CN114543645B

CN114543645B - Magnetic field target positioning system and method

Info

Publication number: CN114543645B
Application number: CN202210159008.7A
Authority: CN
Inventors: 陈传金
Original assignee: Chengdu Siruiding Life Technology Co ltd
Current assignee: Chengdu Siruiding Life Technology Co ltd
Priority date: 2022-02-21
Filing date: 2022-02-21
Publication date: 2024-01-30
Anticipated expiration: 2042-02-21
Also published as: CN114543645A

Abstract

The invention discloses a magnetic field target positioning system and a magnetic field target positioning method. The magnetic field object positioning system according to the present invention comprises: the magnetic field generation control module is used for generating a signal for controlling the generation of a magnetic field; a magnetic field generating device for generating a magnetic field in space according to the signal generated by the magnetic field generating control module; the target positioning device is positioned in the magnetic field generated by the magnetic field generating device and generates a magnetic induction signal; the signal acquisition module is used for acquiring magnetic induction signals generated at the target positioning device; and the positioning calculation module is used for calculating the position and the direction of the target positioning device according to the magnetic induction signals acquired by the magnetic field signal acquisition module. The target positioning technology can be used in medical operation, particularly interventional operation, and can ensure the positioning accuracy as much as possible under the condition of excessively occupying the size of a target object. The more commonly applicable positioning calculation method provided by the invention does not need to limit the cross section of the exciting coil to be circular.

Description

Magnetic field target positioning system and method

Technical Field

The present invention relates to electromagnetic fields, and more particularly to magnetic field target positioning systems and methods.

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.

It is therefore desirable to provide a target positioning technique that can be used in medical procedures, particularly interventional procedures, and that can ensure as much accuracy as possible of positioning without taking up too much of the target size.

Disclosure of Invention

The invention provides a technology for positioning a target based on a magnetic field. A magnetic field is controllably generated in the vicinity of the living body, and the position and direction of the object in the magnetic field space, such as three-dimensional coordinates, pitch angle, and rotation angle, are calculated by collecting magnetic induction signals of the object in the magnetic field space.

According to a first aspect of the present invention, a magnetic field target positioning system is provided. The system may include: the magnetic field generation control module is used for generating a signal for controlling the generation of a magnetic field; a magnetic field generating device for generating a magnetic field in space according to the signal generated by the magnetic field generating control module; the target positioning device is positioned in the magnetic field generated by the magnetic field generating device and generates a magnetic induction signal; the signal acquisition module is used for acquiring magnetic induction signals generated at the target positioning device; and the positioning calculation module is used for calculating the position and the direction of the target positioning device according to the magnetic induction signals acquired by the magnetic field signal acquisition module.

In the magnetic field object localization system according to the first aspect of the invention, the object localization device may be located on a medical device for medical intervention into a living being.

In the magnetic field target positioning system according to the first aspect of the invention, the calculation is a discretization calculation for the magnetic field generating device. The discretization calculation comprises dividing a magnetic field generator in the magnetic field generating device into sub-modules according to different dimensions, and performing discretization treatment, so that the positioning calculation module calculates the position and the direction of the target positioning device by each sub-module, and then synthesizes the positions and the directions to obtain a final result.

In the magnetic field target positioning system according to the first aspect of the invention, the magnetic field generating means may further include a plurality of magnetic field generators and fixing means for fixing the plurality of magnetic field generators. Each magnetic field generator may be arranged at a different position or in a different orientation in the magnetic field generating means to generate a corresponding magnetic field. Furthermore, each magnetic field generator comprises a field coil.

In the magnetic field object positioning system according to the first aspect of the invention, the object positioning means is a positioning sensor coil.

In the magnetic field target positioning system according to the first aspect of the invention, the magnetic field generation control module may be configured to generate alternating currents of a plurality of frequencies, each magnetic field generator being configured to generate a respective magnetic field from the respective frequency currents generated by the magnetic field generation control module, thereby generating a frequency modulated magnetic field containing the respective frequency.

Alternatively, the magnetic field generation control module may be configured to generate square wave currents, each magnetic field generator being configured to receive the square wave currents in time-sharing rotation and generate a corresponding magnetic field, thereby generating magnetic fields in time-series.

Accordingly, the signal acquisition module is configured to decompose the respective magnetically induced signal components of each magnetic field generator acting on the target positioning device according to a magnetic field generation manner.

In the magnetic field target positioning system according to the first aspect of the invention, the positioning calculation module may be configured to: based on the biot-savart law, the system of equations solves the position and orientation of the target positioning device from the respective magnetically induced signal components of each magnetic field generator acting on the target positioning device.

Preferably, the above operations may further include: calculating a modulus value of the signal component; 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.

Preferably, the above operations may further include: 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.

Preferably, the position and orientation of the target positioning device is iteratively solved according to the Levenberg-Marquardt (LM) algorithm or a modified version thereof.

In the magnetic field object positioning system according to the first aspect of the invention, the position and orientation of the object positioning device include three-dimensional coordinates, pitch angle and rotation angle of the object positioning device.

In the magnetic field object positioning system according to the first aspect of the invention, the plurality of magnetic field generators is at least 6 magnetic field generators.

In the magnetic field target positioning system according to the first aspect of the invention, the shape of the cross section of the exciting coil of the magnetic field generator may be such that the exciting coil of the magnetic field generator and the target positioning device are equivalent to magnetic dipoles, thereby approximating the position and direction of the target positioning device. Preferably, the cross section of the exciting coil of the magnetic field generator may be circular in shape.

Alternatively, the cross-sectional shape of the field coil of the magnetic field generator may be such that the field coil of the magnetic field generator cannot be equivalently a magnetic dipole. Preferably, the cross section of the exciting coil of the magnetic field generator may be a shape other than a circle.

In the magnetic field target positioning system according to the first aspect of the invention, the positioning calculation module may be further configured to: dividing the exciting coil 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 magnetic induction intensity signal at the target positioning device acquired by the magnetic field signal acquisition module and the relationship between the magnetic induction intensity generated by the exciting coil in space and the space position and the direction.

Preferably, the 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 may further include: 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.

Preferably, the dividing the exciting coil into exciting coil sub-blocks may further include: dividing the exciting coil into M sections along the axial direction to obtain M sub-coil pieces, and segmenting the outline after the sub-coil pieces are equivalent to the outline of the sub-coil pieces. The calculating the magnetic induction intensity of each excitation coil sub-block at any point P in space by taking each excitation coil sub-block as a current element may further include: 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. The step of 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 may further comprise: 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. The obtaining the position and the direction of the target positioning device based on the magnetic induction intensity signal at the target positioning device collected by the magnetic field signal collecting module and the relationship between the magnetic induction intensity generated by the exciting coil in space and the space position and the direction may further include: 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.

According to a second aspect of the present invention, a magnetic field target positioning method is provided. The method may include: generating a signal for controlling the generation of the magnetic field; generating a magnetic field in space according to the generated signal for controlling the generation of the magnetic field; collecting magnetic induction signals generated by a target positioning device in the magnetic field; and calculating the position and the direction of the target positioning device according to the acquired magnetic induction signals.

In the magnetic field target positioning method according to the second aspect of the invention, the target positioning device may be located on a medical device for medical intervention into a living being.

In the magnetic field target positioning method according to the second aspect of the present invention, the calculation is a discretization calculation for the magnetic field, the discretization calculation includes dividing a magnetic field generator for generating the magnetic field into sub-modules according to different dimensions, and performing discretization processing, so that the position and the direction of the target positioning device are calculated by each sub-module, and then the final result is obtained by synthesis.

In the magnetic field target positioning method according to the second aspect of the invention, a plurality of magnetic field generators fixed to the fixture may be employed to generate a magnetic field in space. Each magnetic field generator may be arranged in a different position or in a different orientation to generate a corresponding magnetic field. Furthermore, each magnetic field generator may comprise a field coil.

In the magnetic field object localization method according to the second aspect of the present invention, the object localization means may be a localization sensor coil.

In the magnetic field target positioning method according to the second aspect of the invention, the operation of generating a signal for controlling the generation of the magnetic field may include generating alternating currents of a plurality of frequencies. The operation of generating a magnetic field in space may include each magnetic field generator generating a corresponding magnetic field from the generated current of the respective frequency, thereby generating a frequency modulated magnetic field comprising the respective frequency.

Alternatively, the operation of generating a signal to control the generation of the magnetic field may comprise generating a square wave current. The operation of generating the magnetic field in space may include each magnetic field generator receiving the square wave current in time-sharing rotation and generating a corresponding magnetic field, thereby generating the magnetic field in time-sharing rotation.

Accordingly, the operation of collecting the magnetic induction signal generated by the object positioning device in the magnetic field may include: and decomposing corresponding magnetic induction signal components acted on the target positioning device by each magnetic field generator according to a magnetic field generation mode.

In the magnetic field target positioning method according to the second aspect of the present invention, the operation of calculating the position and orientation of the target positioning device may include: based on the biot-savart law, the system of equations solves the position and orientation of the target positioning device from the respective magnetically induced signal components of each magnetic field generator acting on the target positioning device.

In the magnetic field target positioning method according to the second aspect of the present invention, the operation of solving the position and the direction of the target positioning device according to the respective magnetic induction signal components applied to the target positioning device by each magnetic field generator by the system of equations may further include: calculating a modulus value of the signal component; 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.

Preferably, the operation of solving the position and direction of the target positioning device according to the respective magnetic induction signal components applied to the target positioning device by each magnetic field generator by the system of equations may further include equally dividing the signal components into a plurality of groups (for the reason that the position is expressed by XYZ three-dimensional coordinates, and each three coils XYZ are combined into one group, thus being divided into four groups, and the sum of three moduli of each group is judged to be the best), and calculating the sum of the signal moduli of each group; 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 magnetic field target positioning method according to the second aspect of the present invention, the operation of solving the position and the direction of the target positioning device according to the respective magnetic induction signal components applied to the target positioning device by each magnetic field generator by the system of equations may further include: the position and orientation of the target positioning device is iteratively solved according to the Levenberg-Marquardt (LM) algorithm or its modified algorithm.

In the magnetic field target positioning method according to the second aspect of the present invention, the position and direction of the target positioning device may include three-dimensional coordinates, pitch angle, and rotation angle of the target positioning device.

In the magnetic field target positioning method according to the second aspect of the invention, the plurality of magnetic field generators may be at least 6 magnetic field generators.

In the magnetic field target positioning method according to the second aspect of the present invention, the shape of the cross section of the exciting coil of the magnetic field generator may be such that the exciting coil of the magnetic field generator and the target positioning device are equivalent to magnetic dipoles, thereby approximating the position and direction of the target positioning device. Preferably, the cross section of the exciting coil of the magnetic field generator may be circular in shape.

In the magnetic field target positioning method according to the second aspect of the present invention, the operation of calculating the position and orientation of the target positioning device may include: dividing the exciting coil 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 magnetic field target positioning method according to the second aspect of the present invention, the operation of calculating 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 may further include: 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.

In the magnetic field target positioning method according to the second aspect of the present invention, the operation of dividing the exciting coil into exciting coil sub-blocks may further include: dividing the exciting coil into M sections along the axial direction to obtain M sub-coil pieces, and segmenting the outline after the sub-coil pieces are equivalent to the outline of the sub-coil pieces. The operation of 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 may further include: 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. The operation of 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 may further include: 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. The operation of 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 spatial position and the direction may further include: 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.

According to a third 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 positioning method as in the second aspect of the present invention.

The invention provides a target positioning technology by utilizing an electromagnetic field positioning principle. The target positioning technology can be particularly used in medical operations, particularly interventional operations, and can ensure the positioning accuracy as much as possible under the condition that the size of a target object is excessively occupied.

In magnetic field positioning applications, the excitation coil of the magnetic field generator 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 implemented in accordance with the invention.

Fig. 2 is a schematic diagram of a magnetic field generating device implemented in accordance with the present invention.

Fig. 3A is a schematic diagram of a magnetic field generation control module according to an embodiment of the present invention.

Fig. 3B illustrates one of modulation results of the quadrature modulated signal according to an embodiment of the present invention.

Fig. 4 is a schematic workflow diagram of a signal acquisition module according to an embodiment of the invention.

Fig. 5 is a schematic diagram of magnetic field target localization according to an embodiment of the invention.

FIG. 6 is a flow chart of an iterative solution of target position and orientation in accordance with an embodiment of the present invention.

Fig. 7 is a flowchart of a magnetic field target positioning calculation method according to another embodiment of the invention.

Fig. 8 is a flowchart of a method of constructing a magneto-inductive electromotive force equation according to another embodiment of the present invention.

Fig. 9 is a schematic diagram of coordinates of an excitation coil using a cartesian coordinate system according to another embodiment of the invention.

Fig. 10 is a schematic view of an excitation coil having a rectangular cross section with rounded corners according to another embodiment of the invention.

Fig. 11 is a schematic view of an exciting coil according to another embodiment of the present invention, the cross section of which is a rounded triangle.

Fig. 12 is a schematic view of an excitation coil having another rounded rectangle in cross-section according to another embodiment of the invention.

Fig. 13 is a flow chart of a magnetic field target positioning method implemented in accordance with the present 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.

Magnetic field target positioning system

A magnetic field target positioning system according to the present invention may include a magnetic field generation control module, a magnetic field generating device, a target positioning device, a signal acquisition module, and a positioning calculation module.

The magnetic field generation control module is used for generating a signal for controlling the generation of a magnetic field.

The magnetic field generating device generates a magnetic field in space according to the signal generated by the magnetic field generating control module. In a preferred embodiment of the present invention, the magnetic field generating means may further comprise a plurality of magnetic field generators and fixing means for fixing the plurality of magnetic field generators. In a preferred embodiment, the plurality of magnetic field generators is at least 6 magnetic field generators. Each magnetic field generator is arranged at a different position or in a different arrangement direction in the magnetic field generating device to generate a corresponding magnetic field. 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. Each magnetic field generator includes an excitation coil.

It will be understood by those skilled in the art that although terms such as "magnetic field generating means", "magnetic field generator", "exciting coil" and the like 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 and the like may also be used to express the same or similar meaning.

The target positioning device is positioned in the magnetic field generated by the magnetic field generating device 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.

The signal acquisition module is used for acquiring magnetic induction signals generated at the target positioning device. Due to the presence of the magnetic field, a magnetic induction signal is generated at the target positioning means, i.e. the positioning sensor coil. The signal acquisition module acquires the magnetic induction signal for analysis by a method described below, thereby enabling positioning of the target positioning device.

The positioning calculation is performed by a positioning calculation module. That is, the positioning calculation module calculates the position and direction of the target positioning device according to the magnetic induction signals acquired by the magnetic field signal acquisition module.

Those skilled in the art will appreciate that the positioning calculation module may be a software calculation module, i.e. the calculation operations described are performed entirely by algorithm programming on a general purpose computer. The positioning calculation module may also be a hardware module or a firmware module, which performs the positioning calculation operation 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 manner of the magnetic field generation control will be explained below.

The magnetic field generation control module is responsible for driving the magnetic field generator to generate a magnetic field. Common driving modes include: alternating current drive, collimated current drive, or permanent magnet drive.

The alternating current drive mode is first seen. The magnetic field generation control module generates alternating currents of a plurality of frequencies. Each magnetic field generator generates a corresponding magnetic field from the respective frequency current generated by the magnetic field generation control module, thereby generating a frequency modulated magnetic field containing the respective frequency.

The alternating current mode has the advantages that the alternating current frequency point is single, and the single frequency point signal is not easy to interfere with other equipment. Generally, the frequency range of the electrophysiological signal is 0.02 Hz-2 KHz, and the frequency requirement of the electrophysiological signal related equipment is high, so that the frequency point of the alternating current is not set in the range of 0.02 Hz-2 KHz, and the output of the control signal can not influence the electrophysiological signals of other equipment as long as the frequency point of the alternating current signal is set above 2 KHz.

However, the alternating current drive has the problem that the alternating current generates an alternating magnetic field, and other conductors than the target positioning device (e.g. other devices or components on the operating table, such as the head of an X-ray machine in particular) generate induced currents in the magnetic field, so that eddy currents are generated, which influence the magnetic field generator to generate an alternating magnetic field, so that the calculated position and direction of the target positioning device (sensor coil) are inaccurate.

And then look at the quasi-dc driving mode. The magnetic field generation control module generates square wave current, and each magnetic field generator can receive the square wave current in a time sharing way and generate corresponding magnetic fields, so that the magnetic fields are generated in time sequence.

The advantage of adopting the collimation flow mode to drive is that the collimation flow mode is adopted to time-share and send square wave signals to each magnetic field generator (exciting coil), and each magnetic field generator works in time-share and in turn, so that the signal components of each magnetic field generator acting on the detector can be demodulated according to time sequence. Because the control signal is a square wave signal, the frequency spectrum range of the square wave signal is usually a frequency range of hundreds of Hz to 2KHz, therefore, when a target positioning device (usually a sensor coil with an iron core) is placed in a magnetic field, the iron core can not generate eddy current due to the wider frequency range of the square wave signal, and the eddy current generated by driving in an alternating current mode is overcome, so that the problem of inaccurate target positioning is solved.

The disadvantage of the quasi-dc mode of driving is that the frequency spectrum of the square wave signal falls within the frequency range of the electrophysiological signal, and the square wave signal is adopted for driving, which is easy to affect the electrophysiological signal of other devices, and the frequency is low, so that the volume size of the exciting coil and the target positioning device (positioning sensor coil) is larger.

Finally, the permanent magnet driving mode is adopted. The alternating magnetic field can be generated by driving the permanent magnet to rotate (for example, by using a motor) through the magnetic field generation control module. The method for generating the magnetic field by driving is mainly applied to occasions such as surgical operation, household Virtual Reality (VR) application positioning and the like.

The permanent magnet is driven to rotate at a speed not too high, for example, if the electrode is rotated at 3000 rpm, the corresponding frequency is 50Hz, and no eddy current is generated at such frequency, but an electrophysiological signal of about 50Hz is affected.

After determining the magnetic field drive generation pattern, the signal acquisition module may decompose the respective magnetically induced signal components of each magnetic field generator acting on the target positioning device according to the magnetic field generation pattern. For example, for alternating magnetic fields, the respective magnetically induced signal components of each magnetic field generator acting on the target sensor coil may be obtained by means of frequency demodulation. For the magnetic field generated by the collimation flow driving, as the magnetic field generator generates the magnetic field in a time-sharing way, the signal acquisition module can acquire the magnetic induction signal in a time-sharing way, so as to obtain the corresponding magnetic induction signal component of the action time period of each magnetic field generator.

Then, in a positioning calculation module, the position and orientation of the target positioning device are solved based on a system of equations of the Biot-Savart Law (Biot-Savart Law) from the respective magnetically induced signal components that each magnetic field generator acts on the target positioning device.

A magnetic field target positioning system according to an embodiment of the invention is explained in more detail below with reference to the accompanying drawings.

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 implemented in accordance with the present invention. 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. 3A is a schematic diagram of a magnetic field generation control module according to an embodiment of the present invention. In the preferred embodiment shown in fig. 3A, the magnetic field generator in the magnetic field generating device generates an alternating magnetic field by driving of the magnetic field generating control module. In this preferred embodiment, the function of the magnetic field generation control module is to modulate the quadrature signal, and to amplify and drive the magnetic field generator to generate the alternating magnetic field. As shown in fig. 3A, the magnetic field generation control module 300 comprises a signal generator 301 comprising, for example, k signal generators, denoted signal generator 1, signal generator 2, … …, signal generator k in fig. 3A, respectively, with a base frequency of 2KHz (other frequencies may also be selected), the signal generator parameters being set by step-wise addition of λ KHz (e.g. λ=0.1). The signal modulator 302 modulates the signal in a quadrature manner. Fig. 3B illustrates one of modulation results of the quadrature modulated signal according to an embodiment of the present invention. The signal amplifier 303 amplifies the modulated signal according to a variable gain factor, wherein the gain factor is set according to the digital acquisition unit unsaturated as much as possible to amplify the signal. Thus, the driving signal generator 304 generates a driving signal to drive each magnetic field generator to generate an alternating magnetic field.

Fig. 4 is a schematic workflow diagram of a signal acquisition module according to an embodiment of the invention. In the case of alternating magnetic fields, the function of the signal acquisition module is to acquire alternating magnetic induction signals generated by the object positioning device in the generated alternating magnetic field and demodulate signal components generated by each magnetic field generator applied to the object positioning device (sensor coil) according to modulation parameters in the magnetic field generation control module. As shown in fig. 4, the workflow 400 of the signal acquisition module starts in step 401, where an AD-acquisition device is used to acquire a signal B on a target object in a magnetic field, i.e. a magnetic induction signal B generated by acting on a target positioning device (positioning sensor coil). In step 402, it is determined whether the AD collector is saturated. If it is determined that the AD collector is not saturated, in step 403, the no branch of step 402, the signal amplification factor is adjusted according to the principle that the AD collector is not saturated as much as possible to amplify the signal. Otherwise, it is determined that the AD collector is saturated, in step 404, the yes branch of step 402, the collected signals are demodulated according to the signal modulation mode of the signal modulator 302 in fig. 3A, so as to obtain signal components generated by each magnetic field generator acting on the target object (i.e. the target positioning device). Finally, in step 405, the obtained signal component is output.

Fig. 5 is a schematic diagram of magnetic field target localization according to an embodiment of the invention. In the coordinate system 500 shown in fig. 5, the magnetic field generating means comprises magnetic field generator sets 501A, 501B, 501C, 501D, each set comprising 3 magnetic field generators. For example, the magnetic field generator 502 is one magnetic field generator in the magnetic field generator group 501C, 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) 503 is also in the coordinate system 500. 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 503 are variables to be solved.

Magnetic dipole equivalent embodiment

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 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 502, 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 demodulation result output in step 405 in fig. 4:

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 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. Since the number of unknowns is 6, it is necessary to ensure that the number of equations remaining after the elimination of part of the equations is 6 or more, and typically the number of equations is 6 to 12, and preferably the number of 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 And (3) selecting the sum of the modulus with the maximum value from the equation sets, finding 3 signal quantities corresponding to the sum of the modulus with the maximum value, removing equations corresponding to the 3 signal quantities from the 12 equation sets, and combining the rest 9 equations to form an optimal overdetermined equation set to participate in final solving.

FIG. 6 is a flow chart of an iterative solution of target position and orientation in accordance with an embodiment of the present invention. As shown in fig. 6, the target position and orientation solving process 600 begins at step 601 where the demodulated signals output at step 405 of fig. 4 are input, each of the demodulated signals corresponding to a signal component generated by the magnetic field generator acting on the target positioning device. The signal component is acquired under optimal parameters for amplifying the signal as much as possible (step 403) when the digital acquisition unit is determined to be not saturated in step 402 of fig. 4. Next, in step 602, it is determined whether the result is not resolved 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 602, the current round of solution is stopped in step 604, and the solution failure is output. If the number of times exceeds the preset value, i.e. the no branch of step 602, step 603 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 603, step 605 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 603, step 606 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 607, a common method being the LM (Levenberg-Marquardt) algorithm or its modified version. At step 608, a determination is made as to whether the iteration is converging. If convergence, yes branch of step 608, then the successful solution is marked in step 609, and then the solution result is output in step 610; if convergence fails, i.e., the no branch of step 608, the process returns to step 602 to determine whether the number of failures exceeds a preset number.

Examples of the general case

In the magnetic dipole equivalent embodiment, according to the Biot-Savart Law (Biot-Savart Law) column equation, since the distance between the magnetic field generator and the object is far greater than the size of the magnetic field generator, the two are regarded as magnetic dipoles, and the equation is deduced:

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 x component, B, of the magnetic induction generated by the ith magnetic field generator 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, it is necessary to set the cross section of the coil in the magnetic field generator to other shapes, such as a rounded rectangle in fig. 10. 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 position calculation method, so that exciting coils with different cross sections can perform magnetic positioning calculation, and accurate positioning of a target object is realized.

Fig. 7 is a flowchart of a magnetic field target positioning calculation method according to another embodiment of the invention. As shown in fig. 7, the magnetic field target positioning calculation method 700 includes the steps of:

s710: dividing the exciting coil into exciting coil sub-blocks;

s720: 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;

s730: 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);

s740: based on the magnetic induction intensity signal at the target positioning device acquired by the magnetic field signal acquisition module and the relationship between the magnetic induction intensity generated in space by the exciting coil and the spatial position and direction (pitch angle and rotation angle) obtained in step S730, the spatial position coordinates and direction (pitch angle and rotation angle) of the target positioning device (sensor coil) are solved.

In step S720, 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.

The method for constructing the magnetomotive force equation is an important step of the present invention, and a flowchart of a method 800 for constructing the magnetomotive force equation is shown in fig. 8, and specifically includes the following steps:

s810: 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 S710 of FIG. 7;

s820: 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 S720 of FIG. 7;

s830: 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 S730 of FIG. 7;

S840: 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 S830 is equal to the magnetic induction intensity of the sensor coil obtained in this step in the P normal vector direction 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 S740 of fig. 7.

Fig. 9 is a schematic diagram of coordinates of an excitation coil using a cartesian coordinate system according to another embodiment of the invention. As shown in FIG. 9, the excitation coil is centered at the origin of coordinates using a Cartesian coordinate system, the axial vector points in the Z direction, the cross-sectional vector points in the X and Y directions, and the excitation is performed in the Z directionCoil slicing, namely equivalent to M thin coils (sub-coil pieces) with length H, wherein the center position Z=0 of the exciting coil and the center position of the ith thin coil are

Fig. 10 is a schematic view of an excitation coil having a rectangular cross section with rounded corners according to another embodiment of the invention. Fig. 11 is a schematic view of an exciting coil according to another embodiment of the present invention, the cross section of which is a rounded triangle. Fig. 12 is a schematic view of an excitation coil having another rounded rectangle in cross-section according to another 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. 10, 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. 11, or another rounded rectangle in fig. 12. The common point of fig. 10, 11 and 12 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 that the magnetic induction intensity component of the ith section in the jth profile at any point P in the magnetic field is within the corresponding length or angle rangeAnd (5) integrating.

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. The measured magnetic induction electromotive forceAnd the calculated coefficient k is substituted into epsilon=k· (B '·vp'), so that a simultaneous equation set can be used, and since the three-dimensional space position coordinates of the P point are contained in B ', vp' is characterized 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.

It will be appreciated by those skilled in the art that although magnetic dipole equivalents are employed in the above embodiment, the teachings herein with respect to solving the system of overdetermined equations, LM algorithm solution iterations, are applicable to this embodiment.

Magnetic field target positioning method

A magnetic field target positioning method according to an embodiment of the present invention is described below in its entirety.

As shown in fig. 13, a magnetic field target positioning method 1300 according to an embodiment of the invention starts at step S1310. In step S1310, a signal for controlling the generation of the magnetic field is generated. As can be appreciated by reference to fig. 1 and the description thereof, the signal controlling the generation of the magnetic field may be provided by the magnetic field generation control module.

The generated signal controlling the occurrence of the magnetic field comprises alternating currents of a plurality of frequencies. This situation may be referred to as alternating current drive.

The generated signal controlling the generation of the magnetic field comprises a square wave current. This situation may be referred to as collimated flow driving.

In step S1320, a magnetic field is generated in space according to the generated signal for controlling the generation of the magnetic field. In particular, a plurality of magnetic field generators (see fig. 1) fixed to the fixture may be employed to generate a magnetic field in space. The plurality of magnetic field generators may be at least 6 magnetic field generators. 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 the case of alternating current drive, each magnetic field generator generates a corresponding magnetic field from the generated current of the respective frequency, thereby generating a frequency modulated magnetic field containing the respective frequency.

In the case of collimated flow driving, each magnetic field generator receives a square wave current in time-sharing and generates a corresponding magnetic field, thereby generating magnetic fields in time-series.

Next, in step S1330, magnetic induction signals generated by the object positioning device in the magnetic field are acquired. It will be appreciated by those skilled in the art that in a preferred embodiment of the present invention, the target positioning device is located on a medical device for medical intervention into the living being. More specifically, the object positioning device is a positioning sensor coil. In particular, in this step, the respective magnetically induced signal components of each magnetic field generator acting on the object positioning device are resolved in accordance with the manner of magnetic field generation, e.g. alternating current drive or collimated current drive. For example, where the alternating current drive generates a quadrature modulated magnetic field signal, the decomposition herein may include quadrature demodulation or Fast Fourier Transform (FFT).

Finally, in step S1340, the position and direction of the target positioning device are calculated according to the acquired magnetic induction signals. Specifically, at this step, based on the biot-savart law, the system of equations solves the position and orientation of the target positioning device from the respective magnetically induced signal components that each magnetic field generator acts on the target positioning device. According to a preferred embodiment of the invention, the position and orientation of the target positioning device comprises the three-dimensional coordinates, pitch angle and rotation angle of the target positioning device.

More specifically, in order to solve the equation set using the approximation method, it is necessary to reject an equation unsuitable for the approximation method from the equation set. Thus, the step of solving the system of equations for the position and orientation of the target positioning device may further comprise: 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.

In addition, in solving the equation set, the Levenberg-Marquardt (LM) algorithm or its modified algorithm may be utilized due to the need to iteratively solve the position and orientation of the target positioning device.

In a preferred embodiment of the approximate solution, the cross-sectional shape of the field coil of the magnetic field generator is such that the field coil of the magnetic field generator and the target positioning means are equivalent to magnetic dipoles, thereby approximating the position and orientation of the target positioning means. For example, the cross section of the field coil of the magnetic field generator is circular in shape, and the field coil may be equivalent to a magnetic dipole.

Of course, the cross-sectional shape of the field coil of the magnetic field generator may be such that the field coil of the magnetic field generator cannot be equivalently a magnetic dipole. For example, the cross section of the exciting coil of the magnetic field generator is a shape other than a circle.

In order to adapt to the more general situation, namely the situation that the cross section of the exciting coil is of any shape, the invention provides a more general and applicable method for calculating the position and the direction of the target positioning device. The method comprises the following steps: dividing the exciting coil 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.

Taking each excitation coil sub-block as a current element, and calculating the magnetic induction intensity of any point P of each excitation coil sub-block in space, wherein the method specifically comprises the following steps: and obtaining the magnetic induction intensity of the excitation coil sub-blocks at any point P in space based on the Biao-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.

More specifically, the exciting coil is divided into M segments in the axial direction to obtain M sub-coil pieces, and the sub-coil pieces are equivalent to the outline of the sub-coil pieces, and then the outline is segmented. Then, the magnetic induction intensity component of each section of the contour at any point P in the magnetic field is calculated by using the Biaoo-savart law. And 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. The magnetic induction intensity of the sensor coil of the target positioning device in the direction of the P normal vector is listed according to the law of electromagnetic induction. The normal vector refers to the normal unit vector at the sensor coil cross section. 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.

The magnetic field target positioning system and the magnetic field target positioning method are applicable to all fields and application scenes in which target positioning is required, for example, the magnetic field target positioning system and 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 stored thereon instructions executable by a processor, which instructions, when executed by the processor, cause the processor to perform a magnetic field target positioning method as described above, or may also cause the processor to perform only the operation of calculating the position and orientation of a target positioning device from the acquired magnetic induction signals as described above.

Thus, according to the present disclosure, a computer program or a computer program product may also be proposed which, when executed, may implement the magnetic field object localization method as described above, or may perform only the operation of calculating the position and orientation of the object localization device from the acquired magnetic induction signals as described above.

In addition, the invention also relates to a computing device or a computing system for magnetic field target positioning, 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 method as described above.

Alternatively, the invention also relates to a computing device or computing system comprising a processor and a memory, said memory having stored therein a computer program which, when executed by said processor, enables only the operation of calculating the position and orientation of said object localization device from the acquired magnetic induction signals 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. according to the magnetic field target positioning system and method provided by the embodiment of the invention, the position and direction of the sensor are solved based on the signal component generated by the target positioning sensor coil in the magnetic field and the position and placement angle of the magnetic field generator for generating the magnetic field, so that the accurate positioning of a target object (sensor coil) is realized.

2. The magnetic field components generated by the magnetic field generators in each group are orthogonal to each other by arranging the magnetic field generators in groups, so that the magnetic field components of the magnetic field generators are in corresponding relation with the positions and the arrangement angles of the magnetic field generators, and the positions and the arrangement angles of the magnetic field generators are more accurate.

3. The control signal for driving the magnetic field generator to generate the magnetic field component is a quasi-direct current signal or an alternating current modulated quadrature signal. When the control signal is a modulation orthogonal signal, the modulation orthogonal signal is a plurality of frequency division multiplexing signals taking a certain basic frequency as a basis and taking a certain step length as a variable, and the frequency division multiplexing signals are used for simultaneously driving a plurality of magnetic field generators to generate alternating magnetic fields. On the other hand, when the control signal is a quasi-direct current signal, time-sharing driving of the plurality of magnetic field generators can be realized, so that the magnetic field generators generate corresponding magnetic fields in a time-sharing manner.

4. 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.

5. The invention also discloses a magnetic field target position calculation method, 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 rotating angle is established. The method has the advantages that in the magnetic positioning system, the cross section of the exciting coil is expanded more, not necessarily round, but also round-corner rectangular, or round-corner triangle and combination of line segments and arcs, so that more possibility is provided for manufacturing and installing the exciting coil, even if the distance between the exciting coils is very close, the exciting coils cannot be equivalently a magnetic dipole, and the signal component generated by the exciting coil acting on the sensor coil can still be accurately calculated by adopting the method, thereby realizing accurate positioning of an object (the sensor coil).

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

1. A magnetic field target positioning system, comprising:

the magnetic field generation control module is used for generating a signal for controlling the generation of a magnetic field;

a magnetic field generating device for generating a magnetic field in space according to the signal generated by the magnetic field generating control module;

the target positioning device is positioned in the magnetic field generated by the magnetic field generating device and generates a magnetic induction signal;

the signal acquisition module is used for acquiring magnetic induction signals generated at the target positioning device;

the positioning calculation module is used for calculating the position and the direction of the target positioning device according to the magnetic induction signals acquired by the magnetic field signal acquisition module;

the magnetic field generating device further comprises a plurality of magnetic field generators;

each magnetic field generator is arranged at a different position or in a different arrangement direction in the magnetic field generating means to generate a corresponding magnetic field,

each magnetic field generator includes an excitation coil;

The positioning calculation module is configured to: based on the Biaor-Saval law, solving the position and the direction of the target positioning device according to the corresponding magnetic induction signal components acted on the target positioning device by each magnetic field generator by a system of equations;

further comprises:

calculating a modulus value of the signal component;

obtaining signal components with maximum and/or minimum modulus values, and removing equations corresponding to the signal components in an equation set;

the rest equations form an optimized overdetermined equation set, and the position and the direction of the target positioning device are solved;

the magnetic field generating device further comprises a plurality of magnetic field generators and fixing means for fixing the plurality of magnetic field generators,

each magnetic field generator includes an excitation coil;

dividing the exciting coil into a plurality of 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

obtaining the position and the direction of the target positioning device based on the magnetic induction intensity signal at the target positioning device acquired by the magnetic field signal acquisition module and the relationship between the magnetic induction intensity generated by the exciting coil in space and the space position and the direction;

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 the straight line segments or the arcs at P to obtain magnetic induction intensity of the straight line segments or the arcs at P; and (3) 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 spatial position and direction.

2. The system of claim 1, wherein the target positioning device is located on a medical device for medical intervention into the living being.

3. The system of claim 1, the computing being a discretization of the magnetic field generating device.

4. The system of claim 1, wherein the target positioning device is a positioning sensor coil.

5. The system of claim 1, wherein the magnetic field generation control module is configured to generate alternating currents of a plurality of frequencies, each magnetic field generator being configured to generate a respective magnetic field from the respective frequency currents generated by the magnetic field generation control module, thereby generating a frequency modulated magnetic field comprising the respective frequency.

6. The system of claim 1, wherein the magnetic field generation control module is configured to generate a square wave current, each magnetic field generator configured to receive the square wave current in time-sharing rotation and generate a corresponding magnetic field, thereby generating magnetic fields in time-sharing sequence.

7. The system of claim 5 or 6, wherein the signal acquisition module is configured to decompose respective magnetically induced signal components of each magnetic field generator acting on the object positioning device in accordance with a magnetic field generation pattern.

8. The system of claim 1, wherein said solving the position and orientation of the target positioning device from the system of equations based on the respective magnetically induced signal components of each magnetic field generator acting on 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.

9. The system of claim 1, wherein said solving the position and orientation of the target positioning device from the system of equations based on the respective magnetically induced signal components of each magnetic field generator acting on 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.

10. The system 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.

11. The system of claim 1, wherein the plurality of magnetic field generators is at least 6 magnetic field generators.

12. The system of claim 1, wherein the cross-sectional shape of the field coil of the magnetic field generator is such that the field coil of the magnetic field generator and the target positioning device are equivalent to magnetic dipoles, thereby approximating the position and orientation of the target positioning device.

13. The system of claim 12, wherein the field coil of the magnetic field generator is circular in cross-section.

14. The system of claim 1, wherein the cross-sectional shape of the field coil of the magnetic field generator is such that the field coil of the magnetic field generator cannot be equivalently a magnetic dipole.

15. The system of claim 14, wherein the cross section of the field coil of the magnetic field generator is a shape other than circular.

16. The system 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.

17. The system of claim 1, wherein:

the said dividing the said exciting coil into several exciting coil sub-blocks, further includes: 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 obtaining the position and the direction of the target positioning device based on the magnetic induction intensity signal at the target positioning device collected by the magnetic field signal collection module 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.

18. A magnetic field target positioning method, comprising:

generating a signal for controlling the generation of the magnetic field;

generating a magnetic field in space according to the generated signal for controlling the generation of the magnetic field;

Collecting magnetic induction signals generated by a target positioning device in the magnetic field;

calculating the position and the direction of the target positioning device according to the collected magnetic induction signals;

the calculating the position and the direction of the target positioning device comprises the following steps: based on the Biaor-Saval law, solving the position and the direction of the target positioning device according to the corresponding magnetic induction signal components acted on the target positioning device by each magnetic field generator by a system of equations;

further comprises:

calculating a modulus value of the signal component;

each magnetic field generator includes an excitation coil;

19. The method of claim 18, wherein the calculation is a discretized calculation of the magnetic field.

20. The method of claim 18, wherein the target positioning device is located on a medical device for medical intervention into the living being.

21. The method according to claim 18, wherein:

a plurality of magnetic field generators fixed to a fixture are employed to generate a magnetic field in space,

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.

22. The method of claim 18, wherein the object positioning device is a positioning sensor coil.

23. The method of claim 21, wherein generating the signal that controls the generation of the magnetic field comprises generating alternating currents of a plurality of frequencies, and wherein generating the magnetic field in space comprises each magnetic field generator generating a corresponding magnetic field based on the generated currents of the respective frequencies, thereby generating a frequency modulated magnetic field comprising the respective frequencies.

24. The method of claim 21, wherein generating the signal that controls the generation of the magnetic field comprises generating a square wave current, and wherein generating the magnetic field in space comprises each magnetic field generator receiving the square wave current in time-sharing rotation and generating a corresponding magnetic field, thereby generating the magnetic field in time-sharing.

25. The method of claim 23 or 24, wherein said acquiring the magnetic induction signal generated by the object positioning device in the magnetic field comprises: and decomposing corresponding magnetic induction signal components acted on the target positioning device by each magnetic field generator according to a magnetic field generation mode.

26. The method of claim 18, wherein said solving the position and orientation of the target positioning device from the system of equations based on the respective magnetically induced signal components applied to the target positioning device by each magnetic field generator further comprises:

27. The method of claim 18, wherein said solving the position and orientation of the target positioning device from the system of equations based on the respective magnetically induced signal components applied to the target positioning device by each magnetic field generator further comprises:

28. The method of claim 18, wherein the position and orientation of the target positioning device comprises three-dimensional coordinates, pitch angle, and rotation angle of the target positioning device.

29. The method of claim 21, wherein the plurality of magnetic field generators is at least 6 magnetic field generators.

30. The method of claim 21, wherein the cross-sectional shape of the field coil of the magnetic field generator is such that the field coil of the magnetic field generator and the target positioning device are equivalent to magnetic dipoles, thereby approximating the position and orientation of the target positioning device.

31. The method of claim 30, wherein a cross-section of the field coil of the magnetic field generator is circular in shape.

32. The method of claim 21, wherein the cross-sectional shape of the field coil of the magnetic field generator is such that the field coil of the magnetic field generator cannot be equivalently a magnetic dipole.

33. The method of claim 32, wherein the cross-section of the field coil of the magnetic field generator is a shape other than circular.

34. The method of claim 21, wherein said calculating the position and orientation of the object-locating device comprises:

dividing the exciting coil into a plurality of exciting coil sub-blocks;

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.

35. The method of claim 34, 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:

36. The method according to claim 34, wherein:

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 spatial 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.

37. 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 localization method of claim 18.