A small loop frequency domain electromagnetic array detection device and method for urban environment

Abstract

The present invention relates to the field of geophysical electromagnetic methods, and specifically to a small-loop frequency-domain electromagnetic array detection device and method for urban environments. The device includes: a transmitting system for generating a periodic sinusoidal current; a transmitting coil connected to the transmitting system for transmitting a primary field underground, with the side length of the transmitting coil being less than 2 meters; a receiving coil array composed of multiple receiving coils for receiving secondary field signals induced by underground structures; a receiving system connected to the receiving coil array for processing the received secondary field signals; and a hinge-type mobile platform for carrying the receiving coil array and the receiving system and moving along a survey line. The small-loop frequency-domain electromagnetic array detection device and method for urban environments of the present invention can quickly detect in urban areas and effectively solve the problem of low detection efficiency of traditional frequency-domain electromagnetic method instruments.

Description

Technical Field

[0001] The present invention relates to the field of geophysical electromagnetic methods, and specifically to a small-loop frequency-domain electromagnetic array detection device and method for urban environments. Background Technique

[0002] The utilization of urban above-ground space is gradually approaching saturation, and the development and utilization of underground space have become a hot topic. Urban geological safety issues have become increasingly prominent. As a classic geophysical detection method, the electromagnetic method is widely used in fields such as environmental engineering and geological disaster monitoring. During detection, an excitation current is injected into an ungrounded loop through a transmitting system. According to the principle of electromagnetic induction, the underground medium generates a response signal, which is analyzed to obtain the distribution state of the underground electrical medium. This method has advantages such as non-destructiveness, high efficiency, and low cost. Therefore, detecting urban underground space through the electromagnetic method helps to increase the degree of underground exploration and improve development safety, which is of great significance.

[0003] According to the time-varying characteristics of the electromagnetic field and its mathematical description method, electromagnetic detection methods can be divided into two types: time domain and frequency domain. The time-domain electromagnetic method relies on the transient response signal generated at the moment when the transmitting current is turned off for detection. Its frequency spectrum range is relatively wide, and the energy distribution is relatively dispersed; while the frequency-domain electromagnetic method uses a periodic current with a fixed frequency as the excitation, so the spectral energy is concentrated at specific frequency points. In urban environments, due to the complex underground structure, high-conductivity targets such as metal pipelines will cause the rapid attenuation of electromagnetic wave energy. The time-domain electromagnetic method relies on transient response signals for detection. In such environments, the attenuation of its effective signals is more significant, affecting the detection efficiency.

[0004] Currently, the traditional fixed single-coil transceiver mode used in frequency-domain electromagnetic detection has low working efficiency. Due to the limited signal coverage range, it is difficult to effectively identify the complex electrical structures underground in cities, and its anti-interference ability is weak and vulnerable to interference sources such as metal pipelines. Therefore, in view of the above current situation, there is an urgent need to develop a small-loop frequency-domain electromagnetic array detection device and method for urban environments to overcome the deficiencies in current practical applications. Summary of the Invention

[0005] The purpose of the present invention is to provide a small-loop frequency-domain electromagnetic array detection device and method for urban environments to solve the problems raised in the above background technique.

[0006] To achieve the above purpose, the present invention provides the following technical solutions:

[0007] A small-loop frequency-domain electromagnetic array detection device for urban environments, comprising:

[0008] A transmitting system for generating a periodic sine wave current;

[0009] A transmitting coil, connected to the transmitting system, for transmitting a primary field underground, and the side length of the transmitting coil is less than 2 meters;

[0010] A receiving coil array, composed of multiple receiving coils, for receiving secondary field signals induced by underground structures;

[0011] A receiving system, connected to the receiving coil array, for processing the received secondary field signals;

[0012] And a hinged mobile platform, for carrying the receiving coil array and the receiving system, and moving along the survey line.

[0013] As a further solution of the present invention: the number of receiving coils in the receiving coil array is n, labeled 1, 2,..., n, and the first receiving coil is the receiving coil closest to the transmitting coil.

[0014] As a further solution of the present invention: the hinged mobile platform can flexibly adjust the arrangement mode of the receiving coil array according to actual detection requirements.

[0015] A detection method for a small loop frequency domain electromagnetic array detection device in an urban environment according to the above, comprising the following steps:

[0016] Step S1: Arrange a transmitting coil and a receiving coil array in the target area and the reference area respectively, transmit a primary field underground through the transmitting system, and receive secondary field signals through the receiving coil array;

[0017] Step S2: Perform relevant superposition processing on the vertical magnetic field components collected by the receiving coil array, and calculate the normalized anomaly ratio Q of the background fields in the target area and the reference area;

[0018] Step S3: Introduce the reptile search algorithm in the metaheuristic algorithm, and take the maximization of the normalized anomaly ratio Q as the goal to obtain the optimal constraint parameters;

[0019] Step S4: Substitute the obtained optimal constraint parameters into the calculation of the normalized anomaly ratio Q in step S2 to obtain the optimal normalized anomaly ratio Q, repeat the operation until all measurement points are completed, and obtain the underground electrical structure of the target area.

[0020] As a further solution of the present invention: in step S1, the reference area is an area close to the target area in terms of geographical location, with similar geological structures and few interference sources.

[0021] As a further solution of the present invention: in step S1, the transmitting frequency of the transmitting coil is a fixed frequency, and the receiving frequency of the receiving coil array is the same as the transmitting frequency, but the amplitude and phase change according to the underground electrical structure.

[0022] As a further solution of the present invention: in step S2, the specific steps of the relevant superposition processing include:

[0023] Performing constrained superposition on the received coil array response H in the target area to obtain the superposition response G in the target area. The specific formula is as follows:

[0024] ;

[0025] Where, for n receiving coils, x is the receiving coil number, x ∈ [1, n], is the distance from the x-th receiving coil to the 1st receiving coil, is the position compensation coefficient, is the amplitude compensation coefficient, i is the imaginary unit, and its square is equal to -1, H x represents the vertical magnetic field component collected by the x-th receiving coil, e represents the natural number approximately equal to 2.718, represents the attenuation coefficient of the electromagnetic wave during propagation;

[0026] Performing direct superposition on the background field received coil array response in the reference area to obtain the superposition response in the reference area. The specific formula is as follows:

[0027] ;

[0028] Where, represents the vertical magnetic field component of the background field collected by the x-th receiving coil;

[0029] Calculating the initial normalized anomaly ratio Q of the background fields in the target area and the reference area. Among them, the calculation formula of the normalized anomaly ratio Q is:

[0030] .

[0031] As a further solution of the present invention: in step S3, the reptile search algorithm is used to optimize the constraint parameters, with -Q as the objective function, and the evolution factor is dynamically adjusted during the search process. The value range of the evolution factor is between 2 and -2.

[0032] As a further solution of the present invention: through continuous iterative optimization of the reptile search algorithm, -Q is minimized, thereby obtaining the maximum anomaly response.

[0033] Compared with the prior art, the beneficial effects of the present invention are:

[0034] 1. The present invention can quickly detect in urban areas, effectively solving the problem of low detection efficiency of traditional frequency domain electromagnetic method instruments;

[0035] 2. Compared with single - coil reception, the present invention effectively highlights the underground anomaly response, improves the detection resolution, and has a faster inversion and interpretation speed.

[0036] 3. The mobile platform adopted in the present invention is hinged, and the number and arrangement of the receiving coil arrays can be flexibly adjusted according to the detection target and requirements, with strong flexibility and adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic diagram of the urban - environment small - loop frequency - domain electromagnetic array detection device in the embodiment of the present invention;

[0038] Among them, 1 - transmitting system, 2 - transmitting coil, 3 - receiving coil array, 4 - receiving system, 5 - hinged mobile platform.

[0039] Figure 2 It is a schematic diagram of the transmitting waveform and three typical receiving waveforms in a typical receiving coil array in the embodiment of the present invention.

[0040] Figure 3 It is a flow chart of the detection method of the urban - environment small - loop frequency - domain electromagnetic array detection device in the embodiment of the present invention.

[0041] Figure 4 It is a flow chart of obtaining the optimal constraint parameters based on the reptile search algorithm in the embodiment of the present invention.

[0042] Figure 5 It is a schematic diagram of the numerical simulation model in the embodiment of the present invention.

[0043] Figure 6 It is a comparison diagram of the detection effects of a single receiving coil and the receiving coils of the array in the embodiment of the present invention;

[0044] Among them, (a) is the magnitude of the background field and the total field of a single receiving coil, and (b) is the magnitude of the background field and the total field of the receiving coils of the array. DETAILED IMPLEMENTATION MANNER

[0045] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0046] The following describes the specific implementation of the present invention in detail with specific embodiments.

[0047] Please refer to Figures 1-6, a frequency domain electromagnetic array detection device for small loop in urban environment provided by an embodiment of the present invention includes:

[0048] A transmitting system 1 for generating a periodic sinusoidal current;

[0049] A transmitting coil 2 connected to the transmitting system 1 for transmitting a primary field into the ground, and the side length of the transmitting coil 2 is less than 2 meters;

[0050] A receiving coil array 3 composed of multiple receiving coils for receiving secondary field signals induced by underground structures;

[0051] A receiving system 4 connected to the receiving coil array 3 for processing the received secondary field signals;

[0052] And a hinge-type mobile platform 5 for carrying the receiving coil array 3 and the receiving system 4 and moving along the survey line.

[0053] In an embodiment of the present invention, the number of receiving coils in the receiving coil array 3 is n, numbered 1, 2,..., n, and the first receiving coil is the receiving coil closest to the transmitting coil 2.

[0054] The hinge-type mobile platform 5 can flexibly adjust the arrangement mode of the receiving coil array 3 according to actual detection requirements.

[0055] In an embodiment of the present invention, a detection method for the above-mentioned frequency domain electromagnetic array detection device for small loop in urban environment includes the following steps:

[0056] Step S1: Arrange the transmitting coil 2 and the receiving coil array 3 in the target area and the reference area respectively, transmit a primary field into the ground through the transmitting system 1, and receive secondary field signals through the receiving coil array 3;

[0057] Among them, the three-dimensional frequency domain finite difference method is used to calculate the secondary response of the underground medium to the primary field, providing a theoretical reference for the received signal;

[0058] Step S2: Perform correlation superposition processing on the vertical magnetic field components collected by the receiving coil array 3, and calculate the normalized anomaly ratio Q of the background fields in the target area and the reference area;

[0059] Step S3: Introduce the reptile search algorithm in the meta-heuristic algorithm, and take the maximization of the normalized anomaly ratio Q as the goal to obtain the optimal constraint parameters;

[0060] Step S4: Substitute the obtained optimal constraint parameters into the calculation of the normalized anomaly ratio Q in step S2 to obtain the optimal normalized anomaly ratio Q, repeat the operation until all measurement points are completed, and obtain the underground electrical structure of the target area.

[0061] In one embodiment of the present invention, in step S1, the reference area is an area that is geographically close to the target area, has a similar geological structure, and has few interference sources.

[0062] In step S1, the transmission frequency of the transmission coil 2 is a fixed frequency, and the reception frequency of the reception coil array 3 is the same as the transmission frequency, but the amplitude and phase vary according to the underground electrical structure. Among them, each reception coil in the reception coil array 3 receives the underground information at its location, and the amplitude and phase of the reception signal of different reception coils relative to the transmission signal reflect the underground electrical structure (resistivity) at its location.

[0063] In one embodiment of the present invention, in step S2, the specific steps of the correlation stacking process include:

[0064] Performing constrained stacking on the reception coil array response H of the target area to obtain the stacked response G of the target area. The specific formula is as follows:

[0065] ;

[0066] Among them, for n reception coils, x is the reception coil number, x ∈ [1, n], is the distance from the x-th reception coil to the first reception coil, is the position compensation coefficient, is the amplitude compensation coefficient, i is the imaginary unit, and its square is equal to -1. H x represents the vertical magnetic field component collected by the x-th reception coil, e represents the natural number approximately equal to 2.718, represents the attenuation coefficient of the electromagnetic wave during propagation;

[0067] Performing direct stacking on the background field reception coil array response of the reference area to obtain the stacked response of the reference area. The specific formula is as follows:

[0068] ;

[0069] Among them, represents the vertical magnetic field component of the background field collected by the x-th reception coil;

[0070] Calculating the initial normalized anomaly ratio Q between the background field of the target area and the reference area. Among them, the calculation formula of the normalized anomaly ratio Q is:

[0071] .

[0072] In one embodiment of the present invention, in step S3, a reptile search algorithm is used to optimize the constraint parameters. Taking -Q as the objective function, the evolution factor is dynamically adjusted during the search process, and the value range of the evolution factor is between 2 and -2.

[0073] The reptile search algorithm continuously iterates and optimizes to minimize -Q, thereby obtaining the maximum abnormal response.

[0074] Embodiment 1: As Figure 1 shown, the small loop frequency domain electromagnetic array detection device for urban environment of the present invention includes a transmitting system 1, a transmitting coil 2, a receiving coil array 3, a receiving system 4, and a hinge type mobile platform 5.

[0075] As Figure 2 shown, it is a typical transmitting current waveform and receiving voltage waveform. The transmitting current is a periodic sine wave. The receiving voltage waveform is shown taking 3 coils as an example, having the same frequency as the transmitting current, but with different amplitude and phase changes, reflecting the electrical structure characteristics of different underground positions.

[0076] As Figure 3 shown, the detection method of the small loop frequency domain electromagnetic array detection device for urban environment of the present invention includes:

[0077] Step A: Construct a small loop frequency domain electromagnetic array detection device, and conduct detections in the target area and the reference area respectively;

[0078] Step B: Taking the reference area as the background field, calculate the normalized anomaly ratio Q at each measurement point;

[0079] Step C: At each measurement point, aiming at the maximum normalized anomaly ratio Q, obtain the optimal constraint parameters based on the meta - heuristic algorithm;

[0080] Step D: Repeat the above work until all measurement points are completed, and the underground geological electrical structure of the survey line can be obtained to end.

[0081] Embodiment 2: Step A specifically includes: defining the area to be detected as the target area, defining the area close to the survey area in terms of geographical location, having a similar geological structure and few interference sources as the reference area, taking the data obtained from the reference area as the background field, arranging the transmitting coil 2 and the transmitting system 1 on the ground, arranging the receiving coil array 3 and the receiving system 4 on the hinge type mobile platform 5, and the hinge type mobile platform 5 moves along the survey line;

[0082] The transmitting system 1 generates a periodic sinusoidal current through the transmitting coil 2 to transmit a primary field to the ground; the receiving system 4 receives the secondary field signal induced by the underground structure through the receiving coil array 3 during the movement of the hinged mobile platform 5; the receiving coil closest to the transmitting coil during detection is defined as the 1st receiving coil, and the total number of receiving coils is n, and their labels are 1, 2, …, n;

[0083] Detection depth It can be obtained according to the skin depth formula where, is the transmitting frequency, is the magnetic permeability of the underground medium, is the conductivity of the underground medium, and the attenuation coefficient of the electromagnetic wave during propagation ;

[0084] Step B specifically includes: defining the vertical magnetic field component collected by the receiving coil array 3 as , using the amplitude and position of the receiving coil as constraints, performing correlation stacking processing on the data received by the array, and obtaining the expression of the normalized anomaly ratio Q of the background fields in the target area and the reference area;

[0085] Performing constrained stacking on the response H of the receiving coil array 3 in the target area to obtain the stacked response G of the target area, and the specific formula is as follows:

[0086] ;

[0087] where, for n receiving coils, x is the receiving coil number, x ∈ [1, n], is the distance from the xth receiving coil to the 1st receiving coil, is the position compensation coefficient, is the amplitude compensation coefficient, i is the imaginary unit, and its square is equal to -1, H x represents the vertical magnetic field component collected by the xth receiving coil, e represents the natural number approximately equal to 2.718, represents the attenuation coefficient of the electromagnetic wave during propagation;

[0088] Performing direct stacking on the response of the background field receiving coil array 3 in the reference area to obtain the stacked response of the reference area, and the specific formula is as follows:

[0089] ;

[0090] where, represents the vertical magnetic field component of the background field collected by the xth receiving coil;

[0091] The ratio of the superimposed signal to the background field reference signal is Q. When Q is at its maximum, it is the most sensitive to anomalies in the target detection area, and this is the optimal interpretation result. The specific formula is as follows:

[0092] .

[0093] Step C specifically includes: introducing the Reptilian search algorithm (RSA) in the meta-heuristic algorithm to obtain the constraint parameters and values. RSA is a global search by simulating the hunting behavior of crocodiles. Since the objective function of the optimization algorithm usually can only find the minimum value, therefore, RSA takes -Q as the objective function to obtain the optimal constraint parameters and values.

[0094] Step D specifically includes: substituting the optimal constraint parameters and into the calculation formula of the normalized anomaly ratio Q in Step B to obtain the optimal normalized anomaly ratio Q, and finally obtaining the normalized anomaly data of a certain point in the survey area and the background field area. Repeat this operation until all measurement points on the survey line are completed to obtain the underground structure of the target area.

[0095] Example 3: As Figure 4 shown, how to obtain the optimal constraint parameters and values through the Reptilian search algorithm. The method includes:

[0096] First of all, the objectives to be optimized are and , so the optimization dimension s of the algorithm is 2. Subsequently, set the initial parameter population size N, the upper limit and the lower limit of the search range and the maximum number of iterations T;

[0097] According to the initial parameters, perform population initialization: the position of the i-th individual in the j-th dimensional space is x (i,j) , is a random number, and each individual in each iteration is regarded as a candidate solution;

[0098] ;

[0099] When the maximum number of iterations is not reached, calculate the fitness function and the current optimal solution under the initial parameters. In the present invention, the fitness function is the same as the objective function, set as -Q;

[0100] Subsequently, update the parameter evolution factors , R, P and :

[0101] ;

[0102] ;

[0103] ;

[0104] ;

[0105] Among them, evolutionary factors Randomly select a decreasing value between 2 and -2 throughout the number of iterations; Used to reduce the search range; is the percentage difference between the optimal solution and the current solution, is the j-th dimension hunting operator in the i-th solution; t is the current iteration number, is a random number; is the j-th dimension position of the current best solution, is a random number, represents the j-th dimension position of the r2-th candidate solution, It is a minimum value used to ensure that the denominator is not 0. In this invention, it is set to 0.001 based on experience; It is a sensitive parameter that controls the difference between candidate solutions during the iteration process. In this invention, it is set to 0.1 based on experience. is the average position of the i-th individual solution, and is the maximum and minimum value of the j-th dimension; T is the maximum number of iterations;

[0106] ;

[0107] Among them, s is the optimization dimension, x (i,j) is the position of the i-th individual in the j-dimensional space;

[0108] After the parameter update is completed, the search phase begins, which can be divided into two phases: the encirclement phase and the hunting phase;

[0109] The encirclement phase can be divided into two strategies: walking off the ground and walking close to the ground. The mathematical model for this phase is:

[0110] ;

[0111] in, is the position of the i-th individual in the j-dimensional space after t+1 iterations, is a random number, Represents the j-th dimension position of the r1-th candidate solution;

[0112] The hunting phase can be divided into two strategies: hunting coordination and hunting cooperation. In this phase, an approximate optimal solution may be found after several iterations, and the search will be intensified near the optimal solution. The mathematical model of this phase is:

[0113] ;

[0114] in, It is a sensitive parameter used to control the search accuracy. In this invention, it is set to 0.1 based on experience. is a random number;

[0115] Finally, the optimal solution in each iteration is saved. When the number of iterations reaches the maximum number of iterations T, the search is completed and the current optimal constraint parameters are returned. and The value of .

[0116] Example 4: Figure 5 As shown in the figure, the electromagnetic field calculation is performed in the MATLAB2022b programming environment to carry out the numerical simulation model of a certain measuring point of the present invention. The experiment uses the three-dimensional frequency domain finite difference method to obtain data. The calculation space size of the entire formation is 200m×100m×100m. The size of the air layer is the same as the formation size, and the resistivity of the air layer is 10 8 Ω·m, the resistivity of the underground background layer is 100Ω·m; the size of the anomaly is 10m×10m×20m, the depth from the center is 20m, the lateral distance is 27m, the distribution is symmetrical, and the resistivity of the anomaly is 300Ω·m; the excitation source is at the center and symmetrically distributed. To facilitate numerical simulation, its shape is set to square, the transmission frequency is 2kHz, the transmission current is 30A, and the side length is 2m; the side length of the receiving coil array 3 is 1m, the edge spacing is 1m, and the first receiving coil is 25m away from the center of the transmitting coil 2; the overall grid is divided by variable step size, the grid is divided into 0.1m where there are coils and anomalies, and the grid is sparse in other places.

[0117] like Figure 6 As shown in the experimental results of the model, the population size is set to 500, the number of iterations is set to 100, the search upper limit is set to 200, the lower limit is set to 0, and the iteration begins; it can be seen that the background field and the total field are not much different when the single coil is detected, as shown in Figure 6 As shown in (a); However, when the device and method of the present invention are used for detection, the background field and the total field are significantly different, as shown in FIG. Figure 6 As shown in (b), it is proved that the detection method proposed in the present invention is superior.

[0118] In summary, to further improve the detection efficiency and flexibility of the detection method, the detection device can be carried on a mobile platform. The emission source adopts a small loop form (with a side length less than 2 meters due to the complex urban space), and the receiving coil array 3 is used for reception to improve the signal coverage and system sensitivity. In addition, based on the signal correlation between the receiving coil arrays 3, the detection resolution and applicability in complex urban environments can be further enhanced.

[0119] It should be noted that in the present invention, it should be understood that although this specification is described according to the embodiments, not every embodiment only contains an independent technical solution. This narrative manner of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A small loop frequency domain electromagnetic array detection device for urban environment, characterized in that Including: A transmitting system for generating a periodic sinusoidal current; A transmitting coil connected to the transmitting system for transmitting a primary field underground, wherein the side length of the transmitting coil is less than 2 meters; A receiving coil array composed of a plurality of receiving coils for receiving secondary field signals induced by underground structures; A receiving system connected to the receiving coil array for processing the received secondary field signals; And a hinged mobile platform for carrying the receiving coil array and the receiving system and moving along a survey line; Wherein, the detection method of the small loop frequency domain electromagnetic array detection device for urban environment includes the following steps: Step S1: Arrange a transmitting coil and a receiving coil array in a target area and a reference area respectively, transmit a primary field underground through the transmitting system, and receive secondary field signals through the receiving coil array; Step S2: Perform correlation stacking processing on the vertical magnetic field components collected by the receiving coil array, and calculate the normalized anomaly ratio Q of the background fields of the target area and the reference area; Step S3: Introduce the reptile search algorithm in the meta-heuristic algorithm, and take maximizing the normalized anomaly ratio Q as the goal to obtain the optimal constraint parameters; Step S4: Substitute the obtained optimal constraint parameters into the calculation of the normalized anomaly ratio Q in Step S2 to obtain the optimal normalized anomaly ratio Q, repeat the operation until all measuring points are completed, and obtain the underground electrical structure of the target area; In Step S2, the specific steps of the correlation stacking processing include: Perform constraint stacking on the response H of the receiving coil array in the target area to obtain the stacked response G of the target area, and the specific formula is as follows: ； Among them, for n receiving coils, x is the receiving coil number, and x ∈ [1, n]. is the distance from the x-th receiving coil to the first receiving coil. is the position compensation coefficient. is the amplitude compensation coefficient, i is the imaginary unit, and its square is equal to -1. H x represents the vertical magnetic field component collected by the x-th receiving coil, and e represents the natural constant. represents the attenuation coefficient of the electromagnetic wave during propagation. Receive the background field receiving coil array response of the reference area Perform direct superposition to obtain the superposition response of the reference area , and the specific formula is as follows: ； Among them, represents the vertical magnetic field component of the background field collected by the x-th receiving coil; Calculate the initial normalized anomaly ratio Q of the background fields of the target area and the reference area, wherein the calculation formula of the normalized anomaly ratio Q is: 。 2. The urban environment small-loop frequency-domain electromagnetic array detection device according to claim 1, characterized in that, The number of receiving coils in the receiving coil array is n, numbered 1, 2,..., n, and the first receiving coil is the receiving coil closest to the transmitting coil.

3. The small-loop frequency-domain electromagnetic array detection device for urban environment according to claim 2, characterized in that, The hinged mobile platform can flexibly adjust the arrangement mode of the receiving coil array according to actual detection requirements.

4. The urban environment small-loop frequency domain electromagnetic array detection device according to claim 1, characterized in that In Step S1, the reference area is an area close to the target area in geographical location, with similar geological structures and few interference sources.

5. The urban environmental small-loop frequency-domain electromagnetic array detection device according to claim 1, characterized in that In Step S1, the transmitting frequency of the transmitting coil is a fixed frequency, and the receiving frequency of the receiving coil array is the same as the transmitting frequency, but the amplitude and phase change according to the underground electrical structure.

6. The urban environment small-loop frequency domain electromagnetic array detection device according to claim 1, characterized in that, In Step S3, the reptile search algorithm is used to optimize the constraint parameters, take -Q as the objective function, and dynamically adjust the evolution factor during the search process, and the value range of the evolution factor is between 2 and -2.

7. The urban environmental small-loop frequency-domain electromagnetic array detection device according to claim 6, characterized in that, The reptile search algorithm continuously iterates and optimizes to make -Q reach the minimum, so as to obtain the maximum anomaly response.

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