Underground target positioning method and device based on circular antenna array space sampling

Abstract

The invention discloses an underground target positioning method and device based on circular antenna array space sampling, and belongs to the technical field of ground penetrating radars. The method comprises the steps that a ground penetrating radar system antenna array is placed parallel to the ground and advances at a constant speed in the scanning direction, the ground penetrating radar system antenna array is a one-transmitting multi-receiving circular antenna array, a plurality of receiving antennas are evenly distributed in a circular layout, a transmitting antenna is located at the circle center of the circular array, and a receiving antenna is located at the circle center of the circular array; and performing two-dimensional DOA estimation on the data of each sampling point to obtain an azimuth angle and a pitch angle of the target under the current sampling point, and generating three-dimensional coordinate information of the target through inter-frame joint data processing of a plurality of spatial sampling points so as to realize three-dimensional positioning of the target. According to the method, continuous space sampling and inter-frame joint data processing are utilized, high-precision three-dimensional positioning of the underground target can be achieved without the need that the ground penetrating radar system has a large bandwidth, and the antenna design difficulty of the ground penetrating radar system is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of ground penetrating radar, and in particular relates to an underground target positioning method and device based on circular antenna array spatial sampling. Background Art

[0002] Ground penetrating radar technology has been widely used in resource exploration, road detection, hydrology, glacier research and other fields due to its advantages such as non-destructive, fast speed, easy operation and low cost. Underground media are usually lossy media. The higher the frequency of the ground penetrating radar radiation signal, the greater the propagation loss in the medium. Therefore, ground penetrating radar with a lower frequency has better penetration ability. At the same time, in order to obtain better distance resolution, ground penetrating radar needs to have a larger bandwidth. In addition, ground penetrating radar is also developing in the direction of miniaturization. Among them, the acoustic wave excitation antenna technology can achieve an order of magnitude reduction in antenna size at the same frequency. By adapting to a small unmanned load platform, it can improve the safety of field environment detection.

[0003] There are currently two main methods for three-dimensional positioning of underground targets. One is to rely on traditional single-channel ground penetrating radar to obtain multiple two-dimensional images through multiple scans to synthesize three-dimensional information. The other is to use multi-channel three-dimensional ground penetrating radar to obtain three-dimensional information through a single scan. The former requires multiple scans and the process is cumbersome. The latter requires array antennas, which often require large-size array antennas, and the number of antennas is large, and the equipment is heavy. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides an underground target positioning method and device based on circular antenna array spatial sampling, which adopts circular array DOA technology with continuous spatial sampling and inter-frame joint data processing to achieve high-precision three-dimensional positioning of underground targets, get rid of the dependence of underground target detection system on antenna bandwidth, and reduce the difficulty of antenna design of ground penetrating radar system. New antennas with lower frequency and smaller size can be used, such as acoustic wave excitation antennas, so as to obtain better medium penetration effect, deeper detection range and lighter ground penetrating radar system.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] On the one hand, the present invention provides an underground target positioning method based on circular antenna array spatial sampling, the method comprising:

[0007] Step S1, the antenna array of the ground penetrating radar system is placed parallel to the ground and moves forward at a constant speed along the scanning direction, wherein the antenna array of the ground penetrating radar system is a circular antenna array with multiple receiving antennas, multiple receiving antennas are evenly distributed in a circular layout, and the transmitting antenna is located at the center of the circular array;

[0008] Step S2: During the scanning process, the ground penetrating radar system records the sampling information of multiple spatial sampling points;

[0009] Step S3, performing two-dimensional DOA estimation for each spatial sampling point according to the sampling information;

[0010] Step S4, based on the two-dimensional DOA estimation result, separating the angle change curves of different targets according to the angle information of multiple spatial sampling points;

[0011] Step S5: according to the pitch angles of multiple spatial sampling points Calculate the target's coordinates on the y-axis ;

[0012] Step S6: According to the coordinates and the azimuth of multiple spatial sampling points Calculate the x-axis coordinates of the target ;

[0013] Step S7: According to the coordinates , coordinates and the pitch angles of multiple spatial sampling points Calculate the coordinates of the target in the z-axis direction ;

[0014] Step S8, at this point, the target three-dimensional coordinates ( ) estimates.

[0015] On the other hand, the present invention provides an underground target positioning device based on circular antenna array spatial sampling, comprising:

[0016] The sampling information acquisition unit is used to place the antenna array of the ground-penetrating radar system parallel to the ground and move forward at a uniform speed along the scanning direction, wherein the antenna array of the ground-penetrating radar system is a circular antenna array with multiple receptions and multiple receiving antennas are evenly distributed in a circular layout, and the transmitting antenna is located at the center of the circular array; during the scanning process, the ground-penetrating radar system records the sampling information of multiple spatial sampling points;

[0017] A two-dimensional DOA estimation unit is used to perform two-dimensional DOA estimation on each spatial sampling point according to the sampling information; based on the two-dimensional DOA estimation result, the angle change curves of different targets are separated according to the angle information of multiple spatial sampling points;

[0018] The target three-dimensional coordinate acquisition unit is used to obtain the pitch angle of multiple spatial sampling points. Calculate the target's coordinates on the y-axis ; According to the coordinates and the azimuth of multiple spatial sampling points Calculate the x-axis coordinates of the target ; According to the coordinates , coordinates and the pitch angles of multiple spatial sampling points Calculate the coordinates of the target in the z-axis direction , complete the target three-dimensional coordinates ( ) estimates.

[0019] In a third aspect, the present invention also provides an electronic device, comprising: one or more processors; a memory for storing one or more programs; wherein, when the one or more programs are executed by the one or more processors, the one or more processors implement the aforementioned underground target positioning method based on circular antenna array spatial sampling.

[0020] In a fourth aspect, the present invention provides a computer-readable storage medium having executable instructions stored thereon, which, when executed by a processor, enables the processor to implement the aforementioned underground target positioning method based on circular antenna array spatial sampling.

[0021] The beneficial effects of the present invention are:

[0022] The underground target three-dimensional positioning method of the present invention relies on circular array two-dimensional DOA estimation combined with continuous spatial sampling processing to perform three-dimensional positioning, and does not require a large-bandwidth antenna; compared with multi-point cross positioning, continuous spatial sampling is used to utilize more spatial sampling information and has higher positioning accuracy; the design difficulty of the radar system's antenna, radio frequency channel, etc. is reduced, which facilitates the miniaturization and lightweighting of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the two-dimensional DOA of a single spatial sampling point of a circular array;

[0024] Figure 2 It is a schematic diagram of the change of target azimuth during scanning;

[0025] Figure 3 It is a schematic diagram of the change of the pitch angle of the target during the scanning process;

[0026] Figure 4 This is a flow chart of an underground target positioning method based on circular antenna array spatial sampling of the present invention;

[0027] Figure 5 It is a single point signal processing flow chart;

[0028] Figure 6 It is a curve diagram of estimated parameters obtained for a single target based on the azimuth information of multiple spatial sampling points;

[0029] Figure 7 The figure is a comparison diagram between the estimated position of the target obtained based on the method of the present invention and the actual position of the target. DETAILED DESCRIPTION

[0030] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0031] The purpose of the present invention is to provide an underground target positioning method and device based on circular antenna array spatial sampling. The method does not require the antenna to have a large bandwidth, and relies on the circular array DOA technology to provide a new technical solution for three-dimensional positioning of underground targets through one-dimensional scanning.

[0032] like Figure 1 As shown, the ground penetrating radar system of the present invention adopts a one-transmit-multiple-receive antenna array, and the receiving antennas are arranged in a circular layout. Without loss of generality, 6 receiving antennas are taken as an example, and the interval between the receiving antennas is less than 1 / 4 wavelength. The transmitting antenna is located at the center of the circular array, and the center of the circular array is taken as the origin of the rectangular coordinate system. The axis is perpendicular to the ground and upward. The axis points to the direction of the scan, and the coordinates of the underground target are , the angle between the line connecting the underground target and the center of the circular array and the z-axis is the pitch angle, recorded as , the angle between the projection of the line connecting the underground target and the center of the circular array on the xoy plane and the y-axis is the azimuth, recorded as .

[0033] Assume that the radius of the antenna array with one transmit and multiple receive is , the number of array elements is N, and the azimuth angle of each array element is set to , let the angle of the first array element be , because the array elements are evenly distributed in a circle, so Assume that The goal is target, assuming its azimuth is , the pitch angle is , its steering vector It can be expressed as:

[0034] ,

[0035] In the formula, exp represents the exponential function, j represents the imaginary unit, Indicates wavelength;

[0036] The received signal of N array elements can be expressed as:

[0037] ,

[0038] Among them, the intermediate parameters , represents the received data vector, represents the source vector, represents the noise vector, t represents the time variable;

[0039]

[0040]

[0041]

[0042] In the formula, the superscript T represents the transpose of the matrix;

[0043] By receiving data vector The covariance matrix of the received array signal can be obtained for:

[0044]

[0045] in, represents the autocorrelation coefficient of the signal, represents the noise power, represents the identity matrix, the superscript H represents the conjugate transpose of the matrix, and E[] represents the mathematical expectation.

[0046] The antenna array receives The echo signal of the target, the covariance matrix The eigenvalues ​​of The larger eigenvalues ​​are determined by the signal, and the other smaller eigenvalues ​​are determined by the noise, which is equal to , for the covariance matrix The characteristic decomposition is:

[0047]

[0048] In the above formula, and They represent the signal subspace and the noise subspace respectively. Ideally, the signal subspace With the noise subspace are mutually orthogonal, so the signal subspace The guiding vector Also with the noise subspace Orthogonal,

[0049]

[0050] Therefore, the spatial spectrum is:

[0051]

[0052] Searching for the peak of the spatial spectrum can get the pitch angle corresponding to the target and azimuth The value of .

[0053] like Figure 2 and Figure 3 As shown, a right-handed three-dimensional coordinate system is established for the detection scene of the present invention. The axis is perpendicular to the ground and upward. The axis points to the direction of scanning. Assume that the coordinates of the center of the ground penetrating radar antenna array are , assuming there is a target within the scanning detection range, its coordinates are , when the ground penetrating radar moves along the y-axis, Each sampling information of the ground penetrating radar can obtain two angle information of the target through the circular array DOA, one is the target vector The angle between the projection on the plane and the y-axis is the azimuth , one is the angle between the target vector and the z-axis, that is, the pitch angle , as the ground penetrating radar moves, the azimuth and pitch angle The size of will also change:

[0054] ,

[0055] ,

[0056] In the formula, || means taking the absolute value.

[0057] From above You can get:

[0058] ,

[0059] in, The curve is an inverse proportional function;

[0060] The curve is a quadratic function with the parameter It is the symmetry axis of the function, and its characteristics are significant, so we can first use the DOA estimation to get Value, please , for the parameters Make an estimate. After the parameters are determined, The curve has only one undetermined parameter and can be Then there is only one unknown parameter left , can be further The curve is determined. So far, the three-dimensional coordinates of the target are completely determined.

[0061] like Figure 4 As shown, based on the above-described theory, the underground target positioning method described in the present invention includes the following steps:

[0062] Step S1, the antenna array of the ground penetrating radar system is placed parallel to the ground and moves forward at a constant speed along the scanning direction;

[0063] Step S2: During the scanning process, the ground penetrating radar system records the sampling information of multiple spatial sampling points;

[0064] Step S3, performing two-dimensional DOA estimation for each spatial sampling point according to the sampling information;

[0065] Step S4, separating the angle change curves of different targets according to the angle information of multiple spatial sampling points;

[0066] Step S5: according to the pitch angles of multiple spatial sampling points Calculate the target's coordinates on the y-axis ;

[0067] Step S6: Coordinates and azimuths of multiple spatial sampling points Calculate the x-axis coordinates of the target ;

[0068] Step S7: According to the coordinates , coordinates and the pitch angles of multiple spatial sampling points Calculate the coordinates of the target in the z-axis direction ;

[0069] Step S8, at this point, the target three-dimensional coordinates ( ) estimates.

[0070] like Figure 5 As shown, the signal processing steps for each spatial sampling point in step S3 are:

[0071] Step S31, pre-processing the echo data, such as filtering, signal amplification, etc.;

[0072] Step S32, calculating the covariance matrix of the multi-channel signal;

[0073] Step S33, performing eigenvalue decomposition on the covariance matrix;

[0074] Step S34, analyzing the characteristic values ​​to determine the target quantity;

[0075] Step S35, separating the signal subspace and the noise subspace;

[0076] Step S36, calculating the two-dimensional spatial spectrum;

[0077] Step S37: Search for the peak value of the two-dimensional spatial spectrum and record the azimuth angle corresponding to the target. and pitch angle .

[0078] Example

[0079] Set up two targets, their position coordinates are and , using the positioning method of the present invention, assuming the radius of the array is Meter, number of array elements The ground penetrating radar scans along the y-axis. The array element numbered 0 is initially located in the positive direction of the y-axis. The azimuth of the first array element is , other array elements are The numbers are clockwise on the plane, and the azimuth angle relative to the center of the array element is .

[0080] When the ground penetrating radar scans along the y-axis, the position of the array center changes from Move to , scanning a total distance of ten meters. Figure 6 As shown, the coordinates The target is based on the pitch angle of multiple spatial sampling points Estimated parameters.

[0081] like Figure 7 As shown, it is a comparison between the estimated results of the two target positions and the actual positions. The estimated target position and the actual target position basically coincide with each other. It can be seen that the method of the present invention has high reliability.

[0082] On the other hand, the present invention provides an underground target positioning device based on circular antenna array spatial sampling, wherein each unit included in the device can perform each of the aforementioned steps, specifically including:

[0083] The sampling information acquisition unit is used to place the antenna array of the ground-penetrating radar system parallel to the ground and move forward at a uniform speed along the scanning direction, wherein the antenna array of the ground-penetrating radar system is a circular antenna array with multiple receptions and multiple receiving antennas are evenly distributed in a circular layout, and the transmitting antenna is located at the center of the circular array; during the scanning process, the ground-penetrating radar system records the sampling information of multiple spatial sampling points;

[0084] A two-dimensional DOA estimation unit is used to perform two-dimensional DOA estimation on each spatial sampling point according to the sampling information; based on the two-dimensional DOA estimation result, the angle change curves of different targets are separated according to the angle information of multiple spatial sampling points;

[0085] The target three-dimensional coordinate acquisition unit is used to obtain the pitch angle of multiple spatial sampling points. Calculate the target's coordinates on the y-axis ; According to the coordinates and the azimuth of multiple spatial sampling points Calculate the x-axis coordinates of the target ; According to the coordinates , coordinates and the pitch angles of multiple spatial sampling points Calculate the coordinates of the target in the z-axis direction , complete the target three-dimensional coordinates ( ) estimates.

[0086] In a third aspect, the present invention also provides an electronic device, comprising: one or more processors; a memory for storing one or more programs; wherein, when the one or more programs are executed by the one or more processors, the one or more processors implement the aforementioned underground target positioning method based on circular antenna array spatial sampling.

[0087] In a fourth aspect, the present invention provides a computer-readable storage medium having executable instructions stored thereon, which, when executed by a processor, enables the processor to implement the aforementioned underground target positioning method based on circular antenna array spatial sampling.

[0088] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for underground target positioning based on circular antenna array spatial sampling, characterized in that: The method comprises: Step S1, the antenna array of the ground penetrating radar system is placed parallel to the ground and moves forward at a constant speed along the scanning direction, wherein the antenna array of the ground penetrating radar system is a circular antenna array with multiple receiving antennas, multiple receiving antennas are evenly distributed in a circular layout, and the transmitting antenna is located at the center of the circular array; Step S2: During the scanning process, the ground penetrating radar system records the sampling information of multiple spatial sampling points; Step S3, performing two-dimensional DOA estimation for each spatial sampling point according to the sampling information; Step S4, based on the two-dimensional DOA estimation result, separating the angle change curves of different targets according to the angle information of multiple spatial sampling points; Step S5: according to the pitch angles of multiple spatial sampling points Calculate the target's coordinates on the y-axis ; Step S6: According to the coordinates and the azimuth of multiple spatial sampling points Calculate the x-axis coordinates of the target ; Step S7: According to the coordinates , coordinates and the pitch angles of multiple spatial sampling points Calculate the coordinates of the target in the z-axis direction ; Step S8, at this point, the target three-dimensional coordinates ( ) estimates.

2. The underground target positioning method based on circular antenna array spatial sampling according to claim 1 is characterized in that: The step S3 comprises: Step S31, preprocessing the sampling information; Step S32, calculating the covariance matrix of the received array signal based on the preprocessed sampling information; Step S33, performing eigenvalue decomposition on the covariance matrix; Step S34, determining the target quantity based on the decomposed eigenvalues; Step S35, separating the receiving array signal subspace and the noise subspace; Step S36, calculating the two-dimensional spatial spectrum; Step S37: Search for the peak value of the two-dimensional spatial spectrum and record the azimuth angle corresponding to the target. and pitch angle .

3. The underground target positioning method based on circular antenna array spatial sampling according to claim 2 is characterized in that: The step S32 comprises: receiving a data vector Calculate the covariance matrix of the received array signal for: in, represents the autocorrelation coefficient of the signal, represents the noise power, represents the unit matrix, the superscript H represents the matrix conjugate transpose, and E[] represents the mathematical expectation. , represents the elevation angle of the target relative to the center of the antenna array, Indicates the azimuth of the target relative to the center of the antenna array.

4. The underground target positioning method based on circular antenna array spatial sampling according to claim 2 is characterized in that: The step S33 includes: Performing eigenvalue decomposition involves, In the formula, and They represent signal subspace and noise subspace respectively, K is the number of targets, and N is the number of receiving antennas.

5. The underground target positioning method based on circular antenna array spatial sampling according to claim 2 is characterized in that: The step S36 includes calculating the formula of the two-dimensional spectrum space as follows: In the formula, represents the target’s steering vector, is the target's elevation angle relative to the center of the antenna array, is the azimuth of the target relative to the center of the antenna array, and the superscript H represents the matrix conjugate transpose. represents the noise subspace.

6. The underground target positioning method based on circular antenna array spatial sampling according to claim 1 is characterized in that: The step S5 comprises: As the GPR system moves, the target's elevation angle relative to the center of the antenna array The function of the coordinate y scanned by the ground penetrating radar system is: ， In the formula, || means taking the absolute value, , Indicates the coordinates of the target; From the above formula, we can get: ， Using the target's elevation angle relative to the center of the antenna array , for the parameters , Make an estimate.

7. The underground target positioning method based on circular antenna array spatial sampling according to claim 1 is characterized in that: The step S6 comprises: As the GPR system moves, the azimuth of the target relative to the center of the antenna array The function that changes with the coordinate y of the ground penetrating radar scanning system is: ， Based on the above parameters Perform fitted estimates.

8. An underground target positioning device based on circular antenna array spatial sampling, characterized in that: include: The sampling information acquisition unit is used to place the antenna array of the ground-penetrating radar system parallel to the ground and move forward at a uniform speed along the scanning direction, wherein the antenna array of the ground-penetrating radar system is a circular antenna array with multiple receptions and multiple receiving antennas are evenly distributed in a circular layout, and the transmitting antenna is located at the center of the circular array; during the scanning process, the ground-penetrating radar system records the sampling information of multiple spatial sampling points; A two-dimensional DOA estimation unit is used to perform two-dimensional DOA estimation on each spatial sampling point according to the sampling information; based on the two-dimensional DOA estimation result, the angle change curves of different targets are separated according to the angle information of multiple spatial sampling points; The target three-dimensional coordinate acquisition unit is used to obtain the pitch angle of multiple spatial sampling points. Calculate the target's coordinates on the y-axis ; According to the coordinates and the azimuth of multiple spatial sampling points Calculate the x-axis coordinates of the target ; According to the coordinates , coordinates and the pitch angles of multiple spatial sampling points Calculate the coordinates of the target in the z-axis direction , complete the target three-dimensional coordinates ( ) estimates.

9. An electronic device, characterized in that: include: one or more processors; A memory for storing one or more programs; Among them, when one or more programs are executed by the one or more processors, the one or more processors implement the underground target positioning method based on circular antenna array spatial sampling as described in any one of claims 1-7.

10. A computer-readable storage medium, characterized in that: Executable instructions are stored thereon, which, when executed by a processor, enable the processor to implement an underground target positioning method based on circular antenna array spatial sampling as described in any one of claims 1-7.

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