Magnetic sensor calibration method

Abstract

The invention discloses a magnetic sensor calibration method, which obviously improves the calibration efficiency, relates to the technical field of magnetic sensor calibration, simplifies the traditional multi-position calibration (generally needing more than six positions) into only needing two specific positions, shortens the calibration time by more than 60%, and is particularly suitable for a batch production environment. The calibration precision is guaranteed, the sensitivity matrix and the zero offset parameter can be accurately solved by accurately controlling the magnetic field of the Helmholtz coil and the angle of the rotating platform and combining a reasonable error model, and the precision requirements of most application scenes are met. The system structure is simplified, only rotation control of two specific positions is needed, a complex three-dimensional rotation mechanism is not needed, and the system cost and the maintenance difficulty are reduced.

Description

Technical Field

[0001] This invention relates to the field of magnetic sensor calibration technology, and in particular to a magnetic sensor calibration method that requires only two specific locations. Background Technology

[0002] Magnetic sensors are widely used in navigation, positioning, industrial inspection, and medical devices, and their measurement accuracy directly affects the performance of the entire system. Due to factors such as manufacturing processes and material properties, magnetic sensors suffer from problems such as inconsistent sensitivity, zero-bias error, and non-orthogonality error. These errors must be corrected through calibration to improve measurement accuracy.

[0003] Traditional magnetic sensor calibration methods typically require rotating the sensor to multiple positions in three-dimensional space (such as the 6-position method, 8-position method, 24-position method, etc.), collecting a large amount of data, and then fitting calibration parameters using optimization algorithms such as the least squares method. These methods require manual placement or rotating a turntable to change positions or angles, making the calibration process cumbersome, time-consuming, and with limited accuracy. Especially in mass production scenarios, calibration efficiency becomes a production bottleneck.

[0004] In existing technologies, calibration systems based on Helmholtz coils are widely used, as they can generate a uniform and controllable standard magnetic field. However, traditional methods still require measurements at multiple locations or use with the aid of other calibration equipment. When using measurements at multiple locations, calibrating a sensor typically takes several minutes or even longer. Furthermore, when combined with other calibration equipment, the complexity of the rotating mechanisms and other components increases system cost and maintenance difficulty.

[0005] For example, patent document application number 202410348330.3 describes a magnetometer calibration device. This device uses a program-controlled AC power supply to drive a three-dimensional uniform magnetic field generator, producing a uniform magnetic field of arbitrary direction and magnitude in three-dimensional space. The automated dynamic adjustment of the magnetic field direction effectively replaces the physical rotation of the magnetometer, standardizing and normalizing the magnetometer calibration process. Compared to traditional calibration methods, this significantly saves time and greatly improves its feasibility for practical engineering applications. The introduction of a fluxgate magnetometer closed-loop control into the control system of the AC power-driven uniform magnetic field generator provides real-time monitoring and correction of magnetic field parameters, ensuring the stability and accuracy of the magnetic field, compared to open-loop control. Furthermore, this device has advantages such as simple structure, easy assembly, and low cost. However, this solution requires a fluxgate magnetometer as the "gold standard" for the magnetic field to accurately determine the direction and intensity of the magnetic field generated by the coil. It also suffers from drawbacks such as complex hardware structure.

[0006] Therefore, how to provide a magnetic sensor calibration method that can significantly improve calibration efficiency while ensuring calibration accuracy is an urgent technical problem that needs to be solved by those skilled in the art. Summary of the Invention

[0007] In view of the above problems, the present invention provides a magnetic sensor calibration method to overcome or at least partially solve the above problems. This method addresses the inefficiency of existing magnetic sensor calibration methods by requiring only two locations to complete the calibration, significantly improving calibration efficiency while maintaining calibration accuracy.

[0008] This invention provides the following solution:

[0009] A magnetic sensor calibration method, comprising: The magnetic sensor to be calibrated is fixed on a non-magnetic rotating platform at the center of the Helmholtz coil; A constant current is applied to the Helmholtz coil to generate a uniform magnetic field with a target strength and target direction. The magnetic sensor to be calibrated is rotated to the first calibration position using the non-magnetic rotating platform, and the first output data of the magnetic sensor to be calibrated is measured and recorded. The magnetic sensor to be calibrated is rotated to a second calibration position that differs from the first calibration position using the non-magnetic rotating platform, and the second output data of the magnetic sensor to be calibrated is measured and recorded. Based on a preset magnetic sensor error model, the calibration parameters of the magnetic sensor to be calibrated are calculated using the first output data and the second output data.

[0010] Preferably, the phase difference between the first calibration position and the second calibration position is 90°.

[0011] Preferably, the first calibration position is the 0° position where the sensitive axis of the magnetic sensor to be calibrated is parallel to the direction of the uniform magnetic field; the second calibration position is the 90° position where the sensitive axis of the magnetic sensor to be calibrated is perpendicular to the direction of the uniform magnetic field.

[0012] Preferably, the non-magnetic rotating platform includes a stepper motor, a controller, and a shielding housing. The stepper motor and the controller are used to control the rotation angle to 0° and 90°. The shielding housing is used to shield external electromagnetic interference.

[0013] Preferably, the calibration parameters include a sensitivity matrix and a zero bias vector.

[0014] Preferably, the magnetic sensor error model is represented by the following formula: V = M B + V0 In the formula: V represents the magnetic sensor output vector, B represents the magnetic field strength vector, M represents the sensitivity matrix to be determined, and V0 represents the zero bias vector to be determined.

[0015] Preferably, the method for solving the magnetic sensor error model includes: Let the magnetic field strength vector at the first calibration position be B1, and the output vector of the magnetic sensor to be calibrated be V1; let the magnetic field strength vector at the second calibration position be B2, and the output vector of the magnetic sensor to be calibrated be V2; Solve the system of equations: V1 = M B1 + V0 V2 = M B2 + V0 The sensitivity matrix M and the zero bias vector V0 are obtained.

[0016] Preferably, multiple data acquisitions are performed at the first calibration position and the second calibration position, and the average value of the multiple acquisition results is taken as the output data for that position.

[0017] Preferably, the uniform magnetic field generated by the Helmholtz coil is monitored in real time by a fluxgate magnetometer to ensure the uniformity and stability of the magnetic field.

[0018] Preferably, the system further includes a wireless communication module, through which the magnetic sensor to be calibrated is connected to the data acquisition module for wireless calibration; the data acquisition module is used to acquire the output data of the magnetic sensor to be calibrated.

[0019] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects: This application provides a magnetic sensor calibration method that significantly improves calibration efficiency, simplifying traditional multi-position calibration (typically requiring more than six positions) to only two specific positions, reducing calibration time by more than 60%, making it particularly suitable for mass production environments. Calibration accuracy is guaranteed; by precisely controlling the magnetic field of the Helmholtz coil and the angle of the rotating platform, combined with a reasonable error model, the sensitivity matrix and zero-bias parameters can be accurately calculated, meeting the accuracy requirements of most application scenarios. The system structure is simplified, requiring only rotation control at two specific positions, eliminating the need for complex three-dimensional rotation mechanisms, thus reducing system cost and maintenance difficulty. It boasts a high degree of automation; the entire calibration process can be automatically completed by the control processing unit, including position control, data acquisition, parameter calculation, and result storage, reducing manual intervention. It is highly scalable, easily integrating wireless communication modules to achieve wireless calibration of wireless sensors; it can be expanded into a multi-station system to calibrate multiple sensors simultaneously, further improving batch calibration efficiency.

[0020] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0022] Figure 1 This is a flowchart of the magnetic sensor calibration method provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of the non-magnetic rotating platform provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the overall device used in the embodiments of the present invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0024] See Figure 1 This invention provides a magnetic sensor calibration method, such as... Figure 1 As shown, the method may include: The magnetic sensor to be calibrated is fixed on a non-magnetic rotating platform at the center of the Helmholtz coil; A constant current is applied to the Helmholtz coil to generate a uniform magnetic field with a target strength and target direction. The magnetic sensor to be calibrated is rotated to the first calibration position using the non-magnetic rotating platform, and the first output data of the magnetic sensor to be calibrated is measured and recorded. The magnetic sensor to be calibrated is rotated to a second calibration position that differs from the first calibration position using the non-magnetic rotating platform, and the second output data of the magnetic sensor to be calibrated is measured and recorded. Based on a preset magnetic sensor error model, the calibration parameters of the magnetic sensor to be calibrated are calculated using the first output data and the second output data.

[0025] The magnetic sensor calibration method provided in this application involves fixing the magnetic sensor to be calibrated on a rotatable non-magnetic platform at the center of a Helmholtz coil; passing a constant current through the Helmholtz coil to generate a uniform magnetic field of known intensity and direction; acquiring the output data of the magnetic sensor at two positions with a phase difference; and calculating the sensitivity matrix and zero-bias parameter based on a preset magnetic sensor error model using the data from the two positions to complete the calibration. This method simplifies traditional multi-position calibration to only two specific positions and eliminates the need for standard data acquisition mechanisms such as fluxgate magnetometers. It significantly improves calibration efficiency while maintaining calibration accuracy, making it particularly suitable for rapid calibration requirements in mass production.

[0026] In practical applications, the first calibration position, the second calibration position, and the phase difference can be determined according to actual needs. For example, in one implementation, to ensure precise adjustment, the phase difference between the first calibration position and the second calibration position can be 90°. Further, the first calibration position is the 0° position where the sensitive axis of the magnetic sensor to be calibrated is parallel to the direction of the uniform magnetic field; the second calibration position is the 90° position where the sensitive axis of the magnetic sensor to be calibrated is perpendicular to the direction of the uniform magnetic field.

[0027] In this embodiment, a non-magnetic rotating platform is used to adjust the position of the magnetic sensor to be calibrated. In order to achieve precise adjustment, this embodiment can provide that the non-magnetic rotating platform includes a stepper motor, a controller, and a shielding housing. The stepper motor and the controller are used to control the rotation angle to 0° and 90°; the shielding housing is used to shield external electromagnetic interference.

[0028] In specific implementation, embodiments of this application may provide calibration parameters including a sensitivity matrix and a zero-bias vector. Further, the magnetic sensor error model is represented by the following equation: V = M B + V0 In the formula: V represents the magnetic sensor output vector, B represents the magnetic field strength vector, M represents the sensitivity matrix to be determined, and V0 represents the zero bias vector to be determined.

[0029] The method for solving the magnetic sensor error model includes: Let the magnetic field strength vector at the first calibration position be B1, and the output vector of the magnetic sensor to be calibrated be V1; let the magnetic field strength vector at the second calibration position be B2, and the output vector of the magnetic sensor to be calibrated be V2; Solve the system of equations: V1 = M B1 + V0 V2 = M B2 + V0 The sensitivity matrix M and the zero bias vector V0 are obtained.

[0030] To further ensure the accuracy of the acquired output data, embodiments of this application may provide multiple data acquisitions at the first calibration position and the second calibration position, and take the average of the multiple acquisition results as the output data at that position.

[0031] To further ensure the accuracy of the generated magnetic field, embodiments of this application can provide real-time monitoring of the uniform magnetic field generated by the Helmholtz coil through fluxgate magnetization to ensure the uniformity and stability of the magnetic field.

[0032] To achieve wireless calibration, this application embodiment may also provide a wireless communication module, through which the magnetic sensor to be calibrated is communicatively connected to the data acquisition module to achieve wireless calibration; the data acquisition module is used to acquire the output data of the magnetic sensor to be calibrated.

[0033] The magnetic sensor calibration method provided in this application embodiment will be described in detail below with reference to a calibration system in one implementation.

[0034] This application provides a rapid two-position calibration system for a magnetic sensor, which includes a Helmholtz coil, a non-magnetic rotating platform, a magnetic field monitoring module, a data acquisition module, a control processing unit, and a shielding housing.

[0035] The Helmholtz coil consists of a pair of coaxial, circular coils of the same radius. When current is passed through them in the same direction, a highly uniform magnetic field is generated in the central region of the coil. The Helmholtz coil is connected to a precision current source, and the magnitude and direction of the current are controlled by a control processing unit.

[0036] The non-magnetic rotating platform is located at the center of the Helmholtz coil and is driven by a stepper motor, achieving a rotational accuracy better than 0.1°. A sensor clamp is provided on the rotating platform to secure the magnetic sensor to be calibrated. The platform is made of non-magnetic materials (such as aluminum alloy or plastic) to avoid interference with the magnetic field.

[0037] The magnetic field monitoring module includes a high-precision fluxgate sensor, which monitors the magnetic field strength in the central region of the Helmholtz coil in real time and feeds the data back to the control processing unit to form a closed-loop control and ensure magnetic field stability.

[0038] The data acquisition module includes a multi-channel ADC and a high-precision signal conditioning circuit for acquiring the output signal of the magnetic sensor. In a preferred embodiment, the magnetic sensor communicates with the data acquisition module via a wireless communication module (such as Bluetooth) to achieve wireless calibration, avoiding interference and operational inconvenience introduced by cables.

[0039] The control processing unit is an industrial control computer or embedded system that runs calibration control software, coordinates the work of each module, and executes calibration algorithms.

[0040] The shielding shell is a double-layer electromagnetic shielding structure, with a high magnetic permeability material inside and a high electrical conductivity material outside, effectively shielding against external electromagnetic interference.

[0041] The magnetic sensor can communicate with the data acquisition module via a wireless communication module to achieve wireless calibration.

[0042] Combination Figure 3 The calibration method of the present invention for the overall equipment and materials shown includes the following steps: Step 1: System Initialization The magnetic sensor 7 to be calibrated is fixed on the fixture of the rotating platform 2, ensuring that the relative position of the magnetic sensor to be calibrated and the fixture is fixed. Preferably, the triaxial coil 1, the rotating platform 2, and the magnetic sensor 7 can be placed as a whole in the magnetic field shielding cavity 6 to further avoid interference from the surrounding background magnetic field.

[0043] Step 2: Establishing the magnetic field The control processing unit 5 controls a precision current source to supply a constant current I to the Helmholtz coil 1, generating a uniform magnetic field B at the center of the coil. The magnetic field monitoring module 3 monitors the magnetic field strength in real time to ensure that the magnetic field is stable at a preset value (e.g., 50 μT).

[0044] Step 3: First position measurement The control processing unit 5 controls the rotating platform 2 to rotate the magnetic sensor 7 to the 0° position (i.e., the sensor's sensitive axis is parallel to the magnetic field direction). After waiting 100ms for the system to stabilize, the data acquisition module 4 acquires the output signal V1 of the magnetic sensor 7, continuously acquiring it 10 times and taking the average value as the final V1. At the same time, the magnetic field strength B1 measured by the magnetic field monitoring module 3 is recorded.

[0045] Step 4: Second position measurement The control processing unit 5 controls the rotating platform 2 to rotate the magnetic sensor 7 to a 90° position (i.e., the sensor's sensitive axis is perpendicular to the magnetic field direction). After stabilization, the output signal V2 is acquired, averaged, and the magnetic field strength B2 is recorded.

[0046] Step 5: Parameter Calculation The error model of the magnetic sensor is: V = M B + V0 Where V is a 3D output vector, B is a 3D magnetic field vector, M is a 3×3 sensitivity matrix, and V0 is a 3D zero bias vector.

[0047] A system of equations was established based on measurement data from two locations: V1 = M B1 + V0 V2 = M B2 + V0 Since the magnetic field direction generated by the Helmholtz coil is known, let B1 = [B0, 0, 0]^T and B2 = [0, B0, 0]^T, where B0 is the scalar value of the magnetic field intensity. Substituting B1 and B2 into the system of equations, the solution can be obtained as follows: The estimated value of M can be calculated, and V0 = (V1 + V2) / 2 - M [B0 / 2, B0 / 2, 0]^T Step 6: Result storage Write the calculated sensitivity matrix M and zero-bias vector V0 into the internal memory (such as EEPROM) of the magnetic sensor 7, or upload them to the database for storage. At the same time, quality indicators such as calibration residuals can be calculated to determine whether the calibration is qualified.

[0048] In an extended embodiment, the system can be configured as a multi-station calibration station. The rotating platform 2 is a circular turntable, and 4 sensor stations are evenly distributed on the edge. During operation, the turntable rotates 90° each time, so that one station enters the calibration position. When a sensor calibration is completed, the turntable rotates to transfer the next sensor into the calibration position, and at the same time, the manipulator removes the calibrated sensor and inserts a new sensor. In this way, continuous automated calibration can be achieved, and dozens of sensors can be calibrated per hour. This method is applicable to batch rapid calibration of magnetoresistive sensors such as AMR, GMR, and TMR.

[0049] Experimental verification: Calibrate a certain type of AMR magnetic sensor using this method. The calibration time for each sensor is about 12 seconds (the traditional multi-position method requires more than 40 seconds). After calibration, the measurement error of the sensor within the range of ±100 μT is less than 1%, meeting the requirements of most applications.

[0050] In summary, the magnetic sensor calibration method provided in this application significantly improves calibration efficiency, simplifying traditional multi-position calibration (typically requiring more than 6 positions) to only 2 specific positions, reducing calibration time by more than 60%, making it particularly suitable for mass production environments. Calibration accuracy is guaranteed; by precisely controlling the magnetic field of the Helmholtz coil and the angle of the rotating platform, combined with a reasonable error model, the sensitivity matrix and zero-bias parameters can be accurately calculated, meeting the accuracy requirements of most application scenarios. The system structure is simplified, requiring only rotation control at two specific positions, eliminating the need for complex three-dimensional rotation mechanisms, thus reducing system cost and maintenance difficulty. It boasts a high degree of automation; the entire calibration process can be automatically completed by the control processing unit, including position control, data acquisition, parameter calculation, and result storage, reducing manual intervention. It is highly scalable, easily integrating wireless communication modules to achieve wireless calibration of wireless sensors; it can be expanded into a multi-station system to calibrate multiple sensors simultaneously, further improving batch calibration efficiency.

[0051] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0052] As can be seen from the above description of the embodiments, those skilled in the art can clearly understand that this application can be implemented by means of software plus necessary general-purpose hardware platforms. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in various embodiments or some parts of the embodiments of this application.

[0053] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for system or system embodiments, since they are basically similar to method embodiments, the description is relatively simple, and relevant parts can be referred to the descriptions in the method embodiments. The systems and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0054] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A method for calibrating a magnetic sensor, characterized in that, include: The magnetic sensor to be calibrated is fixed on a non-magnetic rotating platform at the center of the Helmholtz coil; A constant current is applied to the Helmholtz coil to generate a uniform magnetic field with a target strength and target direction. The magnetic sensor to be calibrated is rotated to the first calibration position using the non-magnetic rotating platform, and the first output data of the magnetic sensor to be calibrated is measured and recorded. The magnetic sensor to be calibrated is rotated to a second calibration position that differs from the first calibration position using the non-magnetic rotating platform, and the second output data of the magnetic sensor to be calibrated is measured and recorded. Based on a preset magnetic sensor error model, the calibration parameters of the magnetic sensor to be calibrated are calculated using the first output data and the second output data.

2. The magnetic sensor calibration method according to claim 1, characterized in that, The phase difference between the first calibration position and the second calibration position is 90°.

3. The magnetic sensor calibration method according to claim 2, characterized in that, The first calibration position is the 0° position where the sensitive axis of the magnetic sensor to be calibrated is parallel to the direction of the uniform magnetic field; the second calibration position is the 90° position where the sensitive axis of the magnetic sensor to be calibrated is perpendicular to the direction of the uniform magnetic field.

4. The magnetic sensor calibration method according to claim 2, characterized in that, The non-magnetic rotating platform includes a stepper motor, a controller, and a shielding housing. The stepper motor and the controller are used to control the rotation angle to 0° and 90°. The shielding housing is used to shield external electromagnetic interference.

5. The magnetic sensor calibration method according to claim 1, characterized in that, The calibration parameters include the sensitivity matrix and the zero bias vector.

6. The magnetic sensor calibration method according to claim 5, characterized in that, The error model of the magnetic sensor is expressed by the following equation: V = M B + V0 In the formula: V represents the magnetic sensor output vector, B represents the magnetic field strength vector, M represents the sensitivity matrix to be determined, and V0 represents the zero bias vector to be determined.

7. The magnetic sensor calibration method according to claim 6, characterized in that, The method for solving the magnetic sensor error model includes: Let the magnetic field strength vector at the first calibration position be B1, and the output vector of the magnetic sensor to be calibrated be V1; let the magnetic field strength vector at the second calibration position be B2, and the output vector of the magnetic sensor to be calibrated be V2; By solving the system of equations: V1 = M B1 + V0 V2 = M B2 + V0 The sensitivity matrix M and the zero bias vector V0 are obtained.

8. The magnetic sensor calibration method according to claim 1, characterized in that, Multiple data acquisitions are performed at the first and second calibration positions, and the average value of the multiple acquisitions is taken as the output data for that position.

9. The magnetic sensor calibration method according to claim 1, characterized in that, The uniform magnetic field generated by the Helmholtz coil is monitored in real time using a fluxgate magnetometer to ensure the uniformity and stability of the magnetic field.

10. The magnetic sensor calibration method according to claim 1, characterized in that, It also includes a wireless communication module, through which the magnetic sensor to be calibrated is connected to the data acquisition module to achieve wireless calibration; the data acquisition module is used to collect the output data of the magnetic sensor to be calibrated.

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