Shallow surface drilling tool positioning system based on magnetic field intensity and control method

Abstract

The invention discloses a shallow earth surface drilling tool positioning system based on magnetic field intensity and a control method thereof. The system comprises a magnetic field generator array, a magnetic sensor and an information processing module, wherein the magnetic sensor and the information processing module are arranged on a drilling tool; the magnetic field generator array is located at the corresponding position of the real-time position of the drilling tool, the magnetic field generator array comprises a plurality of magnetic field generators arranged in a preset array, and the working frequencies of the plurality of magnetic field generators are different preset frequencies; the magnetic sensor obtains a magnetic field signal of each magnetic field generator and sends the magnetic field signal to the information processing module; and the information processing module calculates an initial distance value between each magnetic field generator and the drilling tool according to the plurality of magnetic field signals, and calculates space coordinate data of the drilling tool by combining the plurality of initial distance values. By arranging the multi-frequency magnetic field generator array and combining with signal processing, the problems of accumulative errors, sight distance dependence, easy interference and the like in the prior art are solved, and stable, high-precision and real-time positioning of the drilling tool in a shallow earth surface complex environment is realized.

Description

Technical Field

[0001] This invention relates to the field of positioning and measurement technology, and in particular to a shallow surface drilling tool positioning system and control method based on magnetic field strength. Background Technology

[0002] In the field of shallow surface drilling engineering, such as urban rail transit, underground utility tunnel construction, and shallow resource exploration projects, achieving real-time and precise positioning of drilling tools is one of the core technologies to ensure construction quality and safety. Currently, common positioning technologies in the industry mainly include inertial navigation, laser positioning, and traditional magnetic positioning methods.

[0003] Specifically, inertial navigation systems recursively deduce position and attitude from accelerometer and gyroscope measurements, but errors accumulate over time, leading to decreased accuracy over long-term operation, and high-precision inertial devices are expensive. Laser positioning technology relies on optical line-of-sight, establishing a baseline at the starting shaft and deploying optical targets at the tunneling end for measurement. However, this method cannot penetrate obstacles and is easily affected by environmental factors such as dust and smoke at the construction site, causing signal interruption or failure. Traditional magnetic positioning technology can use magnetometers to measure magnetic field vectors and calculate position through model registration, but its algorithms are usually complex, computationally burdensome, have poor real-time performance, and insufficient numerical stability, and are extremely sensitive to measurement noise and external electromagnetic interference. In addition, traditional magnetic positioning devices often have a simple structure and low observability. In urban environments rich in metal structures or with strong interference, the magnetic field signal is easily distorted, resulting in a significant reduction in positioning accuracy. Summary of the Invention

[0004] The purpose of this invention is to provide a shallow surface drill bit positioning system and control method based on magnetic field strength. By deploying a multi-frequency magnetic field generator array and combining it with signal processing, the system effectively overcomes the problems of cumulative error, line-of-sight dependence and susceptibility to interference in the prior art, and achieves stable and high-precision real-time positioning of the drill bit in complex shallow surface environments.

[0005] To address the aforementioned technical problems, a first aspect of this invention provides a shallow surface drill bit positioning system based on magnetic field strength, comprising: a magnetic field generator array, a magnetic sensor disposed on the drill bit, and an information processing module; The magnetic field generator array is located at the corresponding position of the real-time position of the drill bit. The magnetic field generator array includes several magnetic field generators arranged in a preset array, and the operating frequencies of the several magnetic field generators are different preset frequencies. The magnetic sensor acquires the magnetic field signal of each of the magnetic field generators and sends it to the information processing module; The information processing module calculates the initial distance between each magnetic field generator and the drill bit based on several magnetic field signals, and calculates the spatial coordinate data of the drill bit by combining several initial distance values.

[0006] Furthermore, the preset array is a symmetrical arrangement with spatial constraints.

[0007] Furthermore, the preset array is an isosceles triangle or equilateral triangle arrangement based on the ground plane or a plane corresponding to a first preset depth below the ground, and the magnetic field generator array includes three magnetic field generators, which are respectively arranged at the vertices of the triangle.

[0008] Furthermore, the preset array is a spatial arrangement of three-dimensional triangles or regular tetrahedrons, and the magnetic field generator array includes at least four magnetic field generators. The at least four magnetic field generators are respectively set at the vertices of the three-dimensional triangles or regular tetrahedrons, at least one of the magnetic field generators is set at a second preset depth below the ground, and the remaining magnetic field generators are set on the ground.

[0009] Furthermore, when all the magnetic field generators in the magnetic field generator array are turned off simultaneously, the information processing module collects the background environmental magnetic field information of the drill bit through the magnetic sensor and records the background magnetic field spectrum, which includes the background magnetic field intensity at each preset frequency. When the magnetic field generators in the magnetic field generator array are turned on, the information processing module collects the magnetic field signal of each magnetic field generator through the magnetic sensor; Based on the background magnetic field spectrum, the information processing module performs background magnetic field differential processing on each magnetic field signal to obtain the net magnetic field strength of each magnetic field generator. The net magnetic field strength is the value of the magnetic field signal at the corresponding preset frequency minus the value of the background magnetic field spectrum at the same frequency.

[0010] Furthermore, the information processing module also performs adaptive filtering on the net magnetic field strength of each of the magnetic field generators. By calculating the mean and variance of the net magnetic field strength, the filtering parameters are adjusted in real time according to the changes in the net magnetic field strength to track low-frequency disturbances introduced by the slow drift of the underground magnetic field in the area where the drilling tool is located, and to suppress narrowband interference introduced by environmental electromagnetic interference.

[0011] Furthermore, the information processing module calculates the initial distance between the drill bit and each of the magnetic field generators based on the net magnetic field strength of each of the magnetic field generators using a near-field magnetic positioning model; The information processing module calculates the spatial coordinate data of the drill bit based on the spatial coordinates of all the magnetic field generators and their corresponding initial distance values ​​using a spatial geometric analytical algorithm.

[0012] Furthermore, the formula for calculating the initial distance between the drill bit and each of the magnetic field generators is as follows: in, Let be the initial distance between the i-th magnetic field generator and the drill string. Let be the magnetic moment value of the i-th magnetic field generator. Let i be the net magnetic field strength value corresponding to the i-th magnetic field generator, where i = A, B, or C.

[0013] Furthermore, the preset array is arranged in an isosceles triangle configuration; The formula for calculating the spatial coordinate data of the drill bit is: Where b is the length of the base of the isosceles triangle, and h is the distance from the vertex on the perpendicular bisector of the base to the base. These represent the initial distances between the magnetic field generator and the drill bit at the three vertices of the isosceles triangle.

[0014] Accordingly, a second aspect of the present invention provides a control method for a shallow surface drill bit positioning system based on magnetic field strength, which positions the drill bit using the aforementioned shallow surface drill bit positioning system based on magnetic field strength, including the following steps: Configure a magnetic field generator array, which includes several magnetic field generators arranged in a preset array, and set the operating frequency of the several magnetic field generators to different preset frequencies. The magnetic field signal of each magnetic field generator is acquired by a magnetic sensor installed on the drill bit; Based on the acquired magnetic field signals, the initial distance between each magnetic field generator and the drill bit is calculated. By combining all the calculated initial distance values ​​and the spatial coordinates of the magnetic field generator, the spatial coordinate data of the drill bit are calculated.

[0015] The above-described technical solutions of the embodiments of the present invention have the following beneficial technical effects: 1. The symmetrical array deployed on the ground (above or below ground) provides superior geometric constraints for spatial calculation. The independent and non-overlapping operating frequencies of each generator, combined with its alternating power-on strategy and differential and adaptive filtering for the background magnetic field, can effectively remove inherent magnetic field noise and transient electromagnetic interference in the environment. This allows for the extraction of stable, pure, and effective magnetic field signals in complex on-site electromagnetic environments, laying a solid foundation for subsequent accurate positioning. 2. First, based on the near-field magnetic positioning model, the initial distance between the drill string and each generator is quickly calculated using the net magnetic field strength. Then, through a clever geometric analytical method, the initial value of the drill string's spatial coordinates is obtained by eliminating variables using the symmetry of the array. This initial value has a small computational load and provides a high-quality starting point for subsequent iterations. Finally, the Gauss-Newton iteration method based on the Jacobian matrix is ​​introduced to optimize this initial value, and the reliability of different measurement values ​​is taken into account by using a weighted matrix. Thus, while ensuring computational efficiency, the accuracy and stability of the final positioning results are significantly improved. 3. Not only does it output the optimal position estimate of the drilling tool, but it also calculates the error ellipsoid and confidence score of the position through sensitivity analysis, thereby quantitatively evaluating the quality of each positioning result. The information is pushed to the construction control system in real time, enabling operators to intuitively judge the reliability of the positioning and take remedial measures such as adjusting the generator power in time when the confidence score is low or the error ellipsoid is too large. Ultimately, it achieves real-time and accurate correction of the drilling trajectory, ensuring the high-quality completion of the project. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the principle of the shallow surface drill positioning system based on magnetic field strength provided in an embodiment of the present invention; Figure 2 This is a flowchart of the shallow surface drill positioning system based on magnetic field strength provided in an embodiment of the present invention; Figure 3 This is a flowchart of the control method for a shallow surface drilling tool positioning system based on magnetic field strength provided in an embodiment of the present invention.

[0017] Figure label: 100. Magnetic field generator; 200. Magnetic sensor; 300. Information processing module. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0019] Please refer to Figure 1A first aspect of this invention provides a shallow surface drill bit positioning system based on magnetic field strength, comprising: a magnetic field generator array, a magnetic sensor 200 disposed on the drill bit, and an information processing module 300. The magnetic field generator array is located at a corresponding position relative to the real-time position of the drill bit. The magnetic field generator array includes a plurality of magnetic field generators 100 arranged in a preset array, each operating at a different preset frequency. The magnetic sensor 200 acquires the magnetic field signal of each magnetic field generator 100 and sends it to the information processing module 300. The information processing module 300 calculates the initial distance value between each magnetic field generator 100 and the drill bit based on the plurality of magnetic field signals, and calculates the spatial coordinate data of the drill bit by combining the plurality of initial distance values.

[0020] The shallow surface drilling tool positioning system based on magnetic field strength provided in this invention constructs an active positioning architecture in which a ground-based transmitter and a drilling tool moving end work together. A magnetic field generator array, serving as the system's spatial reference, is deployed on the ground surface corresponding to the drilling tool's real-time activity area. Several magnetic field generators 100 within the array are arranged according to a pre-designed spatial configuration to ensure effective geometric constraints on the underground drilling tool from different directions. Each magnetic field generator 100 is assigned a unique pre-designed operating frequency; these frequencies are independent and non-overlapping, ensuring that even when operating simultaneously, the emitted magnetic field signals are separable in the frequency domain. A magnetic sensor 200 mounted on the drilling tool is responsible for collecting the composite magnetic field signal generated by the combined action of all magnetic field generators 100 at its location. Subsequently, these raw magnetic field signals are sent to the information processing module 300. The module first demodulates and separates the independent signal components corresponding to each magnetic field generator 100 from the composite signal according to the specific frequency of each generator. Then, based on these separated magnetic field intensity components, the module calculates the initial distance values ​​between the drill string and each magnetic field generator 100 using a physical model of near-field magnetic positioning. Finally, the information processing module 300 treats these initial distance values ​​as a series of virtual spheres with the positions of each magnetic field generator 100 as the centers and the distance values ​​as the radii. Using the principles of spatial geometry, the module solves for the intersection points of these spheres, thereby retrieving the precise three-dimensional spatial coordinate data of the drill string at the current moment.

[0021] This system, by deploying a multi-frequency dedicated magnetic field generator array and coordinating magnetic sensing and intelligent calculation at the drill bit end, successfully overcomes the problem of accumulated errors in traditional inertial navigation, eliminates the dependence of laser positioning on strict line-of-sight, and significantly improves the anti-interference capability and measurement reliability of traditional magnetic positioning technology in complex electromagnetic environments. Thus, it can achieve stable and high-precision real-time positioning of the drill bit position under various adverse conditions faced by shallow surface drilling, providing a reliable technical guarantee for precise guidance construction.

[0022] Furthermore, the preset array is a symmetrical arrangement with spatial constraints.

[0023] This "symmetrical arrangement" means that the several magnetic field generators 100 in the array are not arranged randomly or linearly, but according to specific geometric rules, giving them characteristics such as rotational symmetry or mirror symmetry in their spatial structure. This symmetrical configuration, such as the common isosceles or equilateral triangles deployed on the ground, aims to establish a highly deterministic and strongly constrained spatial reference frame for subsequent position calculations. As the drill bit moves underground, its distance relationship with each generator in the array changes with its position. This symmetrical structure ensures effective and balanced geometric constraints on the drill bit's position from different directions, thereby greatly reducing the ambiguity and multiple solutions that may occur during position calculations.

[0024] The symmetrical configuration provides optimal geometric constraints for spatial positioning calculations, making the distance-based position calculation process mathematically more rigorous and deterministic. This effectively avoids problems such as fuzzy calculations, numerical instability, and even jumps in positioning results that are prone to occur in asymmetrical or weakly constrained layouts. This not only directly improves the accuracy and reliability of drill bit positioning results but also enhances the robustness of the entire system in the face of measurement noise and minor disturbances.

[0025] Optionally, the preset array is an isosceles triangle or equilateral triangle arrangement based on the ground plane or the plane corresponding to the first preset depth below the ground. The magnetic field generator array includes three magnetic field generators 100, which are respectively set at the vertices of the triangle.

[0026] The preferred implementation of the preset array is to use isosceles or equilateral triangles arranged based on the ground plane or a plane corresponding to a first preset depth below the ground. The magnetic field generator array includes three magnetic field generators 100, each precisely fixed to one of the three vertices of the triangle. The isosceles triangle layout provides spatial symmetry about the perpendicular bisector, while the equilateral triangle goes further, achieving perfect isotropy, meaning that the constraint from the center to each vertex is completely uniform in the horizontal plane. Arranging these three generators on the same plane (on the ground surface or shallowly buried underground) establishes a stable and known two-dimensional reference plane. These three vertices form a non-collinear reference frame in space, and their precise coordinate relationship provides the most basic and necessary geometric constraints for the subsequent three-dimensional spatial calculations performed by the information processing module 300. Once the information processing module 300 calculates the initial distance values ​​between the drill bit and these three vertices, these three distance values ​​geometrically represent the radii of the three spheres. The intersection of these three spheres will ideally converge to one or two finite spatial points. Combined with the prior knowledge that the drill bit must be located below the surface, the spatial position of the drill bit can be uniquely determined, thereby converting the distance measurement values ​​into precise spatial coordinate data.

[0027] Optionally, the preset array is a spatial arrangement of a three-dimensional triangle or a regular tetrahedron. The magnetic field generator array includes at least four magnetic field generators 100, which are respectively located at the vertices of the three-dimensional triangle or the regular tetrahedron. At least one magnetic field generator 100 is located at a second preset depth below the ground, and the remaining magnetic field generators 100 are located on the ground.

[0028] The preferred implementation of the preset array is a spatially arranged three-dimensional triangular or tetrahedral layout. In this configuration, the magnetic field generator array includes at least four magnetic field generators 100, which are no longer confined to the same plane but are arranged at the vertices forming the geometric structure of the three-dimensional triangle or tetrahedron. This layout requires at least one magnetic field generator 100 to be located at a second preset depth below the ground surface, while the remaining generators are deployed on the ground surface. This hybrid "surface-underground" layout essentially constructs a non-coplanar, three-dimensional reference frame with a specific volume in space. When the surface magnetic field generators 100 and the underground magnetic field generators 100 work together, they apply magnetic field excitation to the underground drilling tool from different heights and directions. This layout greatly enhances the system's spatial constraint and observability in the vertical direction (i.e., the depth direction), enabling the information processing module 300 to obtain measurement information from different elevations when calculating the spatial coordinates of the drill bit. This effectively elevates the positioning model from a two-dimensional plane to a full three-dimensional space, providing geometric conditions that traditional planar arrays do not possess for retrieving the precise vertical position of the drill bit.

[0029] Furthermore, when all magnetic field generators 100 in the magnetic field generator array are simultaneously turned off, the information processing module 300 collects the background environmental magnetic field information of the drilling tool through the magnetic sensor 200 and records the background magnetic field spectrum, which includes the background magnetic field intensity at each preset frequency. When the magnetic field generators 100 in the magnetic field generator array are turned on, the information processing module 300 collects the magnetic field signal of each magnetic field generator 100 through the magnetic sensor 200. Based on the background magnetic field spectrum, the information processing module 300 performs background magnetic field differential processing on each magnetic field signal to obtain the net magnetic field intensity of each magnetic field generator 100. The net magnetic field intensity is the value of the magnetic field signal at the corresponding preset frequency minus the value of the background magnetic field spectrum at the same frequency.

[0030] In this embodiment of the invention, the information processing module 300 executes a sophisticated background magnetic field identification and elimination process to ensure the purity of the effective signal. Specifically, before the system begins positioning, all generators in the magnetic field generator array are simultaneously turned off. In this state, various background magnetic noises (such as geomagnetic fields, industrial stray magnetic fields, etc.) present in the actual working environment of the drilling tool are completely collected by the magnetic sensor 200. The information processing module 300 records the background environmental magnetic field information at this time and analyzes and generates a background magnetic field spectrum. This spectrum accurately records the background magnetic field intensity at a specific preset frequency point of each magnetic field generator 100 that will be used subsequently, which is equivalent to drawing a detailed "environmental electromagnetic noise map". Subsequently, when the magnetic field generators 100 are turned on in sequence and emit excitation signals of their respective frequencies, what the magnetic sensor 200 collects is no longer a pure effective signal, but a mixture of effective signal and background noise. At this time, the information processing module 300 uses background differential processing technology to accurately subtract the pre-recorded background magnetic field intensity at the same frequency from the total intensity of the mixed signal for each frequency corresponding to the magnetic field generator 100, thereby extracting the net magnetic field intensity generated purely by the target generator.

[0031] By implementing the above-mentioned active background magnetic field measurement and differential processing, this system fundamentally improves the signal anti-interference capability in complex electromagnetic environments. It can dynamically identify and eliminate inherent and time-varying background magnetic field interference in the environment, ensuring that the magnetic field strength data used for subsequent distance calculation and position calculation is a "clean" signal that truly reflects the spatial relationship between the generator and the drill string. This greatly reduces the adverse effects of environmental noise on positioning accuracy and provides crucial data quality assurance for obtaining stable, reliable, and high-precision positioning results throughout the drilling operation.

[0032] Furthermore, the information processing module 300 also performs adaptive filtering on the net magnetic field strength of each magnetic field generator 100. By calculating the mean and variance of the net magnetic field strength, the filtering parameters are adjusted in real time according to the changes in the net magnetic field strength to track the low-frequency disturbances introduced by the slow drift of the underground magnetic field in the area where the drilling tool is located, and to suppress the narrowband interference introduced by environmental electromagnetic interference.

[0033] After completing the differential processing of the background magnetic field, the information processing module 300 further performs adaptive filtering on the net magnetic field strength corresponding to each magnetic field generator 100 to improve signal quality. Unlike traditional fixed-parameter filtering methods, this adaptive filtering can dynamically respond to changes in the actual working environment. The information processing module 300 calculates and analyzes the statistical characteristics (such as mean and variance) of each net magnetic field strength signal in real time, and adjusts its internal filtering parameters autonomously and continuously based on this. This dynamic adjustment mechanism gives it two key capabilities: first, it can actively track and compensate for the slow drift of the background magnetic field caused by the drilling tool moving to different formations, which is a low-frequency and time-varying change; second, it can specifically suppress narrowband interference introduced by sudden or intermittent electromagnetic interference sources in the environment, which usually have specific frequency characteristics. The entire filtering process is a closed-loop self-optimizing system. Its filtering characteristics are not fixed in advance, but are shaped in real time and in a targeted manner according to the characteristics of the input signal, thereby ensuring that the output signal quality remains optimal.

[0034] The filtering parameters (such as cutoff frequency, bandwidth, attenuation coefficient, etc.) are not fixed in advance, but are a dynamic response system. By continuously calculating the statistical characteristics of the net magnetic field strength (such as mean and variance), it senses changes in signal characteristics and environmental interference in real time and adjusts the above parameters accordingly. This dynamic self-adjustment mechanism enables it to intelligently widen or narrow the filter passband, effectively tracking and compensating for the slow drift of the background magnetic field caused by geological differences, and accurately suppressing sudden electromagnetic interference at specific frequencies. Thus, it maintains optimal filtering performance under various time-varying conditions, ensuring the purity and stability of the output signal.

[0035] Furthermore, the information processing module 300 calculates the initial distance between the drill string and each magnetic field generator 100 based on the net magnetic field strength of each magnetic field generator 100 using a near-field magnetic positioning model; the information processing module 300 calculates the spatial coordinate data of the drill string based on the spatial coordinates of all magnetic field generators 100 and their corresponding initial distance values ​​using a spatial geometric analytical algorithm.

[0036] After obtaining the net magnetic field strength after background subtraction and adaptive filtering, the information processing module 300 enters the core position calculation stage. First, based on the physical model of near-field magnetic positioning, each magnetic field generator 100 is considered as a magnetic dipole source. According to the principle that there is a definite mathematical relationship between the magnetic field strength and propagation distance of a source with a known magnetic moment in the near-field region, the module uses the net magnetic field strength value corresponding to each generator to calculate the initial distance between the drill string and each generator. This step transforms the magnetic field strength information, which is difficult to use directly, into a more intuitive physical quantity that is more conducive to spatial geometric calculations. Subsequently, the information processing module 300 enters the spatial positioning stage, combining the known, precisely measured spatial coordinates of all magnetic field generators 100 with the corresponding initial distance values ​​just calculated. Each "generator coordinate - initial distance" pair geometrically defines a sphere with the generator position as the center and the initial distance as the radius. The module uses a spatial geometric analytical algorithm to solve for the intersection points of these spheres in three-dimensional space. Since the array layout ensures spatial constraints, these spheres usually intersect in a finite region. The center of this region or the optimal estimated point is determined as the current spatial coordinate data of the drill bit, thus completing the final conversion from magnetic field signal to three-dimensional position.

[0037] Specifically, the formula for calculating the initial distance between the drill string and each magnetic field generator 100 is as follows: in, Let be the initial distance between the i-th magnetic field generator 100 and the drill string. Let be the magnetic moment value of the i-th magnetic field generator 100. Let i be the net magnetic field strength value corresponding to the i-th magnetic field generator 100, where i = A, B, or C.

[0038] After obtaining the pre-processed net magnetic field strength, the information processing module 300 converts the magnetic field strength into a spatial distance based on near-field magnetic positioning theory. The physical model underlying this conversion treats each magnetic field generator 100 as an equivalent magnetic dipole with a known magnetic moment. In the near-field region, the magnetic field strength at a point in space is inversely proportional to the cube of the distance from that point to the dipole. Based on this established physical law, the information processing module 300 uses pre-calibrated and stored magnetic moment values ​​of each generator, combined with the corresponding real-time measured net magnetic field strength values, to directly calculate the initial distance between the drill string and each magnetic field generator 100 by dividing the magnetic moment by the strength and introducing a proportionality coefficient. This calculation process has clear physical meaning and a definite mathematical relationship, transforming the abstract magnetic field sensing quantity into an intuitive spatial distance quantity that is easy to solve geometrically subsequently.

[0039] Specifically, the preset array is arranged in an isosceles triangle pattern; The formula for calculating the spatial coordinate data of the drill string is: Where b is the length of the base of the isosceles triangle, and h is the distance from the vertex on the perpendicular bisector of the base to the base. These represent the initial distances between the magnetic field generator 100 at the three vertices of the isosceles triangle and the drill bit.

[0040] When the preset array is arranged in an isosceles triangle, the information processing module 300 utilizes the symmetry inherent in this specific geometric configuration to efficiently calculate the spatial coordinates of the drill bit using a spatial analytical method. This method first incorporates the known positions of the three magnetic field generators 100 and the three measured initial distance values ​​into a unified coordinate system, with the base length and the height of the perpendicular bisector serving as key geometric parameters. By subtracting the distance equations pairwise, the system cleverly eliminates higher-order terms of the unknowns, thereby transforming the nonlinear distance equations into a linear system. This transformation allows the system to directly analyze the initial horizontal coordinates of the drill bit. Specifically, the lateral position of the drill bit is determined by the squared difference of the distances measured by the generators at both ends of the base, while its longitudinal position is calculated by incorporating the distance information from the vertex generator and combining it with the characteristics of the perpendicular bisector. After determining the horizontal coordinates, the system selects any generator position, substitutes the distance equations back to solve for the depth coordinates of the drill bit, and, based on the physical fact that the drill bit is located below the surface, selects a reasonable negative solution from the mathematical solutions, thereby efficiently obtaining a complete initial estimate of the spatial coordinates.

[0041] By employing the aforementioned spatial analytical algorithm based on the symmetry of isosceles triangles, the system achieves efficient and stable calculation of the initial value of the drill bit position. This method transforms the complex nonlinear positioning problem into a linear problem that can be solved analytically. This not only significantly reduces computational complexity and improves real-time performance, but more importantly, its solution process completely avoids the convergence instability problems that may occur in iterative algorithms. It provides high-quality and reliable initial values ​​for subsequent possible optimization iterations, thereby ensuring the robustness and computational efficiency of the positioning system as a whole.

[0042] Below, as Figure 1 and Figure 2 As shown, the principle of this system will be further explained through a specific embodiment: (I) Establishing the Array and Geometric Model of the Ground Magnetic Field Generator A magnetic field generator array ABC is deployed on the ground, arranged in an isosceles triangle, and the three magnetic field generators are numbered as follows: The geometric layout exhibits high spatial symmetry, laying the foundation for subsequent precise positioning calculations.

[0043] Three magnetic field generators 100 operating frequency Independently configured and non-overlapping, these transmitters can transmit simultaneously while maintaining a certain frequency interval. In shallow drilling with relatively uniform geological conditions, a higher frequency can be appropriately selected. If there are interference sources nearby, such as high-voltage transmission lines, the main interference frequency band should be avoided, and a less interfering frequency band should be selected to improve anti-interference capability. Simultaneously, the transmission frequency must possess high stability to ensure signal accuracy and consistency. This frequency configuration helps avoid mutual interference between different magnetic field generators 100, ensuring that each transmitted signal can be accurately distinguished and analyzed by the triaxial magnetometer.

[0044] Let the positions of the three magnetic field generators 100 be respectively , , Let plane ABC be Let the length of the base AC be... The vertex B is located on the perpendicular bisector of AC, and the perpendicular distance from B to line AC is... Establish a coordinate system with the midpoint of AC as the origin. Define the x-axis along the AC direction, pointing positively to C; define the y-axis as the perpendicular bisector of AC passing through the origin, pointing positively to B; and define the z-axis as the positive direction perpendicular to the ground upwards. Therefore... , , , serving as the benchmark framework for positioning.

[0045] Theoretically, increasing the number of magnetic field generators 100 can provide more measurement information and enhance fault tolerance; however, this invention preferably uses a "three-unit isosceles triangle" scheme, which satisfies the need for sufficient triangulation positioning information while avoiding the computational and deployment costs caused by redundancy, thus balancing accuracy and economy. Other optional schemes include: ① Arranging the three magnetic field generators 100 in an equilateral triangle (with equal distances between each pair) can obtain more uniform spatial constraints for isotropic geological environments, potentially further simplifying the calculation and improving accuracy; ② Placing one or two of the magnetic field generators 100 underground to enhance vertical observability and bring them closer to the working stratum, reducing errors introduced by surface-to-subsurface differences; ③ When extremely high 3D positioning accuracy is required, a tetrahedral arrangement can be used, preferably with two units placed underground, to obtain more comprehensive and uniform 3D magnetic field coverage, suitable for deep drilling or precise 3D positioning scenarios.

[0046] (II) Background Environmental Magnetic Field Differential and Filtering Process A magnetic sensor 200 is installed on the drill bit side of the drilling tool. As the drill bit is a critical part of the drilling tool that directly contacts the underground medium, installing a triaxial magnetic sensor here maximizes the accuracy and timeliness of the magnetic field signals acquired by the sensor. This sensor can receive magnetic field signals generated by multiple magnetic field generators 100 on the ground, and possesses high sensitivity and strong anti-interference capabilities.

[0047] When the magnetic field generator 100 is not powered on, the magnetic sensor 200 records the background magnetic field spectrum. The system identifies and records the main noise frequency bands in the environment. The information processing module 300 acquires the background magnetic field signal data recorded by the magnetic sensor 200, stores and performs preliminary analysis on it for subsequent signal extraction and correction.

[0048] After that, the three ground-based magnetic field generators 100 Each magnetic field generator 100 alternately enters the energizing state in a specific sequence at its own non-overlapping operating frequencies. When a magnetic field generator 100 is energized, the magnetic sensor 200 on the drill bit transmits the received magnetic field signal containing information about that magnetic field generator 100 to the information processing module 300. The information processing module 300 uses frequency demodulation technology to extract the magnetic field generator 100 from the mixed signal. Corresponding magnetic field strength .

[0049] Next, the information processing module 300 removes the influence of the background magnetic field using a background difference formula: Finally, information processing module 300 pairs Adaptive filtering is performed. The adaptive filter automatically adjusts its coefficients by tracking changes in the background magnetic field in real time, thus better suppressing background noise and interference signals. After adaptive filtering, the information processing module 300 outputs three magnetic field generators 100. net magnetic field strength , , .

[0050] (iii) Calculate the distance information between the drilling tool and the magnetic field generator 100. Information processing module 300, based on the Biot-Savart law and the equivalent magnetic dipole propagation model, calculates the relationship between the drilling tool and each magnetic field generator 100. The approximate distance between them.

[0051] The Biot-Savart law describes the magnetic field generated by a current element at a point in space. In a drill bit positioning system, considering the propagation characteristics of shallow surface environments, an equivalent magnetic dipole model is constructed for approximate distance estimation. In the model, the magnetic moment... and net magnetic field strength Magnetic moment is a key parameter for calculating distance. This is an inherent physical quantity of the magnetic field generator 100, characterizing the magnitude of the magnetic field generated by the generator 100, and is known during the system design and debugging phases. Net magnetic field strength The magnetic field data is obtained from three magnetic field generators 100 after being processed by the information processing module 300 through the magnetic sensor 200 installed at the drill bit. net magnetic field strength , , .

[0052] Based on the above principles and measurement data, the approximate distance can be calculated using the following formula: Thus, the drilling tool and magnetic field generator 100 are obtained. Rough distance between , , .

[0053] (iv) Establish the azimuth measurement equations for the drilling tool and the magnetic field generator 100. After obtaining the approximate distance between the drill string and each magnetic field generator 100 , , Next, the precise position of the drill bit is determined. Let the unknown position of the drill bit be... This refers to the precise position of the drill bit in three-dimensional space.

[0054] Considering that the distance measured in reality is not the true distance, but a measurement value containing noise, we define a distance measurement model (with noise): in, To represent the drill string position determined based on spatial geometric relationships The actual distance between the magnetic field generator 100 and the magnetic field generator 100. To account for noise, a residual function is introduced to measure the degree of deviation between the measured distance and the true distance: The residual function, by calculating the difference between the true distance and the actual measured distance based on spatial geometric relationships, can intuitively reflect the deviation of each measurement from the actual situation. Based on this, optimization algorithms can be used for iterative updates. This reduces residuals and provides a more accurate estimate of drill string position.

[0055] (v) Establish the objective function for drill string positioning optimization To obtain the optimal estimate of the drill string position, a weighted least squares objective function is constructed and minimized: in The optimal estimate of the drill string's position is the coordinate point found by the optimization algorithm that is closest to the actual position of the drill string.

[0056] objective function The expression is: By minimizing the objective function , to obtain Take the minimum value That is, the optimal estimate of the drill string position after considering measurement noise and the weights of each measurement.

[0057] (vi) Geometric analytical method for determining the initial value of the drill string position After establishing the objective function for drill string positioning optimization, in order to improve the solution efficiency, the information processing module 300 uses a geometric analytical method to obtain the initial value of the target point position. Because the drilling tool is located underground ( ), and the solution in the negative half space is selected as the initial value.

[0058] When noise is ignored, the true distance satisfies: Bundle Squaring both sides simultaneously, we get: right and subtract and eliminate have to: Multiplying both sides by -1 and simplifying, we get the linear constraint: for and The same logic applies to subtraction, resulting in: Substitution , , For both sides of equation AB: thereby: Similarly, for equation AC, since point AC is symmetrical, the condition can be eliminated. Item, we get: It can be calculated that: Bundle Substituting back into equation AB, we can obtain... : Take any point (such as A), and use back substitution to find... : Because the drilling tool is underground ( ),so Take the negative root to obtain the initial value. This initial value can serve as the starting point for subsequent iterative optimizations, helping to improve convergence speed and solution efficiency.

[0059] (vii) Iterative optimization of drill string positioning results based on Jacobian matrix Based on the existing distance model and residual vector, the information processing module 300 introduces the Jacobian matrix and employs the Gauss-Newton iterative method to continuously optimize the drill string position estimation. The Gauss-Newton method is suitable for nonlinear least squares problems based on distance observations, exhibiting fast local convergence characteristics, and is particularly effective in scenarios with small errors.

[0060] The distance model is: This formula is used to accurately describe the position of the drill string. Position of magnetic field generator 100 .

[0061] Based on this distance formula, define the residual vector: It intuitively reflects the difference between the distance calculated based on the current estimated location and the actual measured distance.

[0062] To further improve measurement accuracy, the Jacobian matrix of the residuals with respect to the unknowns is calculated: The Jacobian matrix reflects the rate at which the residual vector changes with the drill string position, and it plays a crucial role in subsequent iterative optimization. The three measurement matrices are stacked to obtain: Using the Gauss-Newton iteration formula: in It is a weighted matrix, usually a diagonal matrix, containing the weights of each measurement. , It is the current The estimated residual vector.

[0063] In each iteration, the drill string position is first estimated based on the current position. Calculate the Jacobian matrix and residual vector Then combine with the weighted matrix Through formula Calculate the position adjustment amount. Apply this adjustment amount from the current position. Subtracting from the middle, we get the new estimated position. As the iteration proceeds, the residual vector... The difference between the estimated and actual positions will gradually decrease, meaning the difference between the estimated and actual positions will continuously shrink, thus making the estimated position of the drill bit closer and closer to the true value.

[0064] (viii) Results Output and Sensitivity Analysis When the iteration converges, the information processing module 300 obtains the optimal estimate of the drill string position. Sensitivity analysis was used to assess positioning accuracy and provide a basis for trajectory correction. At the convergence point, to reflect the distribution of drill string position estimation errors in various directions due to factors such as measurement noise and the approximation of the model itself, the positioning error covariance is approximately calculated based on Fisher information: From the error covariance matrix Taking the square root of the diagonal element yields... These three values ​​represent respectively in , , Standard deviation of the estimation error in direction. These standard deviations visually demonstrate the degree of uncertainty in the drill string's position across various dimensions.

[0065] Based on these standard deviations, a 95% error ellipsoid is further generated. The error ellipsoid is centered on the estimated position of the drill string, and its shape and size are determined by… The decision is made. At a 95% confidence level, the actual drill string location will most likely fall within this error ellipsoid.

[0066] Optimal position estimation The 95% error ellipsoid information and confidence score are pushed to the construction control system along with the location. Construction personnel can use this information to correct the trajectory. If a low confidence score or a large error ellipsoid is found, it indicates low positioning reliability or a large error, possibly suggesting a weak signal or excessive interference. In this case, construction personnel can use this information to determine whether measures need to be taken to enhance the signal and reduce interference, such as adjusting the power of the magnetic field generator 100, changing the position of the magnetic sensor 200, or adding filtering measures. Then, the positioning calculation is recalculated to ensure that the drill bit follows the predetermined high-precision trajectory.

[0067] Accordingly, please refer to Figure 3The second aspect of this invention provides a control method for a shallow surface drill bit positioning system based on magnetic field strength. The method for positioning the drill bit using the aforementioned shallow surface drill bit positioning system based on magnetic field strength includes the following steps: Step S100: Configure the magnetic field generator array to include a plurality of magnetic field generators 100 arranged in a preset array, and set the operating frequency of the plurality of magnetic field generators 100 to a different preset frequency.

[0068] In practice, the first step is to plan and deploy a magnetic field generator array on the surface (or near the surface) of the expected drilling area based on the drilling project's design trajectory and geological survey data. The array configuration requires careful design, typically employing a symmetrical layout with spatial constraints, such as precisely fixing three magnetic field generators 100 at the three vertices of an isosceles triangle. More importantly, during the power-on initialization phase, each magnetic field generator 100 in the array must be independently frequency-configured, assigning it a preset, non-overlapping specific operating frequency. This frequency configuration process is usually completed on the system controller, through software settings or hardware DIP switches, ensuring that the transmitted signals of each generator can be clearly distinguished in the frequency domain. This step establishes a unique and known spatial reference base and separable signal sources for the entire positioning system.

[0069] In step S200, the magnetic field signal of each magnetic field generator 100 is acquired by the magnetic sensor 200 installed on the drill bit.

[0070] Once drilling begins and the drill string enters the ground, the magnetic sensor 200, positioned at or near the drill bit, operates continuously. As a highly sensitive magnetic field receiver, it senses the synthetic magnetic field environment at its location in real time. This synthetic magnetic field consists of three main parts: effective signals with specific frequencies emitted by the magnetic field generators 100 in the ground array; broad-spectrum background electromagnetic noise from the surrounding environment; and transient strong interference that may be introduced by industrial equipment, etc. The magnetic sensor 200 detects these continuously varying analog magnetic field signals over time, typically converting them from analog to digital signals to form a digital sequence, which is then packaged and sent to the information processing module 300. This step ensures the acquisition of raw data containing information about the spatial relationships between the drill string and the generators.

[0071] After acquiring the raw magnetic field signal, the information processing module 300 performs a series of sophisticated preprocessing operations to extract useful information. A key preprocessing step is background magnetic field differential processing: the system first shuts down all magnetic field generators 100, and the magnetic sensor 200 measures and records the magnetic field spectrum under pure background conditions as a background noise reference. Subsequently, when the magnetic field generators 100 are operating normally, for each frequency point, the pre-recorded background value of the corresponding frequency is subtracted from the measured total magnetic field strength to obtain the net magnetic field strength generated purely by the target generator. In addition, adaptive filtering technology can be used to dynamically adjust the filtering parameters according to the signal statistical characteristics, further suppressing narrowband interference and tracking slowly drifting low-frequency noise, ensuring the purity and reliability of the signal used in subsequent processing.

[0072] Step S300: Based on the acquired magnetic field signals, calculate the initial distance between each magnetic field generator 100 and the drill bit.

[0073] After obtaining the pre-processed net magnetic field strength values ​​corresponding to each generator, the information processing module 300 performs distance conversion based on the physical model of near-field magnetic positioning. This model, based on the Biot-Savart law and magnetic dipole theory, establishes that in the near-field region, the magnetic field strength at a point in space is inversely proportional to the cube of its distance from the magnetic source. Specifically, for each magnetic field generator 100, the information processing module 300 uses its known magnetic moment value, determined during the system calibration phase, combined with the corresponding net magnetic field strength value obtained in step S200, and calculates the initial distance between the drill string and the generator using the mathematical relationship determined by the physical model. This step transforms the abstract magnetic field sensing quantity into concrete distance information with clear geometric meaning, providing direct input parameters for spatial positioning.

[0074] Step S400: Combine all the calculated initial distance values ​​and the spatial coordinates of the magnetic field generator 100 to calculate the spatial coordinate data of the drill bit.

[0075] The information processing module 300 has now acquired two key sets of information: first, the precise spatial coordinates of all magnetic field generators 100 in a pre-established coordinate system; and second, the initial distance values ​​between the drill string and each generator, calculated through step S300. The core of the positioning calculation lies in solving a geometric problem: finding a point (drill string position) in three-dimensional space such that its distance to multiple known points (generator positions) is equal to or closest to the measured distance value. The system first employs an efficient geometric analytical method, utilizing the symmetry of the array (such as an isosceles triangle layout) to quickly obtain the initial estimate of the drill string's spatial coordinates. Subsequently, an iterative optimization algorithm (such as the Gauss-Newton method) is typically introduced. Starting from this initial value, an objective function is constructed, and the Jacobian matrix is ​​calculated. Through multiple iterations, the position estimate is continuously corrected, minimizing the residual between the calculated distance and the actual measured distance, ultimately outputting high-precision spatial coordinate data of the drill string at the current moment. Furthermore, the system can perform sensitivity analysis to evaluate the confidence level and error range of the positioning result, providing a more comprehensive basis for trajectory correction decisions.

[0076] Through the four steps described above, the control method constructs a complete and robust shallow surface drill bit positioning method. From the symmetrical layout and frequency planning of the system hardware, to the real-time acquisition and purification of magnetic field signals during drilling, to the reliable distance conversion based on the physical model, and finally to the accurate calculation of spatial coordinates through rigorous geometric analysis and optimization algorithms, the entire process is logically clear and interconnected. This method effectively overcomes the inherent defects of traditional technologies, such as cumulative errors, line-of-sight dependence, and susceptibility to complex electromagnetic interference. It can stably and efficiently output real-time high-precision position information of the drill bit under harsh working conditions of non-line-of-sight and strong interference underground, providing key technical support for precision-guided drilling operations.

[0077] The embodiments of the present invention aim to protect a shallow surface drill positioning system and its control method based on magnetic field strength, which has the following effects: 1. The symmetrical array deployed on the ground (above or below ground) provides superior geometric constraints for spatial calculation. The independent and non-overlapping operating frequencies of each generator, combined with its alternating power-on strategy and differential and adaptive filtering for the background magnetic field, can effectively remove inherent magnetic field noise and transient electromagnetic interference in the environment. This allows for the extraction of stable, pure, and effective magnetic field signals in complex on-site electromagnetic environments, laying a solid foundation for subsequent accurate positioning. 2. First, based on the near-field magnetic positioning model, the initial distance between the drill string and each generator is quickly calculated using the net magnetic field strength. Then, through a clever geometric analytical method, the initial value of the drill string's spatial coordinates is obtained by eliminating variables using the symmetry of the array. This initial value has a small computational load and provides a high-quality starting point for subsequent iterations. Finally, the Gauss-Newton iteration method based on the Jacobian matrix is ​​introduced to optimize this initial value, and the reliability of different measurement values ​​is taken into account by using a weighted matrix. Thus, while ensuring computational efficiency, the accuracy and stability of the final positioning results are significantly improved. 3. Not only does it output the optimal position estimate of the drilling tool, but it also calculates the error ellipsoid and confidence score of the position through sensitivity analysis, thereby quantitatively evaluating the quality of each positioning result. The information is pushed to the construction control system in real time, enabling operators to intuitively judge the reliability of the positioning and take remedial measures such as adjusting the generator power in time when the confidence score is low or the error ellipsoid is too large. Ultimately, it achieves real-time and accurate correction of the drilling trajectory, ensuring the high-quality completion of the project.

[0078] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0079] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0080] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0081] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A shallow surface drill bit positioning system based on magnetic field strength, characterized in that, include: Magnetic field generator array, magnetic sensor (200) mounted on the drill bit, and information processing module (300). The magnetic field generator array is located at the corresponding position of the real-time position of the drill bit. The magnetic field generator array includes a plurality of magnetic field generators (100) arranged in a preset array. The operating frequencies of the plurality of magnetic field generators (100) are all different preset frequencies. The magnetic sensor (200) acquires the magnetic field signal of each of the magnetic field generators (100) and sends it to the information processing module (300). The information processing module (300) calculates the initial distance value between each magnetic field generator (100) and the drill bit based on several magnetic field signals, and calculates the spatial coordinate data of the drill bit by combining several initial distance values.

2. The shallow surface drill positioning system based on magnetic field strength according to claim 1, characterized in that, The preset array is a symmetrical arrangement with spatial constraints.

3. The shallow surface drill positioning system based on magnetic field strength according to claim 2, characterized in that, The preset array is an isosceles triangle or equilateral triangle arrangement based on the ground plane or the plane corresponding to the first preset depth below the ground. The magnetic field generator array includes three magnetic field generators (100), and the three magnetic field generators (100) are respectively arranged at the vertices of the triangle.

4. The shallow surface drilling tool positioning system based on magnetic field strength according to claim 2, characterized in that, The preset array is a spatial arrangement of a three-dimensional triangle or a regular tetrahedron. The magnetic field generator array includes at least four magnetic field generators (100). The at least four magnetic field generators (100) are respectively set at the vertices of the three-dimensional triangle or the regular tetrahedron. At least one of the magnetic field generators (100) is set at a second preset depth below the ground, and the remaining magnetic field generators (100) are set on the ground.

5. The shallow surface drill positioning system based on magnetic field strength according to any one of claims 1-4, characterized in that, When all magnetic field generators (100) in the magnetic field generator array are turned off at the same time, the information processing module (300) collects the background environmental magnetic field information of the drill bit through the magnetic sensor (200) and records the background magnetic field spectrum, which includes the background magnetic field intensity at each preset frequency. When the magnetic field generators (100) of the magnetic field generator array are turned on, the information processing module (300) collects the magnetic field signal of each of the magnetic field generators (100) through the magnetic sensor (200); Based on the background magnetic field spectrum, the information processing module (300) performs background magnetic field differential processing on each magnetic field signal to obtain the net magnetic field strength of each magnetic field generator (100). The net magnetic field strength is the value of the magnetic field signal at the corresponding preset frequency minus the value of the background magnetic field spectrum at the same frequency.

6. The shallow surface drilling tool positioning system based on magnetic field strength according to claim 5, characterized in that, The information processing module (300) also performs adaptive filtering on the net magnetic field strength of each of the magnetic field generators (100). By calculating the mean and variance of the net magnetic field strength, the filtering parameters are adjusted in real time according to the changes in the net magnetic field strength to track the low-frequency disturbances introduced by the slow drift of the underground magnetic field in the area where the drilling tool is located, and to suppress the narrowband interference introduced by environmental electromagnetic interference.

7. The shallow surface drilling tool positioning system based on magnetic field strength according to claim 5, characterized in that, The information processing module (300) calculates the initial distance between the drill bit and each of the magnetic field generators (100) based on the net magnetic field strength of each of the magnetic field generators (100) through a near-field magnetic positioning model. The information processing module (300) calculates the spatial coordinate data of the drill bit based on the spatial coordinates of all the magnetic field generators (100) and their corresponding initial distance values ​​through a spatial geometric analysis algorithm.

8. The shallow surface drilling tool positioning system based on magnetic field strength according to claim 7, characterized in that, The formula for calculating the initial distance between the drill string and each of the magnetic field generators (100) is as follows: in, Let be the initial distance between the i-th magnetic field generator (100) and the drill string. Let be the magnetic moment value of the i-th magnetic field generator (100). Let i be the net magnetic field strength value corresponding to the i-th magnetic field generator (100), where i = A, B or C.

9. The shallow surface drilling tool positioning system based on magnetic field strength according to claim 7, characterized in that, The preset array is arranged in an isosceles triangle pattern; The formula for calculating the spatial coordinate data of the drill bit is: Where b is the length of the base of the isosceles triangle, and h is the distance from the vertex on the perpendicular bisector of the base to the base. The values ​​are the initial distances between the magnetic field generator (100) at the three vertices of the isosceles triangle and the drill bit.

10. A control method for a shallow surface drilling tool positioning system based on magnetic field strength, characterized in that, Positioning the drill bit using the shallow surface drill bit positioning system based on magnetic field strength as described in any one of claims 1-9 includes the following steps: Configure a magnetic field generator array to include a plurality of magnetic field generators (100) arranged in a preset array, and set the operating frequencies of the plurality of magnetic field generators (100) to be different preset frequencies. The magnetic field signal of each of the magnetic field generators (100) is acquired by a magnetic sensor (200) installed on the drill bit; Based on the acquired magnetic field signals, the initial distance between each magnetic field generator (100) and the drill bit is calculated; By combining all the calculated initial distance values ​​and the spatial coordinates of the magnetic field generator (100), the spatial coordinate data of the drill bit are calculated.

Images