RU2297650C2 - Method for finding underwater ferromagnetic objects - Google Patents

Abstract

FIELD: technology for reconnaissance with usage of magnetic fields, possible use for finding underwater ferromagnetic objects.

SUBSTANCE: in accordance to method, to magnetic field sources are towed along research strip. Limits of research strip are set by dispersing ferromagnetic material, formed in form of masses in 1m³, positioned at distance of 80-170 meters from each other along axis of boundary with creation of a tetragon. By means of block for monitoring alternating operation of towed magnetic field sources, registration of total magnetic field of towed sources and ferromagnetic masses is performed by primary three-component transformer of magnetic field. Registered signals of total magnetic field of towed sources and ferromagnetic masses are amplified and transformed by a secondary transformer. Amplified and transformed signals of total magnetic field of towed sources and ferromagnetic masses are dispatched to computing block, in computing block, signal is determined, generated due to presence of ferromagnetic masses or underwater ferromagnetic object. Signal is sent from computing block to executing block with its following relay to monitoring block. Monitoring block ensures movement of towed magnetic field sources within given limits of research strip by means of determining signal coordinates in navigation module.

EFFECT: extended research strip.

2 dwg

Description

The invention relates to the field of underwater mining and detection of underwater objects by artificially created and natural magnetic fields and can be used to ensure navigational safety when approaching oil vessels and gas carriers when approaching unreasonable marine loading and unloading buoy terminals of types BTL and STL, as well as to detect magnetized navigational hazards (shallows, banks, underwater rocks, etc.).

There is a method of underwater mining of minerals [1], including moving along a landmark of an underwater mining unit along the bottom in parallel stripes and collecting minerals, in which the boundaries are set by dispersing the ferromagnetic material, and a device is installed on the unit for monitoring the presence of ferromagnetic material and measuring the magnitude of the magnetic fields, while moving the unit, the boundary of the next strip is set from the board of the unit simultaneously with the collection of ferromagnetic material and forest fossil in the previous lane.

The disadvantage of this method is the small width of the strip of the survey, which significantly increases the process, and, accordingly, material costs.

There is also a method of detecting underwater objects from ferromagnetic materials, based on measuring the magnetic field along the survey strip using a magnetometer [2]. This method also has a small inspection width, in particular when searching for ferromagnetic objects having a negligible intrinsic field.

To detect and measure a useful signal in the known methods, a magnetic system [3] is used, comprising a three-component magnetic field converter, a power supply, a signal amplification and conversion unit, an executive unit, a second three-component magnetic field converter, two magnetic field sources, a control unit and a computing unit in which the outputs of the first and second magnetic field sources and the outputs of the first and second three-component magnetic field transducers are connected through a control unit respectively, with a power supply unit and a signal amplification and conversion unit, the output of which is connected through the computing unit to the input of the executive unit. In this case, three-component transducers and magnetic field sources are located at the vertices of the corners of a rectangle oriented across the survey strip, the lower side of which is formed by a source and a three-component magnetic field transducer.

This system compared with the known methods [1, 2] due to the use of two three-component magnetic field transducers increases the accuracy of detection of underwater objects and increases the width of the survey strip. However, when searching for ferromagnetic objects with an insignificant intrinsic field, the width of the survey strip is insignificant. In addition, this system is practically not applicable for the detection of weakly magnetized objects.

From the theory of permanent magnets it is known (see for example: Gordin V.M., Rose E.N., Uglov B.D. Marine magnetometry. M., Nedra, 1986, p.232), that one of the main characteristics of permanent magnets is specific magnetic energy

W = V · N / 2, (J / m ³ ),

where B is the magnetic induction, H is the magnetic field strength.

This energy characterizes the potential ability of a magnet to store magnetic energy.

Wherein

(BH) max≅V _r ^2/4 ₀ μ _r ^2,

where B _r is the residual magnetic induction, μ ₀ is the magnetic permeability of the magnet rock.

и

то

где

- намагниченность, М - магнитный момент, ν - объем магнитного материала.Based on the values of the maximum specific energy that these or those magnets can create, we can estimate the magnitude of the magnetic moment. Given that the magnetic moment is directly proportional to the volume of the ferromagnetic material, the results of the assessment for one cubic meter of magnetic material, taking into account that

and

then

Where

- magnetization, M - magnetic moment, ν - volume of magnetic material.

где μ₀=4π·10^-7.When ν = 1m ³

where μ ₀ = 4π · 10 ^-7 .

The results of calculating the maximum magnetic moment that can be created by one cubic meter of ferromagnetic material have the following values:

- for Fe-Al-Ni-Co alloys (Wmax = 40 · 10 ³ J / m ³ ; Mmax = 500 kA / m ² ; K = 2 · 10 ^-8 );

- for rare-earth compounds of the SmCo type (Wmax = 72 · 10 ³ J / m ³ ; Mmax = 670 kA / m ² ; K = 1.5 · 10 ^-8 );

- compounds based on Fe, Fe-Co (Wmax = 26 · 10 ³ J / m ³ ; Mmax = 400 kA / m ² ; K = 2.5 · 10 ^-8 );

- various steels such as ЕХЗ, Е7В6 and others

(Wmax = 1 ÷ 2 · 10 ³ J / m ³ ; Mmax = 80 ÷ 110 kA / m ² ; K = 9 ÷ 12 · 10 ^-8 ).

Compounds of rare-earth metals (coefficient 1.5 · 10 ^-8 ) and steel (coefficient 9 ÷ 12 · 10 ^-8 ) have the highest energy intensity.

Estimation of the volume of ferromagnetic material necessary to create at various distances r from the center of a magnetic field source having values of 1.10 and 100 NT, based on the dependence ν≅10 ^-5 · V / M · r ³ = kBr ³ , k = 10 ^-5 / M - a coefficient depending on the magnetic material used, showed (Table 1) that to create a constant magnetic field with the required intensity of 10 NTL at a distance from the center of the source of about 200 m, approximately ten cubic meters of steel or two cubic meter of rare earth metals.

Table 1. r, m B = 1NT B = 10NT B = 100NTl B = 1NT B = 10NT B = 100NTl 5000 100,000 1,000,000 10,000,000 2000 20000 200,000 1000 one hundred 1000 10,000 twenty 200 2000 500 10 one hundred 1000 2 twenty 200 200 one 10 one hundred 0.2 2 twenty one hundred 0.1 one 10 0.02 0.2 2 fifty 0.01 0.1 one 0.002 0.02 0.2

Given the fact that the average length of a production unit or tanker is about 150 m, and the error of modular magnetic sensors is 0.1-0.01 NT (see, for example, Semevsky RB, Averkiev V.V., Yarotsky V. A. Special magnetometry (St.P., Nauka, 2002, p.164), the length of the ferromagnetic material along the recommended course of motion for detecting a useful signal will be about 300 m. In this case, the value of the inspection bandwidth using a magnetometer calculated by the formula:

B = [(10 ¹⁰ M ² / σ ₁ ² + σ ₂ ² ) ^1/3 -Z ² ] ^1/2 , where M is the magnetic moment of the ferromagnetic material, σ ₁ is the sensitivity of the magnetometer, σ ₂ is the level of magnetic noise, Z - the depth under the primary transducer of the magnetometer (at M = 50 E / m, Z = 50 m, σ ₁ = 0.001 gamma, σ ₂ = 1.73 gamma) will be 214 m.

The construction of such an artificial ferromagnetic field in marine conditions is associated with significant material costs, which, in combination with a small survey bandwidth, significantly reduces the functional possibilities of the known methods.

The objective of the proposed technical solution is to expand the functionality of known methods.

The problem is solved due to the fact that in the method of underwater mining and detection of underwater objects in magnetic fields, including moving along a landmark of a magnetic field measurement carrier, setting boundaries by dispersing ferromagnetic material or natural sources of a magnetic field, followed by measuring the magnitude of the magnetic field with the creation of an alternating magnetic field in two diagonally located vertices of a quadrangle oriented across the survey strip, boundaries, the lower side of which is formed by the source of the magnetic field and the meter and is located on the survey horizon, and the upper side is formed by the primary three-component transducers of the magnetometer - before setting the boundaries by dispersing the ferromagnetic material, masses of one cubic meter are formed from the ferromagnetic material, which are placed at distances 80 ÷ 170 m from each other along the axis of the border.

Unlike the known methods in the present method, before setting the boundaries of the survey area by dispersing the ferromagnetic material, masses of one cubic meter are formed from it, which are placed at distances of 80-170 m from each other along the axis of the border.

The invention is illustrated by drawings (figures 1 and 2). Figure 1 - block diagram of a measuring system of a magnetic field, which includes two towed sources of magnetic field 1 and 2, connected via cable cables 3 and 4, respectively, to the power supply 5 through the control unit 6, two towed primary three-component magnetic field transducer 7 and 8, connected via cable cables 9 and 10, respectively, to the secondary Converter 11 through the control unit 6, the computing unit 12, the input of which is connected to the output of the secondary Converter 11, and the output is connected to the input flax block 13. Figure 2 - exposure of the survey strip. The masses of ferromagnetic material 14, the axis of the boundary 15, the carrier 16 of the measuring system of the magnetic field.

The measuring system operates as follows. In the process of towing along the survey strip by means of the control unit 6, the magnetic sources 1 and 2 are alternately operated. The total magnetic field of the source 1 and the ferromagnetic masses 14 act on the primary track component transducer of the magnetic field 8, and the total magnetic field of the source 2 and ferromagnetic masses 14 affects primary track component magnetic field transducer 7. The signals arising from this are fed to the input of the secondary transducer 11, which amplifies and converts the signal Ala. From the secondary Converter 11, the signals alternately enter the computing unit 12, which determines the signal due to the presence of ferromagnetic masses or an underwater ferromagnetic object (when searching for underwater objects). Next, the signal is fed to the Executive unit 13, where it is recorded and transmitted to the media control system 16, which ensures the movement of the medium within the specified boundaries of the survey area (work). When searching for underwater objects, the signal enters the navigation module, where its coordinates are determined.

The sensitivity of this measuring system to the detection of magnetic fields of ferromagnetic sources is characterized by an error in the determination of the signal m _c , which is determined in accordance with the expression

where m ₁ , m ₂ are the errors in determining the sensitivity of the primary three-component magnetic field transducers 7 and 8, respectively, m _Δс is the error in determining the magnitude of the signal characterizing the presence of ferromagnetic masses or an underwater object due to a change in the initial increment between the distances from the magnetic field source 1 to the primary three-component converter 8 and the magnetic field source 2 to the three-primary converter 7. The value _Δs m can be determined from the formula _Δs m = 3M / S × m _Δs, g e M - magnetic moment of the magnetic field source, S - distance from the magnetic field source 2 to the three-primary converter 7, m _Δs - error in determining the change in the initial increment of distance from the magnetic field source 1 to the three-primary converter 7.

For a special case, when the X axis of the primary three-component magnetic field transducers 7 and 8 are oriented along the survey strip, the value of m _Δs is determined by the formula

where m _Δy '; m _Δy "- errors in determining the increment of the coordinate of the source of magnetic field 1 relative to the primary three-component transducer 7 and the source of magnetic field 2 relative to the primary three-component transducer 8, respectively.

The values of m _{Δy are} determined by the formulas

where m _y1 , m _y2 are the errors in determining the coordinate of the source of magnetic field 1 relative to the primary three-component magnetic field transducer 7 at the beginning and in the process of movement of the carrier, respectively, m _y1 , m _y2 are the errors of determining the coordinate of the source of magnetic field 2 relative to the primary magnetic field transducer 3 at the beginning and in the process of movement of the medium. The values of m _y1 , m _y2 , m _y1 , m _{y2 are} determined by the formula

составит 4000 м, что более чем в 10 раз выше, чем у известных способов (В=300 м).where A is the amplitude of the source of the magnetic field measured at the location of the primary three-component magnetic field transducer, ΔA is the measurement error A, ΔM is the measurement error M, D is the distance between the magnetic field source 1 and the primary three-component magnetic field transducer 8, Dx is the projection D to the X axis. For example, for the case when m1, m2 = 0.0001 gamma, M = 1000 E / m, S-500 m, A = 10 O, ΔA = 10 O ΔM = 0.5 E / m, Dx = 100 m, D = 150 m, the error of determination will be m _c = 0.002 gamma. When M is equal to 1000 em and m _c equal to 0 002 gamma, the width of the examination strip B calculated by

will be 4000 m, which is more than 10 times higher than that of the known methods (B = 300 m).

The creation of a magnetic field in two diagonally located vertices of a quadrangle oriented across the survey strip formed by the boundaries, the lower side of which is formed by the magnetic field source 1 and the primary three-component transducer 8 with its location on the survey horizon, and the upper side is formed by the magnetic field 2 and the primary three-component transducer 7 with the formation of boundaries by dispersing ferromagnetic material with a volume of one cubic meter at a distance of 80 ÷ 170 m a friend from each other along the axis of the border, allows you to create a constant magnetic field with a strength of 10 NT using magnetometers with a sensitivity of 0.001 ÷ 0.0001 gamma, which allows the detection of ferromagnetic objects with a survey bandwidth of up to 5000 m and low-magnetic objects with a survey bandwidth of 1000 m and more.

In the proposed method, systematic errors and errors due to the Earth’s magnetic field and its variations due to the compensation principle of the measuring system’s functioning in combination with the location of the ferromagnetic material forming the boundaries of the survey area in a certain order are excluded from the processing results, which increases the reliability of the survey results. The creation of an artificial magnetic field from the masses of ferromagnetic material located in a certain order allows, when approaching unchallenged marine loading and unloading buoy terminals of the BTL and STL type, to ensure navigational safety of ships and reduces the time to exit to these stations. In this embodiment, the use of the proposed method, the magnetometers can be installed in the underwater part of the shaft lag or sonar equipment in the bow of the vessel. When the magnetometers are located in ship conditions, the created artificial magnetic field from the masses of ferromagnetic material can also be used as a cable measuring line for field tests of ship technical navigation aids (see, for example, Korablev A.E., Massarov V.F. Electromagnetic navigation systems and devices. L., VMA, p. 9).

In addition, by means of the proposed method, the search and detection of underwater objects consisting of ferromagnetic materials (iron, steel, etc.), underwater hazards (banks, reefs, rocks) containing low-magnetic materials (sand, clay, pebbles, etc.).

Information sources

1. Patent of the Russian Federation No. 2030583.

2. Systems, instruments and devices for underwater search / Zhukov RF, Kondratovich AA, Mogilny SD, Tsipko B.I. - M., Military Publishing House of the Ministry of Defense of the USSR, 1972, p. 7-9, p. 114-120.

3. Copyright certificate of the USSR No. 727007.

Claims (1)

A method for detecting underwater ferromagnetic objects, including towing two sources of a magnetic field along a survey strip with setting boundaries by dispersing ferromagnetic material formed in the form of masses of one cubic meter, located at a distance of 80-170 m from each other along the axis of the border with the formation of a quadrangle, the implementation of the alternating operation of the towed sources of the magnetic field through the control unit, registration of the total magnetic field of the towed sources and ferromagnetic ma with a primary three-component magnetic field converter, amplification and conversion of the recorded signals of the total magnetic field of the towed sources and ferromagnetic masses by a secondary converter, transmission of the amplified and converted signals of the total magnetic field of the towed sources and ferromagnetic masses to the computing unit that determines the signal due to the presence of ferromagnetic masses or underwater ferromagnetic object, signal transmission from the computing unit to the executive unit with by its next relaying to the control unit, which provides the towed sources of the magnetic field movement at the specified boundaries of the survey strip by determining the coordinates of the signal in the navigation module.

Images