Disclosure of Invention
The technical problem to be solved by the invention is as follows: aiming at the technical problems in the prior art, the invention provides the method and the device for detecting the internal structure of the building based on radar signal processing, which are simple to operate, easy to realize, high in detection precision and efficiency and strong in real-time performance.
In order to solve the technical problems, the technical scheme provided by the invention is as follows:
a building internal structure detection method based on radar signal processing comprises the following steps:
s1, fixedly arranging a radar system on the outer side of a building to be detected, constructing an equivalent array by adopting a multi-transmitting multi-receiving antenna array to form an equivalent aperture, and detecting a target area through the arranged radar system to obtain a multi-channel echo signal of the target area;
s2, converting all the channel echo domain signals acquired in the step S1 into image domain data;
and S3, transforming the image domain data obtained in the step S2 into a characteristic binary image, and performing inversion to obtain the internal structure of the building.
As a further improvement of the method of the present invention, in step S2, coherent superposition processing is performed on all channel echo domain signals by using a back projection BP algorithm, and image domain data is obtained through conversion.
As a further improvement of the method of the present invention, the step of performing coherent superposition processing by using a back projection BP algorithm includes:
s21, dividing an imaging area into M multiplied by N pixel points;
s22, calculating the two-way time delay between each pixel point and all the receiving and transmitting antenna combinations;
s23, calculating the phase compensation of each pixel point according to the calculated double-pass time delay;
and S24, calculating data of each aperture domain in the equivalent aperture according to the phase compensation, accumulating the data of each aperture domain to obtain a calculation coherence stack result, and using the calculation coherence stack result as the image domain data obtained by conversion.
As a further improvement of the method of the present invention, the step S22 specifically obtains each pixel point (x) by following the following formulan,ym) With two-way time delay tau between all transceiver antenna combinationsk:
Wherein, ymAnd xnThe coordinate values of the distance-direction and the azimuth-direction pixel points are respectively represented, M is 1,2T(k),yT(k) Is the transmit antenna coordinate, (x)R(k),yR(k) Is a coordinate of the receiving antenna, c represents the speed of light, dTDistance of pixel point to transmitting antenna, dRThe distance between the pixel point and the receiving antenna;
in the step S23, each pixel point (x) is calculatedn,ym) Phase compensation phase ofkThe expression of (a) is:
phasek(xn,ym)=exp(j2πfc·(dT+dR)/c)
wherein f iscCarrier frequency, c is speed of light;
in the step S24, a coherent superposition result I is obtained by calculation according to the following formulas(x, y) and as said image domain data;
wherein z isk(x,y)=echos(t-τk(x,y))×phasek(x, y) denotes the k-th aperture domain data, echos(t-τk(x, y)) is the time delay corrected channel echo signal.
As a further improvement of the method, in step S3, two-dimensional CFAR detection is performed on the image domain data to obtain a binary image of the internal structure characteristics of the building to be detected, and the internal structure of the building is obtained through inversion; the step of performing two-dimensional CFAR detection comprises: determining a detection threshold value in advance according to the difference between the human body echo and the building echo in the image domain, taking the unit to be detected as the center, comparing the image domain data obtained in the step S2 with the detection threshold value, and obtaining a binary image of the internal structure characteristics of the building to be detected according to the comparison result.
As a further improvement of the method of the present invention, the step of determining the detection threshold value includes: respectively setting a protection window for avoiding the self-shielding effect of the object, a background reference window for estimating the unit to be detected and a corresponding detection probability PAAccording to the set protection window, reference window and detection probability PAThe detection threshold value is determined to be obtained.
As a further improvement of the method of the present invention, in step S2, all the channel echo domain signals are converted into image domain data by using a range-doppler-based imaging algorithm.
As a further improvement of the method, in step S3, the image domain data is processed by using a maximum threshold method to obtain a binary image of the internal structure characteristics of the building to be detected, and the internal structure of the building is obtained by inversion, which specifically includes: and searching the maximum value max (x, y) in the array of the image domain data, taking the designated multiple a.max (x, y) of the maximum value as a comparison threshold value, wherein 0< a <1, comparing each pixel point value with the comparison threshold value, taking the pixel point value greater than the comparison threshold value as 1, and otherwise, taking 0 to obtain the internal structural feature binary image of the building to be detected.
A building internal structure detection device based on radar signal processing comprises:
the system comprises a multi-channel echo signal acquisition module, a multi-channel echo signal acquisition module and a multi-channel echo signal acquisition module, wherein the multi-channel echo signal acquisition module is used for fixedly arranging a radar system on the outer side of a building to be detected, the radar system adopts a multi-transmitting multi-receiving antenna array to construct an equivalent array so as to form an equivalent aperture, and a target area is detected through the arranged radar system so as to acquire a multi-channel echo signal of the target area;
an image domain data conversion module, configured to convert all the channel echo domain signals obtained in step S1 into image domain data;
and an internal structure inversion module, configured to transform the image domain data obtained in step S2 into a characteristic binary image, and perform inversion to obtain an internal structure of the building.
As a further improvement of the device, the image domain data conversion module adopts an image domain data conversion module based on a BP algorithm, and is used for performing coherent superposition processing on all channel echo domain signals by adopting a back projection BP algorithm to obtain image domain data through conversion;
the internal structure inversion module is based on CFAR detection and is used for carrying out two-dimensional CFAR detection on the image domain data to obtain a binary image of the internal structure characteristics of the building to be detected, and the internal structure of the building is obtained through inversion.
Compared with the prior art, the invention has the advantages that:
1. the method and the device for detecting the internal structure of the building based on radar signal processing acquire multi-channel echo signals by adopting an equivalent aperture mode at a fixed position, convert echo domain data into image domain data, and then invert the image domain data to obtain the internal structure of the building.
2. According to the method and the device for detecting the internal structure of the building based on radar signal processing, disclosed by the invention, the multi-channel echo signal can be obtained through one-time radar detection, the real-time detection of the internal structure of the building can be realized, and further, the method and the device can be directly fused with a target detection signal processing mode in the building, so that the real-time state positions of the internal structure of the building and a target can be accurately judged.
3. The building internal structure detection method and device based on radar signal processing further utilize equivalent aperture multi-channel echo signal data at a fixed position to carry out coherent BP imaging, multi-channel echo data can be obtained by one-time detection, real-time inversion can be carried out on the building internal structure, two-dimensional CFAR detection is carried out on image domain data according to human body echoes and building structure characteristics after BP imaging, the building internal structure can be accurately inverted, and the method and device can be conveniently and directly fused with target detection in a building.
Detailed Description
The invention is further described below with reference to the drawings and specific preferred embodiments of the description, without thereby limiting the scope of protection of the invention.
As shown in fig. 1, the method for detecting the internal structure of a building based on radar signal processing in the present embodiment includes the steps of:
s1, fixedly arranging a radar system on the outer side of a building to be detected, constructing an equivalent array by the radar system through a multi-transmitting multi-receiving antenna array to form an equivalent aperture, and detecting a target area through the arranged radar system to obtain a multi-channel echo signal of the target area.
S2, converting all the channel echo domain signals acquired in the step S1 into image domain data;
and S3, transforming the image domain data obtained in the step S2 into a characteristic binary image, and performing inversion to obtain the internal structure of the building.
The radar system is specifically ultra-wideband through-wall radar equipment, and the interior of a building to be detected is detected by using a fixedly arranged through-wall radar, and a radar echo signal is returned; because the equivalent aperture is formed by adopting the array antenna design and structure on the premise of determining the working frequency band, the array element density can be increased to avoid grating lobes, and the imaging resolution can be improved, the embodiment utilizes the characteristics, the radar adopts the multi-transmitting multi-receiving antenna array structure to form the equivalent aperture, the multi-channel echo signal is obtained by adopting the equivalent aperture mode of a fixed position, the echo domain data is converted into image domain data, the image domain data is converted into a characteristic binary image, and then the internal structure of the building is obtained by inversion, thereby realizing the internal structure detection of the building by utilizing the equivalent aperture mode based on the fixed radar, compared with the traditional method of adopting a mobile radar to realize the detection by utilizing a synthetic aperture mode, a radar device does not need to be moved, the internal structure detection of the building can be realized by adopting one-time radar detection, and the operation complexity can be greatly reduced, the method improves the detection efficiency, improves the detection real-time property, and is particularly suitable for application occasions with higher real-time requirement.
The method can acquire multi-channel echo signals through one-time radar detection, can realize real-time detection of the internal structure of the building, can be executed independently and parallelly with the detection process of the targets in the building, and cannot influence the detection of the targets in the building, so that the detection of the internal structure of the building can be directly fused with the processing mode of the target detection signals in the building, and is favorable for accurately judging the real-time state positions of the internal structure and the targets of the building.
In the specific application example, when the multi-channel echo signal is extracted in step S1, the ultra-wideband radar apparatus is first fixed to the wall by using a tripod or other device, the ultra-wideband radar device adopts a multi-transmitting multi-receiving antenna array to construct an equivalent array, thereby forming an equivalent aperture, all channels sequentially transmit and receive electromagnetic wave signals, the multi-channel echo signal of the target area is obtained by directly carrying out one-time detection on the target area, the actual detection scene in the specific application embodiment is shown in figure 2, wherein the room is about 27.3m long and more than 8m wide, the radar is arranged to be close to the wall with a certain height from the ground, the center of the room is 4.4m away from the left window, 3 bearing columns of 0.5m by 0.5m are arranged in the room at positions of 7m, 14m and 21m, the left windows are 4m, 11m and 15m, 3 windows are arranged on the rear side of the room, and no wall exists between 19m and 22.65 m.
In step S2 of this embodiment, coherent superposition processing is performed on all the channel echo domain signals acquired in step S1 by using a back projection BP algorithm, and image domain data is obtained through conversion. The backward projection BP algorithm is adopted to convert the echo domain data into the image domain data, the operation is simple, the real-time performance is strong, and the detection real-time performance can be further improved.
In this embodiment, the step of performing coherent superposition processing by using a back projection BP algorithm includes:
s21, dividing an imaging area into M multiplied by N pixel points, wherein y ism(M-1, 2, …, M) and xn(m ═ 1,2, …, N) represents coordinate values of pixel points in the distance direction and the azimuth direction, respectively;
s22, calculating each pixel point (x)n,ym) A two-way time delay with all the transmitting and receiving antenna combinations;
s23, calculating the phase compensation of each pixel point according to the calculated double-pass time delay;
and S24, calculating data of each aperture domain in the equivalent aperture according to phase compensation, accumulating the data of each aperture domain to obtain a calculation coherence stack result, and using the calculation coherence stack result as the image domain data obtained by conversion.
Through the steps, the multi-channel echo data acquired by the equivalent aperture can be converted into image domain data, through coherent superposition processing, incoherent clutter, noise and side lobes among channels can be suppressed, and the suppression effect is good.
In step S22, each pixel point (x) is calculated according to the following formulas (1), (2) and (3)n,ym) Two-way time delay with all transmit-receive antenna combinations:
wherein, ym(M ═ 1,2,. multidot., M) and xnN is a coordinate value representing a pixel point in a distance direction and an orientation direction, k is 1,2,.., NUM is the channel label, NUM is the equivalent aperture number, (x)T(k),yT(k) Is the transmit antenna coordinate, (x)R(k),yR(k) Is a coordinate of the receiving antenna, c represents the speed of light, dTDistance of pixel point to transmitting antenna, dRThe distance between the pixel point and the receiving antenna;
in step S23, each pixel point (x) is calculatedn,ym) Phase compensation phase ofkThe expression of (a) is:
phasek(xn,ym)=exp(j2πfc·(dT+dR)/c) (4)
wherein f iscCarrier frequency, c is speed of light;
in step S24, a coherent addition result I is obtained by calculation according to the following formula (5)s(x, y) and as image domain data;
wherein z isk(x,y)=echos(t-τk(x,y))×phasek(x, y) denotes the k-th aperture domain data, echos(t-τk(x, y)) is the time delay corrected channel echo signal.
It can be understood that, the above-mentioned conversion of the echo domain signals of each channel into the image domain data may also adopt other methods according to actual requirements to reduce implementation complexity, etc.
In this embodiment, in step S3, performing two-dimensional CFAR detection on the image domain data to obtain a two-value graph of internal structure characteristics of the building to be detected, and performing inversion to obtain the internal structure of the building; the step of performing two-dimensional CFAR detection comprises: and determining a detection threshold value in advance according to the difference between the human body echo and the building echo in the image domain, taking the unit to be detected as a center, comparing the image domain data obtained in the step S2 with the detection threshold value, and obtaining a two-value image of the internal structure characteristic of the building to be detected according to the comparison result, wherein if the pixel value of the image domain data is greater than the detection threshold value, the two-value image is 1, otherwise, the two-value image is 0, and the two-value image is obtained. The difference between the human body echo and the building echo in the image domain comprises the difference between the distance width and the area, namely, the two-dimensional CFAR detection is carried out by utilizing the different characteristics of the distance width and the area of the human body echo and the building echo in the image domain.
The image domain data are converted into the characteristic binary image through the two-dimensional CFAR detection, the target can be accurately detected by utilizing the difference between the human body echo and the building echo in the image domain, so that the internal structure characteristics of the building are accurately inverted, and the threshold can be subjected to adaptive change according to the echo intensity by only selecting the size and the width of an appropriate window in the CFAR detection, so that the optimal detection in each local area is ensured, and the target detection probability can be improved.
In this embodiment, the step of determining the detection threshold includes: respectively setting a protection window for avoiding the self-shielding effect of the object, a background reference window for estimating the unit to be detected and a corresponding detection probability PAAccording to the set protection window, reference window and detection probability PAThe threshold value is determined according to the statistical value, and the specific expression is as follows:
in which alpha is a threshold factor, PAFor detecting the probability, N is the total number of the protection window and the reference window participating in the average, and T is the finally obtained threshold value.
After the threshold value is determined by the method, the image domain data obtained in the step S2 are respectively compared with the threshold value to be converted into a characteristic binary image, so that the target self-shielding effect can be fully considered, and the detection accuracy can be further improved.
It can be understood that, the obtaining of the binary image of the internal structure feature of the building to be detected from the image domain data may also adopt other methods according to actual requirements, for example, a maximum threshold method is used, that is, the image domain data obtained in step S2 is processed by using the maximum threshold method to obtain the binary image of the internal structure feature of the building to be detected, and the internal structure of the building is obtained by inversion, and the specific steps include: and searching the maximum value max (x, y) in the array of the image domain data, taking the designated multiple a.max (x, y) of the maximum value as a comparison threshold value, wherein 0< a <1, comparing each pixel point value with the comparison threshold value, taking the pixel point value greater than the comparison threshold value as 1, and otherwise, taking 0 to obtain the internal structural feature binary image of the building to be detected.
As shown in fig. 3, in the embodiment, when the detection of the structure in the building is realized based on the radar signal processing, specifically, after the position of the ultra-wideband radar is fixed, a target area is directly detected once, so as to obtain a multi-channel echo signal of the target area; then, carrying out coherent superposition processing on all the acquired channel echo domain signals by adopting a back projection BP algorithm to obtain image domain data; and then, carrying out two-dimensional CFAR detection on the obtained image domain data according to the structural characteristics of the building, and further performing inversion on the internal structure of the building. The method utilizes the equivalent aperture multi-channel echo signal data of the fixed position to carry out coherent BP imaging, can obtain the multi-channel echo data by one-time detection, thereby carrying out real-time inversion on the internal structure of the building, carrying out two-dimensional CFAR detection on image domain data according to the human body echo and the structural characteristics of the building after BP imaging, being capable of accurately inverting the internal structure of the building, having strong real-time performance, simple actual operation and high efficiency, and being capable of being directly fused with target detection in the building.
In order to verify the effectiveness of the invention, the actual measurement data shown in fig. 2 are processed by simulation processing and the method of the invention, fig. 4 is the result of the simulation processing of the actual measurement data shown in fig. 2, fig. 5 is the result of the detection of the internal structure of the building by the method of the invention, and as can be seen from fig. 4 and 5, the internal structure of the building detected by the method of the invention is basically matched with the actual detection scene, the protruding wall parts of the back wall, the column and the left window edge can be detected, and the internal structure of the building can be obtained by accurate inversion; the detection result obtained by further fusing the movement of the single target in the building with the method of the invention is shown in fig. 6, that is, the movement result of the single target in the building is fused with the detection structure of the internal structure of the building, wherein the curve represents the target state track, and the oblique line frame filling area represents the detection result of the structure of the building.
This embodiment is based on device of radar detection inversion building inner structure includes:
the system comprises a multi-channel echo signal acquisition module, a multi-channel echo signal acquisition module and a multi-channel echo signal acquisition module, wherein the multi-channel echo signal acquisition module is used for fixedly arranging a radar system on the outer side of a building to be detected, the radar system adopts a multi-transmitting multi-receiving antenna array to construct an equivalent array so as to form an equivalent aperture, and a target area is detected through the arranged radar system so as to acquire a multi-channel echo signal of the target area;
the image domain data conversion module is used for converting all the channel echo domain signals acquired by the multi-channel echo signal acquisition module into image domain data;
and the internal structure inversion module is used for transforming the image domain data obtained by the image domain data conversion module into a characteristic binary image and performing inversion to obtain the internal structure of the building.
In this embodiment, the image domain data conversion module adopts an image domain data conversion module based on a BP algorithm, and is configured to perform coherent superposition processing on all channel echo domain signals by using a back projection BP algorithm, so as to obtain image domain data through conversion;
the internal structure inversion module is based on CFAR detection and is used for carrying out two-dimensional CFAR detection on the image domain data to obtain a two-value image of the internal structure characteristics of the building to be detected, and the internal structure of the building is obtained through inversion.
The above-mentioned devices of this embodiment correspond to the above-mentioned building internal structure detection method based on radar signal processing one by one, and are not described herein again one by one.
The foregoing is considered as illustrative of the preferred embodiments of the invention and is not to be construed as limiting the invention in any way. Although the present invention has been described with reference to the preferred embodiments, it is not intended to be limited thereto. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical spirit of the present invention should fall within the protection scope of the technical scheme of the present invention, unless the technical spirit of the present invention departs from the content of the technical scheme of the present invention.