An electromagnetic induction detection method and system

Abstract

This invention discloses an electromagnetic induction detection method and system. The method includes: Step S1, pre-setting multiple transmitting wires and corresponding dual-channel receiving wires in a target detection area. The dual-channel receiving wires are orthogonally distributed and connected to a signal receiving device. The transmitting wires are connected to a transmitting power supply device, and the primary magnetic flux of the loop cavity formed by each transmitting wire and the corresponding dual-channel receiving wire is zero; Step S2, pre-setting the positions of multiple signal detection points along the length direction of each transmitting wire; Step S3, sequentially moving the dual-channel receiving wires according to the positions of the multiple detection points on the same transmitting wire to obtain measurement data of the multiple detection points in the target detection area on each transmitting wire; Step S4, determining the dielectric structure within the target detection area based on the measurement data of the multiple detection points in the target detection area on each transmitting wire. This invention aims to avoid limiting the use of electromagnetic induction detection methods to confined spaces.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic detection in nondestructive testing, and more particularly to an electromagnetic induction detection method and system. Background Technology

[0002] Currently, geological exploration, mineral detection, and mechanical inspection often utilize the principle of electromagnetic induction for detection or testing. In practical engineering, near-source electromagnetic induction measurement is particularly common. However, this method has its drawbacks: due to the proximity of the receiving sensor or probe to the transmitter, a strong mutual electromagnetic inductance exists between the transmitter and the receiving sensor. This mutual inductance signal acts as strong interference, superimposed on the response signal of the measured object, leading to a reduction in the signal-to-noise ratio of the effective signal. Therefore, if the mutual inductance effect in the receiving sensor can be suppressed or eliminated, the detection accuracy or resolution of near-source measurements can be effectively improved.

[0003] Existing invention patents, CN102565862A and CN103837899A, disclose a method and device for measuring the gradient of transient electromagnetic response signals and a transient electromagnetic measurement device, respectively. Both improve reception efficiency by reducing the electromagnetic induction of the transmitting coil on the receiving coil or sensor through the spatial distribution characteristics of the electromagnetic field of the "transmitting loop". However, this setup requires precise fixing of the relative positions of the transmitting or receiving coils, and the transceiver device cannot be too large, making it difficult to install and too heavy for field operations. Furthermore, the limited area of ​​the transmitting and receiving coils severely restricts the ability to increase the transmitting magnetic moment and thus improve electromagnetic detection capabilities by increasing the area of ​​the transmitting coil. Therefore, there is an urgent need to propose a new electromagnetic induction detection method to improve detection accuracy. Summary of the Invention

[0004] The main objective of this invention is to provide an electromagnetic induction detection method and system, which aims to solve the technical problems of low accuracy and limited detection in existing electromagnetic induction detection methods.

[0005] To achieve the above objectives, the present invention provides an electromagnetic induction detection method, the method comprising the following steps:

[0006] Step S1: Multiple transmitting wires and corresponding dual-channel receiving wires are preset in the target detection area. The dual-channel receiving wires are orthogonally distributed and connected to the signal receiving device. The transmitting wires are connected to the transmitting power supply device. The primary magnetic flux of each transmitting wire in the loop cavity formed by the corresponding dual-channel receiving wire is zero.

[0007] Step S2: Preset the positions of multiple signal detection points along the length of each transmitting wire;

[0008] Step S3: Move the dual-channel receiving wire sequentially according to the positions of multiple detection points on the same transmitting wire to obtain the measurement data of the target detection area at multiple detection points on each transmitting wire;

[0009] Step S4: Determine the medium structure within the target detection area based on the measurement data of multiple detection points on each transmitting lead in the target detection area.

[0010] Optionally, the two ends of the transmitting wire are grounded or connected in a loop.

[0011] Optionally, the two ends of the transmitting wire can be switched between being grounded and being connected to a loop.

[0012] Optionally, the detection points on the same transmitting lead are distributed at equal intervals.

[0013] Optionally, the current transmitted by the transmitting power supply device is any one of a fixed-frequency alternating current, a programmed combination of multi-frequency alternating current, and a time-varying step current.

[0014] Optionally, the dual-channel receiving wires are arranged in corresponding mutually orthogonal magnetic field measuring sensors, wherein the magnetic field measuring sensors are one of coil sensors, magnetic rod sensors, magnetoresistive sensors, and Hall sensors.

[0015] Optionally, when the magnetic field measuring sensor is a coil sensor, each transmitting wire passes through the loop cavity formed by the dual-channel receiving wire.

[0016] Optionally, a vertical guide tube is fitted over a portion of the loop cavity formed by the corresponding dual-channel receiving wires through which each transmitting wire passes.

[0017] Optionally, the step of determining the dielectric structure within the target detection area based on measurement data from multiple detection points on each transmitting lead includes:

[0018] Step S41: Preset multiple parameters of the initial medium structure;

[0019] Step S42: Based on multiple parameters of the preset initial medium structure, Maxwell's equations, and the positions of each detection point, obtain the theoretical numerical simulation signal within the target detection area;

[0020] Step S43: Compare the theoretical numerical simulation signal with the actual measurement data of each detection point on the same transmitting lead;

[0021] In step S44, if the comparison result does not meet the preset requirements, the corresponding parameters of the preset medium structure are adjusted according to the comparison result, and the updated parameters are used to continue to execute step S42 until the comparison result meets the preset requirements.

[0022] In addition, to achieve the above objectives, the present invention also provides an electromagnetic induction detection system, the system comprising a transmitting power supply device, a signal receiving device, multiple transmitting wires connected to the transmitting power supply device, and dual-channel receiving wires connected to the signal receiving device, wherein the dual-channel receiving wires are orthogonally distributed and the primary magnetic flux of each transmitting wire in the loop cavity formed by the corresponding dual-channel receiving wire is zero.

[0023] Beneficial effects:

[0024] (1) This method arranges the dual-channel receiving wires in an orthogonal distribution so that the primary magnetic flux of each transmitting wire in the loop cavity formed by the corresponding dual-channel receiving wire is zero. The dual-channel receiving wires are directionally moved along the detection point to detect the possible medium structure in the target detection area. In the case of the existence of the medium structure, the electromagnetic field excitation response of the medium structure around the transmitting wire due to the alternating current in the transmitting wire can still be received by the dual-channel receiving wire, thereby effectively avoiding the influence of the transmitting wire on the primary field of the dual-channel receiving wire, obtaining high data accuracy, and thus improving the accuracy of electromagnetic induction detection data.

[0025] (2) This method can be used in complex ground and confined spaces such as boreholes and tunnels. The sensor near-source measurement suppresses the primary field signal, resulting in a high signal-to-noise ratio and strong detection capability. It also has high operating efficiency and directional detection function.

[0026] (3) This measurement method is not limited to frequency or time and can be used for detection, which improves the versatility of electromagnetic exploration.

[0027] (4) This method also effectively solves the problem of orientation of underground abnormal targets.

[0028] (5) In addition to conventional geological and mineral resource exploration, this method is also suitable for fine detection of underground obstacles in cities, such as underground metal pipelines, abandoned pile foundations, pile caps and metal structural components, groundwater and pollution environment detection, etc.

[0029] (6) The entire measurement system is simple and convenient, and the on-site construction operation is convenient, which is conducive to its promotion. Attached Figure Description

[0030] Figure 1 This is a flowchart illustrating the first embodiment of the electromagnetic induction detection method of the present invention;

[0031] Figure 2 This is a schematic diagram of the structure of a first embodiment of an electromagnetic induction detection system according to the present invention;

[0032] Figure 3 for Figure 2The diagram shows a rendering of the first embodiment where the magnetic flux of the dual-channel receiving wire is zero.

[0033] Figure 4 for Figure 2 The diagram shows a rendering of a second embodiment where the magnetic flux of the dual-channel receiving wire is zero.

[0034] Figure 5 This is a schematic diagram of the structure of a second embodiment of an electromagnetic induction detection system according to the present invention;

[0035] Figure 6 This is a schematic diagram of the structure of a third embodiment of an electromagnetic induction detection system of the present invention.

[0036] Figure 7 This is a diagram illustrating the effect of using the electromagnetic field response signals of the mutually orthogonal sensors of this invention to determine the target direction.

[0037] Figure 8 This is a diagram illustrating the effect of determining the target direction using the electromagnetic field response signal obtained from the orthogonal gradient measurement of this invention.

[0038] Figure 9 This is a schematic diagram of the fourth embodiment of an electromagnetic induction detection system of the present invention.

[0039] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0040] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0041] See Figures 2 to 9 The present invention provides an electromagnetic induction detection system, the system comprising a transmitting power supply device 3, a signal receiving device 2, multiple transmitting wires 31 connected to the transmitting power supply device 3, and a dual-channel receiving wire connected to the signal receiving device 2.

[0042] Specifically, the signal receiving device 2 is connected to a mutually orthogonal magnetic field measuring sensor, and the magnetic field measuring sensor is internally equipped with mutually orthogonal dual-channel receiving wires; and the transmitting wire 31 is also connected to the transmitting power supply device 2 through a corresponding auxiliary power supply wire. The auxiliary power supply wire provides a loop for the transmitting wire 31. The auxiliary power supply wire forming the loop is far away from the transmitting wire 31 to minimize the impact of the primary field it generates on the receiving sensor. At the same time, the position of the transmitting wire 31 can be adjusted according to the actual detection needs.

[0043] In practical applications, an alternating current transmitting power supply device 2 is used to supply alternating current through the transmitting conductor 31, thereby forming an alternating primary electromagnetic field covering the measuring line around the transmitting conductor 31. The magnetic flux of the primary electromagnetic field in the dual-channel receiving conductor is zero. Then, the measuring sensor can capture the induced secondary electromagnetic field radiated by the dielectric structure around the transmitting conductor 31 due to electromagnetic induction through the dual-channel receiving conductor. The magnetic field measuring sensor is moved point by point along the length of the transmitting conductor 31 to measure the data. The electrical structural parameters around the measuring line are interpreted based on the magnitude, direction or frequency characteristics of the orthogonally distributed secondary electromagnetic field measured point by point.

[0044] Furthermore, to better illustrate the deployment principle of an electromagnetic induction detection system, the following describes the specific steps of the electromagnetic induction detection method, such as... Figure 1 The diagram shown is a flowchart of an embodiment of an electromagnetic induction detection method, which specifically includes:

[0045] Step S1: Multiple transmitting wires and corresponding dual-channel receiving wires are preset in the target detection area. The dual-channel receiving wires are orthogonally distributed and connected to the signal receiving device. The transmitting wires are connected to the transmitting power supply device. The primary magnetic flux of each transmitting wire in the loop cavity formed by the corresponding dual-channel receiving wire is zero.

[0046] Specifically, in practical applications, the magnetic field measurement sensor internally has mutually orthogonal dual-channel receiving wires. The magnetic field measurement sensor can be selected from one of the following: a coil sensor, a magnetic rod sensor, a magnetoresistive sensor, and a Hall effect sensor. For example... Figure 2 As shown, the magnetic field measuring sensor is a coil sensor, and each transmitting wire 31 passes through the loop cavity formed by the dual-channel receiving wire. Preferably, a vertical guide tube 4 can also be provided on the transmitting wire 31 to ensure the straightness of the transmitting wire 31 where the dual-channel receiving wire is located, so that the primary magnetic flux of each transmitting wire in the loop cavity formed by the corresponding dual-channel receiving wire is zero.

[0047] Furthermore, the two ends of the transmitting wire 31 are either grounded or connected in a loop. Specifically, as shown... Figure 2 and Figure 5 As shown, the transmitting wire 31 is grounded at both ends; as Figure 6 As shown, the two ends of the transmitting wire 31 are connected in a loop; preferably, two selector switches are also provided in the connection loop to facilitate the selection of grounding or connection loop of the transmitting wire 31.

[0048] Step S2: Preset the positions of multiple signal detection points along the length of each transmitting wire; specifically, as follows... Figure 9As shown, the transmitting wires are parallel and spaced apart, and the positions of the detection points can be distributed along the length of the transmitting wires. Preferably, the detection points on the same transmitting wire are distributed at equal intervals.

[0049] Step S3: Move the dual-channel receiving wire sequentially according to the positions of multiple detection points on the same transmitting wire to obtain measurement data of multiple detection points of the target detection area on each transmitting wire; specifically, the final measurement data of multiple detection points is the data obtained by the target detection area under the electromagnetic induction influence of the internal medium structure.

[0050] Specifically, such as Figure 3 As shown, when a rectangular receiving coil is used as the measuring sensor for a dual-channel receiving conductor, and the alternating current supplied to the transmitting conductor flows from top to bottom, according to the right-hand rule, the magnetic field lines on the left and right sides of the space with the transmitting conductor as the axis of symmetry are perfectly symmetrical. Therefore, when the dual-channel receiving conductor is positioned symmetrically about the transmitting conductor, the magnetic field lines entering and exiting the receiving coil are exactly zero. This also applies when the current in the transmitting conductor flows in the opposite direction or when alternating current is supplied. Therefore, based on the above principle, as long as the dual-channel receiving conductor is in a symmetrical position about the transmitting conductor (not necessarily attached to it), regardless of the change in the alternating current on the transmitting conductor, the magnetic flux through the dual-channel receiving conductor is zero. No induced electromotive force is generated in the dual-channel receiving conductor due to the change in current on the transmitting conductor, thus effectively avoiding the mutual inductance effect caused by the dual-channel receiving conductor being close to the transmitting conductor. In other words, the dual-channel receiving conductor avoids the interference caused by the primary field of the transmitting conductor. The electromagnetic field excitation response from the surrounding medium structure due to the alternating current in the transmitting conductor, which is the secondary field, can still be received by the dual-channel receiving conductor. Similarly, Figure 4 The reason for the magnetic rod sensor's reception shown is also related to... Figure 3 The rectangular receiving coils shown are basically the same, and the coils inside the magnetic rod sensor are also orthogonally wound.

[0051] Furthermore, such as Figure 5 As shown, the dual-channel receiving wire is composed of a first-channel coil 21 and a second-channel coil 22 that are orthogonal to each other. The first-channel coil 21 is formed by connecting left and right wires in series, while the second-channel coil 22 is formed by connecting front and rear wires in series. The left-right connected first-channel coil 21 and the front-rear connected second-channel coil 22 are then assembled into a cubic structure. The transmitting wire 31 overlaps with and passes through the central axis of the cube, thus ensuring that the magnetic flux of the primary field emitted by the transmitting wire 31 within the cubic structure is zero. Similarly, as... Figure 6As shown, the selected first channel coil 21 and second channel coil 22 are both rectangular wire frames that are orthogonal to each other, and the transmitting wire 31 overlaps with and passes through the central axis of the dual-channel coil.

[0052] Furthermore, the current transmitted by the transmitting power supply device is any one of a fixed-frequency alternating current, a programmed combination of multi-frequency alternating current, and a time-varying step current. Specifically, if a fixed-frequency alternating current is supplied to the transmitting wire 31, a fixed-frequency electromagnetic field is formed around the transmitting wire 31; if a programmed combination of multi-frequency alternating current is supplied to the transmitting wire 31, a multi-frequency electromagnetic field is formed around it; and if a time-varying step current is supplied to the transmitting wire 31, a transient electromagnetic field is formed around it. The corresponding electromagnetic response signals are then received by a measuring sensor, facilitating subsequent analysis of the electrical structure of the probe medium based on the response amplitude and phase change characteristics of electromagnetic signals at different frequencies. Generally, the electromagnetic field response signals of mutually orthogonal sensors can undergo vector synthesis and other calculations. The magnitude, direction, and frequency characteristics of the calculation results are used to determine the basic orientation and electrical characteristics of the concealed target.

[0053] Step S4: Determine the medium structure within the target detection area based on the measurement data of multiple detection points on each transmitting lead in the target detection area.

[0054] Specifically, step S4 includes:

[0055] Step S41: Preset multiple parameters of the initial medium structure;

[0056] Step S42: Based on multiple parameters of the preset initial medium structure, Maxwell's equations, and the positions of each detection point, obtain the theoretical numerical simulation signal within the target detection area; specifically, combining the geological and geophysical conditions that can be obtained in the area to be detected, set the geometric parameters of the initial medium structure used for inversion and the corresponding physical property parameters such as resistivity, dielectric constant, polarizability, and magnetic permeability, and combine the mathematical equations (Maxwell's equations) and the operating mode of this detection method, calculate the numerical simulation signal that the receiving measurement point, measurement line, or measurement area should obtain through the numerical simulation method.

[0057] Step S43: Compare the theoretical numerical simulation signal with the actual measurement data of each detection point on the same transmitting lead;

[0058] In step S44, if the comparison result does not meet the preset requirements, the corresponding parameters of the preset medium structure are adjusted according to the comparison result, and the updated parameters are used to continue to execute step S42 until the comparison result meets the preset requirements.

[0059] Specifically, the target direction is determined based on the electromagnetic field response signals of mutually orthogonal sensors, such as... Figure 7As shown, 5 corresponds to the primary magnetic field line generated by the transmitting wire 31, and 6 corresponds to the secondary magnetic field line generated by the target medium structure. The power supply direction of the transmitting wire 31 is perpendicular to the paper and inwards. The measuring sensor is a coil, with two orthogonal coils located as shown in the figure. The first channel coil 21 is placed vertically, and the second channel coil 22 is placed horizontally, with both coil planes perpendicular to the paper. The magnetic flux of the primary field generated by the alternating current supplied by the transmitting wire 31 in both receiving coils is zero. When the concealed target medium structure 1 is located on the left and right sides of the transmitting wire 31, the optimal receiving coil for the secondary field generated by its excitation is the horizontally placed second channel coil 22, and the vertically placed second channel coil 22 is placed horizontally. The first channel coil 21 is placed in the most unfavorable position; when the concealed target medium structure 2 is located above and below the transmitting wire 31, the optimal coupling positions of the two orthogonal receiving coils are interchanged; therefore, the orientation of the concealed electrical structure can be roughly determined based on the intensity and magnitude variation characteristics of the secondary field signals received by the two orthogonal receiving antennas; taking the normal direction of each receiving coil as the signal vector direction, through the vector synthesis of the signals received by the two receiving coils, and under ideal conditions, with the power supply transmitting wire 31 as a reference, the direction of the synthesized vector is exactly perpendicular to the direction of the target, and thus the electromagnetic field response signal of the mutually orthogonal sensors can be determined to judge the target direction through the above analysis.

[0060] And, determining the target direction based on the electromagnetic field response signal from orthogonal gradient measurements, such as... Figure 8 As shown, the transmitting wire 31 is powered perpendicular to the paper and points inwards. The receiving sensor is a coil, perpendicular to the paper. Horizontal or vertical receiving coils are paired, positioned as shown. The primary field generated by the alternating current supplied to the transmitting wire 31 has zero magnetic flux in all four paired receiving coils. When a concealed, well-conducting target is located at a certain position on the transmitting wire 31, the secondary field it generates still has its optimal and least favorable coupling orientations. Furthermore, the coil closer to the concealed target will receive a stronger induced signal. The signals received by the two coils in this coupling direction are subtracted, and the exact orientation of the concealed target can be determined based on the sign of the subtraction result. Therefore, the effectiveness of determining the orientation of a concealed target through vector synthesis of signals received by gradient receiving coils in orthogonal directions still exists. Furthermore, gradient measurement can clearly distinguish left, right, up, and down.

[0061] Furthermore, as described above, the orientation of the target medium structure can be determined based on orthogonal quadratic field measurement and gradient measurement. Then, based on the comparison between the numerical simulation signal and the corresponding measured signals at the measured points, lines, and areas, the initially set geometric or physical property parameters of the medium structure are adjusted according to the magnitude and variation characteristics of the differences. The numerical simulation method is then used again to calculate the numerical signals obtained from the receiving measurement points, lines, or areas, and the updated signals are compared with the measured numerical signals. The geometric or physical parameters of the newly set medium structure are adjusted in real time according to the magnitude and variation characteristics of the differences. This iterative calculation continues until the difference between the numerical simulation signal and the measured numerical signal is small enough to meet the user's settings. Therefore, the geometric and physical property parameters of the medium structure within the target area are the final updated parameters that most closely approximate the actual results. Moreover, the above measurement method can be used in unrestricted spaces, thereby improving measurement accuracy and efficiency, and enhancing the versatility of electromagnetic induction measurement.

[0062] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or system that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or system. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or system that includes that element.

[0063] The sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0064] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. Any equivalent structural or procedural transformations made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. An electromagnetic induction detection method characterized by, The method comprises the following steps: Step S1, a plurality of fixed transmission wires and corresponding double-channel receiving wires are preset in a target detection area, the double-channel receiving wires are orthogonally distributed and connected with a signal receiving device, the fixed transmission wires are connected with a transmission power supply device, the primary field magnetic flux of each fixed transmission wire in the loop cavity formed by the corresponding double-channel receiving wire is zero, the signal receiving device is connected with the double-channel receiving wire, the two ends of the fixed transmission wire are arranged in a grounding mode or a loop connection mode, and the two ends of the fixed transmission wire are switchable between the grounding mode and the loop connection mode; Step S2, positions of a plurality of signal detection points along the length direction of each fixed transmission wire are preset, and each detection point on the same fixed transmission wire is distributed at equal intervals; Step S3, the double-channel receiving wire is moved according to the positions of the plurality of detection points on the same fixed transmission wire in sequence, measurement data of the plurality of detection points of the target detection area on each fixed transmission wire are obtained, and a vertical guide pipe is arranged on the part of the region of the loop cavity formed by the corresponding double-channel receiving wire through which each fixed transmission wire passes; Step S4, a medium structure in the target detection area is determined according to the measurement data of the plurality of detection points of the target detection area on each fixed transmission wire, and specifically, step S4 comprises: Step S41, a plurality of parameters of an initial medium structure are preset; Step S42, a theoretical numerical simulation signal in the target detection area is obtained according to the plurality of parameters of the preset initial medium structure, Maxwell equations and the positions of the detection points; Step S43, the theoretical numerical simulation signal is compared with the measurement data of each detection point on the same transmission wire; Step S44, if the comparison result does not meet a preset requirement, the corresponding parameter of the preset medium structure is adjusted according to the comparison result, and the updated corresponding parameter is used to continue step S42 until the comparison result meets the preset requirement.

2. The electromagnetic induction detection method according to claim 1, characterized in that, The current transmitted by the transmission power supply device is any one of a fixed-frequency alternating current, a programmed combined multi-frequency alternating current and a time-varying step current.

3. The electromagnetic induction detection method according to claim 1, characterized in that, The double-channel receiving wire is arranged in a corresponding mutual orthogonal magnetic field measurement sensor, and the magnetic field measurement sensor is one of a coil sensor, a magnetic rod sensor, a magnetic resistance sensor and a Hall sensor.

4. The electromagnetic induction detection method according to claim 3, characterized in that, When the magnetic field measurement sensor is a coil sensor, each transmission wire passes through the loop cavity formed by the double-channel receiving wire.

5. An electromagnetic induction detection system, characterized in that The system comprises a transmission power supply device, a signal receiving device, a plurality of fixed transmission wires connected with the transmission power supply device and a double-channel receiving wire connected with the signal receiving device, the double-channel receiving wire is orthogonally distributed, and the primary field magnetic flux of each fixed transmission wire in the loop cavity formed by the corresponding double-channel receiving wire is zero, The double-channel receiving wire is configured to move along the fixed transmission wire to a preset equal-interval signal detection point; The magnetic field measurement sensor connected with the signal receiving device is a coil sensor, a magnetic rod sensor, a magnetic resistance sensor or a Hall sensor.

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