Active anti-magnetic interference electroencephalogram acquisition system and method

Abstract

The invention belongs to the technical field of magnetic field processing, and relates to an active anti-magnetic interference electroencephalogram acquisition system and method. The electroencephalogram collecting system comprises an electroencephalogram collecting electrode, an electroencephalogram amplifier, an anti-magnetic-interference assembly and a controller, the anti-magnetic-interference assembly comprises a magnetic shielding barrel, a coil assembly defining a shielding area is arranged in the magnetic shielding barrel, and a magnetic sensor is located in an effective area arranged in the shielding area; the magnetic sensor driver and the coil driver are arranged outside the magnetic shielding barrel; the electroencephalogram amplifier is arranged in the effective area; the magnetic sensor driver controls the magnetic sensor to collect a magnetic interference signal and send the signal to the controller; and the controller performs vector decomposition on the magnetic interference signal to obtain the magnetic field size of the coil assembly in each direction, generates a control instruction based on the magnetic field size in each direction and sends the control instruction to the coil driver so as to control the current size of the coil assembly, so that the coil assembly generates an offset magnetic field opposite to the magnetic field size in the corresponding direction in each direction. The invention also provides an active anti-magnetic interference electroencephalogram acquisition method.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic field processing, and in particular, to an electroencephalogram acquisition system and method with active diamagnetic interference resistance. Background Technique

[0002] Electroencephalogram (EEG) signals can reflect the electrophysiological activities of brain nerve cells and can interpret the instructions and intentions inside the brain. High-precision EEG signals have broad application prospects and significant practical value. However, the anti-interference ability of EEG signals is weak. Therefore, the degaussing process for EEG signal acquisition is particularly important.

[0003] A commonly used method in the prior art is to acquire EEG signals in an electromagnetic shielding room. Since there are a large number of electromagnetic interference sources in the ordinary environment, such as electromagnetic waves emitted by nearby electronic devices, power frequency interference in the power grid, etc. The electromagnetic shielding room can effectively block these external electromagnetic signals and provide a low-noise electromagnetic environment for EEG acquisition. However, this method has certain defects. One is that due to the large amount of building materials and more wiring required for the electromagnetic shielding room, the volume of the electromagnetic shielding room is large, sufficient space is needed, and the construction cost is high. The other is that the requirement for grounding is high. Good grounding is a crucial link for EEG acquisition in the electromagnetic shielding room. The EEG acquisition device needs to be connected to the grounding system of the shielding room through a special grounding wire. This can effectively conduct the static electricity and electromagnetic interference on the device to the ground and further improve the quality of signal acquisition. If the grounding is poor, it may cause phenomena such as baseline drift in the acquired EEG signals, affecting the analysis and interpretation of EEG signals.

[0004] When collecting electroencephalogram (EEG) signals, 50Hz or 60Hz electromagnetic waves are the main interference. Therefore, removing the interference in this frequency band has become a necessary noise reduction means. Among them, the notch filter is a mainstream means of removing power frequency interference. The notch filter is a special filter, and its main function is to suppress or attenuate signals of a specific frequency, with less impact on signals of other frequencies. For removing power frequency interference, it can set a "notch" in the frequency domain to significantly reduce the signal intensity of the power frequency interference frequency components. However, this method also has certain defects. The first is phase distortion. The notch filter usually causes phase changes during the filtering process. When the signal passes through the notch filter, the phase shift situations of different frequency components are different. The second is that the performance of removing power frequency interference is greatly affected by software and hardware. In terms of hardware: the performance of the hardware notch filter depends on the accuracy and stability of the electronic components (such as resistors, capacitors, and inductors) used. The actual electronic components have a certain tolerance range, which may cause deviations between the notch frequency and bandwidth and the design values. In terms of software: the software notch filter is limited by the calculation accuracy during digital signal processing. Since digital signals are discrete and represented with a limited word length in a computer, quantization errors will occur. Moreover, if the calculation or representation accuracy of the filter coefficients is insufficient, it may affect the filtering effect. The third is that new interference or noise may be introduced. In the hardware notch filter, the circuit components themselves may generate thermal noise or electromagnetic interference. For example, a resistor will generate thermal noise when passing current, and this noise will be superimposed on the signal, affecting the quality of the filtered signal. In the software notch filter, if the algorithm is not implemented properly, such as overflow or rounding errors during digital operations, quantization errors similar to noise may be generated, interfering with the normal processing of the signal.

[0005] In view of the above deficiencies, there is an urgent need to propose an EEG acquisition scheme with outstanding anti-interference performance. Summary of the Invention

[0006] The purpose of the present invention is to provide an EEG acquisition system with active anti-magnetic interference, which can actively resist magnetic interference and has the advantages of strong dynamic adaptability, low cost, easy to carry, good shielding effect, and being applicable to complex magnetic field environments.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] In the first aspect, the present invention provides an EEG acquisition system with active anti-magnetic interference, including: EEG acquisition electrodes, an EEG amplifier, an anti-magnetic interference component, and a controller;

[0009] Among them, the anti-magnetic interference component includes a magnetic shielding barrel, a coil group arranged in the magnetic shielding barrel and capable of enclosing a shielding area, an effective area arranged in the shielding area; a magnetic sensor placed in the effective area, a magnetic sensor driver and a coil driver placed outside the magnetic shielding barrel;

[0010] The EEG amplifier is placed within the effective area;

[0011] The magnetic sensor drive controls the magnetic sensor to collect magnetic interference signals and sends them to the controller; the controller performs vector decomposition on the magnetic interference signals to obtain the magnetic field magnitudes in each direction of the coil group. The controller generates control instructions based on the magnetic field magnitudes in each direction and sends the control instructions to the coil drive to control the current magnitudes of the coil group, so that the coil group generates a cancellation magnetic field in each direction that is opposite to the magnetic field magnitude in the corresponding direction.

[0012] As a possible implementation, the magnetic field within the effective area decays by 3 dB.

[0013] As a possible implementation, the coil group is a three-dimensional Helmholtz coil, that is, it is composed of three pairs of orthogonal Helmholtz coils.

[0014] As a possible implementation, after the controller obtains the magnetic interference signals, it performs vector decomposition to obtain the magnetic field magnitudes at the center of each pair of Helmholtz coils. The control instructions are generated based on the magnetic field magnitudes at the center to make the current flowing through each pair of Helmholtz coils satisfy the following relationship with the magnetic field magnitude at the center:

[0015]

[0016] where B is the magnetic field magnitude at the center, in Tesla; μ0 is the magnetic permeability of vacuum, μ0 = 4Π×10 -7 T·m / A; n is the number of turns of each pair of Helmholtz coils; I is the current flowing through each pair of Helmholtz coils, in Ampere; R is the radius of the coil, in meters.

[0017] As a possible implementation, the magnetic shielding barrel is a hollow cylindrical structure, and three pairs of orthogonal Helmholtz coils are distributed in the front-back, up-down, and left-right directions inside the barrel; among them, the two pairs of Helmholtz coils in the up-down and left-right directions are saddle-shaped coils, and the pair of Helmholtz coils in the front-back direction is a cylindrical coil.

[0018] As a possible implementation, the magnetic shielding barrel is a hollow cylindrical structure or a hollow hexahedral structure, and all three pairs of orthogonal Helmholtz coils are square Helmholtz coils.

[0019] As a possible implementation, the effective area and the shielding area are concentric, and the area of the effective area is denoted as S1, the area of the shielding area is denoted as S2, and the area occupied by the amplifier is S3. Then, it should satisfy: S2 > S1 > S3.

[0020] Second aspect, the present invention provides an electroencephalogram (EEG) acquisition method with active anti-magnetic interference, and the EEG acquisition method is applied to the EEG acquisition system provided by the first aspect; the EEG acquisition method includes the following steps:

[0021] S10. The subject wears the EEG acquisition electrodes, and the EEG acquisition electrodes are communicatively connected to the EEG amplifier;

[0022] S11. The magnetic sensor drives and controls the magnetic sensor to collect the magnetic interference signals and sends them to the controller;

[0023] S12. The controller performs vector decomposition on the magnetic interference signals to obtain the magnetic field magnitudes in each direction of the coil group, and the controller generates a control instruction based on the magnetic field magnitudes;

[0024] S13. The coil driver receives the control instruction to control the current magnitude of the coil group, so that the coil group generates a canceling magnetic field in each direction that is opposite to the magnetic field magnitude in the corresponding direction.

[0025] As a possible implementation, the coil group is a three-dimensional Helmholtz coil, that is, it is composed of three pairs of orthogonal Helmholtz coils; after the controller obtains the magnetic interference signals, it performs vector decomposition to obtain the magnetic field magnitudes at the centers of each pair of Helmholtz coils, and the control instruction is generated according to the magnetic field magnitudes at the centers, so that the current flowing through each pair of Helmholtz coils and the magnetic field magnitude at the center satisfy the following relationship:

[0026]

[0027] where B is the magnetic field magnitude at the center, with the unit of Tesla; μ0 is the magnetic permeability of vacuum, μ0 = 4Π×10 -7 T·m / A; n is the number of turns of each pair of Helmholtz coils; I is the current flowing through each pair of Helmholtz coils, with the unit of Ampere; R is the radius of the coil, with the unit of meter.

[0028] Compared with the prior art, the beneficial effects produced by the present invention are as follows:

[0029] 1. The active anti-magnetic interference EEG acquisition system proposed by the present invention proposes an active anti-electromagnetic interference method different from the traditional passive electromagnetic shielding method. According to the magnitude of the interference magnetic field, the anti-magnetic interference component is used to perform corresponding magnetic field compensation to cancel the electromagnetic interference, which has the advantages of strong dynamic adaptability, good shielding effect, and being applicable to complex magnetic field environments.

[0030] 2. The proposed electroencephalogram acquisition system with active anti-magnetic interference of the present invention uses a coil group composed of three pairs of orthogonal Helmholtz coils. Among them, the two pairs of Helmholtz coils on the upper and lower and left and right sides are saddle-shaped coils, and the pair of Helmholtz coils in the front and back are cylindrical coils. With such a design, it can ensure the uniformity of the coil magnetic field in the axial direction and maintain the uniformity of the radial coils.

[0031] 3. In the proposed electroencephalogram acquisition system with active anti-magnetic interference of the present invention, the coil current source has high-precision and high-bandwidth performance, can accurately and quickly compensate the spatial magnetic field, and has the function of outputting positive and negative currents, thus realizing the AC output ability. Furthermore, it can effectively suppress the magnetic noise within a specific frequency band to meet the requirements of magnetic field interference cancellation and environmental adaptability, improve the overall magnetic field processing efficiency and stability of the system, ensure that an accurate magnetic field compensation effect can still be maintained in a complex magnetic field environment, protect related equipment or systems from the adverse effects of magnetic noise, and enable them to operate stably and efficiently.

[0032] 4. The proposed electroencephalogram acquisition system with active anti-magnetic interference of the present invention requires little space, has a low layout cost, is also convenient to carry, and can achieve a more ideal magnetic field distribution within a limited space.

[0033] 5. The proposed electroencephalogram acquisition system with active anti-magnetic interference of the present invention has been proven by experiments to have excellent anti-electromagnetic interference effects, and the electromagnetic attenuation rate has reached 55.3%. Description of the Drawings

[0034] The drawings described herein are used to provide a further understanding of the present invention, form a part of the present invention, and the schematic embodiments of the present invention and their descriptions are used to explain the present invention, and do not constitute an improper limitation to the present invention. In the drawings:

[0035] Figure 1 is a schematic structural diagram of the electroencephalogram acquisition system with active anti-magnetic interference in the embodiment of the present invention;

[0036] Figure 2 is a schematic diagram of a circular Helmholtz coil in the embodiment of the present invention;

[0037] Figure 3 is a schematic diagram of the shape of a radial saddle-shaped coil in the embodiment of the present invention;

[0038] Figure 4 is a schematic structural diagram of a magnetic shielding barrel with a hollow cylindrical structure and a magnetic shielding barrel with a hollow hexahedron structure with a square Helmholtz coil inside in the embodiment of the present invention;

[0039] Figure 5 is a flowchart of the electroencephalogram acquisition method with active anti-magnetic interference in the embodiment of the present invention

[0040] Figure 6Schematic diagram of the peak value of 50Hz power frequency interference before magnetic field compensation in the embodiments of the present invention;

[0041] Figure 7 Schematic diagram of the peak value of 50Hz power frequency interference after magnetic field compensation in the embodiments of the present invention.

[0042] Reference numerals

[0043] 1 - EEG acquisition electrode, 2 - EEG amplifier, 3 - anti - magnetic interference component, 30 - magnetic shielding barrel, 31 - coil group, 32 - magnetic sensor, 33 - magnetic sensor driver, 34 - coil driver, 4 - controller, 5 - host computer. Detailed implementation manners

[0044] For the convenience of clearly describing the technical solutions of the embodiments of the present invention, in the embodiments of the present invention, terms such as "first" and "second" are used to distinguish the same items or similar items with basically the same functions and roles. For example, the first threshold and the second threshold are only used to distinguish different thresholds, and do not limit their sequence. Those skilled in the art can understand that terms such as "first" and "second" do not limit the quantity and execution order, and "first" and "second" do not necessarily mean different.

[0045] It should be noted that in the present invention, words such as "exemplary" or "for example" are used to represent examples, illustrations or explanations. Any embodiment or design solution described as "exemplary" or "for example" in the present invention should not be construed as being more preferred or having more advantages than other embodiments or design solutions. Exactly, using words such as "exemplary" or "for example" aims to present related concepts in a specific manner.

[0046] In the present invention, "at least one" means one or more, and "a plurality" means two or more. "And / or" describes the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone, where A and B can be singular or plural. The character " / " generally represents an "or" relationship between the front and rear associated objects. The following "at least one (piece)" or its similar expressions refer to any combination of these items, including any combination of single item (piece) or plural items (pieces). For example, at least one (piece) of a, b or c can represent: a, b, c, the combination of a and b, the combination of a and c, the combination of b and c, or the combination of a, b and c, where a, b, c can be single or multiple.

[0047] Embodiments of the present invention aim to propose a new shielding system and method for the electroencephalogram (EEG) field, which can actively resist magnetic interference, and has the advantages of strong dynamic adaptability, good shielding effect (especially the suppression of low-frequency magnetic fields in the EEG band), easy to carry, and applicable to complex magnetic field environments.

[0048] Embodiments of the present invention provide an EEG acquisition system with active anti-magnetic interference. Refer to Figure 1 , which includes: an EEG acquisition electrode 1, an EEG amplifier 2, an anti-magnetic interference component 3, and a controller 4;

[0049] Among them, the anti-magnetic interference component 3 includes a magnetic shielding barrel 30 and a coil group 31 disposed within the magnetic shielding barrel 30 and capable of enclosing a shielding area;

[0050] Refer to Figure 2 , as a possible implementation, the coil group 31 is a three-dimensional Helmholtz coil, that is, composed of three pairs of orthogonal Helmholtz coils. With such a setting, the uniformity of the coil magnetic field in the axial direction can be ensured to the greatest extent.

[0051] Refer to Figure 1 and Figure 3 , as a possible implementation, the magnetic shielding barrel 30 is a hollow cylindrical structure, and three pairs of orthogonal Helmholtz coils are distributed in the front-back, up-down, and left-right directions inside the barrel; among them, the two pairs of Helmholtz coils in the up-down and left-right directions are saddle-shaped coils, and the pair of Helmholtz coils in the front-back direction is a cylindrical coil. By using the saddle-shaped coil design for the coils in the up-down and left-right directions, the uniformity of the radial coils can be maintained.

[0052] The coil current source has high-precision and high-bandwidth performance, can accurately and quickly compensate for the spatial magnetic field, and has the function of outputting positive and negative currents, thereby realizing the AC output ability, and then can effectively suppress the magnetic noise in a specific frequency band, to meet the requirements of magnetic field interference cancellation and environmental adaptability, improve the overall magnetic field processing efficiency and stability of the system, ensure that an accurate magnetic field compensation effect can still be maintained in a complex magnetic field environment, protect relevant equipment or systems from the adverse effects of magnetic noise, and enable them to operate stably and efficiently.

[0053] Refer to Figure 4 , as a possible implementation, the magnetic shielding barrel 30 is a hollow cylindrical structure, as shown in (a) of Figure 4 , or a hollow hexahedral structure, as shown in (b) of Figure 4 , or a hollow octahedral structure, as shown in (c) of Figure 4 . The three pairs of orthogonal Helmholtz coils are all square Helmholtz coils. During specific implementation, it can be designed into any shape according to actual needs. It should be understood that the shape of the magnetic shielding barrel does not affect the specific implementation of this solution.

[0054] The Helmholtz coils involved in this embodiment are not limited to the traditional circular Helmholtz coils in terms of their application scope. In fact, they cover Helmholtz coils of various geometric shapes. Next, a square Helmholtz coil will be taken as an example for elaboration. In many actual application scenarios, especially in specific environments with strict requirements for space utilization efficiency and anti-interference ability, the square Helmholtz coil demonstrates unique advantages. Compared with similar devices of other shapes, the square Helmholtz coil can utilize the limited space resources within the shielding area more efficiently. Its square structural design enables better fitting to shielding areas of various shapes during layout and installation, reducing space waste, and thus achieving a more ideal magnetic field distribution within the limited space.

[0055] This optimized way of space utilization further lays a solid foundation for enhancing the anti-interference effect. When an external interfering magnetic field exists, the square Helmholtz coil, relying on its unique structure and layout, can more precisely generate a counteracting magnetic field to oppose it, effectively offsetting the influence of the interfering magnetic field. Compared with Helmholtz coils of other shapes, the square structure can arrange more turns of coils within the same space or adopt a more reasonable current distribution, thereby generating a stronger and more uniform compensation magnetic field, and further achieving more excellent anti-interference performance, providing a stable and reliable magnetic field environment guarantee for various devices and experiments with strict requirements for the magnetic field environment.

[0056] See Figure 1 , an effective area is set within the shielding area. The anti-magnetic interference component 3 further includes a magnetic sensor 32 placed within the effective area, a magnetic sensor driver 33 placed outside the magnetic shielding barrel 30, and a coil driver 34;

[0057] As a possible implementation, the magnetic field attenuation within the effective area is 3 dB.

[0058] As a possible implementation, the effective area and the shielding area are concentric. And if the area of the effective area is denoted as S1, the area of the shielding area is denoted as S2, and the area occupied by the amplifier is S3, then it should satisfy: S2 > S1 > S3.

[0059] See Figure 1 , the magnetic sensor driver 33 controls the magnetic sensor 32 to collect magnetic interference signals and sends them to the controller 4; the controller 4 performs vector decomposition on the magnetic interference signals to obtain the magnetic field magnitudes in each direction of the coil group 31. The controller 4 generates a control instruction based on the magnetic field magnitudes in each direction and sends the control instruction to the coil driver 34 to control the current magnitude of the coil group 31, so that the coil group 31 generates a canceling magnetic field in each direction that is opposite to the magnetic field magnitude in the corresponding direction.

[0060] See Figure 1, the EEG amplifier 2 is placed within the effective area. Since the coil group 31 generates a canceling magnetic field in each direction that is opposite in magnitude to the magnetic field in the corresponding direction, a low electromagnetic noise environment is created within the magnetic shielding barrel 30. The EEG signals collected by the EEG electrodes are transmitted to the EEG amplifier. The EEG amplifier is in a low-noise environment, so it can effectively process and transmit the EEG signals, protecting the EEG signals from electromagnetic interference.

[0061] As a possible implementation, after the controller obtains the magnetic interference signal, it performs vector decomposition to obtain the magnitude of the magnetic field at the center of each pair of Helmholtz coils. The control instruction generates a control instruction based on the magnitude of the magnetic field at the center, so that the current flowing through each pair of Helmholtz coils satisfies the following relationship with the magnitude of the magnetic field at the center:

[0062]

[0063] where B is the magnitude of the magnetic field at the center, in Tesla; μ0 is the magnetic permeability of vacuum, μ0 = 4Π×10 -7 T·m / A; n is the number of turns of each pair of Helmholtz coils; I is the current flowing through each pair of Helmholtz coils, in Ampere; R is the radius of the coil, in meter.

[0064] In a second aspect, an EEG acquisition method for active anti-magnetic interference provided by an embodiment of the present invention is applied to the EEG acquisition system provided in the first aspect; see Figure 5 , the EEG acquisition method includes the following steps:

[0065] S10. The subject wears the EEG acquisition electrodes, and the EEG acquisition electrodes are communicatively connected to the EEG amplifier;

[0066] S11. The magnetic sensor drive controls the magnetic sensor to collect the magnetic interference signal and sends it to the controller;

[0067] S12. The controller performs vector decomposition on the magnetic interference signal to obtain the magnitude of the magnetic field in each direction of the coil group, and the controller generates a control instruction based on the magnitude of the magnetic field;

[0068] S13. The coil driver receives the control instruction to control the current magnitude of the coil group, so that the coil group generates a canceling magnetic field in each direction that is opposite in magnitude to the magnetic field in the corresponding direction.

[0069] As a possible implementation, the coil group is a three-dimensional Helmholtz coil, that is, it is composed of three pairs of orthogonal Helmholtz coils; after the controller obtains the magnetic interference signal, it performs vector decomposition to obtain the magnitude of the magnetic field at the center of each pair of Helmholtz coils. The control instruction generates a control instruction based on the magnitude of the magnetic field at the center, so that the current flowing through each pair of Helmholtz coils satisfies the following relationship with the magnitude of the magnetic field at the center:

[0070]

[0071] Among them, B is the magnitude of the magnetic field at the center, with the unit of Tesla; μ0 is the magnetic permeability of vacuum, μ0 = 4Π×10 -7 T·m / A; n is the number of turns of each pair of Helmholtz coils; I is the current flowing through each pair of Helmholtz coils, with the unit of Ampere; R is the radius of the coil, with the unit of meter.

[0072] The following further elaborates on this embodiment in combination with specific experiments. In this experiment, an electroencephalogram (EEG) acquisition system is used to perform magnetic field compensation for electromagnetic interference.

[0073] Refer to Figure 1 , place the EEG amplifier in the internal space of the EEG acquisition system, and use the EEG acquisition electrode 1 to collect EEG signals. After the EEG signals are amplified and processed by the EEG amplifier 2, they are transmitted to the host computer 5, and then the corresponding EEG signal information is displayed on the host computer 5. Record the relevant data of the EEG acquisition system before and after the magnetic field compensation operation respectively, as shown in Table 1:

[0074] Table 1 Peak-to-peak value of 50Hz power frequency interference before and after magnetic field compensation

[0075]

[0076] Then transmit the recorded data to the host computer, store these data through the host computer, and observe their corresponding spectra. Refer to Figure 6 and Figure 7 , through magnetic field compensation, the peak amplitude of the 50Hz power frequency interference is significantly reduced from an average of 6.04uV to 2.7uV, and the attenuation rate reaches 55.3%. This indicates that this system plays an obvious role in reducing magnetic field interference.

[0077] Although the present invention has been described in combination with various embodiments herein, however, in the process of implementing the claimed invention, those skilled in the art can understand and achieve other variations of the disclosed embodiments by viewing the drawings, the disclosure content, and the drawings' descriptions, etc. In the specification, the word "comprising" does not exclude other components or steps, and "a" or "one" does not exclude a plurality. A single processor or other unit can implement several functions listed in the specification. Certain measures are described in different embodiments, but this does not mean that these measures cannot be combined to produce good effects.

[0078] Although the present invention has been described in connection with specific features and their embodiments, it will be apparent that various modifications and combinations can be made without departing from the spirit and scope of the invention. Accordingly, the present specification and drawings are merely exemplary illustrations of the invention and are considered to cover any and all modifications, variations, combinations, or equivalents within the scope of the invention. Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the invention. Thus, if these modifications and variations of the present invention fall within the scope of the present invention and its equivalent technologies, the present invention is also intended to include these changes and modifications.

Claims

1. An electroencephalogram acquisition system with active anti-magnetic interference, characterized in that, Comprising: EEG acquisition electrodes, an EEG amplifier, an anti-magnetic interference component, and a controller; Wherein, the anti-magnetic interference component includes a magnetic shielding barrel, a coil group disposed within the magnetic shielding barrel and capable of enclosing a shielding region, an effective region is disposed within the shielding region; a magnetic sensor placed within the effective region, a magnetic sensor driver and a coil driver disposed outside the magnetic shielding barrel; The EEG amplifier is disposed within the effective region; The magnetic sensor driver controls the magnetic sensor to collect magnetic interference signals and sends them to the controller; the controller performs vector decomposition on the magnetic interference signals to obtain the magnetic field magnitudes in each direction of the coil group, and the controller generates a control instruction based on the magnetic field magnitudes in each direction, and sends the control instruction to the coil driver to control the current magnitude of the coil group, so that the coil group generates a canceling magnetic field in each direction that is opposite to the magnetic field magnitude in the corresponding direction.

2. The electroencephalogram acquisition system with active anti-magnetic interference according to claim 1, wherein The magnetic field within the effective region is attenuated by 3 dB.

3. The electroencephalogram acquisition system with active anti-magnetic interference according to claim 1, characterized in that The coil group is a three-dimensional Helmholtz coil, that is, it is composed of three pairs of orthogonal Helmholtz coils.

4. The electroencephalogram acquisition system with active anti-magnetic interference according to claim 3, wherein, After the controller obtains the magnetic interference signal, it performs vector decomposition to obtain the magnetic field magnitude at the center of each pair of Helmholtz coils, and generates a control instruction according to the magnetic field magnitude at the center, so that the current flowing through each pair of Helmholtz coils satisfies the following relationship with the magnetic field magnitude at the center: Among them, B is the magnetic field magnitude at the center, with the unit of Tesla; μ0 is the magnetic permeability of vacuum, μ0 = 4Π×10 -7 T·m / A; n is the number of turns of each pair of Helmholtz coils; I is the current flowing through each pair of Helmholtz coils, with the unit of Ampere; R is the radius of the coil, with the unit of meter.

5. The electroencephalogram acquisition system with active anti-magnetic interference according to claim 1, wherein The magnetic shielding barrel is a hollow cylindrical structure, and three pairs of orthogonal Helmholtz coils are distributed in the front-back, up-down, and left-right directions inside the barrel; among them, the two pairs of Helmholtz coils in the up-down and left-right directions are saddle-shaped coils, and the pair of Helmholtz coils in the front-back direction is a cylindrical coil.

6. The electroencephalogram acquisition system with active anti-magnetic interference according to claim 1, wherein The magnetic shielding barrel is a hollow cylindrical structure or a hollow hexahedral structure, and the three pairs of orthogonal Helmholtz coils are all square Helmholtz coils.

7. The electroencephalogram acquisition system with active anti-magnetic interference according to claim 1, characterized in that, The effective region and the shielding region are co-centered, and the area of the effective region is denoted as S1, the area of the shielding region is denoted as S2, and the area occupied by the amplifier is S3, then it should satisfy: S2 > S1 > S3.

8. A method for electroencephalogram acquisition with active anti-magnetic interference, characterized in that, The EEG acquisition method is applied to the EEG acquisition system according to any one of claims 1 to 7; the EEG acquisition method includes the following steps: S10. The subject wears the EEG acquisition electrodes, and the EEG acquisition electrodes are communicatively connected to the EEG amplifier; S11. The magnetic sensor driver controls the magnetic sensor to collect magnetic interference signals and sends them to the controller; S12. The controller performs vector decomposition on the magnetic interference signals to obtain the magnetic field magnitudes in each direction of the coil group, and the controller generates a control instruction based on the magnetic field magnitudes; S13. The coil driver receives the control instruction to control the current magnitude of the coil group, so that the coil group generates a canceling magnetic field in each direction that is opposite to the magnetic field magnitude in the corresponding direction.

9. The electroencephalogram acquisition method for actively resisting magnetic interference according to claim 8, wherein, The coil group is a three-dimensional Helmholtz coil, that is, it is composed of three pairs of orthogonal Helmholtz coils; after the controller obtains the magnetic interference signal, it performs vector decomposition to obtain the magnetic field magnitude at the center of each pair of Helmholtz coils, and generates a control instruction according to the magnetic field magnitude at the center, so that the current flowing through each pair of Helmholtz coils satisfies the following relationship with the magnetic field magnitude at the center: Among them, B is the magnitude of the magnetic field at the center, with the unit of Tesla; μ0 is the magnetic permeability of vacuum, μ0 = 4Π×10 -7 T·m / A; n is the number of turns of each pair of Helmholtz coils; I is the current flowing through each pair of Helmholtz coils, with the unit of Ampere; R is the radius of the coil, with the unit of meter.

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