INVERSE ESTIMATION-BASED RADIUS CALCULATION METHOD AND SYSTEM FOR FERROMAGNETIC TARGET DETECTION

Abstract

Disclosed is an inverse estimation-based radius calculation method and system for ferromagnetic target detection. The calculation method includes a data acquisition step and a ferromagnetic target detection radius calculation step. Distrubance of a scale model to power frequency electromagnetic waves is used to inversely estimate a corresponding ferromagnetic target detection radius. Inverse estimation is performed separately for an air layer and a sea water layer according to test results of multiple scale model tests and in consideration of both a stationary state and a motion state of the scale model, so as to acquire a ferromagnetic target detection radius calculation formula. Weights of factors such as mass, speed, depth, and height are great in inverse estimation, so that inverse estimation precision is improved. The majority of background noise interference can be screened out of the power frequency electromagnetic waves.

Claims

1. An inverse estimation-based radius calculation method for ferromagnetic target detection, the method being used to inversely estimate, according to a test result of a single scale model stationary test or scale model motion test, a ferromagnetic target detection radius R in a corresponding ferromagnetic target stationary test or ferromagnetic target motion test, and the method comprising the following steps: (1) a data acquisition step: respectively acquiring values of a model detection radius r, a ratio p of the mass of a ferromagnetic target to the mass of a scale model, a diving depth L.sub.1 of the ferromagnetic target, a depth L.sub.2 of the scale model in sea water, an attenuation index n.sub.1 of power frequency electromagnetic wave intensity in an air layer with respect to a distance, a height l.sub.1 of a ferromagnetic target detection platform, a flight height l.sub.2 of an unmanned aerial vehicle, a speed V of the ferromagnetic target, a speed v of the scale model, a ferromagnetic target included angle θ.sub.1, a scale model included angle θ.sub.2, an orientation change speed V.sub.∂ of the ferromagnetic target, and an orientation change speed v.sub.∂ of the scale model, wherein the value of r is calculated by using the following formula: r = t × v1 ÷ 2, t being a disturbance duration, v1 being a flight speed of the unmanned aerial vehicle, and the value of t being the test result of the single scale model test; and (2) a ferromagnetic target detection radius calculation step: calculating the ferromagnetic target detection radius R according to the following formula: $\frac{R}{r}=p\frac{e^{-k_1{L}_1}\left(1+V+{\text{V}}_{\partial }\cdot \text{D}\right)M\cdot sin{\theta }_1\frac{1}{k_2{l}_1{}^{n_1}}}{e^{-k_2{L}_2}\left(1+v+v_{\partial }\cdot \text{d}\right)m\cdot sin{\theta }_2\frac{1}{k_2{l}_2{}^{n_1}}}$ where e is a base number of a natural logarithm, k.sub.1 is an attenuation coefficient of sea water to a magnetic field, and k.sub.2 is an attenuation coefficient of air to the magnetic field.

2. The inverse estimation-based radius calculation method for ferromagnetic target detection according to claim 1, wherein a derivation process of the formula in the ferromagnetic target detection radius calculation step comprises: (1) acquiring the following empirical formulas according to test results of multiple scale model tests: $\frac{H_{{\theta }_2}}{H_{{\theta }_1}}=\frac{1}{k_2{l}_1{}^{n_1}};$ $\frac{H_{{\theta }_2}}{H_{{\theta }_1}}=e^{-k_1{L}_1}$ wherein H.sub.θ2 and H.sub.θ1 are respectively power frequency electromagnetic wave intensities at two different points in the same medium layer, l.sub.1 is a distance between two points in the air layer, L.sub.1 is a distance between two points in the sea water layer, the medium layer is the air layer or the sea water layer, and the multiple scale model tests comprise a scale model stationary test and a scale model motion test; (2) performing inverse estimation separately for the air layer and the sea water layer according to the test results and the empirical formulas and in consideration of both a stationary state and a motion state of the scale model, so as to acquire an empirical formula for calculating a power frequency electromagnetic wave intensity B.sub.2: $B_2=-\frac{\pi SI}{{\lambda }^2{r}_{\text{0}}}{\text{e}}^{-k_1{L}_2}\left(1+v+v_{\partial }\cdot d\right)m\cdot sin{\theta }_2\frac{1}{k_2{l}_2{}^{n_1}}$ where π is Pi, S is a total area of a dipole group, I is current intensity, λ is a wavelength of power frequency electromagnetic waves, m is the mass of the scale model, v is a movement speed of a detection target, v.sub.∂ is an estimated change speed of the target, d is a diameter of the target, θ.sub.2 is a detection included angle, L.sub.2 is a depth of the detection target in sea water, and l.sub.2 is a height of a detection point; and (3) performing inverse estimation according to the empirical formula for H.sub.θ to acquire a ferromagnetic target detection radius calculation formula: $\frac{R}{r}=\frac{-\frac{\pi SI}{{\lambda }^2{r}_{\text{0}}}{e}^{-k_1{L}_1}\left(1+V+{\text{V}}_{\partial }\cdot \text{D}\right)M\cdot sin{\theta }_1\frac{1}{k_2{l}_1{}^{n_1}}}{-\frac{\pi SI}{{\lambda }^2{r}_0}{e}^{-k_1{L}_2}\left(1+v+v_{\partial }\cdot \text{d}\right)m\cdot sin{\theta }_2\frac{1}{k_2{l}_2{}^{n_1}}}$ wherein said formula is used to acquire the formula in the ferromagnetic target detection radius calculation step.

3. The inverse estimation-based radius calculation method for ferromagnetic target detection according to claim 2, wherein H.sub.2 and h.sub.2 both have multiple different values in each of the multiple scale model tests.

4. The inverse estimation-based radius calculation method for ferromagnetic target detection according to claim 1, wherein in the data acquisition step, n.sub.1 is a preset natural number, the value of k.sub.1 is 0.357, and the value of k.sub.2 is 61.24.

5. An inverse estimation-based radius calculation system for ferromagnetic target detection, the system being used to inversely estimate, according to a test result of a single scale model stationary test or scale model motion test, a ferromagnetic target detection radius R in a corresponding ferromagnetic target stationary test or ferromagnetic target motion test, and the system comprising the following modules: a data acquisition module, configured to perform the following: respectively acquiring values of a model detection radius r, a ratio p of the mass of a ferromagnetic target to the mass of a scale model, a diving depth L.sub.1 of the ferromagnetic target, a depth L.sub.2 of the scale model in sea water, an attenuation index n.sub.2 of power frequency electromagnetic wave intensity in a sea water layer with respect to a distance, a height l.sub.1 of a ferromagnetic target detection platform, a flight height l.sub.2 of an unmanned aerial vehicle, a speed V of the ferromagnetic target, a speed v of the scale model, an orientation change speed V.sub.∂ of the ferromagnetic target, an orientation change speed V.sub.∂ of the scale model, a ferromagnetic target included angle θ.sub.1, a scale model included angle θ.sub.2, a diameter D of the ferromagnetic target, and a diameter d of the scale model, wherein the value of r is calculated by using the following formula: r = t × v1 ÷ 2, t being a disturbance duration, v1 being a flight speed of the unmanned aerial vehicle, and the value of t being the test result of the single scale model test; and a ferromagnetic target detection radius calculation module, configured to perform the following: calculating the ferromagnetic target detection radius R according to the following formula: $\frac{R}{r}=\frac{-\frac{\pi SI}{{\lambda }^2{r}_{\text{0}}}{e}^{-k_1{L}_1}\left(1+V+{\text{V}}_{\partial }\cdot \text{D}\right)M\cdot sin{\theta }_1\frac{1}{k_2{l}_1{}^{n_1}}}{-\frac{\pi SI}{{\lambda }^2{r}_0}{e}^{-k_1{L}_2}\left(1+v+v_{\partial }\cdot \text{d}\right)m\cdot sin{\theta }_2\frac{1}{k_2{l}_2{}^{n_1}}}$ where e is a base number of a natural logarithm, k.sub.1 is an attenuation coefficient of sea water to a magnetic field, and k.sub.2 is an attenuation coefficient of air to the magnetic field.

6. The inverse estimation-based radius calculation system for ferromagnetic target detection according to claim 5, wherein a derivation operation of the formula in the ferromagnetic target detection radius calculation module comprises: (1) acquiring the following empirical formulas according to test results of multiple scale model tests: $\frac{H_{{\theta }_2}}{H_{{\theta }_1}}=\frac{1}{k_2{l}_1{}^{n_1}};$ $\frac{H_{{\theta }_2}}{H_{{\theta }_1}}=e^{-k_1{L}_1}$ wherein H.sub.θ2 and H.sub.θ1 are respectively power frequency electromagnetic wave intensities at two different points in the same medium layer, l.sub.1 is a distance between two points in the air layer, L.sub.1 is a distance between two points in the sea water layer, the medium layer is the air layer or the sea water layer, and the multiple scale model tests comprise a scale model stationary test and a scale model motion test; (2) performing inverse estimation separately for the air layer and the sea water layer according to the test results and the empirical formulas and in consideration of both a stationary state and a motion state of the scale model, so as to acquire an empirical formula for calculating a power frequency electromagnetic wave intensity H.sub.θ: $B_2=-\frac{\pi SI}{{\lambda }^2{r}_{\text{0}}}{\text{e}}^{-k_1{L}_2}\left(1+v+v_{\partial }\cdot d\right)m\cdot sin{\theta }_2\frac{1}{k_2{l}_2{}^{n_1}}$ where π is Pi, S is a total area of a dipole group, I is current intensity, λ is a wavelength of power frequency electromagnetic waves, m is the mass of the scale model, v.sub.0 is a movement speed of a detection target, v.sub.∂ is an orientation change speed of the scale model, d is a diameter of the scale model, θ is a detection included angle, L.sub.2 is a depth of the detection target in sea water, and l.sub.2 is a height of a detection point; and (3) performing inverse estimation according to the empirical formula for H.sub.θ to acquire a ferromagnetic target detection radius calculation formula: $\frac{R}{r}=\frac{-\frac{\pi SI}{{\lambda }^2{r}_{\text{0}}}{e}^{-k_1{L}_1}\left(1+V+{\text{V}}_{\partial }\cdot \text{D}\right)M\cdot sin{\theta }_1\frac{1}{k_2{l}_1{}^{n_1}}}{-\frac{\pi SI}{{\lambda }^2{r}_0}{e}^{-k_1{L}_2}\left(1+v+v_{\partial }\cdot \text{d}\right)m\cdot sin{\theta }_2\frac{1}{k_2{l}_2{}^{n_1}}}$ wherein said formula is used to acquire the formula in the ferromagnetic target detection radius calculation module.

7. The inverse estimation-based radius calculation system for ferromagnetic target detection according to claim 6, wherein L.sub.2 and l.sub.2 both have multiple different values in each of the multiple scale model tests.

8. The inverse estimation-based radius calculation system for ferromagnetic target detection according to claim 5, wherein in the data acquisition module, n.sub.1 and n.sub.2 are both preset natural numbers, the value of k.sub.1 is 0.357, and the value of k.sub.2 is 61.24.

9. An inverse estimation-based radius calculation device for ferromagnetic target detection, comprising a memory and a processor, wherein the memory is used to store a computer program, and the processor, when executing the computer program, implements the inverse estimation-based radius calculation method for ferromagnetic target detection according claim 1.

10. A computer-readable storage medium, characterized in that the storage medium stores a computer program, and when executed by a processor, the computer program implements the inverse estimation-based radius calculation method for ferromagnetic target detection according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0060] FIG. 1 is a flowchart of an inverse estimation-based radius calculation method for ferromagnetic target detection according to an embodiment of the present invention; and

[0061] FIG. 2 is schematic diagram of a detection included angle formed when a detection target is directly under a detection point in an inverse estimation-based radius calculation method for ferromagnetic target detection according to an embodiment of the present invention.

DETAILED DESCRIPTION

[0062] In order to make the objective, technical solution, and advantages of the present invention clearer, the following detailed description of the present invention is provided with reference to the accompanying drawings and embodiments. It is to be understood that specific embodiments described herein are used merely to explain the present invention, and are not used to limit the present invention.

[0063] As shown in FIG. 1, the present embodiment provides an inverse estimation-based radius calculation method for ferromagnetic target detection, the method being used to inversely estimate, according to a test result of a single scale model stationary test or scale model motion test, a ferromagnetic target detection radius R in a corresponding ferromagnetic target stationary test or ferromagnetic target motion test. The method includes the following steps: [0064] (1) a data acquisition step: [0065] respectively acquiring values of a model detection radius r, a ratio p of the mass of a ferromagnetic target to the mass of a scale model, a diving depth L.sub.1 of the ferromagnetic target, a depth L.sub.2 of the scale model in sea water, an attenuation index n.sub.1 of power frequency electromagnetic wave intensity in an air layer with respect to a distance, a height l.sub.1 of a ferromagnetic target detection platform, a flight height l.sub.2 of an unmanned aerial vehicle, a speed V of the ferromagnetic target, a speed v of the scale model, an orientation change speed V.sub.∂ of the ferromagnetic target, an orientation change speed ν.sub.∂ of the scale model, a diameter D of the ferromagnetic target, a diameter d of the scale model, a ferromagnetic target included angle θ.sub.1, and a scale model included angle θ.sub.2, [0066] wherein L.sub.1 = 120 m, L.sub.2 = 19 m, l.sub.1 = 5000 m, l.sub.2 = 10 m, v = 0.5 m/s, V = 20 m/s, sinθ.sub.1 = 1, and sinθ.sub.2 = 0.98, the mass of the scale model is 2.3 tons, and the ferromagnetic target is an underwater vehicle, and has a mass of 9000 tons.

[0067] The value of r is 112 m, and is calculated by using the following formula: r = t × v1 ÷ 2. t is a disturbance duration, and has a value of 44.8 s. v1 is a flight speed of the unmanned aerial vehicle, and has a value of 5 m/s.

[0068] The value of t is the test result of the single scale model test. In the test, a sampling rate of a sensor is 1024 Hz, and an analysis frequency is 50 Hz. Compared with conventional acoustic detection, attenuation of power frequency electromagnetic waves caused by sea water is weak, so that the power frequency electromagnetic waves have a high capability of penetrating the sea water layer. The power frequency electromagnetic waves do not cause large changes in electromagnetic signals due to changes in submarine topography, such that a disturbance signal does not include too much clutter. The power frequency electromagnetic waves are spatially evenly distributed, and the disturbance signal is clear, so that the disturbance signal can be acquired without extremely complex processing, thereby acquiring the disturbance duration.

[0069] a ferromagnetic target detection radius calculation step: [0070] calculating the ferromagnetic target detection radius R according to the following formula, a value thereof being 21.74 km: [0071] where e is a base number of a natural logarithm, k.sub.1 is an attenuation coefficient of sea water to a magnetic field, and has a value of 0.357, k.sub.2 is an attenuation coefficient of air to the magnetic field, and has a value of 61.24, and n.sub.1 is a preset natural number. The value of n.sub.1 may be the same, or may be different. In this embodiment, the value of n.sub.1 is 1.

[0072] A derivation process of the formula comprises: [0073] (1) The following empirical formulas are acquired according to test results of multiple scale model tests: [0074] wherein H.sub.θ2 and H.sub.θ1 are respectively power frequency electromagnetic wave intensities at two different points in the same medium layer, l.sub.1 is a distance between two points in the air layer, L.sub.1 is a distance between two points in the sea water layer, the medium layer is the air layer or the sea water layer, and the multiple scale model tests include a scale model stationary test and a scale model motion test. L.sub.2 and l.sub.2 both have multiple different values in each of the multiple scale model tests. In this embodiment, L.sub.2 has six values in total and L.sub.2 ≤ 30 m, and l.sub.2 has seven values in total and l.sub.2 ≤ 50 m.

[0075] The power frequency electromagnetic waves are generated by a high-voltage power transmission network, and an alternating current and an alternating magnetic field excite each other. A power frequency high-voltage power grid is equivalent to a dipole group, and serves as a signal source of the power frequency electromagnetic waves. A signal of the power frequency electromagnetic waves is in a positive proportional relationship to both a total area of the dipole group and the current intensity in the power transmission network. The power frequency electromagnetic waves have a fixed time-varying period, and the scale model can still generate disturbance to the power frequency electromagnetic waves when the scale model is stationary, so that a case in which the speed of the scale model is zero needs to be considered. In addition, different media attenuate the power frequency electromagnetic waves differently, so that inverse estimation needs to be performed separately for the air layer and the sea water layer.

[0076] Inverse estimation is performed separately for the air layer and the sea water layer according to the test results and the empirical formulas and in consideration of both a stationary state and a motion state of the scale model, so as to acquire an empirical formula for calculating a power frequency electromagnetic wave intensity B.sub.2:

[00014]$B_2=-\frac{\pi \text{}SI}{{\lambda }^2{r}_0}{e}^{-k_1{L}_2}\left(1+v+v_{\partial }\cdot d\right)m\cdot sin{\theta }_2\frac{1}{k_2{l}_2{}^{n_1}}$

where π is Pi, S is a total area of a dipole group, I is current intensity, λ, is a wavelength of power frequency electromagnetic waves, m is the mass of the scale model, ν.sub.0 is a movement speed of a detection target, H is a depth of the detection target in sea water, l.sub.2 is a height of a detection point, ν.sub.∂ is an orientation change speed of the scale model, d is a diameter of the target, and θ is a detection included angle, as shown in FIG. 2.

[0077] Inverse estimation is performed according to the empirical formula for B.sub.2 to acquire a ferromagnetic target detection radius calculation formula:

[00015]$\frac{R}{r}=\frac{-\frac{\pi \text{}SI}{{\lambda }^2{r}_0}{e}^{-k_1{L}_1}\left(1+V+{\text{V}}_{\partial }\cdot \text{D}\right)M\cdot sin{\theta }_1\frac{1}{k_2{l}_1{}^{n_1}}}{-\frac{\pi \text{}SI}{{\lambda }^2{r}_0}{e}^{-k_1{L}_2}\left(1+v+v_{\partial }\cdot \text{d}\right)m\cdot sin{\theta }_2\frac{1}{k_2{l}_2{}^{n_1}}}$

[0078] Said formula is used to acquire the formula in the ferromagnetic target detection radius calculation step. Since the sea is mostly a far-field region of power frequency electromagnetic waves, weights of factors such as mass, speed, depth, and height are great in inverse estimation, so that inverse estimation precision is improved.

[0079] In the ferromagnetic target detection radius calculation step, a calculation process of the values of k.sub.1 and k.sub.2 is as follows:

[0080] Since air and sea water have different physical parameters and have different absorptive actions with respect to electromagnetic waves, the attenuation coefficient k is calculated according to the following formula:

[00016]$\text{k}\text{=}\omega \sqrt{\frac{\mu \text{}\epsilon }{2}\left(1+\frac{{\sigma }^2}{{\omega }^2{\epsilon }^2}\right)+1}$

where ω is an angular frequency of electromagnetic waves, σ is the conductivity of a medium, .Math. is the magnetic permeability of the medium, and ε is a dielectric constant of the medium. Calculation is performed according to physical properties of sea water and air and parameters thereof, so as to obtain: k.sub.1 = 0.357, and k.sub.2 = 61.24.

[0081] Power frequency electromagnetic waves can be used to measure a disturbance signal without requiring a large number of excitation sources. In addition, power frequency electromagnetic waves are very low-frequency electromagnetic waves, so that the majority of background noise interference can be screened out. The power frequency electromagnetic waves have a large wavelength and a long propagation distance, and so can also be used to perform signal detection in a far-field region, thereby meeting the requirements of large-range detection in the sea. Therefore, the inverse estimation-based radius calculation method for ferromagnetic target detection in this embodiment can be used to perform large-distance wide-range detection for a ferromagnetic target concealed by background noise of the sea.

[0082] The present embodiment provides an inverse estimation-based radius calculation system for ferromagnetic target detection, the system being used to inversely estimate, according to a test result of a single scale model stationary test or scale model motion test, a ferromagnetic target detection radius R in a corresponding ferromagnetic target stationary test or ferromagnetic target motion test. The system includes the following modules: [0083] a data acquisition module, configured to perform the following: [0084] respectively acquiring values of a model detection radius r, a ratio p of the mass of a ferromagnetic target to the mass of a scale model, a diving depth L.sub.1 of the ferromagnetic target, a depth L.sub.2 of the scale model in sea water, an attenuation index n.sub.1 of power frequency electromagnetic wave intensity in an air layer with respect to a distance, a height l.sub.1 of a ferromagnetic target detection platform, a flight height l.sub.2 of an unmanned aerial vehicle, a speed V of the ferromagnetic target, a speed v of the scale model, an orientation change speed V.sub.∂ of the ferromagnetic target, an orientation change speed ν.sub.∂ of the scale model, a diameter D of the ferromagnetic target, a diameter d of the scale model, a ferromagnetic target included angle θ.sub.1, and a scale model included angle θ.sub.2, [0085] wherein r is calculated by using the following formula: r = t × v1 ÷ 2, t being a disturbance duration, v1 being a flight speed of the unmanned aerial vehicle, and the value of t being the test result of the single scale model test; and [0086] a ferromagnetic target detection radius calculation module, configured to perform the following: [0087] calculating the ferromagnetic target detection radius R according to the following formula: [0088] where e is a base number of a natural logarithm, k.sub.1 is an attenuation coefficient of sea water to a magnetic field, k.sub.2 is an attenuation coefficient of air to the magnetic field, and n.sub.1 is a preset natural number.

[0089] A derivation operation of the formula comprises: [0090] (1) acquiring the following empirical formulas according to test results of multiple scale model tests: [0091] wherein H.sub.θ2 and H.sub.θ1 are respectively power frequency electromagnetic wave intensities at two different points in the same medium layer, l.sub.1 is a distance between two points in the air layer, L.sub.1 is a distance between two points in the sea water layer, the medium layer is the air layer or the sea water layer, the multiple scale model tests include a scale model stationary test and a scale model motion test, and L.sub.2 and l.sub.2 both have multiple different values in each of the multiple scale model tests.

[0092] performing inverse estimation separately for the air layer and the sea water layer according to the test results and the empirical formulas and in consideration of both a stationary state and a motion state of the scale model, so as to acquire an empirical formula for calculating a power frequency electromagnetic wave intensity B.sub.2:

[00020]$B_2=-\frac{\pi \text{}SI}{{\lambda }^2{r}_0}{\text{e}}^{-k_1{L}_2}\left(1+v+v_{\partial }\cdot d\right)m\cdot sin{\theta }_2\frac{1}{k_2{l}_2{}^{n_1}}$

where π is Pi, S is a total area of a dipole group, I is current intensity, λ, is a wavelength of power frequency electromagnetic waves, m is the mass of the scale model, ν is a movement speed of the scale model, L.sub.2 is a depth of the detection target in sea water, l.sub.2 is a height of a detection point, ν.sub.∂ is an orientation change speed of the scale model, d is a diameter of the scale model, and θ is a detection included angle.

[0093] performing inverse estimation according to the empirical formula for B.sub.2 to acquire a ferromagnetic target detection radius calculation formula:

[00021]$\frac{R}{r}=\frac{-\frac{\pi \text{}SI}{{\lambda }^2{r}_0}{e}^{-k_1{L}_1}\left(1+V+{\text{V}}_{\partial }\cdot \text{D}\right)M\cdot sin{\theta }_1\frac{1}{k_2{l}_1{}^{n_1}}}{-\frac{\pi \text{}SI}{{\lambda }^2{r}_0}{e}^{-k_1{L}_2}\left(1+v+v_{\partial }\cdot \text{d}\right)m\cdot sin{\theta }_2\frac{1}{k_2{l}_2{}^{n_1}}}$

wherein said formula is used to acquire the formula in the ferromagnetic target detection radius calculation module.

[0094] In the ferromagnetic target detection radius calculation module, a calculation operation of the values of k.sub.1 and k.sub.2 is as follows:

[0095] Since air and sea water have different physical parameters and have different absorptive actions with respect to electromagnetic waves, the attenuation coefficient k is calculated according to the following formula:

[00022]$\text{k}\text{=}\omega \sqrt{\frac{\mu \text{}\epsilon }{2}\left(1+\frac{{\sigma }^2}{{\omega }^2{\epsilon }^2}\right)+1}$

where ω is an angular frequency of electromagnetic waves, σ is the conductivity of a medium, .Math. is the magnetic permeability of the medium, and ε is a dielectric constant of the medium. Calculation is performed according to physical properties of sea water and air and parameters thereof, so as to obtain: k.sub.1 = 0.357, and k.sub.2 = 61.24.

[0096] It can be easily understood by those skilled in the art that the foregoing description is only preferred embodiments of the present invention and is not intended to limit the present invention. All the modifications, identical replacements and improvements within the spirit and principle of the present invention should be in the scope of protection of the present invention.