CN114543645A

CN114543645A - Magnetic field target positioning system and method

Info

Publication number: CN114543645A
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: 2022-05-27
Anticipated expiration: 2042-02-21
Also published as: CN114543645B

Abstract

The invention discloses a magnetic field target positioning system and a magnetic field target positioning method. The magnetic field object locating 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; the magnetic field generating device generates a magnetic field in the space according to the signal generated by the magnetic field generation control module; the target positioning device is positioned in the magnetic field generated by the magnetic field generating device and generates magnetic induction signals; the signal acquisition module is used for acquiring magnetic induction signals generated by 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 operations, particularly interventional operations, and can ensure the positioning accuracy as much as possible under the condition of not occupying the size of a target object excessively. The more generally applicable positioning calculation method provided by the invention does not limit the cross section of the excitation 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 object location systems and methods.

Background

In modern medical technology, living tissues can be treated by introducing consumables such as catheters and sheath tubes into living bodies. However, in the operation, a target object such as a catheter, a guide wire, an introducer (sheath), or a probe needs to be accurately positioned and tracked. When different organism tissues are subjected to interventional therapy, the positioning precision is different, and generally, the higher the precision is, the better the positioning is, and the more accurate the positioning is.

Since the target object such as a catheter is usually introduced into the body through a blood vessel, an alimentary canal, etc., the target object itself is designed to be small in size, and if a positioning device with a certain size is additionally added, the target object does not meet the requirement of being introduced into the body in size. In addition, although the position of the target object can also be observed by means of images such as X-rays, magnetic resonance imaging, etc., such a position generally does not meet the positioning accuracy requirements at the surgical level.

Therefore, it is desirable to provide a target positioning technique that can be used in medical surgery, particularly in interventional surgery, and can ensure positioning accuracy as much as possible without occupying an excessive size of the target.

Disclosure of Invention

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

According to a first aspect of the present invention, a magnetic field object localization 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; the magnetic field generating device generates a magnetic field in the space according to the signal generated by the magnetic field generation control module; the target positioning device is positioned in the magnetic field generated by the magnetic field generating device and generates magnetic induction signals; the signal acquisition module is used for acquiring magnetic induction signals generated by 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 target locating system according to the first aspect of the present invention, the target locating device may be located on a medical device that is medically intervened in a living body.

In the magnetic field object localization system according to the first aspect of the present invention, the calculation is a discretization calculation applied to the magnetic field generating means. The discretization calculation comprises the steps of dividing a magnetic field generator in the magnetic field generating device into sub-modules according to different dimensions, and performing discretization processing, so that the positioning calculation module calculates the position and the direction of the target positioning device by using each sub-module, and then performs synthesis to obtain a final result.

In the magnetic field object locating system according to the first aspect 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. Each magnetic field generator may be disposed at a different location or different orientation in the magnetic field generating device to generate a corresponding magnetic field. Furthermore, each magnetic field generator includes an excitation coil.

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

In the magnetic field object localization system according to the first aspect of the present 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 corresponding magnetic field from the currents of the respective frequency 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 turn in a time-sharing manner and generate a corresponding magnetic field, thereby generating the magnetic fields in a time sequence.

Correspondingly, the signal acquisition module is configured to resolve the respective magnetic induction signal component of each magnetic field generator acting on the target positioning device according to the magnetic field generation manner.

In the magnetic field object locating system according to the first aspect of the present invention, the location calculation module may be configured to: based on the biot-savart law, the position and direction of the target positioning device are solved according to the corresponding magnetic induction signal component of each magnetic field generator acting on the target positioning device and the column equation set.

Preferably, the above operation may further include: calculating a modulus value of the signal component; obtaining a signal component with the maximum and/or minimum modulus value, and removing an equation corresponding to the signal component; and forming an optimized overdetermined equation set by the rest equations, and solving the position and the direction of the target positioning device.

Preferably, the above operation may further include: dividing the signal components into a plurality of groups equally, and calculating the sum of signal modulus of each group; comparing the signal modulus sums of all groups to obtain a signal component group with the maximum modulus sum value and/or the minimum modulus sum value, and removing an equation corresponding to the signal component group; and forming an optimized overdetermined equation set by the rest equations, and solving the position and the direction of the target positioning device.

Preferably, the position and orientation of the object-locating device is solved iteratively in accordance with 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 comprises three-dimensional coordinates, a pitch angle and a rotation angle of the object positioning device.

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

In the magnetic field object locating system according to the first 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 object locating device are equivalent to a magnetic dipole, thereby approximately calculating the position and the orientation of the object locating device. Preferably, the excitation coil of the magnetic field generator may be circular in cross-section.

Alternatively, the shape of the cross-section of the field coil of the magnetic field generator may be such that the field coil of the magnetic field generator cannot be equated to a magnetic dipole. Preferably, the excitation coil of the magnetic field generator may also have a cross-section of a shape other than a circle.

In the magnetic field object localization system according to the first aspect of the present invention, the localization calculation module may be further configured to: dividing the excitation coil into excitation coil sub-blocks; taking each excitation coil subblock as a current element, and calculating the magnetic induction intensity of each excitation coil subblock at any point P in space; superposing the magnetic induction intensity of each excitation coil subblock at any point P in space to obtain the relation 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 signals at the target positioning device acquired by the magnetic field signal acquisition module and the relation between the magnetic induction intensity generated by the excitation coil in the space and the space position and direction.

Preferably, said 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 subblocks at any point P in the space based on the Biao-Saval law according to the position and the placing direction of each excitation coil subblock serving as a current element and the current intensity of the excitation coil subblocks.

Preferably, the dividing the excitation coil into excitation coil sub-blocks may further include: dividing the excitation coil into M sections along the axial direction to obtain M sub-coil pieces, and after the sub-coil pieces are equivalent to the contour of the sub-coil pieces, segmenting the contour. The calculating the magnetic induction intensity of each excitation coil subblock at any point P in the space by using each excitation coil subblock as a current element may further include: and calculating the magnetic induction intensity component of each section of the profile at any point P in the magnetic field by adopting the Biao-Saval law. The magnetic induction intensity of each excitation coil subblock at any point P in the space is superposed to obtain the relationship between the magnetic induction intensity generated by the whole excitation coil in the space and the spatial position and direction, and the method can further comprise the following steps: superposing the magnetic induction intensity components of the sections of the profile in P to obtain the magnetic induction intensity of the profile in P; and superposing the magnetic induction intensity of the M profiles in the P direction in the axial direction to obtain the magnetic induction intensity of the excitation coil in the P direction, so that the relation between the magnetic induction intensity of the whole excitation coil in the space and the space position and direction is obtained. The obtaining the position and the direction of the target positioning device based on the magnetic induction signal at the target positioning device acquired by the magnetic field signal acquisition module and the relationship between the magnetic induction generated by the excitation coil in space and the spatial position and direction may further include: listing the magnetic induction intensity of a sensor coil of the target positioning device in the direction of a normal vector P 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 listing a magnetic induction electromotive force equation according to the principle that the magnetic induction intensity of the excitation coil on the P direction vector is equal to the magnetic induction intensity of the sensor coil on the P normal vector, so that the position and the direction of the target positioning device are obtained through solving.

According to a second aspect of the invention, a magnetic field target locating method is provided. The method may include: generating a signal for controlling the generation of the magnetic field; generating a magnetic field in the 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 localization method according to the second aspect of the present invention, the target localization apparatus may be located on a medical apparatus that is medically intervened in a living body.

In the magnetic field target positioning method according to the second aspect of the present invention, the calculation is a discretization calculation of the magnetic field, and the discretization calculation includes dividing the magnetic field generator 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 synthesized to obtain a final result.

In the magnetic field target positioning method according to the second aspect of the present invention, a plurality of magnetic field generators fixed to a fixture may be employed to generate a magnetic field in space. Each magnetic field generator may be disposed at a different location or in a different orientation to produce a corresponding magnetic field. Also, each magnetic field generator may include an excitation coil.

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

In the magnetic field target locating method according to the second aspect of the present 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 magnetic fields in space may include each magnetic field generator generating a corresponding magnetic field in response to the generated current at the respective frequency, thereby generating a frequency modulated magnetic field containing 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 magnetic fields in space may comprise each magnetic field generator time-sharing receiving the square wave current in turn and generating a corresponding magnetic field, thereby generating magnetic fields in time sequence.

Accordingly, the operation of acquiring magnetic induction signals generated by the object-locating device in the magnetic field may include: and decomposing corresponding magnetic induction signal components of each magnetic field generator acting on the target positioning device according to the magnetic field generation mode.

In the magnetic field target locating method according to the second aspect of the present invention, the operation of calculating the position and orientation of the target locating device may include: based on the biot-savart law, the position and direction of the target positioning device are solved according to the corresponding magnetic induction signal component of each magnetic field generator acting on the target positioning device and the column equation set.

In the magnetic field object locating method according to the second aspect of the present invention, the operation of solving the position and orientation of the object locating device according to the respective magnetic induction signal component acting on the object locating device by each magnetic field generator may further include: calculating a modulus value of the signal component; obtaining a signal component with the maximum and/or minimum modulus value, and removing an equation corresponding to the signal component; and forming an optimized overdetermined equation set by the rest equations, 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 magnetic induction signal component corresponding to each magnetic field generator acting on the target positioning device and the column equation set may further include dividing the signal components equally 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, so that the signal components are divided into four groups, and the sum of the three moduli of each group is determined as the optimum), and calculating the sum of the signal moduli of each group; comparing the signal modulus sums of all groups to obtain a signal component group with the maximum modulus sum value and/or the minimum modulus sum value, and removing an equation corresponding to the signal component group; and forming an optimized overdetermined equation set by the rest equations, and solving the position and the direction of the target positioning device.

In the magnetic field object locating method according to the second aspect of the present invention, the operation of solving the position and orientation of the object locating device according to the respective magnetic induction signal component acting on the object locating device by each magnetic field generator may further include: iteratively solving the position and orientation of the object-locating device according to the Levenberg-Marquardt (LM) algorithm or a modified version thereof.

In the magnetic field target locating method according to the second aspect of the present invention, the position and orientation of the target locating device may include a three-dimensional coordinate, a pitch angle, and a rotation angle of the target locating device.

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

In the magnetic field object locating 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 object locating device are equivalent to a magnetic dipole, thereby approximately calculating the position and the direction of the object locating device. Preferably, the excitation coil of the magnetic field generator may be circular in cross-section.

In the magnetic field target locating method according to the second aspect of the present invention, the operation of calculating the position and orientation of the target locating device may include: dividing the excitation coil into excitation coil sub-blocks; taking each excitation coil subblock as a current element, and calculating the magnetic induction intensity of each excitation coil subblock at any point P in space; superposing the magnetic induction intensity of each excitation coil subblock at any point P in space to obtain the relation 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 excitation coil in the space and the space position and direction.

In the magnetic field target locating 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 by using each excitation coil sub-block as a current element may further include: and obtaining the magnetic induction intensity of the excitation coil subblocks at any point P in the space based on the Biao-Saval law according to the position and the placing direction of each excitation coil subblock serving as a current element and the current intensity of the excitation coil subblocks.

In the magnetic field target locating method according to the second aspect of the present invention, the operation of dividing the excitation coil into excitation coil sub-blocks may further include: dividing the excitation coil into M sections along the axial direction to obtain M sub-coil pieces, and after the sub-coil pieces are equivalent to the contour of the sub-coil pieces, segmenting the contour. The operation of calculating the magnetic induction intensity of each excitation coil subblock at any point P in the space by using each excitation coil subblock as a current element may further include: and calculating the magnetic induction intensity component of each section of the profile at any point P in the magnetic field by adopting the Biao-Saval law. The operation of superposing the magnetic induction intensities of the excitation coil sub-blocks at any point P in the space to obtain the relationship between the magnetic induction intensity generated by the whole excitation coil in the space and the spatial position and direction may further include: superposing the magnetic induction intensity components of the sections of the profile in P to obtain the magnetic induction intensity of the profile in P; and superposing the magnetic induction intensity of the M profiles in the P direction in the axial direction to obtain the magnetic induction intensity of the excitation coil in the P direction, so that the relation between the magnetic induction intensity of the whole excitation coil in the space and the space position and direction is obtained. The operation of obtaining the position and the direction of the object locating device based on the acquired magnetic induction signal at the object locating device and the relationship between the magnetic induction generated in the space and the spatial position and the spatial direction by the exciting coil may further include: listing the magnetic induction intensity of a sensor coil of the target positioning device in the direction of a normal vector P 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 listing a magnetic induction electromotive force equation according to the principle that the magnetic induction intensity of the excitation coil on the P and the magnetic induction intensity of the sensor coil on the P normal vector are equal, and solving to 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, the instructions, when executed by the processor, causing the processor to perform a magnetic field target localization method according to 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 of not occupying the size of a target object excessively.

In magnetic field positioning applications, the excitation coil of the magnetic field generator and the sensor coil of the object positioning device may be equivalent to a magnetic dipole. This equivalent setting allows a fast and approximate solution to the target location when the excitation coil has a circular cross-sectional shape. However, when the cross-sectional shape of the exciting coil is not circular but other shapes, the equivalent setting of the magnetic dipole cannot be applied.

The invention provides a more generally applicable positioning calculation method aiming at various cross-sectional shapes of the excitation coil. According to the calculation method, the excitation 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 superposed 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 through solving the equation.

In addition, for the over-determined equation set, an equation with a more accurate calculation result can be reserved, and an inaccurate equation is removed, so that an appropriate number of equations are reserved, and more accurate positioning calculation is carried out.

Similarly, the system of equations may be iteratively solved 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, and wherein:

FIG. 1 is a schematic diagram of a magnetic field object locating system implemented in accordance with the present 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 invention.

Fig. 3B illustrates one of the modulation results of a 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 present invention.

FIG. 5 is a schematic diagram of magnetic field target location according to an embodiment of the present invention.

FIG. 6 is a flowchart of an iterative solution of target position and orientation, according to an embodiment of the present invention.

FIG. 7 is a flow chart of a magnetic field target location calculation method according to another embodiment of the present invention.

Fig. 8 is a flowchart of a method of constructing a magnetic induction electromotive force equation according to another embodiment of the present invention.

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

Fig. 10 is a schematic view of a field coil having a rounded rectangular cross section according to another embodiment of the present invention.

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

FIG. 13 is a flow chart of a magnetic field target location method implemented in accordance with the present invention.

Detailed Description

The technical solution 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

The magnetic field target positioning system according to the invention can comprise a magnetic field generation control module, a magnetic field generation 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 the magnetic field.

The magnetic field generating device generates a magnetic field in the space according to the signal generated by the magnetic field generation control module. In a preferred embodiment of the 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 different positions or different arrangement directions in the magnetic field generating device to generate corresponding magnetic fields. The shape of the magnetic field generator can be adjusted according to the application, and the common form is 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 placing angle of the magnetic field generator can be adjusted according to the amplitude of the signal collected by 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 device", "magnetic field generator", "excitation coil", etc. are used in the present invention to describe a device for generating various levels of a magnetic field in space, other similar terms such as a magnetic generating unit, a magnetic generator, a magnetic generating coil, a location pad, etc. may be used to convey the same or similar meaning.

The target positioning device is positioned in the magnetic field generated by the magnetic field generating device and generates magnetic induction signals. According to an embodiment of the invention, the object localization means is a localization sensor coil. And installing the target positioning device on or in the target to be positioned. Thus, the position and orientation of the object is determined at the same time as the position and orientation of the coil of the positioning sensor is determined. In a preferred embodiment, the target-locating device is located on a medical device that is medically intervened in the living being. For example, the target may be a catheter, or more specifically, may be one or more electrodes on the catheter; an object localization device is also mounted on the catheter, proximate to the electrode, for locating the catheter or the electrode.

The position and orientation of the target positioning device includes the three-dimensional coordinates, pitch angle, and rotation angle of the target positioning device. More generally, the orientation of the target-locating device may also include the roll angle, but in the application of the present invention this dimension of roll angle is not of concern.

The signal acquisition module is used for acquiring magnetic induction signals generated by the target positioning device. Due to the presence of the magnetic field, a magnetic induction signal is generated on the object positioning means, i.e. the positioning sensor coil. The signal acquisition module acquires the magnetic induction signal for analysis by the method described below, so that the target positioning device can be positioned.

The positioning calculation is completed by the positioning calculation module. That is, the positioning calculation module calculates the position and the direction of the target positioning device according to the magnetic induction signal collected by the magnetic field signal collection module.

It will be appreciated by those skilled in the art that the position calculation module may be a software calculation module, i.e. programmed entirely by an algorithm to perform the described calculation operations on a general purpose computer. The positioning calculation module may also be a hardware module or a firmware module, and the positioning calculation operation is performed 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 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 methods include: alternating current drive, collimated current drive, or permanent magnet drive.

First, an alternating current driving method is described. The magnetic field generation control module generates alternating currents of a plurality of frequencies. Each magnetic field generator generates a corresponding magnetic field in accordance with the current of the respective frequency generated by the magnetic field generation control module, thereby generating a frequency-modulated magnetic field containing the respective frequency.

The alternating current mode driving 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 signals is 0.02 Hz-2 KHz, and the frequency requirements of the equipment related to the electrophysiological signals are high, so that the frequency point of the alternating current should not be set in the range of 0.02 Hz-2 KHz, and as long as the frequency point of the alternating current signals is set above 2KHz, the output of the control signal can not affect the electrophysiological signals of other equipment.

However, the problem with driving with alternating current is that the alternating current generates an alternating magnetic field, and conductors other 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) induce currents in the magnetic field, thereby generating eddy currents, and the eddy current signals may affect the magnetic field generator to generate the alternating magnetic field, so that the calculated position and direction of the target positioning device (sensor coil) are inaccurate.

Then, see the quasi-DC driving method. The magnetic field generation control module generates square wave currents, and each magnetic field generator can receive the square wave currents in turn in a time-sharing mode and generate a corresponding magnetic field, so that the magnetic fields are generated in a time sequence.

The advantage of adopting the collimated flow mode for driving is that the collimated flow mode is adopted, square wave signals are sent to the magnetic field generators (magnet exciting coils) in a time-sharing mode, and the magnetic field generators work in turn in a time-sharing mode, so that signal components of the magnetic field generators acting on the detector can be demodulated according to time sequence. Because the control signal is a square wave signal, and the frequency spectrum range of the square wave signal is usually a frequency range from hundreds of Hz to 2KHz, after the 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 wide frequency range of the square wave signal, so that the problem of inaccurate target positioning caused by the eddy current driven by an alternating current mode is solved.

The quasi-dc driving has the disadvantages that the frequency spectrum range of the square wave signal falls within the frequency range of the electrophysiological signal, the square wave signal driving is easy to affect the electrophysiological signals of other devices, and the frequency is low, so that the volume sizes of the excitation coil and the target positioning device (positioning sensor coil) are large.

And finally, a permanent magnet driving mode. The permanent magnet is driven (for example, driven by a motor) to rotate by the magnetic field generation control module, so that an alternating magnetic field can be generated. The mode of driving to generate the magnetic field is mainly applied to occasions such as surgical operations, household Virtual Reality (VR) application positioning and the like.

The permanent magnet is driven to rotate, the rotating speed of the permanent magnet is not too fast, for example, if the electrode rotates at 3000 rpm, the corresponding frequency is 50Hz, and the frequency does not generate eddy current, but the electrophysiological signals of about 50Hz are influenced.

After the magnetic field driving generation mode is determined, the signal acquisition module may resolve, according to the magnetic field generation mode, a corresponding magnetic induction signal component of each magnetic field generator acting on the target positioning device. For example, for an alternating magnetic field, the respective magnetic induction signal component of each magnetic field generator acting on the target sensor coil can be obtained by means of frequency demodulation. For the magnetic field generated by the drive of the collimated flow, because the magnetic field generator generates the magnetic field in a time-sharing manner, the signal acquisition module can acquire the magnetic induction signals in a time-sharing manner, so that corresponding magnetic induction signal components of each magnetic field generator in an action time period are obtained.

Then, in a positioning calculation module, according to the corresponding magnetic induction signal component acted on the target positioning device by each magnetic field generator, the position and the direction of the target positioning device are solved based on a Biot-Savart Law (Biot-Savart Law) column equation system.

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

As shown in fig. 1, a magnetic field target locating system 100 includes a magnetic field generating device 101. The magnetic field generating device 101 comprises a plurality of magnetic

field generator groups

102A, 102B, 102C, 102D, each comprising one or more magnetic field generators. For example, each magnetic field generator group comprises 3 magnetic field generators for generating magnetic fields. The system 100 further comprises a signal acquisition module 107 for acquiring modulation signals in the generated magnetic field, a magnetic field generation control module 108 whose main function is to modulate signals to drive the magnetic field generator to generate a magnetic field, and a positioning calculation module 109 for solving for the position and orientation of the object. As previously mentioned, the positions described herein may be represented in three-dimensional coordinates, while the orientations described herein may be represented in terms of pitch and roll angles. The target positioning device (also called sensor or detector) 103 is located on the target and has the function of detecting the magnetic field, i.e. magnetic induction signals can be generated by positioning the sensor coil in the magnetic field. One end of the cable 104 is connected to the object-locating 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 generation device 101, and the other end is connected to the magnetic field generation control module 108. In addition, the system 100 may further include 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, pitch angle, and rotation angle values 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 solution position and angle of the system of equations. Here, 12 magnetic field generators are described as an example. The outer shape of the magnetic field generator may be designed to be cylindrical, square, or other various shapes.

Furthermore, it will be appreciated by those skilled in the art that although the magnetic field generator (or even the magnetic field generating means) and the magnetic field generation control module are described herein as two components of a magnetic field object localization system, in many cases the magnetic field generator and the magnetic field generation control module may be integrated together. Thus, the present invention does not limit the magnetic field generator from being physically separated or integrated with the magnetic field generation control module, but only functionally differentiated. In other words, in the embodiment in which the magnetic field generator is integrated with the magnetic field generation control module, the relationship of the two can be regarded as the relationship of hardware and its drive, or the integration of the two can 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 groups of

magnetic field generators

202A, 202B, 202C, 202D, each group including 3 mutually orthogonal magnetic field generators. The internal structure 204 of the magnetic field generator group 202A will be described 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 invention. In the preferred embodiment represented in fig. 3A, the magnetic field generator in the magnetic field generating device generates an alternating magnetic field by the driving of the magnetic field generation control module. In the preferred embodiment, the magnetic field generation control module is operative to modulate the quadrature signal, which is amplified to drive the magnetic field generator to generate the alternating magnetic field. As shown in fig. 3A, the magnetic field generation control module 300 includes a signal generator 301 including, for example, k signal generators, which are respectively denoted as signal generator 1, signal generators 2, … …, and signal generator k in fig. 3A, and sets signal generator parameters by accumulating in steps of λ KHz (for example, λ ═ 0.1) with a base frequency of 2KHz (other frequencies may be selected). The signal modulator 302 modulates the signal in a quadrature manner. Fig. 3B illustrates one of the modulation results of the quadrature modulated signal in accordance with 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 principle that the digital collector does not saturate to amplify the signal as much as possible. Thus, the drive signal generator 304 generates drive signals to drive the respective magnetic field generators to generate the alternating magnetic field.

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

FIG. 5 is a schematic diagram of magnetic field target location according to an embodiment of the present invention. In the coordinate system 500 shown in fig. 5, the magnetic field generating means comprise groups of

magnetic field generators

501A, 501B, 501C, 501D, each group comprising 3 magnetic field generators. For example, the magnetic field generator 502 is a magnetic field generator set 501C, the position and the laying angle of which are known, P (x)_i,y_i,z_i,α_i,β_i). An object-locating device (locating sensor coil) 503 is also in the coordinate system 500. Common target objects provided with target positioning devices in the medical field include catheters, guide wires, introducers (sheaths), probes and the like, and the application fields include cardiac interventional therapy navigation, pulmonary bronchus positioning navigation, renal artery ablation navigation and the like. The spatial position and the placing angle P (x, y, z, α, β) of the target-positioning device 503 are variables to be solved.

Magnetic dipole equivalent embodiment

Because the distance between the magnetic field generator and the target object is far larger than the size of the magnetic field generator, the magnetic field generator and the target object can be regarded as magnetic dipoles.

According to the Biot-Savart Law, the localization principle is detailed as follows:

according to the position and the placing angle of the magnetic field generator 502, the 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) The pitch angle (polar angle) and the rotation angle (azimuth angle) of the magnetic field generator, where i denotes the number or index of the magnetic field generator, e.g. when there are N magnetic field generators, i is 1,2, …, N ≧ 6.

Target-to-field generator distance:

the ith magnetic field generator generates a signal volume Vol generated by the magnetic field acting on the target_iCorresponding 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 spatial position of the target object, (α, β) is the pitch angle (polar angle) and the rotation angle (azimuth angle) of the positioning sensor coil, γ is the gain coefficient, and P (x, y, z, α, β, γ) is 6 unknown quantities to be solved. Taking 12 magnetic field generators as an example, 12 equations containing 6 unknowns can be obtained to form an overdetermined system of equations in parallel.

Solving the problem of the overdetermined equation set is actually a nonlinear model solving problem, part (more than or equal to 6) or all of the equations 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 type thereof, and the improved type is adopted in the preferred embodiment of the invention, so that convergence can be obtained within 3-8 iterations.

The above equation set is an approximate calculation formula obtained by taylor expanding the calculation formula according to the biot-savart law and then taking the first harmonic component, so that the position and direction obtained by solving the over-determined 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 accurate. When the target positioning device is too close to the magnetic field generator, a response signal induced by a coil of the positioning sensor through an excitation signal of the magnetic field generator is very strong, the response signal is substituted into an equation, and the calculated position and direction errors are large and inaccurate; when the target positioning device is too far away from the magnetic field generator, a response signal induced by a coil of the positioning sensor through an excitation signal of the magnetic field generator is very weak, the response signal is substituted into an equation, and the calculated position and direction errors are large and inaccurate. Therefore, in the actual calculation process, equations corresponding to signal components that are too close to each other or too far from each other need to be removed, or equations corresponding to signal components that are too close to each other or too far from each other can be removed. The response signal components of each equation 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 into a plurality of groups, such as N groups, and calculating the sum of the signal modulus of each group;

and A302, finding a signal component group with the maximum modulus sum value and/or the minimum modulus sum value, deleting the equation corresponding to the signal component group with the maximum modulus sum value and/or the minimum modulus sum value, and forming an optimized overdetermined equation group by the rest equations to participate in final solution. Because the number of the unknowns is 6, after the partial equations are removed, the number of the remaining equations is required to be ensured to be greater than or equal to 6, usually the number of the equations is 6-12, and as a preferred scheme, the number of the equations is 6, 9 or 12. Comparing the signal modulus sums of all groups to obtain a signal component group with the maximum modulus sum value and/or the minimum modulus sum value, and removing an equation corresponding to the signal component group; and forming an optimized overdetermined equation set by the rest equations, 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, and the method specifically comprises the following steps:

a3001, respectively counting the sum of signal moduli acquired by the target positioning device 103 for the 102A, 102B, 102C, and 102D magnetic field generator sets, and the calculation formula is:

wherein, Vol_iIs the signal quantity generated by the i-th magnetic field generator to generate the magnetic field acting on the target, i is the number or index of each signal component, Vol^A、Vol^B、Vol^CAnd Vol^DRespectively, the modulus of three adjacent semaphores.

A3002, comparison Vol^A、Vol^B、Vol^CAnd Vol^DThe sum of the moduli with the maximum value is screened out, 3 semaphore corresponding to the sum of the moduli with the maximum value is found out, the equations corresponding to the 3 semaphore are removed from 12 equation sets, and the remaining 9 equations are combined to form an optimized over-determined equation set to participate in the final solution.

FIG. 6 is a flowchart of an iterative solution of target position and orientation, according to an embodiment of the present invention. As shown in FIG. 6, the object position and orientation solution flow 600 begins at step 601, where the demodulated signals output at step 405 of FIG. 4 are input, each corresponding to a signal component produced by the magnetic field generator acting on the object-locating device. This signal component is acquired under the optimal parameters to try to amplify the signal (step 403) when it is determined in step 402 of fig. 4 that the digital acquisition is not saturated. Next, in step 602, it is determined whether the result is not solved for a plurality of consecutive times under the current input condition. If the number of times exceeds the predetermined value (e.g., 3 times), i.e., the "yes" branch of step 602, the current round of solution is stopped in step 604, and the failure in solution is output. If the number of times exceeds the preset value, i.e. the "no" branch of step 602, the process proceeds to step 603, and it is determined whether the object corresponding to the current input is the first solution. If the first solution is performed, that is, the "yes" branch of step 603, step 605 is performed, and an initial bit value is randomly generated as an initial iteration value; if not, i.e. the "no" branch of step 603, then step 606 is entered, and the result of the previous solution is used as the initial value for the iterative solution. After the initial values are determined, the object coordinates and orientation are iteratively solved in step 607, the usual method being the LM (Levenberg-Marquardt) algorithm or a modification thereof. At step 608, it is determined whether the iteration converged. If so, yes branch of step 608, marking successful solution 609, and then outputting the solution 610; if the convergence fails, i.e., the "no" branch of step 608, the process returns to step 602 to determine whether the number of failures exceeds the predetermined number.

General case embodiments

In the embodiment of magnetic dipole equivalence, when the equation is expressed according to the Biot-Savart Law (Biot-Savart), the distance between the magnetic field generator and the target object is far larger than the size of the magnetic field generator, so that the magnetic field generator and the target object are regarded as a magnetic dipole, and the equation is deduced:

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 and rotation angle of the sensor coil, gamma is the gain coefficient, Vol_iAs a component of the magnetic induction signal, B_(x,i)Of the magnetic induction produced at the sensor coil by the i-th magnetic field generatorComponent x, B_(y,i)Is the y-component of the magnetic induction produced at the sensor coil by the i-th magnetic field generator, B_(z,i)Is the z-component of the magnetic induction produced at the sensor coil by the i-th magnetic field generator.

In this method, there is a precondition that the magnetic field generator (excitation coil) and the object positioning device (positioning sensor coil) are respectively equivalent to a magnetic dipole to directly apply biot-savart law. That is, in the above embodiments, the shape of the cross section of the excitation coil of the magnetic field generator is such that the excitation coil of the magnetic field generator and the object localization apparatus can be equivalent to a magnetic dipole, whereby the position and the direction of the object localization apparatus can be approximately calculated.

Therefore, during the production of actual products, it is often necessary to provide the excitation coil in the magnetic field generator with a circular cross section so that the excitation coil maximally approximates the structural characteristics of the magnetic dipole. That is, in such embodiments, the excitation coil of the magnetic field generator is circular in cross-section.

This condition limits the structure of the exciting coil. However, in practical applications, it is desirable to provide the cross-section of the coil in the magnetic field generator with other shapes, such as the rounded rectangle in fig. 10. The structural feature that the cross section of the exciting coil needs to be arranged in a circular shape 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 that the excitation coil is equivalent to a magnetic dipole, the cross-section of the excitation coil being circular, is broken. That is, the following embodiments are applicable not only to the case where the shape of the cross section of the excitation coil of the magnetic field generator is such that the excitation coil of the magnetic field generator can be equivalent to a magnetic dipole, but also to the case where the shape of the cross section of the excitation coil of the magnetic field generator is such that the excitation coil of the magnetic field generator cannot be equivalent to a magnetic dipole. In the latter case, more specifically, the excitation coil of the magnetic field generator has a cross-section of a shape other than a circle.

In any case, the invention provides a magnetic field target position calculation method, so that excitation coils with different cross sections can perform magnetic positioning calculation, and accurate positioning of a target object is realized.

FIG. 7 is a flow chart of a magnetic field target location calculation method according to another embodiment of the present invention. As shown in fig. 7, the magnetic field target location calculation method 700 includes the following steps:

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

s720: taking each excitation coil subblock as a current element, and calculating the magnetic induction intensity of each excitation coil subblock at any point P in space;

s730: superposing the magnetic induction intensity of each excitation coil sub-block at any point P in the space to obtain the relation between the magnetic induction intensity generated by the whole excitation coil in the space and the space position and direction (pitch angle and rotation 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 the space by the excitation coil and the spatial position and direction (pitch angle and rotation angle) obtained in step S730, the spatial position coordinate and direction (pitch angle and rotation angle) of the target positioning device (sensor coil) are obtained by solving.

In step 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 specifically means that the magnetic induction intensity of each excitation coil sub-block at any point P in space is obtained based on bioto-savart law according to the position and placement direction of each excitation coil sub-block as a current element and the current intensity of the excitation coil sub-block.

It will be understood by those skilled in the art that the magnetic induction mentioned above and in the following is meant to be a vector, i.e. the 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 Bio-Saval law is adopted to arrange the magnetic induction electromotive force equation of the P sensor coil, the shape of the section outline of the excitation coil is taken into consideration as an essential factor, and the excitation coil and the sensor coil are not directly equivalent to a magnetic dipole. In the specific method, the section profile of the excitation coil is divided into micro-segments, the magnetic induction intensity components of the micro-segments in a magnetic field are calculated respectively, then the magnetic induction intensity components are accumulated through integration, and finally the calculation formula of the magnetic induction intensity of the whole excitation coil at any point P in the space is obtained, so that the magnetic induction electromotive force equation of the P sensor coil is listed.

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

s810: dividing the excitation coil into M sections along the axial direction to obtain M sub-coil pieces, and after the sub-coil pieces are equivalent to the contours of the sub-coil pieces, segmenting the contours, wherein the step is a further extension of the step S710 in the figure 7;

s820: calculating the magnetic induction intensity component of each section of the contour at any point P in the magnetic field by adopting the Biao-Saval law, wherein the step is a further extension of the step S720 in the figure 7;

s830: superposing the magnetic induction intensity components of the sections of the profile in P to obtain the magnetic induction intensity of the profile in P; superposing the magnetic induction intensity of the M profiles in the P direction in the axial direction to obtain the magnetic induction intensity of the excitation coil in the P direction, wherein the expression of the magnetic induction intensity of the P includes the three-dimensional spatial position coordinate and the angle of the P, so as to obtain the relationship between the magnetic induction intensity of the whole excitation coil in the space and the spatial position and direction, and the step is a further extension of the step S730 in 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 at the section of the sensor coil, and the normal vector is characterized by a pitch angle and a rotation angle; the magnetic induction electromotive force equation is listed by the principle that the magnetic induction intensity of the exciting coil in P obtained in step S830 and the magnetic induction intensity of the sensor coil in the P normal vector direction obtained in this step are equal, so as to solve to obtain the position and the direction of the target positioning device (sensor coil), which is a further extension of step S740 of fig. 7.

Fig. 9 is a schematic coordinate diagram of an excitation coil using a cartesian coordinate system according to another embodiment of the invention. As shown in fig. 9, a cartesian coordinate system is adopted, the center of the excitation coil is located at the origin of coordinates, the axial vector points to the Z direction, the cross-sectional vector points to the X direction and the Y direction, the excitation coil is sliced along the Z direction, the excitation coil with the length H is equivalent to M thin coils (sub-coil slices) with the length H/M, wherein the center position Z of the excitation coil is 0, and the center position of the ith thin coil is 0

Fig. 10 is a schematic view of a field coil having a rounded rectangular cross-section according to another embodiment of the present invention. Fig. 11 is a schematic view of a field 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 a field coil according to another embodiment of the present invention, the cross section of which is another rounded rectangle.

On any thin coil (the central position is [0,0, Z ]), the construction method of the magnetic induction electromotive force equation is explained by taking a rectangle with a rounded section as an example. The thin coils are equivalent to rounded rectangles, the rounded rectangles are shown in fig. 10, straight line segments are K1, K2, K3 and K4, arc segments are S1, S2, S3 and S4, the rounded rectangles are spliced into a closed shape by S1, K1, S2, K2, S3, K3, S4 and K4 in sequence, the circular rectangles are symmetrical in figure, the arc segments are S1, S2, S3 and S4 and can be combined into a circle, namely, the arc segments S1, S2, S3 and S4 are respectively one fourth of the same circle, and the circle is divided into four equal parts. The thin coil used for calculating the magnetic induction can also be in other shapes, such as a rounded triangle in fig. 11, or another rounded rectangle in fig. 12. Fig. 10, 11 and 12 have in common 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 following describes a method for calculating the magnetic induction intensity of the excitation coil at a certain point in space and a method for solving the three-dimensional spatial position and angle of the sensor coil in the magnetic field, taking a rounded rectangle as an example.

Obviously, the rounded rectangle is composed of 4 1/4 circular arcs and 4 straight-line segments, the side length of the straight-line segment of the rounded rectangle is L, W, the radius of the circular arc of the four corners is R, (X, Y, Z) are coordinate points on the rounded rectangle, and any point is taken on the eight line segments:

any point coordinate of the circular arc S1 (circle center [ L/2, W/2, Z ], Ψ ═ 0, π/2]) is:

M1＝[L/2+R*cos(Ψ),W/2+R*sin(Ψ),Z]；

any point coordinate of straight line segment K1([ L/2, (W/2+ R), Z ] to [ -L/2, (W/2+ R), Z ]) is:

M2＝[X,(W/2+R),Z]；

any point coordinate of arc S2 (circle center [ -L/2, W/2, Z ], Ψ ═ pi/2, pi ]) is:

M3＝[-L/2+R*cos(Ψ),W/2+R*sin(Ψ),Z]；

any point in the straight line segment K2([ - (L/2+ R), W/2, Z ] to [ - (L/2+ R), -W/2, Z ]) is:

M4＝[-(L/2+R),Y,Z]；

any point coordinate of arc S3 (circle center [ -L/2, -W/2, Z ], Ψ ═ pi, 3 pi/2 ]) is:

M5＝[-L/2+R*cos(Ψ),-W/2+R*sin(Ψ),Z]；

any point coordinate of straight line segment K3([ -L/2, - (W/2+ R), Z ] to [ L/2, - (W/2+ R), Z ]) is:

M6＝[X,-(W/2+R),Z]；

any point of the circular arc S4 (circle center [ L/2, -W/2, Z ], Ψ ═ 3 π/2,2 π) is coordinate:

M7＝[L/2+R*cos(Ψ),-W/2+R*sin(Ψ),Z]；

any point in the straight line segment K4([ (L/2+ R), -W/2, Z ] to [ (L/2+ R), W/2, Z ]) is:

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 the magnetic field is as follows according to the Biot-Savart law:

the magnetic induction B generated by the multiple line segments is dB of each line segment_nAnd (4) integrating and then superposing.

Where dli is the differential of M1-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 differentiated by Ψ for M1. 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:

while

Therefore:

above | a_i|^-3It is difficult to obtain an integral analysis formula, and an approximate calculation process is required. Since (1+ x)^mThe Taylor expansion of (A) is:

taking only the first item, (1+ x)^m≈1+m·x。

In this way,

to pair

Integration was performed to obtain:

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 should be noted here that int is the integration function in matlab. For example, int (dl1 × a1 × a1^ (-3), Ψ,0, π/2) is dl1 × a1 × a1^ (-3) where Ψ is integrated over the interval [0, π/2], and b 1-b 8 is the magnetic induction intensity corresponding to each segment after the rounded rectangle is divided into eight segments. Written as a general mathematical formula:

when i is 1,2,3,4,5,6,7,8, respectively:

the magnetic induction of the rounded rectangle is the vector integral of each magnetic induction, and can be expressed by the formula: b1+ B2+ B3+ B4+ B5+ B6+ B6+ B8. A more general expression is:

wherein, B_jIs the magnetic induction of the jth profile at P, N is the number of segments into which the profile is divided, b_iIs the integral of the magnetic induction intensity component of the ith segment in the jth profile at any point P in the magnetic field over a corresponding length or angular range.

In particular, when the excitation coil is a solenoid coil, since L is 0, W is 0, Z is 0, and the cross-sectional profile of the excitation coil is circular, the expression of the magnetic induction of P in the circular profile is expressed in an XYZ coordinate system as follows:

wherein Bx, By and Bz are components of magnetic induction intensity of the profile in the X, Y, Z axial direction, N is the number of turns of the excitation coil, R is the radius of a four-corner arc, μ is magnetic permeability, and (x, y, z) is a three-dimensional coordinate of a point P.

After the magnetic induction intensity of each section profile of the excitation coil at the point P is obtained, the magnetic induction intensity of the whole excitation coil at the point P is obtained by superposing the magnetic induction intensities of the M profiles at the point P in the axial direction, and the expression of the magnetic induction intensity of the excitation coil at the point P is

Wherein B is the exciting coil in PMagnetic induction of points, B_jThe magnetic induction intensity of the jth profile at the point P is shown, and M is the number of sections of the excitation coil which is axially split.

An excitation voltage U is applied to the exciting coil

Can obtain the change rate of the exciting current

In the formula, L' is the inductance of the exciting coil. Is provided with

B '═ Bx', By ', Bz'), then

Mu is magnetic conductivity, N is the number of turns of the exciting coil, U is exciting voltage applied to the exciting coil, R is a four-corner arc radius, L ' is the inductance of the exciting coil, B ' is the magnetic induction intensity of the exciting coil after coordinate conversion of the magnetic induction intensity B of the exciting coil at a point P, and the coordinate conversion refers to the conversion of the magnetic induction intensity B of the point P, which is represented by taking the center point of the exciting coil as an origin, into the magnetic induction intensity B ' of the point P under the same coordinate system as the sensor coil. The coordinate system of the space where the sensor coil is located is not established with the center point of the excitation coil as the origin, so conversion is performed, the space coordinate of the sensor coil and the magnetic induction B of P are located in the same coordinate system, and the converted magnetic induction of P is represented as B'.

The induced electromotive force of the sensor is determined according to the law of electromagnetic induction

Where n is the number of sensor coil turns and Φ is the magnetic flux passing through the sensor coil. And phi is B · S, where B is the magnetic induction intensity of the magnetic field generated by the excitation coil at the sensor coil (P), S is the sensor coil cross-sectional area, and S is (pi · r)²) Vp ' where r is the sensor coil circumference radius and vp ' (xv ', yv ', zv ') is the sensor coil cross-sectionThe normal unit vector vp' can be characterized by a pitch angle and a rotation angle.

Is provided with

The magnetically induced electromotive force of the sensor, e, k · (B '· vp'). The coordinate (three-dimensional coordinate) and attitude (pitch angle and rotation angle) of the sensor coil can be calculated by the simultaneous equation set because B 'includes the three-dimensional spatial position coordinate of point P and vp' is represented by the pitch angle and rotation angle. Preferably, the sensor coordinates and attitude are solved using the LM algorithm.

It will be appreciated by those skilled in the art that although magnetic dipole equivalence was employed in the previous embodiment, the same is applicable to the present embodiment with respect to solving overdetermined equations, and the iteration of the LM algorithm.

Magnetic field target positioning method

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

FIG. 13 is a flow chart of a magnetic field target locating method implemented in accordance with the present invention.

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

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

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

In step S1320, a magnetic field is generated in the 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 on a 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 disposed at a different location or different orientation to produce a corresponding magnetic field. Each magnetic field generator includes an excitation coil.

In the case of alternating current driving, each magnetic field generator generates a corresponding magnetic field in accordance with the generated current of the respective frequency, thereby generating a frequency-modulated magnetic field containing the respective frequency.

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

Next, in step S1330, magnetic induction signals generated by the target positioning device in the magnetic field are collected. It will be appreciated by those skilled in the art that in a preferred embodiment of the invention, the target-locating device is located on a medical device that is medically interposed within the living being. More specifically, the object-locating means is a location sensor coil. In particular, in this step, the respective magnetic induction signal component of each magnetic field generator acting on the object positioning means is resolved according to the magnetic field generation means, for example an alternating current drive or a collimated current drive. For example, where the alternating current drive generates a quadrature modulated magnetic field signal, the decomposition here may include quadrature demodulation or Fast Fourier Transform (FFT).

Finally, in step S1340, the position and orientation of the target positioning device are calculated based on the acquired magnetic induction signals. Specifically, at this step, based on the biot-savart law, the column equation set solves the position and direction of the object locating device according to the corresponding magnetic induction signal component of each magnetic field generator acting on the object locating device. According to a preferred embodiment of the invention, the position and orientation of the object-locating device comprises the three-dimensional coordinates, the pitch angle and the rotation angle of the object-locating device.

More specifically, in order to solve the equation set by the approximation method, equations in the equation set that are not suitable for the approximation method need to be eliminated. Thus, the step of solving the target positioning device for position and orientation by the system of equations may further comprise: dividing the signal components into a plurality of groups equally, and calculating the sum of signal modulus of each group; comparing the signal modulus sums of all groups to obtain a signal component group with the maximum modulus sum value and/or the minimum modulus sum value, and removing an equation corresponding to the signal component group; and forming an optimized overdetermined equation set by the rest equations, and solving the position and the direction of the target positioning device.

In addition, the Levenberg-Marquardt (LM) algorithm or a modified version thereof may be utilized in solving the system of equations as an iterative solution to the position and orientation of the object-locating device is required.

In a preferred embodiment of the approximation solution, the shape of the cross section of the excitation coil of the magnetic field generator is such that the excitation coil of the magnetic field generator and the object localization device are equivalent to magnetic dipoles, whereby the position and orientation of the object localization device is approximated. For example, the excitation coil of the magnetic field generator is circular in cross-section, the excitation coil may be equivalent to a magnetic dipole.

Of course, the shape of the cross-section of the field coil of the magnetic field generator may be such that the field coil of the magnetic field generator cannot be equated to a magnetic dipole. For example, the excitation coil of the magnetic field generator has a cross-section of a shape other than a circle.

In order to adapt to the more general situation, namely the situation that the cross section of the excitation coil is in an arbitrary shape, the invention provides a more generally applicable method for calculating the position and the direction of the target positioning device. The method comprises the following steps: dividing the excitation coil into excitation coil sub-blocks; taking each excitation coil subblock as a current element, and calculating the magnetic induction intensity of each excitation coil subblock at any point P in space; superposing the magnetic induction intensity of each excitation coil subblock at any point P in space to obtain the relation 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 excitation coil in the space and the space position and direction.

Taking each excitation coil subblock as a current element, calculating the magnetic induction intensity of each excitation coil subblock at any point P in space, and specifically comprising the following steps: and obtaining the magnetic induction intensity of the excitation coil subblocks at any point P in the space based on the Biot-Saval law according to the position and the placing direction of each excitation coil subblock serving as a current element and the current intensity of the excitation coil subblocks.

More specifically, the excitation coil is axially divided into M sections to obtain M sub-coil pieces, and after the sub-coil pieces are equivalent to the contours of the sub-coil pieces, the contours are segmented. Then, the magnetic induction intensity component of each section of the contour at any point P in the magnetic field is calculated by adopting the Biao-Saval law. And superposing the magnetic induction intensity components of the sections of the profile in the P to obtain the magnetic induction intensity of the profile in the P. And superposing the magnetic induction intensity of the M profiles in the P direction in the axial direction to obtain the magnetic induction intensity of the excitation coil in the P direction, so that the relation between the magnetic induction intensity of the whole excitation coil in the space and the space position and direction is obtained. And listing the magnetic induction intensity of a sensor coil of the target positioning device in the direction of the P normal vector according to the law of electromagnetic induction. The normal vector refers to the normal unit vector at the cross section of the sensor coil. And listing a magnetic induction electromotive force equation according to the principle that the magnetic induction intensity of the excitation coil on the P is equal to the magnetic induction intensity of the sensor coil on the P normal vector, so that the position and the direction of the target positioning device are obtained through solving.

The magnetic field target positioning system and the magnetic field target positioning method are suitable for all fields and application scenes needing target positioning, 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

Further, one of ordinary skill in the art will recognize that the methods of the present disclosure may be implemented as computer programs. The methods of the above embodiments are performed by one or more programs, as described above in connection with the figures, including instructions to cause a computer or processor to perform the algorithms described 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 disc 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 can be provided to the computer by using various types of transitory computer-readable media. Examples of the transitory computer readable medium include an electric signal, an optical signal, and an electromagnetic wave. The transitory computer readable medium can be used to provide the program to the computer through a wired communication path such as an electric wire and an optical fiber or a wireless communication path.

For example, according to an 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 object localization method as described above, or may cause the processor to perform only the operations of calculating the position and orientation of an object localization apparatus from the acquired magnetic induction signals as described above.

Therefore, according to the present disclosure, it is also possible to propose a computer program or a computer program product which, when being executed, enables the magnetic field object localization method as described above to be implemented, or which, as described above, can only carry out the operation of calculating the position and orientation of the object localization arrangement from the acquired magnetic induction signals.

Furthermore, the invention relates to a computing device or a computing system for magnetic field object localization comprising a processor and a memory, in which a computer program is stored which, when being executed by the processor, can carry out the magnetic field object localization method as described above.

Alternatively, the invention also relates to a computing device or computing system comprising a processor and a memory, in which a computer program is stored which, when being executed by the processor, enables only the operation of calculating the position and orientation of the object-locating device from the acquired magnetic induction signals as described above.

The invention has the advantages of

In summary, in addition to the effects already described above, the advantageous 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 the 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 the placing angle of the magnetic field generator for generating the magnetic field, so that the target object (the sensor coil) is accurately positioned.

2. The magnetic field generators in each group are arranged in groups, so that the magnetic field components generated by the magnetic field generators in each group are orthogonal to each other, the magnetic field components of the magnetic field generators are in corresponding relation with the positions and the placement angles of the magnetic field generators, and the positions and the placement 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 modulated orthogonal signal, the modulated orthogonal signal is a plurality of frequency division multiplexing signals which are based on a certain basic frequency and take a certain step length as a variable, and the plurality of magnetic field generators are driven to generate the alternating magnetic field simultaneously through the frequency division multiplexing signals. 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 an overdetermined equation set is formed by simultaneously adopting a plurality of signal components, in order to improve the calculation efficiency, a method for screening out an optimized equation combination 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 calculating 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 a magnetic dipole, but the excitation coil of the magnetic field generator is divided into excitation coil subblocks, each excitation coil subblock is used as a current element, the magnetic induction intensity of any point P in space of each excitation coil subblock is calculated, then the magnetic induction intensities of any point P in space of the excitation coil subblocks are superposed, and the relationship between the magnetic induction intensity generated by the whole excitation coil in space and the space position, the pitch angle and the rotation angle is established. The method has the advantages that in the magnetic positioning system, the shape of the cross section of the excitation coil is expanded more, the excitation coil is not circular, can be in a round corner rectangle shape, can also be in a round corner triangle shape, and can also be in a combination of line segments and arcs, more possibilities are provided for manufacturing and installing the excitation coil, even if the distance between the excitation coils is very short and cannot be equivalent to a magnetic dipole, the method can still accurately calculate the signal component generated when the excitation coil acts on the sensor coil, and therefore accurate positioning of the target (the sensor coil) is achieved.

The embodiments of the invention are not limited to the above-described examples, and various changes and modifications in form and detail may be made by one skilled in the art without departing from the spirit and scope of the invention, which is considered to fall within the scope of the invention.

Claims

1. A magnetic field object locating system comprising:

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 the space according to the signal generated by the magnetic field generation control module;

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

the signal acquisition module is used for acquiring magnetic induction signals generated by 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.

2. The system of claim 1, wherein the target-locating device is located on a medical device that is medically interposed within a living being.

3. The system of claim 1, wherein the calculation is a discretized calculation of the magnetic field generating device.

4. The system of claim 1, wherein:

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

each magnetic field generator is arranged at different positions or different arrangement directions in the magnetic field generating device to generate corresponding magnetic fields,

each magnetic field generator includes an excitation coil.

5. The system of claim 1, wherein the object-locating device is a location sensor coil.

6. The system of claim 4, wherein the magnetic field generation control module is configured to generate alternating currents at a plurality of frequencies, each magnetic field generator being configured to produce a corresponding magnetic field from the currents at the respective frequencies generated by the magnetic field generation control module, thereby generating a frequency-modulated magnetic field containing the respective frequencies.

7. The system of claim 4, wherein the magnetic field generation control module is configured to generate square wave currents, each magnetic field generator being configured to receive the square wave currents in turn and generate a corresponding magnetic field in a time-sharing manner, thereby generating magnetic fields in a time sequence.

8. The system of claim 6 or 7, wherein the signal acquisition module is configured to resolve the respective magnetic induction signal component of each magnetic field generator acting on the target positioning device from the magnetic field generation.

9. The system of claim 8, wherein the location calculation module is configured to: based on the biot-savart law, the position and direction of the target positioning device are solved according to the corresponding magnetic induction signal component of each magnetic field generator acting on the target positioning device and the column equation set.

10. The system of claim 9, wherein the system of equations solving for the position and orientation of the object-locating device based on the respective magnetic induction signal components applied to the object-locating device by each magnetic field generator further comprises:

calculating a modulus value of the signal component;

obtaining a signal component with the maximum and/or minimum modulus value, and removing an equation corresponding to the signal component;

and forming an optimized overdetermined equation set by the rest equations, and solving the position and the direction of the target positioning device.

11. The system of claim 10, wherein the system of equations solving for the position and orientation of the object-locating device based on the respective magnetic induction signal components applied to the object-locating device by each magnetic field generator further comprises:

dividing the signal components into a plurality of groups equally, and calculating the sum of signal modulus of each group;

comparing the signal modulus sums of all groups to obtain a signal component group with the maximum modulus sum value and/or the minimum modulus sum value, and removing an equation corresponding to the signal component group;

12. The system of claim 9, wherein the system of equations solving for the position and orientation of the object-locating device based on the respective magnetic induction signal components applied to the object-locating device by each magnetic field generator further comprises:

iteratively solving the position and orientation of the object-locating device according to the Levenberg-Marquardt (LM) algorithm or a modified version thereof.

13. The system of claim 1, wherein the position and orientation of the target positioning device comprises three-dimensional coordinates, a pitch angle, and a rotation angle of the target positioning device.

14. The system of claim 4, wherein the plurality of magnetic field generators is at least 6 magnetic field generators.

15. The system of claim 4, wherein a cross-section of the field coil of the magnetic field generator is shaped such that the field coil of the magnetic field generator and the object localization apparatus are equivalent to a magnetic dipole, thereby approximately calculating the position and orientation of the object localization apparatus.

16. The system of claim 15, wherein the field coil of the magnetic field generator is circular in cross-section.

17. The system of claim 4, wherein the field coil of the magnetic field generator has a cross-sectional shape such that the field coil of the magnetic field generator cannot be equated to a magnetic dipole.

18. The system of claim 17, wherein a cross-section of the field coil of the magnetic field generator is a shape other than circular.

19. The system of claim 4, wherein the location calculation module is further configured to:

dividing the excitation coil into excitation coil sub-blocks;

taking each excitation coil subblock as a current element, and calculating the magnetic induction intensity of each excitation coil subblock at any point P in space;

superposing the magnetic induction intensity of each excitation coil subblock at any point P in space to obtain the relation between the magnetic induction intensity generated by the whole excitation coil in space and the space position and direction; and

and obtaining the position and the direction of the target positioning device based on the magnetic induction intensity signals at the target positioning device acquired by the magnetic field signal acquisition module and the relation between the magnetic induction intensity generated by the excitation coil in the space and the space position and direction.

20. The system of claim 19, wherein the 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 subblocks at any point P in the space based on the Biao-Saval law according to the position and the placing direction of each excitation coil subblock serving as a current element and the current intensity of the excitation coil subblocks.

21. The system of claim 19, wherein:

the dividing the excitation coil into excitation coil sub-blocks further comprises: dividing the excitation coil into M sections along the axial direction to obtain M sub-coil pieces, equivalently dividing the contour of the sub-coil pieces into sections,

the said each excitation coil subblock as the current element, calculate the magnetic induction of each excitation coil subblock at any point P in the space, further include: the magnetic induction intensity component of each section of the profile at any point P in the magnetic field is calculated by adopting the Biao-Saval law,

the magnetic induction intensity of each excitation coil subblock at any point P in the space is superposed to obtain the relationship between the magnetic induction intensity generated by the whole excitation coil in the space and the space position and direction, and the method further comprises the following steps: superposing the magnetic induction intensity components of the sections of the profile in P to obtain the magnetic induction intensity of the profile in P; the magnetic induction intensity of the M profiles in the P direction is superposed in the axial direction to obtain the magnetic induction intensity of the magnet exciting coil in the P direction, thereby obtaining the relation between the magnetic induction intensity of the whole magnet exciting coil in the space and the space position and direction,

the obtaining of 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 excitation coil in the space and the space position and the direction further includes: listing the magnetic induction intensity of a sensor coil of the target positioning device in the direction of a normal vector P 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 listing a magnetic induction electromotive force equation according to the principle that the magnetic induction intensity of the excitation coil on the P direction vector is equal to the magnetic induction intensity of the sensor coil on the P normal vector, so that the position and the direction of the target positioning device are obtained through solving.

22. A magnetic field target locating method comprising:

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

generating a magnetic field in the 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.

23. The method of claim 22, wherein the calculation is a discretized calculation of the magnetic field.

24. The method of claim 22, wherein the target-locating device is located on a medical device that is medically interposed within a living being.

25. The method of claim 22, wherein:

a plurality of magnetic field generators mounted on a fixture are employed to generate magnetic fields in space,

each magnetic field generator is arranged at a different position or in a different orientation to generate a corresponding magnetic field,

each magnetic field generator includes an excitation coil.

26. The method of claim 22, wherein the object-locating device is a location sensor coil.

27. The method of claim 25, wherein generating a signal to control the generation of the magnetic field comprises generating alternating currents at a plurality of frequencies, and wherein generating the magnetic field in the space comprises generating a corresponding magnetic field by each magnetic field generator in response to the generated currents at the respective frequencies, thereby generating a frequency modulated magnetic field comprising the respective frequencies.

28. The method of claim 25, wherein generating the signal for controlling the generation of the magnetic field comprises generating a square wave current, and wherein generating the magnetic field in the space comprises time-sharing receiving the square wave current and generating a corresponding magnetic field in turn for each magnetic field generator, thereby generating the magnetic field in a time-sequential manner.

29. The method of claim 27 or 28, wherein said acquiring magnetic induction signals generated by an object-locating device in said magnetic field comprises: and decomposing corresponding magnetic induction signal components of each magnetic field generator acting on the target positioning device according to the magnetic field generation mode.

30. The method of claim 29, wherein said calculating the position and orientation of the target positioning device comprises: based on the biot-savart law, the position and direction of the target positioning device are solved according to the corresponding magnetic induction signal component of each magnetic field generator acting on the target positioning device and the column equation set.

31. The method of claim 30, wherein the solving the position and orientation of the object-locating device from the respective magnetic induction signal components applied to the object-locating device by each magnetic field generator further comprises:

calculating a modulus value of the signal component;

32. The method of claim 31, wherein the solving the position and orientation of the object-locating device from the respective magnetic induction signal components applied to the object-locating device by each magnetic field generator further comprises:

33. The method of claim 30, wherein the solving the position and orientation of the object-locating device according to the respective magnetic induction signal component applied to the object-locating device by each magnetic field generator further comprises:

34. The method of claim 22, wherein the position and orientation of the target positioning device comprises three-dimensional coordinates, a pitch angle, and a rotation angle of the target positioning device.

35. The method of claim 25, wherein the plurality of magnetic field generators is at least 6 magnetic field generators.

36. The method of claim 25, wherein a cross-section of the field coil of the magnetic field generator is shaped such that the field coil of the magnetic field generator and the object localization apparatus are equivalent to a magnetic dipole, thereby approximately calculating the position and orientation of the object localization apparatus.

37. The method of claim 36, wherein the field coil of the magnetic field generator is circular in cross-section.

38. The method of claim 25, wherein a cross-section of the field coil of the magnetic field generator is shaped such that the field coil of the magnetic field generator cannot be equated to a magnetic dipole.

39. The method of claim 38, wherein the field coil of the magnetic field generator is shaped other than circular in cross-section.

40. The method of claim 25, wherein said calculating the position and orientation of the target positioning device comprises:

dividing the excitation coil into excitation 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 excitation coil in the space and the space position and direction.

41. The method of claim 40, wherein the step 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 further comprises:

42. The method of claim 40, wherein:

the magnetic induction intensity of each excitation coil subblock at any point P in the space is superposed to obtain the relationship between the magnetic induction intensity generated by the whole excitation coil in the space and the space position and direction, and the method further comprises the following steps: superposing the magnetic induction intensity components of the sections of the profile at P to obtain the magnetic induction intensity of the profile at P; the magnetic induction intensity of the M profiles in the P direction is superposed in the axial direction to obtain the magnetic induction intensity of the magnet exciting coil in the P direction, thereby obtaining the relation between the magnetic induction intensity of the whole magnet exciting coil in the space and the space position and direction,

the obtaining of the position and the direction of the target positioning device based on the relationship between the acquired magnetic induction signal at the target positioning device and the magnetic induction generated by the excitation coil in the space and the spatial position and the spatial direction further comprises: listing the magnetic induction intensity of a sensor coil of the target positioning device in the direction of a normal vector P 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 listing a magnetic induction electromotive force equation according to the principle that the magnetic induction intensity of the excitation coil on the P direction vector is equal to the magnetic induction intensity of the sensor coil on the P normal vector, so that the position and the direction of the target positioning device are obtained through solving.

43. A computer readable medium having stored thereon instructions executable by a processor, the instructions, when executed by the processor, cause the processor to perform the magnetic field target locating method of claim 22.