constant of internal defects is greater than that of the background, it is usually due to water content, which causes electromagnetic waves to lose a large amount of energy in the defects. Therefore, the peak values ​​in the echo exhibit alternating strong and weak energy. Periodic weak energy echoes are internal resonant echoes, while periodic strong energy echoes are external resonant echoes.

[0015] (3) The modeling process for obtaining the target geometric parameters of the internal resonant echo is as follows:

[0016] (3-1) Let the electromagnetic wave have a relative permittivity of ε. background In the background of a diameter of d and a relative permittivity of ε tar The time it takes for the cylindrical target to reflect back to the receiver is t0, the time it takes for the electromagnetic wave to be transmitted into the target and reflected back to the receiver is t1, the distance the electromagnetic wave travels inside the target is D, the diameter of the target is d, and the angle between the electromagnetic wave and the ground surface is θ.

[0017] (3-2) The propagation speed of electromagnetic waves in the background is Where c is the speed of light, and c = 3 × 10 8 m / s;

[0018] (3-3) The speed of electromagnetic wave propagation in the target is

[0019] (3-4) Based on the propagation mechanism of electromagnetic waves, we can obtain: in

[0020] (3-5) Substituting the parameters from b) and c) into d), we obtain the diameter calculation model for the cylindrical target body as follows:

[0021] (3-6) Let the time difference between the occurrence of the peak value of the internal resonance echo be Δt. 内 (i)=t i+1 -t i , where t i Let represent the time of the peak value of the i-th internal resonance echo. Then, the average diameter calculation model obtained from the i-th peak time is as follows:

[0022] (4) The modeling process for obtaining the target geometric parameters of the external resonant echo is as follows:

[0023] (4-1) Based on the parameter definition in (3-1), let t3 be the time it takes for the electromagnetic wave to return to the receiver after circling half a circle around the target. According to the electromagnetic wave propagation mechanism, we can obtain: Where S is the path length of the electromagnetic wave as it travels half a circle around the target body, and

[0024] (4-2) Based on (4-1), the diameter calculation model for the cylindrical target body is obtained as follows:

[0025] (4-3) Let the time difference between the appearance of the peak value of the external resonance echo be Δt. 外 (j)=t j+1 -t j , where t j Let represent the time of the j-th external resonant echo peak. Then, the average diameter calculation model obtained from the j-th peak times is as follows:

[0026] The beneficial technical effects achieved by this invention are as follows:

[0027] This invention discloses a method for obtaining the geometric parameters of hidden targets based on multiple resonance information of ground-penetrating radar (GPR) echoes, belonging to the field of radar signal processing. Currently, commonly used methods for obtaining hidden target parameters in GPR are mostly based on imaging algorithms or 3D reconstruction methods using the first scattering of GPR echoes, which have high algorithm complexity. This invention fully explores the mechanism of multiple resonance echoes generated by GPR to detect targets, establishes a target geometric parameter acquisition model based on internal and external harmonics, and directly obtains the geometric parameter information of hidden targets from the time-domain plot of multiple resonance echoes. This provides a new method for GPR target detection and acquisition, effectively solving the technical problems of high difficulty in target analysis and geometric parameter acquisition from existing ground-penetrating radar echoes. Attached Figure Description

[0028] Figure 1 A schematic diagram of a method for obtaining the geometric parameters of a hidden target based on multiple resonance information of ground-penetrating radar echoes.

[0029] Figure 2 Schematic diagram of the model for obtaining internal resonance geometric parameters.

[0030] Figure 3 A schematic diagram showing the variation of coefficient A (with a relative permittivity of 10) with the target permittivity and azimuth angle.

[0031] Figure 4 A schematic diagram showing the variation of coefficient A (with a background relative permittivity of 14) with the target permittivity and azimuth angle.

[0032] Figure 5 Schematic diagram of the model for obtaining external resonance geometric parameters.

[0033] Figure 6 A schematic diagram showing the variation of coefficient B with the relative permittivity of the background environment.

[0034] Figure 7 Schematic diagram of internal resonance time difference and external resonance time difference.

[0035] Figure 8 Calculated and average estimated values ​​of internal resonance geometric parameters.

[0036] Figure 9 Calculated and average estimated values ​​of external resonance geometric parameters. Detailed Implementation

[0037] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a method for obtaining the geometric parameters of a hidden target based on multiple resonance information of ground-penetrating radar echoes according to the present invention:

[0038] Example:

[0039] Figure 1 This paper illustrates a flowchart of a method for obtaining the geometric parameters of a hidden target based on multiple resonance information of ground-penetrating radar echoes, according to a preferred embodiment of the present invention. The invention explores the mechanism of multiple resonance echoes generated by ground-penetrating radar for target detection, establishes a target geometric parameter acquisition model based on internal and external harmonics, and directly obtains the geometric parameter information of the hidden target from the time-domain diagram of the multiple resonance echoes. This provides a new method for ground-penetrating radar target detection and acquisition, effectively solving the technical problems of high difficulty in target analysis and geometric parameter acquisition in existing ground-penetrating radar echoes.

[0040] This invention analyzes ground-penetrating radar (GPR) echo data collected from internal road structures and damaged targets. The electromagnetic waves emitted by GPR are pyramidal in shape. Let θ be the angle between the electromagnetic wave and the ground surface, and the commonly used range for the angle between the emitted electromagnetic wave and the horizontal direction is approximately... There is a cylinder with diameter d below the ground. The relative permittivity of the target disease and the underground background environment are ε and ε, respectively. tar With ε background Electromagnetic waves probe the road surface to penetrate the ground. The echoes collected at time 0 typically represent direct waves from the radar, directly received by the receiver. These waves have high energy and do not contain target information. Therefore, it is necessary to remove the direct waves and adjust the time 0 corresponding to the direct waves to correspond to the road surface. That is, in the echo data f0(t), we need to find the time t that maximizes the amplitude and energy of f0(t). max ,Right now:

[0041] t max ={tf0(t)=max[abs(f0(t))]}(1)

[0042] Then extract the raw echo data The data at each time point is deleted, where ΔT is the time width of the radar transmitted waveform. Thus, the echo obtained after adjusting the zero point of the time depth is...

[0043] After adjusting the zero point of the time depth, let t0 be the time when the electromagnetic wave first detects the target and returns to the receiver, and t1 be the time when the electromagnetic wave penetrates into the target and is reflected back to the receiver. Figure 2 As shown, according to Figure 2 Based on the geometric relationship of electromagnetic wave propagation, the time difference between t1 and t0 can be derived using the following formula:

[0044]

[0045] Where v2 is the speed at which electromagnetic waves propagate in the target body, and v1 is the propagation speed of electromagnetic waves in the background, and Where c is the speed of light, and c = 3 × 10 8 m / s; D is the distance the electromagnetic wave travels inside the target, and D = d / sinθ. The calculated diameter is obtained from equation (2):

[0046]

[0047] To further analyze the influence of the target's relative permittivity and the angle of incidence of the electromagnetic wave on the calculated diameter, let coefficient A be:

[0048]

[0049] Then equation (3) can be written as In equation (4), at a certain incident angle, the coefficient A decreases as the relative permittivity of the target increases; at a certain target permittivity, the coefficient A decreases as the incident angle increases; when the background relative permittivity is 10 and 14 respectively, the relationship between the coefficient A and the incident angle and the target relative permittivity is as follows: Figure 3 and Figure 4 As shown in the figure, under a fixed target, the change in the incident angle has little effect on the coefficient. That is, during the process of electromagnetic waves incident on the underground target from the moment they contact the target until they leave the target, the influence of the electromagnetic wave's angle θ on the diameter calculation is negligible.

[0050] Electromagnetic wave diffraction model outside the target body, such as Figure 5 As shown, let t3 be the time it takes for the electromagnetic wave to return to the receiver after circling half a circle around the target. Based on the electromagnetic wave propagation mechanism, the time difference between t3 and t0 can be derived as follows:

[0051]

[0052] Where S is the path length of the electromagnetic wave as it travels half a circle around the target body, and The calculated value of the diameter is obtained according to equation (5):

[0053]

[0054] To further analyze the influence of the target's relative permittivity and the angle of incidence of the electromagnetic wave on the calculated diameter, let coefficient B be:

[0055]

[0056] Then equation (6) can be written as As can be seen from equation (7), the coefficient B is only related to the background dielectric constant, and as the background dielectric constant increases, the coefficient B decreases, such as... Figure 6 As shown.

[0057] Let Δt be the time difference between the occurrence of the peak value of the internal resonance echo in the echo. 内 (i)=t i+1 -t i , where t i Let represent the time of the peak value of the i-th internal resonance echo. Then, the average diameter calculation model obtained from the i-th peak time is as follows: Let the time difference between the occurrence of the peak value of the external resonant echo be Δt. 外 (j)=t j+1 -t j , where t j Let represent the time of the j-th external resonant echo peak. Then, the average diameter calculation model obtained from the j-th peak times is as follows:

[0058] Taking a background relative permittivity of 9 and a hollow cylindrical defect target (diameter d = 0.15 m) relative permittivity of 1, with θ = π / 2 as an example, the obtained echo is as follows: Figure 7 As shown, the time interval between internal and external resonances is determined based on polarity and energy. Figure 7 Δt 内 With Δt 外 As shown. The calculation results are as follows. Figure 8 and 9 As shown, Figure 8 The target diameter and its average diameter value calculated using the internal resonance time difference (e.g.) Figure 8 (As shown by the dashed line), and the average diameter is 0.1494 meters. Figure 9 The target diameter and its average diameter value calculated using the external resonance time difference (e.g.) Figure 9 (As shown by the dashed line in the middle), and the average diameter is 0.1476 meters. The calculation results show that this method can effectively obtain the geometric parameter information of the target object.

Claims

1. A method for obtaining the geometric parameters of a hidden target based on multiple resonance information of ground-penetrating radar echoes, characterized in that, include: Collect ground-penetrating radar echo data and preprocess the echo data; The preprocessed echo data is used to determine internal and external resonance using the polarity energy determination method. The sequential time difference of the internal resonant echo is obtained by using a consistent polarity peak extraction method. The sequential time difference of the external resonant echo is obtained by using a consistent polarity peak extraction method with the opposite polarity to that of the internal resonant echo. Based on the scattering mechanism of ground-penetrating radar electromagnetic waves on a hidden target, a target geometric parameter acquisition model for internal resonant echoes is established. The target geometric dimensions are calculated by sequentially calculating the internal resonant time differences, and the target parameter values ​​are obtained by taking the average of the parameter calculation results for multiple time differences. At the same time, a target geometric parameter acquisition model for external resonant echoes is established. The target geometric dimensions are estimated by sequentially calculating the external resonant time differences, and the target parameter values ​​are obtained by taking the average of the parameter calculation results for multiple time differences. Establish target geometric parameter acquisition models for internal resonant echo and external resonant echo respectively; calculate the peak time difference sequence of internal resonant echo and the peak time difference sequence of external resonant echo respectively to obtain target geometric parameters in sequence, and then take the average value of the calculation results of multiple time difference parameters. The modeling steps for obtaining the target geometric parameters of the internal resonant echo are as follows: a) Assume that the electromagnetic wave has a relative permittivity of . In the background, from a diameter of d The relative permittivity is The time it takes for the cylindrical target to reflect back to the receiver is The time it takes for an electromagnetic wave to penetrate the target and be reflected back to the receiver is... The distance that electromagnetic waves travel inside the target is D The diameter of the target body is d The angle between the electromagnetic wave and the Earth's surface is ; b) The speed of electromagnetic waves in the background is ,in c It is the speed of light, and ; c) The speed of electromagnetic wave propagation in the target body is ; d) Based on the propagation mechanism of electromagnetic waves: ,in ; e) Substituting the parameters from b) and c) into d), we obtain the diameter calculation model for the cylindrical target body as follows: ; The steps for obtaining the target geometric parameters of the external resonant echo model are as follows: f) Based on the parameter definition in a), let the time it takes for the electromagnetic wave to return to the receiver after circling half a circle around the target be... Based on the electromagnetic wave propagation mechanism, we can obtain: Where S is the path length of the electromagnetic wave as it travels half a circle around the target body, and ; g) Based on f), the diameter calculation model for the cylindrical target body is as follows: .

2. The method for obtaining the geometric parameters of a hidden target based on multiple resonance information of ground-penetrating radar echoes according to claim 1, characterized in that, Also includes: The radial dimensions of road cavities, the diameter of metal pipelines, the radial dimensions of internal road cracks, the water depth in manholes, and the diameter of manhole covers were obtained.

3. The method for obtaining the geometric parameters of a hidden target based on multiple resonance information of ground-penetrating radar echoes according to claim 1, characterized in that, Preprocessing of ground-penetrating radar echo data includes adjusting the time and depth zero points and removing direct waves.

4. The method for obtaining the geometric parameters of a hidden target based on multiple resonance information of ground-penetrating radar echoes according to claim 1, characterized in that, The method for determining internal and external resonance in echo data adopts a combined method of determining the positive and negative polarity and energy of the echo.

5. The method for obtaining the geometric parameters of a hidden target based on multiple resonance information of ground-penetrating radar echoes according to claim 3, characterized in that, The method for adjusting the zero point of time depth is as follows: In a series of echo data In the middle, looking for The moment of maximum amplitude energy ,Right now: ， Then extract the raw echo data Data deletion at any given time, among which Given the time width of the radar transmitted waveform, the echo with the adjusted time depth zero point is obtained as follows: .

6. The method for obtaining the geometric parameters of a hidden target based on multiple resonance information of ground-penetrating radar echoes according to claim 4, characterized in that, Ground penetrating radar electromagnetic waves from relative permittivity Dielectric incident on relative permittivity In a medium, the reflection coefficient of the echo generated at the surface of the medium is: ， Let the polarity of the incident wave be (+, -), then when When, reflection coefficient Therefore, the polarity of the reflected wave is (-, +); when When, reflection coefficient Therefore, the polarity of the reflected wave is (+, -).

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