Magnetic field immune system

Abstract

The invention relates to the field of magnetic field detection, in particular to a magnetic field immune system which is externally provided with a to-be-detected target magnetic field S. The magnetic field immune system comprises a three-axis magnetic sensor used for measuring X-axis, Y-axis and Z-axis magnetic field components Bx, By and Bz, a space rectangular coordinate system is established by taking the three-axis magnetic sensor as an original point, and the three-axis magnetic sensor is used for measuring X-axis, Y-axis and Z-axis magnetic field components Bx, By and Bz; the straight line where the three-axis magnetic sensor and the target magnetic field S are located is the Z axis; the two single-axis magnetic sensors are used for measuring a Z-axis magnetic field component Bz and are arranged at symmetrical positions with the three-axis magnetic sensor as a symmetrical point, the two single-axis magnetic sensors and the three-axis magnetic sensor are located on the same plane, the plane is a plane where the X axis and the Y axis are located together, and the Z axis is perpendicular to the plane. The layout design of the invention is helpful for detecting and correcting the tilt error of the magnetic field, and ensures that the magnetic field measurement on the XY plane is more accurate.

Description

Technical Field

[0001] This application relates to the field of magnetic field detection, and particularly to a magnetic field immune system. Background Art

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

[0003] Currently, the technologies on the market usually involve a larger combination arrangement of sensors, or mainly aim to increase the detection coverage, or use more sensors to improve the detection accuracy. As is known to those skilled in the art, using more sensors will involve more calculations, increase the complexity of the algorithm and the system, be more prone to failures, and also need to ensure the consistency between multiple sensors. Otherwise, it is easy to introduce non-uniform errors between sensors, further increasing the complexity of the system. Summary of the Invention

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

[0005] This application provides a magnetic field immune system, adopting the following technical solution: A magnetic field immune system, with a target magnetic field S to be detected externally, includes: a three-axis magnetic sensor for measuring the magnetic field components B x 、B y and B z on the X, Y, and Z axes. 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 magnetic field component B z on the Z axis, arranged at symmetric positions with the three-axis magnetic sensor as the symmetric point. Among them, the two single-axis magnetic sensors and the three-axis magnetic sensor are in the same plane, and this plane is the plane where the X axis and the Y axis are both located, and the Z axis is perpendicular to this plane.

[0006] A further solution is that it further includes another two single-axis magnetic sensors. The four single-axis magnetic sensors are evenly distributed at equal angles around the three-axis magnetic sensor in the X-axis and Y-axis plane, forming two groups of single-axis magnetic sensor groups arranged at symmetric positions.

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

[0008] A further solution is to obtain the magnetic field component EB of the external magnetic field on the X-axis according to the measurement values of one of the groups of the uniaxial magnetic sensor groups and the X-axis proportionality coefficient k x , and obtain the magnetic field component EB of the external magnetic field on the Y-axis according to the measurement values of the other group of the uniaxial magnetic sensor groups and the Y-axis proportionality coefficient k x , and use EB y , EB y to correct the measurement values of the triaxial magnetic sensor, so as to obtain the magnetic field components SB of the target magnetic field on the X-axis and Y-axis at the triaxial magnetic sensor x and SB y . x and SB y .

[0009] A further solution is that: the magnetic field component EB of the external magnetic field on the X-axis x is obtained by the following method: adding the measurement values of the one group of the uniaxial magnetic sensor groups and then multiplying by the X-axis proportionality coefficient k x ; the magnetic field component SB of the target magnetic field on the X-axis x is obtained by the following method: subtracting the magnetic field component EB of the external magnetic field on the X-axis from the measurement value of the triaxial magnetic sensor on the X-axis x ; the magnetic field component EB of the external magnetic field on the Y-axis y is obtained by the following method: adding the measurement values of the other group of the uniaxial magnetic sensor groups and then multiplying by the Y-axis proportionality coefficient k y ; the magnetic field component SB of the target magnetic field on the Y-axis y is obtained by the following method: subtracting the magnetic field component EB of the external magnetic field on the Y-axis from the measurement value of the triaxial magnetic sensor on the Y-axis y .

[0010] A further solution is that the calculation steps of the X-axis proportionality coefficient k x include: obtaining the initial external magnetic field bias value EB of the X-axis of the triaxial magnetic sensor x[0] ; obtaining the initial measurement values B z1[0] and B z3[0] of the one group of the uniaxial magnetic sensor groups; adding the initial measurement values B z1[0] and B z3[0] of the one group of the uniaxial magnetic sensor groups and then dividing by the initial external magnetic field bias value EB of the X-axis of the triaxial magnetic sensor x[0] , and thus obtaining the X-axis proportionality coefficient k x .

[0011] A further solution is that the Y-axis proportionality coefficient k yThe calculation steps include: obtaining the initial external magnetic field bias value EB of the Y-axis of the triaxial magnetic sensor y[0] ; obtaining the initial measurement values B z2[0] and B z4[0] of the other group of the single-axis magnetic sensor groups z2[0] ; adding the initial measurement values B z4[0] and B y[0] of the other group of the single-axis magnetic sensor groups and dividing the sum by the initial external magnetic field bias value EB of the Y-axis of the triaxial magnetic sensor y . That is, the Y-axis proportionality coefficient k

[0012] is obtained z1[0] . Further, when the external magnetic field strength changes slowly, the initial measurement values B z2[0] , B z3[0] , B z4[0] and B x of the two groups of the single-axis magnetic sensor groups are dynamically adjusted. According to the X-axis proportionality coefficient k y and the Y-axis proportionality coefficient k x[0] , the initial external magnetic field bias values EB y[0] of the X-axis and Y-axis of the triaxial magnetic sensor are linearly updated

[0013] . Further, the difference component Δx is obtained by subtracting the measurement values of one group of the single-axis magnetic sensor groups, and the difference component Δy is obtained by subtracting the measurement values of the other group of the single-axis magnetic sensor groups. Then, the angle of the target magnetic field in the X-axis and Y-axis plane can be calculated .

[0014] . Further, the interference in the four single-axis magnetic sensors is corrected according to the data of the triaxial magnetic sensor, and the angle of the target magnetic field in the X-axis and Y-axis plane is obtained. Specifically, it includes: 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 triaxial magnetic sensor measures the triaxial magnetic field simultaneously, and the readings obtained are B x = SB x + EB x , B y = SB y + EB y , B z = SB z + EB z ; assuming that the target magnetic field is mainly concentrated in the horizontal plane, that is , then the Z-axis component of the triaxial magnetic sensor ; The four uniaxial magnetic sensors only measure the magnetic field in the Z-axis direction, and their measured values are denoted as , i = 1, 2, 3, 4. The measured value at each uniaxial magnetic sensor can be written as , where is the amplitude of the signal in the X-axis and Y-axis plane, θ is the true angle of the target magnetic field in the horizontal plane, is the theoretical layout angle of the i-th uniaxial magnetic sensor, where , , , , k i is the gain factor of the i-th uniaxial magnetic sensor. At the same time, there is a proportional difference in the contribution of the external magnetic field interference to the four uniaxial magnetic sensors and the central triaxial magnetic sensor, denoted as , where a i is the proportional coefficient of the i-th uniaxial magnetic sensor on the periphery to the external magnetic field interference response; In summary, the readings of the four uniaxial magnetic sensors can be written as ; For the interference correction of the data of the four uniaxial magnetic sensors, the corrected value is defined as , and substituting it in gives ; Assume that after the initial calibration, all the uniaxial magnetic sensors on the periphery have the same gain, that is, k i = k, where k is a constant, then ; Using the symmetry of the two groups of uniaxial magnetic sensor groups, the differences are obtained for the two groups of uniaxial magnetic sensor groups respectively: , ; Then there is , so can be obtained.

[0015] A further solution is that the evaluation steps of the proportional coefficient a i of the i-th uniaxial magnetic sensor's response to the external magnetic field interference include: setting the target magnetic field to zero in the initial calibration stage; the triaxial magnetic sensor measures to obtain B zcal = EB z , and the four uniaxial magnetic sensors measure to obtain B zical = EB zi ; Assume EB zi = a i · EB z ; It can be deduced that B zical = a i · B zcal , and after sorting, we get .

[0016] In summary, the layout design of the present application helps to detect and correct the tilt error of the magnetic field, ensuring more accurate magnetic field measurement on the XY plane. The uniqueness of this layout lies in that, while maintaining a simple layout, it can eliminate or reduce the influence of magnetic field tilt on measurement through the fusion of the outputs of the single-axis magnetic sensors around the perimeter. Description of the Drawings

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

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

[0019] Figure 3 This is the sensor layout design diagram of another embodiment of the present application. Detailed Embodiments

[0020] It should be noted that the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features.

[0021] The embodiments of the present application will be described below in conjunction with the drawings of the specification, but these embodiments should not be construed as limiting the present application.

[0022] As Figure 1 and Figure 2 shown, an embodiment of the present application provides a magnetic field immune system, with a target magnetic field S to be detected externally provided. The system includes a central sensor (a three-axis magnetic sensor) and two peripheral sensors (single-axis magnetic sensors). Figure 1 Shown are the magnetic field line diagrams of the target magnetic field (magnet), as well as the magnetic field line diagrams of the positions of the respective sensors and the diagrams of the magnetic field intensities sensed by the respective sensors. Figure 1 The system layout is shown from the longitudinal section of the three-dimensional space. Figure 2 From Figure 1 the plane perpendicular to the plane shown, the system layout is shown. In Figure 2 , the two peripheral sensors are marked with special symbols to indicate the magnetic field directions they measure.

[0023] A spatial rectangular coordinate system is established with the central sensor as the origin. Among them, the two peripheral sensors and the central sensor are arranged on the same straight line, with this straight line as the X-axis. The target magnetic field S is arranged outside this straight line, and the straight line where the target magnetic field S and the central sensor are located is perpendicular to the X-axis, with this straight line as the Z-axis. Another straight line perpendicular to both the X-axis and the Z-axis is made, with this straight line as the Y-axis; the plane where the X-axis and the Y-axis are located is the XY plane, or the horizontal plane.

[0024] In this embodiment, the coordinates of the two peripheral sensors on the X-axis are B z1 (R, 0) and 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 central sensor (triaxial magnetic sensor) can be a sensor whose output electrical signal intensity is proportional to the magnitude of the sensed magnetic field intensity. For example, in the embodiments of the present application, a triaxial (3D) Hall sensor can be used, which can measure the triaxial magnetic field components B x , B y and B z on the X-axis, Y-axis, and Z-axis simultaneously. The measurement results include the superposition of 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 ; The two peripheral sensors (uniaxial magnetic sensors) can be sensors whose output electrical signal intensity is proportional to the magnitude of the sensed magnetic field intensity. For example, in the embodiments of the present application, linear Hall sensors that measure a single direction component (for example, only the magnetic field component in the Z-axis direction needs to be measured in this embodiment) can be used. A linear Hall sensor means that the output electrical signal intensity of the Hall sensor is proportional to the magnitude of the sensed magnetic field intensity. Moreover, the two peripheral sensors are arranged at symmetric positions with the triaxial Hall sensor as the symmetry 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 including the superposition of the target magnetic field S and the external magnetic field E. The measured values are respectively denoted as B z1 = SB z1 + EB z1 and B z3 = SB z3 + EB z3 .

[0026] The target magnetic field S is a short-range dipole magnetic source, including a magnetic ring, a disc-shaped magnet, and a strip-shaped magnet. Among them, the center of the radial secondary magnet or secondary magnetic ring is located on the Z-axis, so that the magnitudes of the Z-axis magnetic field components at two positions on the XY plane that are symmetric about the origin are equal and the directions are opposite.

[0027] The external magnetic field E comes from a magnetic source at a long distance, and its direction is approximately fixed. It irradiates the entire sensor array like "parallel light". 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 non-uniformly changing part of the external magnetic field E in space.

[0028] To obtain a pure target magnetic field value, it is necessary to eliminate the influence of the external magnetic field E (EB x , B y , B z ) from B x , EB y , EB z . In this application, through a symmetric layout design, the contributions of the target magnetic field S can cancel each other out in the z-axis components of the peripheral sensors, leaving the main external magnetic field E information.

[0029] Specifically, for two peripheral sensors B z1 and B z3 at two symmetric positions on the X-axis, 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 are arranged at symmetric positions of the target magnetic field S, the magnitudes of the Z-axis components of the target magnetic field S at these two points are equal and the directions are opposite, that is, SB z1 = -SB z3 .

[0030] Therefore, adding the measured values of these two peripheral sensors B z1 and B z3 gives: B z1 + B z3 = (SB z1 + SB z3 ) + (EB z1 + EB z3 ) = EB z1 + EB z3 ; only considering the uniformly changing part of the external magnetic field E in space, it can be known that EB z1 + EB z3 ≈ 2EB z , so it can be deduced that: B z1 + B z3 = 2EB z .

[0031] Furthermore, it can be obtained that EB z = (Bz1 +B z3 ) / 2, that is, the Z-axis component of the external magnetic field E is half of the sum of the measured values of the peripheral sensors B z1 and B z3 This indicates that by adding the measured values of the sensors B z1 and B z3 at symmetric positions, the Z-axis component of the target magnetic field S is cancelled out, leaving only the contribution of the external magnetic field E. After obtaining the Z-axis component value EB z of the external magnetic field E at the central sensor, the pure target magnetic field value SB z on the Z-axis at the central sensor can be obtained through the formula SB z =B z -EB z That is, it can be obtained.

[0032] 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. For the specific calculation process, reference can be made to the calculation process using four peripheral sensors in the next embodiment.

[0033] As Figure 1 and Figure 3 shown, another embodiment of the present application provides a magnetic field immune system, including a central sensor (a three-axis magnetic sensor) and four peripheral sensors (single-axis magnetic sensors). Since Figure 1 the system layout is shown from the longitudinal section of the three-dimensional space, the two additional peripheral sensors are not visible in Figure 1 . Figure 3 Shown from the plane perpendicular to the plane shown in Figure 1 . In Figure 3 , the four peripheral sensors are marked with special symbols to indicate the magnetic field directions they measure.

[0034] Establish a spatial rectangular coordinate system with the central sensor as the origin. Among them, two peripheral sensors (such as B z1 and B z3 ) and the central sensor are arranged on the same straight line. Take this 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, the other straight line is taken as the Y axis, the plane where the X axis and the Y axis are located is the XY plane, or the horizontal plane, 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, and the straight line is taken as 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 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 single-direction components (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 a superposition of the target magnetic field S and the external magnetic field E, and 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 central sensor and the peripheral sensors.

[0035] To obtain a pure target magnetic field value, it is necessary to eliminate the influence of the external magnetic field E (EB x , B y , B z ) from the measured values B x , EB y , EB z of the triaxial sensor. In this application, through a symmetric layout design, the contributions of the target magnetic field S can cancel each other out in the z-axis component of the peripheral sensors, leaving the main external magnetic field E information.

[0036] Specifically, for the two peripheral sensors B z1 and B z3 at two symmetric positions on the X-axis, 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 are arranged at symmetric positions of the target magnetic field S, the magnitudes of the z-axis components of the target magnetic field S at these two points are equal and the directions are opposite, that is, SB z1 = -SB z3 . Therefore, adding the measured values of these two peripheral sensors B z1 and B z3 gives: B z1 + B z3 = (SB z1 + SB z3 ) + (EB z1 + EB z3 ) = EB z1 + EB z3 ; and from the characteristic of the uniform change of the external magnetic field E, it can be deduced that: B z1 + B z3 = 2EB z , and further it can be obtained that EB z = (B z1 + B z3 ) / 2, that is, the z-axis component of the external magnetic field E is half of the sum of the measured values of the peripheral sensors B z1 and B z3 . This shows that by adding the measured values of the sensors B z1 and B z3 at symmetric positions, the z-axis component of the target magnetic field S is completely canceled out, leaving only the contribution of the external magnetic field E.

[0037] Similarly, for the outer peripheral sensors B at two symmetric positions on the Y-axis z2 and B z4 , the measured values are respectively: B z2 =SB z2 +EB z2 , B z4 =SB z4 +EB z4 . Since these two outer peripheral sensors B z2 and B z4 are arranged at symmetric positions of the target magnetic field S, such that the magnitudes of the Z-axis components of the target magnetic field S at these two points are equal and the directions are opposite, i.e., SB z2 =-SB z4 , therefore, adding the measured values of these two outer peripheral sensors B z2 and B z4 gives: B z2 +B z4 = (SB z2 +SB z4 ) + (EB z2 +EB z4 ) = 0 + EB z2 +EB z4 ; and from the characteristic of the uniform distribution of the external magnetic field E, it is known that EB z2 ≈EB z4 ≈EB z , therefore, it can be deduced that: B z2 +B z4 =2EB z , and further it can be obtained that EB z = (B z2 +B z4 ) / 2, that is, the Z-axis component of the external magnetic field E is half of the sum of the measured values of the outer peripheral sensors B z2 and B z4 . This shows that by adding the measured values of the sensors B z2 and B z4 at symmetric positions, the Z-axis component of the target magnetic field S is completely cancelled out, and only the contribution of the external magnetic field E remains.

[0038] It can be understood that the Z-axis component of the external magnetic field E can also be one-fourth of the sum of the measured values of the outer peripheral sensors B z1 , B z2 , B z3 and B z4 . Calculating the Z-axis component of the external magnetic field E using the sum of the measured values of 4 outer peripheral sensors will reduce the influence of the non-uniformity of the outer peripheral sensors. After obtaining the component value EB z of the external magnetic field E on the Z-axis, then the pure target magnetic field value SB z on the Z-axis is obtained through the formula SB z =Bz -EB z Can be obtained

[0039] 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.

[0040] 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 proportionality coefficient of the external magnetic field E in the X-axis and Z directions, simply referred to as the X-axis proportionality coefficient, k y is the proportionality coefficient of the external magnetic field E in the Y and Z directions, simply referred to as the Y-axis proportionality coefficient, (B z1 +B z3 ) is the result of the sum of the peripheral sensors B z1 and B z3 , representing the change of the external magnetic field E in the Z-axis direction, (B z2 +B z4 ) is the result of the sum of the peripheral sensors B z2 and B z4 , representing the change of the external magnetic field E in the Z-axis direction; k x and k y are determined through initial calibration (the initial calibration process is described in detail below), and this fixed proportional relationship can be used in subsequent measurements to achieve dynamic updates of EB x and EB y .

[0041] Specifically, the target magnetic field values SB x and SB y on the X-axis and Y-axis can be obtained through the following steps.

[0042] First, perform initial calibration.

[0043] Specifically, in an environment where there is no target magnetic field S and only the external magnetic field E has an impact, record the initial measurement values B z1[0] , B z2[0] , B z3[0] , B z4[0] of the four peripheral sensors, as well as the initial measurement values EB x[0] , EB y[0](Since it is only the initial measured 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] refer to the external magnetic field bias value at time 0). Calculate the X-axis proportionality coefficient and the Y-axis proportionality coefficient through these values, as shown in the following equations (1) and (2): k x =EB x[0] / (B z1[0] +B z3[0] ) (1) k y =EB y[0] / (B z2[0] +B z4[0] ) (2) Secondly, calculate the external magnetic field bias value at any time t in real time.

[0044] Specifically, at any time t, read the measured values B z1[t] , B z2[t] , B z3[t] , B z4[t] of the four peripheral sensors, and calculate the current external magnetic field bias values EB x[t] and EBy [t] at time t: (3) (4) Substitute (1) and (2) into (3) and (4) respectively, and get: , .

[0045] Finally, perform bias compensation on the central sensor.

[0046] Specifically, introduce the target magnetic field S. According to the measured values B x[t] , B y[t] , B z[t] of the central sensor at time t, deduct the external magnetic field bias value through the following formula to obtain the pure target magnetic field values SB x and SB y on the X-axis and Y-axis: .

[0047] It can be understood that when the magnetic field intensity of the external magnetic field E changes slowly, since the direction of the external magnetic field E remains unchanged and the output value of the three-axis Hall sensor changes linearly with the magnitude of the external magnetic field E, therefore, the initial values B z1[0] , B z2[0] , B z3[0] , Bz4[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 k x and k y unchanged, and the 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).

[0048] Through the above derivation, the addition of the measured 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.

[0049] 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 a table or approximating the tangent.

[0050] Adopt the sensor arrangement method of this embodiment, that is: use a central three-axis Hall sensor to measure the magnetic field in the X, Y, and Z axis directions, and arrange four linear Hall sensors at four 90-degree directions with equal radii around it to measure the Z-axis component of the magnetic field. Such a layout design helps to detect and correct the tilt error of the magnetic field, ensuring more accurate magnetic field measurement on the XY plane; the uniqueness of this layout lies in that it can eliminate or reduce the influence of magnetic field tilt on measurement by fusing the outputs of the surrounding linear Hall sensors while keeping the layout simple. Moreover, this application clarifies that there are exactly four linear Hall sensors around the central three-axis Hall sensor. This choice of quantity not only ensures the detection accuracy but also simplifies the system complexity. The 90-degree symmetric layout of the four linear Hall sensors enables the gradient change of the magnetic field to be obtained through simple calculations without increasing the number of additional sensors. The magnetic field detection methods in the prior art may use more sensors to improve accuracy, and as is known to those skilled in the art, more sensors involve more calculations and the consistency between multiple sensors also needs to be ensured. This application only requires four linear Hall sensors, which can logically avoid or reduce these disadvantages.

[0051] It can be understood that when adopting the sensor arrangement method of this embodiment, the distances of the two pairs of surrounding linear Hall sensors from the center point can be different, but the distances of the two linear Hall sensors in the same pair from the center point are equal. In addition, three pairs or four pairs of linear Hall sensors can also be arranged around. The more peripheral sensors there are, the lower the error caused by the non-uniformity in the production of the sensors can be reduced.

[0052] In the above embodiment, the non-uniformity in the production of the peripheral sensors is likely to have a certain impact on the measurement. Next, another embodiment will be introduced, where the measurement value of the central sensor can be used to correct the non-uniformity of the peripheral sensors.

[0053] As Figure 3 shown, in this embodiment, the Z-axis data collected by the four surrounding linear Hall sensors (specific implementation of the single-axis magnetic sensor) is used to measure the signal angle. Among them, the four peripheral linear Hall sensors are respectively located in the 0°, 90°, 180°, and 270° directions. 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.

[0054] In an ideal situation where there is no external magnetic field interference or the external magnetic field interference is negligible, it can be denoted as , where , is the amplitude of the target magnetic field S in the XY plane (which can be regarded as the magnitude of the "horizontal component"); θ is the direction angle of the target magnetic field S in the XY plane (i.e., the relative rotation angle between the magnet and the sensor), is the arrangement angle of the linear Hall sensor i (for example, the arrangement angles of the 1st, 2nd, 3rd, and 4th linear Hall sensors are 0°, 90°, 180°, and 270° in sequence); 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, it is considered that their k values are the same (the proportionality coefficient for converting the magnetic field component in the plane into the output of the sensor's Z axis).

[0055] If there is external magnetic field interference, then , if the external magnetic field is approximately equal at the four linear Hall sensors, it can be denoted as EB zi ≈EB z .

[0056] For sensors in symmetric positions (0° and 180°, 90° and 270°), differential operations can be performed respectively to eliminate (or weaken) certain symmetric components and highlight the orthogonal components of the target magnetic field S.

[0057] Specifically, for the differential operation in the 0° and 180° directions: , if the external magnetic field can be ignored, then , so there is .

[0058] Similarly, for the differential operation in the 90° and 270° directions: , if the external magnetic field can be ignored, then , , so there is .

[0059] That is , from which the angle of the target magnetic field S in the XY plane can be estimated .

[0060] When there is a long-distance and approximately fixed-direction parallel external magnetic field E, assuming that the contribution of the external magnetic field E in the Z-axis direction 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 truly exactly the same at the four linear Hall sensors, it will cancel each other out in the difference. However, if there is non-uniformity between the individual linear Hall sensors, residual errors will be introduced.

[0061] Denote , .

[0062] After substituting the external magnetic field terms, we get: , .

[0063] 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 ), then the external magnetic field components in the difference will be completely cancelled out, and the angle calculation remains .

[0064] However, in actual situations, there are often slight differences among the four linear Hall sensors, resulting in or . This will leave residual interference in Δx or Δy, thus making tanθ 计算 ≠tanθ. In other words, there will be a certain deviation in the angle calculation, and its magnitude depends on the degree of non-uniformity of the external magnetic field interference between each pair of linear Hall sensors.

[0065] To reduce the deviation between the calculated value and the actual value of the angle, 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 of the target magnetic field S in the horizontal plane (XY plane).

[0066] Specifically, let the target magnetic field (signal) be S(SB x , SB y , SB z ), and the external magnetic field interference (uniform interference) be E(EB x , EB y , EB z ). The central three-axis Hall sensor measures the three-axis magnetic field simultaneously, and the readings obtained are B x =SB x +EB x , B y =SB y +EB y , B z =SB z +EB zSince the magnet used for the target magnetic field is a two-pole magnet, it is basically parallel to the horizontal plane (theoretically absolutely parallel to the horizontal plane) at the central position where the three-axis Hall sensor is located. Therefore, it can be assumed that , the Z-axis component of the central three-axis Hall sensor is approximately . The four peripheral linear Hall sensors only measure the magnetic field in the Z-axis direction, and their measured values are denoted as B zi =SB zi +EB zi , i = 1, 2, 3, 4. Utilizing the symmetry of the sensor positions, the measured value at each peripheral linear Hall sensor can be written as , where 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 layout angle of the i-th linear Hall sensor (for example: ), and 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, and there may be differences 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 measured values of the four peripheral linear Hall sensors and the contribution to the z-axis measured value of the central three-axis Hall sensor have a proportional difference, denoted as , where a i is called the proportionality coefficient of the i-th peripheral linear Hall sensor's response 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 .

[0067] It can be understood that to obtain the proportionality coefficient a i of each peripheral linear Hall sensor's response to the external magnetic field interference, the target magnetic field can be removed during the initial calibration stage (for example, in a uniform external magnetic field without a target magnetic source). 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 , and the four peripheral linear Hall sensors measure B zical =EB zi . From the assumption , it can be deduced that , and after rearrangement, it can be obtained that , that is: by calibrating and measuring B zical and B zcal , the proportionality coefficient a i of each peripheral sensor can be calculated, which reflects the proportional relationship between its response to the external magnetic field interference and the response of the central three-axis Hall sensor to the external magnetic field interference.

[0068] During actual measurement, the B measured by the triaxial Hall sensor at the center z ≈EB z , therefore, the readings of the peripheral sensors are obtained by performing interference correction on the data of the four linear Hall sensors on the periphery, that is, removing the influence of the interference field (i.e., the external magnetic field), and defining the corrected value as. After substitution, we get ; Since the proportionality coefficient a of each peripheral sensor is calculated through initial calibration i , the residual error introduced due to the non-uniformity between the linear Hall sensors can be reduced. Therefore, for the sake of simplifying the subsequent derivation, it can be assumed that all the linear Hall sensors on the periphery have the same gain, that is, k i =k (constant), then .

[0069] Using the symmetry of the peripheral sensors at the ideal arrangement angles, it can be divided into two groups for discussion.

[0070] 1. For the linear Hall sensors in the 0° and 180° directions, take and , then , , and define the difference as .

[0071] 2. For the linear Hall sensors in the 90° and 270° directions, take and , then , , and define the difference as .

[0072] From the above difference results, we have , and thus can obtain .

[0073] Those skilled in the art can clearly understand that for the convenience and conciseness of description, only the above division of each functional module is used as an example. In actual applications, the above functions can be allocated to different functional modules according to needs, that is, the internal structure of the device is divided into different functional modules to complete all or part of the functions described above. The specific working processes of the system, device, and unit described above can refer to the corresponding processes in the foregoing method embodiments and will not be elaborated here.

[0074] In several embodiments provided by the present 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, in essence, or the part that contributes to the prior art, or all or part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device or a processor to execute all or part of the steps of the methods described in various embodiments of the present application.

[0075] The above embodiments are only used to introduce the technical solution of the present application in detail. However, the description of the above embodiments is only for helping to understand the method and its core idea of the present application, and should not be construed as a limitation of the present application. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application should be covered within the protection scope of the present application.

Claims

1. A magnetic field immune system, with a target magnetic field S to be detected set externally, characterized in that, Comprising: 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 for measuring the Z-axis magnetic field component B z , are arranged at symmetric positions with the triaxial magnetic sensor as the symmetric point. Among them, the two single-axis magnetic sensors and the triaxial magnetic sensor are located in the same plane, which is the plane where the X-axis and the Y-axis are both located, and the Z-axis is perpendicular to this plane.

2. The magnetic field immune system according to claim 1, wherein It further includes two other uniaxial magnetic sensors. The four uniaxial magnetic sensors are equidistantly and equally angularly distributed around the triaxial magnetic sensor in the plane where the X-axis and the Y-axis are located together, forming two groups of uniaxial magnetic sensor groups arranged at symmetric positions.

3. The magnetic field immune system according to claim 2, characterized in that, Obtain the magnetic field component EB of the external magnetic field in the Z-axis according to the measurement values of one or both of the groups of the uniaxial magnetic sensor groups z , and use EB z to correct the measurement values of the triaxial magnetic sensor, so as to obtain the Z-axis magnetic field component SB of the target magnetic field at the triaxial magnetic sensor z .

4. The magnetic field immune system according to claim 2, wherein According to the measured values of one set of the uniaxial magnetic sensor groups and the X-axis proportionality coefficient k x , the magnetic field component EB of the external magnetic field on the X-axis is obtained x , according to the measured values of the other set of the uniaxial magnetic sensor groups and the Y-axis proportionality coefficient k y , the magnetic field component EB of the external magnetic field on the Y-axis is obtained y , and EB x and EB y are used to correct the measured values of the triaxial magnetic sensor, so as to obtain the X-axis and Y-axis magnetic field components SB of the target magnetic field at the triaxial magnetic sensor x and SB y .

5. The magnetic field immune system according to claim 4, wherein Wherein: The magnetic field component EB of the external magnetic field in the X-axis x is obtained by adding the measurement values of one of the groups of the uniaxial magnetic sensor groups and multiplying the sum by the X-axis scale factor k x ; Magnetic field component SB of the target magnetic field in the X-axis x is obtained by subtracting the measured value of the triaxial magnetic sensor in the X-axis from the magnetic field component EB of the external magnetic field in the X-axis x ; The magnetic field component EB of the external magnetic field in the Y-axis y is obtained by adding the measured values of the other group of the uniaxial magnetic sensor groups and then multiplying by the Y-axis scale factor k y ; Magnetic field component SB of the target magnetic field in the Y-axis y is obtained by subtracting the measured value of the triaxial magnetic sensor in the Y-axis from the magnetic field component EB of the external magnetic field in the Y-axis y .

6. The magnetic field immune system according to claim 5, wherein 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 groups of the single-axis magnetic sensor groups z1[0] and B z3[0] ; Add the initial measurement values B of one of the groups of the uniaxial magnetic sensor groups z1[0] and B z3[0] , and then divide the sum by the initial external magnetic field bias value EB of the X-axis of the triaxial magnetic sensor x[0] , thus obtaining the X-axis proportionality coefficient k x .

7. The magnetic field immune system according to claim 6, characterized in that, The Y-axis proportionality coefficient 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 set of the single-axis magnetic sensor groups z2[0] and B z4[0] ; Add the initial measurement values B of the other group of the single-axis magnetic sensor groups, z2[0] and B z4[0] and divide the sum by the initial external magnetic field bias value EB of the Y-axis of the triaxial magnetic sensor, y[0] to obtain the Y-axis proportionality 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, dynamically adjust the initial measured values B of the two groups of the single-axis magnetic sensor groups z1[0] ,B z2[0] ,B z3[0] and B z4[0] , according to the X-axis scale factor k x and the 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 differential component Δx is obtained by subtracting the measured values of one of the groups of uniaxial magnetic sensor groups, and the differential component Δy is obtained by subtracting the measured values of the other group of uniaxial magnetic sensor groups, so that the angle of the target magnetic field in the plane of the X-axis and the Y-axis can be calculated .

10. The magnetic field immune system according to claim 2, characterized in that, Correct the measured values of the four uniaxial magnetic sensors according to the data of the triaxial magnetic sensor, and obtain the angle of the target magnetic field in the plane of the X-axis and the Y-axis. Specifically, it includes: Let the target magnetic field be S(SB x ,SB y ,SB z ), and the external magnetic field be E(EB x ,EB y ,EB z ). The triaxial magnetic sensor measures the triaxial magnetic fields simultaneously, and the readings obtained are 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 ; Four single-axis magnetic sensors only measure the magnetic field in the Z-axis direction, and their measured values are denoted as , i = 1, 2, 3, 4. The measured value at each single-axis magnetic sensor can be written as , where is the amplitude of the signal in the X-axis and Y-axis plane, θ is the true angle of the target magnetic field in the horizontal plane, is the theoretical layout angle of the i-th single-axis magnetic sensor, where , , , , k i is the gain factor of the i-th single-axis magnetic sensor. At the same time, there is a proportional difference in the contribution of external magnetic field interference to the four single-axis magnetic sensors and the central three-axis magnetic sensor, denoted as , where a i is the proportional coefficient of the i-th single-axis magnetic sensor on the periphery to the response of external magnetic field interference; In summary, the readings of the four single-axis magnetic sensors can be written as ; Interference correction is performed on the data of four single-axis magnetic sensors, and the corrected value is defined as , and after substitution, we get ; Assume that all the uniaxial magnetic sensors on the periphery have the same gain, namely k, after initial calibration. i = k, where k is a constant, then ; By utilizing the symmetry of two groups of single-axis magnetic sensor groups, differential operations are respectively performed on the two groups of single-axis magnetic sensor groups to obtain: , ; Then there is , so it can be obtained that .

11. The magnetic field immune system according to claim 10, wherein The proportionality coefficient a of the i-th uniaxial magnetic sensor's response to external magnetic field interference i The evaluation steps include: Set the target magnetic field to zero in the initial calibration stage; The B is measured by a three-axis magnetic sensor zcal = EB z The B is measured by four single-axis magnetic sensors zical = EB zi ; Assume EB zi = a i · EB z ; It can be deduced that B zical =a i ·B zcal , and after rearrangement, we can get .

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