A magnetic field immune system

Abstract

The present application relates to the field of magnetic field detection, in particular to a magnetic field immune system, which is provided with a target magnetic field S to be detected externally, including: a three-axis magnetic sensor for measuring the magnetic field components B of the X-axis, Y-axis and Z-axis x 、B y and B z , wherein a spatial rectangular coordinate system is established with the three-axis magnetic sensor as the origin, and the straight line where the three-axis magnetic sensor and the target magnetic field S are located is the Z axis; two single-axis magnetic sensors are used to measure the Z-axis magnetic field component B z , are arranged symmetrically about the three-axis magnetic sensor, wherein the two single-axis magnetic sensors and the three-axis magnetic sensor are located in the same plane, and the plane is the plane shared by the X-axis and the Y-axis, and the Z-axis is perpendicular to the plane. The layout design of this application helps detect and correct magnetic field tilt errors, ensuring more accurate magnetic field measurements in the XY plane.

Description

Technical Field

[0001] The present application relates to the field of magnetic field detection, and in particular to a magnetic field immune system. Background Art

[0002] The magnetic field immunity correction algorithm is a technology based on the symmetrical layout of sensors and external magnetic field modeling, which is used to remove the interference of external contamination magnetic fields (external magnetic fields, external fields) on the target magnetic field measurement.

[0003] Currently, commercially available technologies typically utilize a wider array of sensors, either primarily to increase detection coverage or to enhance detection accuracy. However, those skilled in the art understand that employing more sensors increases computational complexity, increasing algorithm and system complexity and making them more susceptible to failure. Furthermore, ensuring consistency across multiple sensors can easily introduce uneven errors, further increasing system complexity. Summary of the Invention

[0004] In order to calculate and dynamically compensate for external magnetic field interference in real time, the present application provides a magnetic field immune system.

[0005] The present application provides a magnetic field immune system, which adopts the following technical solutions: a magnetic field immune system, which is provided with a target magnetic field S to be detected on the outside, including: a three-axis magnetic sensor for measuring the magnetic field components B of the X-axis, Y-axis and Z-axis x 、B y and B z , wherein a spatial rectangular coordinate system is established with the three-axis magnetic sensor as the origin, and the straight line where the three-axis magnetic sensor and the target magnetic field S are located is the Z axis; two single-axis magnetic sensors are used to measure the Z-axis magnetic field component B z , arranged at a symmetrical position with the three-axis magnetic sensor as a symmetrical point, wherein the two single-axis magnetic sensors and the three-axis magnetic sensor are located in the same plane, and the plane is the plane in which the X-axis and the Y-axis are located, and the Z-axis is perpendicular to the plane.

[0006] A further solution is to further include two other single-axis magnetic sensors, which are distributed around the three-axis magnetic sensor at equal distances and angles on the X-axis and Y-axis planes to form two groups of single-axis magnetic sensors arranged in symmetrical positions.

[0007] A further solution is to obtain the magnetic field component EB of the external magnetic field on the Z axis based on the measurement values ​​of one or two groups of the single-axis magnetic sensor groups. z , and use EB z Correct the measurement value of the three-axis magnetic sensor to obtain the Z-axis magnetic field component SB of the target magnetic field at the three-axis magnetic sensor z .

[0008] A further solution is to use the measurement value of one of the uniaxial magnetic sensor groups and the X-axis proportional coefficient k x , obtain the magnetic field component EB of the external magnetic field on the X axis x , according to the measurement value of the other group of uniaxial magnetic sensors and the Y-axis proportional coefficient k y , obtain the magnetic field component EB of the external magnetic field on the Y axis y , and use EB x , EB y Correct the measurement value of the three-axis magnetic sensor to obtain the X-axis and Y-axis magnetic field components SB of the target magnetic field at the three-axis magnetic sensor x and SB y .

[0009] A further solution is, wherein: the magnetic field component EB of the external magnetic field on the X axis is x The result is obtained by adding the measured values ​​of one of the uniaxial magnetic sensor groups and multiplying the sum by the X-axis proportional coefficient k. x ; Target magnetic field component SB on the X axis x The magnetic field component EB of the external magnetic field on the X axis is obtained by subtracting the measured value of the three-axis magnetic sensor on the X axis from the magnetic field component EB of the external magnetic field on the X axis. x The magnetic field component EB of the external magnetic field on the Y axis y The result is obtained by adding the measured values ​​of the other group of the single-axis magnetic sensor groups and multiplying them by the Y-axis proportional coefficient k. y ; Target magnetic field component SB on the Y axis y The magnetic field component EB of the external magnetic field on the Y axis is obtained by subtracting the measured value of the three-axis magnetic sensor on the Y axis from the magnetic field component EB of the external magnetic field on the Y axis. y .

[0010] A further solution is that the X-axis scale factor k x The calculation step includes: obtaining the initial external magnetic field bias value EB of the X axis of the three-axis magnetic sensor x[0] ; Obtain the initial measurement value B of one of the groups of the uniaxial magnetic sensor groups z1[0] and B z3[0] ; The initial measurement value B of one of the groups of the uniaxial magnetic sensor group z1[0] and B z3[0] The sum is then divided by the initial external magnetic field bias value EB of the X axis of the three-axis magnetic sensor x[0] , that is, to obtain the X-axis scale coefficient k x .

[0011] A further solution is that the Y-axis scale factor k yThe calculation step includes: obtaining the initial external magnetic field bias value EB of the Y axis of the three-axis magnetic sensor y[0] ; Obtain the initial measurement value B of the other group of the uniaxial magnetic sensor group z2[0] and B z4[0] The initial measurement value B of another group of the uniaxial magnetic sensor group z2[0] and B z4[0] The sum is then divided by the initial external magnetic field bias value EB of the Y axis of the three-axis magnetic sensor y[0] , that is, to obtain the Y-axis scale coefficient k y .

[0012] A further solution is to dynamically adjust the initial measurement values ​​B of the two groups of uniaxial magnetic sensors when the external magnetic field strength changes slowly. z1[0] ,B z2[0] ,B z3[0] and B z4[0] , according to the X-axis scale factor k x and Y-axis scale factor k y , linearly update the initial external magnetic field bias values ​​EB of the X-axis and Y-axis of the three-axis magnetic sensor x[0] and EB y[0] .

[0013] A further solution is to calculate the angle of the target magnetic field in the X-axis and Y-axis planes by subtracting the measurement values ​​of one group of the single-axis magnetic sensor groups to obtain the difference component Δx and subtracting the measurement values ​​of the other group of the single-axis magnetic sensor groups to obtain the difference component Δy. .

[0014] A further solution is to correct the interference in the four single-axis magnetic sensors according to the data of the three-axis magnetic sensor and obtain the angle of the target magnetic field in the X-axis and Y-axis planes, specifically including: assuming the target magnetic field is S(SB x ,SB y ,SB z ), the external magnetic field is E(EB x ,EB y ,EB z ), the three-axis magnetic sensor measures the three-axis magnetic field simultaneously, and the reading obtained is B x =SB x +EB x ,B y =SB y +EB y ,B z =SB z +EB z ; Assume that the target magnetic field is mainly concentrated in the horizontal plane, that is , then the Z-axis component of the three-axis magnetic sensor is ; The four single-axis magnetic sensors only measure the magnetic field in the Z-axis direction, and their measured values ​​are recorded as , i=1, 2, 3, 4, the measured value at each single-axis magnetic sensor can be written as ,in, is the amplitude of the signal in the X-axis and Y-axis planes, θ is the true angle of the target magnetic field in the horizontal plane, is the theoretical arrangement angle of the i-th uniaxial magnetic sensor, where , , , , k i is the gain factor of the i-th single-axis magnetic sensor. At the same time, the contribution of the external magnetic field interference to the four single-axis magnetic sensors is proportionally different from that of the central three-axis magnetic sensor, which is recorded as , where a i is the proportional coefficient of the response of the i-th uniaxial magnetic sensor to the external magnetic field interference; In summary, the readings of the four uniaxial magnetic sensors can be written as ; Perform interference correction on the four single-axis magnetic sensor data and define the corrected value as , after substituting into ; Assume that all peripheral single-axis magnetic sensors have the same gain after initial calibration, that is, k i =k, where k is a constant, then ; Using the symmetry of the two groups of single-axis magnetic sensors, the two groups of single-axis magnetic sensors are differentiated to obtain: , ; then there is , so we can get .

[0015] A further solution is that the proportional coefficient a of the response of the i-th uniaxial magnetic sensor to the external magnetic field interference is i The evaluation steps include: setting the target magnetic field to zero in the initial calibration stage; measuring B with the three-axis magnetic sensor; zcal =EB z , four uniaxial magnetic sensors measure B zical =EB zi ; Assume EB zi =a i ·EB z ; It can be deduced that B zical =a i ·B zcal , sorted out .

[0016] In summary, the layout design of this application helps to detect and correct the tilt error of the magnetic field, ensuring more accurate magnetic field measurement in the XY plane. The uniqueness of this layout is that it can eliminate or reduce the impact of magnetic field tilt on measurement by fusing the outputs of the surrounding single-axis magnetic sensors while keeping the layout simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the layout design diagram of the magnetic field immune system for this application.

[0018] Figure 2 This is a sensor layout design diagram of an embodiment of the present application.

[0019] Figure 3 This is a sensor layout design diagram of another embodiment of the present application. DETAILED DESCRIPTION

[0020] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of technical features indicated. Therefore, features specified as "first" or "second" may explicitly or implicitly include one or more of such features.

[0021] The following describes an embodiment of the present application in conjunction with the drawings in the specification, but the embodiment should not be understood as limiting the present application.

[0022] like Figure 1 and Figure 2 As shown, an embodiment of the present application provides a magnetic field immune system, in which a target magnetic field S to be detected is set externally. The system includes a central sensor (three-axis magnetic sensor) and two peripheral sensors (single-axis magnetic sensors). Figure 1 Shown is a schematic diagram of the magnetic field lines of the target magnetic field (magnet), the magnetic field lines at the location of each sensor, and the magnetic field strength sensed by each sensor. Figure 1 Display the system layout from a longitudinal section in three-dimensional space. Figure 2 From Figure 1 The plane perpendicular to the plane shown shows the system layout. Figure 2 In the diagram, the two peripheral sensors are identified with special symbols to indicate the direction of the magnetic field they measure.

[0023] A spatial rectangular coordinate system is established with the central sensor as the origin. The two peripheral sensors and the central sensor are placed on the same straight line, with this line being the X-axis. The target magnetic field S is placed outside this line, and the line between the target magnetic field S and the central sensor is perpendicular to the X-axis, with this line being the Z-axis. Another straight line is drawn perpendicular to both the X- and Z-axes, with this line being the Y-axis. The plane containing the X- and Y-axes is the XY plane, or horizontal plane.

[0024] In this embodiment, the coordinates of the two peripheral sensors on the X axis are B z1 (R, 0), B z3 (-R, 0), where R is the distance between the central sensor and the peripheral sensors, that is, the two peripheral sensors are symmetrically arranged on both sides of the central sensor.

[0025] The center sensor (three-axis magnetic sensor) can use a sensor whose output electrical signal strength is proportional to the magnitude of the magnetic field strength it senses. For example, the embodiment of the present application can use a three-axis (3D) Hall sensor that can simultaneously measure the three-axis magnetic field components B of the X-axis, Y-axis, and Z-axis. x 、B y and B z , the measurement results include the target magnetic field S (SB x , SB y , SB z ) and the external magnetic field E(EB x , EB y , EB z ), that is: B x =SB x +EB x , B y =SB y +EB y , B z =SB z +EB z ;

[0026] The two peripheral sensors (single-axis magnetic sensors) can use sensors whose output electrical signal strength is proportional to the magnitude of the magnetic field strength they sense. For example, the embodiments of the present application can all use linear Hall sensors that measure a single direction component (for example, in this embodiment, only the magnetic field component in the Z-axis direction needs to be measured). A linear Hall sensor refers to a Hall sensor whose output electrical signal strength is proportional to the magnitude of the magnetic field strength it senses. In addition, the two peripheral sensors are arranged at symmetrical positions with the three-axis Hall sensor as the symmetrical point. For example, in this embodiment, they are arranged on the positive and negative axes of the X-axis, and are used to measure the Z-axis magnetic field component that is the superposition of the target magnetic field S and the external magnetic field E. The measured values ​​are recorded as B and B respectively. z1 =SB z1 +EB z1 and B z3 =SB z3 +EB z3 .

[0027] The target magnetic field S is a close-range, two-pole magnetic source, including a magnetic ring, pancake magnet, or bar magnet. The center of the radial secondary magnet or secondary magnetic ring is located on the Z axis, so that the Z-axis magnetic field components of the target magnetic field S at any two locations symmetrical about the origin on the XY plane are equal in magnitude and opposite in direction.

[0028] The external magnetic field E comes from a distant magnetic source, and its direction is approximately fixed, similar to "parallel light" illuminating the entire sensor array. Since the magnetic source of the external magnetic field E is far away, it can be considered that the external magnetic field E changes uniformly in space, without considering the part of the external magnetic field E that changes non-uniformly in space.

[0029] In order to obtain a pure target magnetic field value, it is necessary to x ,B y ,B z Eliminate the external magnetic field E (EB x , EB y , EB z The present application adopts a symmetrical layout design so that the contributions of the target magnetic field S can cancel each other in the z-axis component of the peripheral sensors, leaving the main external magnetic field E information.

[0030] Specifically, for the two peripheral sensors B at symmetrical positions on the X axis z1 and B z3 , the measured values ​​are: B z1 =SB z1 +EB z1 , B z3 =SB z3 +EB z3 Since these two peripheral sensors B z1 and B z3 Arranged at the symmetrical position of the target magnetic field S, so that the Z-axis components of the target magnetic field S at these two points are equal in magnitude and opposite in direction, that is, SB z1 =-SB z3 .

[0031] Therefore, the two peripheral sensors B z1 and B z3 Add the measured values ​​to get: B z1 +B z3 =(SB z1 +SB z3 )+(EB z1 +EB z3 ) =EB z1 +EB z3 Considering only the part of the external magnetic field E that varies uniformly in space, we know that EB z1 +EB z3 ≈2EB z, therefore, it can be deduced that: B z1 +B z3 =2EB z .

[0032] Further EB z =(B z1 +B z3 ) / 2, that is, the Z-axis component of the external magnetic field E is the peripheral sensor B z1 and B z3 half of the sum of the measured values, which indicates that the symmetrical position of sensor B z1 and B z3 The Z-axis component of the target magnetic field S is canceled out by adding the measured values, leaving only the contribution of the external magnetic field E. After obtaining the Z-axis component value EB of the external magnetic field E at the center sensor z Then the pure target magnetic field value SB on the Z axis at the center sensor is z By formula SB z =B z -EB z You can get it.

[0033] Because the external magnetic field E originates from a distant magnetic source, its direction is approximately fixed. This means that the proportional relationship between the X, Y, and Z components of the external magnetic field E is stable. When the external magnetic field E changes several times in the Z-axis direction, the components in the X and Y-axis directions also change by the same multiple. For the specific calculation process, please refer to the calculation process using four peripheral sensors in the next embodiment.

[0034] like Figure 1 and Figure 3 As shown, another embodiment of the present application provides a magnetic field immune system, including a central sensor (three-axis magnetic sensor) and four peripheral sensors (single-axis magnetic sensors). Figure 1 The system layout is displayed from the longitudinal section of the three-dimensional space, so the two additional peripheral sensors are Figure 1 Not visible in. Figure 3 From Figure 1 The plane perpendicular to the plane shown shows the system layout. Figure 3 In the diagram, the four peripheral sensors are identified with special symbols to indicate the direction of the magnetic field they measure.

[0035] A spatial rectangular coordinate system is established with the central sensor as the origin, where two peripheral sensors (such as B z1 and B z3 ) are set on the same straight line with the center sensor, with the straight line as the X axis, and the other two peripheral sensors (such as B z2 and B z4) is arranged on another straight line with the center sensor, and the straight line is perpendicular to the other straight line, with the other straight line being the Y axis, and the plane where the X axis and the Y axis are located is the XY plane, or horizontal plane, and the target magnetic field S is arranged outside the XY plane, and the target magnetic field S is perpendicular to the XY plane with another straight line where the center sensor is located, with the straight line being the Z axis; wherein the center sensor (three-axis magnetic sensor) can adopt a sensor whose output electrical signal strength is proportional to the magnitude of the magnetic field strength felt. For example, the embodiment of the present application can adopt a three-axis (3D) Hall sensor, which can simultaneously measure the three-axis magnetic field component B x 、B y and B z , the measurement results include the target magnetic field S (SB x , SB y , SB z ) and the external magnetic field E(EB x , EB y , EB z ), wherein the target magnetic field S and the external magnetic field E are the same as those in the previous embodiment and will not be described in detail herein, namely: x =SB x +EB x , B y =SB y +EB y , B z =SB z +EB z ; The four peripheral sensors (single-axis magnetic sensors) can adopt sensors whose output electrical signal strength is proportional to the magnitude of the magnetic field strength they sense. For example, the embodiments of the present application can all adopt linear Hall sensors that measure a single direction component (for example, in this embodiment, only the magnetic field component in the Z-axis direction needs to be measured), and the four peripheral sensors are equidistantly distributed around the central three-axis Hall sensor on the positive and negative X axes and the positive and negative Y axes, and are used to measure the Z-axis magnetic field component that is the superposition of the target magnetic field S and the external magnetic field E. The measured values ​​are recorded as B z1 =SB z1 +EB z1 、B z2 =SB z2 +EB z2 、B z3 =SB z3 +EB z3 and B z4 =SB z4 +EB z4 In this embodiment, the coordinates of the four peripheral sensors in the XY plane are B z1 (R, 0), B z2 (0, R), B z3 (-R, 0), B z4(0, -R), where R is the distance between the center sensor and the peripheral sensors.

[0036] In order to obtain a pure target magnetic field value, it is necessary to measure the value B from the triaxial sensor. x ,B y ,B z Eliminate the external magnetic field E (EB x , EB y , EB z ), the present application adopts a symmetrical layout design so that the contributions of the target magnetic field S can cancel each other out in the z-axis component of the peripheral sensor, leaving the main external magnetic field E information.

[0037] Specifically, for the two peripheral sensors B at symmetrical positions on the X axis z1 and B z3 , the measured values ​​are: B z1 =SB z1 +EB z1 , B z3 =SB z3 +EB z3 Since these two peripheral sensors B z1 and B z3 Arranged at the symmetrical position of the target magnetic field S, so that the Z-axis components of the target magnetic field S at these two points are equal in magnitude and opposite in direction, that is, SB z1 =-SB z3 Therefore, the two peripheral sensors B z1 and B z3 Add the measured values ​​to get: B z1 +B z3 =(SB z1 +SB z3 )+(EB z1 +EB z3 ) =EB z1 +EB z3 ; From the uniform change characteristics of the external magnetic field E, it can be deduced that: B z1 +B z3 =2EB z , further derive EB z =(B z1 +B z3 ) / 2, that is, the Z-axis component of the external magnetic field E is the peripheral sensor B z1 and B z3 half of the sum of the measured values, which indicates that the symmetrical position of sensor B z1 and B z3 By adding the measured values ​​of the target magnetic field S, the Z-axis component of the target magnetic field S is completely cancelled, leaving only the contribution of the external magnetic field E.

[0038] Similarly, for the two symmetrical peripheral sensors B on the Y axis z2 and B z4 , the measured values ​​are: B z2 =SB z2 +EB z2 , B z4 =SB z4 +EB z4 Since these two peripheral sensors B z2 and B z4 Arranged at the symmetrical position of the target magnetic field S, so that the Z-axis components of the target magnetic field S at these two points are equal in magnitude and opposite in direction, that is, SB z2 =-SB z4 Therefore, the two peripheral sensors B z2 and B z4 Add the measured values ​​to get: B z2 +B z4 =(SB z2 +SB z4 )+(EB z2 +EB z4 ) = 0 + EB z2 +EB z4 ; According to the uniform distribution characteristics of the external magnetic field E, we know that EB z2 ≈EB z4 ≈EB z , therefore, it can be deduced that: B z2 +B z4 =2EB z , further derive EB z =(B z2 +B z4 ) / 2, that is, the Z-axis component of the external magnetic field E is the peripheral sensor B z2 and B z4 half of the sum of the measured values, which indicates that the symmetrical position of sensor B z2 and B z4 By adding the measured values ​​of the target magnetic field S, the Z-axis component of the target magnetic field S is completely cancelled, leaving only the contribution of the external magnetic field E.

[0039] It is understood that the Z-axis component of the external magnetic field E can also be the peripheral sensor B z1 、B z2 、B z3 and B z4 One quarter of the sum of the measured values. By using the sum of the measured values ​​of the four peripheral sensors to calculate the Z-axis component of the external magnetic field E, the influence of the inhomogeneity of the peripheral sensors will be reduced. When obtaining the Z-axis component value EB of the external magnetic field E z After that, the pure target magnetic field value SB on the Z axis z By formula SB z =Bz -EB z You can get it.

[0040] Since the external magnetic field E comes from a distant magnetic source, its direction is approximately fixed, which means that the proportional relationship between the X, Y, and Z components of the external magnetic field E is stable. When the external magnetic field E changes several times in the Z-axis direction, the components in the X-axis and Y-axis directions also change by the same multiple.

[0041] Based on the above assumptions, the following mapping relationship is established: EB x =k x (B z1 +B z3 ),EB y =k y (B z2 +B z4 ), where k x is the proportional coefficient of the external magnetic field E in the X-axis and Z-direction, referred to as the X-axis proportional coefficient, k y Is the proportional coefficient of the external magnetic field E in the Y and Z directions, referred to as the Y-axis proportional coefficient, (B z1 +B z3 ) is the peripheral sensor B z1 and B z3 The summed result represents the change of the external magnetic field E in the Z-axis direction, (B z2 +B z4 ) is the peripheral sensor B z2 and B z4 The summed result represents the change of the external magnetic field E in the Z-axis direction; k is determined by initial calibration x and k y (The initial calibration process is described below), and this fixed proportional relationship is used in subsequent measurements to achieve EB x and EB y Dynamic updates.

[0042] Specifically, the target magnetic field values ​​SB of the X-axis and Y-axis x and SB y It can be obtained by following the steps below.

[0043] First, perform initial calibration.

[0044] Specifically, in an environment without target magnetic field S and only with the influence of external magnetic field E, the initial measurement values ​​B of the four peripheral sensors are recorded. z1[0] ,B z2[0] ,B z3[0] ,B z4[0] , and the initial measurement value EB of the center sensor x[0] ,EB y[0](Because it is only the initial measurement value of the external magnetic field E, it is called the "initial external magnetic field bias value", where EB x[0] and EB y[0] Refers to the external magnetic field bias value at time 0). The X-axis scale factor and the Y-axis scale factor are calculated using these values, as shown in the following equations (1) and (2):

[0045] k x =EB x[0] / (B z1[0] +B z3[0] ) (1)

[0046] k y =EB y[0] / (B z2[0] +B z4[0] ) (2)

[0047] Secondly, the external magnetic field bias value at any time t is calculated in real time.

[0048] Specifically, at any time t, the measurement values ​​B of the four peripheral sensors are read. z1[t] 、B z2[t] 、B z3[t] 、B z4[t] , calculate the current external magnetic field bias value EB at time t x[t] and EBy [t] :

[0049] (3)

[0050] (4)

[0051] Substituting (1) and (2) into (3) and (4) respectively, we get:

[0052] ,

[0053] .

[0054] Finally, the center sensor is offset compensated.

[0055] Specifically, the target magnetic field S is introduced, and the measurement value B of the central sensor at time t is x[t] ,B y[t] ,B z[t] , deduct the external magnetic field bias value through the following formula to obtain the pure target magnetic field value SB on the X-axis and Y-axis x and SB y : .

[0056] It can be understood that when the magnetic field strength of the external magnetic field E changes slowly, since the direction of the external magnetic field E does not change, and the output value of the three-axis Hall sensor changes linearly with the change of the magnitude of the external magnetic field E, the initial value B of the peripheral sensor can also be dynamically measured or adjusted. z1[0] ,B z2[0] ,B z3[0] ,B z4[0] and the initial external magnetic field bias value EB of the center sensor x[0] ,EB y[0] Specifically, through the formula EB x[0] =k x (B z1[0] +B z3[0] ), EB y[0] =k y (B z2[0] +B z4[0] ), where, when the direction of the external magnetic field E remains unchanged, k x and k y unchanged, and B obtained by re-measurement z1[0] ,B z2[0] ,B z3[0] ,B z4[0] You can update EB x[0] ,EB y[0] By filtering the readings of peripheral sensors, eliminating the influence of interference fields, and updating EB x[0] ,EB y[0] , thereby adapting to changes in the external magnetic field E (that is, when the external magnetic field E changes, the measurement results can also change adaptively).

[0057] Through the above derivation, the addition of the measurement values ​​of the symmetrically arranged peripheral sensors can effectively eliminate the influence of the target magnetic field S, thereby extracting the main components of the external magnetic field E in the X, Y, and Z axis directions (EB x , EB y , EB z ), and then from B x ,B y ,B z Eliminate the external magnetic field E (EB x , EB y , EB z ) to obtain a pure target magnetic field value.

[0058] After obtaining the pure target magnetic field value (SB x , SB y , SB z ), the rotation angle θ of the magnet relative to the sensor group can be obtained by looking up the table or taking the approximate tangent.

[0059] The sensor arrangement of this embodiment employs a central three-axis Hall effect sensor for measuring magnetic fields in the X, Y, and Z axes, and four linear Hall effect sensors arranged at 90-degree angles around it at equal radii for measuring the magnetic field component in the Z axis. This layout design facilitates the detection and correction of magnetic field tilt errors, ensuring more accurate magnetic field measurements in the XY plane. This layout is unique in that it can eliminate or reduce the impact of magnetic field tilt on measurements by fusing the outputs of the surrounding linear Hall effect sensors, while maintaining a simple layout. Furthermore, this application specifies that there are only four linear Hall effect sensors surrounding the central three-axis Hall effect sensor. This selection ensures detection accuracy while simplifying system complexity. The 90-degree symmetrical arrangement of the four linear Hall effect sensors allows the magnetic field gradient to be determined through simple calculations, without requiring additional sensors. Existing magnetic field detection methods may use more sensors to improve accuracy. However, as those skilled in the art know, more sensors involve more calculations and require consistency between the multiple sensors. This application only requires four linear Hall effect sensors, logically avoiding or reducing these shortcomings.

[0060] It is understood that with the sensor arrangement of this embodiment, the distances between the center point and two pairs of linear Hall sensors can be different, but the distances between the same pair of linear Hall sensors and the center point are equal. Furthermore, three or four pairs of linear Hall sensors can be arranged around the perimeter. Having more peripheral sensors can reduce errors caused by manufacturing non-uniformity between sensors.

[0061] In the above embodiment, the manufacturing non-uniformity of the peripheral sensors may affect the measurement. Next, another embodiment is described, in which the measurement value of the central sensor can be used to correct the non-uniformity of the peripheral sensors.

[0062] like Figure 3 As shown, this embodiment uses the Z-axis data collected by four peripheral linear Hall sensors (a specific embodiment of a single-axis magnetic sensor) to measure the signal angle. The four peripheral linear Hall sensors are located at 0°, 90°, 180°, and 270° directions, respectively. The Z-axis magnetic field component measured by each linear Hall sensor can be written as: B zi =SB zi +EB zi , where i=1, 2, 3, 4, SB zi represents the Z-axis component of the target magnetic field S at the i-th linear Hall sensor; EB zi represents the Z-axis component of the external magnetic field E at the i-th linear Hall sensor.

[0063] In the ideal case where there is no external magnetic field interference or the external magnetic field interference can be ignored, it can be expressed as ,in , is the amplitude of the target magnetic field S in the XY plane (which can be regarded as the size of the "horizontal component"); θ is the direction angle of the target magnetic field S in the XY plane (that is, the relative rotation angle between the magnet and the sensor), is the layout angle of linear Hall sensor i (for example, the layout angles of the 1st, 2nd, 3rd, and 4th linear Hall sensors are 0°, 90°, 180°, and 270°, respectively); k is the geometric and sensitivity factor of the linear Hall sensor. Since the four peripheral sensors are usually made by the same manufacturing process, their k values ​​are assumed to be the same (the proportional coefficient that converts the in-plane magnetic field component to the sensor's Z-axis output).

[0064] If there is external magnetic field interference, If the external magnetic field is approximately equal at the four linear Hall sensors, it can be expressed as EB zi ≈EB z .

[0065] For sensors at symmetrical positions (0° and 180°, 90° and 270°), differential analysis can be performed to eliminate (or weaken) certain symmetrical components and highlight the orthogonal components of the target magnetic field S.

[0066] Specifically, the difference between 0° and 180° directions: , if the external magnetic field can be ignored, then, , so there is .

[0067] Similarly, the difference between 90° and 270° directions: , if the external magnetic field can be ignored, then , , so there is .

[0068] Right now , from which the angle of the target magnetic field S in the XY plane can be estimated .

[0069] When there is a parallel external magnetic field E at a long distance and with a roughly fixed direction, it is assumed that the Z-axis contribution of the external magnetic field E on each peripheral linear Hall sensor is approximately equal, that is, EB z1 ≈EB z2 ≈EB z3 ≈EB z4 ≈EB z , then the total output of the four linear Hall sensors can be written as It should be noted that if the external magnetic field E is exactly the same at the four linear Hall sensors, it will cancel each other out in the differential. However, if there is non-uniformity between the linear Hall sensors, residual errors will be introduced.

[0070] remember , .

[0071] Substituting the external magnetic field term, we can obtain:

[0072] ,

[0073] .

[0074] If the external magnetic field E is exactly the same at the four linear Hall sensors (i.e. EB z1 ≈EB z2 ≈EB z3 ≈EB z4 ≈EB z ), the external magnetic field component in the differential will be completely cancelled, and the angle calculation is still .

[0075] However, in actual situations, there are often slight differences between the four linear Hall sensors, resulting in or This leaves a residual disturbance in Δx or Δy, which makes tanθ 计算 ≠tanθ. In other words, the angle calculation will produce a certain deviation, the magnitude of which depends on the degree of non-uniformity of the external magnetic field interference between each pair of linear Hall sensors.

[0076] In order to reduce the deviation between the calculated angle value and the actual value, the embodiment of the present application also provides a method for using the data of the central three-axis Hall sensor to correct the interference in the four peripheral linear Hall sensors, and finally obtain the angle S of the target magnetic field in the horizontal plane (XY plane).

[0077] Specifically, let the target magnetic field (signal) be S(SB x ,SB y ,SB z ), external magnetic field interference (uniform interference) is E(EB x ,EB y ,EB z The three-axis Hall sensor in the center measures the three-axis magnetic field simultaneously, and the reading obtained is B x =SB x +EB x ,B y =SB y +EB y ,B z =SBz +EB z Since the magnet used in the target magnetic field is a two-pole magnet, it is basically parallel to the horizontal plane at the center of the three-axis Hall sensor (theoretically, it is absolutely parallel to the horizontal plane). Therefore, it can be assumed that , then the Z-axis component of the three-axis Hall sensor in the center is approximately The four peripheral linear Hall sensors only measure the magnetic field in the Z-axis direction, and their measured values ​​are recorded as B zi =SB zi +EB zi , i = 1, 2, 3, 4. Using the symmetry of the sensor position, the measured value at each peripheral linear Hall sensor can be written as ,in, is the amplitude of the signal in the horizontal plane, θ is the true angle of the target magnetic field in the horizontal plane, is the theoretical arrangement angle of the i-th linear Hall sensor (for example: ), k i is the gain factor of the i-th linear Hall sensor (determined by the geometric structure and sensitivity of the linear Hall sensor, which may vary between different linear Hall sensors). At the same time, it can be considered that on the z-axis, the contribution of the external interference magnetic field to the z-axis measurement values ​​of the four peripheral linear Hall sensors and the contribution to the z-axis measurement value of the central three-axis Hall sensor have a proportional difference, which is recorded as , where a i It is called the proportional coefficient of the response of the i-th peripheral linear Hall sensor to the z-axis component of the external interference magnetic field. In summary, the readings of the four peripheral linear Hall sensors can be written as .

[0078] It can be understood that in order to find the proportional coefficient a of each peripheral linear Hall sensor's response to the external magnetic field interference, i , the target magnetic field can be removed in the initial calibration stage (for example, in the absence of a target magnetic source, in a uniform external magnetic field). At this time, all Hall sensors are only affected by the external magnetic field interference. Therefore, the central three-axis Hall sensor measures B zcal =EB z , the four peripheral linear Hall sensors measure B zical =EB zi By the assumption , it can be deduced that , sorted out , that is, B obtained by calibration measurement zical and B zcal , the proportional coefficient a of each peripheral sensor can be calculated i , which reflects the proportional relationship between its response to external magnetic field interference and the response of the three-axis Hall sensor in the center to external magnetic field interference.

[0079] In actual measurement, the B measured by the three-axis Hall sensor in the center z ≈EB z Therefore, the reading of the peripheral sensor is, and the interference correction is performed on the data of the four peripheral linear Hall sensors, that is, the influence of the interference field (ie, the external magnetic field) is removed. The corrected value is defined as, and after substituting it into ; Since the proportional coefficient a of each peripheral sensor is calculated through initial calibration i After the initial calibration, the residual error caused by the non-uniformity between the linear Hall sensors can be reduced. Therefore, to simplify the subsequent derivation, it can be assumed that all peripheral linear Hall sensors have the same gain after the initial calibration, that is, k i =k(constant), then .

[0080] Taking advantage of the symmetry of peripheral sensors at ideal arrangement angles, the discussion can be divided into two groups.

[0081] 1. For the linear Hall sensor in the 0° and 180° directions, take and ,but , , define the difference as .

[0082] 2. For the linear Hall sensors in the 90° and 270° directions, take and ,but , , define the difference as .

[0083] According to the above difference results, we have , so we can get .

[0084] Those skilled in the art will clearly understand that for the sake of convenience and brevity, the division of the above-mentioned functional modules is only used as an example for illustration. In actual applications, the above-mentioned functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above. The specific working processes of the above-mentioned systems, devices and units can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0085] In the several embodiments provided in this application, it should be understood that the disclosed systems, devices, and methods can be implemented in other ways. If the integrated unit is implemented in the form of a software functional unit and sold or used as a separate product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application is essentially or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of a software product, which is stored in a storage medium and includes a number of instructions for enabling a computer device or processor to perform all or part of the steps of the method described in each embodiment of the present application.

[0086] The above embodiments are merely intended to provide a detailed description of the technical solutions of the present application. The descriptions of the above embodiments are intended only to aid understanding of the methods and core concepts of the present application and should not be construed as limiting the present application. Any changes or substitutions that can be readily conceived by a person skilled in the art within the technical scope disclosed in the present application should fall within the scope of protection of the present application.

Claims

1. A magnetic field immune system, wherein a target magnetic field S to be detected is set outside, and the target magnetic field S is a close-range dipole magnetic source, wherein: The center of the radial dipole magnet or dipole magnetic ring is located on the Z axis, so that the magnetic field components of the target magnetic field S along the Z axis at any two positions symmetrical about the origin on the plane where the X axis and the Y axis are located are equal in magnitude and opposite in direction, and the characteristics include: Three-axis magnetic sensor for measuring the X-axis, Y-axis and Z-axis magnetic field components B x 、B y and B z , wherein a spatial rectangular coordinate system is established with the three-axis magnetic sensor as the origin, and the straight line where the three-axis magnetic sensor and the target magnetic field S are located is the Z axis; Two single-axis magnetic sensors for measuring the Z-axis magnetic field component B z , arranged at a symmetrical position with the three-axis magnetic sensor as a symmetrical point, wherein the two single-axis magnetic sensors and the three-axis magnetic sensor are located in the same plane, which is the plane in which the X-axis and the Y-axis are located, and the Z-axis is perpendicular to the plane.

2. The magnetic field immune system according to claim 1, wherein: It also includes two other single-axis magnetic sensors, which are distributed around the three-axis magnetic sensor at equal distances and angles on the plane where the X-axis and the Y-axis are located, forming two groups of single-axis magnetic sensors set in symmetrical positions.

3. The magnetic field immune system according to claim 2, wherein: The magnetic field component EB of the external magnetic field on the Z axis is obtained according to the measurement values ​​of one or two groups of the single-axis magnetic sensor groups. z , and use EB z Correct the measurement value of the three-axis magnetic sensor to obtain the Z-axis magnetic field component SB of the target magnetic field at the three-axis magnetic sensor z .

4. The magnetic field immune system according to claim 2, wherein: According to the measurement value of one of the uniaxial magnetic sensor groups and the X-axis proportional coefficient k x , obtain the magnetic field component EB of the external magnetic field on the X axis x , according to the measurement value of the other group of uniaxial magnetic sensors and the Y-axis proportional coefficient k y , obtain the magnetic field component EB of the external magnetic field on the Y axis y , and use EB x , EB y Correct the measurement value of the three-axis magnetic sensor to obtain the X-axis and Y-axis magnetic field components SB of the target magnetic field at the three-axis magnetic sensor x and SB y .

5. The magnetic field immune system according to claim 4, characterized in that: in: The magnetic field component EB of the external magnetic field on the X axis x The result is obtained by adding the measured values ​​of one of the uniaxial magnetic sensor groups and multiplying the sum by the X-axis proportional coefficient k. x ; The magnetic field component SB of the target magnetic field on the X axis x The magnetic field component EB of the external magnetic field on the X axis is obtained by subtracting the measured value of the three-axis magnetic sensor on the X axis from the magnetic field component EB of the external magnetic field on the X axis. x ; The magnetic field component EB of the external magnetic field on the Y axis y The result is obtained by adding the measured values ​​of the other group of the single-axis magnetic sensor groups and multiplying them by the Y-axis proportional coefficient k. y ; The magnetic field component SB of the target magnetic field on the Y axis y The magnetic field component EB of the external magnetic field on the Y axis is obtained by subtracting the measured value of the three-axis magnetic sensor on the Y axis from the magnetic field component EB of the external magnetic field on the Y axis. y .

6. The magnetic field immune system according to claim 5, characterized in that: The X-axis scale factor k x The calculation steps include: Obtain the initial external magnetic field bias value EB of the X-axis of the three-axis magnetic sensor x[0] ; Obtain the initial measurement value B of one of the uniaxial magnetic sensor groups z1[0] and B z3[0] ; The initial measurement value B of one of the uniaxial magnetic sensor groups is z1[0] and B z3[0] The sum is then divided by the initial external magnetic field bias value EB of the X axis of the three-axis magnetic sensor x[0] , that is, to obtain the X-axis scale coefficient k x .

7. The magnetic field immune system according to claim 6, wherein: The Y-axis scale factor k y The calculation steps include: Obtain the initial external magnetic field bias value EB of the Y axis of the three-axis magnetic sensor y[0] ; Obtain the initial measurement value B of the other group of the uniaxial magnetic sensor group z2[0] and B z4[0] ; The initial measurement value B of the other group of the uniaxial magnetic sensor group is z2[0] and B z4[0] The sum is then divided by the initial external magnetic field bias value EB of the Y axis of the three-axis magnetic sensor y[0] , that is, to obtain the Y-axis scale coefficient k y .

8. The magnetic field immune system according to claim 6 or 7, characterized in that: When the external magnetic field strength changes slowly, the initial measurement values ​​B of the two groups of single-axis magnetic sensors are dynamically adjusted. z1[0] ,B z2[0] ,B z3[0] and B z4[0] , according to the X-axis scale factor k x and Y-axis scale factor k y , update the initial external magnetic field bias values ​​EB of the X-axis and Y-axis of the three-axis magnetic sensor x[0] and EB y[0] .

9. The magnetic field immune system according to claim 2, wherein: The angles of the target magnetic field in the X-axis and Y-axis planes can be calculated by subtracting the difference Δx from the measurement values ​​of one group of the single-axis magnetic sensor groups and subtracting the difference Δy from the measurement values ​​of the other group of the single-axis magnetic sensor groups. .

10. The magnetic field immune system according to claim 2, wherein: Correcting the measurement values ​​of the four single-axis magnetic sensors according to the data of the three-axis magnetic sensor, and obtaining the angles of the target magnetic field in the X-axis and Y-axis planes, specifically including: Assume the target magnetic field is S(SB x ,SB y ,SB z ), the external magnetic field is E(EB x ,EB y ,EB z ), the three-axis magnetic sensor measures the three-axis magnetic field simultaneously, and the reading obtained is B x =SB x +EB x ,B y =SB y +EB y ,B z =SB z +EB z ; Assume that the target magnetic field is mainly concentrated in the horizontal plane, that is , then the Z-axis component of the three-axis magnetic sensor is ; The four single-axis magnetic sensors only measure the magnetic field in the Z-axis direction, and their measured values ​​are recorded as , i=1, 2, 3, 4, the measured value at each single-axis magnetic sensor can be written as ,in, is the amplitude of the signal in the X-axis and Y-axis planes, θ is the true angle of the target magnetic field in the horizontal plane, is the theoretical arrangement angle of the i-th uniaxial magnetic sensor, where , , , , k i is the gain factor of the i-th single-axis magnetic sensor. At the same time, the contribution of the external magnetic field interference to the four single-axis magnetic sensors is proportionally different from that of the central three-axis magnetic sensor, which is recorded as , where a i is the proportional coefficient of the response of the i-th uniaxial magnetic sensor on the periphery to the external magnetic field interference; In summary, the readings of the four uniaxial magnetic sensors can be written as ; Interference correction is performed on the four single-axis magnetic sensor data, and the corrected value is defined as , after substituting into ; Assume that all peripheral single-axis magnetic sensors have the same gain after initial calibration, that is, k i =k, where k is a constant, then ; By utilizing the symmetry of the two groups of single-axis magnetic sensors, the two groups of single-axis magnetic sensors are differentiated to obtain: , ; Then there is , so we can get .

11. The magnetic field immune system according to claim 10, wherein: The proportional coefficient a of the response of the i-th uniaxial magnetic sensor to external magnetic field interference i The evaluation steps include: In the initial calibration phase, the target magnetic field is set to zero; The three-axis magnetic sensor measures B zcal =EB z , four uniaxial magnetic sensors measure B zical =EB zi ; Assume EB zi =a i ·EB z ; It can be deduced that B zical =a i ·B zcal , sorted out .

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