Method for locating a remote magnetic target and design method thereof

Abstract

The application discloses a kind of positioning of long-distance magnetic target and its design method, belong to the target positioning technical field based on magnetic field.It includes: S100, the position coordinates and magnetic moment of magnetic interference source are inverted using short baseline magnetic detection system, then real-time stripping interference magnetic field generated by magnetic interference source at long baseline magnetic detection system using inversion result, finally realize long-distance magnetic target positioning using long baseline magnetic detection system, obtain the magnetic moment vector m2 of magnetic target;S200, according to actual working condition and detection demand, the design method of each parameter of magnetic detection system is proposed in combination with the magnetic moment vector m2.The application uses short baseline magnetic detection system to real-time strip platform magnetic interference, and realizes long-distance magnetic target positioning using long baseline magnetic detection system.

Description

Technical Field

[0001] This invention relates to a method for locating and designing long-distance magnetic targets, belonging to the field of target positioning technology based on magnetic fields. Background Technology

[0002] Magnetic target localization technology is a non-contact, passive detection method based on magnetic fields. Theoretically, it can detect the presence of any ferromagnetic material on Earth. Compared to other detection methods, magnetic anomaly detection is largely unaffected by natural factors such as weather. Furthermore, water (oceans, rivers, lakes, etc.), air, the human body, and most soil and rocks do not shield the magnetic field. It also boasts advantages such as strong identification capabilities, short operating time, high positioning accuracy, and low cost. Therefore, magnetic target localization technology has wide applications in underwater exploration, biomedicine, archaeological excavation, and mineral exploration.

[0003] Achieving long-range magnetic target localization can effectively improve detection efficiency, thereby enabling magnetic target localization technology to be better applied in various fields. Magnetic target localization techniques for detecting long-range magnetic targets mainly include scalar magnetic target localization and tensor magnetic target localization, but both methods have drawbacks to varying degrees.

[0004] 1. Due to the inability to accurately obtain the geomagnetic tilt and deflection angles, the positioning accuracy of scalar magnetic target positioning technology is limited.

[0005] Given the geomagnetic tilt and declination, and leveraging the near-zero scalar gradient of the geomagnetic field, a nonlinear equation system can be constructed using a scalar magnetic sensor array to accurately determine the magnetic target's coordinates. The geomagnetic tilt and declination need to be calculated using a geomagnetic field model or measured by geomagnetic observatories. However, the fluctuations in the time-varying geomagnetic field are tens of nT on calm days and hundreds of nT on storm days, making it impossible to accurately determine the geomagnetic tilt and declination. Furthermore, the current number of geomagnetic stations worldwide is only around 170, limiting the geographical application of the technology. Therefore, the application of scalar magnetic target positioning technology for detecting distant magnetic targets is limited, and its positioning accuracy is insufficient.

[0006] 2. Tensor magnetic target localization technology has not yet achieved long-distance magnetic target localization.

[0007] The magnetic gradient tensor is the gradient of the magnetic field vector in three spatial directions. Magnetic target localization technology based on the magnetic gradient tensor is called tensor magnetic target localization technology. Since the gradient of the Earth's magnetic field is essentially zero, tensor magnetic localization technology is unaffected by the Earth's magnetic field and its fluctuations. Furthermore, the magnetic gradient tensor provides richer magnetic field information and higher spatial resolution, resulting in higher positioning accuracy and faster detection speed compared to scalar magnetic target localization technology. However, because the magnetic gradient tensor decays faster than the magnetic field scalar, the positioning distance of tensor magnetic target localization technology is generally smaller. The instrument used to measure the magnetic gradient tensor is called a tensor gradiometer, and the distance between adjacent sensors in the gradiometer is defined as the baseline distance. When the relative positioning error (100% × positioning error / positioning distance) is exactly equal to 5%, the positioning distance at this point is called the maximum positioning distance of the magnetic target localization technology. The maximum positioning distance of tensor magnetic target localization technology varies with the baseline distance as follows: Figure 1 As shown, the larger the baseline distance, the farther the positioning distance; that is, to achieve long-distance magnetic target positioning, the baseline distance must be increased. However, for large-volume magnetic detection systems, existing technologies struggle to accurately and in real-time isolate the hard and soft magnetic interference generated by the platform at the magnetic detection system. Therefore, current tensor magnetic target positioning technology has not yet achieved long-distance magnetic target positioning. Summary of the Invention

[0008] This invention proposes a method for locating and designing long-range magnetic targets. It utilizes a short-baseline magnetic detection system to remove platform magnetic interference in real time and a long-baseline magnetic detection system to achieve long-range magnetic target location. This solves the problem that existing tensor magnetic positioning technology requires a long-baseline magnetic detection system to achieve long-range magnetic target location, but for large-volume magnetic detection systems, existing technology has difficulty in accurately and in real time removing hard and soft magnetic interference generated by the platform at the magnetic detection system.

[0009] A method for locating and designing a long-range magnetic target, wherein the design method of the composite magnetic target positioning system includes the following steps:

[0010] S100. The position coordinates and magnetic moment of the magnetic interference source are inverted using a short baseline magnetic detection system. Then, the interference magnetic field generated by the magnetic interference source at the long baseline magnetic detection system is stripped away in real time using the inversion results. Finally, the long baseline magnetic detection system is used to locate the magnetic target at a distance and obtain the magnetic moment vector m2 of the magnetic target.

[0011] S200. Based on the actual working conditions and detection requirements, and in conjunction with the magnetic moment vector m2, a design method for each parameter of the magnetic detection system is proposed.

[0012] Furthermore, S100 specifically includes the following steps:

[0013] S110. Using a short baseline magnetic detection system to retrieve the location coordinates and magnetic moment of the magnetic interference source:

[0014] Measuring the magnetic gradient tensor G using a short baseline magnetic detection system 1 The positioning formula of the tensor magnetic positioning method and the measured G 1 Calculate the position vector r1 = [x1, y1, z1] of the magnetic interference source. T r1 is the magnitude of the position vector r1. After calculating the position vector of the magnetic interference source, the magnetic moment vector m1 is calculated according to equation (1).

[0015] m1=(A T ·A) -1 A T ·G 1 (1)

[0016] In the formula:

[0017]

[0018] S120. Calculate the magnetic field generated by the magnetic interference source at the long baseline magnetic detection system. When the detection distance is greater than 3 times the size of the magnetic target itself, the magnetic target is regarded as a magnetic dipole. Substitute the position vector r1 and magnetic moment vector m1 calculated in S110 into the magnetic dipole model (2) to calculate the inversion magnetic field B generated by the magnetic interference source of the platform at the long baseline magnetic detection system. I ,

[0019]

[0020] In the formula, the vacuum permeability μ0 = 4π × 10 -7 T·m / A, p1 is the position coordinate of the magnetic sensor at the long baseline magnetic detection system;

[0021] S130. Isolate the magnetic field generated by the magnetic interference source, calculate the position vector and magnetic moment vector of the magnetic target. The long-baseline magnetic detection system measures the superimposed magnetic field B generated by the magnetic interference source and the magnetic target. S Superimposed magnetic field B S Subtract the inverted magnetic field B I This completes the compensation for the magnetic interference source, thereby obtaining the target magnetic field B generated by the magnetic target. T Using the target magnetic field B T The magnetic gradient tensor G generated by the magnetic target measured at the long baseline distance is obtained. 2 Using the magnetic gradient tensor G 2 The positioning formula of tensor magnetic positioning technology calculates the position vector r2 of the magnetic target, and then... 2 And r2 replaces G in formula (1) 1 And r1, that is, the magnetic moment vector m2 of the magnetic target is calculated.

[0022] Furthermore, S200 specifically includes three system parameters: short baseline distance D1, long baseline distance D2, and distance r1 between the magnetic detection system and the magnetic interference source.

[0023] Furthermore, S200 specifically includes the following steps:

[0024] S210. Design the long baseline distance D2. Based on the detection requirements, determine the magnetic moment vector m2 and the positioning distance r2 of the magnetic target. Without considering the influence of magnetic interference sources, calculate the relative positioning error ρ of the magnetic target under different baseline distances D2 according to the calculation steps in S100. When ρ is the smallest, the value of D2 is the optimal value.

[0025] S220. Calculate the magnetic moment vector m1 of the magnetic interference source using a short baseline magnetic detection system and formula (1);

[0026] S230. Design the short baseline distance D1 and the distance r1 between the magnetic detection system and the magnetic interference source. Calculate the relative positioning error under different D1 and r1. When ρ is the minimum, the values ​​of D1 and r1 are optimal.

[0027] The beneficial effects of this invention are:

[0028] (1) In view of the current technology, which has not been able to achieve long-distance magnetic target positioning and has difficulty in accurately and in real time removing hard and soft magnetic interference generated by the platform at the magnetic detection system, this invention proposes a long-short baseline composite magnetic detection system that first removes the magnetic interference source through a short baseline magnetic detection system and then achieves long-distance magnetic target positioning through a long baseline magnetic detection system. The design method of each parameter of the magnetic detection system is also given.

[0029] (2) When the present invention uses the designed long and short baseline composite magnetic detection system to locate magnetic targets, the relative positioning error percentage ρ does not exceed 5% within a positioning distance of 535m, which has successfully completed the positioning of magnetic targets under long distance conditions.

[0030] (3) When the present invention uses the designed long and short baseline composite magnetic detection system to locate magnetic targets, when the positioning distance is 500m, the positioning error percentage ρ before removing airborne magnetic interference is 353.8%, and the positioning error percentage ρ after removing airborne magnetic interference is 0.70%, thus achieving accurate compensation of airborne interference magnetic field. Attached Figure Description

[0031] Figure 1 The impact of baseline distance on maximum positioning distance;

[0032] Figure 2 It is a combined long and short baseline magnetic detection system;

[0033] Figure 3The result is the optimal long baseline calculation result;

[0034] Figure 4 The variation of the positioning error percentage ρ with the distance r1 from the interference source and the short baseline distance D1 is shown.

[0035] Figure 5 ρ represents the percentage of positioning error at different positioning distances;

[0036] Figure 6 ρ represents the percentage of positioning error before and after interference source compensation. Detailed Implementation

[0037] 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] Reference Figures 1-6 As shown, this invention proposes a method for locating and designing a long-range magnetic target. The design method of the composite magnetic target positioning system includes the following steps:

[0039] S100, Long-distance magnetic target localization method: The position coordinates and magnetic moment of the magnetic interference source are inverted using a short-baseline magnetic detection system. Then, the interference magnetic field generated by the magnetic interference source at the long-baseline magnetic detection system is stripped off in real time using the inversion results. Finally, the long-baseline magnetic detection system is used to realize the long-distance magnetic target localization and obtain the magnetic moment vector m2 of the magnetic target.

[0040] Design method of S200 long and short baseline composite magnetic detection system: Based on actual working conditions and detection requirements, design methods for various parameters of the magnetic detection system are proposed, specifically including three system parameters: short baseline distance D1, long baseline distance D2, and distance r1 between the magnetic detection system and the magnetic interference source.

[0041] Furthermore, S100 specifically includes the following steps:

[0042] S110. Using a short baseline magnetic detection system to retrieve the location coordinates and magnetic moment of the magnetic interference source:

[0043] Measuring the magnetic gradient tensor G using a short baseline magnetic detection system 1 The positioning formula of the tensor magnetic positioning method and the measured G 1 Calculate the position vector r1 = [x1, y1, z1] of the magnetic interference source. T r1 is the magnitude of the position vector r1. After calculating the position vector of the magnetic interference source, the magnetic moment vector m1 is calculated according to equation (1).

[0044] m1=(A T ·A) -1 A T ·G 1 (1)

[0045] In the formula:

[0046]

[0047] S120. Calculate the magnetic field generated by the magnetic interference source at the long baseline magnetic detection system. When the detection distance is greater than 3 times the size of the magnetic target itself, the magnetic target is regarded as a magnetic dipole. Substitute the position vector r1 and magnetic moment vector m1 calculated in S110 into the magnetic dipole model (2) to calculate the inversion magnetic field B generated by the magnetic interference source of the platform at the long baseline magnetic detection system. I ,

[0048]

[0049] In the formula, the vacuum permeability μ0 = 4π × 10 -7 T·m / A, p1 is the position coordinate of the magnetic sensor at the long baseline magnetic detection system;

[0050] S130. Isolate the magnetic field generated by the magnetic interference source, calculate the position vector and magnetic moment vector of the magnetic target. The long-baseline magnetic detection system measures the superimposed magnetic field B generated by the magnetic interference source and the magnetic target. S Superimposed magnetic field B S Subtract the inverted magnetic field B I This completes the compensation for the magnetic interference source, thereby obtaining the target magnetic field B generated by the magnetic target. T Using the target magnetic field B T The magnetic gradient tensor G generated by the magnetic target measured at the long baseline distance is obtained. 2 Using the magnetic gradient tensor G 2 The positioning formula of tensor magnetic positioning technology calculates the position vector r2 of the magnetic target, and then... 2 And r2 replaces G in formula (1) 1 And r1, that is, the magnetic moment vector m2 of the magnetic target is calculated.

[0051] Furthermore, S200 specifically includes three system parameters: short baseline distance D1, long baseline distance D2, and distance r1 between the magnetic detection system and the magnetic interference source.

[0052] Furthermore, S200 specifically includes the following steps:

[0053] S210. Design the long baseline distance D2. Based on the detection requirements, determine the magnetic moment vector m2 and the positioning distance r2 of the magnetic target. Without considering the influence of magnetic interference sources, calculate the relative positioning error ρ of the magnetic target under different baseline distances D2 according to the calculation steps in S100. When ρ is the smallest, the value of D2 is the optimal value.

[0054] S220. Calculate the magnetic moment vector m1 of the magnetic interference source using a short baseline magnetic detection system and formula (1);

[0055] S230. Design the short baseline distance D1 and the distance r1 between the magnetic detection system and the magnetic interference source. Calculate the relative positioning error under different D1 and r1. When ρ is the minimum, the values ​​of D1 and r1 are optimal.

[0056] Specifically, tensor magnetic positioning technology requires a long-baseline magnetic detection system to achieve long-distance magnetic target positioning. However, for large-volume magnetic detection systems, existing technologies struggle to accurately and in real-time isolate the hard and soft magnetic interference generated by the platform at the magnetic detection system. The purpose of this invention is to propose a long-short baseline composite magnetic detection system. This system utilizes a short-baseline magnetic detection system to isolate platform magnetic interference in real-time, while using a long-baseline magnetic detection system to achieve long-distance magnetic target positioning. This invention proposes a method for positioning long-distance magnetic targets and its design.

[0057] Furthermore, no scholar has yet proposed a design method for a long-range magnetic target positioning system. The purpose of this invention is to propose a method for locating and designing a long-range magnetic target. Based on the operating conditions and detection requirements, various parameters of the magnetic detection system are designed to achieve long-range magnetic target positioning.

[0058] The following is a specific implementation method of the present invention:

[0059] Based on the invariant of the magnetic gradient tensor, some scholars have proposed the scalar triangulation and ranging (STAR) method, which is unaffected by the Earth's magnetic field. The tensor magnetic positioning method will be illustrated using the STAR method as an example. The STAR method calculates the magnetic target's r = [x0, y0, z0]. T The formula for locating a position vector is:

[0060]

[0061] in C represents the magnetic gradient contraction in the positive z-axis direction. T , C represents the negative z-axis direction T D is the baseline distance, and z = [0, 0, 1] T , ▽C T For magnetic gradient contraction C T The gradient of C. T The calculation formula is equation (4), CT The calculation formula is (5).

[0062]

[0063]

[0064] in C represents the magnetic gradient contraction in the positive x-axis direction. T , C represents the negative x-axis direction T , C represents the magnetic gradient contraction in the positive y-axis direction. T , C represents the negative y-axis direction T x = [1, 0, 0] T y = [0, 1, 0] T .

[0065] Assume the detection requirement is to locate a magnetic moment of 2 × 10⁻⁶. 6 A·m 2 When targeting magnetic targets, the maximum positioning distance should be no less than 500m, and the magnetic moment of the magnetic interference source should be 50A·m. 2 The simulation conditions are shown in Table 1.

[0066] <![CDATA[Magnetic target magnetic moment m1]]> <![CDATA[Position coordinate r2]]> Magnetic sensor resolution S <![CDATA[Magnetic moment m2 of the magnetic interference source]]> Environmental noise <![CDATA[(0,2×10 6 ,0)A·m 2 ]]> (0,0,500)m 10fT <![CDATA[(0,50,0)A·m 2 ]]> 100T

[0067] Table 1 Simulation conditions

[0068] First, the design of a combined long- and short-baseline magnetic detection system is carried out:

[0069] (1) Calculate the long-distance baseline D2

[0070] First, based on the magnitude of the magnetic moment of the magnetic target and the positioning distance, the relationship between the positioning error percentage ρ and the long baseline D2 is derived through simulation analysis, such as... Figure 3 As shown in the figure. Simulation results show that the optimal long baseline distance D2 is 35m when the positioning error percentage ρ is minimized.

[0071] (2) Calculate the distance r1 between the magnetic detection system and the interference source and the short baseline distance D1.

[0072] Simulation analysis revealed the variation of the positioning error percentage ρ with both the distance to the interference source r1 and the short baseline distance D1, as follows: Figure 4 As shown in the figure. Simulation results show that the optimal distance r1 is 17.6m and the optimal short baseline distance is 3.6m.

[0073] Next, the pre-designed long- and short-baseline composite magnetic detection system is used to locate the magnetic target and verify the positioning effect. The positioning error percentage ρ at different positioning distances is shown below. Figure 5As shown, the relative positioning error percentage ρ does not exceed 5% within a positioning distance of 535m, indicating that the maximum positioning distance of the magnetic detection system is approximately 535m, which meets the detection requirements.

[0074] When using the designed long-short baseline composite magnetic detection system to locate magnetic targets, at a positioning distance of 500m, the positioning error percentage ρ before removing platform magnetic interference is 353.8%, and the positioning error percentage ρ after removing airborne magnetic interference is 0.70%, indicating that the magnetic detection system designed in this patent accurately compensates for platform magnetic interference.

Claims

1. A method for locating and designing long-range magnetic targets, characterized in that, The design method of a composite magnetic target positioning system includes the following steps: S100. The position coordinates and magnetic moment of the magnetic interference source are inverted using a short-baseline magnetic detection system. Then, the interference magnetic field generated by the magnetic interference source at the long-baseline magnetic detection system is stripped away in real time using the inversion results. Finally, the long-baseline magnetic detection system is used to locate the magnetic target at a long distance, and the magnetic moment vector of the magnetic target is obtained. m 2; S200. Based on actual working conditions and detection requirements, and in conjunction with the magnetic moment vector... m 2. Design methods for various parameters of the magnetic detection system are proposed.

2. The method for locating and designing a long-range magnetic target according to claim 1, characterized in that, S100 specifically includes the following steps: S110. Using a short baseline magnetic detection system to retrieve the location coordinates and magnetic moment of the magnetic interference source: Measuring the magnetic gradient tensor using a short baseline magnetic detection system G 1 The positioning formula and measured data are obtained using the tensor magnetic positioning method. G 1 Calculate the position vector of the magnetic interference source r 1 = [ x 1, y 1, z 1] T , r 1 is the position vector r The magnitude of 1, i.e., the distance between the magnetic detection system and the magnetic interference source, is used to calculate the position vector of the magnetic interference source. Then, the magnetic moment vector is calculated according to equation (1). m 1, (1) In the formula: S120. Calculate the magnetic field generated by the magnetic interference source at the long-baseline magnetic detection system. When the detection distance is greater than three times the size of the magnetic target, the magnetic target is considered a magnetic dipole. The position vector calculated in S110 is then used... r 1 and magnetic moment vector m Substituting into the magnetic dipole model equation (2), the inversion magnetic field generated by the magnetic interference source on the platform at the long baseline magnetic detection system is calculated. B I , (2) In the formula, the vacuum permeability μ0 = 4π × 10 -7 T·m / A, p 1 represents the position coordinates of the magnetic sensor at the long baseline magnetic detection system; S130. After stripping away the magnetic field generated by the magnetic interference source, calculate the position vector and magnetic moment vector of the magnetic target. The long-baseline magnetic detection system measures the superimposed magnetic field generated by the magnetic interference source and the magnetic target. B S Superimposed magnetic field B S Subtract the inverted magnetic field B I This process compensates for magnetic interference sources, thereby obtaining the target magnetic field generated by the magnetic target. B T Utilizing the target magnetic field B T Obtain the magnetic gradient tensor generated by the magnetic target measured at the long baseline distance. G 2 Using the magnetic gradient tensor G 2 The positioning formula of tensor magnetic positioning technology calculates the position vector of a magnetic target. r 2. G 2 and r 2 replaces formula (1) G 1 and r 1. That is, calculate the magnetic moment vector of the magnetic target. m 2.

3. The method for locating and designing a long-range magnetic target according to claim 1, characterized in that, In S200, this specifically includes short baseline distance. D 1. Long baseline distance D 2. Distance between the magnetic detection system and the magnetic interference source r 1. These three system parameters.

4. The method for locating and designing a long-range magnetic target according to claim 2, characterized in that, S200 specifically includes the following steps: S210, Design Long Baseline Distance D 2. Determine the magnetic moment vector of the magnetic target based on the detection requirements. m 2 and positioning distance r 2. Ignoring the influence of magnetic interference sources, calculate the different... according to the calculation steps in S100. D 2. Relative positioning error of magnetic targets ρ, when ρ At its minimum, D The optimal value is 2; S220. Calculate the magnetic moment vector of the magnetic interference source using a short baseline magnetic detection system and formula (1). m 1; S230, Design Short Baseline Distance D 1. Distance between the magnetic detection system and the magnetic interference source r 1. Calculate different D 1. r The relative positioning error under condition 1, when ρ At its minimum, D 1 and r The value of 1 is the optimal value.

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