A signal direction-based parallel pipeline identification method and system

Abstract

The application discloses a parallel pipeline identification method and system based on signal direction, and particularly relates to the technical field of electromagnetic measurement and identification, and is used for solving the problem of direction misinterpretation caused by inconsistent sensor posture and superimposed induction field in dense parallel laying sections; by injecting a pulsating current signal to the target pipeline, using a two-axis orthogonal magnetic field sensor to pick up the first direction component and the second direction component of each pipeline surface in any posture, mapping the positive and negative half cycle components into complex vectors and constructing a first complex vector trajectory and a second complex vector trajectory, calculating the closed area of the non-overlapping part of the two trajectories as the asymmetry, through the algebraic sum of the asymmetry of adjacent lines approaching to zero and the sum of the absolute values exceeding the preset complementary judgment threshold value, excluding the non-target pipelines showing numerical complementarity, and applying a preset threshold value to the asymmetry of the remaining pipelines to identify the target pipeline.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic quantity measurement and identification technology, and more specifically, to a parallel pipeline identification method and system based on signal direction. Background Technology

[0002] In the operation and maintenance of power cables and metal pipelines, it is often necessary to accurately identify a target pipeline from multiple parallel-laid pipelines. Existing technologies can use a signal injection and direction detection-based identification method. The working principle is as follows: a DC pulsating signal of a specific period is applied to one end of the target pipeline, causing the signal current to flow along the pipeline's metal sheath or conductor towards the distant grounding point, forming an electromagnetic response around the pipeline synchronized with the injected signal. Operators use current sensors with direction discrimination capabilities to inspect each pipeline along the pipeline group. By analyzing whether the direction of the current signal picked up by the sensor matches the injection reference direction, it is determined whether the currently tested pipeline is the target pipeline. When the direction of the signal picked up by the sensor matches the injection direction, it is determined to be the target pipeline; if the direction does not match or there is no signal response, it is determined to be a non-target pipeline.

[0003] However, in practical applications, in densely parallel sections, the injected current and induced current carried by multiple pipelines will superimpose in space to form a complex electromagnetic response. Due to the extremely small distance between each pipeline and the operation method of operators touching the sensor pipe by pipe with their hands, it is difficult to ensure that the sensor's sensitive axis is coupled and sensed in the exact same spatial orientation each time. The direction of the signal represented by the sensor output is affected by both the actual current direction in the pipeline and the coupling relationship between the superimposed electromagnetic response and the sensor's own orientation. This means that even without changing the actual current direction of the pipeline, the sensor may still output a signal direction indication opposite to the reference direction, causing distortion of the direction judgment result. This makes it difficult to guarantee the accuracy of the existing method in densely parallel working conditions, and it is easy to misjudge or miss the target pipeline. Summary of the Invention

[0004] To overcome the aforementioned deficiencies of the prior art, the present invention provides a parallel pipeline identification method and system based on signal direction to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A parallel pipeline identification method based on signal direction includes the following steps: S1: Inject a pulsating current signal with a preset period into one end of the target pipeline; S2: Select a reference point on the target pipeline and place a magnetic field sensor with two orthogonal sensing axes at the reference point; S3: For at least two pipelines in a parallel pipeline laying section, respectively, make the magnetic field sensor approach the surface of each pipeline in any posture to obtain the first direction component and the second direction component corresponding to each pipeline. S4: For each pipeline, map the first direction component and the second direction component to complex vectors on the complex plane, obtain the first complex vector trajectory during the positive half-cycle of the pulsating current signal and the second complex vector trajectory during the negative half-cycle, and calculate the closed area enclosed by the first complex vector trajectory and the reversed second complex vector trajectory on the complex plane as the asymmetry of the pipeline. S5: Select one of at least two pipelines as the pipeline to be tested, compare the asymmetry of the pipeline to be tested with the asymmetry of at least one adjacent pipeline, and if the values ​​are complementary, determine that the pipeline to be tested is a non-target pipeline and exclude it. S6: For pipelines that have not been excluded, if they do not meet the requirements of numerical complementarity and asymmetry less than a preset threshold, then the pipeline is determined to be the target pipeline.

[0006] Further, S1 includes: generating a square wave current signal with alternating positive and negative half cycles by a signal generator, setting the period of the square wave current signal to a preset period, connecting the output terminal of the signal generator to the metal sheath or conductor of the target pipeline, connecting the ground terminal of the signal generator to the ground, and injecting a square wave current signal with a preset period into one end of the target pipeline as a pulsating current signal.

[0007] Further, S2 includes: selecting a reference point in an exposed section of the target pipeline that is not covered by parallel laying, fixing a magnetic field sensor with a first sensitive axis and a second sensitive axis on the surface of the target pipeline at the reference point, wherein the first sensitive axis and the second sensitive axis are orthogonally arranged in a plane perpendicular to the pipeline axis, the first sensitive axis picks up a reference first direction component, and the second sensitive axis picks up a reference second direction component.

[0008] Further, S3 includes: identifying at least two pipelines within the parallel pipeline laying section, sequentially attaching a magnetic field sensor to the surface of each pipeline, wherein each time the magnetic field sensor contacts the pipeline surface in an arbitrary spatial orientation, the first direction component under the attachment orientation is picked up by the first sensitive axis, the second direction component under the attachment orientation is picked up by the second sensitive axis, and the first direction component and the second direction component corresponding to each pipeline are recorded.

[0009] Further, S4 includes: constructing a complex plane with the first directional component as the real part and the second directional component as the imaginary part; mapping the instantaneous values ​​of the first and second directional components of the pulsating current signal for each cycle to complex vectors on the complex plane; extracting all complex vectors during the positive half-cycle to form a first complex vector trajectory; extracting all complex vectors during the negative half-cycle to form a second complex vector trajectory; reversing the direction of the second complex vector trajectory to obtain the reversed second complex vector trajectory; calculating the closed area occupied by the non-overlapping parts of the region enclosed by the first complex vector trajectory and the region enclosed by the reversed second complex vector trajectory on the complex plane; and using the closed area as the asymmetry of the pipeline.

[0010] Further, calculating the closed area occupied by the non-overlapping portions of the region enclosed by the first complex vector trajectory and the region enclosed by the reversed second complex vector trajectory on the complex plane includes: connecting the beginning and end of the first complex vector trajectory with straight line segments to form a first closed curve, connecting the beginning and end of the reversed second complex vector trajectory with straight line segments to form a second closed curve, calculating the difference between the union area and the intersection area of ​​the region enclosed by the first closed curve and the region enclosed by the second closed curve, and using the difference as the closed area.

[0011] Furthermore, S5 includes: selecting any one of the pipelines whose asymmetry calculation has been completed as the pipeline to be tested; comparing the asymmetry of the pipeline to be tested with the asymmetry of at least one adjacent pipeline pairwise; if the asymmetry of the pipeline to be tested and the asymmetry of the adjacent pipelines show a zero-sum trend and opposite polarities, then the pipeline to be tested is determined to be a non-target pipeline and is excluded from the subsequent determination process.

[0012] Furthermore, the asymmetry of the pipeline under test is compared with the asymmetry of at least one adjacent pipeline, including: obtaining the algebraic sum of the asymmetry of the pipeline under test and the asymmetry of the adjacent pipeline; if the algebraic sum approaches zero and the sum of the absolute values ​​of the asymmetry of the pipeline under test and the asymmetry of the adjacent pipeline exceeds the preset complementary judgment threshold, then it is determined that there is a trend of one increasing while the other decreases and the polarities are opposite.

[0013] Furthermore, S6 includes: sequentially checking all remaining pipelines after elimination; if the adjacent pipelines of a certain pipeline in the remaining pipelines have been eliminated or the asymmetry between the pipeline and the remaining adjacent pipelines does not show a zero-sum trend and the polarities are opposite, and the asymmetry of the pipeline is less than a preset threshold, then the corresponding pipeline is determined to be the target pipeline.

[0014] On the other hand, the present invention provides a parallel pipeline identification system based on signal direction, comprising the following modules: The pulsating signal injection module is used to inject a pulsating current signal with a preset period into one end of the target pipeline. The reference point sensing arrangement module is used to select a reference point on the target pipeline and arrange a magnetic field sensor with two orthogonal sensing axes at the reference point. The dual-axis component acquisition module is used to obtain the first and second direction components of each pipeline by having a magnetic field sensor approach the surface of each pipeline in any orientation within a parallel pipeline laying section. The asymmetry calculation module is used to map the first direction component and the second direction component into complex vectors on the complex plane for each pipeline, obtain the first complex vector trajectory during the positive half-cycle of the pulsating current signal and the second complex vector trajectory during the negative half-cycle, and calculate the closed area enclosed by the first complex vector trajectory and the reversed second complex vector trajectory on the complex plane as the asymmetry of the pipeline. The adjacent line comparison and exclusion module is used to select one of at least two pipelines as the pipeline to be tested, compare the asymmetry of the pipeline to be tested with the asymmetry of at least one adjacent pipeline, and if the values ​​are complementary, the pipeline to be tested is determined to be a non-target pipeline and is excluded. The target pipeline determination module is used to determine if a pipeline that has not been excluded is a target pipeline if it does not meet the requirements of numerical complementarity and asymmetry less than a preset threshold.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The first and second directional components of the pipeline surface are obtained by a dual-axis orthogonal magnetic field sensor. The magnetic field response between the positive and negative half-cycles is constructed into the first and second complex vector trajectories on the complex plane by complex vector mapping. The non-overlapping closed area of ​​the region enclosed by the two trajectories is used as the asymmetry of the pipeline, which directly reflects the consistency of the polarization state of the pipeline response under pulsating signal excitation. When the pipeline is the target pipeline for direct signal injection, the magnetic field response of the positive and negative half-cycles is highly symmetrical and the closed area is close to zero. When the pipeline is a non-target pipeline affected by inductive coupling, the polarization ellipticization of the synthetic magnetic field leads to a significant increase in the closed area. Using the closed area as the asymmetry eliminates the need to rely on the specific spatial orientation of the sensor on each pipeline, and also eliminates the need for precise alignment or recording of the sensor's sensitive axis direction, thus eliminating the measurement deviation introduced by inconsistent handheld operation posture.

[0016] 2. The asymmetry of each pipeline in the parallel laying section is compared pairwise between adjacent pipelines. Utilizing the reciprocal complementarity of the inductive coupling between parallel pipelines, non-target pipelines with numerical complementarity are identified and excluded when the algebraic sum of the asymmetry approaches zero and the sum of the absolute values ​​exceeds a preset complementarity judgment threshold. After complementarity exclusion, the asymmetry of the remaining pipelines is judged by a preset threshold. This can reliably distinguish target pipelines with highly consistent positive and negative half-cycle magnetic field responses from the parallel pipeline group. The entire identification process does not rely on the inversion of the spatial distribution of the underground electromagnetic field, nor does it require pre-calibration of the pipeline burial depth or soil medium parameters. The judgment can be completed solely based on the electrical quantities that can be directly picked up from the surface of each pipeline. Attached Figure Description

[0017] Figure 1 This is a flowchart of a parallel pipeline identification method based on signal direction according to the present invention; Figure 2 This is a schematic diagram of the structure of a parallel pipeline identification system based on signal direction according to the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] Example 1: Figure 1 This invention presents a parallel pipeline identification method based on signal direction, which includes the following steps: S1: Inject a pulsating current signal with a preset period into one end of the target pipeline; S2: Select a reference point on the target pipeline and place a magnetic field sensor with two orthogonal sensing axes at the reference point; S3: For at least two pipelines in a parallel pipeline laying section, respectively, make the magnetic field sensor approach the surface of each pipeline in any posture to obtain the first direction component and the second direction component corresponding to each pipeline. S4: For each pipeline, map the first direction component and the second direction component to complex vectors on the complex plane, obtain the first complex vector trajectory during the positive half-cycle of the pulsating current signal and the second complex vector trajectory during the negative half-cycle, and calculate the closed area enclosed by the first complex vector trajectory and the reversed second complex vector trajectory on the complex plane as the asymmetry of the pipeline. S5: Select one of at least two pipelines as the pipeline to be tested, compare the asymmetry of the pipeline to be tested with the asymmetry of at least one adjacent pipeline, and if the values ​​are complementary, determine that the pipeline to be tested is a non-target pipeline and exclude it. S6: For pipelines that have not been excluded, if they do not meet the requirements of numerical complementarity and asymmetry less than a preset threshold, then the pipeline is determined to be the target pipeline.

[0020] When implementing S1, a square wave current signal with alternating positive and negative half cycles is generated by a signal generator. The period of the square wave current signal is set to a preset period. The output terminal of the signal generator is connected to the metal sheath or conductor of the target pipeline, and the grounding terminal of the signal generator is connected to the earth. A square wave current signal with a preset period is injected into one end of the target pipeline as a pulsating current signal.

[0021] The signal generator is a DC power supply device capable of outputting bipolar square wave current. Internally, it has a polarity switching circuit that alternately switches the polarity of the output current at set time intervals, forming a square wave current signal with alternating positive and negative half-cycles. During the positive half-cycle, current flows from the signal generator output to the target pipeline, and during the negative half-cycle, current flows back from the ground through the signal generator. The positive and negative half-cycles together form a complete cycle.

[0022] The operation method for setting the period of the square wave current signal to a preset period is as follows: The preset period is determined based on the target pipeline's capacitance to ground and leakage resistance along the pipeline. When the target pipeline is long or has a large capacitance to ground, a longer half-cycle duration is required to ensure that the pipeline's capacitance to ground can be fully charged or discharged during the positive or negative half-cycle. In this case, the preset period is set to a longer value, for example, 4 to 8 times the time constant required for the target pipeline's capacitance to ground to charge to 63% of the injection voltage. When the target pipeline is short or has a small capacitance to ground, the pipeline's capacitance to ground charges and discharges rapidly. In this case, the preset period is set to a shorter value, for example, 2 to 4 times the time constant required for the pipeline's capacitance to ground to charge. The preset period is set via the period adjustment knob on the signal generator or the parameter input interface. The internal controller of the signal generator controls the timing of the polarity switching circuit based on the set preset period.

[0023] The procedure for connecting the signal generator output to the target pipeline's metal sheath or conductor is as follows: If the target pipeline is a cable and a square wave current signal needs to be injected into the metal sheath, use insulated test leads to connect the signal generator output to the exposed part of the target pipeline's metal sheath or the metal sheath grounding lead; if the target pipeline is a cable and a square wave current signal needs to be injected into the conductor, use insulated test leads to connect the signal generator output to the conductor terminal of the target pipeline. During connection, ensure good contact between the test leads and the metal sheath or conductor, with a contact resistance of less than 10 ohms, to avoid poor contact that could distort the injected current waveform.

[0024] The procedure for connecting the signal generator's grounding terminal to the earth is as follows: Connect the signal generator's grounding terminal to a grounding electrode inserted into the earth via a grounding wire. The grounding electrode is inserted vertically into the earth, with the insertion depth determined by the soil resistivity. For example, in dry soil areas, the insertion depth is 30 to 50 centimeters, and in moist soil areas, the insertion depth is 20 to 30 centimeters. The grounding resistance between the grounding electrode and the earth should be less than 50 ohms to ensure that the current can smoothly flow back from the earth to the signal generator during the negative half-cycle of the square wave current signal.

[0025] After connecting the signal generator output to the target pipeline's metal sheath or conductor and connecting the signal generator grounding terminal to the earth, the signal generator output is activated. The signal generator injects a square wave current signal with a preset period into one end of the target pipeline as a pulsating current signal. The injected pulsating current signal propagates along the target pipeline's metal sheath or conductor towards the distant grounding point, forming an electromagnetic response around the target pipeline synchronized with the pulsating current signal. During the positive half-cycle of the pulsating current signal, the current flows from the injection end to the distant grounding point; during the negative half-cycle, the current flows back from the distant grounding point through the earth. The current directions of the positive and negative half-cycles are opposite and alternate, with the alternation frequency determined by the reciprocal of the preset period. After injection, a pulsating current signal with a preset period and alternating positive and negative half-cycles exists on the target pipeline, providing an excitation source for subsequently deploying a magnetic field sensor at the reference point and acquiring the directional components of each pipeline within the parallel pipeline laying section.

[0026] When implementing S2, a reference point is selected in the exposed section of the target pipeline that is not covered by parallel laying. A magnetic field sensor with a first sensitive axis and a second sensitive axis is fixed on the surface of the target pipeline at the reference point. The first sensitive axis and the second sensitive axis are orthogonally arranged in a plane perpendicular to the pipeline axis. The first sensitive axis picks up the reference first direction component, and the second sensitive axis picks up the reference second direction component.

[0027] The magnetic field sensor is a biaxial magnetoresistive sensor, integrating a first magnetoresistive sensing element and a second magnetoresistive sensing element. The first magnetoresistive sensing element is sensitive to the magnetic field component along a first sensitive axis, while the second magnetoresistive sensing element is sensitive to the magnetic field component along a second sensitive axis. The first and second magnetoresistive sensing elements each form a Wheatstone bridge structure. After applying a bias voltage, the differential output voltage of the Wheatstone bridge is proportional to the magnitude of the magnetic field component along the corresponding sensitive axis. The magnetic field sensor is encapsulated in a non-magnetic housing with a curved contact surface at the bottom. The radius of curvature of this curved contact surface matches the outer diameter of common pipelines, for example, 15 mm to 50 mm. The top or side of the housing is marked with a first sensitive axis direction mark and a second sensitive axis direction mark. The first sensitive axis direction mark is a scribed or printed line, and the second sensitive axis direction mark is another scribed or printed line perpendicular to the first sensitive axis direction mark. The housing is also marked with an axial alignment mark, the direction of which is perpendicular to the plane containing the first and second sensitive axes.

[0028] After injecting a pulsating current signal with a preset period, an electromagnetic response synchronized with the pulsating current signal will exist around the target pipeline. When selecting a reference point on the target pipeline, choose an exposed section of the target pipeline that is not covered by other parallel pipelines. An exposed section refers to a section around the target pipeline within a plane perpendicular to the pipeline axis, with a radius equal to five times the pipeline diameter and centered on the pipeline axis, where no other metal pipelines are laid in parallel. Within the exposed section, the magnetic field on the surface of the target pipeline is mainly generated by the pulsating current signal within the target pipeline; the influence of the induced magnetic field generated by the induced current of the parallel pipelines is negligible. The specific procedure for determining the exposed section is as follows: observe along the direction of the target pipeline or scan using a pipeline path detector to find sections where the distance between the target pipeline and other pipelines is greater than five times the pipeline diameter, and select the midpoint of the section farthest from the nearest parallel pipeline as the reference point.

[0029] The procedure for fixing the magnetic field sensor to the target pipeline surface at the reference point is as follows: The arc-shaped contact surface at the bottom of the magnetic field sensor housing is placed against the target pipeline surface at the reference point, ensuring the axial alignment mark is parallel to the target pipeline axis. An elastic strap is used to wrap around the target pipeline and the magnetic field sensor housing, pressing the magnetic field sensor firmly to the target pipeline surface. The elastic strap is made of elastic fabric or rubber, with both ends connected by buckles or Velcro. The tightening force of the elastic strap ensures a tight fit between the arc-shaped contact surface at the bottom of the magnetic field sensor housing and the target pipeline surface, with a gap of less than 1 mm. When fixing the magnetic field sensor, its rotational attitude around the pipeline axis is adjusted so that the plane containing the first and second sensitive axis direction marks is perpendicular to the pipeline axis. Since the axial alignment mark is parallel to the pipeline axis and perpendicular to the plane containing the first and second sensitive axes, when the axial alignment mark is parallel to the pipeline axis, the first and second sensitive axes automatically lie in a plane perpendicular to the pipeline axis, thus achieving an orthogonal arrangement of the first and second sensitive axes in a plane perpendicular to the pipeline axis.

[0030] The specific process of picking up the reference first direction component from the first sensitive axis and the reference second direction component from the second sensitive axis is as follows: A bias voltage is applied to the magnetic field sensor. The bias voltage is a DC voltage, for example, a bias voltage of 5 volts. When the pulsating current signal flows through the target pipeline, an alternating magnetic field is generated around the target pipeline. The direction and magnitude of the alternating magnetic field change alternately with the polarity switching of the pulsating current signal. The first magnetoresistive sensing element senses the component of the alternating magnetic field in the direction of the first sensitive axis and converts it into a first differential voltage signal through a Wheatstone bridge of the first magnetoresistive sensing element. The first differential voltage signal is the reference first direction component. The second magnetoresistive sensing element senses the component of the alternating magnetic field in the direction of the second sensitive axis and converts it into a second differential voltage signal through a Wheatstone bridge of the second magnetoresistive sensing element. The second differential voltage signal is the reference second direction component.

[0031] Both the first and second reference direction components are time-varying analog voltage signals. The amplitude of the analog voltage signal is proportional to the magnitude of the magnetic field component in the corresponding sensitive axis direction, and the polarity of the analog voltage signal reflects the positive or negative direction of the magnetic field component in the corresponding sensitive axis direction. Together, the first and second reference direction components record complete information about the magnetic field vector around the target pipeline at the reference point in a plane perpendicular to the pipeline's axial direction. When acquiring the first and second reference direction components, the magnetic field sensor is connected to the data acquisition device via a signal cable. The signal cable transmits the first and second differential voltage signals to the two analog input channels of the data acquisition device, respectively. The data acquisition device synchronously samples the two analog input channels at a sampling rate no less than 20 times the frequency corresponding to the preset period of the pulsating current signal, converting the analog voltage signals into digital signals to obtain the digital sampling sequences of the first and second reference direction components. The sampled digital signals are stored in the memory of the data acquisition device. After the above picking and sampling are completed, the reference first direction component and reference second direction component at the reference point have been recorded, providing a reference benchmark for subsequent acquisition of the first direction component and second direction component of each pipeline in the parallel pipeline laying section and for target pipeline identification.

[0032] When implementing S3, at least two pipelines are identified in the parallel pipeline laying section. The magnetic field sensor is sequentially attached to the surface of each pipeline. Each time it is attached, the magnetic field sensor contacts the pipeline surface in any spatial posture. The first direction component under the attachment posture is picked up by the first sensitive axis, and the second direction component under the attachment posture is picked up by the second sensitive axis. The first direction component and the second direction component corresponding to each pipeline are recorded.

[0033] After acquiring and recording the reference first and second direction components at the reference point, the operator, carrying a magnetic field sensor and data acquisition device, moves to the parallel pipeline laying section. A parallel pipeline laying section refers to a section where multiple pipelines are laid adjacent to each other along the same direction, with the distance between adjacent pipelines within the section less than three times the pipeline diameter. Before entering the parallel pipeline laying section, the operator conducts a visual inspection along the section's direction or scans it using a pipeline path detector to confirm the number of pipelines laid within the section, ensuring that at least two pipelines exist within the section. Every visible or accessible pipeline within the section is considered as the pipeline for which data is to be acquired.

[0034] The procedure for sequentially attaching the magnetic field sensor to the surface of each pipeline is as follows: The operator holds the magnetic field sensor and approaches each pipeline one by one along the direction of the parallel pipeline section. For the pipeline to be approached, the operator moves the magnetic field sensor near the pipeline surface, so that the arc-shaped contact surface at the bottom of the magnetic field sensor housing faces the pipeline surface. The operator places the arc-shaped contact surface at the bottom of the magnetic field sensor housing against the pipeline surface. There is no need to deliberately adjust the rotational attitude of the magnetic field sensor around the pipeline axis, nor is it necessary to align the axial alignment mark with the pipeline axis. Each time the magnetic field sensor is approached, it contacts the pipeline surface in any spatial orientation. Any spatial orientation refers to the sensor orientation determined by the operator's natural wrist posture when holding the magnetic field sensor. It is not required that the sensor orientation be exactly the same each time it is approached, nor is it required that the first and second sensitive axes be in a plane perpendicular to the pipeline axis. The magnetic field sensor has two orthogonal measurement axes, a first sensitive axis and a second sensitive axis. Regardless of the spatial orientation of the magnetic field sensor when it is close to the pipeline surface, the projection components of the first and second sensitive axes in the plane perpendicular to the pipeline axis can always capture the magnetic field vector information of the surrounding magnetic field in the plane perpendicular to the pipeline axis. Although the angle between the orthogonal coordinate system formed by the first and second sensitive axes and the surrounding magnetic field vector is different under any spatial orientation of the magnetic field sensor, the composite result of the components picked up by the two sensitive axes completely represents the representation of the magnetic field vector in the orthogonal coordinate system. Subsequent processing by mapping the dual-axis components to a complex vector can eliminate the influence of attitude differences.

[0035] The specific process of picking up the first direction component of the proximity attitude using the first sensitive axis and the second direction component using the second sensitive axis is as follows: A bias voltage is applied to the magnetic field sensor close to the pipeline surface. The amplitude of the bias voltage is the same as the bias voltage applied during the pickup operation at the reference point, for example, a bias voltage of 5 volts. The alternating magnetic field generated when the pulsating current signal flows through the target pipeline, and the superimposed magnetic field generated by the induced current in the parallel pipeline, act together at the location of the magnetic field sensor. The first magnetoresistive sensing element senses the component of the superimposed magnetic field in the direction of the first sensitive axis and converts it into a first differential voltage signal through the Wheatstone bridge of the first magnetoresistive sensing element. The first differential voltage signal is the first direction component in the proximity attitude. The second magnetoresistive sensing element senses the component of the superimposed magnetic field in the direction of the second sensitive axis and converts it into a second differential voltage signal through the Wheatstone bridge of the second magnetoresistive sensing element. The second differential voltage signal is the second direction component in the proximity attitude. The data acquisition device is connected to the magnetic field sensor via a signal cable. It synchronously samples the first differential voltage signal and the second differential voltage signal at the same sampling rate as at the reference point. The sampling rate is not less than 20 times the frequency corresponding to the preset period of the pulsating current signal. The analog voltage signal is converted into a digital signal to obtain the digital sampling sequence of the first directional component and the digital sampling sequence of the second directional component corresponding to the current proximity to the pipeline.

[0036] The operation method for recording the first and second directional components corresponding to each pipeline is as follows: After sampling the first and second directional components of the currently approached pipeline, the data acquisition device stores the digital sampling sequences of the first and second directional components in its memory and assigns a pipeline number to the currently approached pipeline. The pipeline number is an integer starting from 1 and incrementing sequentially. The first approached pipeline is assigned pipeline number 1, the second approached pipeline is assigned pipeline number 2, and so on. The pipeline number of each pipeline is associated with and stored in conjunction with the digital sampling sequences of the first and second directional components. After the operator completes the approach, pickup, and recording for the current pipeline, the magnetic field sensor is removed from the surface of the current pipeline, and the operator moves to the surface of the next pipeline to repeat the approach, pickup, and recording operation until data acquisition has been completed for all identified pipelines in the parallel pipeline laying section. After all pipelines have been picked up, the memory of the data acquisition device stores the pipeline number, the digital sampling sequence of the first directional component, and the digital sampling sequence of the second directional component for each pipeline. The stored data is used as input data for subsequent complex vector mapping, complex vector trajectory extraction, and closed area calculation for each pipeline.

[0037] When implementing S4, a complex plane is constructed with the first directional component as the real part and the second directional component as the imaginary part. The instantaneous values ​​of the first and second directional components of the pulsating current signal in each cycle are mapped to complex vectors on the complex plane. All complex vectors during the positive half-cycle are extracted to form the first complex vector trajectory, and all complex vectors during the negative half-cycle are extracted to form the second complex vector trajectory. The direction of the second complex vector trajectory is reversed to obtain the reversed second complex vector trajectory. The closed area occupied by the non-overlapping parts of the region enclosed by the first complex vector trajectory and the region enclosed by the reversed second complex vector trajectory on the complex plane is calculated, and the closed area is used as the asymmetry of the pipeline.

[0038] The operation method for constructing a complex plane with the first directional component as the real part and the second directional component as the imaginary part is as follows: After the data acquisition device completes the recording of the first and second directional components of all pipelines in the parallel pipeline laying section, for each pipeline, the digital sampling sequence of the first and second directional components corresponding to the pipeline is retrieved from the memory of the data acquisition device. Each sample value in the digital sampling sequence of the first directional component corresponds to an instantaneous value of the first directional component, and the sample values ​​at the same moment in the digital sampling sequence of the second directional component correspond to an instantaneous value of the second directional component. The instantaneous value of the first directional component is used as the abscissa of the Cartesian coordinate system, and the instantaneous value of the second directional component is used as the ordinate of the Cartesian coordinate system. The abscissa of the Cartesian coordinate system represents the real part, and the ordinate represents the imaginary part. The Cartesian coordinate system constitutes a complex plane. The instantaneous values ​​of the first and second directional components at each sampling moment correspond to a coordinate point on the complex plane. The complex number corresponding to the coordinate point is the complex vector. The real part of the complex vector is equal to the instantaneous value of the first directional component, and the imaginary part of the complex vector is equal to the instantaneous value of the second directional component. The operation method for mapping the instantaneous values ​​of the first and second directional components of each cycle of the pulsating current signal to complex vectors on the complex plane is as follows: according to the order of sampling time, the instantaneous values ​​of the first and second directional components at each sampling time are converted into a coordinate point on the complex plane one by one, and the coordinate points of all sampling times form a trajectory curve that unfolds over time on the complex plane.

[0039] The operation method for extracting all complex vectors during the positive half-cycle to form the first complex vector trajectory is as follows: The start and end times of each positive half-cycle are determined according to the preset period of the pulsating current signal. The start time of the positive half-cycle is the moment when the current jumps from zero to the positive direction in each cycle, and the end time is the moment when the current jumps from the positive to the negative direction in each cycle. The start and end times are determined by identifying the sign change points of the instantaneous values ​​of the first or second directional components. The complex vectors corresponding to all sampling points between the start and end times in each cycle are arranged in chronological order, and the complex vectors extracted from all cycles are merged to form the first complex vector trajectory. The operation method for extracting all complex vectors during the negative half-cycle to form the second complex vector trajectory is as follows: The start and end times of each negative half-cycle are determined according to the preset period of the pulsating current signal. The start time of the negative half-cycle is the moment when the current jumps from zero to the negative direction in each cycle, and the end time is the moment when the current jumps from the negative to the positive direction in each cycle. Arrange the complex vectors corresponding to all sampling points between the start and end times of the negative half-cycle in each cycle in chronological order, and merge the complex vectors extracted from all cycles to form the second complex vector trajectory.

[0040] The operation of reversing the direction of the second complex vector trajectory to obtain the reversed second complex vector trajectory is as follows: Each complex vector contained in the second complex vector trajectory is inverted by taking the opposite of both the real and imaginary parts. This inversion causes the second complex vector trajectory to rotate 180 degrees around the origin in the complex plane, resulting in the reversed second complex vector trajectory. The positional relationship between the reversed second complex vector trajectory and the first complex vector trajectory in the complex plane reflects the degree of consistency in the magnetic field response during the positive and negative half-cycles.

[0041] The operation for calculating the closed area occupied by the non-overlapping portions of the regions enclosed by the first complex vector trajectory and the reversed second complex vector trajectory on the complex plane is as follows: Connect the beginning and end of the first complex vector trajectory with straight line segments to form a first closed curve, and connect the beginning and end of the reversed second complex vector trajectory with straight line segments to form a second closed curve. Calculate the difference between the union area and the intersection area of ​​the regions enclosed by the first and second closed curves, and use this difference as the closed area. In the specific processing, determine the positions of the first and last points of the first complex vector trajectory. The first point is the coordinate point of the complex vector corresponding to the first sampling point of the positive half-cycle on the complex plane, and the last point is the coordinate point of the complex vector corresponding to the last sampling point of the positive half-cycle on the complex plane. Connect the last point to the first point with a straight line segment. This straight line segment, together with the curve of the first complex vector trajectory itself, forms a closed region. The curve of the first complex vector trajectory itself and the straight line segment connecting the first and last points constitute the first closed curve. Similarly, the starting and ending points of the reversed second complex vector trajectory are determined. A straight line segment is drawn from the ending point to the starting point. The curve of the reversed second complex vector trajectory itself, together with the straight line segment connecting the starting and ending points, forms the second closed curve. A geometric union operation is performed on the regions enclosed by the first and second closed curves in the complex plane to obtain the union region, and a geometric intersection operation is performed to obtain the intersection region. The difference between the area of ​​the union region and the area of ​​the intersection region is the closed area occupied by the non-overlapping parts of the regions enclosed by the first and second closed curves in the complex plane. The geometric union and geometric intersection operations are implemented using a point-by-point scanning method. The complex plane is discretized into a grid. The regions enclosed by the first and second closed curves are marked with fill marks. The number of grid cells covered by at least one region is counted and multiplied by the area of ​​the grid cell to obtain the union area. The number of grid cells covered by both regions simultaneously is counted and multiplied by the area of ​​the grid cell to obtain the intersection area. The closed area is used as the asymmetry of the pipeline, and the dimension of asymmetry is the square of the voltage. For example, the closed area is a value in square millivolts. Asymmetry reflects the degree to which the polarization trajectories of the positive half-cycle magnetic field response and the negative half-cycle magnetic field response on the complex plane of a pipeline do not overlap.

[0042] After calculating the closed area on the complex plane occupied by the non-overlapping portions of the regions enclosed by the first complex vector trajectory and the reversed second complex vector trajectory, the calculated closed area is stored in the memory of the data acquisition device in association with the pipeline number. After completing the calculation and storage of the closed area for each pipeline, the memory stores the pipeline number and the corresponding asymmetry for each pipeline, providing a data basis for subsequent comparison of the asymmetry of adjacent pipelines.

[0043] When implementing S5, any one of the pipelines whose asymmetry calculation has been completed is selected as the pipeline to be tested. The asymmetry of the pipeline to be tested is compared with the asymmetry of at least one adjacent pipeline. If the asymmetry of the pipeline to be tested and the asymmetry of the adjacent pipelines show a trend of mutual inversion and opposite polarities, the pipeline to be tested is determined to be a non-target pipeline and is excluded from the subsequent judgment process.

[0044] After calculating the closed area of ​​all pipelines within the parallel pipeline laying section and storing the closed area as an asymmetry degree associated with the pipeline sequence number, the pipeline sequence number and corresponding asymmetry degree of all pipelines are retrieved from the memory of the data acquisition device. The asymmetry degree includes the polarity assigned during the closed area calculation in S4. The polarity of the closed area is determined based on the coverage relationship of the area enclosed by the first complex vector trajectory relative to the area enclosed by the reversed second complex vector trajectory on the complex plane. If the coverage area of ​​the area enclosed by the first complex vector trajectory is greater than the coverage area of ​​the area enclosed by the reversed second complex vector trajectory, the closed area is positive; if the coverage area of ​​the area enclosed by the first complex vector trajectory is less than the coverage area of ​​the area enclosed by the reversed second complex vector trajectory, the closed area is negative. All pipelines for which asymmetry degree calculation has been completed are arranged according to the spatial arrangement order of pipeline laying. The spatial arrangement order is the actual physical arrangement order of the pipelines within the parallel pipeline laying section in the plane perpendicular to the pipeline axis. The spatial arrangement order is determined as follows: Operators record the pipeline numbers sequentially from left to right or top to bottom within the parallel pipeline laying section according to the actual pipeline arrangement position. The recorded pipeline number sequence is then input into the data acquisition device as the spatial arrangement order. The data acquisition device determines the adjacent pipelines for each pipeline based on the input spatial arrangement order. Adjacent pipelines are those that are immediately next to each other in the spatial arrangement order. A pipeline can have one or two adjacent pipelines. Pipelines at both ends of the spatial arrangement order each have one adjacent pipeline, and pipelines in the middle of the spatial arrangement order each have two adjacent pipelines. Any pipeline from all pipelines for which asymmetry calculations have been completed is selected as the pipeline to be tested. Based on the position of the pipeline to be tested in the spatial arrangement order, at least one adjacent pipeline is determined. The operation method for comparing the asymmetry of the pipeline to be tested with the asymmetry of at least one adjacent pipeline is as follows: For a pipeline to be tested with one adjacent pipeline, the asymmetry of the pipeline to be tested is compared with the asymmetry of that adjacent pipeline. For a pipeline under test with two adjacent pipelines, first compare the asymmetry of the pipeline under test with the asymmetry of the first adjacent pipeline, and then compare the asymmetry of the pipeline under test with the asymmetry of the second adjacent pipeline.

[0045] During pairwise comparisons, the asymmetry of the pipeline under test is obtained by algebraically summing the asymmetry of its adjacent pipelines. If the algebraic sum approaches zero and the sum of the absolute values ​​of the asymmetry of the pipeline under test and its adjacent pipelines exceeds a preset complementarity threshold, then the asymmetry is determined to be inversely proportional and opposite in polarity. The operation to obtain the algebraic sum of the asymmetry of the pipeline under test and its adjacent pipelines is as follows: algebraically add the asymmetry of the pipeline under test and its adjacent pipelines. The condition for the algebraic sum to approach zero is that the absolute value of the algebraic sum is less than 1 / 10 of the absolute value of the asymmetry of the pipeline under test. For example, this ratio can be adjusted to 1 / 5 or 1 / 20 based on the actual coupling characteristics of the parallel pipelines. The sum of absolute values ​​is the result of adding the absolute values ​​of the asymmetry of the pipeline under test and the absolute values ​​of the asymmetry of its adjacent pipelines. If the sum of the absolute values ​​is greater than the preset complementarity threshold, it indicates that the values ​​of both asymmetries are relatively large, eliminating the possibility that the algebraic sum might accidentally approach zero due to excessively small values. This reliably confirms the existence of a complementary relationship between the two asymmetries. The preset complementarity threshold is set as follows: after calculating the asymmetries of all pipelines, obtain the absolute value of the largest asymmetry among all pipelines. Multiply this absolute value by a preset proportional coefficient to obtain the preset complementarity threshold. The preset proportional coefficient is determined based on the coupling strength between pipelines within the parallel pipeline laying section. Smaller pipeline spacing and stronger coupling result in a larger preset proportional coefficient, for example, 0.3 to 0.5. Larger pipeline spacing and weaker coupling result in a smaller preset proportional coefficient, for example, 0.1 to 0.3. The preset proportional coefficient is set by the operator on the data acquisition device based on the actual spacing of the parallel pipeline laying section.

[0046] If the asymmetry of the pipeline under test exhibits an inverse relationship with the asymmetry of at least one adjacent pipeline, and their polarities are opposite, then the pipeline under test is determined to be a non-target pipeline and is excluded from subsequent judgment processes. The exclusion process involves marking the pipeline as a non-target pipeline in the data acquisition device, and pipelines marked as excluded will no longer participate in subsequent judgments. The complementary asymmetry characteristics exhibited on non-target pipelines stem from the induced current formed by the inductive coupling of parallel pipelines, creating a reverse circulation between adjacent pipelines. This reverse circulation generates superimposed magnetic fields in opposite directions on the surfaces of the two pipelines, causing the asymmetry values ​​of the positive and negative half-cycle magnetic field responses on their respective pipelines to exhibit an inverse relationship. By identifying and excluding pipelines with complementary asymmetry, non-target pipelines with spurious responses due to inductive coupling can be removed from the candidate pipeline set. After performing pairwise comparisons and complementary judgments on all pipelines, pipelines not marked as excluded in the data acquisition device are considered as not excluded pipelines and enter the subsequent judgment process.

[0047] When implementing S6, all remaining pipelines after elimination are checked in sequence. If the adjacent pipeline of a certain pipeline in the remaining pipeline has been eliminated or the asymmetry between the pipeline and the remaining adjacent pipeline does not show a zero-sum trend and the polarity is opposite, and the asymmetry of the pipeline is less than the preset threshold, then the corresponding pipeline is determined to be the target pipeline.

[0048] After marking pipelines with complementary asymmetry as excluded, a portion of the pipelines in the data acquisition device's memory are marked as excluded, while the remaining pipelines are not. These unmarked pipelines constitute the remaining pipelines. The remaining pipelines form a candidate pipeline set, which may contain one or more pipelines. The process of checking the remaining pipelines is as follows: the data acquisition device reads the pipeline number of each remaining pipeline in spatial order, and retrieves the information of adjacent pipelines, asymmetry, and recorded exclusion status markers from the memory based on the pipeline number. For each remaining pipeline, the following checks are performed: adjacent pipeline exclusion status check, asymmetry complementarity check with remaining adjacent pipelines, and asymmetry threshold check.

[0049] The procedure for checking the exclusion status of adjacent pipelines is as follows: Check whether the adjacent pipelines of the remaining pipeline have been marked as excluded during the pairwise comparison process. If at least one adjacent pipeline of the remaining pipeline has been marked as excluded, it indicates that the complementary relationship of the asymmetry of the remaining pipeline has been broken. The asymmetry existing on the remaining pipeline is not caused by the complementary effect of inductive coupling with the excluded adjacent pipelines. The remaining pipeline remains in the candidate pipeline set and enters the asymmetry threshold check. If none of the adjacent pipelines of the remaining pipeline have been marked as excluded, meaning all adjacent pipelines remain in the candidate pipeline set, further check whether the asymmetry of the remaining pipeline and its remaining adjacent pipelines exhibits an inverse relationship with opposite polarities.

[0050] The procedure for checking the complementary relationship between the remaining pipeline and its adjacent pipelines is as follows: The asymmetry of the remaining pipeline is compared pairwise with the asymmetry of each of its adjacent pipelines. The pairwise comparison method involves obtaining the algebraic sum of the asymmetry of the remaining pipeline and its adjacent pipelines. If the algebraic sum approaches zero and the sum of the absolute values ​​of the asymmetry of the remaining pipeline and its adjacent pipelines exceeds a preset complementarity threshold, then a mutually exclusive relationship is identified with opposite polarities. If the asymmetry of the remaining pipeline and any adjacent pipeline exhibits a mutually exclusive relationship with opposite polarities, it indicates that an induced coupling complementary relationship still exists between the remaining pipeline and its adjacent pipelines. The remaining pipeline is then marked as excluded and removed from the candidate pipeline set. If the asymmetry of the remaining pipeline and all its adjacent pipelines does not exhibit a mutually exclusive relationship with opposite polarities, the remaining pipeline remains in the candidate pipeline set and enters the asymmetry threshold check. For the remaining pipelines that have only one adjacent pipeline in the spatial arrangement order and whose adjacent pipelines have been excluded, skip the complementary situation check and proceed directly to the asymmetry threshold check.

[0051] The asymmetry threshold check is performed by comparing the asymmetry of the remaining pipelines in the candidate pipeline set after adjacent pipeline exclusion checks and complementary status checks with a preset threshold. The preset threshold distinguishes between residual asymmetry on the target pipeline caused by measurement noise or minor environmental fluctuations and significant asymmetry caused by inductive coupling effects. On the target pipeline, due to the high symmetry between the positive and negative half-cycle magnetic field responses, the asymmetry should be close to zero, while on non-target pipelines, the asymmetry value caused by inductive coupling effects is relatively large. The preset threshold is set as follows: after calculating the asymmetry of all pipelines, before performing the complementarity determination, the absolute value of the largest asymmetry among all pipelines is obtained. This absolute value is then multiplied by a preset threshold scaling factor to obtain the preset threshold. The preset threshold scaling factor is determined based on the consistency of the pipeline's capacitance to ground and leakage resistance along the pipeline. When pipeline laying conditions are consistent and pipeline parameter differences are small, a smaller preset threshold scaling factor is used, for example, 0.05 to 0.15. When pipeline laying conditions vary significantly or pipeline parameters are inconsistent, a larger preset threshold ratio coefficient is used, for example, a preset threshold ratio coefficient of 0.15 to 0.3. The preset threshold ratio coefficient is set by the operator on the data acquisition device based on the actual laying conditions of the parallel pipeline section. If the asymmetry of the remaining pipeline is less than the preset threshold, the remaining pipeline is determined to be the target pipeline. If the asymmetry of the remaining pipeline is greater than or equal to the preset threshold, it indicates that there are other asymmetric factors on the remaining pipeline besides non-complementary induction effects. The remaining pipeline is then marked as pending confirmation, and the operator manually verifies the remaining pipeline.

[0052] After sequentially performing adjacent pipeline exclusion status checks, complementary status checks, and asymmetry threshold checks on all remaining pipelines in the candidate pipeline set, the remaining pipelines identified as target pipelines in the data acquisition device are the identified target pipelines. When multiple remaining pipelines exist in the candidate pipeline set and all meet the target pipeline determination criteria, the remaining pipeline with the smallest asymmetry is determined as the target pipeline, and the remaining pipelines that meet the determination criteria are marked as pending confirmation. After the target pipeline determination is completed, the data acquisition device displays the pipeline number determined as the target pipeline and the corresponding asymmetry value. The operator locates the target pipeline within the parallel pipeline laying section based on the displayed pipeline number.

[0053] Example 2: Figure 2 A schematic diagram of a parallel pipeline identification system based on signal direction according to the present invention is provided. The parallel pipeline identification system based on signal direction includes the following modules: The pulsating signal injection module is used to inject a pulsating current signal with a preset period into one end of the target pipeline. The reference point sensing arrangement module is used to select a reference point on the target pipeline and arrange a magnetic field sensor with two orthogonal sensing axes at the reference point. The dual-axis component acquisition module is used to obtain the first and second direction components of each pipeline by having a magnetic field sensor approach the surface of each pipeline in any orientation within a parallel pipeline laying section. The asymmetry calculation module is used to map the first direction component and the second direction component into complex vectors on the complex plane for each pipeline, obtain the first complex vector trajectory during the positive half-cycle of the pulsating current signal and the second complex vector trajectory during the negative half-cycle, and calculate the closed area enclosed by the first complex vector trajectory and the reversed second complex vector trajectory on the complex plane as the asymmetry of the pipeline. The adjacent line comparison and exclusion module is used to select one of at least two pipelines as the pipeline to be tested, compare the asymmetry of the pipeline to be tested with the asymmetry of at least one adjacent pipeline, and if the values ​​are complementary, the pipeline to be tested is determined to be a non-target pipeline and is excluded. The target pipeline determination module is used to determine if a pipeline that has not been excluded is a target pipeline if it does not meet the requirements of numerical complementarity and asymmetry less than a preset threshold.

[0054] All calculations involved in the embodiments are dimensionless numerical calculations, and the preset parameters and thresholds in the calculations are set by those skilled in the art according to the actual situation.

[0055] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, in the form of a computer program product.

[0056] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and inventive constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0057] In addition, the functional modules in the various embodiments of this application can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0058] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of modules is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple modules or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or modules may be electrical, mechanical, or other forms.

[0059] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0060] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A parallel pipeline identification method based on signal direction, characterized in that, Includes the following steps: S1: Inject a pulsating current signal with a preset period into one end of the target pipeline; S2: Select a reference point on the target pipeline and place a magnetic field sensor with two orthogonal sensing axes at the reference point; S3: For at least two pipelines in a parallel pipeline laying section, respectively, make the magnetic field sensor approach the surface of each pipeline in any posture to obtain the first direction component and the second direction component corresponding to each pipeline. S4: For each pipeline, map the first direction component and the second direction component to complex vectors on the complex plane, obtain the first complex vector trajectory during the positive half-cycle of the pulsating current signal and the second complex vector trajectory during the negative half-cycle, and calculate the closed area enclosed by the first complex vector trajectory and the reversed second complex vector trajectory on the complex plane as the asymmetry of the pipeline. S5: Select one of at least two pipelines as the pipeline to be tested, compare the asymmetry of the pipeline to be tested with the asymmetry of at least one adjacent pipeline, and if the values ​​are complementary, determine that the pipeline to be tested is a non-target pipeline and exclude it. S6: For pipelines that have not been excluded, if they do not meet the requirements of numerical complementarity and asymmetry less than a preset threshold, then the pipeline is determined to be the target pipeline.

2. The parallel pipeline identification method based on signal direction according to claim 1, characterized in that, S1 includes: A square wave current signal with alternating positive and negative half cycles is generated by a signal generator. The period of the square wave current signal is set to a preset period. The output terminal of the signal generator is connected to the metal sheath or conductor of the target pipeline, and the ground terminal of the signal generator is connected to the earth. A square wave current signal with a preset period is injected into one end of the target pipeline as a pulsating current signal.

3. The parallel pipeline identification method based on signal direction according to claim 1, characterized in that, S2 includes: selecting a reference point in an exposed section of the target pipeline that is not covered by parallel laying, fixing a magnetic field sensor with a first sensitive axis and a second sensitive axis on the surface of the target pipeline at the reference point, the first sensitive axis and the second sensitive axis being orthogonally arranged in a plane perpendicular to the pipeline axis, the first sensitive axis picking up a reference first direction component, and the second sensitive axis picking up a reference second direction component.

4. The parallel pipeline identification method based on signal direction according to claim 1, characterized in that, S3 includes: identifying at least two pipelines within the parallel pipeline laying section, sequentially attaching a magnetic field sensor to the surface of each pipeline, with the magnetic field sensor contacting the pipeline surface in any spatial orientation each time it is attached, picking up the first direction component under the attachment orientation by the first sensitive axis, picking up the second direction component under the attachment orientation by the second sensitive axis, and recording the first and second direction components corresponding to each pipeline.

5. The parallel pipeline identification method based on signal direction according to claim 1, characterized in that, S4 includes: A complex plane is constructed with the first directional component as the real part and the second directional component as the imaginary part. The instantaneous values ​​of the first and second directional components of the pulsating current signal in each cycle are mapped to complex vectors on the complex plane. All complex vectors during the positive half-cycle are extracted to form the first complex vector trajectory, and all complex vectors during the negative half-cycle are extracted to form the second complex vector trajectory. The direction of the second complex vector trajectory is reversed to obtain the reversed second complex vector trajectory. The closed area occupied by the non-overlapping parts of the region enclosed by the first complex vector trajectory and the region enclosed by the reversed second complex vector trajectory on the complex plane is calculated, and the closed area is used as the asymmetry of the pipeline.

6. The parallel pipeline identification method based on signal direction according to claim 5, characterized in that, Calculating the closed area on the complex plane occupied by the non-overlapping portions of the region enclosed by the first complex vector trajectory and the region enclosed by the reversed second complex vector trajectory includes: connecting the beginning and end of the first complex vector trajectory with straight line segments to form a first closed curve, connecting the beginning and end of the reversed second complex vector trajectory with straight line segments to form a second closed curve, calculating the difference between the union area and the intersection area of ​​the region enclosed by the first closed curve and the region enclosed by the second closed curve, and using the difference as the closed area.

7. The parallel pipeline identification method based on signal direction according to claim 1, characterized in that, S5 includes: selecting any one of the pipelines whose asymmetry calculation has been completed as the pipeline to be tested; comparing the asymmetry of the pipeline to be tested with the asymmetry of at least one adjacent pipeline one by one; if the asymmetry of the pipeline to be tested and the asymmetry of the adjacent pipelines show a zero-sum trend and opposite polarities, then the pipeline to be tested is determined to be a non-target pipeline and is excluded from the subsequent determination process.

8. The parallel pipeline identification method based on signal direction according to claim 7, characterized in that, The asymmetry of the pipeline under test is compared with the asymmetry of at least one adjacent pipeline, including: obtaining the algebraic sum of the asymmetry of the pipeline under test and the asymmetry of the adjacent pipeline. If the algebraic sum approaches zero and the sum of the absolute values ​​of the asymmetry of the pipeline under test and the asymmetry of the adjacent pipeline exceeds the preset complementary judgment threshold, then it is determined that the asymmetry shows a trend of one increasing while the other decreases and the polarities are opposite.

9. The parallel pipeline identification method based on signal direction according to claim 1, characterized in that, S6 includes: All remaining pipelines after elimination are checked in sequence. If the adjacent pipelines of a certain pipeline in the remaining pipelines have been eliminated or the asymmetry between the pipeline and the remaining adjacent pipelines does not show a zero-sum trend and the polarity is opposite, and the asymmetry of the pipeline is less than the preset threshold, then the corresponding pipeline is determined to be the target pipeline.

10. A parallel pipeline identification system based on signal direction, used to implement the parallel pipeline identification method based on signal direction as described in any one of claims 1-9, characterized in that, Includes the following modules: The pulsating signal injection module is used to inject a pulsating current signal with a preset period into one end of the target pipeline. The reference point sensing arrangement module is used to select a reference point on the target pipeline and arrange a magnetic field sensor with two orthogonal sensing axes at the reference point. The dual-axis component acquisition module is used to obtain the first and second direction components of each pipeline by having a magnetic field sensor approach the surface of each pipeline in any orientation within a parallel pipeline laying section. The asymmetry calculation module is used to map the first direction component and the second direction component into complex vectors on the complex plane for each pipeline, obtain the first complex vector trajectory during the positive half-cycle of the pulsating current signal and the second complex vector trajectory during the negative half-cycle, and calculate the closed area enclosed by the first complex vector trajectory and the reversed second complex vector trajectory on the complex plane as the asymmetry of the pipeline. The adjacent line comparison and exclusion module is used to select one of at least two pipelines as the pipeline to be tested, compare the asymmetry of the pipeline to be tested with the asymmetry of at least one adjacent pipeline, and if the values ​​are complementary, the pipeline to be tested is determined to be a non-target pipeline and is excluded. The target pipeline determination module is used to determine if a pipeline that has not been excluded is a target pipeline if it does not meet the requirements of numerical complementarity and asymmetry less than a preset threshold.

Images