Variable target domain magnetic field compensation system and method based on multi-degree-of-freedom magnetic dipole coil array

Abstract

The invention discloses a variable target domain magnetic field compensation system and method based on a multi-degree-of-freedom magnetic dipole coil array. The variable target domain magnetic field compensation system comprises a magnetic field detection device, an array type magnetic compensation coil device, a motion capture device and a magnetic field processing control system. The magnetic field detection device is used for measuring target area magnetic field parameters; the array type magnetic compensation coil device is used for compensating a target area magnetic field; the motion capture device is used for recording position parameters of a target area of the measured object in real time; and the magnetic field processing control system is respectively connected with the magnetic field detection device and the array type magnetic compensation coil device and is used for controlling the array type magnetic compensation coil device according to the magnetic field parameters of the target area so as to dynamically compensate the magnetic field of the target area. The multi-degree-of-freedom array magnetic compensation coil layout and multi-channel independent driving are adopted, magnetic noise suppression of multiple target domains in the device is achieved, the layout is flexible, the controllability is improved, and it is ensured that high-precision magnetic measurement can still be achieved in the natural activity process of organisms.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of high-precision electromagnetic field shielding devices, relates to the field of extremely weak magnetic field measurement, and can be used for an active magnetic compensation system of various magnetic shielding devices, provides a low-noise near-zero magnetic environment for extremely weak magnetic field measurement, and particularly relates to a variable target domain magnetic field compensation system and method based on a multi-degree-of-freedom magnetic dipole coil array. BACKGROUND

[0002] With the development of quantum precision magnetic field, high-sensitivity magnetometers have been widely applied in frontier physical experiments and biomedical fields. For example, the brain magnetic function imaging is a key application of quantum extremely weak magnetic field measurement technology in the biomedical field, which can provide strong support for clinical brain disease diagnosis and treatment. However, the high-sensitivity magnetometer needs to work in a relatively low magnetic field environment, and needs to provide a near-zero magnetic field by a high-performance magnetic shielding room. The high-performance magnetic shielding room usually uses a high magnetic permeability alloy shielding layer for passive shielding, and then uses an energized coil for active reduction of internal residual magnetism. Although increasing the number of high magnetic permeability alloy layers can improve the shielding performance, the cost and weight will be significantly increased. The traditional Helmholtz coil and the conventional double-plane coil are used for compensating the magnetic field environment of a fixed space region, so that they cannot meet the demand for accurate measurement of extremely weak magnetic field of a living body under a natural behavior paradigm. SUMMARY

[0003] To solve the problems in the prior art, the application provides a variable target domain magnetic field compensation system and method based on a multi-degree-of-freedom magnetic dipole coil array, which adopts a multi-degree-of-freedom array magnetic compensation coil layout and a multi-channel independent drive to realize magnetic noise suppression of multiple target domains in the device, has flexible layout and increased controllability, and ensures that high-precision magnetic measurement can be realized in the process of natural activity of a living body.

[0004] To achieve the above object, the application provides the following scheme. A variable target domain magnetic field compensation system based on a multi-degree-of-freedom magnetic dipole coil array, comprising: a magnetic field detection device, an array type magnetic compensation coil device, a motion capture device, and a magnetic field processing control system. The magnetic field detection device is used for measuring magnetic field parameters of a target region. The array type magnetic compensation coil device is used for compensating the magnetic field of the target region. The motion capture device is used for recording position parameters of the target region of a measured object in real time. The magnetic field processing control system is connected with the magnetic field detection device and the array type magnetic compensation coil device respectively, and is used for controlling the array type magnetic compensation coil device according to the magnetic field parameters of the target region, so as to achieve dynamic compensation of the magnetic field of the target region.

[0005] Preferably, the magnetic field detection device comprises several magnetometers distributed around the target region of the measured object at predetermined spatial positions to measure the magnetic field at the target region of the measured object and transmit the signal to the host computer via signal transmission lines.

[0006] Preferably, the motion capture device determines the type, size and direction of the required compensation magnetic field of the target region of the measured object according to the eight-degree-of-freedom model of the environmental magnetic field.

[0007] Preferably, the arrayed magnetic compensation coil device comprises a pair of planar plates placed in two opposite directions around the measured object and coils arranged thereon, the two planar plates are placed opposite and parallel to each other, the pair of parallel planar plates are the reference for the coil distribution, slots are opened on the surface of the planar plates according to design needs to fix the position and shape of the coils on the plates, the coil distribution on the two plates includes symmetric and asymmetric forms, the coils arranged on the planar plates include a combination of multi-layer arrayed magnetic compensation coils in splicing or nesting form, each sub-unit coil includes a rectangle or a circle, which is driven by a driving connection line, and the internal current is adjusted according to the target to generate the required compensation magnetic field of the system.

[0008] Preferably, the magnetic field processing control system comprises a multi-channel data acquisition board card, a multi-channel low-noise coil driver, a host computer and a power supply device. The multi-channel data acquisition board card is used to convert the collected magnetic field parameters into digital signals and transmit them to the host computer via data transmission lines. The multi-channel low-noise coil driver is controlled by the host computer and is used to drive the power supply device to generate a current of a specific size and direction for driving the arrayed magnetic compensation coil device. The host computer is used to construct a magnetic eight-degree-of-freedom field model according to the collected signals, and to determine the compensation magnetic field parameters according to the position parameters of the target region to be measured, so as to adjust the parameters of the multi-channel low-noise coil driver. The power supply device provides a stable current source for the multi-channel data acquisition board card and the multi-channel low-noise coil driver.

[0009] The application also provides a variable target region magnetic field compensation method based on a multi-degree-of-freedom magnetic dipole coil array, which is realized by the system described above, and the method comprises the following steps: Step 1: After the measured object enters the magnetic shielding cabin, the magnetic field detection device is installed at the detection part of the measured object to collect the magnetic field parameters of the target, and the magnetic field parameters are transmitted to the host computer via the multi-channel data acquisition board card, that is, the target is collected, and a predetermined number of magnetic sensors are arranged in the space to scan the magnetic field parameters of each part of the space and collect the static components of the environmental magnetic field in the whole space, and the magnetic field parameters are transmitted to the host computer via the multi-channel data acquisition board card. Step 2: According to the static component of the detected environmental magnetic field parameters, the environmental magnetic field in the whole space is equivalent to an eight-degree-of-freedom magnetic field model, and the type, size and direction of the required compensation magnetic field of the target region of the measured object are determined. Step 3: The motion capture device records the position parameters of the movable measured object to be detected in real time, and transmits the parameters to the upper computer in real time. Step 4: According to the magnetic field model, the static solution of the current distribution of the dipole coil array is sought, and according to the position parameters of the movable measured object to be detected recorded by the capture device 7 in real time, the dynamic solution of the current distribution of the dipole coil array in the compensation of the current target region position is further solved. Step 5: According to the calculated dynamic solution of the current distribution of the dipole coil array, the upper computer adjusts the output parameters to control the multi-channel low-noise coil driver to drive the array magnetic compensation coil device to complete the compensation. Step 6: According to the actual test situation, it is decided whether to continue the variable target domain compensation. If the test is not completed or the position of the target region to be detected is further changed, the current distribution ratio of each dipole coil unit in the array magnetic compensation coil device is corrected, the output parameters of the upper computer are adjusted, and steps 3-6 are repeated. If the test is completed, the magnetic field compensation is ended.

[0010] Preferably, the eight-degree-of-freedom magnetic field model simplifies the magnetic field in the environment into three orthogonal directions x-axis, y-axis and z-axis uniform magnetic field and 、 、 、 and five direction gradient magnetic field, that is , 、 and represent the environmental magnetic field, the uniform magnetic field and the gradient magnetic field, , 、 and represent the uniform magnetic field of the three orthogonal directions x-axis, y-axis and z-axis, , 、 、 、 and represent 、 、 、 and five direction gradient magnetic field, which describes the distribution relationship of the magnetic field in detail. Since the space magnetic field in the magnetic shielding room can be kept stable for a long time, the eight-degree-of-freedom magnetic field model can be used for subsequent variable target domain magnetic field compensation.

[0011] Preferably, the method of seeking the static solution of the current distribution of the dipole coil array based on the magnetic field model, and then further calculating the dynamic solution of the current distribution of the dipole coil array in compensating for the current position of the target area based on the position parameters of the movable test object to be detected recorded in real time by the capturing device, includes: Set as shared k There are 10 dipole coil array groups, and each dipole coil array group has 1000 dipole coil array groups. j Each sub-unit coil has [number] sub-unit coils. i Section of conductor, i The magnetic fields of the conductor segment at point P are superimposed to obtain the magnetic field of each sub-unit coil at point P. P magnetic field at the location Each dipole coil array group at the field point P magnetic field at the location All dipole coil array groups at the field point P magnetic field at the location ,in This refers to the magnetic field at point P for each segment of wire within a single sub-unit coil. This refers to the magnetic field at point P of each sub-unit coil within a single dipole coil array. For a single dipole coil array group at the field point P The magnetic field at that location is decomposed into uniform magnetic fields in three directions, according to the Biot-Savart law. ,in The magnetic field strength at a point in space. The permeability of free space, The initial value of the current intensity in the current-carrying conductor. It is a current element vector. For the current element The position vector pointing to the point where the magnetic field to be determined. Position vector The magnitude of the uniform magnetic field at point P is expressed as: ,in I The current intensity within the current-carrying conductor. , and They are respectively x axis, y shaft and z A uniform magnetic field along the axial direction; similarly, the gradient fields in the five directions are expressed as follows: ,in , , , and They represent , , , and Gradient magnetic field in the direction of A x , A y and A z respectively represent the magnetic field superposition of the matrix composed of the function of the three directions of the dipole coil array group and the single field point position and the coil parameters, M xx , M xy , M xz , M yy and M yz represent the superposition of the magnetic field gradient generated by each coil in the coil array at a single target point, and the current in the coil is solved according to the magnetic field distribution, that is, the equation group is solved: ; wherein, , and are the values of the uniform magnetic field in the three directions of each discrete point in the target field area to be compensated, x , y , z , , , , are the gradient values of each discrete point in the five directions in the target field area to be compensated, and eight parameters are obtained according to the magnetic field data collected by the magnetic detection device in the target area. The equation group is an over-determined equation, and the Tikhonov regularization method is used to seek the current distribution static solution of the dipole coil array at the current position. The position of the magnetic detection device of the target magnetic field recorded by the motion capture device is calculated according to the parameters to ensure that the movable magnetic detection device is in the linear working interval, so as to combine with the obtained current distribution static solution to calculate the real-time current distribution dynamic solution.

[0012] Compared with the prior art, the beneficial effects of the present application are: (1) Compared with the traditional fixed coil configuration of the active magnetic compensation method, the present application adopts high-density array coil layout and multi-channel independent driving, which can meet the high-degree magnetic field regulation and control, and generate single-direction magnetic field, gradient field magnetic field and higher-order magnetic field.

[0013] (2) The present application can realize dynamic magnetic field compensation according to the motion trajectory of the measured object, meet the suppression of motion artifacts generated by the measured object when moving, and provide a stable magnetic field environment for realizing wearable brain magnetic measurement. BRIEF DESCRIPTION OF DRAWINGS

[0014] ​In order to more clearly illustrate the technical solutions of the present application, the following briefly introduces the drawings needed in the embodiments. Obviously, the drawings described below only show some of the embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0015] Figure 1 It is a schematic diagram of the magnetic field compensation system of the multi-degree-of-freedom array magnetic compensation coil of the embodiment of the present application, and the coil combination is spliced; Figure 2 It is a schematic diagram of the multi-layer array coil combination of the embodiment of the present application in a stacked and nested manner; Figure 3 It is a flow chart of a variable target domain magnetic field compensation method based on a multi-degree-of-freedom magnetic dipole coil array of the embodiment of the present application; In the figure, 1 is a measured object; 2 is a signal transmission line; 3 is a multi-channel data acquisition board card; 4 is a multi-channel low-noise coil driver; 5 is a data transmission line; 6 is a power supply device; 7 is a motion capture device; 8 is an array magnetic compensation coil device; 9 is a driving connection line; 10 is an upper computer; 11 is a magnetic field processing control system; 12 is a dipole coil array group; 13 is a sub-unit coil; and 14 is a wire. DETAILED DESCRIPTION

[0016] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0017] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0018] Embodiment one The biological magnetic signal is extremely weak, for example, the amplitude of the brain magnetic signal is only in the order of hundred fT, the frequency is mainly in the low frequency band of 0.5Hz to 100Hz, and it is extremely easy to be disturbed by the environmental background magnetic field, resulting in the reduction of the signal quality of the brain magnetic functional imaging, and it is difficult to meet the related scientific research and disease diagnosis and treatment. The biological individual has natural behaviors such as respiratory fluctuation during the measurement process, and the spatial positions of various organs in the body will also change in real time. The traditional magnetic compensation system is limited to the magnetic compensation mode of the fixed area, resulting in a significant decline in the magnetic noise suppression ability under the natural behavior paradigm, and it is unable to meet the effective capture of the extremely weak magnetic signal of the biological body. In order to further improve the performance of the biomedical magnetic measurement, the present application proposes a variable target domain magnetic field compensation system based on a multi-degree-of-freedom magnetic dipole coil array, adopts a multi-degree-of-freedom array magnetic compensation coil layout and a multi-channel independent driving, realizes the magnetic noise suppression of multiple target domains in the device, the layout is flexible, the controllability is increased, and the high-precision magnetic measurement can still be realized in the process of the natural activity of the biological body, meets the needs of the extremely weak magnetic imaging of the biological body for multiple target regions and low-noise magnetic environment, and provides an effective measurement means for studying the physiological activity law of the biological body and analyzing multiple organ joint diseases. It comprises: a magnetic field detection device, an array type magnetic compensation coil device 8, a motion capture device 7 and a magnetic field processing control system 11.

[0019] The magnetic field detection device is used for measuring the magnetic field parameters of the target region. The array type magnetic compensation coil device 8 is used for compensating the magnetic field of the target region. The motion capture device 7 is used for recording the position parameters of the target region of the measured object 1 in real time. The magnetic field processing control system 11 is connected with the magnetic field detection device and the array type magnetic compensation coil device 8 respectively, and is used for controlling the sub-unit coil 13 device according to the magnetic field parameters of the target region, so as to dynamically compensate the magnetic field of the target region.

[0020] In one embodiment, the magnetic field detection device comprises a plurality of magnetometers, which are distributed around the target region of the measured object 1 at certain spatial positions, accurately measure the magnetic field at the target region of the measured object 1 in the magnetic shielding space, and transmit the magnetic field to the upper computer 10 through the signal transmission line 2, and an eight-degree-of-freedom magnetic field model is constructed. 、 、 、 and five direction gradient magnetic fields, that is , 、 and respectively represent the environmental magnetic field, the uniform magnetic field and the gradient magnetic field, , , and a uniform magnetic field in three orthogonal directions x, y and z, wherein , , , and represent , , , and a gradient magnetic field in five directions, the model describes in detail the distribution relationship of the magnetic field, since the space magnetic field in the magnetic shielding room can be kept stable for a long time, therefore the eight-degree-of-freedom magnetic field model can be used for subsequent variable target domain magnetic field compensation.

[0021] In one embodiment, the motion capture device 7 provides the position parameters of the target region of the measured object 1, which can be combined with the eight-degree-of-freedom magnetic field model of the target region, to determine the type, size and direction of the required compensation magnetic field of the target region of the measured object 1.

[0022] In one embodiment, the array type magnetic compensation coil device includes a pair of planar plates placed in two opposite directions around the measured object 1 and coils arranged thereon, the two planar plates are placed opposite and parallel to each other, the pair of parallel planar plates are the reference for the coil distribution, according to the design needs, slots can be opened on the surface of the planar plate for fixing the position and shape of the coil on the plate, the coil distribution on the two planar plates includes symmetric form and asymmetric form, the coil arranged on the planar plate includes but is not limited to spliced or nested multi-layer array coil combination, each sub-unit coil 13 includes but is not limited to rectangular or circular, which can be driven individually by the driving connection line 9, and the internal current can be adjusted according to the target, so as to generate the required compensation magnetic field of the system.

[0023] In one embodiment, the magnetic field processing control system 11 includes a multi-channel data acquisition board card 3, a multi-channel low-noise coil driver 4, a host computer 10 and a power supply device 6, the multi-channel data acquisition board card 3 is used to convert the collected magnetic field parameters into digital signals and transmit them to the host computer 10 through the data transmission line 5, the multi-channel low-noise coil driver 4 is controlled by the host computer 10, and the power supply device 6 generates a current of a specific size and direction for driving the array type magnetic compensation coil device 8, the host computer 10 is used to construct a magnetic eight-degree-of-freedom field model according to the collected signals, and then determine the magnetic field parameters to be compensated according to the position parameters of the target region to be measured, so as to adjust the parameters of the multi-channel low-noise coil driver 4, and the power supply device 6 provides a stable current source for the above-mentioned multi-channel data acquisition board card 3 and multi-channel low-noise coil driver 4.

[0024] The specific implementation process is described in detail in the following Figure 1The application provides a variable target domain magnetic field compensation system based on a multi-degree-of-freedom magnetic dipole coil array, which comprises a signal transmission line 2, a motion capture device 7, an array type magnetic compensation coil device 8 and a magnetic field processing control system 11, wherein the magnetic field processing control system 11 comprises a multi-channel data acquisition board card 3, a multi-channel low-noise coil driver 4, a power supply device 6 and an upper computer 10, the magnetic field processing control system 11 is connected with the magnetic field detection device through the signal transmission line 2 and the multi-channel data acquisition board card 3, and the magnetic field processing control system 11 outputs a driving current to the array type magnetic compensation coil device 8 through a driving connection line 9.

[0025] In the use process of MEG, the magnetic field detection device needs to be installed in cooperation with the head size of the measured object 1, a certain number of high-precision magnetometers are installed around the brain of the measured object 1, so that the magnetic field at different positions of the brain of the measured object 1 is accurately measured, and the signal is transmitted to the magnetic field processing control system 11 through the signal transmission line 2.

[0026] Reference Figure 1 Two array type magnetic compensation coil devices 8 are installed around the measured object 1, which are placed in parallel and symmetrically, the array type magnetic compensation coil device 8 is composed of a planar plate and coils arranged thereon, slots are opened on the surface of the planar plate to facilitate the fixation of the position and shape of the coils on the plate, and the distribution of the coils on the two plates includes symmetric and asymmetric forms.

[0027] Reference Figure 1 And Figure 2 In the design and arrangement of the coils arranged on the planar plate, a multi-layer array type coil combination in a splicing or nesting mode is included but not limited to, each sub-unit coil 13 includes but is not limited to a rectangular or circular shape, can be driven individually by the driving connection line 9, and the internal current can be adjusted according to the target, so as to generate a compensation magnetic field required by the system.

[0028] Reference Figure 1 In the magnetic field processing control system 11, the magnetic field parameters of the target region can be converted into digital signals through the multi-channel data acquisition board card 3, and transmitted to the upper computer 10 through the data transmission line 5, so as to facilitate the upper computer 10 to build a magnetic field model, the upper computer 10 determines the to-be-compensated magnetic field parameters in the process of building the magnetic field model, and controls the multi-channel low-noise coil driver 4, so that the power supply device 6 generates a dynamic current with a specific size and direction for the array type magnetic compensation coil device 8.

[0029] Embodiment two Reference Figure 1 And Figure 3 The application further provides a variable target domain magnetic field compensation method based on a multi-degree-of-freedom magnetic dipole coil array, and the operation process comprises the following steps: Step 1: After the measured object 1 enters the magnetic shielding room, the magnetic field detection device is installed at the detection site of the measured object 1 to collect the magnetic field parameters of the target. The magnetic field parameters are transmitted to the upper computer 10 through the multi-channel data acquisition board card 3, that is, the target is collected. A predetermined number of magnetic sensors are arranged in the space to scan the magnetic field parameters of each part of the space, collect the static components of the environmental magnetic field in the entire space, and transmit the magnetic field parameters to the upper computer 10 through the multi-channel data acquisition board card 3. Step 2: According to the static components of the detected environmental magnetic field parameters, the environmental magnetic field in the entire space is reduced and equivalent to an eight-degree-of-freedom magnetic field model, and the magnetic field in the environment in each direction is simplified to three orthogonal directions x-axis, y-axis and z-axis uniform magnetic field and 、 、 、 and five direction gradient magnetic field, that is , 、 and represent the environmental magnetic field, the uniform magnetic field and the gradient magnetic field, , 、 and represent the uniform magnetic field of three orthogonal directions x-axis, y-axis and z-axis, , 、 、 、 and represent 、 、 、 and five direction gradient magnetic field, which describes the distribution relationship of the magnetic field in detail. Since the space magnetic field in the magnetic shielding room can be kept stable for a long time, the eight-degree-of-freedom magnetic field model can be used for subsequent variable target domain magnetic field compensation. Step 3: The motion capture device 7 records the position parameters of the movable measured object 1 in real time, and transmits the parameters to the upper computer 10 in real time. Step 4: There are k dipole coil array groups 12, each dipole coil array group 12 has j subunit coils 13, each subunit coil 13 has i segments of wire 14, and the magnetic field of i segments of wire 14 at the field point P is superimposed to obtain the magnetic field P of each subunit coil 13 at the field point , and each dipole coil array group 12 has the magnetic field PThe magnetic field at the field point P The magnetic field at the field point P P The magnetic field at the field point P , which can be decomposed into three uniform magnetic fields in three directions, where is the magnetic field at the field point P by each segment of wire 14 in a single subunit coil 13, is the magnetic field at the field point P by each subunit coil 13 in a single dipole coil array group 12, P is the magnetic field at the field point P by the single dipole coil array group 12, according to the Biot-Savart law where P is the magnetic induction at a point in space, is the vacuum permeability, is the initial value of the current intensity in the current-carrying conductor, is the current element vector, is the position vector from the current element to the position of the field point to be solved, is the magnitude of the position vector , and the uniform magnetic field at the field point P can be expressed as where is the current intensity in the current-carrying conductor, P , and I are the uniform magnetic fields in the , and directions, respectively, and similarly the gradient fields in five directions can be expressed as x where y , z , , and represent the gradient magnetic fields in the , , , and directions, respectively, A , A x , A y and A z represent the magnetic field superposition of the matrix composed of the functions of the three directions of the dipole coil array group 12, the position of the single field point, and the coil parameters, M xx , M xy , M xz , M yy and M yzThis represents the superposition of the magnetic field gradients generated by each coil in the coil array at a single target point. Solving for the current in the coil based on the magnetic field distribution is equivalent to solving the system of equations: ; in , and For each discrete point in the target field area to be compensated x , y , z The values ​​of uniform magnetic fields in three directions , , , and The gradient values ​​in five directions for each discrete point within the target field region to be compensated are given. The above eight parameters can be obtained from the magnetic field data obtained by the magnetic sensor scanning in space. This set of equations is an overdetermined set of equations, and the static solution of the current distribution of the dipole coil array can be found using the Tikhonov regularization method. Then, based on the position parameters of the target area of ​​the movable test object 1 to be detected, which are recorded in real time by the capturing device 7, the magnetic field to be compensated in the target area is updated, i.e., the new magnetic field. , , , , , , and The dynamic solution of current distribution of the dipole coil array at the current target region position is recalculated. Step 5: Based on the calculated dynamic solution of the current distribution of the dipole coil array, the host computer 10 adjusts the output parameters and controls the multi-channel low-noise coil driver 4 to distribute the current of each dipole coil unit in the array magnetic compensation coil device 8. The array magnetic compensation coil device 8 generates the required magnetic field and completes the compensation. Step 6: Determine whether to continue variable target domain compensation based on the actual test results. If the test is not completed or the location of the target area to be tested changes further, recalculate the dynamic solution of the current distribution of the dipole coil array, correct the output parameters of the host computer 10, adjust the current distribution ratio of each dipole coil unit in the array magnetic compensation coil device 8 by the multi-channel low-noise coil driver 4, thereby generating a new compensation magnetic field. Repeat steps 3-6. If the test has been completed, end the magnetic field compensation.

[0030] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A variable target domain magnetic field compensation system based on a multi-degree of freedom magnetic dipole coil array, characterized by, The system comprises a magnetic field detection device, an array magnetic compensation coil device, a motion capture device and a magnetic field processing control system; The magnetic field detection device is used for measuring the magnetic field parameters of the target region; The array magnetic compensation coil device is used for compensating the magnetic field of the target region; The motion capture device is used for recording the position parameters of the target region of the measured object in real time; The magnetic field processing control system is connected with the magnetic field detection device and the array magnetic compensation coil device respectively, and is used for controlling the array magnetic compensation coil device according to the magnetic field parameters of the target region, so as to dynamically compensate the magnetic field of the target region.

2. The system of claim 1, wherein, The magnetic field detection device comprises a plurality of magnetometers, which are distributed around the target region of the measured object at predetermined spatial positions, measure the magnetic field at the target region of the measured object, and transmit the magnetic field parameters to the upper computer through signal transmission lines.

3. The system of claim 1, wherein, The motion capture device determines the type, size and direction of the required compensation magnetic field of the target region of the measured object according to the eight-degree-of-freedom model of the environmental magnetic field.

4. The system of claim 1, wherein, The array magnetic compensation coil device comprises a pair of planar plates placed in two opposite directions around the measured object and coils arranged thereon, the two planar plates are placed opposite and parallel to each other, the pair of parallel planar plates are the reference for the coil distribution, according to the design needs, slots are opened on the surface of the planar plate for fixing the position and shape of the coil on the plate, the coil distribution on the two plates includes symmetric and asymmetric forms, the coils arranged on the planar plate include spliced or nested multi-layer array coil combinations, each sub-unit coil includes a rectangle or a circle, which is driven by a driving connection line, and the internal current is adjusted according to the target, thereby generating the required compensation magnetic field of the system.

5. The system of claim 1, wherein, The magnetic field processing control system comprises a multi-channel data acquisition board card, a multi-channel low-noise coil driver, an upper computer and a power supply device; The multi-channel data acquisition board card is used for converting the collected magnetic field parameters into digital signals and transmitting them to the upper computer through data transmission lines; The multi-channel low-noise coil driver is controlled by the upper computer and is used for driving the power supply device to generate a current of a specific size and direction for driving the array magnetic compensation coil device; The upper computer is used for constructing a magnetic eight-degree-of-freedom field model according to the collected signals, determining the magnetic field parameters to be compensated according to the position parameters of the target region to be measured, and adjusting the parameters of the multi-channel low-noise coil driver; The power supply device provides stable current sources for the multi-channel data acquisition board card and the multi-channel low-noise coil driver.

6. A method for compensating a variable target domain magnetic field based on a multi-degree-of-freedom magnetic dipole coil array, the method being implemented by the system of any one of claims 1-5, characterized in that, The method comprises: Step 1: After the measured object enters the magnetic shielding cabin, the magnetic field detection device is installed on the part of the measured object to be detected to collect the magnetic field parameters of the target, and the magnetic field parameters are transmitted to the upper computer through the multi-channel data acquisition board card, that is, the target is collected, and a predetermined number of magnetic sensors are arranged in the space to scan the magnetic field parameters of each part of the space, collect the static components of the environmental magnetic field in the whole space, and transmit the magnetic field parameters to the upper computer through the multi-channel data acquisition board card; Step 2: According to the static components of the detected environmental magnetic field parameters, the environmental magnetic field in the whole space is equivalent to an eight-degree-of-freedom magnetic field model, and the type, size and direction of the required compensation magnetic field of the target region of the measured object are determined; Step 3: The action capture device records the position parameter of the movable measured object in real time, and transmits the parameter to the host computer in real time; Step 4: According to the magnetic field model, the static solution of the current distribution of the dipole coil array is sought, and according to the position parameter of the movable measured object recorded by the capture device in real time, the dynamic solution of the current distribution of the dipole coil array in the compensation of the current target region position is further solved; Step 5: According to the dynamic solution of the current distribution of the dipole coil array calculated, the host computer adjusts the output parameter to control the multi-channel low-noise coil driver to drive the array magnetic compensation coil device to complete the compensation; Step 6: According to the actual test situation, it is decided whether to continue the variable target domain compensation, if the test is not completed or the position of the target region to be detected is further changed, the current distribution proportion of each dipole coil unit in the array magnetic compensation coil device is corrected, the output parameter of the host computer is adjusted, and steps 3-6 are repeated, if the test is completed, the magnetic field compensation is ended.

7. The method of claim 6, wherein, The eight-degree-of-freedom magnetic field model simplifies the magnetic field in each direction distributed in the environment into three orthogonal directions x-axis, y-axis and z-axis uniform magnetic field and 、 、 、 and five direction gradient magnetic field, that is , 、 and respectively represent the environment magnetic field, uniform magnetic field and gradient magnetic field, , 、 and represent the uniform magnetic field of three orthogonal directions x-axis, y-axis and z-axis, , 、 、 、 and represent 、 、 、 and five direction gradient magnetic field, the model describes the distribution relationship of the magnetic field in detail, because the space magnetic field in the magnetic shielding room can be kept stable for a long time, so the eight-degree-of-freedom magnetic field model can be used for subsequent variable target domain magnetic field compensation.

8. The method of claim 6, wherein, The method for seeking the static solution of the current distribution of the dipole coil array according to the magnetic field model, and further solving the dynamic solution of the current distribution of the dipole coil array in the compensation of the current target region position according to the position parameter of the movable measured object recorded by the capture device in real time comprises: Setting common k Each dipole coil array group has j Sub-unit coils, each sub-unit coil has i Segments of wire, the i Segments of wire are superimposed at the field point P to obtain the magnetic field of each sub-unit coil at the field point P The magnetic field of each dipole coil array group at the field point P The magnetic field of all dipole coil array groups at the field point P Where Is the magnetic field of each segment of wire in a single sub-unit coil at the field point P, Is the magnetic field of each sub-unit coil in a single dipole coil array group at the field point P, Is the magnetic field of a single dipole coil array group at the field point P And is decomposed into three direction uniform magnetic fields, according to the Biot-Savart law Where Is the magnetic induction intensity at a point in space, Is the vacuum permeability, Is the initial value of the current intensity in the current-carrying conductor, Is the current element vector, Is the position vector from the current element To the point where the magnetic field is to be solved, Is the magnitude of the position vector The uniform magnetic field at the field point P is represented as Where I Is the current intensity in the current-carrying conductor, , And Are the uniform magnetic fields in the x Axis, y Axis and z Axis direction, and similarly the gradient field in five directions is represented as Where , , , And Represent the gradient magnetic fields in the , , , And Directions, A x , A y And A z Respectively represent the magnetic field superposition of the matrix composed of three directions of the dipole coil array group and the functions related to the position of the single field point and the coil parameters,​​​ M xx , M xy , M xz , M yy and M yz represents the superposition of the magnetic field gradients generated by each coil in the array at a single target point, the currents in the coils are solved from the magnetic field distribution, i.e. from the system of equations: ； in, , and For each discrete point in the target field area to be compensated x , y , z The values ​​of the uniform magnetic field in three directions. , , , , The gradient values ​​of each discrete point in the target field area to be compensated in five directions are given by eight parameters obtained from the magnetic field data collected by the magnetic detection device in the target area. This set of equations is an overdetermined set of equations. The Tikhonov regularization method is used to find the static solution of the current distribution of the dipole coil array at the current position. The motion capture device records the position of the magnetic detection device of the target magnetic field in real time and calculates the compensation magnetic field to ensure that the movable magnetic detection device is in the linear working range based on the parameters. Then, it is combined with the obtained static solution of current distribution to calculate the dynamic solution of real-time current distribution.

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