Magnetic field sensor measurement parameter calibration method and system

Abstract

The invention relates to the field of magnetic array current sensors, and provides a calibration method and system for measurement parameters of a magnetic field sensor. The magnetic field sensor measurement parameter calibration method comprises the following steps: enabling a long straight conductor with known current and known position to vertically pass through planes where all magnetic field sensors are located, changing the position of the long straight conductor for multiple times, and respectively recording the measurement parameters of the long straight conductor when the long straight conductor is located at different positions; the position coordinates of the long straight conductor, the current magnitude and the magnetic field actually measured by the magnetic field sensor; taking the position parameter of the magnetic field sensor as a scanning parameter, calculating an error between a calculated magnetic field of the magnetic field sensor and an actually measured magnetic field under a given combination of the position of the long straight conductor and the position parameter of the magnetic field sensor, and respectively calculating the sum of error absolute values as a target function when the long straight conductor is located at a plurality of different positions; and the position parameter corresponding to the minimum value of the target function is used as a calibration result, and calibration of all magnetic field sensor measurement parameters is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of current measurement and calibration of magnetic array current sensors, and in particular to a method and system for calibrating measurement parameters of magnetic field sensors. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] The current measurement principle of the magnetic array current sensor is: use multiple magnetic field sensors to measure the magnetic field at multiple spatial magnetic field measurement points around the measured current conductor, and use the measured magnetic field information and current inversion algorithm to achieve non-contact measurement of the measured current. Thanks to the mature development of magnetic field sensing technology, broadband current measurement can be achieved through high-sensitivity and wide-band measurement of the magnetic field generated by the measured current, and because the size of the magnetic field sensor can be very small, the magnetic array current sensor built based on the magnetic field sensor has a compact structure and can be directly arranged at the high-voltage end, eliminating the expensive and complex insulation structure. Based on the above advantages, the magnetic array current sensor has great application prospects in distributed wide-area measurement.

[0004] However, in order to achieve accurate inversion of magnetic field to current, it is first necessary to accurately calibrate the measurement parameters of each magnetic field sensor, including the position coordinates, magnetic sensitivity direction angle, and sensitivity coefficient of the magnetic field sensor. The sensitivity coefficient can be calibrated directly through the Helmholtz coil system. As for the measurement parameters such as the position coordinates and magnetic sensitivity direction angle of the magnetic field sensor, when the magnetic field sensor is fixed, the position and magnetic sensitivity direction angle will inevitably deviate from the rated value, but there is no reliable physical means to accurately measure them. Summary of the invention

[0005] In order to solve the technical problems existing in the above-mentioned background technology, the present invention provides a method and system for calibrating measurement parameters of a magnetic field sensor, aiming to achieve accurate calibration of all measurement parameters of the magnetic field sensor.

[0006] In order to achieve the above object, the present invention adopts the following technical solution: A first aspect of the present invention provides a method for calibrating parameters measured by a magnetic field sensor.

[0007] A method for calibrating a magnetic field sensor measurement parameter, comprising: A long straight conductor with a known current and a known position is passed vertically through the plane where all magnetic field sensors are located, and the position of the long straight conductor is changed multiple times. The position coordinates of the long straight conductor, the current magnitude, and the magnetic field actually measured by the magnetic field sensor are recorded when the long straight conductor is at different positions. Taking the position parameters of the magnetic field sensor as the scanning parameters, under a given combination of the position of the long straight conductor and the position parameters of the magnetic field sensor, the error between the magnetic field calculated by the magnetic field sensor and the magnetic field actually measured is calculated, and when the long straight conductor is at multiple different positions, the sum of the absolute values ​​of the errors is calculated as the objective function; the position parameters corresponding to the minimum value of the objective function are taken as the calibration results; wherein the position parameters include: position coordinates and magnetic sensitive direction angles.

[0008] Furthermore, the magnetic field actually measured by the magnetic field sensor is obtained according to its output voltage signal combined with a sensitivity coefficient of the magnetic field sensor.

[0009] Furthermore, the sensitivity coefficient of the magnetic field sensor is calibrated using a Helmholtz coil system.

[0010] Furthermore, the Helmholtz coil system comprises: A signal generator, used for outputting an AC voltage signal; A power amplifier, connected to the signal generator, is used to amplify the signal output by the signal generator to generate a coil excitation current; A Helmholtz coil, connected to a power amplifier, is used to generate a uniform magnetic field after the coil excitation current flows through it; Fluxgate sensor, used to measure the actual magnetic field of a uniform magnetic field; The data acquisition module is used to collect the actual magnetic field and upload it to the host computer.

[0011] Furthermore, the calibration process using the Helmholtz coil system includes: the Helmholtz coil generates a uniform magnetic field, placing a magnetic field sensor in the uniform magnetic field area, and the magnetic sensitivity direction of the magnetic field sensor is in the direction of the uniform magnetic field; using a magnetic field sensor probe to measure the magnetic field of the uniform magnetic field, and the sensitivity coefficient of the magnetic field sensor is the ratio between the output voltage of the magnetic field sensor and the magnetic field sensor probe.

[0012] Furthermore, the magnetic field sensor calculates the magnetic field by forward calculation using Biotsafar's law.

[0013] Furthermore, the sensitivity coefficient is expressed by the following formula:

[0014] in, represents the sensitivity coefficient of the magnetic field sensor, represents the output voltage of the magnetic field sensor, Indicates the magnetic field value measured by the magnetic field sensor probe.

[0015] Furthermore, the objective function is expressed by the following formula:

[0016] in, x k , y k , θ k Respectively represent k The x-axis coordinate, y-axis coordinate, and magnetic sensitive direction angle of each magnetic field sensor. j represents the number of times the position of a long straight conductor changes, Indicates the calculation k The magnetic field measured by the magnetic field sensor, Indicates current I j In the position ( x k , y k ) component of the magnetic field generated at .

[0017] A second aspect of the present invention provides a system for calibrating parameters measured by a magnetic field sensor.

[0018] A calibration system for measuring parameters of a magnetic field sensor, comprising: The experimental module is configured as follows: a long straight conductor with a known current and a known position is passed vertically through the plane where all magnetic field sensors are located, the position of the long straight conductor is changed multiple times, and the position coordinates, current magnitude, and magnetic field actually measured by the magnetic field sensor of the long straight conductor are recorded when the long straight conductor is at different positions; The calibration module is configured as follows: taking the position parameters of the magnetic field sensor as scanning parameters, calculating the error between the magnetic field calculated by the magnetic field sensor and the magnetic field actually measured under a given combination of the position of the long straight conductor and the position parameters of the magnetic field sensor, and calculating the sum of the absolute values ​​of the errors as the objective function when the long straight conductor is at multiple different positions; taking the position parameters corresponding to the minimum value of the objective function as the calibration result; wherein the position parameters include: position coordinates and magnetic sensitive direction angles.

[0019] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a method, system, medium, equipment and product for calibrating the measurement parameters of a magnetic field sensor. The method includes: using a Helmholtz coil to calibrate the sensitivity coefficient of the magnetic field sensor; changing the position of a long straight conductor that vertically passes through the plane where all magnetic field sensors are located, and passing a current with a known value, recording the position coordinates of the long straight conductor, the current magnitude and the magnetic field actually measured by the magnetic field sensor when the long straight conductor is at different positions; using the position parameters of the magnetic field sensor (including the position coordinates and the magnetic sensitive direction angle) as scanning parameters, under a given combination of the position of the long straight conductor and the position parameters of the magnetic field sensor, calculating the error between the magnetic field obtained by the magnetic field sensor through the Biotsafar law forward calculation and the actual measured magnetic field, and when the long straight conductor is at three different positions, respectively calculating the sum of the absolute values ​​of the above errors as the objective function; among all the position parameter combinations, the position parameter combination corresponding to the minimum value of the objective function is the calibration result of the position parameters of the magnetic field sensor. According to the above steps, the calibration of all magnetic field sensor measurement parameters can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0021] Figure 1 is a flow chart of a method for calibrating a magnetic field sensor measurement parameter according to the present invention; Figure 2 is a schematic diagram of different long straight conductors generating magnetic fields at the location of the kth magnetic field sensor shown in the present invention; Figure 3 is the Helmholtz calibration system shown in the present invention; Figure 4 is a relationship diagram between the objective function value of the fourth magnetic field sensor and its position parameter combination shown in the present invention; Figure 5 is a structural diagram of a calibration system for measuring parameters of a magnetic field sensor shown in the present invention; Figure 6 It is a physical test diagram of magnetic field sensor measurement parameter calibration shown in the present invention; Figure 7 It is a design principle diagram of a magnetic field sensor based on a small coil shown in the present invention. DETAILED DESCRIPTION

[0022] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0023] It should be noted that the following detailed descriptions are all illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0024] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0025] It should be noted that the flowcharts and block diagrams in the accompanying drawings illustrate the possible implementation architecture, functions and operations of the methods and systems according to various embodiments of the present disclosure. It should be noted that each box in the flowchart or block diagram can represent a module, a program segment, or a part of a code, and the module, program segment, or a part of a code may include one or more executable instructions for implementing the logical functions specified in each embodiment. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in an order different from that marked in the accompanying drawings. For example, two boxes represented in succession can actually be executed substantially in parallel, or they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the flowchart and / or block diagram, and the combination of boxes in the flowchart and / or block diagram can be implemented using a dedicated hardware-based system that performs a specified function or operation, or can be implemented using a combination of dedicated hardware and computer instructions.

[0026] Embodiment 1 like Figure 1 As shown, this embodiment provides a method for calibrating a magnetic field sensor measurement parameter, comprising the following steps: Step 1: Use a Helmholtz coil system to calibrate the sensitivity coefficient of the magnetic field sensor. Specifically, the Helmholtz coil system used is as follows: Figure 3As shown in the figure, the system includes a Helmholtz coil, a signal generator, a power amplifier, a high-accuracy fluxgate sensor probe, and a signal processing unit (fluxgate meter) of the fluxgate sensor. The signal generator outputs an AC voltage signal, which is amplified by the power amplifier to generate a coil excitation current, which generates a uniform magnetic field after flowing through the Helmholtz coil. The magnetic field sensor is placed in the uniform magnetic field area, and the magnetic sensitivity direction of the magnetic field sensor is strictly in the direction of the uniform magnetic field; a high-precision magnetic field sensor probe is used to measure the magnetic field of the uniform magnetic field, and the ratio between the output voltage of the magnetic field sensor and the magnetic field measured by the magnetic field sensor probe is the sensitivity coefficient of the magnetic field sensor. The collected data is uploaded to the host computer for processing through the data acquisition module (DAQ).

[0027] Specifically, the Helmholtz coil calibrates the magnetic field sensor, including the following steps (1) Preparation Equipment inspection: Ensure that the Helmholtz coil, magnetic field sensor, power supply, data acquisition system and other equipment are in good working condition.

[0028] Environmental preparation: Select an environment without external magnetic field interference for calibration to reduce errors.

[0029] Sensor installation: Fix the magnetic field sensor at the center of the Helmholtz coil, making sure its axis coincides with the coil axis.

[0030] (2) Preliminary testing Energize the coil: Energize the Helmholtz coil and gradually increase the current to observe the response of the magnetic field sensor.

[0031] Initial calibration: Perform an initial calibration of the sensor using a standard source of known magnetic field strength (such as a gauss meter) to check its basic performance.

[0032] (3) Formal calibration Set current range: Set the current range of the Helmholtz coil as required, usually selecting a series of equally spaced current values.

[0033] Data collection: At each current value, record the output value of the magnetic field sensor. Make sure each current value is stable before recording.

[0034] Repeated measurements: To improve the accuracy of the calibration, multiple repeated measurements can be made at each current value and the average value is taken as the final result.

[0035] (4) Data processing and analysis Data fitting: Fit the collected data to obtain the relationship curve between the magnetic field strength and the sensor output.

[0036] Performance evaluation: Evaluate the sensitivity coefficient of the sensor based on the fitting results.

[0037] Error analysis: Analyze the sources of errors that may be introduced during the calibration process, such as temperature changes, electromagnetic interference, etc., and take appropriate measures to correct them.

[0038] (5) Calibration report and adjustment Write calibration report: organize the calibration process, data, analysis results, etc. into a calibration report.

[0039] Sensor adjustment: Based on the calibration results, make necessary adjustments or repairs to the sensor to ensure that its performance meets the requirements.

[0040] Save calibration records: Keep calibration records for future reference and use.

[0041] During the calibration process, ensure that the Helmholtz coil and the magnetic field sensor are in a good thermal equilibrium state to avoid the influence of temperature changes on the calibration results. Avoid calibration in a strong magnetic field environment to reduce the interference of the external magnetic field. Before calibration, the magnetic field sensor should be preheated to ensure its stable performance.

[0042] By following the above steps, the accuracy and reliability of the sensitivity coefficient of the Helmholtz coil calibration magnetic field sensor can be ensured. However, the specific calibration process may vary depending on factors such as device model and application scenario, so it should be adjusted according to specific circumstances in actual operation.

[0043] Step 2: If Figure 2 As shown in the figure, a long straight conductor is passed vertically through the plane where all magnetic field sensors are located, and a current of known value is passed through it. The position of the long straight conductor is changed at least 3 times. j to index the position of the long straight conductor), record the position coordinates of the long straight conductor ( x j , y j ), the current flowing through a long straight conductor I j , and the magnetic field actually measured by the magnetic field sensor B k, j ; Step 3: Use the position parameters (position coordinates and magnetic sensitive direction angle) of the magnetic field sensor as scanning parameters, and set the scanning range and step size of the position parameters. k The position coordinates and magnetic sensitive direction angles of the magnetic field sensors are respectively ( x k , y k )and θ k ,like Figure 2 Set the k The scanning ranges of the horizontal and vertical coordinates of the magnetic field sensor positions are [ x k,r + a , x k,r - a ]、[ y k,r + b , y k,r - b ], the scanning range of magnetic sensitive direction angle is [ θ k, r +c , θ k, r - c ],in x k, r , y k, r , θ k, r Respectively k The horizontal coordinate, vertical coordinate and rated value of magnetic sensitive direction angle of each magnetic field sensor position are a , b , c are the horizontal and vertical coordinates of the magnetic field sensor and the deviation of the actual position of the magnetic sensitive direction angle from the corresponding rated value; specify Δ x k , Δ y k , Δ θ k Respectively k The scanning step length of the horizontal coordinate, vertical coordinate and magnetic sensitive direction angle position parameters of the magnetic field sensor.

[0044] For k The position parameter combination of the magnetic field sensor ( x k , y k , θ k ) and the long straight conductor position ( x j , y j ), and combined with the current flowing through a long straight conductor I j , through Biosafari's law, forward calculation k The magnetic field measured by the magnetic field sensor ,Right now: (1) in, and The current I j In the position ( x k , y k ) x , y The magnetic field component in the axial direction is expressed as follows: (2) in, μ 0 is the vacuum magnetic permeability; ( x j , y j ) is the j The position coordinates of the conductor.

[0045] When the long straight conductor is in 3 different positions, k The sum of the absolute values ​​of the errors between the magnetic field calculated by the forward direction of the magnetic field sensor and the magnetic field actually measured is defined as the objective function, that is: (3) in, Represents the objective function.

[0046] Step 4: During the scanning process of the position parameters of the magnetic field sensor, different position parameter combinations ( x k , y k , θ k ) is brought into the objective function (3). When the objective function reaches the minimum value, the corresponding position parameter combination is the calibration result of the magnetic field sensor position parameters, namely: (4) in, x k,c , y k,c and θ k, c Respectively k The results of calibration of the horizontal and vertical coordinates and magnetic sensitive direction angle of a magnetic field sensor.

[0047] The present invention provides a method for calibrating the measurement parameters of a magnetic field sensor, including: using a Helmholtz coil to calibrate the sensitivity coefficient of the magnetic field sensor; changing the position of a long straight conductor that vertically passes through the plane where all magnetic field sensors are located, and passing a current of known value, recording the position coordinates of the long straight conductor, the current magnitude, and the magnetic field actually measured by the magnetic field sensor when the long straight conductor is at different positions; using the position parameters of the magnetic field sensor (including the position coordinates and the magnetic sensitive direction angle) as scanning parameters, under a given combination of the position of the long straight conductor and the position parameters of the magnetic field sensor, calculating the error between the magnetic field obtained by the magnetic field sensor through the Biotsafar law forward calculation and the actual measured magnetic field, and when the long straight conductor is at three different positions, respectively calculating the sum of the absolute values ​​of the above errors as the objective function; among all the position parameter combinations, the position parameter combination corresponding to the minimum value of the objective function is the calibration result of the position parameters of the magnetic field sensor. According to the above steps, the calibration of all magnetic field sensor measurement parameters can be achieved.

[0048] The feasibility and effectiveness of the proposed method for calibrating parameters of a magnetic field sensor are now described in conjunction with an embodiment.

[0049] The proposed method is analyzed and verified by simulation.

[0050] Figure 2 The figure is a schematic diagram of using 6 magnetic field sensors to measure current according to an embodiment of the present invention. All magnetic field sensors are equally spaced around the current conductor to be measured, and the magnetic sensitivity direction is approximately in the direction of the magnetic field generated by the current. During the simulation process, the position coordinates of all magnetic field sensors and the rated values ​​of the magnetic sensitivity direction angles are shown in Table 1. The position of the current conductor to be measured is changed 3 times, as shown in Table 1. Figure 2 As shown in the figure, the position coordinates of conductors 1, 2, and 3 are (-10, 5) mm, (6, 1) mm, and (-8, -4) mm respectively. The current flowing through conductors 1, 2, and 3 at different positions is , , The above currents are all 100 A. k The magnetic fields generated at the locations of the magnetic field sensors are B 1. B 2 and B 3.

[0051] In order to simulate the deviation of the magnetic field sensor from its rated position during the fixed installation process, an offset is set for the position parameter of each magnetic field sensor. The offset range of the horizontal and vertical coordinates of each magnetic field sensor is ±1mm, and the offset range of its magnetic sensitive direction angle is ±10°, that is, a = b = 1 mm,c = π / 18. After applying the offset to the horizontal and vertical coordinates and magnetic sensitive direction angle of each magnetic field sensor, the actual values ​​of the position parameters of each magnetic field sensor are shown in Table 1, where ( x k, n , y k, n ) is the k The rated value of the magnetic field sensor coordinate position, ( x k, t , y k, t ) is the k The coordinate position of each magnetic field sensor is relative to its rated value ( x k, n , y k, n ) is the actual value after the offset, ( x k, c , y k, c ) is the first k The coordinate position of the magnetic field sensor. If the calibration result is accurate, the coordinate position after calibration should be the same as ( x k, t , y k, t )equal.

[0052] Table 1 Rated values, actual values, and calibration values ​​of magnetic field sensor position parameters

[0053] When performing parameter scanning on the position coordinates and magnetic sensitive direction angle of the magnetic field sensor, the scanning step length of the horizontal and vertical coordinates is set to Δ x k = Δ y k = 0.1 mm, and the scanning step of the magnetic sensitive direction angle is set to Δ θ k= 1°. The setting of the scanning step length of the horizontal and vertical coordinate parameters of the magnetic field sensor is related to the position accuracy of the long straight conductor. In the actual implementation process, in order to determine the position coordinates of the long straight conductor, 3D printing technology can be selected to print out a support structure of the long straight conductor, and the printing accuracy of 3D printing technology can reach 0.1 mm. Since the position accuracy of the long straight conductor is 0.1 mm, the calibration accuracy of the horizontal and vertical coordinates of the magnetic field sensor cannot exceed 0.1 mm, so the scanning step length of the position coordinates of the magnetic field sensor is set to 0.1 mm. Parameter scanning of the position coordinates and magnetic sensitive direction angle of the magnetic field sensor is essentially a combination enumeration of the horizontal coordinate, vertical coordinate and magnetic sensitive direction angle. The smaller the step length, the greater the number of combinations of the horizontal coordinate, vertical coordinate and magnetic sensitive direction angle. In this way, the scanning step length of the magnetic sensitive direction angle is only set to 1° to reduce the number of combinations to a certain extent.

[0054] In order to determine the actual values ​​of the horizontal coordinate, vertical coordinate and magnetic sensitive direction angle of the magnetic field sensor, the horizontal coordinate, vertical coordinate and magnetic sensitive direction angle are scanned within their set ranges. For each combination of them, the objective function value is calculated according to formula (4). When the objective function value reaches the minimum, the corresponding horizontal coordinate, vertical coordinate and magnetic sensitive direction angle are the calibration results of the magnetic field sensor position parameters. Figure 4 When calibrating the first magnetic field sensor, the relationship between the objective function value and different position parameter combinations is given by Figure 4 It can be seen that the objective function value has a trend of first decreasing and then increasing, and the objective function value has a unique minimum value. When calibrating the horizontal coordinate, vertical coordinate and magnetic sensitive direction angle of the magnetic field sensor, it is essentially necessary to solve three position variables. Therefore, the long straight conductor needs to be placed in at least three different positions to construct the equation shown in formula (1). In this way, the horizontal coordinate, vertical coordinate and magnetic sensitive direction angle of the magnetic field sensor can be uniquely determined. Finally, the calibration results of the horizontal coordinate, vertical coordinate and magnetic sensitive direction angle of all magnetic field sensors are listed in Table 1, which are equal to the corresponding actual values, thereby verifying the feasibility of the magnetic field sensor position parameters proposed in the present invention.

[0055] Embodiment 2 like Figure 5 As shown, this embodiment provides a calibration system for measuring parameters of a magnetic field sensor, including: The experimental module is configured as follows: a long straight conductor with a known current and a known position is passed vertically through the plane where all magnetic field sensors are located, the position of the long straight conductor is changed multiple times, and the position coordinates, current magnitude, and magnetic field actually measured by the magnetic field sensor of the long straight conductor are recorded when the long straight conductor is at different positions; The calibration module is configured as follows: taking the position parameters of the magnetic field sensor as scanning parameters, calculating the error between the magnetic field calculated by the magnetic field sensor and the magnetic field actually measured under a given combination of the position of the long straight conductor and the position parameters of the magnetic field sensor, and calculating the sum of the absolute values ​​of the errors as the objective function when the long straight conductor is at multiple different positions; taking the position parameters corresponding to the minimum value of the objective function as the calibration result; wherein the position parameters include: position coordinates and magnetic sensitive direction angles.

[0056] The present invention uses a Helmholtz coil to calibrate the sensitivity coefficient of the magnetic field sensor; change the position of a long straight conductor that vertically passes through the plane where all magnetic field sensors are located, and pass a current with a known value, record the position coordinates of the long straight conductor, the current magnitude, and the magnetic field actually measured by the magnetic field sensor when the long straight conductor is at different positions; use the position parameters of the magnetic field sensor (including the position coordinates and the magnetic sensitive direction angle) as scanning parameters, and calculate the error between the magnetic field obtained by the magnetic field sensor through the Biotsafar law forward calculation and the actual measured magnetic field under a given combination of the position of the long straight conductor and the position parameters of the magnetic field sensor, and calculate the sum of the absolute values ​​of the above errors when the long straight conductor is at three different positions as the objective function; among all the position parameter combinations, the position parameter combination corresponding to the minimum value of the objective function is the calibration result of the position parameters of the magnetic field sensor. According to the above scheme, the calibration of all magnetic field sensor measurement parameters can be achieved.

[0057] In some embodiments, the magnetic field actually measured by the magnetic field sensor is obtained based on its output voltage signal combined with a sensitivity coefficient of the magnetic field sensor.

[0058] In some embodiments, the sensitivity coefficient of the magnetic field sensor is calibrated using a Helmholtz coil system.

[0059] In some embodiments, the Helmholtz coil system comprises: A signal generator, used for outputting an AC voltage signal; A power amplifier, connected to the signal generator, is used to amplify the signal output by the signal generator to generate a coil excitation current; A Helmholtz coil, connected to a power amplifier, is used to generate a uniform magnetic field after the coil excitation current flows through it; Fluxgate sensor, used to measure the actual magnetic field of a uniform magnetic field; The data acquisition module is used to collect the actual magnetic field and upload it to the host computer.

[0060] In some embodiments, the calibration process using the Helmholtz coil system includes: the Helmholtz coil generates a uniform magnetic field, placing a magnetic field sensor in the uniform magnetic field area, and the magnetic sensitivity direction of the magnetic field sensor is in the direction of the uniform magnetic field; using a magnetic field sensor probe to measure the magnetic field of the uniform magnetic field, and the sensitivity coefficient of the magnetic field sensor is the ratio between the output voltage of the magnetic field sensor and the magnetic field sensor probe.

[0061] In some embodiments, the magnetic field sensor calculates the magnetic field by forward calculation of Biotsafar's law.

[0062] In some embodiments, the sensitivity coefficient is expressed by the following formula:

[0063] in, represents the sensitivity coefficient of the magnetic field sensor, represents the output voltage of the magnetic field sensor, Indicates the magnetic field value measured by the magnetic field sensor probe.

[0064] In some embodiments, the objective function is expressed by the following formula:

[0065] in, x k , y k , θ k Respectively represent k The x-axis coordinate, y-axis coordinate, and magnetic sensitive direction angle of each magnetic field sensor. j represents the number of times the position of a long straight conductor changes, Indicates the calculation k The magnetic field measured by the magnetic field sensor, Indicates current I j In the position ( x k , y k ) component of the magnetic field generated at .

[0066] In order to further verify the validity of the invention patent, physical test was carried out. Specifically, 3D printing technology was used to produce a mechanical structure that can fix the position of the conductor, such as Figure 6 The structure includes 23 parallel through holes, the position of each through hole is known, and long straight conductors can be placed in each through hole to generate a standard magnetic field. The designed magnetic field sensor uses a small coil with a diameter of 10 mm. The small coil couples the alternating magnetic field to generate an alternating voltage signal. The voltage signal is in a differential relationship with the measured magnetic field, that is:

[0067] In the formula, is the output AC voltage signal of the small coil; To couple to the alternating magnetic field of the small coil, is the magnetic field coupling coefficient of the small coil.

[0068] In order to measure the magnetic field, the output signal of the small coil needs to be integrated, that is:

[0069] In the formula, is the integration coefficient.

[0070] In order to directly output the analog magnetic field signal, an analog integrator is designed, such as Figure 7 As shown, the output signal of the small coil is first amplified by a differential amplifier, then amplified by a first-stage amplifier, and the amplified signal is passed through an integrator to obtain an integral signal, then amplified by a second-stage amplification unit, and finally filtered by a high-pass filter to eliminate high-frequency components. Since the alternating signal output by the small coil is very weak, a multi-stage amplification strategy is adopted to obtain a sufficiently strong output signal and improve the signal-to-noise ratio.

[0071] The differential amplifier uses an AD8429 amplifier with a gain of 20; the first-stage amplifier includes an Im2904 amplifier, resistors R3 and R4. , ; The integrator includes resistor R5 and capacitor C3. , The secondary amplifier includes the Im2904 amplifier, resistor R6 and resistor R7. , ; The high-pass filter includes resistor R8 and capacitor C4, , .

[0072] The positive input terminal of the magnetic sensor is connected to the negative input terminal of the differential amplifier through the resistor R1 and the capacitor C1, and the negative input terminal of the magnetic sensor is connected to the positive input terminal of the differential amplifier through the resistor R2 and the capacitor C2; the resistor R1, the capacitor C1, the resistor R2 and the capacitor C2 are all grounded; wherein, , , , .

[0073] The output end of the differential amplifier is connected to the positive input end of the first-stage amplifier, the negative input end of the first-stage amplifier is grounded through a resistor R3, the negative input end of the first-stage amplifier is also connected to the output end of the first-stage amplifier through a resistor R4, the output end of the first-stage amplifier is connected to one end of a resistor R5, the other end of the resistor R5 is respectively connected to one end of a capacitor C3 and the positive input end of the second-stage amplifier, the other end of the capacitor C3 is grounded, the negative input end of the second-stage amplifier is grounded through a resistor R6, the negative input end of the second-stage amplifier is also connected to the output end of the second-stage amplifier through a resistor R7, the output end of the second-stage amplifier is connected to one end of a capacitor C4, the other end of the capacitor C4 is connected to one end of a resistor R8, and serves as a voltage output end Vout; the other end of the resistor R8 is grounded.

[0074] Since the amplification factor of the operational amplifier in the amplification circuit is inaccurate, and these amplification factors are closely related to the sensitivity coefficient of the magnetic field sensor, they need to be calibrated. According to the specific steps given in the above embodiment, the position parameters and magnetic sensitive direction angles of each magnetic field sensor are calibrated, and then the current inversion calculation is performed based on the calibrated results, so that the accuracy of current inversion can be effectively improved.

[0075] Generally, in order to realize the three-phase current back calculation, a magnetic field-current inversion model is constructed, and the objective function of the model is as follows:

[0076] In the formula, is the magnetic field actually measured by the kth magnetic field sensor, N is the number of magnetic field sensors, , , are the horizontal and vertical coordinates of the jth conductor and the measured current, respectively, and j represents the three-phase currents of a, b, and c; Under the action of three-phase current, k The calculation result of the magnetic field measured by a magnetic field sensor is as follows:

[0077] The amplitude of the three-phase current is set to 10 A, the phase difference between the phase currents is 120°, and a multi-channel sampler is used to sample the output signal of each magnetic field sensor. The measured magnetic field of each magnetic field sensor is calculated based on the sensitivity coefficient of the magnetic field sensor, that is:

[0078] in, represents the sensitivity coefficient of the magnetic field sensor, Represents the output voltage of the magnetic field sensor.

[0079] Then, the measured values ​​of each magnetic field sensor are substituted into the magnetic field-current inversion model, and the current inversion is calculated using the rated value and calibration value of the magnetic field sensor measurement parameters. The accuracy of the current inversion is evaluated using the amplitude relative error. The specific results are shown in the following table: Table 2 Results of three-phase current back-calculation using the rated and calibrated values ​​of the magnetic field sensor measurement parameters

[0080] It can be seen from Table 2 that when the three-phase current is back-calculated with the rated value of the measurement parameter, the maximum relative error of the amplitude of the three-phase current is 4.2%, and when the current is back-calculated with the calibrated value of the measurement parameter, the maximum relative error of the amplitude of the three-phase current is 2.3%. It can be seen that only when the measurement parameters of the magnetic field sensor are accurate can the measured current be accurately back-calculated, thereby demonstrating that the present invention can accurately calibrate the measurement parameters of the magnetic field sensor.

[0081] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for calibrating a magnetic field sensor measurement parameter, characterized in that: include: A long straight conductor with a known current and a known position is passed vertically through the plane where all magnetic field sensors are located, and the position of the long straight conductor is changed multiple times. The position coordinates of the long straight conductor, the current magnitude, and the magnetic field actually measured by the magnetic field sensor are recorded when the long straight conductor is at different positions. Taking the position parameter of the magnetic field sensor as the scanning parameter, under the given combination of the position parameter of the long straight conductor and the position parameter of the magnetic field sensor, the error between the magnetic field calculated by the magnetic field sensor and the magnetic field actually measured is calculated, and when the long straight conductor is at multiple different positions, the sum of the absolute values ​​of the errors is calculated as the objective function; The position parameter corresponding to the minimum value of the objective function is taken as the calibration result; wherein the position parameter includes: position coordinates and magnetic sensitive direction angle.

2. The method for calibrating the magnetic field sensor measurement parameters according to claim 1, characterized in that: The magnetic field actually measured by the magnetic field sensor is obtained according to its output voltage signal combined with the sensitivity coefficient of the magnetic field sensor.

3. The method for calibrating the magnetic field sensor measurement parameters according to claim 2, characterized in that: The sensitivity coefficient of the magnetic field sensor is calibrated using a Helmholtz coil system.

4. The method for calibrating the magnetic field sensor measurement parameters according to claim 3, characterized in that: The Helmholtz coil system comprises: A signal generator, used for outputting an AC voltage signal; A power amplifier, connected to the signal generator, is used to amplify the signal output by the signal generator to generate a coil excitation current; A Helmholtz coil, connected to a power amplifier, is used to generate a uniform magnetic field after the coil excitation current flows through it; Fluxgate sensor, used to measure the actual magnetic field of a uniform magnetic field; The data acquisition module is used to collect the actual magnetic field and upload it to the host computer.

5. The method for calibrating the magnetic field sensor measurement parameters according to claim 3, characterized in that: The calibration process using the Helmholtz coil system includes: the Helmholtz coil generates a uniform magnetic field, placing a magnetic field sensor in the uniform magnetic field area, and the magnetic sensitivity direction of the magnetic field sensor is in the direction of the uniform magnetic field; using a magnetic field sensor probe to measure the magnetic field of the uniform magnetic field, and the sensitivity coefficient of the magnetic field sensor is the ratio between the output voltage of the magnetic field sensor and the magnetic field value measured by the magnetic field sensor probe.

6. The method for calibrating the magnetic field sensor measurement parameters according to claim 5, characterized in that: The sensitivity coefficient is expressed by the following formula: in, represents the sensitivity coefficient of the magnetic field sensor, represents the output voltage of the magnetic field sensor, Indicates the magnetic field value measured by the magnetic field sensor probe.

7. The method for calibrating the magnetic field sensor measurement parameters according to claim 1, characterized in that: The magnetic field sensor calculates the magnetic field by forward calculation using the Biotsafar law.

8. The method for calibrating the magnetic field sensor measurement parameters according to claim 1, characterized in that: The objective function is expressed by the following formula: in, represents the objective function, x k , y k , θ k Respectively represent k The x-axis coordinate, y-axis coordinate, and magnetic sensitive direction angle of each magnetic field sensor. j represents the number of times the position of a long straight conductor changes, Indicates the calculation k The magnetic field measured by the magnetic field sensor, Indicates current I j In the position ( x k , y k ) component of the magnetic field generated at .

9. A calibration system for measuring parameters of a magnetic field sensor, characterized in that: include: The experimental module is configured as follows: a long straight conductor with a known current and a known position is passed vertically through the plane where all magnetic field sensors are located, the position of the long straight conductor is changed multiple times, and the position coordinates, current magnitude, and magnetic field actually measured by the magnetic field sensor of the long straight conductor are recorded when the long straight conductor is at different positions; The calibration module is configured to: take the position parameter of the magnetic field sensor as the scanning parameter, calculate the error between the magnetic field calculated by the magnetic field sensor and the magnetic field actually measured under the given combination of the position of the long straight conductor and the position parameter of the magnetic field sensor, and calculate the sum of the absolute values ​​of the errors as the objective function when the long straight conductor is at multiple different positions; The position parameter corresponding to the minimum value of the objective function is taken as the calibration result; wherein the position parameter includes: position coordinates and magnetic sensitive direction angle.

10. The magnetic field sensor measurement parameter calibration system according to claim 9, characterized in that: The magnetic field actually measured by the magnetic field sensor is obtained according to its output voltage signal combined with the sensitivity coefficient of the magnetic field sensor.

11. The magnetic field sensor measurement parameter calibration system according to claim 9, characterized in that: The magnetic field sensor calculates the magnetic field by forward calculation using the Biotsafar law.

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