Space magnetic field uniformity measurement device and uniformity analysis method

Abstract

The invention discloses a space magnetic field uniformity measuring device which comprises a three-degree-of-freedom moving platform, an integrated magnetic field sensor array arranged on the moving platform and the like, n * n magnetic sensitive elements are arranged in the integrated magnetic field sensor array, the moving platform is a three-degree-of-freedom platform, and n * n magnetic sensitive elements are arranged in the integrated magnetic field sensor array. The magnetic field sensor array can be moved in three mutually perpendicular directions. The space magnetic field uniformity measuring device disclosed by the invention can measure the magnetic field vector in the to-be-measured space, obtain a magnetic field vector equal distribution diagram of the to-be-measured space, and finish the analysis of the space magnetic field uniformity.

Description

Technical Field

[0001] The invention relates to a spatial magnetic field uniformity measuring device and a uniformity analyzing method, belonging to the technical field of magnetic field detection. Background Art

[0002] In view of the importance of determining the uniformity of the magnetic field environment generated around systems or devices such as nuclear magnetic resonance, magnetic field generators, and engines, it is necessary to analyze and determine the spatial magnetic field measurement and the degree of uniformity. The above measurement environment involves the simultaneous measurement of the magnetic field vectors of multiple measured points.

[0003] The sensors currently used for magnetic field measurement have a specific magnetic sensitive direction and a certain magnetic sensitive area, and cannot achieve multi-point magnetic field vector measurement in a certain space.

[0004] Therefore, it is necessary to carry out research on magnetic field vector measurement devices within a certain space to realize multi-point magnetic field measurement and uniformity analysis in space. Summary of the invention

[0005] In order to overcome the above problems, the inventors propose a spatial magnetic field uniformity measurement device, which includes a mobile platform with a stage and a magnetic field sensor array arranged on the mobile platform.

[0006] In a preferred embodiment, the magnetic field sensor array is provided with n×n magnetic sensitive elements. The mobile platform is a three-degree-of-freedom platform, which can move the magnetic field sensor array in three mutually perpendicular directions to measure the magnetic field of the measured position in the measured space in three directions respectively.

[0007] In a preferred embodiment, the mobile platform includes a first bracket, a second bracket and a loading platform, the first bracket is connected to the base via a rotating shaft, and the second bracket is connected to the first bracket via a rotating shaft.

[0008] The stage is connected to the second bracket via a screw rod, so that the stage can translate relative to the second bracket.

[0009] The magnetic field sensor array is fixed on the stage.

[0010] In a preferred embodiment, the first bracket is a rectangular structure, and the second bracket is a U-shaped structure.

[0011] In a preferred embodiment, a motor is provided at the interconnection position of the base, the first bracket, the second bracket and the stage to control the rotation angle of the stage and the translation distance of the corresponding measurement direction. The translation distance measured by the magnetic field sensor array in the three directions of x, y and z is determined according to the resolution of the magnetic field of the space to be measured, and is limited by the rotation accuracy of the motor and the minimum measurement interval of the magnetic sensitive elements in the sensor array.

[0012] The magnetic sensitive direction of the magnetic field sensor array is adjusted by a three-degree-of-freedom mobile platform. Driven by two lead screws, the magnetic field sensor array can complete linear reciprocating motion in a single direction. Driven by the first and second servos, the bracket completes arrayed magnetic field scanning in the x, y, and z directions respectively.

[0013] In a preferred embodiment, the differential output voltage signal of the sensor is amplified, filtered and A / D converted by the signal processing circuit, and the integrated magnetic field sensor array is a multi-channel differential output voltage signal, which is amplified by a combination of a multi-channel selection switch and an instrument amplifier. After filtering, the magnetic field vector information is synthesized, and polynomial interpolation is performed according to the coordinate information of the measurement point in the measured space and the corresponding magnetic induction intensity, and the magnetic field vector distribution map and the magnetic induction intensity distribution map in the measured space are drawn.

[0014] The present invention discloses a method for analyzing spatial magnetic field uniformity, comprising the following steps:

[0015] S1. Adjust the mobile platform so that the magnetic field sensor array obtains the magnetic induction intensity at different positions on three mutually perpendicular planes;

[0016] S2. Take the middle position planes in three mutually perpendicular moving directions as reference planes;

[0017] S3. Perform polynomial interpolation processing according to the coordinate information of the measurement points in the measured space and the corresponding magnetic induction intensity, and draw a magnetic field vector distribution map of the measured space that can reflect the magnetic field intensity at different positions;

[0018] S4. Obtaining the average magnetic induction intensity within the reference plane according to the magnetic induction intensity at different positions within the reference plane;

[0019] S5. Obtain the absolute deviation and relative deviation of the magnetic induction intensity of the magnetic field in the measured space according to the average value of the magnetic induction intensity in the reference plane.

[0020] In a preferred embodiment, in S4, the average magnetic induction intensity B0 in the reference plane is expressed as:

[0021]

[0022] Where N is the total number of all measured points in the reference plane, i is the serial number of the measured point, and B i Represents the magnetic induction intensity of the i-th measured point.

[0023] In a preferred embodiment, in S5, the absolute deviation ΔB of the magnetic induction intensity is expressed as:

[0024] ΔB=Bi -B0

[0025] The relative deviation η of the spatial magnetic field magnetic induction intensity is expressed as:

[0026]

[0027] In the space to be measured, the maximum relative deviation of the magnetic induction intensity at the measured point is used to determine the uniformity of the magnetic field.

[0028] The beneficial effects of the present invention include:

[0029] (1) Aiming at the problem of multi-point magnetic field vector measurement in the space to be measured, a method combining a three-degree-of-freedom mobile platform and a stage is used to complete the array scanning of the magnetic field of the measured points in three directions in the space to be measured.

[0030] (2) Aiming at the problem of measuring magnetic field vectors at multiple points in the space to be measured, the present invention develops an integrated magnetic field sensor array as a magnetic field measurement unit. By combining a multi-way selection switch and an instrument amplifier, amplification of multi-way output voltage signals is achieved, effectively reducing the complexity of the signal processing circuit.

[0031] (3) Aiming at the uniformity analysis of the space to be measured, a spatial magnetic field uniformity analysis method is proposed. By processing the acquired data and software analysis, the magnetic field vector distribution diagram of the space to be measured can be drawn, and the magnetic field uniformity can be determined by the relative deviation of the magnetic induction intensity.

[0032] Explanation of symbols

[0033] 1- Magnetic field sensor array;

[0034] 2- Base;

[0035] 3- first bracket;

[0036] 4- Second bracket;

[0037] 5- Stage. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A schematic structural diagram of a spatial magnetic field uniformity measuring device according to a preferred embodiment of the present invention is shown;

[0039] Figure 2 A schematic diagram showing a structure of a spatial magnetic field uniformity measurement device according to a preferred embodiment of the present invention when measuring magnetic field along the x direction;

[0040] Figure 3 A schematic diagram showing a structure of a spatial magnetic field uniformity measurement device according to a preferred embodiment of the present invention when measuring magnetic field along the y direction;

[0041] Figure 4 A schematic diagram showing a structure of a spatial magnetic field uniformity measurement device according to a preferred embodiment of the present invention when measuring magnetic field along the z direction;

[0042] Figure 5 The figure shows the distribution diagram of the magnetic field vector in the space near the permanent magnet;

[0043] Figure 6 Shows the distribution of magnetic induction intensity near a permanent magnet. DETAILED DESCRIPTION

[0044] The present invention will be further described in detail below through the accompanying drawings and embodiments. Through these descriptions, the characteristics and advantages of the present invention will become more clear and distinct.

[0045] The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. Although various aspects of the embodiments are shown in the drawings, the drawings are not necessarily drawn to scale unless otherwise noted.

[0046] According to a spatial magnetic field uniformity measuring device provided by the present invention, Figure 1 As shown, it includes a mobile platform with three degrees of freedom and an integrated magnetic field sensor array 1 arranged on the mobile platform.

[0047] Preferably, the integrated magnetic field sensor array 1 is provided with n×n magnetic sensitive elements, for example, 4×4 magnetic sensitive elements.

[0048] Furthermore, the three-degree-of-freedom platform combined with the integrated magnetic field sensor array can achieve one-dimensional, two-dimensional or three-dimensional magnetic field measurement.

[0049] According to a preferred embodiment of the present invention, the mobile platform is a three-degree-of-freedom platform capable of moving the integrated magnetic field sensor array 1 in three mutually perpendicular directions.

[0050] Furthermore, by adjusting the mobile platform, the magnetic sensitive direction of the integrated magnetic field sensor array 1 and the displacement in this direction are adjusted to achieve array scanning of the magnetic field information of the measured points in three directions, so that each measuring point in the measured space can achieve magnetic field measurement in three directions.

[0051] In a preferred embodiment, Figure 1-3 As shown, the mobile platform includes a first bracket 3, a second bracket 4 and a loading platform 5. The first bracket 3 is connected to the base 2 through a rotating shaft, and the second bracket 4 is connected to the first bracket 3 through a rotating shaft.

[0052] The stage 5 is connected to the second bracket 4 via a screw rod, so that the stage 5 can translate relative to the second bracket 4.

[0053] The integrated magnetic field sensor array 1 is fixed on the stage 5 .

[0054] In a preferred embodiment, the first bracket 3 is a rectangular structure to improve stability, and the second bracket 4 is a U-shaped structure to facilitate the installation of the loading platform 5.

[0055] In a preferred embodiment, a motor is provided at the position where the base 2, the first bracket 3, the second bracket 4 and the loading platform 5 are connected to each other, so as to control the rotation angle or the translation distance.

[0056] According to a preferred embodiment of the present invention, a first steering gear is horizontally provided on the upper surface of the base 2, and the first steering gear is used to control the rotation angle of the rotating shaft on the base.

[0057] In a preferred embodiment, a second steering gear is disposed on the first bracket 3 , and the rotation angle between the first bracket 3 and the second bracket 4 is controlled by the second steering gear.

[0058] Preferably, a third stepping motor is provided on the second bracket 4 to control the rotation of the lead screw, thereby controlling the translation distance of the stage 5 relative to the second bracket 4 .

[0059] More preferably, there are multiple screw rods, which are arranged in parallel, and the number of the third stepper motors is the same as the number of the screw rods, so that the connection between the loading platform 5 and the second bracket 4 is more stable.

[0060] In the present invention, the specific model and structure of the servo are not limited. For example, the first servo adopts MG996R and the second servo adopts SG90. Preferably, the servo is fixed by non-magnetic screws;

[0061] According to the present invention, the base 2, the first bracket 3, the second bracket 4, the stage 5, the rotating shaft, and the screw rod are all made of non-magnetic materials to avoid affecting the spatial magnetic field measurement. Preferably, the base, the first bracket, the second bracket, and the stage are all made of non-magnetic materials with a certain hardness, preferably 3D printing; the screw rod is made of non-magnetic materials with a certain hardness, preferably a material with a hardness of 155HB.

[0062] According to the present invention, a stepper motor controls the rotation of the lead screw to achieve linear reciprocating motion in a single direction, and a servo motor controls the rotation of the rotating shaft to achieve step-by-step magnetic field array scanning of the measured points in the three directions of x, y, and z in the measured space.

[0063] Furthermore, according to a preferred embodiment of the present invention, a single scan can synchronously obtain the magnetic field components of all measuring points in the measuring plane. The magnetic field at a certain point in the space is the synthesis of the measurements in three directions of the same magnetic sensitive element. Each measuring point in the measured space realizes magnetic field measurement in three directions to obtain the vector information of the measured space.

[0064] According to the present invention, the integrated magnetic field sensor array is a multi-channel differential output voltage signal, and a method of combining a multi-channel selection switch and an instrument amplifier is used to amplify the multi-channel differential output voltage signal as the detection output signal of the magnetic field sensor array.

[0065] The multi-way selector switch and the instrument amplifier are both commonly used devices in the art. For example, the multi-way selector switch adopts the CD4067 model; the instrument amplifier adopts the INA128 model.

[0066] The present invention provides a method for analyzing spatial magnetic field uniformity, comprising the following steps:

[0067] S1. Adjust the mobile platform through the operation panel, press the initial switch button, and the magnetic field sensor array, driven by the two screws, can complete a linear reciprocating motion in a single direction. The bracket, driven by the first and second servos, can complete the rotation in the x, y, and z directions in the measured space, thereby driving the magnetic field sensor array to obtain the magnetic induction intensity at different positions on three mutually perpendicular planes;

[0068] S2. Take the middle position planes in three mutually perpendicular moving directions as reference planes;

[0069] S3. Perform polynomial interpolation processing according to the coordinate information of the measurement point in the measured space and the corresponding magnetic induction intensity, and draw the magnetic field vector distribution map and the magnetic induction intensity distribution map; draw the magnetic field vector distribution of the measured space as shown Figure 5 As shown, the magnetic induction intensity distribution is Figure 6 As shown;

[0070] S4. Obtain the average value of the magnetic induction intensity in the reference plane according to the magnetic induction intensity at different positions in the reference plane, as a reference value for magnetic field uniformity analysis;

[0071] S5. Obtain the absolute deviation and relative deviation of the magnetic induction intensity of the magnetic field in the measured space according to the average value of the magnetic induction intensity in the reference plane.

[0072] In a preferred embodiment, in S4, the average magnetic induction intensity B0 in the reference plane is expressed as:

[0073]

[0074] Where N is the total number of all measured points in the reference plane, i is the serial number of the measured point, and Bi Represents the magnetic induction intensity of the i-th measured point.

[0075] In a preferred embodiment, in S5, the absolute deviation ΔB of the magnetic induction intensity is expressed as:

[0076] ΔB=B i -B0.

[0077] The relative deviation η of the spatial magnetic field magnetic induction intensity is expressed as:

[0078]

[0079] In the space to be measured, the maximum relative deviation of the magnetic induction intensity at the measured point is used to determine the uniformity of the magnetic field.

[0080] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the disclosure of the present invention can be performed in parallel, sequentially or in different orders, as long as the desired results of the technical solution disclosed in the present invention can be achieved, and this document does not limit this.

[0081] Example

[0082] Set up a spatial magnetic field uniformity measurement device, such as Figure 1 As shown, it includes a three-degree-of-freedom mobile platform and an integrated magnetic field sensor array arranged on the mobile platform, etc., wherein the integrated magnetic field sensor array is provided with 4×4 magnetic sensitive elements, and the magnetic field sensor array is sequentially input into the instrument amplifier through a multi-way selection switch, the multi-way selection switch adopts the CD4067 model, and the instrument amplifier adopts the INA128 model. The mobile platform includes a first bracket 3, a second bracket 4 and a stage 5, the first bracket 3 is connected to the base 2 through a rotating shaft, the second bracket 4 is connected to the first bracket 3 through a rotating shaft, the stage 5 is connected to the second bracket 4 through two parallel screws, so that the stage 5 can translate relative to the second bracket 4, and the integrated magnetic field sensor array 1 is fixed on the stage 5.

[0083] The first bracket 3 is a rectangular structure, the second bracket 4 is a U-shaped structure, a first servo is horizontally arranged on the upper surface of the base 2, using MG996R; two second servos are arranged on the first bracket 3, using SG90; a third stepper motor is arranged on the second bracket 4 to control the rotation of the screw rod, wherein the screw rod is made of non-magnetic material with a hardness of 155HB. Preferably, the base, the first bracket, the second bracket and the stage are made of non-magnetic materials with a certain hardness, preferably made by 3D printing;

[0084] The spatial magnetic field uniformity measuring device is used to measure the uniformity of a 1.5×1.5×1.5 cm 3 The magnetic field in the space is detected, and the actual magnetic field distribution about 10cm near the permanent magnet is about 3Gs.

[0085] Perform spatial magnetic field uniformity analysis by following the steps below:

[0086] S1. Adjust the mobile platform through the operation panel, press the initial switch button, and the magnetic field sensor array can complete a linear reciprocating motion in a single direction driven by the two screws. The bracket can complete the rotation in the x, y, and z directions in the measured space driven by the first and second servos, thereby driving the magnetic field sensor array to obtain the magnetic induction intensity at different positions on three mutually perpendicular planes. The measured displacement in the x, y, and z directions is 5mm;

[0087] S2. Take the middle position planes in three mutually perpendicular moving directions as reference planes;

[0088] S3. Perform polynomial interpolation processing according to the coordinate information of the measurement point in the measured space and the corresponding magnetic induction intensity, and draw the magnetic field vector distribution map and the magnetic induction intensity distribution map; draw the magnetic field vector distribution of the measured space as shown Figure 5 As shown, the magnetic induction intensity distribution is Figure 6 As shown;

[0089] S4. Obtain the average value of the magnetic induction intensity in the reference plane according to the magnetic induction intensity at different positions in the reference plane, as a reference value for magnetic field uniformity analysis;

[0090] S5. Obtain the absolute deviation and relative deviation of the magnetic induction intensity of the magnetic field in the measured space according to the average value of the magnetic induction intensity in the reference plane.

[0091] In S1, the magnetic induction intensity output by the magnetic field sensor array at different positions is obtained on three mutually perpendicular planes; in S2, the polynomial interpolation method is used to draw the distribution of the magnetic field vector in the space to be measured. Figure 5 As shown, the magnetic induction intensity distribution is Figure 6 As shown;

[0092] In S4, the average value of magnetic induction intensity B0 in the reference plane is expressed as:

[0093]

[0094] In S5, the absolute deviation ΔB of the magnetic induction intensity is expressed as:

[0095] ΔB=B i -B0.

[0096] The relative deviation η of the spatial magnetic field magnetic induction intensity is expressed as:

[0097]

[0098] In the space to be measured, the maximum relative deviation of the magnetic induction intensity at the measured point is used to determine the uniformity of the magnetic field.

[0099] According to the spatial magnetic field uniformity analysis method:

[0100] The average value of the magnetic induction intensity of all measuring points of the x-direction reference surface of the measured space is measured, B0=2.8Gs, and the maximum relative deviation of the magnetic induction intensity in the x-direction of the measured space is 3.5%;

[0101] The average magnetic induction intensity of all measuring points on the y-direction reference plane of the measured space is measured, and B0=2.9Gs. The maximum relative deviation of the magnetic induction intensity in the y-direction of the measured space is 3.4%.

[0102] The average magnetic induction intensity of all measuring points on the reference plane in the z direction of the measured space is measured, and B0=2.8Gs. The maximum relative deviation of the magnetic induction intensity in the z direction of the measured space is 3.5%.

[0103] Analyzing the relative deviation of the magnetic induction intensity of the measured point in the measured space, the magnetic field in the space has a certain uniformity.

[0104] The present invention has been described above in conjunction with preferred embodiments, but these embodiments are only exemplary and serve only as an illustration. On this basis, the present invention may be subjected to a variety of substitutions and improvements, all of which fall within the scope of protection of the present invention.

Claims

1. A spatial magnetic field uniformity measurement device, characterized in that: The invention comprises a mobile platform with a loading platform and a magnetic field sensor array arranged on the mobile platform.

2. The spatial magnetic field uniformity measuring device according to claim 1, characterized in that: The mobile platform is a three-degree-of-freedom platform, which can move the magnetic field sensor array in three mutually perpendicular directions to respectively implement magnetic field measurement of the measured position in the measured space in the three directions.

3. The spatial magnetic field uniformity measuring device according to claim 1, characterized in that: The magnetic field sensor array is provided with n×n magnetic sensitive elements and is fixed on the stage, and the magnetic field information of the measured points is simultaneously acquired in different planes through the mobile platform.

4. The spatial magnetic field uniformity measuring device according to claim 1 or 2, characterized in that: The magnetic field sensor array is a multi-channel differential output voltage signal, and a multi-channel selection switch and an instrument amplifier are used to amplify the multi-channel differential output voltage signal.

5. A method for analyzing spatial magnetic field uniformity, using the device as claimed in any one of claims 1 to 4, characterized in that: The following steps are involved: S1. Adjust the mobile platform so that the magnetic field sensor array obtains the magnetic induction intensity at different positions on three mutually perpendicular planes; S2. In three mutually perpendicular moving directions, respectively select the planes in the middle position of the corresponding directions as the reference planes for magnetic field measurement in the three directions; S3. Perform polynomial interpolation processing according to the coordinate information of the measurement points in the measured space and the corresponding magnetic induction intensity, and draw a magnetic field vector distribution map of the measured space that can reflect the magnetic field intensity at different positions; S4. Obtaining the average magnetic induction intensity within the reference plane according to the magnetic induction intensity at different positions within the reference plane; S5. Obtain the absolute deviation and relative deviation of the magnetic induction intensity of the magnetic field in the measured space according to the average value of the magnetic induction intensity in the reference plane.

6. The method for analyzing spatial magnetic field uniformity according to claim 5, characterized in that: In S4, the average value of magnetic induction intensity B0 in the reference plane is expressed as: Where N is the total number of all measured points in the reference plane, i is the serial number of the measured point, and B i Represents the magnetic induction intensity of the i-th measured point.

7. The method for analyzing spatial magnetic field uniformity according to claim 6, characterized in that: In S5, the absolute deviation of magnetic induction intensity ΔB is expressed as: ΔB=B i -B0 The relative deviation η of the magnetic induction intensity is expressed as: In the space to be measured, the maximum relative deviation of the magnetic induction intensity at the measured point is used to determine the uniformity of the magnetic field.

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