RU2069374C1 - Method of vector magnetic measurements - Google Patents

Abstract

FIELD: magnetic measurements, can be used in search for minerals and magnetic map-making. SUBSTANCE: in the process of carrier course turns and rolling oscillations orthogonal components of magnetic induction, angular coordinates and carrier angular velocities are measured and memorized, components of the carrier constant magnetic field, inductive and vortex coefficients of carrier noise are determined, earth's magnetic field in the geographic coordinate system at known values of carrier noise is determined; at measurements working route the increments of the carrier constant field are measured, and the previously measured values of the carrier constant field are corrected. EFFECT: facilitated procedure. 2 dwg

Description

 The invention relates to the field of magnetic measurements and is intended for the search and exploration of minerals and magnetic mapping.

 A known method of magnetic measurements, [1] including measuring the parameters of magnetic induction at different courses with periodic evolution of the carrier along the angles of longitudinal and transverse rolls, simultaneous measurement of angles and angular frequency of rolls, determination of interference coefficients of constant and inductive magnetization of the carrier and eddy current interference, as well compensation of carrier noise by means of compensation rings fed by signals from the output of the auxiliary component magnetometer.

 The disadvantage of this known method is its low accuracy. Only a part of the magnetic interference of the carrier can be determined separately, most of the components of the interference can be determined only as a sum or as a difference. This is not enough to reduce carrier noise in vector measurements.

 The purpose of the invention is improving accuracy.

 This goal is achieved by the fact that in the method of vector magnetic measurements, including preliminary turns of the carrier along the course with fluctuations in the angles of longitudinal and transverse rolls, simultaneous measurement and storage of three mutually orthogonal KMI in the coordinate system of the carrier, as well as the angular coordinates and angular velocities of the carrier, determination and storing KMI SP and coefficients of inductive and vortex noise of the carrier by expanding the measured KMI in a system of functions, including the functions of angular coordinates and angular velocities th carrier, measuring and storing the same parameters on the working route and determining the KMI of the Earth’s magnetic field by decomposing the KMI in the same system of functions with known values of the KMI PP and carrier noise factors, in addition, during long-term movement along the route, the same parameters are measured and stored in the process yaw of the carrier along the course and fluctuations in the angles of the longitudinal and transverse rolls, in the process of processing the information, determine the increments of the KMI of the medium of the carrier, correct their previously obtained values and determine the KMI of magnesium Earth's field at the corrected values of the KMI PP of the carrier.

 In FIG. 1 shows a functional diagram of one of the possible variants of the device for implementing the method; in FIG. 2 coordinate systems.

 The device comprises a three-component magnetometer 1, an inertial navigation system 2, a block of angular velocity sensors 3, a computer 4 and a synchronization unit 5.

 The outputs of the three-component magnetometer 1, inertial navigation system 2 and the block of angular velocity sensors 3 are connected, respectively, with the first, second and third inputs of the computer 4. The synchronizing inputs of the blocks 1-4 are connected to the output of the synchronization block 5.

The three-component magnetometer 1 (Fig. 1), made in the form of a three-component digital fluxgate magnetometer, is mounted on the carrier so that its measuring axes are parallel to the coordinate axes of the OXYZ carrier (see Fig. 2). From the output of the three-component magnetometer 1, the electrical signals in the form of KMI codes Bx, By and Bz are received at the first input of the computer 4. Simultaneously with the output of the inertial navigation system 2, signals are sent to the second input of the computer 4 in the form of codes of the angular coordinates of the carrier relative to the geographical coordinate system Olmn. The block of angular velocity sensors, made in the form of three float gyrotachometers, the measuring axes of which are oriented parallel to the coordinate axes X, Y, Z of the carrier, form electrical signals in the form of voltages proportional to the components of the angular velocity of the carrier ω _x , ω _y and ω _z , which after conversion the codes go to the third input of the computer 4.

 Consider the mathematical relationships underlying the method.

представляет собой сумму магнитного поля Земли и магнитного поля носителя, обусловленного постоянным и индуктивным намагничением ферромагнитных масс и магнитным полем вихревых токов:

(1)
Здесь:

вектор магнитной индукции постоянного поля носителя /Bрх, Bpy, Bpz/;
В вектор магнитной индукции магнитного поля Земли /B_l, B_m, B_n/;
А матрица преобразования из географической системы координат Olmn в систему координат носителя;
Е единичная диагональная матрица;
D матрица тензора индуктивных коэффициентов dij;
F матрица тензора вихревых коэффициентов fij.Measured on the carrier magnetic field

represents the sum of the Earth’s magnetic field and the carrier’s magnetic field, due to the constant and inductive magnetization of the ferromagnetic masses and the eddy currents magnetic field:

(one)
Here:

vector of the magnetic induction of a constant field of the carrier / Br, Bpy, Bpz /;
In the vector of magnetic induction of the Earth's magnetic field / B _l , B _m , B _n /;
And the transformation matrix from the geographical coordinate system of Olmn to the coordinate system of the carrier;
E is the unit diagonal matrix;
D matrix of the tensor of inductive coefficients dij;
F is the matrix of the vortex coefficient tensor fij.

(2)
В этой зависимости элементы а_ju матрицы А и их производные по времени

суммируются по индексам j и u c весовыми коэффициентами С и С', заданными соотношением (3):
C $\genfrac{}{}{0ex}{}{\text{i}}{\text{ju}}$ = (C_ij+d_ij)B_ui; C $\genfrac{}{}{0ex}{}{\text{1i}}{\text{ju}}$ = f_ijB_u (3)
Здесь: Bu КМИ магнитного поля Земли в географической системе координат /B_l, B_m и B_п/;
C_ij, d_ij, f_ij элементы матриц Е, D и F.The corresponding expression for the KMI can be represented by the dependence (2):

(2)
In this dependence, the elements a _{ju of the} matrix A and their derivatives with respect to time

are summed over the indices j and uc by the weighting coefficients C and C 'given by the relation (3):
C $\genfrac{}{}{0ex}{}{\text{i}}{\text{ju}}$ = (C _ij + d _ij ) B _ui ; C $\genfrac{}{}{0ex}{}{\text{1i}}{\text{ju}}$ = f _ij B _u (3)
Here: Bu KMI of the Earth's magnetic field in the geographical coordinate system / B _l , B _m and B _p /;
C _ij , d _ij , f _ij elements of the matrices E, D and F.

 The content of the method consists of the following operations and their sequence.

 1. Preliminary turns on the course with fluctuations in the angles of the longitudinal and transverse rolls with simultaneous measurement and storage of three mutually orthogonal KMI in the coordinate system of the carrier, as well as the angular coordinates and angular velocities of the carrier.

 2. Determination and memorization of the KMI PP and the coefficients of inductive and vortex noise of the carrier by expanding the measured KMI in a system of functions, including the functions of the angular coordinates and angular velocities of the carrier.

 3. Measurement and storage of parameters according to paragraph 1 on the working route.

 4. Determination of the KMI of the Earth's magnetic field by decomposing the KMI according to the same system of functions with known values of the KMI PP and carrier interference coefficients.

 5. Measurement and storage of parameters according to paragraph 1 on the working route in the process of yawing the carrier at the heading and fluctuations in the angles of the longitudinal and transverse rolls.

 6. The determination of increments KMI PP media and the adjustment of previously obtained values.

 7. Determination of the KMI of the Earth's magnetic field with the corrected values of the KMI PP and carrier interference factors.

 As a specific example of the implementation of the method, we consider the principle of the device for its implementation.

(4)
K 1,2,n,
cвободными числами которой служат измеренные значения КМИ, а элементы матриц

вычисляются в соответствии с измеренными угловыми координатами и угловыми скоростями. Общее число измерений существенно превышает число неизвестных, и переопределенная система уравнений (4) решается на основе метода наименьших квадратов. В результате решения определяются КМИ ПП носителя Bp_i, а также значения коэффициентов

, после чего составляются системы уравнений (5):

и в результате решения этой системы уравнений по методу наименьших квадратов определяются коэффициенты индуктивных и вихревых помех dij и fij, а также КМИ в географической системе координат B_l, B_m, B_n. Значения КМИ ПП носителя Bp_i, а также значения индуктивных и вихревых коэффициентов заносятся в память ЭВМ, и на этом операция 2 завершается.At the operator’s command, the carrier begins to turn heading with simultaneous fluctuations in the angles of the longitudinal and transverse rolls. At the same time, through the synchronization unit 5, the operator turns on the computer 4 in the information collection mode. At fixed intervals of time, according to the signals of the synchronization unit 5, the KMI values B _x , B _y and B _z , the values of the angular coordinates and the angular velocities of the carrier ω _x , ω _y and ω _z are simultaneously transmitted to the computer inputs and are entered into the computer memory block. After the media is rotated at the rate of 360 ^{o, the} preliminary operation 1 of collecting and storing information is completed and, upon the command of the synchronization unit, the computer switches to the mode of determining and storing interference coefficients (operation 2). In accordance with the information received on the program recorded in the computer memory, the system of equations (4) is compiled:

(4)
K 1,2, n,
the free numbers of which are the measured values of the KMI, and the elements of the matrices

are calculated in accordance with the measured angular coordinates and angular velocities. The total number of measurements significantly exceeds the number of unknowns, and the overdetermined system of equations (4) is solved on the basis of the least squares method. As a result of the decision, the KMI of the carrier medium Bp _i , as well as the values of

, after which the systems of equations (5) are compiled:

and as a result of solving this system of equations using the least squares method, the coefficients of inductive and vortex noise dij and fij are determined, as well as the KMI in the geographical coordinate system B _l , B _m , B _n . The values of the KMI PP of the carrier Bp _i , as well as the values of the inductive and vortex coefficients, are recorded in the computer memory, and this completes the operation 2.

In the process of vector measurements on the working route, on a small portion of the route, within which the magnetic flux density vector of the Earth’s magnetic field can be considered unchanged, synchronous measurements of the CMI B _x , B _y and B _z , angular coordinates and angular velocities of the carrier are performed according to the signal and the measured values at time intervals specified by the synchronization unit are recorded in the computer memory. This third operation is similar to operation 1. The difference is that the measurements are performed during movement along a given route. The minimum number of measurements required is one. To reduce the influence of random errors, the number of measurements can be increased to tens, while it is necessary that the length of the route does not exceed the established limit, taking into account the gradient of magnetic induction. After completion of operation 3, the synchronization unit switches the computer to the determination mode of the KMI of the Earth’s magnetic field (operation 4). According to the program recorded in the computer memory, in accordance with the information obtained during the third operation, a system of equations (4) is compiled for the known values of the KMI of the constant field of the carrier and the known values of inductive and vortex coefficients taking into account dependence (3). As a result of solving the system of equations (4) on the basis of the least squares method, the computer output, which is the output of the entire device, generates KMI codes of the Earth’s magnetic field B _l , B _m and B _n in the geographic coordinate system, free of carrier magnetic interference. This completes the operation 4. With further movement along the route, operations 3 and 4 are repeated at a frequency specified by the synchronization unit.

(6)
K 1,2,n
В результате решения системы уравнений (6) на основе метода наименьших квадратов определяются приращения КМИ постоянного поля носителя ΔB_pi и в память ЭВМ заносится откорректированные с учетом измеренных приращений значения КМИ ПП носителя.If, after the execution of operations 1 and 2, the composition of the carrier’s cargoes has changed, electrical equipment has been switched over or the carrier has been moving along the same course for a long time, there will be changes in the KMI of the carrier’s media and the errors of magnetic measurements will increase. In order to reduce errors directly on the working route, measurements are taken and information is stored in the same way as operation 3 in the process of yawing the carrier along the course and fluctuations in the angles of the longitudinal and transverse rolls within units of degrees / operation 5 /. After the operation is completed, the synchronization unit switches the computer to the mode of determining increments of the KMI of the carrier medium and adjusting previously measured values / operation 6 /. According to the program recorded in the computer memory, in accordance with the information recorded during the 5th operation, a system of equations (4) is compiled for the known values of inductive and vortex coefficients, and KMI PP are represented as the sum of KMI Bp _i stored in the computer memory , and unknown KMI increments ΔB _pi 6

(6)
K 1,2, n
As a result of solving the system of equations (6) on the basis of the least squares method, the increments of the KMI of the constant field of the carrier ΔB _{pi are} determined and the values of the KMI of the carrier are corrected taking into account the measured increments.

 In the process of further movement along the working route, measurements of the KMI of the Earth’s magnetic field are carried out with the corrected values of the KMI PP of the carrier / operation 7 /. This operation is performed similarly to operations 3 and 4.

 If the media path has changed during the magnetic survey or it is necessary to control changes in the magnetic field of the carrier, then steps 5 and 6 are repeated and the KMI PP of the carrier is again corrected.

 As a result of these operations, errors due to changes in the magnetic field of the carrier are reduced, and this does not require repeating the full cycle of labor-intensive measurements of the preparatory / first / operation in the area with a low gradient level.

Claims (1)

 The method of vector magnetic measurements with preliminary and repeated periodic determinations of the magnetic interference of the carrier, including turning the carrier along the course with fluctuations in the angles of the longitudinal and transverse rolls, simultaneous measurement and storage of three orthogonal components of magnetic induction (KMI) in the coordinate system of the carrier, as well as the angular coordinates and angular velocity of the carrier, determination and storage of the KMI of the constant field of the carrier (PP), as well as the coefficients of inductive and vortex noise of the carrier by decomposing I measured the KMI by the system of fractions, including the functions of the angular coordinates and angular velocities of the carrier, measuring and storing three orthogonal KMI in the coordinate system of the carrier, as well as the angular coordinates and angular velocities of the carrier on the working route and determining the KMI of the Earth’s magnetic field by decomposing the KMI according to the same a system of functions with known values of KMI PP and carrier noise factors, characterized in that, in order to improve accuracy, in addition to the intervals between successive determinations of carrier magnetic interference when moving along the working route, three orthogonal KMIs are measured and stored in the coordinate system of the carrier, as well as the angular coordinates and angular velocities of the carrier in the course of yawing the carrier along the course and fluctuations in the angles of the longitudinal and transverse rolls, according to which the increments of the KMI of the carrier PP are determined, taking into account which correct their previously obtained values and determine the KMI of the Earth's magnetic field with the corrected values of the KMI PP of the carrier.

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