CN114577100B - Magnetic field target positioning calculation method - Google Patents
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/004—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring coordinates of points
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B34/00—Computer-aided surgery; Manipulators or robots specially adapted for use in surgery
- A61B34/20—Surgical navigation systems; Devices for tracking or guiding surgical instruments, e.g. for frameless stereotaxis
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C1/00—Measuring angles
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- G—PHYSICS
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- G06F17/10—Complex mathematical operations
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B34/00—Computer-aided surgery; Manipulators or robots specially adapted for use in surgery
- A61B34/20—Surgical navigation systems; Devices for tracking or guiding surgical instruments, e.g. for frameless stereotaxis
- A61B2034/2046—Tracking techniques
- A61B2034/2051—Electromagnetic tracking systems
Abstract
The invention discloses a magnetic field target positioning calculation method. According to the calculation method of the present invention, the exciting coil for generating the magnetic field is divided into exciting coil sub-blocks. And each excitation coil sub-block is used as a current element, so that the magnetic induction intensity of each excitation coil sub-block at any point P in space is calculated. The magnetic induction intensity of any point P in the space of each excitation coil sub-block is overlapped to obtain the relationship between the magnetic induction intensity generated by the whole excitation coil in the space and the space position and direction. And obtaining the position and the direction of the target positioning device based on the acquired magnetic induction intensity signals at the target positioning device and the relationship between the magnetic induction intensity generated by the exciting coil in space and the space position and the direction. The magnetic field target positioning technology can be used in medical operation, in particular interventional operation. Moreover, the positioning calculation method is more universal, and the shape of the cross section of the exciting coil is not limited to be circular.
Description
Technical Field
The invention relates to an electromagnetic field, in particular to a magnetic field target positioning calculation method.
Background
In modern medical technology, living body tissues can be treated by accessing consumable materials such as catheters, sheaths and the like into the living body. However, in surgery, it is necessary to precisely locate and track a target object such as a catheter, a guidewire, an introducer (sheath), or a probe. When interventional therapy is performed on different biological tissues, the positioning accuracy requirements are different, and generally, the higher the accuracy is, the better the positioning accuracy is.
Since the target such as a catheter is usually introduced into the living body through a blood vessel, a digestive tract and the like, the size of the target is designed to be smaller, and if a positioning device with a certain size is additionally added, the target cannot meet the requirement of the intervention in the living body in size. In addition, although the position of the target object may be observed by means of images such as X-rays, magnetic resonance imaging, etc., such a position often does not meet the positioning accuracy requirements at the surgical level.
Therefore, in medical applications, particularly interventional procedures, magnetic field target localization techniques may be employed in order to be able to ensure as much accuracy as possible of localization without taking up too much of the target size.
When the magnetic field target positioning technology is applied, the position and the direction of a target object are solved according to a system of equations of the Biot-Savart Law. In general, when the cross-sectional shape of an exciting coil for generating a magnetic field is circular, it can be equivalent to a magnetic dipole. For the target object, the target positioning device for magnetic induction intensity acquisition is usually a sensor coil, and can be equivalently a magnetic dipole. Since both the excitation coil and the sensor coil are equivalent to magnetic dipoles, the solution process is simplified. However, the above equivalent is provided that the cross-sectional shape of the exciting coil must be circular, and if other shapes are used, such equivalent cannot be applied, and thus the simplified solution method cannot be used to perform the magnetic field target positioning calculation.
Therefore, it is desirable to provide a more generally applicable magnetic field target positioning calculation method, which breaks through the limitation that the cross-sectional shape of the exciting coil is circular, so that the method can be more widely applied to magnetic field target positioning, and still ensure the positioning accuracy.
Disclosure of Invention
The invention provides a more universal positioning calculation method for various cross-sectional shapes of exciting coils. According to the calculation method of the invention, the exciting coil with any cross section shape can be divided into smaller sub-blocks, each sub-block is used as a current element, then the magnetic induction intensities of all the sub-blocks in the space are overlapped to obtain the magnetic induction intensity of any point in the space, and the position and the direction of the target positioning device, such as a three-dimensional coordinate, a pitch angle and a rotation angle, can be obtained by solving the following equation by comparing the magnetic induction intensity on the acquired target sensor coil.
According to a first aspect of the present invention, a method for magnetic field target location calculation is provided. The method may include: dividing an exciting coil for generating a magnetic field into exciting coil sub-blocks; taking each excitation coil sub-block as a current element, and calculating the magnetic induction intensity of each excitation coil sub-block at any point P in space; superposing the magnetic induction intensity of any point P of each excitation coil sub-block in space to obtain the relationship between the magnetic induction intensity generated by the whole excitation coil in space and the space position and direction; and obtaining the position and the direction of the target positioning device based on the acquired magnetic induction intensity signals at the target positioning device and the relation between the magnetic induction intensity generated by the exciting coil in space and the space position and the direction.
In the method according to the first aspect of the present invention, preferably, the magnetic induction intensity of the excitation coil sub-block at any point P in space is obtained based on the biot-savart law, based on the position and arrangement direction of each excitation coil sub-block as a current element, and the current intensity of the excitation coil sub-block.
In the method according to the first aspect of the present invention, preferably, the exciting coil is divided into M segments in the axial direction to obtain M sub-coil pieces, and the contour is segmented after the sub-coil pieces are equivalent to the contour of the sub-coil pieces. And calculating the magnetic induction intensity component of each section of the contour at any point P in the magnetic field by using the Biao-Saval law. Superposing magnetic induction intensity components of each section of the contour at P to obtain the magnetic induction intensity of the contour at P; and (3) superposing the magnetic induction intensities of the M outlines in the axial direction to obtain the magnetic induction intensity of the exciting coil in the P, thereby obtaining the relationship between the magnetic induction intensity generated by the whole exciting coil in space and the spatial position and direction. Listing magnetic induction intensity of a sensor coil of the target positioning device in the direction of a P normal vector according to an electromagnetic induction law, wherein the normal vector refers to a normal unit vector of a section of the sensor coil; and listing a magnetic induction electromotive force equation according to the principle that the magnetic induction intensity of the exciting coil at P is equal to the magnetic induction intensity of the sensor coil at the normal vector of P, so as to solve and obtain the position and the direction of the target positioning device.
In the method according to the first aspect of the invention, preferably, the profile may be a closed profile.
In the method according to the first aspect of the invention, preferably, the profile may be constituted by arc segments and straight segments.
In the method according to the first aspect of the present invention, preferably, the shape of the outline may be a rounded rectangle.
In the method according to the first aspect of the invention, preferably, the profile may be circular in shape.
In the method according to the first aspect of the invention, the target positioning device may preferably be located on a medical device for medical intervention into the living being.
In the method according to the first aspect of the present invention, preferably, the position and orientation of the target positioning device may comprise three-dimensional coordinates, pitch angle and rotation angle of the target positioning device.
In the method according to the first aspect of the invention, preferably, the magnetic field is generated using a plurality of magnetic field generators fixed to the fixture. Each magnetic field generator is arranged at a different position or in a different arrangement direction to generate a corresponding magnetic field. Each magnetic field generator comprises the field coil.
In the method according to the first aspect of the invention, preferably the plurality of magnetic field generators is at least 6 magnetic field generators.
In the method according to the first aspect of the invention, preferably the acquired magnetic induction signals at the target positioning device comprise respective magnetic induction signal components for each magnetic field generator acting on the target positioning device.
In the method according to the first aspect of the present invention, preferably, a system of magneto-inductive electromotive force equations is listed based on the respective magneto-inductive intensity signal components each magnetic field generator acts on the target positioning device and the relationship of the magneto-inductive intensity generated in space by the exciting coil of each magnetic field generator to the spatial position and direction, thereby solving the position and direction of the target positioning device.
In the method according to the first aspect of the present invention, preferably, a modulus value of the signal component is calculated; obtaining signal components with maximum and/or minimum modulus values, and removing equations corresponding to the signal components; and forming the rest equations into an optimal overdetermined equation set, and solving the position and the direction of the target positioning device.
In the method according to the first aspect of the present invention, it is preferable that the signal components are equally divided into a plurality of groups (for the reason that the positions are expressed by XYZ three-dimensional coordinates, and that each three coils XYZ are combined into one group, and thus divided into four groups, the sum of the three moduli of each group is judged to be the most preferable), and the sum of the signal moduli of each group is calculated; comparing the sum of the signal moduli of all the groups to obtain a signal component group with the maximum and/or minimum sum of the moduli, and removing the equation corresponding to the signal component group; and forming the rest equations into an optimal overdetermined equation set, and solving the position and the direction of the target positioning device.
In the method according to the first aspect of the invention, the position and orientation of the target positioning device is preferably solved iteratively according to the Levenberg-Marquardt (LM) algorithm or a modified version thereof.
According to a second aspect of the present invention there is provided a computer readable medium having stored thereon instructions executable by a processor, which instructions, when executed by the processor, cause the processor to perform a magnetic field target location calculation method as in the first aspect of the present invention.
The invention provides a magnetic field target positioning calculation method by utilizing an electromagnetic field positioning principle. The method can be particularly used in medical operations, particularly interventional operations, and can ensure the positioning accuracy as much as possible under the condition of excessively occupying the size of the target object.
In magnetic field positioning applications, the excitation coil for generating the magnetic field and the sensor coil of the target positioning device may be equivalent to magnetic dipoles. This equivalent setting allows for a quick and approximate solution to the target positioning when the cross-sectional shape of the field coil is circular. However, when the cross-sectional shape of the exciting coil is not a circle but another shape, the equivalent setting of the magnetic dipole cannot be applied any more.
The invention provides a more universal positioning calculation method for various cross-sectional shapes of exciting coils. According to the calculation method of the invention, the exciting coil with any cross section shape can be divided into smaller sub-blocks, each sub-block is used as a current element, then the magnetic induction intensities of all the sub-blocks in the space are overlapped to obtain the magnetic induction intensity of any point in the space, and the magnetic induction intensity is compared with the magnetic induction intensity on the acquired target sensor coil, so that the position and the direction of the target positioning device can be obtained by solving the following equation.
In addition, for the overdetermined equation set, more accurate equations of the calculation result can be reserved, inaccurate equations are removed, and therefore an appropriate number of equations are reserved for more accurate positioning calculation.
Similarly, the system of equations may also be solved iteratively using the Levenberg-Marquardt (LM) algorithm, or a modified version thereof.
Drawings
The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings, wherein like elements are numbered alike, wherein:
FIG. 1 is a schematic diagram of a magnetic field target positioning system.
Fig. 2 is a schematic diagram of a magnetic field generating device.
Fig. 3 is a schematic diagram of magnetic field target localization.
Fig. 4 is a flowchart of a magnetic field target positioning calculation method according to an embodiment of the invention.
Fig. 5 is a flowchart of a method of constructing a magneto-inductive electromotive force equation according to an embodiment of the present invention.
Fig. 6 is a schematic diagram of coordinates of an excitation coil using a cartesian coordinate system according to an embodiment of the invention.
Fig. 7 is a schematic view of an excitation coil having a rectangular cross section with rounded corners according to an embodiment of the invention.
Fig. 8 is a schematic view of an excitation coil having a rounded triangle cross-section according to an embodiment of the invention.
Fig. 9 is a schematic view of an excitation coil having another rounded rectangle in cross section according to an embodiment of the invention.
FIG. 10 is a flow chart of an iterative solution of target position and orientation in accordance with an embodiment of the invention.
Detailed Description
The technical scheme of the present invention will be described in further detail below by way of examples with reference to the accompanying drawings, but the present invention is not limited to the following examples.
The general principle of magnetic field target localization is first described below.
According to one embodiment of the invention, the magnetic field target positioning calculation method is implemented by first generating a magnetic field in space and then collecting magnetic induction signals of the target positioning device.
The generation of the magnetic field can be divided into two aspects of magnetic field generation control and magnetic field generation. In a preferred embodiment of the invention, it may involve the use of alternating current, collimated current or permanent magnet rotation to drive the generation of the magnetic field. The magnetic field may be generated using a plurality of magnetic field generators secured to the fixture. Each magnetic field generator is arranged at a different position or in a different arrangement direction to generate a corresponding magnetic field. Each magnetic field generator includes an excitation coil. In a preferred embodiment, the magnetic field generator may be at least 6 magnetic field generators. The shape of the magnetic field generator can be adjusted according to the application, and is usually cylindrical, square or polygonal. The relative placement position of the magnetic field generator can be adjusted according to the positioning area range of the target object. The placement angle of the magnetic field generator can be adjusted according to the amplitude of the acquisition signal of the target object.
It will be appreciated by those skilled in the art that although terms such as "magnetic field generator," "exciter coil," etc. are used in the present invention to describe the means for generating the various levels of magnetic field in space, other similar terms such as magnetic generating units, magnetic generators, magnetic generating coils, spacers, etc. may also be used to express the same or similar meaning.
The target positioning device is positioned in a magnetic field generated by the exciting coil to generate a magnetic induction signal. According to an embodiment of the invention, the object positioning device is a positioning sensor coil. The object positioning device is mounted on or in the object to be positioned. Thus, the position and orientation of the target object is determined at the same time as the position and orientation of the positioning sensor coil are determined. In a preferred embodiment, the target positioning device is located on a medical device for medical intervention into the living being. For example, the target may be a catheter, or more specifically, one or more electrodes on the catheter; a target positioning device is also mounted on the catheter adjacent the electrode for positioning the catheter or electrode.
The position and orientation of the target positioning device includes three-dimensional coordinates, pitch angle and rotation angle of the target positioning device. More generally, the orientation of the object-locating device may also include a roll angle, but in applications of the present invention, this dimension of roll angle is not a concern.
As mentioned above, the magnetic induction signal is generated at the object positioning means, i.e. the positioning sensor coil, due to the presence of the magnetic field. The magnetic induction signal is acquired for analysis, thereby enabling positioning of the target positioning device.
The positioning calculation is the problem to be solved by the invention. In general, the positioning calculation is performed by using the distribution of the generated magnetic field, and according to the acquired corresponding magnetic induction signal of each exciting coil acting on the target positioning device, an equation set is established based on the Biot-Savart Law, so as to solve the position and the direction of the target positioning device.
Those skilled in the art will appreciate that the positioning calculation can be implemented in software, i.e., entirely by algorithm programming, on a general purpose computer to perform the described calculation operations. The positioning calculation may also be implemented in hardware or firmware, i.e. by programming in a special hardware processor such as a Field Programmable Gate Array (FPGA), an Application Specific Integrated Circuit (ASIC), or a Digital Signal Processor (DSP).
The magnetic field target positioning calculation method according to the embodiment of the invention is explained in more detail below by means of the accompanying drawings.
FIG. 1 is a schematic diagram of a magnetic field target positioning system.
As shown in fig. 1, the magnetic field object localization system 100 comprises a magnetic field generating device 101. The magnetic field generating device 101 comprises a plurality of magnetic field generator sets 102A, 102B, 102C, 102D, each comprising one or more magnetic field generators. For example, each magnetic field generator group includes 3 magnetic field generators for generating magnetic fields. The system 100 further comprises a signal acquisition module 107 for acquiring the modulated signals in the generated magnetic field, a magnetic field generation control module 108 whose main function is to modulate the signals to drive the magnetic field generator to generate the magnetic field, and a positioning calculation module 109 for solving the position and direction of the object. As previously mentioned, the positions described herein may be represented in three-dimensional coordinates, while the directions described herein may be represented in pitch and rotation angles. The object positioning device (also called sensor or detector) 103 is located on the object and has the function of detecting the magnetic field, i.e. the magnetic induction signal can be generated in the magnetic field by positioning the sensor coil. One end of the cable 104 is connected to the target positioning device 103 and the other end is connected to the signal acquisition module 107. One end of the cable 105 is connected to the magnetic field generating device 101, and the other end is connected to the magnetic field generation control module 108. The system 100 may further comprise a display 106 for displaying the magnetic induction signals acquired by the signal acquisition module 107 or the positioning information calculated by the positioning calculation module 109. For example, as shown in fig. 1, displayed on the display 106 are the three-dimensional coordinates, the pitch angle, and the numerical value of the rotation angle of the target positioning device 103 (i.e., the target object).
Generally, at least 6 magnetic field generators should be arranged in the magnetic field generating device in order to establish the solving position and angle of the equation set. Here, 12 magnetic field generators are described as an example. The external shape of the magnetic field generator may be designed in a cylindrical shape, a square shape, or various other shapes.
Furthermore, it will be appreciated by those skilled in the art that although the magnetic field generator (and thus the magnetic field generating device) and the magnetic field generating control module are described herein as two components of a magnetic field target positioning system, in many cases the magnetic field generator and the magnetic field generating control module may be integrated together. Thus, the present invention does not limit the physical separation or integration of the magnetic field generator and the magnetic field generation control module, but merely distinguishes between functions. In other words, in embodiments where the magnetic field generator is integrated with the magnetic field generation control module, the relationship of the two may be regarded as hardware and its driven relationship, or the integration of the two may be regarded as a kind of firmware.
Fig. 2 is a schematic diagram of a magnetic field generating device. As shown in fig. 2, the magnetic field generating device 201 includes magnetic field generator groups 202A, 202B, 202C, 202D each including 3 magnetic field generators orthogonal to each other. The internal structure 204 of the magnetic field generator set 202A is illustrated as an example. The magnetic field generator group 202A includes a magnetic field generator 205 that generates an X-direction magnetic field, a magnetic field generator 206 that generates a Y-direction magnetic field, and a magnetic field generator 207 that generates a Z-direction magnetic field.
Fig. 3 is a schematic diagram of magnetic field target localization. In the coordinate system 300 shown in fig. 3, the magnetic field generating means comprises magnetic field generator sets 301A, 301B, 301C, 301D, each set comprising 3 magnetic field generators. For example, the magnetic field generator 302 is one magnetic field generator in the magnetic field generator set 301C, and its position and placement angle are known as P (x i ,y i ,z i ,α i ,β i ). The object positioning device (positioning sensor coil) 303 is also in the coordinate system 300. The common target objects provided with the target positioning device in the medical field comprise catheters, guide wires, introducers (sheath tubes), probes and the like, and the application fields comprise heart interventional therapy navigation, lung bronchus positioning navigation, renal artery ablation navigation and the like. The spatial position and placement angle P (x, y, z, α, β) of the object positioning device 303 are variables to be solved.
Magnetic field positioning calculation method
In the calculation operation of directly equivalent exciting coils to magnetic dipoles, according to the Biot-Savart Law, the equation is deduced by considering the magnetic dipoles as the magnetic field generator and the target phase distance are far greater than the size of the magnetic field generator, and the equation is derived:
Vol i ＝γ*(B (x,i) *cos(α)*cos(β)+B (y,i) *cos(α)*sin(β)+B (z,i) *sin(α))
wherein (x, y, z) is the three-dimensional space position of the target object, (alpha, beta) is the pitching angle and the rotation angle of the sensor coil, gamma is the gain coefficient, vol i For magnetically inducing signal components, B (x,i) Is the firstX-component, B of the magnetic induction generated by i magnetic field generators at the sensor coil (y,i) Is the y-component of the magnetic induction generated by the ith magnetic field generator at the sensor coil, B (z,i) Is the z-component of the magnetic induction produced by the ith magnetic field generator at the sensor coil.
In this method, there is a precondition that the magnetic field generator (exciting coil) and the target positioning device (positioning sensor coil) are equivalent to magnetic dipoles, respectively, to directly apply the biot-savart law. That is, in the above embodiment, the cross-sectional shape of the exciting coil of the magnetic field generator is such that the exciting coil of the magnetic field generator and the target positioning device can be equivalent to magnetic dipoles, whereby the position and direction of the target positioning device can be approximately calculated.
Therefore, in the actual production process, it is generally necessary to set the cross section of the exciting coil in the magnetic field generator to be circular so that the exciting coil approaches the structural feature of the magnetic dipole to the greatest extent. That is, in such an embodiment, the cross section of the field coil of the magnetic field generator is circular in shape.
This condition limits the structure of the exciting coil. However, in practical applications, the cross section of the coil in the magnetic field generator needs to be set to other shapes, such as a rounded rectangle in fig. 7. The structural feature that the cross section of the exciting coil needs to be set to be circular limits the design of the exciting coil structure in magnetic navigation, and is not beneficial to the installation and mass production of the exciting coil.
In the general case of the embodiment to be described next, the limitation of equivalent of the exciting coil to a magnetic dipole, the cross section of which is circular, is broken. That is, the following embodiments are applicable not only to the case where the shape of the cross section of the exciting coil of the magnetic field generator is such that the exciting coil of the magnetic field generator can be equivalently regarded as a magnetic dipole, but also to the case where the shape of the cross section of the exciting coil of the magnetic field generator is such that the exciting coil of the magnetic field generator cannot be equivalently regarded as a magnetic dipole. In the latter case, more specifically, the cross section of the exciting coil of the magnetic field generator is a shape other than a circle.
In either case, the invention provides a magnetic field target positioning calculation method, so that the exciting coils with different cross sections can perform magnetic positioning calculation, and the accurate positioning of a target object is realized.
Fig. 4 is a flowchart of a magnetic field target positioning calculation method according to an embodiment of the invention. As shown in fig. 4, the magnetic field target positioning calculation method 400 includes the steps of:
s410: dividing an exciting coil for generating a magnetic field into exciting coil sub-blocks;
s420: taking each excitation coil sub-block as a current element, and calculating the magnetic induction intensity of each excitation coil sub-block at any point P in space;
S430: the magnetic induction intensity of any point P of each excitation coil sub-block in the space is overlapped to obtain the relationship between the magnetic induction intensity generated by the whole excitation coil in the space and the space position and direction (pitching angle and rotating angle);
s440: based on the acquired magnetic induction intensity signal at the target positioning device and the relationship between the magnetic induction intensity generated in space by the exciting coil obtained in step S430 and the spatial position and direction (pitch angle and rotation angle), the spatial position coordinates and direction (pitch angle and rotation angle) of the target positioning device (sensor coil) are solved.
In step S420, the calculation of the magnetic induction intensity of each excitation coil sub-block at any point P in space using each excitation coil sub-block as a current element specifically means that the magnetic induction intensity of each excitation coil sub-block at any point P in space is obtained based on the biot-savar law according to the position and the arrangement direction of each excitation coil sub-block as a current element and the current intensity of the excitation coil sub-block.
It will be appreciated by those skilled in the art that the magnetic induction referred to above and hereinafter refers to a vector, i.e. a magnetic induction vector or vector signal, includes not only magnitude but also direction.
Compared with the prior art, the method has the advantage that when the magnetic induction electromotive force equation of the P sensor coil is listed by using the Piao-Saval law, the shape of the cross section outline of the exciting coil is taken into consideration as an essential factor, and the exciting coil and the sensor coil are not directly equivalent to be magnetic dipoles. In the specific method, the section outline of the exciting coil is divided into micro-segments, the magnetic induction intensity components of the micro-segments in a magnetic field are calculated respectively, and then the magnetic induction intensity components are accumulated through integration, and finally a calculation formula of the magnetic induction intensity of the exciting coil at any point P in space is obtained, so that a magnetic induction electromotive force equation of the coil of the P sensor is listed.
Fig. 5 is a flowchart of a method of constructing a magneto-inductive electromotive force equation according to an embodiment of the present invention.
The method for constructing the magnetomotive force equation is an important step of the present invention, and a flowchart of a method 500 for constructing the magnetomotive force equation is shown in fig. 5, and specifically includes the following steps:
s510: dividing the exciting coil into M sections along the axial direction to obtain M sub-coil pieces, and after the sub-coil pieces are equivalent to the outlines of the sub-coil pieces, segmenting the outlines, wherein the step is a further expansion of step S410 of FIG. 4;
S520: calculating the magnetic induction intensity component of each section of the contour at any point P in the magnetic field by using the Biaoh-Saval law, wherein the step is a further expansion of step S420 of FIG. 4;
s530: superposing magnetic induction intensity components of each section of the contour at P to obtain the magnetic induction intensity of the contour at P; superposing the magnetic induction intensities of the M outlines on the P in the axial direction to obtain the magnetic induction intensity of the exciting coil on the P, wherein the expression of the magnetic induction intensity of the P comprises the three-dimensional space position coordinate and angle of the P, so that the relation between the magnetic induction intensity of the whole exciting coil in space and the space position and direction is obtained, and the step is further expansion of step S430 of FIG. 4;
s540: listing the magnetic induction intensity of the sensor coil in the direction of a P normal vector according to the law of electromagnetic induction, wherein the normal vector refers to a normal unit vector on the section of the sensor coil, and the normal vector is characterized by a pitching angle and a rotating angle; the principle that the magnetic induction intensity of the exciting coil obtained in step S530 in P and the magnetic induction intensity of the sensor coil obtained in this step in the P normal vector direction are equal lists the magnetic induction electromotive force equation, so as to solve the position and direction of the obtained target positioning device (sensor coil), which is a further extension of step S440 of fig. 4.
In a preferred embodiment of the invention, the profile described above is a closed profile. For example, the contour may be composed of arc segments and straight segments.
In a preferred embodiment, which will be described in detail below, the profile is in the shape of a rounded rectangle. However, it will be appreciated by those skilled in the art that the profile may also be circular in shape. In addition, the shape may be another shape such as a rounded triangle.
Fig. 6 is a schematic diagram of coordinates of an excitation coil using a cartesian coordinate system according to an embodiment of the invention. As shown in fig. 9, the excitation coil is sectioned in the Z direction by using a cartesian coordinate system with its center at the origin of coordinates, the axial vector being directed in the Z direction, the cross-sectional vector being directed in the X direction and the Y direction, and the excitation coil of length H is equivalent to M thin coils (sub-coil pieces) of length H/M, wherein the center position z=0 of the excitation coil and the center position of the i-th thin coil is
Fig. 7 is a schematic view of an excitation coil having a rectangular cross section with rounded corners according to an embodiment of the invention. Fig. 8 is a schematic view of an excitation coil having a rounded triangle cross-section according to an embodiment of the invention. Fig. 9 is a schematic view of an excitation coil having another rounded rectangle in cross section according to an embodiment of the invention.
On any one of the thin coils (center position is [0, Z ]), a method of constructing a magnetic induction electromotive force equation is described by taking a round rectangle as an example of a cross section. The thin coil is equivalent to a rounded rectangle, the rounded rectangle is shown in fig. 7, the straight line segments are K1, K2, K3 and K4, the arc line segments are S1, S2, S3 and S4, the rounded rectangle is formed by splicing S1, K1, S2, K2, S3, K3, S4 and K4 into a closed shape in sequence, the graph is symmetrical, the arc line segments are S1, S2, S3 and S4 which can be combined into a circle, namely the arc line segments S1, S2, S3 and S4 are respectively one quarter of the same circle, and the circle where the rounded rectangle is positioned is equally divided into four equal parts. The thin coil used to calculate the magnetic induction may also be other shapes, such as rounded triangles in fig. 8, or another rounded rectangle in fig. 9. The common point of fig. 7, 8 and 9 is that the contour can be divided into line segments and arcs, and the magnetic induction of each segment of the contour at a certain point in space can be obtained by integration, so that the magnetic induction of the contour at a certain point in space can be obtained by superposition.
The calculation method of the magnetic induction intensity of the exciting coil at a certain point in space and the solving method of the three-dimensional space position and angle of the sensor coil in the magnetic field are described below by taking a rounded rectangle as an example.
Obviously, the fillet rectangle comprises 4 1/4 circular arcs and 4 straightway, and fillet rectangle straightway side length is L, W respectively, and four corners circular arc radius is R, (X, Y, Z) are coordinate point on the fillet rectangle, get arbitrary point on these eight line segments respectively:
the coordinates of any point of the arc S1 (circle centers [ L/2, W/2, Z ], ψ= [0, pi/2 ]) are as follows:
M1＝[L/2+R*cos(Ψ),W/2+R*sin(Ψ),Z]；
straight line segment K1 ([ L/2, (W/2+R), Z ] to [ -L/2, (W/2+R), Z ]) any point coordinates are:
M2＝[X,(W/2+R),Z]；
the coordinates of any point of the arc S2 (circle center [ -L/2, W/2, Z ], psi = [ pi/2, pi ]) are as follows:
M3＝[-L/2+R*cos(Ψ),W/2+R*sin(Ψ),Z]；
straight line segment K2 ([ - (L/2+R), W/2, Z ] to [ - (L/2+R), -W/2, Z ]) has any point coordinates:
M4＝[-(L/2+R),Y,Z]；
the coordinates of any point of the arc S3 (circle center [ -L/2, -W/2, Z ], psi = [ pi, 3 pi/2 ]) are as follows:
M5＝[-L/2+R*cos(Ψ),-W/2+R*sin(Ψ),Z]；
straight line segment K3 ([ -L/2, - (W/2+R), Z ] to [ L/2, - (W/2+R), Z ]) has any point coordinates:
M6＝[X,-(W/2+R),Z]；
the coordinates of any point of the arc S4 (circle center [ L/2, -W/2, Z ], psi= [ 3pi/2, 2pi ]) are as follows:
M7＝[L/2+R*cos(Ψ),-W/2+R*sin(Ψ),Z]；
straight line segment K4 ([ (L/2+R), -W/2, Z ] to [ (L/2+R), W/2, Z ]) has any point coordinates:
M8＝[(L/2+R),Y,Z]；
any current element I (dl) is intercepted on the line segments, and the magnetic induction intensity generated by the current element in a magnetic field is as follows according to the law of Biot-Savart:
the magnetic induction B generated by the multi-line segment is dB of each line segment n And (5) stacking after integration.
Wherein dli is the derivative of M1 to M8:
dl1＝diff(M1,Ψ)；
dl2＝diff(M2,X)；
dl3＝diff(M3,Ψ)；
dl4＝diff(M4,Y)；
dl5＝diff(M5,Ψ)；
dl6＝diff(M6,X)；
dl7＝diff(M7,Ψ)；
dl8＝diff(M8,Y)。
It is noted here that diff is a differential function in matlab. For example, diff (M1, ψ) is the derivative of M1 by ψ. Namely:
ai is the vector of M1-M8 pointing to a point P (x, y, z) in magnetic field space:
a1＝cp-M1；
a2＝cp-M2；
a3＝cp-M3；
a4＝cp-M4；
a5＝cp-M5；
a6＝cp-M6；
a7＝cp-M7；
a8＝cp-M8。
because:
whileSo that:
above |a i | -3 It is difficult to obtain an integral analysis formula, and an approximation calculation process is required. Due to (1+x) m The taylor expansion of (2) is:
taking only the first item, (1+x) m ≈1+m·x。
Thereby the processing time of the product is reduced,
/>
for a pair ofThe integral can be obtained:
b1＝int(dl1×a1*a1^(-3),Ψ,0,π/2)；
b2＝int(dl2×a2*a2^(-3),X,L/2,-L/2)；
b3＝int(dl3×a3*a3^(-3),Ψ,π/2,π)；
b4＝int(dl4×a4*a4^(-3),Y,W/2,-W/2)；
b5＝int(dl5×a5*a5^(-3),Ψ,π,3π/2)；
b6＝int(dl6×a6*a6^(-3),X,-L/2,L/2)；
b7＝int(dl7×a7*a7^(-3),Ψ,3π/2,2π)；
b8＝int(dl8×a8*a8^(-3),Y,-W/2,W/2)。
it is noted here that int is the integral function in matlab. For example, int (dl 1×a1×a1 (-3), ψ,0, pi/2) is dl1×a1×a1 (-3) integrated by ψ in the interval [0, pi/2 ], and b1 to b8 are magnetic induction intensities corresponding to each of the eight segments after dividing the rounded rectangle into eight segments. The general mathematical formula written as:
when i=1, 2,3,4,5,6,7,8, respectively, it is noted that:
the magnetic induction of the rounded rectangle is the vector integral of the magnetic induction of each section, and can be expressed as follows: b=b1+b2+b3+b4+b5+b6+b6+b8. The more general expression is:wherein B is j The magnetic induction of the jth profile at P, N being the number of segments into which the profile is divided, b i Is the integral of the magnetic induction component of the ith section in the jth profile at any point P in the magnetic field over a corresponding length or angular range.
In particular, when the exciting coil is a solenoid coil, since l=0, w=0, and z=0, the cross-sectional profile of the exciting coil is circular, the expression of the magnetic induction intensity of the circular profile at P is expressed in the XYZ coordinate system as:
Wherein Bx, by and Bz are components of the magnetic induction intensity of the profile in the X, Y, Z axial direction, N is the number of exciting coil turns, R is the radius of a quadrangle arc, μ is the magnetic permeability, and (x, y, z) is the three-dimensional coordinate of point P.
After the magnetic induction intensity of each section contour of the exciting coil at the point P is obtained, the magnetic induction intensities of M contours at the point P are overlapped in the axial direction, so that the magnetic induction intensity of the whole exciting coil at the point P is obtained, and the expression of the magnetic induction intensity of the exciting coil at the point P is thatWherein B is the magnetic induction intensity of the exciting coil at the point P, B j The magnetic induction intensity of the jth profile at the point P is M, and the number of segments for axially dividing the exciting coil is defined.
Applying exciting voltage U to exciting coil, the exciting coil is composed ofAvailable, excitation current change rate +.>Where L' is the exciting coil inductance. Is provided with->B '= (Bx', by ', bz'), then +.>Mu is magnetic permeability, N is the number of turns of the exciting coil, U is exciting voltage applied to the exciting coil, R is the radius of a square arc, L ' is inductance of the exciting coil, B ' is magnetic induction intensity of the exciting coil after coordinate conversion of magnetic induction intensity B of the exciting coil at point P, and the coordinate conversion is to convert magnetic induction intensity B of P represented by the center point of the exciting coil as an origin into magnetic induction intensity B ' of P in the same coordinate system as the sensor coil. The coordinate system of the space where the sensor coil is located is not established by taking the center point of the exciting coil as the origin, so that the conversion is performed so that the space coordinate of the sensor coil and the magnetic induction intensity B of P are located in the same coordinate system, and the magnetic induction intensity of P after conversion is denoted as B'.
Induced electromotive force of the sensor according to the law of electromagnetic inductionWhere n is the number of sensor coil turns and Φ is the magnetic flux through the sensor coil. And Φ=b·s, where B is the magnetic induction intensity of the magnetic field generated by the exciting coil at the sensor coil (P), S is the sensor coil sectional area, s= (pi·r) 2 ) Where r is the sensor coil circumference radius, vp '(xv', yv ', zv') is the normal unit vector of the sensor coil cross section, which can be characterized by pitch angle and rotation angle.
Is provided withThe magnetomotive force epsilon=k· (B '·vp') of the sensor. By substituting the measured magneto-inductive electromotive force and the calculated coefficient k into ε=k· (B '·vp'), a simultaneous equation set can be obtained, and since the three-dimensional space position coordinates of the P point are included in B ', vp' is represented by the pitch angle and the rotation angle, the coordinates (three-dimensional coordinates) and the attitudes (pitch angle and rotation angle) of the sensor coil can be calculated by the simultaneous equation set. Preferably, the LM algorithm is used to solve for sensor coordinates and gestures.
In the above method, the acquired magnetic induction signals at the target positioning device comprise respective magnetic induction signal components of each magnetic field generator (exciting coil) acting on the target positioning device. Thus, in the above method, in step S440 of fig. 4, obtaining the position and direction of the target positioning device based on the acquired magnetic induction signals at the target positioning device and the relationship between the magnetic induction generated in space by the exciting coil and the spatial position and direction includes: and listing a magnetic induction electromotive force equation set based on the corresponding magnetic induction intensity signal component acted on the target positioning device by each magnetic field generator and the relation between the magnetic induction intensity generated by the exciting coil of each magnetic field generator in space and the space position and direction, so as to solve and obtain the position and direction of the target positioning device.
The problem of solving the overdetermined equation set is really a nonlinear model solving problem, part (more than or equal to 6) or all equations in the problem can be selected according to a certain screening criterion to be solved simultaneously, a common solving method is an LM (Levenberg-Marquardt) algorithm or an improved version thereof, and the preferred embodiment of the invention adopts the improved version thereof and can obtain convergence in 3-8 iterations.
The above equation set is an approximate calculation equation obtained by taking the first harmonic component after taylor expansion of the calculation equation according to the biot-savart law, so the position and direction obtained by solving the overdetermined equation are approximate values. In order to improve the accuracy of the calculation result, the target positioning device (target object) needs to be placed within a certain distance from the magnetic field generator, and the obtained data is relatively accurate. The target positioning device is too close to the magnetic field generator, the response signal sensed by the positioning sensor coil through the excitation signal of the magnetic field generator is strong, the response signal is substituted into the equation, and the calculated position and direction errors are larger and inaccurate; the target positioning device is far away from the magnetic field generator, the response signal sensed by the positioning sensor coil through the excitation signal of the magnetic field generator is weak, the response signal is substituted into the equation, and the calculated position and direction errors are larger and inaccurate. Therefore, in the actual calculation process, equations corresponding to signal components with too close distance or too far distance need to be removed, and equations corresponding to signal components with too close distance or too far distance can be removed. The response signal components of the equations in the listed equation set are in a reasonable range, so that the calculation accuracy is improved. The method comprises the following specific steps:
A301, dividing the signal components equally into a plurality of groups, such as N groups, and calculating the sum of signal moduli of the groups;
and A302, finding out a signal component group with the maximum and/or minimum sum of modulus values, deleting equations corresponding to the signal component group with the maximum and/or minimum sum of modulus values, and forming the rest equations into an optimal overdetermined equation group to participate in final solving. If the number of unknowns is 6 (one is a gain coefficient in addition to the three-dimensional coordinates, the pitch angle and the rotation angle), after part of the equations are eliminated, the number of the remaining equations needs to be greater than or equal to 6, and typically the number of the equations is 6-12, and preferably the number of the equations is 6, 9 or 12. Comparing the sum of the signal moduli of all the groups to obtain a signal component group with the maximum and/or minimum sum of the moduli, and removing the equation corresponding to the signal component group; and forming the rest equations into an optimal overdetermined equation set, and solving the position and the direction of the target positioning device.
As a preferred scheme, a method for screening out an optimized equation combination from 12 equations is provided, which specifically comprises the following steps:
a3001, respectively counting the sum of the signal moduli acquired by the object positioning device 103 for the magnetic field generator groups 102A, 102B, 102C and 102D, wherein the calculation formula is as follows:
Wherein Vol i Is the signal quantity generated by the magnetic field generated by the ith magnetic field generator acting on the target object, i is the number or index of each signal component, vol A 、Vol B 、Vol C And Vol D The sum of the moduli of the adjacent three semaphores, respectively.
A3002, compare Vol A 、Vol B 、Vol C And Vol D From which the value is selectedAnd (3) finding out 3 semaphores corresponding to the maximum modulus sum, removing equations corresponding to the 3 semaphores from the 12 equation sets, and combining the rest 9 equations to form an optimal overdetermined equation set to participate in final solving.
The above procedure can be summarized as: dividing the signal components into a plurality of groups uniformly, and calculating the sum of signal moduli of the groups; comparing the sum of the signal moduli of all the groups to obtain a signal component group with the maximum and/or minimum sum of the moduli, and removing the equation corresponding to the signal component group; and forming the rest equations into an optimal overdetermined equation set, and solving the position and the direction of the target positioning device.
FIG. 10 is a flow chart of an iterative solution of target position and orientation in accordance with an embodiment of the invention. As shown in fig. 10, the target position and orientation solving process 1000 begins at step 1001 where signal components generated by the respective magnetic field generators acting on the target positioning device are input. Next, in step 1002, it is determined whether the result is not solved a plurality of times in succession under the current input condition. If the number of times exceeds the preset value (e.g., 3 times), i.e., yes branch of step 1002, the current round of solution is stopped in step 1004, and the solution failure is output. If the number of times exceeds the preset value, i.e. the no branch of step 1002, step 1003 is entered to determine whether the target object corresponding to the current input is the first solution. If the solution is the first time, i.e., the "yes" branch of step 1003, step 1005 is entered, and an initial bit value is randomly generated as an initial iteration value; if the solution is not the first time, i.e., the "no" branch of step 1003, step 1006 is entered, using the previous solution result as the initial value for the iterative solution. After the initial values are determined, the coordinates and direction of the object are iteratively solved, step 1007, with a common method being the LM (Levenberg-Marquardt) algorithm or its modified version. It is determined at step 1008 whether the iteration is converging. If convergence, the "yes" branch of step 1008, then the successful solution is marked in step 1009, and then the solution result is output in step 1010; if convergence fails, no branch of step 1008, then step 1002 is returned to determine if the number of failures exceeds a preset number.
That is, the position and orientation of the target positioning device may be iteratively solved according to the Levenberg-Marquardt (LM) algorithm or a modified version thereof.
Direct magnetic dipole equivalent
In addition, an algorithm is attached below that directly equivalent the magnetic field generator or exciting coil to a magnetic dipole. The algorithm can be used in the case where the cross section of the exciting coil is circular in shape.
Because the phase distance between the magnetic field generator and the object is far greater than the size of the magnetic field generator, the magnetic field generator and the object can be directly regarded as magnetic dipoles. According to the Biot-Savart Law (Biot-Savart Law), the positioning principle is described in detail as follows:
based on the position and placement angle of the magnetic field generator 302, a normalized magnetic field generator direction vector can be obtained
Dir (x,i) ＝cos(α i )*cos(β i )
Dir (y,i) ＝cos(α i )*sin(β i )
Dir (z,i) ＝sin(α i )
Wherein (x) i ,y i ,z i ) Is a three-dimensional space position (alpha) i ,β i ) Is the pitch angle (polar angle) and the rotation angle (azimuth angle) of the magnetic field generator, where i represents the number or index of the magnetic field generator, e.g. i=1, 2, …, N, n+.6 when N magnetic field generators are present.
Object-to-magnetic field generator distance:
the ith magnetic field generator generates a signal Vol generated by the magnetic field acting on the target object i Corresponding to the acquiredMagnetic induction signals:
/>
Vol i ＝γ*(B (x,i) *cos(α)*cos(β)+B (y,i) *cos(α)*sin(β)+B (z,i) *sin(α))
wherein, (x, y, z) is the three-dimensional space position of the target object, (alpha, beta) is the pitch angle (polar angle) and the rotation angle (azimuth angle) of the positioning sensor coil, gamma is the gain coefficient, and P (x, y, z, alpha, beta, gamma) is 6 unknown quantities to be solved. Taking 12 magnetic field generators as an example, 12 equations containing 6 unknowns can be obtained, which are combined to form an overdetermined equation set.
The magnetic field target positioning method is suitable for all fields and application scenes needing target positioning, for example, the magnetic field target positioning method can be used for medical application scenes, and can also be used for determining the position and the direction of the head after wearing VR glasses and AR helmets.
Computer program or computer program product and computer readable medium
Furthermore, those of ordinary skill in the art will recognize that the methods of the present disclosure may be implemented as a computer program. The methods of the above embodiments, including instructions to cause a computer or processor to perform the algorithms described in connection with the figures, are performed by one or more programs, as described above in connection with the figures. These programs may be stored and provided to a computer or processor using various types of non-transitory computer readable media. Non-transitory computer readable media include various types of tangible storage media. Examples of the non-transitory computer readable medium include magnetic recording media such as floppy disks, magnetic tapes, and hard disk drives, magneto-optical recording media such as magneto-optical disks, CD-ROMs (compact disk read-only memories), CD-R, CD-R/W, and semiconductor memories such as ROMs, PROMs (programmable ROMs), EPROMs (erasable PROMs), flash ROMs, and RAMs (random access memories). Further, these programs may be provided to a computer by using various types of transitory computer readable media. Examples of transitory computer readable media include electrical signals, optical signals, and electromagnetic waves. The transitory computer readable medium may be used to provide a program to a computer through a wired communication path such as electric wires and optical fibers or a wireless communication path.
For example, according to one embodiment of the present disclosure, a computer readable medium may be provided having instructions stored thereon that, when executed by a processor, cause the processor to perform the magnetic field target location calculation method as described previously.
Thus, according to the present disclosure, a computer program or computer program product may also be proposed which, when executed, enables the magnetic field target location calculation method as described before.
In addition, the invention also relates to a computing device or a computing system, comprising a processor and a memory, wherein the memory stores a computer program, which, when executed by the processor, can implement the magnetic field target positioning computing method as described above.
The beneficial effects of the invention are that
In summary, in addition to the effects already described above, the beneficial effects of the present invention can be summarized as follows:
1. after a magnetic field target position tracking and positioning system is constructed, the magnetic field generator and the positioning sensor are not equivalent to magnetic dipoles, but the exciting coil of the magnetic field generator is divided into exciting coil sub-blocks, each exciting coil sub-block is used as a current element, the magnetic induction intensity of each exciting coil sub-block at any point P in space is calculated, then the magnetic induction intensity of each exciting coil sub-block at any point P in space is overlapped, and the relationship between the magnetic induction intensity generated by the whole exciting coil in space and the space position, the pitching angle and the rotation angle is established. This has the advantage that in the magnetic positioning system, the cross-sectional shape of the exciting coil is more expanded, not necessarily circular, but also rectangular with rounded corners, or triangular with rounded corners and a combination of line segments and arcs, which gives more possibilities for manufacturing and mounting the exciting coil.
2. Even if the distance between the exciting coils is very short, the exciting coils cannot be equivalent to magnetic dipoles, the signal component generated by the exciting coils acting on the sensor coils can still be accurately calculated by adopting the method provided by the invention, so that the accurate positioning of the target object (the sensor coils) is realized.
3. After the overdetermined equation set is formed by adopting the combination of a plurality of signal components, in order to improve the calculation efficiency, a method for screening the optimized equation set from a plurality of equations is also provided, so that the number of equations in the equation set is reduced, and the calculation efficiency is improved.
The embodiments of the present invention are not limited to the examples described above, and those skilled in the art can make various changes and modifications in form and detail without departing from the spirit and scope of the present invention, which are considered to fall within the scope of the present invention.
Claims (14)
1. A method for magnetic field target location calculation, comprising:
dividing an exciting coil for generating a magnetic field into exciting coil sub-blocks; the exciting coil sub-block is a straight line segment or an arc line formed after the section of the exciting coil is cut;
taking each excitation coil sub-block as a current element, and calculating the magnetic induction intensity of each excitation coil sub-block at any point P in space;
Superposing the magnetic induction intensity of any point P of each excitation coil sub-block in space to obtain the relationship between the magnetic induction intensity generated by the whole excitation coil in space and the space position and direction; and
based on the acquired magnetic induction intensity signal at the target positioning device and the relation between the magnetic induction intensity generated by the exciting coil in space and the space position and direction, the position and direction of the target positioning device are obtained, and the method comprises the following steps: listing a magnetic induction electromotive force equation set based on the corresponding magnetic induction intensity signal component acted on the target positioning device by each magnetic field generator and the relation between the magnetic induction intensity generated by the exciting coil of each magnetic field generator in space and the space position and direction, and calculating the modulus value of the signal component;
obtaining signal components with maximum and/or minimum modulus values, and removing equations corresponding to the signal components;
the rest equations form an optimized overdetermined equation set, and the position and the direction of the target positioning device are solved;
the step of superposing the magnetic induction intensity of each excitation coil sub-block at any point P in the space to obtain the relationship between the magnetic induction intensity generated by the whole excitation coil in the space and the space position and direction further comprises the following steps: superposing magnetic induction intensity components of the straight line segments or the arcs at P to obtain magnetic induction intensity of an exciting coil section formed by the straight line segments or the arcs at P; superposing the magnetic induction intensities of the sections of the exciting coils in the axial direction to obtain the magnetic induction intensity of the exciting coils in the P, thereby obtaining the relationship between the magnetic induction intensity generated by the whole exciting coil in space and the space position and direction;
The magnetic field is generated using a plurality of magnetic field generators fixed to the fixture,
each magnetic field generator is arranged at a different position or in a different arrangement direction to generate a corresponding magnetic field,
each magnetic field generator comprises the field coil.
2. The method of claim 1, wherein said calculating the magnetic induction of each excitation coil sub-block at any point P in space using each excitation coil sub-block as a current element, further comprises:
and obtaining the magnetic induction intensity of the excitation coil sub-blocks at any point P in space based on the Piaor-savart law according to the position and the arrangement direction of each excitation coil sub-block serving as a current element and the current intensity of the excitation coil sub-blocks.
3. The method according to claim 1, wherein:
the dividing the exciting coil for generating the magnetic field into exciting coil sub-blocks further comprises: dividing the exciting coil into M sections along the axial direction to obtain M sub-coil pieces, equivalent the sub-coil pieces to the outlines of the sub-coil pieces, segmenting the outlines,
the method for calculating the magnetic induction intensity of each excitation coil sub-block at any point P in space by using each excitation coil sub-block as a current element further comprises the following steps: the magnetic induction intensity component of each section of the outline at any point P in the magnetic field is calculated by using the Biaoo-savart law,
The method for superposing the magnetic induction intensity of each excitation coil sub-block at any point P in space to obtain the relationship between the magnetic induction intensity generated by the whole excitation coil in space and the space position and direction, and the method further comprises the following steps: superposing magnetic induction intensity components of each section of the contour at P to obtain the magnetic induction intensity of the contour at P; the magnetic induction intensities of M outlines at P are overlapped in the axial direction to obtain the magnetic induction intensity of the exciting coil at P, so as to obtain the relationship between the magnetic induction intensity generated by the whole exciting coil in space and the space position and direction,
the method for obtaining the position and the direction of the target positioning device based on the acquired magnetic induction intensity signal at the target positioning device and the relationship between the magnetic induction intensity generated by the exciting coil in space and the space position and the direction further comprises the following steps: listing magnetic induction intensity of a sensor coil of the target positioning device in the direction of a P normal vector according to an electromagnetic induction law, wherein the normal vector refers to a normal unit vector of a section of the sensor coil; and listing a magnetic induction electromotive force equation according to the principle that the magnetic induction intensity of the exciting coil at P is equal to the magnetic induction intensity of the sensor coil at the normal vector of P, so as to solve and obtain the position and the direction of the target positioning device.
4. A method according to claim 3, wherein the profile is a closed profile.
5. The method of claim 4, wherein the profile is comprised of arc segments and straight segments.
6. The method of claim 5, wherein the profile is in the shape of a rounded rectangle.
7. The method of claim 4, wherein the profile is circular in shape.
8. The method of claim 1, wherein the target positioning device is located on a medical device for medical intervention into the living being.
9. The method of claim 1, wherein the position and orientation of the target positioning device comprises three-dimensional coordinates, pitch angle, and rotation angle of the target positioning device.
10. The method of claim 1, wherein the plurality of magnetic field generators is at least 6 magnetic field generators.
11. The method of claim 1, wherein the acquired magnetic induction signals at the target positioning device comprise respective magnetic induction signal components of each magnetic field generator acting on the target positioning device.
12. The method of claim 1, wherein the listing of the set of magnetomotive force equations based on the respective magnetic induction intensity signal components applied to the target positioning device by each magnetic field generator and the spatial relationship of the magnetic induction intensity generated in space by the exciting coil of each magnetic field generator to the spatial position and orientation, thereby solving for the position and orientation of the target positioning device, further comprises:
Dividing the signal components into a plurality of groups uniformly, and calculating the sum of signal moduli of the groups;
comparing the sum of the signal moduli of all the groups to obtain a signal component group with the maximum and/or minimum sum of the moduli, and removing the equation corresponding to the signal component group;
and forming the rest equations into an optimal overdetermined equation set, and solving the position and the direction of the target positioning device.
13. The method of claim 1, wherein the listing of the set of magnetomotive force equations based on the respective magnetic induction intensity signal components applied to the target positioning device by each magnetic field generator and the spatial relationship of the magnetic induction intensity generated in space by the exciting coil of each magnetic field generator to the spatial position and orientation, thereby solving for the position and orientation of the target positioning device, further comprises:
the position and orientation of the target positioning device is iteratively solved according to the Levenberg-Marquardt (LM) algorithm or its modified algorithm.
14. A computer readable medium having stored thereon instructions executable by a processor, which instructions, when executed by the processor, cause the processor to perform the magnetic field target location calculation method of claim 1.
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