A method for collecting radar data of a bonding surface of a building thermal insulation layer

Abstract

The application discloses a kind of building thermal insulation layer bonding surface radar data acquisition methods, belong to radar data acquisition technical field, for building thermal insulation layer bonding surface data acquisition, including based on the principle of penetration imaging radar acquisition building thermal insulation layer bonding surface data, radar echo data is handled using range migration imaging and robust principal component analysis method, using edge detection method is connected and region filling to image edge, generate building thermal insulation layer bonding surface binary image, based on the method of the application builds building thermal insulation layer bonding surface radar data acquisition experimental platform.The application is collected to building thermal insulation layer bonding surface by radar data, and radar echo and image are optimized, provide scientific basis for evaluating the structural stability and potential risk of bonding layer, improve radar data acquisition precision and image definition;Building thermal insulation layer bonding surface radar data acquisition experimental platform is designed, realizes the method of collecting building thermal insulation layer bonding surface data in laboratory environment.

Description

TECHNICAL FIELD

[0001] The application discloses a radar data collection method for a bonding surface of a building thermal insulation layer and belongs to the technical field of radar data collection. BACKGROUND

[0002] In actual engineering, in order to balance the bonding strength, material cost and construction efficiency, the thermal insulation board is usually constructed by using a point frame method or a strip sticking method, and the bonding mortar between the thermal insulation board and the base wall is not completely paved, but forms a local bonding area with a certain distribution rule. The actual bonding area size is a key factor affecting the system stability and thermal insulation performance, and insufficient area is easy to cause local hollowing or even falling off. Since the bonding state is hidden, the traditional destructive bonding surface data collection method has high cost and limited applicability, and therefore an efficient and non-destructive bonding surface data collection technology capable of quantitatively evaluating the actual bonding area is of great significance.

[0003] Traditional bonding surface data collection methods, such as hammering and pulling, are simple to operate, but have the limitations of strong subjectivity and insufficient precision. Methods such as ultrasonic waves and infrared thermal imaging are gradually applied in engineering, but have problems such as low efficiency, results depending on experience, difficulty in realizing quantitative evaluation, and insufficient applicability in complex environments. In comparison, radar has the advantages of fast speed, anti-interference and certain penetration ability, and has gradually been applied to the bonding state identification and defect detection of external wall thermal insulation layers. Existing research attempts to estimate the bonding area by using radar, but the original radar data is severely scattered, cannot reflect the real bonding area inside the thermal insulation layer, and the precision is limited.

[0004] The bonding area not only determines the current bonding state, but also is closely related to the long-term stability of the system: the larger the area, the more stable the system; and insufficient area has potential risk of falling off. Existing research mainly focuses on the instant identification of the bonding state, and can judge whether there is debonding at present, but cannot evaluate the future structural stability or potential risk. Visualizing the bonding area of the bonding mortar inside the thermal insulation layer can not only reflect the current bonding state, but also serve as an important index for predicting the long-term reliability and potential risk of the external wall thermal insulation layer, and provide a scientific basis for maintenance and reinforcement. SUMMARY

[0005] The application aims to provide a radar data collection method for a bonding surface of a building thermal insulation layer, so as to solve the problems in the prior art that the original radar data is severely scattered, cannot reflect the real bonding area inside the thermal insulation layer, cannot evaluate the future structural stability or potential risk, and how to collect the bonding surface data of the building thermal insulation layer in a laboratory environment.

[0006] A radar data collection method for a bonding surface of a building thermal insulation layer comprises the following steps:

[0007] Data on the bonding surface of building insulation layers was acquired based on the principle of penetrating imaging radar. The target burial depth was determined by inverting the velocity of electromagnetic waves and two-way travel time. The amplitude of the echo signal was analyzed by the reflection coefficient between different media to distinguish different media types. Range migration imaging and robust principal component analysis were used to process the radar echo data. Edge detection methods were used to connect and fill the image edges to generate a binary image of the bonding surface of building insulation layers. An experimental platform for radar data acquisition of the bonding surface of building insulation layers was built.

[0008] Calculate the electromagnetic wave propagation speed based on the relative permittivity of the building insulation layer medium:

[0009] ;

[0010] In the formula, For electromagnetic wave speed, It is the speed at which electromagnetic waves propagate in a vacuum. It is the relative permittivity of the building insulation layer medium;

[0011] The distance between the target and the radar is determined based on the two-way travel time of electromagnetic waves.

[0012] ;

[0013] In the formula, The distance between the target and the antenna. This is the two-way propagation time of the electromagnetic wave in the medium;

[0014] The Fresnel reflection coefficient is used to describe the reflection and transmission characteristics of electromagnetic waves propagating at the interface between two media. When the electromagnetic wave is incident perpendicularly, the medium... and medium The reflectivity of the interface for:

[0015] ;

[0016] In the formula, as medium The relative permittivity, as medium Relative permittivity.

[0017] Establish a radar data acquisition model for the bonding surface of building insulation layer, assuming the frequency used by the step-frequency radar is... The target is illuminated by continuous waves, and the target is located at The radar antenna is located at [location]. At, and in A rectangular aperture is synthesized on the plane, and the measurement points form a rectangular grid with a horizontal spacing of [missing information]. Spacing in the vertical direction At each antenna location, the synthesized frequency bandwidth is B, and the backscattered data is... Frequency variables and two-way frequency wavenumbers Directly related ,based on Will Rewritten as Assume the target reflectivity is , measured for:

[0018] ;

[0019] ;

[0020] In the formula, The distance from the radar antenna to the point scatterer is one-way. The imaginary unit;

[0021] right Perform a two-dimensional Fourier transform to convert to the wavenumber domain. :

[0022] ;

[0023] In the formula, For the space wavenumber spectrum, for The wavenumber variable of direction, for The wavenumber variable of direction;

[0024] Substituting the point scatterer echo model By using the principle of stationary phase, the following derivation is obtained: Approximate solution:

[0025] .

[0026] Determine reference distance And construct a phase compensation function. :

[0027] ;

[0028] The vertical distance from the synthetic aperture plane of the radar antenna to the plane where the target is located; and Multiplying the signals and ignoring the amplitude effect yields the wavenumber domain signal compensated by the phase compensation function. :

[0029] ;

[0030] Using Stolt interpolation Mapped to :

[0031] ;

[0032] In the formula, for The wavenumber variable of direction;

[0033] Coordinate transformation is achieved through Stolt interpolation to obtain the spectral response of the point scatterer. :

[0034] ;

[0035] right Perform a three-dimensional inverse Fourier transform to reconstruct the spatial position and reflectivity of the point scatterer, and obtain the radar image. :

[0036] ;

[0037] In the formula, This is a three-dimensional inverse Fourier transform.

[0038] Introducing robust principal component analysis method for Slice matrix of all sampling points on any azimuth axis Clutter suppression is achieved based on low-rank sparse decomposition theory. break down:

[0039] ;

[0040] In the formula, For background clutter, The scattered signal of the mortar target. This includes system thermal noise and random disturbances;

[0041] Solving the convexity problem yields radar images that highlight the target and suppress clutter:

[0042] ;

[0043] ;

[0044] In the formula, for nuclear norm number, for of Norm, The norm is the sum of the absolute values ​​of the elements in a vector. For the Frobenius norm, It is a constant related to noise energy. This is the regularization parameter.

[0045] Edge detection is performed on the radar image, and the detected edges are connected and regions are filled to generate a binary image.

[0046] This is for a radar data acquisition experimental platform for building insulation layers. The building insulation layer radar data acquisition experimental platform includes an external wall insulation structure model, a penetration imaging radar acquisition platform, and a three-dimensional electric scanning and control system. The external wall insulation structure model is placed horizontally at the bottom inside the three-dimensional electric scanning and control system.

[0047] The penetrating imaging radar acquisition platform includes a vector network analyzer, a horn antenna, radio frequency cables, and a computer. The horn antenna is connected to the vector network analyzer via the radio frequency cables, and the vector network analyzer is connected to the computer via TCP / IP communication. The horn antenna is a ridged horn antenna with an operating frequency band covering 2GHz to 18GHz.

[0048] The three-dimensional electric scanning and control system includes a three-axis gantry and a stepper motor controller. The stepper motor controller is located at one end of the X-axis, Y-axis and Z-axis tracks of the three-axis gantry. The horn antenna is fixed at the bottom of the Z-axis track of the three-dimensional electric scanning and control system, with the horn opening pointing vertically downward. The three-dimensional electric scanning and control system completes two-dimensional planar scanning using an S-shaped trajectory at a fixed Z-axis height.

[0049] The exterior wall insulation structure model includes wave-absorbing material, a base concrete substrate, a polymer bonding mortar layer, and a graphite polystyrene insulation board. The wave-absorbing material is placed horizontally near the starting point of the X-axis track. The base concrete substrate is bonded to the graphite polystyrene insulation board via the polymer bonding mortar layer and is placed near the ending point of the X-axis track. The concrete substrate consists of six pieces with dimensions of [missing information]. The precast slabs are spliced ​​together. The substrate has a layer of adhesive mortar coated on its surface, and the outermost layer has a size of [missing information]. Graphite polystyrene insulation board.

[0050] Compared with the prior art, the present invention has the following advantages: The present invention achieves focusing on a specific depth plane through range offset imaging processing and robust principal component analysis, highlighting the target and suppressing clutter; by generating a visualized binary map, it provides a scientific basis for further evaluation of the structural stability and potential risks of the bonding layer; and by designing a radar data acquisition experimental platform for building insulation layer based on the principle of penetrating imaging radar, it realizes a method for acquiring bonding surface data of building insulation layer in a laboratory environment. Attached Figure Description

[0051] Figure 1 This is a schematic diagram of the detection principle of penetrating imaging radar;

[0052] Figure 2 This is a schematic diagram of a radar data acquisition model for the bonding surface of building insulation layers;

[0053] Figure 3 It is a simplified model of an external wall insulation structure;

[0054] Figure 4 This is a schematic diagram of a penetrating imaging radar architecture;

[0055] Figure 5 This is a structural diagram of a three-dimensional electric scanning control system;

[0056] Figure 6 This is a schematic diagram of the limit switch and ground pin;

[0057] Figure 7 This is a schematic diagram of the L-plate;

[0058] Figure 8 This is a schematic diagram of a stepper motor;

[0059] Figure 9 This is a schematic diagram of a T-plate;

[0060] Figure 10 This is a schematic diagram of a coupling;

[0061] Figure 11 This is a schematic diagram of the radar scanning trajectory;

[0062] Figure 12 It is an irregularly shaped radar raw echo image;

[0063] Figure 13 This is the result image after irregular shape imaging and clutter suppression processing;

[0064] Figure 14 It is a binary image with an irregular shape;

[0065] Figure 15 It is a regular-shaped radar raw echo image;

[0066] Figure 16 This is the result image after regular shape imaging and clutter suppression processing;

[0067] Figure 17 It is a regular-shaped binary image;

[0068] In the diagram, 1-limit switch; 2-foot; 3-L-plate; 4-stepper motor; 5-drive shaft; 6-T-plate; 7-coupling. Detailed Implementation

[0069] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention are described clearly and completely below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0070] A method for acquiring radar data on the bonding surface of building insulation layers includes:

[0071] Data on the bonding surface of building insulation layers was acquired based on the principle of penetrating imaging radar. The target burial depth was determined by inverting the velocity of electromagnetic waves and two-way travel time. The amplitude of the echo signal was analyzed by the reflection coefficient between different media to distinguish different media types. Range migration imaging and robust principal component analysis were used to process the radar echo data. Edge detection methods were used to connect and fill the image edges to generate a binary image of the bonding surface of building insulation layers. An experimental platform for radar data acquisition of the bonding surface of building insulation layers was built.

[0072] Calculate the electromagnetic wave propagation speed based on the relative permittivity of the building insulation layer medium:

[0073] ;

[0074] In the formula, For electromagnetic wave speed, It is the speed at which electromagnetic waves propagate in a vacuum. It is the relative permittivity of the building insulation layer medium;

[0075] The distance between the target and the radar is determined based on the two-way travel time of electromagnetic waves.

[0076] ;

[0077] In the formula, The distance between the target and the antenna. This is the two-way propagation time of the electromagnetic wave in the medium;

[0078] The Fresnel reflection coefficient is used to describe the reflection and transmission characteristics of electromagnetic waves propagating at the interface between two media. When the electromagnetic wave is incident perpendicularly, the medium... and medium The reflectivity of the interface for:

[0079] ;

[0080] In the formula, as medium The relative permittivity, as medium Relative permittivity.

[0081] Establish a radar data acquisition model for the bonding surface of building insulation layer, assuming the frequency used by the step-frequency radar is... The target is illuminated by continuous waves, and the target is located at The radar antenna is located at [location]. At, and in A rectangular aperture is synthesized on the plane, and the measurement points form a rectangular grid with a horizontal spacing of [missing information]. Spacing in the vertical direction At each antenna location, the synthesized frequency bandwidth is B, and the backscattered data is... Frequency variables and two-way frequency wavenumbers Directly related ,based on Will Rewritten as Assume the target reflectivity is , measured for:

[0082] ;

[0083] ;

[0084] In the formula, The distance from the radar antenna to the point scatterer is one-way. The imaginary unit;

[0085] right Perform a two-dimensional Fourier transform to convert to the wavenumber domain. :

[0086] ;

[0087] In the formula, For the space wavenumber spectrum, for The wavenumber variable of direction, for The wavenumber variable of direction;

[0088] Substituting the point scatterer echo model By using the principle of stationary phase, the following derivation is obtained: Approximate solution:

[0089] .

[0090] Determine reference distance And construct a phase compensation function. :

[0091] ;

[0092] The vertical distance from the synthetic aperture plane of the radar antenna to the plane where the target is located; and Multiplying the signals and ignoring the amplitude effect yields the wavenumber domain signal compensated by the phase compensation function. :

[0093] ;

[0094] Using Stolt interpolation Mapped to :

[0095] ;

[0096] In the formula, for The wavenumber variable of direction;

[0097] Coordinate transformation is achieved through Stolt interpolation to obtain the spectral response of the point scatterer. :

[0098] ;

[0099] right Perform a three-dimensional inverse Fourier transform to reconstruct the spatial position and reflectivity of the point scatterer, and obtain the radar image. :

[0100] ;

[0101] In the formula, This is a three-dimensional inverse Fourier transform.

[0102] Introducing robust principal component analysis method for Slice matrix of all sampling points on any azimuth axis Clutter suppression is achieved based on low-rank sparse decomposition theory. break down:

[0103] ;

[0104] In the formula, For background clutter, The scattered signal of the mortar target. This includes system thermal noise and random disturbances;

[0105] Solving the convexity problem yields radar images that highlight the target and suppress clutter:

[0106] ;

[0107] ;

[0108] In the formula, for nuclear norm number, for of Norm, The norm is the sum of the absolute values ​​of the elements in a vector. For the Frobenius norm, It is a constant related to noise energy. This is the regularization parameter.

[0109] Edge detection is performed on the radar image, and the detected edges are connected and regions are filled to generate a binary image.

[0110] This is for a radar data acquisition experimental platform for building insulation layers. The building insulation layer radar data acquisition experimental platform includes an external wall insulation structure model, a penetration imaging radar acquisition platform, and a three-dimensional electric scanning and control system. The external wall insulation structure model is placed horizontally at the bottom inside the three-dimensional electric scanning and control system.

[0111] The penetrating imaging radar acquisition platform includes a vector network analyzer, a horn antenna, radio frequency cables, and a computer. The horn antenna is connected to the vector network analyzer via the radio frequency cables, and the vector network analyzer is connected to the computer via TCP / IP communication. The horn antenna is a ridged horn antenna with an operating frequency band covering 2GHz to 18GHz.

[0112] The three-dimensional electric scanning and control system includes a three-axis gantry and a stepper motor controller. The stepper motor controller is located at one end of the X-axis, Y-axis and Z-axis tracks of the three-axis gantry. The horn antenna is fixed at the bottom of the Z-axis track of the three-dimensional electric scanning and control system, with the horn opening pointing vertically downward. The three-dimensional electric scanning and control system completes two-dimensional planar scanning using an S-shaped trajectory at a fixed Z-axis height.

[0113] The exterior wall insulation structure model includes wave-absorbing material, a base concrete substrate, a polymer bonding mortar layer, and a graphite polystyrene insulation board. The wave-absorbing material is placed horizontally near the starting point of the X-axis track. The base concrete substrate is bonded to the graphite polystyrene insulation board via the polymer bonding mortar layer and is placed near the ending point of the X-axis track. The concrete substrate consists of six pieces with dimensions of [missing information]. The precast slabs are spliced ​​together. The substrate has a layer of adhesive mortar coated on its surface, and the outermost layer has a size of [missing information]. Graphite polystyrene insulation board.

[0114] Penetrating imaging radar can detect anomalies or defects inside non-metallic media without damaging the structure itself. For example... Figure 1As shown, the basic principle is to actively radiate electromagnetic wave signals onto the surface of the structure being measured using a radar transmitting antenna. Electromagnetic waves propagate in an approximately straight line in a homogeneous medium. When the propagation path encounters a location where the dielectric constant, conductivity, or magnetic permeability changes abruptly, the electromagnetic wave is reflected and transmitted. The receiving antenna collects these echo signals and uses signal processing methods to reconstruct the scattering characteristics of the target area, thus forming a visualized image of the structure's interior. The contrast of the anomalous area in the image reflects its difference in electromagnetic properties from the surrounding medium, thus allowing for the identification and inference of the location and nature of defects. The detection mechanism of penetrating imaging radar lies in accurately measuring the travel time of the echo signal to calculate the burial depth of the anomalous target; by analyzing the amplitude of the echo signal, the electromagnetic properties of the anomalous target, i.e., its material type, can be inferred, thereby distinguishing it from the surrounding background medium. The combination of travel time and amplitude information constitutes the theoretical basis for identifying the location and properties of targets within the medium.

[0115] The echo signal received by penetrating imaging radar at each sampling point is essentially a superposition of the reflected signals from all scatterers within the target area, like a blurry photograph where all objects overlap. This data domain cannot intuitively represent the spatial distribution characteristics of the scatterers; therefore, imaging processing is needed to map the data from the time dimension to the spatial dimension. The essence of the imaging algorithm is to solve the electromagnetic inverse scattering problem. By compensating for the phase history caused by wavefront curvature and two-way path difference, it achieves precise focusing and positioning of the scattered energy in the spatial coordinate system, thereby reconstructing a spatial distribution image of the dielectric constant. Figure 2 As shown, a radar data acquisition model for the bonding surface of building insulation layer is established, assuming the frequency used by the step-frequency radar is... The target is illuminated by continuous wave radiation; the red line represents the radar path at a stepped frequency. The target is located at... The radar antenna is located at [location]. At, and in A rectangular aperture is synthesized on the plane, and the measurement points form a rectangular grid with a horizontal spacing of [missing information]. Spacing in the vertical direction , It is the one-way distance from the radar antenna to the point scatterer; then the range offset algorithm is used for frequency domain focusing. The range offset algorithm is an efficient frequency domain focusing method. The range offset algorithm solves the range offset problem caused by wavefront curvature through frequency domain processing. Its core lies in the two-dimensional discrete Fourier transform, reference function multiplication to compensate for phase and Stolt interpolation to realize the mapping from non-uniform to uniform wavenumber domain. Finally, accurate focusing is achieved through three-dimensional Fourier transform imaging.

[0116] To address the issues of severe clutter interference and target signal defocusing in radar echo data, this invention designs an efficient data processing workflow, which corely includes two steps: range-shift imaging processing and robust principal component analysis (RPCA) clutter suppression. The acquired raw 3D radar echo data is severely defocused in terms of lateral resolution, making it impossible to directly identify target shapes; therefore, imaging processing is needed to focus the echoes. The external wall insulation system has a uniform layered structure, with all bonding mortar located on the same approximate plane. Range-shift imaging is used to achieve focusing on a specific depth plane, avoiding complex interpolation calculations and resulting in high processing efficiency.

[0117] Even after focusing, clutter interference such as antenna coupling waves and reflections from the interfaces between different wall layers still exists in the image. Therefore, robust principal component analysis (PCA) is introduced to suppress clutter in the slice matrix of all sampling points along any azimuth axis. This method is based on the low-rank sparse decomposition theory in image processing: background clutter exhibits high repeatability at different scanning positions and can be considered as a low-rank matrix. The scattered signal of the mortar target is spatially discrete and can be regarded as a sparse matrix. The remaining system thermal noise and random disturbances are considered as a noise matrix. Therefore, radar image matrix It can be decomposed into the sum of three parts:

[0118] ;

[0119] Robust principal component analysis (PCA) methods estimate the low-rank and sparse components of a signal from noisy observations by solving the following convex optimization problem:

[0120] ;

[0121] ;

[0122] Through this decomposition, background clutter is separated into... The mortar target signal was extracted to Noise and errors remain. This effectively highlights the target and suppresses clutter.

[0123] The building insulation layer radar data acquisition experimental platform follows the research approach of "model construction - data acquisition - data processing - result verification". The system mainly consists of three parts: an external wall insulation structure model, a penetration imaging radar acquisition platform, and a three-dimensional electric scanning and control system. In practical engineering applications, building external wall insulation systems typically consist of multiple layers, including a base wall, an adhesive layer, an insulation layer, and a protective layer. The base wall is usually reinforced concrete or brick, serving a load-bearing function; the adhesive layer is composed of polymer mortar, used to effectively connect the insulation board to the base layer; the insulation layer often uses molded polystyrene foam board (EPS), extruded polystyrene foam board (XPS), and graphite polystyrene foam board (GEPS) to reduce heat conduction; the outer plastering mortar and mesh protective layer mainly serve to resist cracking and provide mechanical protection. Because the protective layer is relatively thin, its impact on the echo signal in radar detection is limited, so it is omitted and appropriately simplified in the experimental modeling. To conduct controllable research on the bonding state in a laboratory environment, this invention constructs a simplified external wall insulation structure model, such as... Figure 3 As shown, the model highlights the influence of the interface between the bonding layer and the insulation layer on the propagation and reflection characteristics of electromagnetic waves. The model consists of three parts: a base concrete substrate, a polymer bonding mortar layer, and a graphite polystyrene insulation board. The concrete substrate uses six boards with dimensions of [missing information]. The precast slabs are spliced ​​as The overall base ensures the scale of the experimental area.

[0124] A layer of adhesive mortar with controllable thickness is coated on the substrate surface, which can not only reproduce the complete bonding state, but also simulate various defect conditions such as local debonding and hollowing by adjusting its distribution range and thickness; the outermost layer is a piece of material with a size of The graphite polystyrene insulation board has dielectric properties close to those of actual engineering materials, and can truly reflect the electromagnetic behavior of key reflective interfaces in the insulation system.

[0125] The core of the building insulation layer radar data acquisition experimental platform directly determines the detection depth and resolution. The building insulation layer radar data acquisition experimental platform constructed in this invention adopts a transceiver integrated stepped-frequency continuous wave system, consisting of a vector network analyzer, a ridged horn antenna covering the 2GHz to 18GHz frequency band, radio frequency cables, and a computer. The system composition is as follows: Figure 4As shown, the ridged horn antenna selected in the experiment served as a transceiver antenna, possessing characteristics such as wide bandwidth, high gain, and good directivity, capable of covering the multi-frequency scattering features caused by structures of different scales within the target area. The antenna was connected to Port 1 of the vector network analyzer via an RF coaxial cable. In a single-port measurement configuration, the complex reflection coefficient S11 was recorded. This parameter not only contains the amplitude and phase information between the incident wave and the target scattered wave but also allows for the recovery of the electromagnetic response distribution within the measured medium through subsequent signal processing. To achieve automated data acquisition, a high-speed communication connection was established between the computer and the vector network analyzer via a LAN cable. Based on the TCP / IP protocol, the control program sent standard SCPI (Programmable Instrument Standard Command) instructions to the designated Socket port of the vector network analyzer to remotely configure the instrument's operating status and control its scanning measurement. The data was then transmitted in real-time to the computer for storage, providing the raw dataset for subsequent imaging algorithm processing.

[0126] To achieve high-precision 3D data acquisition of the external wall insulation layer model, this invention establishes an automated 3D electric scanning control system, such as... Figure 5 As shown, the system consists of a stepper motor module and a three-axis track, used to precisely control the position of the radar antenna in the X, Y, and Z directions to achieve full coverage scanning of the target area. Through this platform, the antenna can move along a preset path in three-dimensional space above the entire insulation layer, providing high-quality data for subsequent three-dimensional imaging and quantitative analysis of the bonding area. The system structure adopts a gantry-type three-axis layout. A limit switch 1 is installed on the outer wall of the Y-axis, and two Y-axis tracks are symmetrically fixed to the top of the experimental platform's feet 2, forming horizontal support. Figure 6 As shown; a slider is provided on the Y-axis track, and a stepper motor 4 is provided at one end of the Y-axis, as shown. Figure 8 As shown; a drive shaft 5 is installed between two tracks at one end of a stepper motor 4. The stepper motor 4 and the Y-axis are connected to the drive shaft 5 via a coupling 7, as shown. Figure 10 As shown; the X-axis track is fixed to the Y-axis slider via plate L3, and can slide along the Y-axis direction, as... Figure 7 As shown; a slider is provided on the X-axis, and a stepper motor 4 is provided at one end of the X-axis; the Z-axis track is fixed to the X-axis slider by a T-plate 6 and can move along the X-axis direction, as shown. Figure 9As shown, a stepper motor 4 is installed at the top of the Z-axis track to achieve precise vertical positioning. The horn antenna is mounted on the Z-axis track and moves stably along the Z-axis via the stepper motor 4, coupling 7, and synchronous belt. The closed-loop control of the stepper motor can precisely adjust the slider position and movement speed to ensure the stability of the radar echo signal at each sampling point. This system can achieve arbitrary three-dimensional path scanning of the radar antenna above the target model and supports flexible settings for step size, speed, and scanning area. The spatial data obtained through high-density sampling provides the necessary spatial resolution basis for subsequent imaging processing and clutter suppression. The system design takes into account high precision, repeatability, and laboratory operability, making it possible to visualize and quantitatively evaluate the bonding area of ​​the external wall insulation layer, providing robust experimental support for bonding reliability research.

[0127] Imaging experiments were conducted on bonding mortar of different shapes and areas inside the insulation layer using the constructed experimental system. During the experiment, a ridged horn antenna was used as the radar antenna, positioned 0.1m above the surface of the insulation layer model, with the antenna beam center pointing vertically downwards. Specific radar scanning parameters are shown in Table 1.

[0128] Table 1. Radar parameters selected in the experiment

[0129] .

[0130] To simulate typical working conditions of external wall insulation layers under different bonding conditions, two sets of bonding mortars with different shapes and areas were fabricated in the laboratory using molds. One set consisted of three squares and three irregularly shaped bonding mortars, while the other set consisted of three squares and three rectangles. During data acquisition, the three-dimensional electric scanning control system operated at a fixed Z-axis height, using a serpentine trajectory to complete the two-dimensional planar scanning. The scanning path was pre-set by the stepper motor controller, as shown in the image. Figure 11 As shown.

[0131] To achieve accurate extraction of the bonding mortar contour, an edge detection method is used for image segmentation. Edge detection is performed on the clutter-suppressed radar image to identify the boundary contour of the target area. Subsequently, the detected edges are connected and regions are filled to generate a complete binary image.

[0132] To verify the overall effectiveness of the experimental system and the proposed data processing flow of this invention, the prepared bonding mortar was placed between the insulation board and the concrete substrate, and a two-dimensional planar scanning measurement was performed using penetrating imaging radar. Table 2 compares the measured values ​​with the actual values ​​in two scenarios:

[0133] Table 2. Measurement results of adhesive area ratio

[0134] ;

[0135] Analysis shows that, as Figure 12 and Figure 15 As shown, the mortar echo in the original radar image is severely defocused, resulting in a loss of geometric information. Figure 13 and Figure 16 As shown, after imaging and clutter suppression processing, the true contour of the mortar is significantly enhanced, and its spatial distribution is consistent with the actual height of the object. Figure 14 and Figure 17 The mortar outline was further enhanced to generate the binary image. Table 2 shows that the relative errors in measuring the bonding area ratio were only 2.43% and 1.82%, respectively. These experiments demonstrate the effectiveness of the radar data acquisition and processing platform for building insulation layers of this invention.

[0136] This invention effectively improves the imaging clarity and identifiability of bonding mortar layers by combining a range offset imaging algorithm with a robust principal component analysis clutter suppression method. It establishes a radar data acquisition experimental platform for building insulation layers, enabling visualization and quantitative analysis of the bonding state inside the insulation layer structure. This radar data acquisition experimental platform for building insulation layers integrates multiple disciplines such as electronic information, non-destructive testing, and civil engineering, and has strong interdisciplinary and innovative characteristics. It can also serve as an important platform for interdisciplinary experimental teaching in related majors in universities.

[0137] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for acquiring radar data on the bonding surface of a building insulation layer, characterized in that, include: Data on the bonding surface of building insulation layers was acquired based on the principle of penetrating imaging radar. The target burial depth was determined by inverting the velocity of electromagnetic waves and two-way travel time. The amplitude of the echo signal was analyzed by the reflection coefficient between different media to distinguish different media types. Range migration imaging and robust principal component analysis were used to process the radar echo data. Edge detection methods were used to connect and fill the image edges to generate a binary image of the bonding surface of the building insulation layer. An experimental platform for radar data acquisition of the bonding surface of building insulation layers was built. Calculate the electromagnetic wave propagation speed based on the relative permittivity of the building insulation layer medium: ； In the formula, For electromagnetic wave speed, It is the speed at which electromagnetic waves propagate in a vacuum. It is the relative permittivity of the building insulation layer medium; The distance between the target and the radar is determined based on the two-way travel time of electromagnetic waves. ； In the formula, The distance between the target and the antenna. This is the two-way propagation time of the electromagnetic wave in the medium; The Fresnel reflection coefficient is used to describe the reflection and transmission characteristics of electromagnetic waves propagating at the interface between two media. When the electromagnetic wave is incident perpendicularly, the medium... and medium The reflectivity of the interface for: ； In the formula, as medium The relative permittivity, as medium Relative permittivity; Establish a radar data acquisition model for the bonding surface of building insulation layer, assuming the frequency used by the step-frequency radar is... The target is illuminated by continuous waves, and the target is located at The radar antenna is located at [location]. At, and in A rectangular aperture is synthesized on the plane, and the measurement points form a rectangular grid with a horizontal spacing of [missing information]. Spacing in the vertical direction At each antenna location, the synthesized frequency bandwidth is B, and the backscattered data is... Frequency variables and two-way frequency wavenumbers Directly related ,based on Will Rewritten as Assume the target reflectivity is , measured for: ； ； In the formula, The distance from the radar antenna to the point scatterer is the one-way distance. The imaginary unit; right Perform a two-dimensional Fourier transform to convert to the wavenumber domain. : ； In the formula, For the space wavenumber spectrum, for The wavenumber variable of direction, for The wavenumber variable of direction; Substituting the point scatterer echo model By using the principle of stationary phase, the following derivation is obtained: Approximate solution: ； Determine reference distance And construct a phase compensation function. : ； The vertical distance from the synthetic aperture plane of the radar antenna to the plane where the target is located; and Multiplying the signals and ignoring the amplitude effect yields the wavenumber domain signal compensated by the phase compensation function. : ； Using Stolt interpolation Mapped to : ； In the formula, for The wavenumber variable of direction; Coordinate transformation is achieved through Stolt interpolation to obtain the spectral response of the point scatterer. : ； right Perform a three-dimensional inverse Fourier transform to reconstruct the spatial position and reflectivity of the point scatterer, and obtain the radar image. : ； In the formula, This is a three-dimensional inverse Fourier transform; Introducing robust principal component analysis method for Slice matrix of all sampling points on any azimuth axis Clutter suppression is achieved based on low-rank sparse decomposition theory. break down: ； In the formula, For background clutter, The scattered signal is from the mortar target. This includes system thermal noise and random disturbances; Solving the convexity problem yields radar images that highlight the target and suppress clutter: ； ； In the formula, for nuclear norm number, for of Norm, The norm is the sum of the absolute values ​​of the elements in a vector. For the Frobenius norm, It is a constant related to noise energy. For regularization parameters; Edge detection is performed on the radar image, and the detected edges are connected and regions are filled to generate a binary image; An experimental platform for radar data acquisition of building insulation layer is used. The experimental platform includes an external wall insulation structure model, a penetrating imaging radar acquisition platform, and a three-dimensional electric scanning and control system. The external wall insulation structure model is placed horizontally at the bottom inside the three-dimensional electric scanning and control system. The penetrating imaging radar acquisition platform includes a vector network analyzer, a horn antenna, radio frequency cables, and a computer. The horn antenna is connected to the vector network analyzer via the radio frequency cables, and the vector network analyzer is connected to the computer via TCP / IP communication. The horn antenna is a ridged horn antenna with an operating frequency band covering 2GHz to 18GHz. The three-dimensional electric scanning and control system includes a three-axis gantry and a stepper motor controller. The stepper motor controller is located at one end of the X-axis, Y-axis and Z-axis tracks of the three-axis gantry. The horn antenna is fixed at the bottom of the Z-axis track of the three-dimensional electric scanning and control system, with the horn mouth pointing vertically downward. The three-dimensional electric scanning and control system completes two-dimensional planar scanning using an S-shaped trajectory at a fixed Z-axis height. The exterior wall insulation structure model includes wave-absorbing material, a base concrete substrate, a polymer bonding mortar layer, and a graphite polystyrene insulation board. The wave-absorbing material is placed horizontally near the starting point of the X-axis track. The base concrete substrate is bonded to the graphite polystyrene insulation board via the polymer bonding mortar layer and is placed near the ending point of the X-axis track. The concrete substrate consists of six pieces with dimensions of [missing information]. The precast slabs are spliced ​​together. The substrate has a layer of adhesive mortar coated on its surface, and the outermost layer has a size of [missing information]. Graphite polystyrene insulation board.

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