Disclosure of Invention
Aiming at the defects existing in the prior art, the application provides an underwater magnetic target positioning method based on a high-order bias magnetic gradient tensor, which is easier to engineer by adopting a plane cross magnetic array structure and can be applied to the field of underwater vehicles and the environment of unknown geomagnetic fields.
The application provides an underwater magnetic target positioning method based on a high-order bias magnetic gradient tensor, which comprises the following steps:
s1, taking the position of a magnetic target as an original point O, and taking a connecting line of any point and the magnetic target as an x-axis to establish a space rectangular coordinate system O-xyz;
s2, detecting a magnetic target through a magnetic sensor module mounted in the underwater vehicle, wherein the magnetic sensor module adopts a plane cross array formed by four vector magnetic sensors, and the four vector magnetic sensors are used as four vertexes of the magnetic sensor module; operating the underwater vehicle, enabling the center point of the magnetic sensor module to be positioned at any point A, and measuring magnetic field three components of four vertexes of the magnetic sensor module in a space rectangular coordinate system O-xyz respectively;
s3, calculating magnetic field three components and magnetic gradient values of a central point A of the magnetic sensor module according to the magnetic field three components of four vertexes of the magnetic sensor module at the point A;
s4, the underwater vehicle moves to any point along the direction parallel to the x axis, the position of the central point of the magnetic sensor module is marked as a point B, and three components of magnetic fields of four vertexes of the magnetic sensor module at the point B in a space rectangular coordinate system O-xyz are measured;
s5, calculating magnetic field three components and magnetic gradient values of a center point B of the magnetic sensor module according to the magnetic field three components of four vertexes of the magnetic sensor module at the point B;
s6, the distance between the point A and the point B is marked as delta x, and the coordinates (a, B and c) of the midpoint M of the connecting line of the point A and the point B are calculated by combining the magnetic field three components and the magnetic gradient values of the point A and the point B, so that the distances of the magnetic target relative to the point B in the directions of the x axis, the y axis and the z axis are respectively a+/-delta x/2, B and c.
In some embodiments, the coordinates (a, B, c) of the midpoint M of the line between the point a and the point B in step S6 are calculated by the formula (1), where the formula (1) is:
(1);
in the formula (1), B x 、B y 、B z The magnetic field components of the A point in the directions of the x axis, the y axis and the z axis are respectively; b (B) xx 、B xy 、B xz Respectively B x Magnetic gradient values in the x-axis, y-axis and z-axis directions; b (B) yx 、B yy 、B yz Respectively B y Magnetic gradient values in the x-axis, y-axis and z-axis directions; b (B) zx 、B zy 、B zz Respectively B z Magnetic gradient values in the x-axis, y-axis and z-axis directions;
B' x 、B' y 、B' z the magnetic field components of the point B in the directions of the x axis, the y axis and the z axis are respectively; b' xx 、B' xy 、B' xz Respectively B' x Magnetic gradient values in the x-axis, y-axis and z-axis directions; b' yx 、B' yy 、B' yz Respectively B' y Magnetic gradient values in the x-axis, y-axis and z-axis directions; b' zx 、B' zy 、B' zz Respectively B' z Magnetic gradient values in the x-axis, y-axis and z-axis directions.
In some of these embodiments, the magnetic field at midpoint A at step S3 is three-component B x 、B y 、B z Calculated by (2), the magnetic field of the ith vertex of the magnetic sensor module at the point A in the directions of the x axis, the y axis and the z axis is dividedThe amounts are respectively marked as B ix 、B iy 、B iz Wherein i=1, 2, 3, 4, and formula (2) has the expression:
(2),
three components B' of the magnetic field at point B in step S4 x 、B' y 、B' z The magnetic field components of the ith vertex of the magnetic sensor module at the point B in the directions of the x axis, the y axis and the z axis are respectively marked as B' by the calculation of (3) ix 、B' iy 、B' iz Wherein i=1, 2, 3, 4, and formula (3) has the expression:
(3)。
in some of these embodiments, the magnetic gradient value B at the point A in step S3 xn 、B yn 、B zn Calculated by the formula (4), the expression of the formula (4) is:
(4),
the magnetic gradient value of the B point, B', in the step S5 xn 、B' yn 、B' zn Calculated by the formula (5), the expression of the formula (5) is:
(5),
in the formulas (4) and (5), d is a baseline distance of the planar cross array of the magnetic sensor module.
In some of these embodiments, in step S6, when the direction of movement of the underwater vehicle from point a to point B is to be in a direction approaching the magnetic target, the distance of the magnetic target relative to point B in the x-axis direction is a- Δx/2; when the moving direction of the underwater vehicle from the point A to the point B is a direction away from the magnetic target, the distance of the magnetic target relative to the point B in the x-axis direction is a+Deltax/2.
Besides, the application also provides an underwater magnetic target positioning device based on the high-order bias magnetic gradient tensor, which comprises a magnetic sensor module and a processor in communication connection with the magnetic sensor module, wherein the processor is configured to operate the underwater magnetic target positioning method based on the high-order bias magnetic gradient tensor.
In some of these embodiments, the four vector magnetic sensors of the magnetic sensor module are each connected to the processor by wires.
Based on the scheme, the underwater magnetic target positioning method based on the high-order bias magnetic gradient tensor in the embodiment of the application can realize the positioning of the magnetic target by adopting a plane cross magnetic array structure and using 4 magnetic sensors, has the characteristics of small number of the magnetic sensors, small occupied space and easy engineering, and is suitable for being applied to the field of underwater vehicles; in addition, the application eliminates errors caused by geomagnetic fields by utilizing a differential method, and can be effectively applied to the environment without knowing the geomagnetic fields.
Detailed Description
The technical solutions in the embodiments will be clearly and completely described below with reference to the drawings in the embodiments of the present application. It will be apparent that the described embodiments are only some, but not all, embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
In the application, a magnetic target refers to an object with magnetism, such as a ship, a submarine, a mine, and the like, which needs to be detected in ocean exploration.
As shown in fig. 2, the method for positioning an underwater magnetic target based on a high-order bias magnetic gradient tensor provided by the application is used for positioning a magnetic target 5 through a magnetic sensor module with a plane cross structure, and comprises the following steps:
s1, taking the position of a magnetic target 5 as an original point O, and taking the connecting line of any point and the magnetic target 5 as an x-axis to establish a space rectangular coordinate system O-xyz;
s2, detecting a magnetic target 5 through a magnetic sensor module mounted in the underwater vehicle 8, wherein the magnetic sensor module adopts a plane cross-shaped array formed by four vector magnetic sensors, the four vector magnetic sensors (specifically, a first magnetic sensor 1, a second magnetic sensor 2, a third magnetic sensor 3 and a fourth magnetic sensor 4 as shown in FIG. 3) are taken as four vertexes of the magnetic sensor module, and the central point of the plane cross-shaped array is taken as the central point of the magnetic sensor module; the center point of the magnetic sensor module is positioned at any point A, and as shown in FIG. 4 (in order to clearly show the measurement process of the magnetic sensor module, the underwater vehicle 8 and the processor 7 are not shown in FIG. 4), three magnetic field components of four vertexes of the magnetic sensor module in a space rectangular coordinate system O-xyz are measured;
s3, calculating magnetic field three components and magnetic gradient values of a central point A of the magnetic sensor module in a space rectangular coordinate system O-xyz according to the magnetic field three components of four vertexes of the magnetic sensor module at the point A obtained in the step S2;
s4, the underwater vehicle 8 moves to any point along the direction parallel to the x axis, the position of the central point of the magnetic sensor module is marked as a point B, and as shown in FIG. 4, three magnetic field components of four vertexes of the magnetic sensor module at the point B in a space rectangular coordinate system O-xyz are measured;
s5, calculating magnetic field three components and magnetic gradient values of a center point B of the magnetic sensor module according to the magnetic field three components of four vertexes of the magnetic sensor module at the point B obtained in the step S4;
s6, the distance between the point A and the point B is recorded as delta x, and the coordinates (a, B and c) of the midpoint M of the connecting line of the point A and the point B are calculated by combining the magnetic field three components and the magnetic gradient values of the point A and the point B, as shown in fig. 4, so that the distances of the magnetic target 5 relative to the point B in the directions of the x axis, the y axis and the z axis are respectively a+/-delta x/2, B and c.
In step S6, coordinates (a, B, c) of a midpoint M of the line between the point a and the point B are calculated by the formula (1), and the formula (1) is expressed as follows:
(1);
in the formula (1), B x 、B y 、B z The magnetic field components of the A point in the directions of the x axis, the y axis and the z axis are respectively; b (B) xx 、B xy 、B xz Respectively B x Magnetic gradient values in the x-axis, y-axis and z-axis directions; b (B) yx 、B yy 、B yz Respectively B y Magnetic gradient values in the x-axis, y-axis and z-axis directions; b (B) zx 、B zy 、B zz Respectively B z Magnetic gradient values in the x-axis, y-axis and z-axis directions;
B' x 、B' y 、B' z the magnetic field components of the point B in the directions of the x axis, the y axis and the z axis are respectively; b' xx 、B' xy 、B' xz Respectively B' x Magnetic gradient values in the x-axis, y-axis and z-axis directions; b' yx 、B' yy 、B' yz Respectively B' y Magnetic gradient values in the x-axis, y-axis and z-axis directions; b' zx 、B' zy 、B' zz Respectively B' z Magnetic gradient values in the x-axis, y-axis and z-axis directions.
In the above-mentioned exemplary embodiment, the underwater magnetic target positioning method based on the high-order bias magnetic gradient tensor adopts the planar cross magnetic array structure, so that the number of the magnetic sensors is small, the occupied space is small, the engineering is easier, and the method can be applied to the field of underwater vehicles and the environment of unknown geomagnetic fields.
The three components of the magnetic field measured in step S2 and step S4 are the sum of the target magnetic anomaly value and the geomagnetic field value, the target magnetic anomaly value is an inherent property of the magnetic target, the geomagnetic field in a certain region can be considered as a fixed value which does not change with time, and the error caused by the geomagnetic field is eliminated in the step S6 in the formula (1) in a differential manner.
As shown in fig. 2, the magnetic field at the midpoint a in step S3 has three components B x 、B y 、B z Calculated by the method (2), the magnetic field components of the ith vertex of the magnetic sensor module at the point A in the directions of the x axis, the y axis and the z axis are respectively marked as B ix 、B iy 、B iz Wherein i=1, 2, 3, 4, and formula (2) has the expression:
(2),
three components B' of the magnetic field at point B in step S4 x 、B' y 、B' z The magnetic field components of the ith vertex of the magnetic sensor module at the point B in the directions of the x axis, the y axis and the z axis are respectively marked as B' by the calculation of (3) ix 、B' iy 、B' iz Wherein i=1, 2, 3, 4, and formula (3) has the expression:
(3)。
as shown in FIG. 2, the magnetic gradient value B at the point A in step S3 xn 、B yn 、B zn Calculated by the formula (4), the expression of the formula (4) is:
(4),
the magnetic gradient value of the B point, B', in the step S5 xn 、B' yn 、B' zn Calculated by the formula (5), the expression of the formula (5) is:
(5),
in the formulas (4) and (5), d is a baseline distance of the planar cross array of the magnetic sensor module. It will be appreciated that the baseline distance is the distance between two opposing magnetic sensors in a planar cross array, as shown in fig. 4, where the distance between the first magnetic sensor 1 and the third magnetic sensor 3 is d and the distance between the second magnetic sensor 2 and the fourth magnetic sensor 4 is d.
In step S6, when the moving direction of the underwater vehicle 8 from the point a to the point B is a direction to approach the magnetic target 5, the distance of the magnetic target 5 relative to the point B in the x-axis direction is a- Δx/2; when the moving direction of the underwater vehicle 8 from the point a to the point B is a direction away from the magnetic target 5, the magnetic target 5 is a+Δx/2 in the x-axis direction with respect to the point B.
In addition, the application also provides an underwater magnetic target positioning device based on the high-order bias magnetic gradient tensor, which is arranged inside the underwater vehicle 8 and comprises a magnetic sensor module, and further comprises a processor 7 which is in communication connection with the magnetic sensor module, wherein the processor 7 is configured to operate the underwater magnetic target positioning method based on the high-order bias magnetic gradient tensor.
In order to ensure stable transmission between the magnetic sensor module and the processor 7, the four vector magnetic sensors of the magnetic sensor module are connected to the processor 7 through wires, respectively. It should be noted that the processor 7 may be a processor such as a computer, which is capable of running the underwater magnetic target positioning method based on the higher-order bias magnetic gradient tensor of the present application.
The underwater magnetic target positioning method based on the high-order bias magnetic gradient tensor is described below by means of a specific embodiment:
example 1
The method for positioning the underwater magnetic target based on the high-order bias magnetic gradient tensor is used for establishing a simulation parameter model, and positioning the magnetic target 5 in the simulation parameter model, and comprises the following steps:
1) Establishing a space rectangular coordinate system
Taking the position of the magnetic target 5 as an original point O, and taking the connecting line of any point and the magnetic target 5 as an x-axis to establish a space rectangular coordinate system O-xyz;
2) Operating the underwater vehicle 8, three components of the magnetic field at four vertices of the magnetic sensor module at any point A are measured by the magnetic sensor module
The magnetic field components in the x-axis, y-axis and z-axis directions of the first vertex of the magnetic sensor module at the point A (121.5,20,100) measured by the first magnetic sensor 1 are respectively B 1x =37138.604nT、B 1y =-15318.108nT、B 1z -33560.264nT; the magnetic field components of the second vertex in the x-axis, y-axis and z-axis directions measured by the second magnetic sensor 2 are respectively B 2x =37201.123nT、B 2y =-15322.817nT、B 2z -33479.872nT; the magnetic field components of the third vertex in the x-axis, y-axis and z-axis directions measured by the third magnetic sensor 3 are respectively B 3x =37173.631nT、B 3y =-15408.516nT、B 3z -33469.357nT; the magnetic field components of the fourth vertex in the x-axis, y-axis and z-axis directions measured by the fourth magnetic sensor 4 are respectively B 4x =37110.717nT、B 4y =-15402.984nT、B 4z =-33550.586nT;
3) Calculating magnetic field three-component and magnetic gradient value of A point in space rectangular coordinate system O-xyz by processor 7
Calculating the magnetic field three-component B at the point A by the method (2) x =37156.01875nT、B y =-15363.106nT、B z -33515.020nT; calculated by the formula (4), B x Magnetic gradient values in the x-axis, y-axis and z-axis directions are B xx =-35.027nT/m、B xy =90.406nT/m、B xz =-90.907nT/m;B y Magnetic gradient values in the x-axis, y-axis and z-axis directions are B yx =90.408nT/m、B yy =80.167nT/m、B yz =70.714nT/m;B z Magnetic gradient values in the x-axis, y-axis and z-axis directions are B zx =-90.907nT/m、B zy =70.714nT/m、B zz =-45.14nT/m;
4) The underwater vehicle 8 moves to any point along the direction parallel to the x-axis, the center point position of the magnetic sensor module is marked as a point B, and three components of the magnetic fields of four vertexes of the magnetic sensor module at the point B are measured
The underwater vehicle 8 moves to an arbitrary point in a direction parallel to the x-axis toward the magnetic target 5, and the center point position of the magnetic sensor module is denoted as point B, and the movement distance is Δx=1m. The magnetic field components of the first vertex of the magnetic sensor module at point B (120.5,20,100) measured by the first magnetic sensor 1 in the x-axis, y-axis and z-axis directions are B 1x =37173.631nT、B' 1y =-15408.516nT、B' 1z -33469.357nT; the magnetic field components of the second vertex in the x-axis, y-axis and z-axis directions are measured by the second magnetic sensor 2 as B', respectively 2x =37236.782nT、B' 2y =-15413.059nT、B' 2z -33387.251nT; the magnetic field components of the third vertex in the x-axis, y-axis and z-axis directions are measured by the third magnetic sensor 3 as B', respectively 3x =37208.547nT、B' 3y =-15500.303nT、B' 3z -33376.64nT; the magnetic field components of the fourth vertex in the x-axis, y-axis and z-axis directions are measured by the fourth magnetic sensor 4 as B', respectively 4x =37144.998nT、B' 4y =-15494.923nT、B' 4z =-33459.602nT;
5) Calculating magnetic field three-component and magnetic gradient value of B point in space rectangular coordinate system O-xyz by processor 7
The three components B' of the magnetic field at the point B are calculated by the method (3) x =37190.9895nT、B' y =-15454.20025nT、B' z -33423.2125nT; calculated by equation (5), B' x Magnetic gradient values in the x-, y-and z-directions are B' xx =-34.916nT/m、B' xy =91.784nT/m、B' xz =-92.717nT/m;B' y Magnetic gradient values in the x-, y-and z-directions are B' yx =91.787nT/m、B' yy =81.864nT/m、B' yz =72.351nT/m;B' z Magnetic gradient values in the x-, y-and z-directions are B' zx =-92.717nT/m、B' zy =72.351nT/m、B' zz =-46.948nT/m;
6) Calculating the midpoint coordinate between the points AB by combining the distance between the points A and B, and further obtaining the position data of the magnetic target 5 relative to the point B
The coordinates (a, B, c) of the midpoint M of the line between the a point and the B point are calculated by the formula (1) to be (121.1384, 19.9273, 99.8836), and the distance of the magnetic target 5 to the B point in the x-axis direction is a- Δx/2= 120.6384M, the distance of the magnetic target 5 to the B point in the y-axis direction is b= 19.9273M, and the distance of the magnetic target 5 to the B point in the z-axis direction is c= 99.8836M.
Comparative example 1
The magnetic sensor module of the planar cross structure array is established by adopting the linear relation between the magnetic dipole position information, the magnetic field vector at the position and the magnetic gradient tensor matrix, which is proposed by the document Moore Penrose generalized inverse of the gradient tensor in Euler's equation forlocating a magnetic dipole (the magnetic dipole is positioned by the inverse of the gradient tensor in the Euler equation promoted by Mole and Penrose), the magnetic dipole is positioned by the inverse of the gradient tensor in the Euler equation, and the simulation parameter model established in the embodiment 1 is positioned.
Comparative example 2
The simulation parameter model established in example 1 is positioned by adopting a high-order bias magnetic gradient positioning algorithm based on a regular hexahedron structure, which is proposed in paper 'target positioning improvement method based on magnetic gradient tensor'.
Fig. 5 shows a comparison of errors of a plurality of sets of data, respectively measured by the method of comparative example 1 and the method of example 1, in which the distance between the center point of the magnetic sensor module and the magnetic target is within 150m, and as can be seen from fig. 4, the positioning error of example 1 of the present application is much smaller than that of comparative example 1 in the presence of the interference of the geomagnetic field.
Fig. 6 shows a comparison of errors of sets of data, respectively measured with the method of comparative example 2 and the method of example 1, in which the distance between the center point of the magnetic sensor module and the magnetic target is within 150m, and as can be seen from fig. 5, the positioning error of example 1 of the present application is substantially the same as that of comparative example 2.
By way of illustration of various embodiments of the high order bias magnetic gradient tensor-based underwater magnetic target positioning method of the present application, it can be seen that the high order bias magnetic gradient tensor-based underwater magnetic target positioning method embodiments of the present application have at least one or more of the following advantages:
1. the underwater magnetic target positioning method based on the high-order bias magnetic gradient tensor provided by the application adopts four magnetic sensors to form a plane cross array, so that the number of the magnetic sensors is reduced, the occupied space is reduced, the cost is saved, and the engineering application is facilitated;
2. the underwater magnetic target positioning method based on the high-order bias magnetic gradient tensor effectively eliminates the interference of the geomagnetic field by a differential method, and improves the positioning precision and stability.
Finally, it should be noted that: in the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other.
The above embodiments are only for illustrating the technical solution of the present application and not for limiting the same; while the application has been described in detail with reference to the preferred embodiments, those skilled in the art will appreciate that: modifications may be made to the specific embodiments of the present application or equivalents may be substituted for part of the technical features thereof; without departing from the spirit of the application, it is intended to cover the scope of the application as claimed.