Extensible multi-element towed electromagnetic coil structure and working method

Abstract

The application discloses a scalable multi-array towed electromagnetic coil structure and a working method, and belongs to the field of towed transient electromagnetic detection equipment. The structure adopts a multi-array modular array design, one transmitting array element and two receiving array elements on the two sides of the transmitting array element form a modular working unit, and the compact connection of the array is realized by the common use of the receiving array elements of adjacent working units. The horizontal offset distance and the vertical distance between the transmitting array element and the receiving array element are constrained, the mutual inductance coefficient in the working unit approaches to zero, the primary field residual interference is suppressed at the physical level, and the shallow detection blind area is eliminated. Time division multiplexing technology is adopted to realize multi-unit round transmission and multi-channel signal synchronous acquisition, a spatial amplitude response matrix is constructed, and the accurate positioning of the center position and the geometric boundary of an underground abnormal body is realized. The application supports horizontal modular seamless expansion, significantly improves the scanning width and the detection efficiency, and can provide rich data basis for high-quality inversion of the underground abnormal body.

Description

Technical Field

[0001] This invention belongs to the field of towed transient electromagnetic detection equipment, specifically relating to an expandable multi-element towed electromagnetic coil structure and its working method. Background Technology

[0002] Currently, the towed transient electromagnetic method mainly employs a single-transmitter-single-receiver coil operating mode in engineering exploration. However, this conventional configuration reveals significant technical shortcomings in practical applications. On the one hand, the strong mutual inductive coupling between the transmitting and receiving coils makes it difficult to effectively attenuate the primary field, and the residual signal severely masks the secondary field information of the early response, thus creating a large shallow detection blind zone. On the other hand, during continuous towing, the single receiving coil has a large spatial sampling interval and low sampling density, making it difficult to meet the requirements for fine characterization of the three-dimensional spatial distribution of underground anomalies, and severely limiting the lateral positioning accuracy.

[0003] To address the aforementioned issues, some research has attempted to develop self-decoupled multi-channel detection devices and high-speed towing systems suitable for specific operating conditions. However, these existing technologies still have the following shortcomings: First, the system suffers from poor geometric adaptability and a lack of modular and scalable logic. Existing devices are typically designed for fixed detection widths, with their geometry and coil layout constrained by initial parameters. They lack a modular configuration mechanism to adapt to dynamic expansion of lateral coverage width under towing conditions. Therefore, when detection missions impose different scale requirements on coverage, it is difficult to achieve rapid deployment and adaptation by flexibly adding or removing channels, limiting the system's versatility in diverse engineering scenarios.

[0004] Second, the signal processing logic is simplistic and lacks lateral location discrimination capabilities. Existing technologies mainly focus on primary field suppression and decoupled acquisition of multi-channel signals, failing to utilize the inherent amplitude gradient characteristics between multiple channels to construct lateral location discrimination logic. This deficiency prevents the system from performing real-time, high-resolution discrimination of the boundary positions of underground anomalies during high-speed travel, thus making it difficult to meet the requirements of refined detection for lateral anomaly boundary identification. Summary of the Invention

[0005] In view of this, this invention proposes an scalable multi-element towed electromagnetic coil structure and its operating method, constructing a multi-channel modular array with rigorous and comprehensive geometric linkage constraints. This design systematically optimizes existing towed transient electromagnetic detection devices from both physical structure and positioning method perspectives. This invention aims to solve prominent problems in current technologies, such as large shallow blind zones, low single-channel detection efficiency, sparse spatial sampling, and inaccurate localization of underground anomalies. By introducing a modular, weakly coupled array structure and combining it with a positioning discrimination method based on multi-channel amplitude gradients, this invention achieves blind-zone-free shallow detection, high-density multi-channel spatial sampling, and significantly improves the positioning accuracy of underground anomalies.

[0006] The objective of this invention is achieved through the following technical solution: According to a first aspect of the present invention, an expandable multi-element dragged electromagnetic coil structure is provided, comprising: Arranged at equal intervals along the horizontal direction Each transmitting array element, and parallel array elements arranged in the plane above the transmitting array elements. There are 1 receiving array element, of which The integer is greater than or equal to 1; the transmitting element is a square coil; and the receiving element is a circular coil. A modular working unit is formed by a transmitting array element and two receiving array elements on its two adjacent sides. Two adjacent working units share a receiving array element located at the boundary. The lateral offset distance of the center of the receiving array element relative to the central axis of the transmitting array element in its working unit is: The lateral spacing between the central axes of two adjacent transmitting elements is And satisfy ; The vertical distance between the plane where the transmitting element is located and the plane where the receiving element is located is ; By matching the lateral offset distance Vertical distance This makes the mutual inductance coefficient between the transmitting and receiving array elements within the working unit... Approaching zero, in order to suppress residual interference of the primary field at the physical level and eliminate shallow detection blind zones.

[0007] Furthermore, the side length of the transmitting array element is Its two adjacent sides are parallel to the towing axis and the lateral expansion axis, respectively; the center of the receiving array element is located on the lateral central axis of the transmitting array element in its working unit.

[0008] Furthermore, the mutual inductance coefficient between the transmitting and receiving array elements within the working unit... Satisfying the piecewise linear integral constraint model: ; in, The first element of the launch array The mutual inductance component between the strip edge and the receiving array element.

[0009] Furthermore, the side length of the transmitting array element, the radius of the receiving array element, and the lateral offset distance... and vertical distance It can be scaled proportionally to the required detection depth and lateral scan width, and still meet the requirements after scaling. Geometric linkage constraints.

[0010] According to a second aspect of the present invention, a method for operating an expandable multi-element dragged electromagnetic coil structure is provided, which is implemented using the aforementioned expandable multi-element dragged electromagnetic coil structure, and includes the following steps: Step 1: The array coil is driven in time-division multiplexing mode. The pulse current generated by the transmitter is distributed to each transmitting array element according to a preset timing sequence via a multiplexer. Step 2: Each modular work unit operates in a modal time-sharing manner: in the... In modal mode, drive the first Each launch array element A primary field is generated, and the two receiving array elements adjacent to the transmitting array element are simultaneously controlled to collect the induced voltage signal generated by the underground medium. Step 3: Summarize the induced voltage signals collected by each modular working unit to construct a spatial response matrix; based on the gradient characteristics in the spatial response matrix, execute the following sub-steps sequentially to determine the location of the underground anomaly: Perform lateral interval determination to determine the distribution range of underground anomalies in the horizontal direction; Perform cross-unit boundary positioning to determine whether underground anomalies cross the junction between work units and locate the boundary position; Geometric boundary identification is performed to extract the boundary features of underground anomalies to determine their geometric contours.

[0011] Furthermore, the time-sharing switch in step 1 is a single-pole switch. Throw switch, single-pole The toggle switch drives the circuit sequentially by periodically switching the conduction channels. Each transmitting element emits cyclically, ensuring that only one transmitting element is active at any given instant. Each work unit switches its working mode cyclically according to a preset time sequence.

[0012] Furthermore, the specific method for constructing the spatial response matrix in step 3 includes: First, the induced voltage signals collected by each receiving channel are sequentially pre-amplified and filtered to remove primary field interference and environmental noise. Then, the time-domain peak level of the induced voltage signal of each receiving channel is extracted from the conditioned signal according to mode. ;in The mode number represents the mode of operation. Each mode corresponds to a single transmitter element that operates independently in sequence. , The spatial arrangement numbering of the receiving array elements. ; Finally, by modal number The row index is used to number the spatial arrangement of the receiving array elements. As a column index, the time-domain peak level of the extracted induced voltage signal is used. The permutation is constructed as a spatial response matrix .

[0013] Further, the lateral interval determination includes: acquiring the induced voltage value of each receiving channel along the arrangement direction of the receiving array elements, and constructing a spatial distribution curve of the induced voltage changing with the channel position; identifying local maxima points in the spatial distribution curve, wherein, for non-edge channels, if the induced voltage value of a channel is simultaneously greater than or equal to the induced voltage value of its left adjacent channel and greater than or equal to the induced voltage value of its right adjacent channel, then the channel is determined to be a local maximum point; for edge channels, if the induced voltage value of a channel is greater than or equal to the induced voltage value of its only existing adjacent channel, then the channel is determined to be a local maximum point; determining the receiving channel corresponding to the local maximum point as the target channel; and determining the time-domain peak level of the induced voltage signal of the target channel. When the induced voltage value of the target channel is significantly higher than that of the adjacent channel and exhibits a local peak envelope, and the difference between the induced voltage value of the target channel and the induced voltage value of the adjacent channel exceeds a preset threshold, it is determined that the center lateral coordinate of the underground anomaly is located directly below the receiving array element corresponding to the target channel.

[0014] Furthermore, the cross-unit boundary positioning includes: configuring the receiving array element at the boundary of two adjacent transmitting array elements as a common receiving array element; acquiring the previous induced voltage value collected when the common receiving array element drives one of the two adjacent transmitting array elements to excite a location once under the previous excitation mode, and the subsequent induced voltage value collected when the common receiving array element drives the same transmitting array element to excite a location once under the subsequent excitation mode; when both the previous induced voltage value and the subsequent induced voltage value exceed a preset threshold, and both exhibit local high amplitude characteristics, it is determined that the underground anomaly is located in the lateral boundary area of ​​the two adjacent transmitting array elements.

[0015] Furthermore, the geometric boundary identification includes: summarizing the time-domain peak levels of the induced voltage signals from all receiving channels within a complete scan cycle. Using the horizontal physical coordinates of each receiving array element as the horizontal axis and the induced voltage value as the vertical axis, a spatial response envelope curve is fitted to form a spatial response envelope curve. The maximum gradient point in the spatial response envelope curve where the induced voltage value decays from a local peak to both sides is identified as the horizontal edge marker point of the underground anomaly. The horizontal span of the underground anomaly is calculated based on the known physical distance between adjacent edge marker points.

[0016] Through the above design scheme, the beneficial effects of this invention compared with the prior art are as follows: First, at the physical level, shallow blind zones are completely eliminated, improving early signal quality: this is achieved by precisely matching the lateral offset distance between the receiving and transmitting array elements. Vertical distance This invention reduces the mutual inductance coefficient between the transmitting and receiving array elements within the working unit. Approaching zero; this zero-coupling physical design suppresses the primary field residue generated at the moment of transmission current cutoff from the source, avoiding its aliasing with the early secondary field signal, thereby effectively eliminating the shallow detection blind zone; compared with the traditional single-transmitter-single-receiver coil system, the present invention can significantly improve the acquisition signal-to-noise ratio and resolution of the response to the shallow underground medium, thereby effectively enhancing the detection and identification capability of near-surface small anomalies (such as cavities, fissures, buried objects or pollution plumes, etc.), and realizing high-precision imaging of shallow structures and anomalies; Second, it achieves high-density spatial sampling, significantly improving the efficiency of detection operations: This invention employs a horizontal multi-channel array arrangement, which can acquire data through a single drag scan. The spatial response profile of the physical channel; combined with time-division multiplexing technology, the system can complete spatial sampling of multi-dimensional data within one transmission cycle, and the effective detection width expands linearly with the increase of the number of working units; this mode completely changes the status quo of low sampling density and long operation cycle of traditional single-channel systems, and provides rich and dense raw data support for the establishment of high-quality underground three-dimensional resistivity models; Third, the positioning and discrimination logic is rigorous and meticulous, and the lateral spatial resolution is significantly improved: This invention fully utilizes the spatial sensitivity distribution characteristics of the receiving array elements to the secondary field response to construct a lateral positioning and discrimination mechanism based on amplitude gradient. This mechanism is rigorous and self-consistent at the discrimination logic level, and can effectively suppress positioning ambiguity, thereby achieving a substantial enhancement of spatial resolution in the lateral dimension. Specifically, by identifying the peak coordinates of the induced voltage values ​​in the spatial response matrix, the lateral center position of the underground anomaly can be accurately located. Utilizing the dual response characteristics of the common receiving channel, the boundary state of the underground anomaly between working units can be effectively identified. This positioning and discrimination mechanism overcomes the limitation of traditional single-channel detection, which can only evaluate two-dimensional profiles, and achieves accurate positioning of the boundary and orientation of the underground anomaly. Fourth, it has strong modular scalability and extremely high engineering adaptability: the work unit design adopted in this invention has rigorous and meticulous geometric linkage constraints. It supports seamless horizontal expansion based on detection bandwidth requirements while maintaining weak coupling consistency within each unit. Element parameters can be scaled proportionally according to mission requirements (such as detection depth and resolution). Combined with a non-magnetic towed platform and time-division multiplexing anti-interference mechanism, the system can maintain high operational stability in complex terrain and electromagnetic environments, demonstrating significant engineering application value. Attached Figure Description

[0017] The accompanying drawings are provided to further illustrate the invention and form part of this application. The illustrative embodiments and descriptions of the invention are used to understand the invention and do not constitute an undue limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the geometric layout of the three transmitting coils and four receiving coils array in an embodiment of the present invention; Figure 2 The mutual inductance coefficient between the transmitting and receiving array elements within the working unit of this embodiment of the invention. Lateral offset distance A graph showing the changing relationship; Figure 3 This embodiment of the invention is based on a single blade. A schematic diagram of the time-division multiplexing process and its circuit logic state implemented by a throw switch; Figure 4 This is a schematic diagram of a conductive ring simulated anomaly model used to verify multi-channel positioning capability in an embodiment of the present invention; Figure 5 This is a three-dimensional surface diagram showing the evolution of the induced voltage value on the first receiving coil with time and spatial position when the first working unit is in the excited state according to an embodiment of the present invention. Figure 6This is a three-dimensional surface diagram showing the evolution of the induced voltage value on the second receiving coil with time and spatial position when the first working unit is in the excited state according to an embodiment of the present invention. Figure 7 This is a three-dimensional surface diagram showing the evolution of the induced voltage value on the second receiving coil with time and spatial position when the second working unit is in the excited state according to an embodiment of the present invention. Figure 8 This is a three-dimensional surface diagram showing the evolution of the induced voltage value on the third receiving coil with time and spatial position when the second working unit is in the excited state according to an embodiment of the present invention. Figure 9 This is a three-dimensional surface diagram showing the evolution of the induced voltage value on the third receiving coil with time and spatial position when the third working unit is in the excited state according to an embodiment of the present invention. Figure 10 This is a three-dimensional surface diagram showing the evolution of the induced voltage value on the fourth receiving coil with time and spatial position when the third working unit of this embodiment is in the excited state. Figure 11 This is a graph showing the change of induced voltage values ​​on each receiving coil over time when the multi-element dragged electromagnetic coil structure is working as a whole, as described in this embodiment of the invention. Figure 12 This is a flowchart illustrating the working method of the expandable multi-element dragged electromagnetic coil structure in an embodiment of the present invention. Explanation of reference numerals in the attached diagram: 1-First transmitting coil; 2-Second transmitting coil; 3-Third transmitting coil; 4-First receiving coil; 5-Second receiving coil; 6-Third receiving coil; 7-Fourth receiving coil; 8-Power supply; 9-Receiver; 10-Transmitter; 11-Single-pole three-throw switch; 12-Conductive ring. Detailed Implementation

[0018] This invention provides a scalable multi-element towed electromagnetic coil structure and its operating method. By constructing a multi-channel modular electromagnetic array with strict geometric linkage constraints, it systematically reconstructs existing towed transient electromagnetic detection systems from two dimensions: physical structure and spatial positioning method. Specifically, at the structural level, a modular, weakly coupled scalable array coil structure is proposed, supporting flexible configuration of multiple array elements and fundamentally improving spatial sampling density and shallow coverage capability. At the methodological level, a positioning discrimination mechanism based on multi-channel amplitude gradient information is introduced, utilizing the response differences of each channel within the array to achieve high-resolution spatial positioning of underground anomalies. Through the high synergy of the above structure and method, this invention can achieve blind-zone-free continuous detection in shallow areas; high-density spatial sampling brought about by multi-channel parallel acquisition; and accurate positioning and identification of underground anomalies. This invention systematically integrates a modular, weakly coupled array structure with geometric linkage constraints and a multi-channel amplitude gradient positioning method to form a complete technical closed loop, which differs from the traditional approach where structural improvement and positioning algorithms are independent processes.

[0019] Specifically, the present invention adopts the following technical means: I. Array Topology and Geometric Arrangement Logic: This invention comprises an array coil consisting of a transmitting array and a receiving array. The transmitting array consists of... Each launch element ( ) along the lateral direction (perpendicular to the towing direction) The receiving array is composed of equally spaced axes; Each receiving array element ( The coils are arranged in parallel on the plane above the transmitting element; the transmitting element is a square coil and the receiving element is a circular coil. This combination of coil shapes can maximize the wiring area and effectively reduce edge effects and anisotropic interference.

[0020] Divided according to the "one transmit, two receive" principle into The first modular work unit, the first Each working unit consists of a launch array element. and the receiving array elements on its left and right sides and receiving array elements Composition: Two adjacent working units share a single receiving array element located in the boundary region.

[0021] The array satisfies global geometric linkage constraints: the lateral offset distance of the center of the receiving array element relative to the central axis of the transmitting array element in its working unit is set as follows. The lateral spacing between the central axes of two adjacent transmitting elements is Then it must satisfy This ensures that the common receiving array element is in a geometrically symmetrical, weakly coupled position when two adjacent working units are rotating.

[0022] II. Physically Zero-Coupling Design and Blind Zone Suppression Mechanism: Each working unit employs a weakly coupled parameter matching design. A calculation model for the mutual inductance coefficient between the transmitting and receiving array elements is established. Precisely calibrate vertical distance Lateral offset distance The optimal combination ensures that the mutual inductance coefficient between the transmitting and receiving elements within the working unit is maximized. Approaching zero. The mutual inductance coefficient between the transmitting and receiving elements within the working unit is... The calculation uses a piecewise integral model: ,in , , and These are the mutual inductance components between the four sides of the transmitting element and the receiving element. By making the induced magnetic flux generated by the four sides of the transmitting element in the receiving circuit cancel each other out, the residual primary field signal at the moment of transmission current cutoff is suppressed at the physical structure level, thereby eliminating the shallow blind zone in the early detection stage.

[0023] III. Time-division multiplexing technology and multi-channel data acquisition methods: Combination Figure 12 As shown, the system uses a single-pole... The system uses a time-sharing switch to allocate energy. During operation, the system sequentially activates each transmission channel according to a predetermined time sequence. Each working unit operates in a modal cyclic manner. Each mode corresponds to a transmitter element that operates independently and sequentially. In any given... In the first mode, the system drives the first... Each launch array element A pulse field is emitted, and the corresponding two receiving array elements are controlled to synchronously acquire the induced voltage signal from the underground medium.

[0024] Within a complete scan cycle driven by time-division multiplexing, the system constructs the spatial response matrix of the induced voltage in the underground medium. Extract the first one in sequence Each launch array element In the transmit mode, the corresponding two receiver array elements and The time-domain peak level of the induced voltage signal is calculated and mapped to the spatial response matrix. The Middle line, number Column and the line, number The element values ​​of the column; where, in the constructed spatial response matrix Middle row index ( This strictly corresponds to the operating timing of each transmitting element, i.e., the mode number. Each mode corresponds to one transmitting element that operates independently in sequence. Column Index ( This corresponds to the spatial arrangement number of the receiving array elements, i.e., the receiving channels at different spatial locations. Therefore, the matrix elements... The physical meaning is: in the first Type 1 mode (the first) Each launch array element Under the first pulse field, the first... The time-domain peak level of the induced voltage signal acquired by the receiving array element (extracted after pre-amplification and filtering conditioning). This forms the spatial response matrix. The spatial electromagnetic response intensity distribution of each physical channel within the full coverage area of ​​the array under different excitation and observation positions is described, realizing high-density spatial sampling in the lateral direction.

[0025] IV. Subsurface anomaly localization method based on amplitude gradient characteristics: Combination Figure 12 As shown, by utilizing the spatial sensitivity characteristics of the receiving array elements to the induced voltage signal, and through the spatial response matrix... Accurate localization can be achieved through gradient analysis: 1. Lateral Interval Determination: Real-time comparison of the induced voltage values ​​acquired by each receiving channel. If the time-domain peak level of the induced voltage signal of a certain receiving channel is significantly higher than that of the adjacent channels and exhibits a local peak envelope, then it is determined that the center of the underground anomaly is located directly below the receiving array element corresponding to that receiving channel.

[0026] 2. Cross-unit boundary positioning: The system compares the signal strengths acquired by the same common receiving array element in two adjacent modes. It acquires the previous induced voltage value collected when the common receiving array element drives one of the two adjacent transmitting array elements to excite a location in the previous excitation mode, and the subsequent induced voltage value collected when the same transmitting array element drives a location to excite a location in the subsequent excitation mode. When both the previous and subsequent induced voltage values ​​exceed a preset threshold and both exhibit local high-amplitude characteristics, the underground anomaly is determined to be located in the lateral boundary region between the two adjacent transmitting array elements. Due to the symmetry of its spatial geometric relationship with the two excitation magnetic fields and the observation point, the common receiving array element will detect significant high-amplitude induced voltage values ​​in both the preceding and following time sequences, and the values ​​will be close. Through this extraction of response characteristics of the same physical channel under different excitation modes, precise identification of the location of anomalies in the transition zone between working units is achieved.

[0027] 3. Geometric Boundary Identification: First, the system aggregates the time-domain peak levels of the induced voltage signals acquired by all receiving channels within a complete scan cycle. Using the lateral physical coordinates of each receiving element as the horizontal axis and the induced voltage value as the vertical axis, a spatial response envelope curve reflecting the underground electrical properties is fitted. Second, by identifying abrupt changes in amplitude within the spatial response envelope curve where the amplitude rapidly decays from a local peak to both sides (i.e., gradient maxima points), the lateral edge markers of the anomaly are used. Combined with the known physical distances between each sampling channel, the spatial distance between two edge marker points is calculated, thereby quantitatively assessing the lateral span of the underground anomaly. Finally, the system considers the distance along the direction of travel (…). The system uses multi-cycle scanning data during the continuous movement of the axis to record the center position of the anomaly identified in each cycle. By fitting the migration trajectory of the anomaly center as it moves, the system can quantitatively assess the extension direction and orientation of the underground anomaly.

[0028] V. Modular and expandable design: The array of this invention supports seamless horizontal scaling. Through... Axial direction according to lateral spacing By linearly increasing the number of transmitting array elements and correspondingly increasing the number of receiving array elements and common receiving channels, the lateral coverage width of a single scan can be multiplied while maintaining the zero-coupling performance of a single working unit and the unchanged positioning logic.

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the following description, in conjunction with the accompanying drawings and a three-transmitter-four-receiver coil, is provided. The present invention will be further described in detail below with reference to exemplary embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. It should be noted that in the present invention, "first," "second," "third," and "fourth" are used to distinguish different objects, rather than to describe a specific order.

[0030] This embodiment provides an expandable multi-element towed electromagnetic coil structure. The entire system is mounted on a rigid towed platform made of non-metallic, non-magnetic composite material. The rigid towed platform is made of non-metallic, non-magnetic composite material selected from one or more of glass fiber reinforced plastic (GFRP), epoxy resin-based composite material, polyvinyl chloride (PVC), high-density polyethylene (HDPE), or polyetheretherketone (PEEK) to avoid induced eddy current interference generated by the metal frame at the moment the transmit pulse is turned off. Figure 1As shown, a preferred embodiment of the present invention is a three-transmitter-four-receiver coil array. This array consists of three transmitting elements and four receiving elements, which, for ease of description, are respectively designated as the first transmitting coil 1, the second transmitting coil 2, the third transmitting coil 3, the first receiving coil 4, the second receiving coil 5, the third receiving coil 6, and the fourth receiving coil 7. The transmitting elements are laid on a reference plane (Z=0), and the receiving elements are laid vertically above the transmitting elements at a height of [missing information]. In the parallel plane.

[0031] This embodiment divides the three-transmitter-four-receiver coil array into three closely connected modular working units. Each working unit follows a "one-transmitter, two-receiver" physical layout: the first working unit consists of a first transmitting coil 1 and symmetrically distributed first receiving coils 4 and second receiving coils 5 on its left and right sides; the second working unit consists of a second transmitting coil 2 and symmetrically distributed second receiving coils 5 and third receiving coils 6 on its left and right sides; the third working unit consists of a third transmitting coil 3 and symmetrically distributed third receiving coils 6 and fourth receiving coils 7 on its left and right sides. The second receiving coil 5 serves as the receiving channel for both the first and second working units, and the third receiving coil 6 serves as the receiving channel for both the second and third working units. This multiplexing logic allows the array to maintain continuous detection coverage while significantly reducing the total number of receiving channels, thus lowering system load and hardware costs.

[0032] In this embodiment, the physical specifications and spatial coordinates of each array element are precisely calibrated to achieve zero-coupling balance; specifically, Array element specifications: The side lengths of the first transmitting coil 1, the second transmitting coil 2, and the third transmitting coil 3 are all set to 0.5m, and the number of coil turns is... All are set to 40 turns; the radii of the first receiving coil 4, the second receiving coil 5, the third receiving coil 6, and the fourth receiving coil 7 are... All are set to 0.1m, and the number of coil turns All are set to 100 turns.

[0033] Weak coupling height: Sets the vertical distance between the receiving plane and the transmitting plane. It is 0.1m.

[0034] Geometric linkage constraint: Set the lateral offset distance from the center of the receiving array element to the center axis of the transmitting array element of its corresponding working unit as... In this embodiment, the solution is obtained based on the mutual inductance model. To ensure that the common receiving array element is at a zero-coupling point during the rotation of adjacent working units, the lateral spacing between the central axes of adjacent transmitting array elements is set. Geometric linkage must be satisfied ,Right now .

[0035] Through the above Due to the arrangement constraints, the second receiving coil 5 is located to the right of the first transmitting coil 1. At the offset point, it is also located to the left of the second transmitting coil 2. This offset ensures the consistency of physical symmetry and weak coupling performance of the array as a whole during the lateral expansion process.

[0036] To eliminate the shallow blind zone in the early stages of detection at the physical level, it is essential to ensure that each working unit is in a state of zero-coupling equilibrium. Based on the symmetry of the array structure, mutual inductance analysis is performed using the first transmitting coil 1 and the first receiving coil 4 in the first working unit as an example, resulting in the zero-coupling spatial parameter combination. This can be extended to all working cells in the array. For example... Figure 3 As shown, the center of the first transmitting coil 1 is set at the origin. The center coordinates of the first receiving coil 4 are: According to Neumann's formula, the mutual inductance coefficient between the first transmitting coil 1 and the first receiving coil 4 is... The calculation logic is as follows: the first side of the first transmitting coil 1 is parallel to... shaft edge Positive direction ( ); the second side of the first transmitting coil 1 is parallel to shaft edge Positive direction ( The third side of the first transmitting coil 1 is parallel to... shaft edge negative direction ( The fourth side of the first transmitting coil 1 is parallel to... shaft edge negative direction ( Mutual inductance coefficient The algebraic sum of the contributions of the four edges to the receiving loop, i.e. .

[0037] The specific piecewise integral expressions for the mutual inductance coefficients of each side are as follows: ; ; ; ; In the above integral, Indicates the first transmitting coil 1 The straight-line distance between the infinitesimal element on the edge and the infinitesimal element on the first receiving coil 4. The geometric constraint equations are as follows: ; ; ; ; In the above formulas, , , and These are the mutual inductance coefficient components between the four sides of the first transmitting coil 1 and the first receiving coil 4, respectively; The number of turns of the first transmitting coil 1; The number of turns of the first receiving coil 4; The vacuum permeability; This is half the length of the first transmitting coil 1; The radius of the first receiving coil 4; The polar coordinates of the infinitesimal element on the first receiving coil 4 relative to its center; The first transmitting coil 1 is parallel to Linear integral variables on the edges of the axis; The first transmitting coil 1 is parallel to Linear integral variables on the edges of the axis; , , and These are the straight-line distances from the micro-element on the first side to the fourth side of the first transmitting coil 1 to the micro-element on the first receiving coil 4, respectively. The vertical distance between the plane containing the first receiving coil 4 and the plane containing the first transmitting coil 1; It is the lateral offset distance of the center of the first receiving coil 4 relative to the central axis of the first transmitting coil 1 in its working unit.

[0038] like Figure 2 As shown, a function is established for the mutual inductance model to obtain the mutual inductance coefficient. Lateral offset distance The response curve changes with vertical height. When it remains unchanged, as the center of the first receiving coil 4 moves laterally... Axial outward offset, mutual inductance coefficient It gradually decreases from the positive direction (increasing mutual inductance) and passes through the zero point of the horizontal axis. Let... In this embodiment, the optimal lateral offset distance is accurately solved. In this specific spatial coordinate system, the primary field excited by the first transmitting coil 1 achieves a dynamic equilibrium state where the positive and negative magnetic fluxes within the loop formed by the first receiving coil 4 dynamically cancel each other out. At this point, the induced voltage value generated by the primary field on the first receiving coil 4 is theoretically zero, and the system eliminates mutual inductance interference at the physical structure level. Based on the determined... Due to the arrangement constraints, all common channels in the array can synchronously reach this equilibrium state in time-division multiplexing mode, thus providing a clean physical background for capturing weak early underground induced voltage signals.

[0039] like Figure 3 As shown, in order to acquire multi-channel high-density sampling data within a single detection cycle and eliminate electromagnetic interference within a large-scale array, this system adopts a single-pole-based approach. The energy scheduling mechanism of the single-pole triple-throw switch. In this embodiment, the transmitter 10 sequentially drives the three modular working units to switch cyclically via the single-pole triple-throw switch 11. The specific process is as follows: First mode: Single-pole triple-throw switch 11 turns on the first channel, driving the first transmitting coil 1 to transmit a pulse field; at the same time, receiver 9 locks on and collects the induced voltage signals collected by the first receiving coil 4 and the second receiving coil 5.

[0040] Second mode: Single-pole triple-throw switch 11 switches to the second channel, driving the second transmitting coil 2 to work; synchronously controls the second receiving coil 5 and the third receiving coil 6 to collect the induced voltage signal, realizing the horizontal translation and overlap of the detection area.

[0041] Third mode: Single-pole triple-throw switch 11 switches to the third channel, driving the third transmitting coil 3 to transmit; synchronously controlling the third receiving coil 6 and the fourth receiving coil 7 to collect the induced voltage signal.

[0042] Within a complete scan cycle of the time-division multiplexing driver, the system is constructed according to the following logic. 3D response matrix Within a complete scan cycle, the first [number] [item] is extracted sequentially. Modal 1 Each launch array element When activated, the time-domain peak levels of the two induced voltage signals of the corresponding two receiving array elements are measured and mapped to a spatial response matrix. The element values ​​are filled in using the following method: the response values ​​of the first receiving coil 4 and the second receiving coil 5 corresponding to the first mode are filled in. , The response values ​​of the second receiving coil 5 and the third receiving coil 6 corresponding to the second mode are filled in. , The response values ​​of the third receiving coil 6 and the fourth receiving coil 7 corresponding to the third mode are filled in. , Matrix row index Corresponding modal number, column index The spatial response matrix is ​​formed by corresponding spatial numbering of the receiving array elements. The spatial electromagnetic response intensity distribution within the array's coverage area is fully described.

[0043] Receiver 9 and transmitter 10 are respectively connected to power supply 8. The function of power supply 8 is to provide power to each module of receiver 9 and transmitter 10. The transmitter 10 includes a DC-DC adjustable constant current source, an H-bridge chopper circuit, and a transmission control unit. The receiver 9 includes a microcontroller, a multi-channel synchronous data acquisition module, and four receiving channels. Each receiving channel is equipped with an overvoltage protection circuit, a preamplifier, and a signal conditioning circuit. The four receiving channels correspond to the first receiving coil 4, the second receiving coil 5, the third receiving coil 6, and the fourth receiving coil 7, respectively. It should be noted that the specific circuit structures of the DC-DC adjustable constant current source, the H-bridge chopper circuit, the transmission control unit, the microcontroller, the multi-channel synchronous data acquisition module, the overvoltage protection circuit, the preamplifier, and the signal conditioning circuit are common knowledge / existing technology in the field. This invention organically integrates and consolidates the above-mentioned devices or modules into a whole. As for each individual device or module, the specific structure for realizing its respective function already exists in the prior art. The protocols, software, or programs involved in the operation of each device and / or module also already exist in the prior art and are fully known to those skilled in the art, so they will not be described in detail here.

[0044] like Figure 4 As shown, to verify the lateral positioning capability of the multi-channel array, this embodiment establishes a physical model including an underground simulated anomaly (conductive ring 12). The plane containing the array coils is set as the XOY plane, and the vertical distance directly below the array is... At that location, a circular conductive ring 12 with a radius of 0.05m is set.

[0045] Experimental procedure: Simulate the towing process, and set the conductive ring 12 along... The system performs a horizontal axis translation scan with a step size of 0.01m, sequentially passing under each working unit. The system records the induced voltage response of all channels using the aforementioned time-division multiplexing mode, acquiring detection data of the array at different spatial locations.

[0046] Early signal purity analysis: such as Figures 5 to 10The figure shows the three-dimensional response surface of the induced voltage as a function of time and spatial location when each working unit operates independently. Due to the zero-coupling physical design, the surface did not exhibit signal overload or severe oscillations caused by primary field residue in the early stage after the transmit current was turned off. This indicates that the early induced voltage signal captured by the receiving array element directly originates from the induced eddy current of the underground anomaly, verifying the effectiveness of this physical structure in eliminating shallow detection blind zones.

[0047] Spatial response extreme characteristics: From Figures 5 to 10 As can be seen from the curved surface, the induced voltage value exhibits a clear single-peak envelope characteristic in the horizontal direction. When the center of the conductive ring 12 is translated to be directly below a receiving element of the current acquisition unit, the observation distance reaches its shortest, and the receiving circuit's capture efficiency of the induced magnetic flux reaches its global highest value. Therefore, a significant energy peak is formed at the point where the horizontal coordinate of the curved surface coincides with the center of the receiving element. This physical characteristic provides reliable data criteria for subsequent precise positioning logic based on amplitude gradient.

[0048] Lateral positioning logic based on multi-channel amplitude gradient: such as Figure 11 As shown, the curves illustrating the changes in induced voltage values ​​acquired by the four receiving elements (denoted as the first receiving coil 4, the second receiving coil 5, the third receiving coil 6, and the fourth receiving coil 7, respectively) with the lateral position of the conductive ring 12 are displayed when the array is operating as a whole. Based on the above secondary field response, the system achieves precise positioning by executing the following discrimination logic: Peak positioning criterion: Real-time extraction of the induced voltage value matrix of the receiving channel corresponding to the first receiving coil 4, the second receiving coil 5, the third receiving coil 6, and the fourth receiving coil 7. For example... Figure 9 As shown by the curve's peak, the induced voltage value of a receiving channel will reach its peak when the anomalous object is directly below a certain receiving element. By identifying the channel corresponding to the maximum value in the spatial response matrix, the center coordinates of the anomalous object in the lateral expansion direction can be directly located.

[0049] Dual response characteristics in the boundary region: Utilizing the shared characteristics of the second receiving coil 5 and the third receiving coil 6, if an anomalous object is located in the boundary region between two adjacent transmitting elements, the corresponding shared receiving channel can detect significant high-amplitude signals with highly uniform intensity in its respective mode. Through this cross-element "dual response" comparison, the specific distribution of anomalous objects among the working elements can be effectively identified, compensating for the shortcomings of single-channel detection in lateral spatial resolution.

[0050] Geometric boundary identification: by... Figure 11By analyzing the gradient rate of change of the spatial response envelope curve, the system can calculate the lateral boundary span of the anomaly. This amplitude gradient based on the multi-channel physical spacing provides a dense spatial point cloud foundation for subsequent high-quality 3D imaging of underground targets.

[0051] In summary, this invention eliminates shallow blind zones through zero-coupling physical constraints and achieves rapid detection and accurate location of subsurface anomalies by utilizing a modular multi-channel array and amplitude gradient determination logic. This design not only significantly enhances lateral spatial resolution but also supports the technological leap from two-dimensional profile assessment to high-precision three-dimensional resistivity imaging from the data source, effectively meeting the refined detection needs of complex engineering environments.

Claims

1. An expandable multi-element dragged electromagnetic coil structure, characterized in that, include: Arranged at equal intervals along the horizontal direction Each transmitting array element, and parallel array elements arranged in the plane above the transmitting array elements. There are 1 receiving array element, of which The integer is greater than or equal to 1; the transmitting element is a square coil; and the receiving element is a circular coil. A modular working unit is formed by a transmitting array element and two receiving array elements on its two adjacent sides. Two adjacent working units share a receiving array element located at the boundary. The lateral offset distance of the center of the receiving array element relative to the central axis of the transmitting array element in its working unit is: The lateral spacing between the central axes of two adjacent transmitting elements is And satisfy ; The vertical distance between the plane where the transmitting element is located and the plane where the receiving element is located is ; By matching the lateral offset distance and vertical distance This makes the mutual inductance coefficient between the transmitting and receiving array elements within the working unit so that... Approaching zero, in order to suppress residual interference of the primary field at the physical level and eliminate shallow detection blind zones.

2. The expandable multi-element dragged electromagnetic coil structure according to claim 1, characterized in that, The side length of the transmitting array element is Its two adjacent sides are parallel to the towing axis and the lateral expansion axis, respectively; the center of the receiving array element is located on the lateral central axis of the transmitting array element in its working unit.

3. The expandable multi-element dragged electromagnetic coil structure according to claim 1, characterized in that, The mutual inductance coefficient between the transmitting and receiving elements within the working unit Satisfying the piecewise linear integral constraint model: ； in, The first element of the launch array The mutual inductance component between the strip edge and the receiving array element.

4. The expandable multi-element dragged electromagnetic coil structure according to claim 1, characterized in that, The side length of the transmitting array element, the radius of the receiving array element, and the lateral offset distance are specified. and vertical distance It can be scaled proportionally to the required detection depth and lateral scan width, and still meet the requirements after scaling. Geometric linkage constraints.

5. A working method for an expandable multi-element dragged electromagnetic coil structure, characterized in that, The scalable multi-element dragged electromagnetic coil structure according to any one of claims 1 to 4 is implemented by the following steps: Step 1: The array coil is driven in time-division multiplexing mode. The pulse current generated by the transmitter is distributed to each transmitting array element according to a preset timing sequence via a multiplexer. Step 2: Each modular work unit operates in a modal time-sharing manner: in the... In modal mode, drive the first Each launch array element A primary field is generated, and the two receiving array elements adjacent to the transmitting array element are simultaneously controlled to collect the induced voltage signal generated by the underground medium. Step 3: Summarize the induced voltage signals collected by each modular working unit to construct a spatial response matrix; based on the gradient characteristics in the spatial response matrix, execute the following sub-steps sequentially to determine the location of the underground anomaly: Perform lateral interval determination to determine the distribution range of underground anomalies in the horizontal direction; Perform cross-unit boundary positioning to determine whether underground anomalies cross the junction between work units and locate the boundary position; Geometric boundary identification is performed to extract the boundary features of underground anomalies to determine their geometric contours.

6. The operating method of the expandable multi-element towed electromagnetic coil structure according to claim 5, characterized in that, The multi-way time-sharing switch in step 1 uses a single-pole switch. Throw switch, single-pole The toggle switch drives the circuit sequentially by periodically switching the conduction channels. Each transmitting element emits cyclically, ensuring that only one transmitting element is active at any given instant. Each work unit switches its working mode cyclically according to a preset time sequence.

7. The operating method of the expandable multi-element dragged electromagnetic coil structure according to claim 5, characterized in that, The specific methods for constructing the spatial response matrix in step 3 include: First, the induced voltage signals collected by each receiving channel are sequentially pre-amplified and filtered to remove primary field interference and environmental noise. Then, the time-domain peak level of the induced voltage signal of each receiving channel is extracted from the conditioned signal according to mode. ;in The mode number represents the mode of operation. Each mode corresponds to a single transmitter element that operates independently in sequence. , The spatial arrangement numbering of the receiving array elements. ; Finally, by modal number The row index is used to number the spatial arrangement of the receiving array elements. As a column index, the time-domain peak level of the extracted induced voltage signal is used. The permutation is constructed as a spatial response matrix .

8. The operating method of the expandable multi-element dragged electromagnetic coil structure according to claim 7, characterized in that, The lateral interval determination includes: acquiring the induced voltage value of each receiving channel along the arrangement direction of the receiving array elements, and constructing a spatial distribution curve of the induced voltage changing with the channel position; identifying local maxima in the spatial distribution curve, wherein, for non-edge channels, if the induced voltage value of a channel is simultaneously greater than or equal to the induced voltage value of its left adjacent channel and greater than or equal to the induced voltage value of its right adjacent channel, then the channel is determined to be a local maximum; for edge channels, if the induced voltage value of a channel is greater than or equal to the induced voltage value of its only existing adjacent channel, then the channel is determined to be a local maximum; determining the receiving channel corresponding to the local maximum as the target channel; and determining the time-domain peak level of the induced voltage signal of the target channel. When the induced voltage value of the target channel is significantly higher than that of the adjacent channel and exhibits a local peak envelope, and the difference between the induced voltage value of the target channel and the induced voltage value of the adjacent channel exceeds a preset threshold, it is determined that the center lateral coordinate of the underground anomaly is located directly below the receiving array element corresponding to the target channel.

9. The operating method of the expandable multi-element dragged electromagnetic coil structure according to claim 7, characterized in that, The cross-unit boundary positioning includes: configuring the receiving array element at the boundary of two adjacent transmitting array elements as a common receiving array element; acquiring the previous induced voltage value collected when the common receiving array element drives one of the two adjacent transmitting array elements to excite a location once under the previous excitation mode, and the subsequent induced voltage value collected when the common receiving array element drives the same transmitting array element to excite a location once under the subsequent excitation mode; when both the previous induced voltage value and the subsequent induced voltage value exceed a preset threshold, and both exhibit local high amplitude characteristics, it is determined that the underground anomaly is located in the lateral boundary area of ​​the two adjacent transmitting array elements.

10. The operating method of the expandable multi-element dragged electromagnetic coil structure according to claim 7, characterized in that, The geometric boundary identification includes: summarizing the time-domain peak levels of the induced voltage signals from all received channels within a complete scan cycle. Using the horizontal physical coordinates of each receiving array element as the horizontal axis and the induced voltage value as the vertical axis, a spatial response envelope curve is fitted to form a spatial response envelope curve. The maximum gradient point in the spatial response envelope curve where the induced voltage value decays from a local peak to both sides is identified as the horizontal edge marker point of the underground anomaly. The horizontal span of the underground anomaly is calculated based on the known physical distance between adjacent edge marker points.

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