A geophysical electromagnetic target body simulation and detection device and method

Abstract

The present application belongs to the technical field of geophysical electromagnetic exploration, and provides a geophysical electromagnetic target body simulation and detection device and method. The present application is realized based on a programmable coil array. According to the simulation needs of a user, the connection mode of the coil array and the number of turns of each coil can be freely changed to construct target bodies of different scales and different electromagnetic parameters. According to the principle of electromagnetic induction, after a primary field is excited by an electromagnetic detection device, the programmable coil array will induce a corresponding secondary field. The electromagnetic detection device receives the secondary field and inverts and images. By comparing the inversion and imaging results with the construction mode of the target body, the accuracy of the detection results of the electromagnetic detection method and device is evaluated. The present application has a wide range of uses and good repeatability.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of geophysical electromagnetic exploration, and particularly relates to a geophysical electromagnetic target body simulation and detection device and method. BACKGROUND

[0002] The statements in this section merely provide background information related to the present application and do not necessarily constitute prior art.

[0003] Geophysical electromagnetic exploration is a non-invasive exploration technology for detecting underground structures and resource distribution by studying the spatial distribution or time variation of natural electromagnetic fields or artificially excited electromagnetic fields in underground media. During the research and optimization of geophysical electromagnetic detection methods and equipment by scholars, simulation devices (including numerical simulation and physical model simulation) used for experiments are indispensable. Numerical simulation refers to a method for simulating geophysical electromagnetic field response through mathematical equations and computer simulation technology. Finite element method and finite difference method are used to construct a three-dimensional electrical structure in a virtual environment and calculate electromagnetic signal propagation, attenuation and reflection processes. However, numerical simulation is only a simple abstract model, and the underground space is extremely complex. Therefore, the results of all numerical calculations are often quite different from the actual situation. Physical model simulation reproduces electromagnetic responses under real geological conditions by constructing scaled geological models and controllable electromagnetic field environments in the laboratory. However, existing simulation experiment devices only simply simulate geoelectric conditions with equal resistivity or single geoelectric unfavorable geological bodies, cannot dynamically adjust the size and electromagnetic parameters of target bodies, and can only support certain or a few detection methods and equipment.

[0004] In summary, the existing technology has a single simulation scene, high cost, poor test repeatability, and is difficult to comprehensively evaluate the detection capability of electromagnetic detection methods and equipment. SUMMARY

[0005] To solve the above problems, the present application proposes a geophysical electromagnetic target body simulation and detection device and method. The present application is realized based on a programmable coil array. According to the simulation needs of users, the connection mode of the coil array and the number of turns of each coil can be freely changed to construct target bodies with different sizes and different electromagnetic parameters. According to the principle of electromagnetic induction, after the primary field is excited by the electromagnetic detection equipment, the programmable coil array will induce the corresponding secondary field. The electromagnetic detection equipment receives the secondary field and performs inversion imaging. By comparing the inversion imaging results with the target body construction method, the accuracy of the detection results of the electromagnetic detection method and equipment can be evaluated. The present application is widely applicable and has good repeatability.

[0006] According to some embodiments, the present application adopts the following technical solutions:

[0007] A geophysical electromagnetic target body simulation device, comprising a programmable coil array and a programmable switch network, wherein:

[0008] The programmable coil array comprises a plurality of coil units arranged in a matrix, each coil unit comprising a plurality of sub-coil units, and a control switch is arranged between adjacent sub-coil units, and the length of the coil path / number of turns of each coil unit in use is determined by changing the state of the control switch;

[0009] The programmable switch network comprises a plurality of programmable switches, a plurality of programmable switches are arranged at intervals on each coil unit, and adjacent coil units are connected through at least one programmable switch, and the number of connected coil units and the connection path formed by each coil unit are changed by controlling the on-off state of each programmable switch;

[0010] The connection mode of the programmable coil array and the number of turns of each coil unit are changed by the states of the control switches and the programmable switch network to construct geophysical electromagnetic target bodies of different scales and different electromagnetic parameters.

[0011] As an optional implementation, the coil units are square coils, each square coil is the same size and arranged in a matrix, and each square coil has a programmable switch at each of its four corners.

[0012] As an optional implementation, each sub-coil unit has a metal contact and a control switch at both ends, adjacent sub-coil units are connected through the metal contacts and control switches, and the control switch is a programmable switch.

[0013] As an optional implementation, each sub-coil unit is connected in series through the control switches.

[0014] As an optional implementation, the control switch has a separate ID and a corresponding independent code bit, and the on-off of the corresponding control switch is controlled by pre-setting the code to determine the length of the coil path / number of turns of each coil unit in use.

[0015] A geophysical electromagnetic target body detection device, comprising the simulation device, a dynamic impedance matching module, and a signal receiving circuit, wherein:

[0016] The simulation device controls the programmable switch network and the control switches according to requirements to construct a target body of a predetermined scale and electromagnetic parameters, and receives a primary field excited by an electromagnetic detection device, and the programmable coil array generates a corresponding secondary field;

[0017] The dynamic impedance matching module detects the complex impedance of each sub-coil unit when the programmable coil array is used as a receiving coil, calculates the optimal matching, and performs dynamic compensation.

[0018] The signal receiving circuit is used for processing the received signal to eliminate or suppress the noise and interference in the measured magnetic field.

[0019] A geophysical electromagnetic target detection method based on the above device comprises the following steps:

[0020] According to the requirements, the scale and electromagnetic parameters of the constructed target are determined, the connection mode and the number of turns of each coil in the corresponding programmable coil array are calculated, the control switches and programmable switch networks are controlled, a two-dimensional coil array is formed, and the target construction is completed.

[0021] After determining the connection mode and the number of turns of each coil of the programmable coil array, the dynamic impedance matching module performs dynamic impedance matching to adjust the receiving channel impedance of the device to the best.

[0022] The receiving mode of the programmable coil array is started, the receiving control parameters of the programmable coil array are calibrated by exciting a standard test signal, and the background electromagnetic noise is obtained.

[0023] The electromagnetic detection equipment is laid out for detection, the programmable coil array is adjusted to the receiving mode, and the primary field signal excited by the electromagnetic detection equipment is sensed in real time.

[0024] According to the comparison between the inversion imaging result and the topological structure of the current programmable coil array, the interpretation of the primary field data sensed by the programmable coil array is performed to evaluate the detection effect.

[0025] According to the comparison result of the inversion imaging and the programmable coil array, the scale and electromagnetic parameters of the target in the next experiment are determined.

[0026] The above steps are repeated until the inversion imaging result meets the detection requirements, and the detection accuracy of the electromagnetic detection equipment is comprehensively evaluated according to the comparison between multiple inversion imaging results and the primary field data sensed by the programmable coil array.

[0027] Compared with the prior art, the beneficial effects of the present application are:

[0028] The geophysical electromagnetic target simulation device based on the programmable coil array can dynamically adjust the connection mode between coils and the number of turns to realize the construction of targets with different scales and different electromagnetic characteristics, and provides an experimental platform for the test and optimization of geophysical electromagnetic detection methods and equipment.

[0029] The method can continuously change the scale and electromagnetic parameters of the target body through simple programmable switch network / encoding instructions of the control switch, and can more accurately obtain the detection limit of the geophysical electromagnetic detection method and equipment, so as to evaluate the detection capability.

[0030] In order to make the above objectives, characteristics and advantages of the present application more apparent, clear and easy to understand, the following preferred embodiments are specifically described below with reference to the attached drawings. BRIEF DESCRIPTION OF DRAWINGS

[0031] The drawings constituting a part of the specification of the present application are used to provide further understanding of the present application, the schematic embodiments of the present application and the description thereof are used to explain the present application, and do not constitute improper limitation on the present application.

[0032] Figure 1 A schematic diagram of a programmable coil array in an embodiment;

[0033] Figure 2 A schematic diagram of a segmented coil and an encoding switch in an embodiment;

[0034] Figure 3 A flowchart of a test method in an embodiment. DETAILED DESCRIPTION

[0035] The present application will be further described below in combination with the drawings and embodiments.

[0036] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs.

[0037] It should be noted that the terms used herein are only for the purpose of describing specific embodiments, and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form, and in addition, it should be understood that when the terms "comprise" and / or "include" are used in the specification, they indicate the presence of a feature, step, operation, device, component and / or combination thereof.

[0038] The embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0039] Embodiment one

[0040] A geophysical electromagnetic target body simulation device, comprising a programmable coil array and a programmable switch network, wherein:

[0041] The programmable coil array comprises a plurality of coil units arranged in a matrix, each coil unit comprising a plurality of turns of coil units, as shown in Figure 1 The programmable coil array comprises a plurality of coil units arranged in a matrix, each coil unit comprising a plurality of turns of coil units, as shown in Figure 2 The programmable coil array comprises a plurality of coil units arranged in a matrix, each coil unit comprising a plurality of turns of coil units, as shown in

[0042] The programmable coil array comprises a plurality of coil units arranged in a matrix, each coil unit comprising a plurality of turns of coil units, as shown in

[0043] In this embodiment, as shown in Figure 1 The coil units are square coils, each square coil is the same size and arranged in a matrix, and each square coil has a programmable switch at each of its four corners.

[0044] The programmable coil array of this embodiment is composed of a series of square coils with variable connection modes and turns, using segmented coil technology and programmable switch network technology, which can freely adjust the connection mode and turns between coils according to user needs, and realize the construction of target objects with different sizes and electromagnetic parameters.

[0045] At the same time, the square coil can be used as a receiving coil to sense the primary field excited by the electromagnetic detection equipment in real time, and record the frequency, amplitude and phase of the primary field, etc. to provide raw data for the optimization of subsequent electromagnetic detection methods and equipment.

[0046] In this embodiment, each sub-coil unit has metal contacts and control switches at both ends, and adjacent sub-coil units are connected through metal contacts and control switches, and the control switches are programmable switches.

[0047] Each sub-coil unit is connected in series through each control switch.

[0048] In this embodiment, each control switch has a separate ID and corresponds to an independent code bit, and by pre-setting the code, the on-off of the corresponding control switch is controlled to determine the coil path length / turns of each coil unit in use.

[0049] The embodiment divides a single coil into multiple independent sub-coil units by using a segmented coil technology. Metal contacts are arranged at both ends of each sub-coil unit, and an encoding switch is arranged between the metal contacts. The number of turns of the coil is determined by controlling the on and off states of the switch. When the number of turns needs to be increased, the series switch of the adjacent sub-coil unit is closed, so that the current flows through multiple sub-coils in sequence to form a long path and multiple turns. When the number of turns needs to be reduced, the switch at a predetermined position is opened to disconnect part of the sub-coil, and only the required number of turns is retained.

[0050] The encoding can be pre-set and correspond to the number of turns one by one. Only a simple encoding control instruction needs to be sent to achieve accurate control of the number of turns. By controlling the encoding switch, fine adjustment of the number of turns of the coil can be achieved to meet the construction requirements of different electromagnetic parameter target bodies.

[0051] Of course, in combination with the programmable switch network, the connection mode (such as parallel connection, mixed connection or hybrid topology) between the coils can also be dynamically adjusted to construct target bodies of different scales and electromagnetic characteristics.

[0052] In order to facilitate manufacturing, the embodiment divides a square coil into four straight wires, programmable switches are arranged at the four vertices of the coil, and the coil is sequentially connected to other coils to form a two-dimensional programmable coil array.

[0053] The programmable switch network is essentially a matrix composed of controllable relays. By programming the on and off states of the switch, the electrical connection path between different coils can be recombined to achieve the construction of a complex target body.

[0054] In other embodiments, the coil can also be changed to other shapes such as a rectangle, a circle, etc. These are easily thought of by those skilled in the art and should be within the protection scope of the present application.

[0055] In some embodiments, a heat dissipation component is also included. Those skilled in the art can use existing heat dissipation components to dissipate heat from the programmable coil array.

[0056] Embodiment two

[0057] A geophysical electromagnetic target body simulation method includes the following steps:

[0058] According to the experimental requirements, the size and electromagnetic parameters of the target body are determined, and the connection mode and the number of turns of the coil that can meet the experimental requirements are calculated. The geophysical electromagnetic exploration instrument detects the eddy current generated by the target conductor (i.e. the programmable coil array in this paper) excited by the primary electromagnetic field, and then detects the secondary field. For the number of turns of the coil, a higher number of turns means a greater eddy current intensity and a higher secondary field intensity. For a coil target body of the same size, a larger number of turns makes it easier to be detected. For a coil with the same number of turns, a larger size means that its coupling with the primary field is enhanced, making it easier to be detected. Through experiments, the relationship between the detectability of the programmable coil array and the two parameters is obtained, and the inverse solving algorithm is obtained.

[0059] In actual use, the control parameters can be input into the control software, and the system automatically generates the topological structure of the corresponding programmable coil array and the number of turns of each coil, completing the design and construction of the target body.

[0060] Embodiment Three

[0061] A geophysical electromagnetic target body detection device, in addition to the simulation device of embodiment one, when the programmable coil array is used as a receiving coil, a dynamic impedance matching module is added. The module uses real-time impedance analysis to deal with the problem of different impedances brought by different connection modes and numbers of turns.

[0062] In this embodiment, when the coil array is used as a detected target, its equivalent impedance (including resistance R, capacitance C and inductance L) directly affects the energy coupling efficiency between the coil array and the detection instrument. The dynamic impedance matching technology refers to detecting the impedance of each sub-coil unit through a high-frequency vector network analysis chip after determining the connection mode of the programmable coil array and the number of turns of each coil. According to the impedance of each coil sub-unit, the resistance R and capacitance C of the components in the impedance matching network are adjusted to match the equivalent impedance of the target coil with the working frequency of the detection instrument, maximizing the signal transmission efficiency and the secondary field response.

[0063] The adjustment of the circuit characteristics of the impedance matching network is realized through a variable capacitance array and a digital potentiometer. A variable capacitor is a capacitor whose capacitance value can be adjusted by an external signal. A variable capacitor array combines multiple variable capacitors together to provide a larger adjustment range and flexibility. A digital potentiometer is an electronic component that controls the resistance value through a digital signal. Essentially, it is a programmable resistor.

[0064] By high-frequency vector network analysis chip and phase-locked amplification technology, the complex impedance of each sub-coil unit is dynamically detected, and the optimal matching element is calculated. Through a switching network, compensation elements such as variable capacitor arrays and digital potentiometers are dynamically accessed to change the capacitance and resistance parameters in the impedance matching network, and the impedance matching of the receiving loop is optimized in real time. Reduce system reflection loss, improve system efficiency and signal integrity.

[0065] It also includes a signal receiving circuit for eliminating or suppressing noise and interference in the measured magnetic field.

[0066] In this embodiment, the signal receiving circuit includes a filter circuit, a power frequency notch circuit, a programmable amplifier circuit, and an analog-to-digital converter connected in sequence, all of which can use existing circuits.

[0067] For example, the filter circuit can use a fourth-order Butterworth low-pass filter to filter out high-frequency interference. The power frequency notch circuit can use a double-T notch circuit to suppress power frequency and harmonic interference. The programmable amplifier circuit and the analog-to-digital converter can use a 24-bit Sigma-Delta ADC to convert the analog signal into a digital signal that the control module can process, making subsequent processing easier.

[0068] Embodiment four

[0069] A geophysical electromagnetic target detection method, as shown in Figure 3 includes the following steps:

[0070] Determine the size and electromagnetic parameters of the target body according to the experimental requirements, determine the connection method between the coils and the number of turns of the coils that can meet the experimental requirements, and complete the design and construction of the target body;

[0071] After determining the connection method of the programmable coil array and the number of turns of each coil, perform dynamic impedance matching to adjust the impedance of the device receiving channel to the best.

[0072] In the specific process, the connection method and the number of turns can be determined first. After determining the connection method, disconnect the coil units that do not participate in the connection. If a loop cannot be formed, it will not be detected. After determining the connection method and the number of turns of the coil units, the impedance can be measured, and the impedance matching can be performed by adjusting the variable capacitor and the digital potentiometer.

[0073] Turn on the receiving mode of the programmable coil array, calibrate the receiving control parameters of the programmable coil array by exciting a standard test signal, and collect background electromagnetic noise (including power frequency interference, environmental noise, etc.) for subsequent accurate calculation of primary field signals.

[0074] Lay out the electromagnetic detection equipment and perform high-precision detection according to the predetermined experimental scheme. At the same time, the programmable coil array is adjusted to the receiving mode to real-time perceive the primary field signal excited by the electromagnetic detection equipment.

[0075] According to the inversion imaging result and the programmable coil topology structure comparison, and the programmable coil array real-time sensing primary field data interpretation, the detection effect is evaluated;

[0076] According to the inversion imaging and the programmable coil topology structure comparison result, the programmable coil size and electromagnetic parameters in the next experiment are determined, if the inversion imaging result meets the requirement, the programmable coil size can be reduced for further experiment, otherwise.

[0077] The above steps are repeated until the inversion imaging result is blurred, according to the comparison of multiple inversion imaging results and coil sensing primary field data, the detection accuracy of the electromagnetic detection theory method and equipment is evaluated, and the error source is determined.

[0078] In the above process, through experiments and experience, the mapping relationship between the coil array size and the geophysical electromagnetic detection accuracy is found, the relationship between the coil size and the electromagnetic parameters corresponding to the actual detection accuracy when the inversion imaging is blurred is found, that is, the detection accuracy of the electromagnetic detection theory method and equipment can be evaluated; the coil unit in the programmable coil array can sense the primary field excited by the detection instrument in real time, by comparing the measured primary field and the theoretical model (through forward simulation, the ideal value of the primary field excited by the detection instrument at the target body can be obtained, but the geometric error of the transmitting coil, the current fluctuation and the interference of the adjacent conductor in the actual environment will cause the distortion of the primary field, and then affect the secondary field inversion accuracy), the primary field distortion correction coefficient is constructed, the reason of the primary field distortion is found, and the electromagnetic transmitter parameters are corrected. The embodiment provides a basis for the optimization of the electromagnetic detection theory method and equipment.

[0079] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can adopt a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer usable storage media (including but not limited to magnetic disk storage, optical storage, etc.) containing computer usable program code. CD - ROM , optical storage, etc.).

[0080] The computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks. Figure 1 one or more flow or blocks Figure 1 one or more flow or blocks

[0081] These computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture including instructions which implement the function specified in the flowchart block or blocks. Figure 1 one or more flow or blocks Figure 1 one or more flow or blocks

[0082] The computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks. Figure 1 one or more flow or blocks Figure 1 one or more flow or blocks

[0083] The above description is only preferred embodiment of the present application but not for limiting the present application. The present application can have various modifications and changes for those skilled in the art. Any modifications, equivalent replacements, improvements, etc. made by those skilled in the art within the spirit and principle of the present application without creative efforts should be included in the protection scope of the present application.

Claims

1. A geophysical electromagnetic target detection apparatus, characterized by, The simulation device comprises a geophysical electromagnetic target body simulation device, a dynamic impedance matching module and a signal receiving circuit, wherein: The geophysical electromagnetic target body simulation device comprises a programmable coil array and a programmable switch network, wherein: The programmable coil array comprises a plurality of coil units arranged in a matrix, each coil unit comprising a plurality of sub-coil units, and a control switch is arranged between adjacent sub-coil units, and the length of the coil path / number of turns of each coil unit in use is determined by changing the state of the control switch; The programmable switch network comprises a plurality of programmable switches, a plurality of programmable switches are arranged at intervals on each coil unit, and adjacent coil units are connected through at least one programmable switch, and the number of coil units connected and the connection path formed by each coil unit are changed by controlling the on-off state of each programmable switch; The connection mode of the programmable coil array and the number of turns of each coil unit are changed by the state of each control switch and the programmable switch network to construct geophysical electromagnetic target bodies of different scales and different electromagnetic parameters; The geophysical electromagnetic target body simulation device controls the programmable switch network and each control switch according to requirements to construct a target body of a predetermined scale and electromagnetic parameter, and receives a primary field excited by an electromagnetic detection device, and the programmable coil array generates a corresponding secondary field by induction; The dynamic impedance matching module detects the complex impedance of each sub-coil unit when the programmable coil array is used as a receiving coil, calculates the optimal matching, and performs dynamic compensation; The signal receiving circuit is used for processing the received signal to eliminate or suppress noise and interference in the measured magnetic field.

2. A geophysical electromagnetic target detection apparatus as claimed in claim 1, characterized in that Each square coil is the same size and is arranged in a matrix, and each square coil has a programmable switch at each of its four corners.

3. A geophysical electromagnetic target detection apparatus as claimed in claim 1, characterized in that Each sub-coil unit has metal contacts and a control switch at both ends, adjacent sub-coil units are connected through the metal contacts and the control switch, and the control switch is a programmable switch.

4. A geophysical electromagnetic target detection apparatus as claimed in claim 1, characterized in that, Each sub-coil unit is connected in series through each control switch.

5. A geophysical electromagnetic target detection apparatus as claimed in claim 1, wherein, The control switch has a separate ID and a corresponding independent code bit, and the on-off state of the corresponding control switch is controlled by pre-setting the code to determine the length of the coil path / number of turns of each coil unit in use.

6. A geophysical electromagnetic target detection apparatus as claimed in claim 1, wherein, The signal receiving circuit comprises a filter circuit, a power frequency notch circuit, a programmable amplification circuit and an analog-to-digital converter connected in sequence.

7. A geophysical electromagnetic target detection apparatus as claimed in claim 6, characterized in that The filter circuit is a fourth-order Butterworth low-pass filter, the power frequency notch circuit is a double-T notch circuit, and the programmable amplification circuit and the analog-to-digital converter are multi-bit Σ-Δ type ADCs.

8. A method of geophysical electromagnetic target detection based on the device of any one of claims 1-7, characterized in that, The method comprises the following steps: Step (1) determining the scale and electromagnetic parameters of the target body to be constructed according to requirements, calculating the connection mode between each coil in the corresponding programmable coil array and the number of turns of each coil, controlling each control switch and the programmable switch network, forming a two-dimensional coil array, and completing the construction of the target body; Step (2) after determining the connection mode of the programmable coil array and the number of turns of each coil, the dynamic impedance matching module performs dynamic impedance matching to adjust the receiving channel impedance of the device to the best. Step (3) starts the receiving mode of the programmable coil array, calibrates the receiving control parameters of the programmable coil array by exciting a standard test signal, and acquires background electromagnetic noise; Step (4) deploys the electromagnetic detection equipment; Step (5) performs detection, adjusts the programmable coil array to the receiving mode, and real-time senses the primary field signal excited by the electromagnetic detection equipment; Step (6) compares the inversion imaging result with the current topological structure of the programmable coil array, interprets the primary field data sensed by the programmable coil array, and evaluates the detection effect of this time; Step (7) determines the size and electromagnetic parameters of the target body in the next experiment according to the comparison result of the inversion imaging and the programmable coil array; Step (8) repeats steps (1)-(7) until the inversion imaging result meets the detection requirements, and comprehensively evaluates the detection accuracy of the electromagnetic detection equipment according to the comparison of multiple inversion imaging results and the primary field data sensed by the programmable coil array.

9. A geophysical electromagnetic target detection method as claimed in claim 8, characterized in that, The process of determining the size and electromagnetic parameters of the target body in the next experiment according to the comparison result of the inversion imaging and the programmable coil array includes: determining the mapping relationship between the coil array size and the geophysical electromagnetic detection accuracy through experiments, and determining the relationship between the coil size and the electromagnetic parameters corresponding to the actual detection accuracy when the inversion imaging is blurred; The coil units in the programmable coil array real-time sense the primary field excited by the electromagnetic detection equipment, the primary field distortion correction coefficient is constructed by comparing the measured primary field with the theoretical model, the cause of the primary field distortion is found out, and the electromagnetic transmitter parameters are corrected.

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