Calibration device and calibration method for electromagnetic field distortion

Abstract

The invention provides a calibration device and method for electromagnetic field distortion, and the device comprises a tool support, an electromagnetic transmitter, an electromagnetic receiver, a tracking processing assembly, a computer, a handheld mobile device, and a high-precision MIMU sensor, and the electromagnetic receiver is fixed on the tool support or the handheld mobile device. The electromagnetic transmitter is fixed on the tool support, the electromagnetic transmitter and the electromagnetic receiver are arranged at an interval, the high-precision MIMU sensor is fixed on the handheld mobile device, and the tracking processing assembly is used for controlling the electromagnetic transmitter to generate a magnetic field covering the electromagnetic receiver and receiving electromagnetic measurement data transmitted by the electromagnetic receiver and MIMU measurement data transmitted by the high-precision MIMU sensor. And carrying out resolving processing on the electromagnetic measurement data and the MIMU measurement data, and transmitting a processing result to a computer for an operator to carry out electromagnetic field distortion calibration. The method has the beneficial effects that the electromagnetic field distortion influence caused by the metal environment can be corrected, and the method has the advantages of simple equipment, convenience in operation and high efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic positioning, and in particular to a calibration device and a calibration method for electromagnetic field distortion. Background Art

[0002] At present, the positioning and measurement methods of moving objects in a small range mainly include computer vision, inertia, radio frequency identification, ultrasonic measurement and electromagnetic measurement. The computer vision measurement method has high positioning accuracy, but the equipment price is high, and it cannot be positioned when there is an object blocking the object being measured and the camera; when inertial measurement is used, its measurement error accumulates over time; when radio frequency identification positioning technology is used, its positioning accuracy is low and cannot be applied to fields with high precision requirements; the accuracy of ultrasonic measurement will be affected in non-uniform media, and the hardware overhead is large and networking is inconvenient. Electromagnetic positioning technology detects the magnetic induction intensity in space to solve the position parameters and posture parameters of the target. Because its positioning effect is not affected by non-metallic objects, it is widely used in aiming display, medical surgery navigation, human-computer interaction, virtual reality, indoor robots, sports biomechanics, three-dimensional imaging and other fields.

[0003] The electromagnetic positioning system is usually composed of an electromagnetic transmitter, an electromagnetic receiver and related processing devices. The electromagnetic transmitter and the electromagnetic receiver are both composed of a coil frame and three mutually orthogonal coils. When the electromagnetic positioning system is working, the signal generating circuit supplies power to the three coils of the electromagnetic transmitter in a time-sharing manner, thereby establishing an instantaneous magnetic field in space. The three coils of the electromagnetic receiver respectively sense the magnetic field generated by the three coils of the electromagnetic transmitter to generate voltage signals. The voltage signal is related to the spatial position and attitude of the electromagnetic receiver coil, and can be expressed as a function of the spatial position. Based on the voltage signal generated by the electromagnetic receiver coil and the magnetic field distribution model generated by the electromagnetic transmitter coil, the three-degree-of-freedom position and three-degree-of-freedom attitude of the electromagnetic receiver relative to the electromagnetic transmitter can be calculated.

[0004] The electromagnetic positioning system is sensitive to the environment. When there are metals or electronic devices that can generate magnetic fields around the electromagnetic positioning system, the electromagnetic measurement data may be inaccurate. This is because the alternating magnetic field will generate eddy currents in nearby conductive materials. They generate secondary magnetic fields, which change the original magnetic field and cause errors in the system, resulting in inaccurate electromagnetic measurement data. At this time, the electromagnetic positioning system is difficult to use directly and needs to be calibrated for electromagnetic field distortion before use.

[0005] At present, the electromagnetic field distortion calibration method mainly fixes the electromagnetic transmitter and fixes the electromagnetic receiver on the translation table to move with the translation table, collects and saves the electromagnetic measurement data and the translation table measurement data, and finally calibrates the electromagnetic field distortion based on mathematical methods. The operation process of this method is complicated, especially difficult to implement in a small-scale application environment. Summary of the invention

[0006] The technical problem to be solved by the present invention is to realize the correction of the electromagnetic field distortion caused by the metal environment, and has the advantages of simple equipment, convenient operation and high efficiency. In order to overcome the defects of the above-mentioned prior art (or related technology), the present invention provides a calibration device and calibration method for electromagnetic field distortion.

[0007] The present invention provides a calibration device for electromagnetic field distortion, comprising a tooling bracket, an electromagnetic transmitter, an electromagnetic receiver, a tracking processing component, a computer, a handheld mobile device and a high-precision MIMU sensor, wherein the electromagnetic receiver is fixed on the tooling bracket or the handheld mobile device, the electromagnetic transmitter is fixed on the tooling bracket and spaced from the electromagnetic receiver, the high-precision MIMU sensor is fixed on the handheld mobile device, and the tracking processing component is electrically connected to the electromagnetic transmitter, the electromagnetic receiver, the computer and the high-precision MIMU sensor, respectively, and is used to control the electromagnetic transmitter to generate a magnetic field covering the electromagnetic receiver, and receive electromagnetic measurement data transmitted by the electromagnetic receiver and MIMU measurement data transmitted by the high-precision MIMU sensor, and perform solution processing on the electromagnetic measurement data and the MIMU measurement data and transmit the processing results to the computer for an operator to perform electromagnetic field distortion calibration.

[0008] Compared with the prior art, the electromagnetic field distortion calibration device of the present application has the following advantages: In the present invention, the fixed installation function of the electromagnetic transmitter and the electromagnetic receiver is realized by the tooling bracket, the electromagnetic transmitter generates a magnetic field through the tracking processing component control, and receives the electromagnetic measurement data transmitted by the electromagnetic receiver and the MIMU measurement data transmitted by the high-precision MIMU sensor. The calibration of the electromagnetic field distortion can be realized through computer processing. The whole device has the advantages of simple equipment, easy operation and high efficiency.

[0009] Furthermore, the above technical solution can assist in calibrating the electromagnetic field distortion by using the MIMU measurement data of the high-precision MIMU sensor, thereby solving the problems of complex electromagnetic field calibration and low measurement accuracy caused by electromagnetic field distortion. At the same time, after the electromagnetic field distortion is calibrated, the handheld mobile device (including the electromagnetic receiver and the high-precision MIMU sensor) can be used in another electromagnetic transmitter environment of the same specification to calibrate the electromagnetic distortion, or other electromagnetic receivers of the same specification can be directly used in the electromagnetic environment of the electromagnetic distortion calibration.

[0010] In a possible implementation manner, the electromagnetic transmitter and the electromagnetic receiver are detachably connected to the tooling bracket.

[0011] Compared with the prior art, the above technical solution can facilitate operators to disassemble the electromagnetic transmitter and the electromagnetic receiver for inspection and replacement.

[0012] In a possible implementation manner, the handheld mobile device and the electromagnetic receiver are detachably connected.

[0013] In a possible implementation, the tooling bracket, the housing of the high-precision MIMU sensor, and the handheld mobile device are all made of non-metallic materials.

[0014] Another technical solution of the present invention is to provide a calibration method for electromagnetic field distortion, which is applied to the above-mentioned calibration device and includes the following steps: Step S1, calibrating the electromagnetic field distortion at the electromagnetic receiver on the tooling bracket; Step S2, calibrating the relative distortion of discrete electromagnetic fields in the measurement environment; Step S3, establishing a posture correction model of relative distortion of the electromagnetic field; Step S4, calibrating the electromagnetic field distortion of multiple calibration positions and outputting the electromagnetic posture corrected by the posture correction model.

[0015] In a possible implementation, the step S1 includes: Step S11, building the test environment with non-metallic interference, fixing the electromagnetic transmitter and the electromagnetic receiver at the reserved positions of the tooling bracket respectively, and measuring and saving the first position information of the electromagnetic receiver relative to the electromagnetic transmitter; Step S12, in the application environment, fixing the electromagnetic transmitter and the electromagnetic receiver at the reserved positions of the tooling bracket respectively, and measuring and saving the second posture information of the electromagnetic receiver relative to the electromagnetic transmitter; Step S13: obtaining the electromagnetic field distortion at the electromagnetic receiver in the application environment according to the first posture information and the second posture information.

[0016] In a possible implementation, step S2 includes: Step S21, in the application environment, keep the electromagnetic transmitter fixed, remove the tooling bracket, fix the high-precision MIMU sensor and the electromagnetic receiver on the handheld mobile device, and calibrate the installation postures of the high-precision MIMU sensor and the electromagnetic receiver; Step S22, moving the handheld mobile device irregularly between a plurality of calibrated positions in the test environment; Step S23, collecting and recording the electromagnetic measurement data and MIMU measurement data of the handheld mobile device during movement, wherein the electromagnetic measurement data is the processing result of the electromagnetic field signal induced by the electromagnetic receiver after being transmitted to the tracking processing component and solved, and the processing result is the electromagnetic posture of the electromagnetic receiver relative to the electromagnetic transmitter, and the MIMU measurement data is the inertial posture; Step S24, calibrating the electromagnetic field relative distortion matrix at each of the calibration positions based on the measured electromagnetic posture, the inertial posture, and the installation posture of the high-precision MIMU sensor and the electromagnetic receiver, wherein the electromagnetic field relative distortion matrix is ​​represented as a discrete matrix of each of the calibration positions relative to the first point position.

[0017] In a possible implementation, step S3 includes: Step S31, obtaining the electromagnetic field relative distortion matrix and the electromagnetic measurement position data at each of the calibrated positions; Step S32, selecting a polynomial fitting method to fit the discrete electromagnetic field relative distortion matrix and the electromagnetic measurement position data to obtain fitting coefficients; Step S33: establishing a posture correction model of relative electromagnetic field distortion based on the fitting coefficients.

[0018] In a possible implementation, step S4 includes: Step S41, calculating the relative distortion of the electromagnetic field at the electromagnetic receiver in the application environment based on the posture correction model of the relative distortion of the electromagnetic field; Step S42, calculating the electromagnetic field distortion at the first point position in the electromagnetic receiver calibration process based on the electromagnetic field distortion at the installation position of the electromagnetic receiver and the relative electromagnetic field distortion; Step S43, calculating the relative distortion of the electromagnetic field at each calibration position during the calibration process, and establishing a posture correction model of the electromagnetic field distortion; Step S44: outputting the distortion-corrected electromagnetic posture at the current position based on the posture correction model of electromagnetic field distortion and the electromagnetic measurement data of the current position of the electromagnetic receiver. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the present invention when being fixed by a tooling bracket; Figure 2 A schematic diagram of electromagnetic distortion calibration by a handheld mobile device according to the present invention; Figure 3 is a flow chart of the steps of the present invention; Figure 4 is a specific flow chart of step S1 of the present invention; Figure 5 is a specific flow chart of step S2 of the present invention; Figure 6 This is a schematic diagram of the electromagnetic field positioning principle of the present invention; Figure 7 is a specific flow chart of step S3 of the present invention; Figure 8 is a specific flow chart of step S4 of the present invention; 1. Explanation of reference numerals: 1. tooling bracket; 2. electromagnetic transmitter; 3. electromagnetic receiver; 4. tracking processing component; 5. computer; 6. handheld mobile device; 7. high-precision MIMU sensor. DETAILED DESCRIPTION

[0020] First, those skilled in the art should understand that these implementations are only used to explain the technical principles of the embodiments of the present application, and are not intended to limit the protection scope of the embodiments of the present application. Those skilled in the art can make adjustments to them as needed to adapt to specific application scenarios.

[0021] The present application is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] See also Figure 1 and Figure 2 The embodiment of the present application discloses a calibration device for electromagnetic field distortion, including an electromagnetic transmitter 2, an electromagnetic receiver 3, a fixture bracket 1, a high-precision MIMU sensor 7, a handheld mobile device 6, a tracking processing component 4 and a computer 5, wherein the electromagnetic transmitter 2 is mainly composed of three mutually perpendicular coils, which are used to generate a magnetic field covering the electromagnetic receiver 3 after receiving the current transmitted by the tracking processing component 4; the electromagnetic receiver 3 is mainly composed of three mutually perpendicular coils, which are used to sense electromagnetic field signals; the fixture bracket 1 provides an installation position for the electromagnetic transmitter 2 and the electromagnetic receiver 3, which is used for the electromagnetic receiver 3 to measure the electromagnetic data at the position; the high-precision MIMU sensor 7 is used in electromagnetic distortion calibration, and is bonded to a handheld mobile device 6 with the electromagnetic receiver 3 to measure the current posture of the electromagnetic receiver 3; the tracking processing component 4 is composed of hardware and software, and is mainly used to control the electromagnetic transmitter 2 to generate an electromagnetic field, obtain the data transmitted by the electromagnetic receiver 3 for solution processing, and transmit the result to the computer 5; the computer 5 mainly processes the high-precision MIMU measurement data and the electromagnetic measurement data.

[0023] Continue to see Figure 2 The shape and specification of the handheld mobile device 6 can be selected according to the actual application. The electromagnetic receiver 3 and the high-precision MIMU sensor 7 are respectively bonded to the two ends of the handheld mobile device 6 by adhesive and can be quickly removed. The installation posture of the high-precision MIMU sensor 7 and the electromagnetic receiver 3 needs to be calibrated in advance.

[0024] See also Figure 3 The embodiment of the present application discloses a calibration method for electromagnetic field distortion, comprising: step S1, calibrating the electromagnetic field distortion at the electromagnetic receiver 3 on the tooling bracket 1; step S2, calibrating the discrete relative distortion of the electromagnetic field in the measurement environment; step S3, establishing a posture correction model of the relative distortion of the electromagnetic field; step S4, calibrating the electromagnetic field distortion of multiple calibration positions and outputting the electromagnetic posture corrected by the posture correction model.

[0025] See also Figure 4 , the first step is to calibrate the distortion at the electromagnetic receiver 3 on the fixture bracket 1: 1.1: First, build a non-metallic interference test environment, such as Figure 1 As shown, the electromagnetic transmitter 2 and the electromagnetic receiver 3 are respectively fixed at the reserved positions of the tooling bracket 1, and each device is connected in the working circuit, and the coordinate system of the electromagnetic receiver 3 at the position is measured and saved. Coordinate system relative to electromagnetic transmitter 2 The posture information of , the attitude matrix is ; 1.2: Use the above calibration device in the application environment, determine the installation position of the electromagnetic transmitter 2 in the application environment, and measure and save the position information of the electromagnetic receiver 3 at the installation position of the tooling bracket 1 relative to the electromagnetic transmitter 2 , the attitude matrix is ; 1.3: Calculate and save the electromagnetic distortion of the electromagnetic receiver 3 at the installation position of the tooling bracket 1 in the application environment .

[0026] See also Figure 5 , the second step is to calibrate the relative distortion of the discrete electromagnetic field in the measurement area: 2.1: Keep the electromagnetic transmitter 2 still, remove the fixture bracket 1, and bond the high-precision MIMU sensor 7 and the electromagnetic receiver 3 to both ends of the handheld mobile device 6 with adhesive, and calibrate the installation posture between the two. ; 2.2: Move the handheld mobile device 6 randomly and irregularly within the application environment, and try to ensure that it can reach all positions within the test environment. The whole process is completed within 15 seconds; 2.3: Collect and record electromagnetic measurement data and high-precision MIMU measurement data during the movement of the handheld mobile device 6, where the electromagnetic measurement data is the electromagnetic field signal induced by the electromagnetic receiver 3 and transmitted to the tracking processing component 4 for analysis, including the position in three directions and posture , is the position information of the electromagnetic receiver 3 relative to the electromagnetic transmitter 2, and the attitude matrix is (m=1,2…); The data output by the high-precision MIMU sensor 7 is the MIMU coordinate system Relative to the inertial coordinate system The attitude of the system, the attitude angle matrix is (m=1,2…), based on the installation posture of the high-precision MIMU sensor 7 and the electromagnetic receiver 3 calibrated in 1.1, the posture matrix of the electromagnetic receiver 3 relative to the inertial coordinate system is obtained (m=1,2…).

[0027] See also Figure 6 , Figure 6 It is a schematic diagram of electromagnetic positioning. Since the distance between the electromagnetic transmitter 2 and the electromagnetic receiver 3 is much larger than the size of the electromagnetic transmitter 2 itself, according to the Biot-Savart law, the two can be regarded as magnetic dipoles; The signal generating circuit supplies power to the coil of the electromagnetic transmitter 2 in a time-sharing manner, thereby establishing an instantaneous magnetic field in space. The magnetic field distribution is B ⃗ = μ 0 4π r 3 [ 3 m∙ ⃗ r∙ ⃗ r∙ ⃗ r 2 - m ⃗ ] The electromagnetic receiver 3 senses the magnetic field generated by the electromagnetic transmitter 2 to generate a voltage signal. The voltage signal is related to the spatial position and posture of the electromagnetic receiver 3 coil and can be expressed as a function of the spatial position. Based on the voltage signal generated by the electromagnetic receiver 3 coil and the magnetic field distribution model generated by the electromagnetic transmitter 2 coil, the coordinate system of the electromagnetic receiver 3 can be calculated. Relative electromagnetic transmitter 2 coordinate system The three-degree-of-freedom position and three degrees of freedom posture .

[0028] 2.4: Based on the electromagnetic and inertial information measured in 2.3 and the installation posture of the high-precision MIMU sensor 7 and the electromagnetic receiver 3, the relative distortion matrix of the electromagnetic field at different calibration positions of the electromagnetic receiver 3 in the application environment is calculated. , which represents the discrete matrix at each measurement position relative to the first point.

[0029] See also Figure 7 ,The third step is to establish the posture correction model of relative distortion of electromagnetic field: 3.1: Save the electromagnetic measurement position information and relative distortion matrix at each position in the second step, and convert the relative distortion matrix into relative distortion attitude angle ; 3.2: Select the polynomial fitting method to fit the discrete electromagnetic field relative to the distortion matrix and the electromagnetic measurement position data. Given the function , in is the electromagnetic measurement position data, y represents the relative distortion attitude angle, in order to calculate the coefficient , using the least squares method, establish the function: Q= ∑ i=1 n [ y i -( ∑ j=1 m a j x ji + a m+1 )] 2 Obtaining coefficients based on the minimum value principle , depending on the magnetic field distortion correction, second-order, third-order and fourth-order polynomials can be used; 3.3: Based on the fitting coefficients obtained in 3.2, establish an attitude correction model for relative distortion of the electromagnetic field.

[0030] See also Figure 8 , the fourth step is to calibrate the electromagnetic field distortion at each position and output the corrected electromagnetic attitude: 4.1: The position information measured by the electromagnetic receiver 3 at the tooling bracket 1 Substitute it into the attitude correction model of relative electromagnetic field distortion in 3.3 to calculate the relative electromagnetic field distortion at this position ; 4.2: Based on and Calculate the electromagnetic field distortion at the first point ; 4.3: Electromagnetic field distortion based on the first point position and the relative distortion of the electromagnetic field at each calibration position relative to the first point Calculate the electromagnetic field distortion at each location , and establish the posture correction model of electromagnetic field distortion using polynomial fitting method; 4.4: The attitude correction model based on electromagnetic field distortion and the electromagnetic receiver 3 measurement data output the electromagnetic attitude at the position after distortion correction.

[0031] In the description of the present application, the description with reference to the terms "one embodiment", "some embodiments", "in the present embodiment", "specific example", or "some examples" etc. means that the specific features, mechanisms, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, mechanisms, materials or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0032] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A calibration device for electromagnetic field distortion, characterized in that: The invention comprises a tooling support (1), an electromagnetic transmitter (2), an electromagnetic receiver (3), a tracking processing component (4), a computer (5), a handheld mobile device (6) and a high-precision MIMU sensor (7), wherein the electromagnetic receiver (3) is fixed on the tooling support (1) or the handheld mobile device (6), the electromagnetic transmitter (2) is fixed on the tooling support (1) and is spaced apart from the electromagnetic receiver (3), the high-precision MIMU sensor (7) is fixed on the handheld mobile device (6), and the tracking processing component (4) is fixed on the handheld mobile device (6). The electromagnetic transmitter (2), the electromagnetic receiver (3), the computer (5) and the high-precision MIMU sensor (7) are respectively electrically connected to the electromagnetic transmitter (2), the electromagnetic receiver (3), the computer (5) and the high-precision MIMU sensor (7), and are used to control the electromagnetic transmitter (2) to generate a magnetic field covering the electromagnetic receiver (3), receive electromagnetic measurement data transmitted by the electromagnetic receiver (3) and MIMU measurement data transmitted by the high-precision MIMU sensor (7), and perform calculation processing on the electromagnetic measurement data and the MIMU measurement data and transmit the processing results to the computer (5) for an operator to perform electromagnetic field distortion calibration.

2. The calibration device according to claim 1, characterized in that: The electromagnetic transmitter (2) and the electromagnetic receiver (3) are detachably connected to the tooling bracket (1).

3. The calibration device according to claim 1, characterized in that: The handheld mobile device (6) and the electromagnetic receiver (3) are detachably connected.

4. The calibration device according to claim 1, characterized in that: The tooling bracket (1), the housing of the high-precision MIMU sensor (7) and the handheld mobile device (6) are all made of non-metallic materials.

5. A calibration method for electromagnetic field distortion, characterized in that: The calibration device according to any one of claims 1 to 4 comprises the following steps: Step S1, calibrating the electromagnetic field distortion at the electromagnetic receiver (3) on the tooling support (1); Step S2, calibrating the relative distortion of discrete electromagnetic fields in the measurement environment; Step S3, establishing a posture correction model of relative electromagnetic field distortion; Step S4, calibrating the electromagnetic field distortion of multiple calibration positions and outputting the electromagnetic posture corrected by the posture correction model.

6. The calibration method according to claim 5, characterized in that: The step S1 comprises: Step S11, constructing the test environment with non-metallic interference, fixing the electromagnetic transmitter (2) and the electromagnetic receiver (3) at reserved positions of the tooling bracket (1), respectively, and measuring and saving the first position information of the electromagnetic receiver (3) relative to the electromagnetic transmitter (2); Step S12, in the application environment, fixing the electromagnetic transmitter (2) and the electromagnetic receiver (3) at reserved positions of the tooling support (1) respectively, and measuring and saving second position information of the electromagnetic receiver (3) relative to the electromagnetic transmitter (2); Step S13, obtaining the electromagnetic field distortion at the electromagnetic receiver (3) in the application environment according to the first posture information and the second posture information.

7. The calibration method according to claim 5, characterized in that: The step S2 comprises: Step S21, in the application environment, the electromagnetic transmitter (2) is kept fixed, the tooling bracket (1) is removed, the high-precision MIMU sensor (7) and the electromagnetic receiver (3) are fixedly connected to the handheld mobile device (6), and the installation postures of the high-precision MIMU sensor (7) and the electromagnetic receiver (3) are calibrated; Step S22, moving the handheld mobile device (6) irregularly between a plurality of calibrated positions in the test environment; Step S23, collecting and recording the electromagnetic measurement data and MIMU measurement data of the handheld mobile device (6) during movement, wherein the electromagnetic measurement data is the processing result of the electromagnetic field signal induced by the electromagnetic receiver (3) being transmitted to the tracking processing component (4) and then being solved and processed, and the processing result is the electromagnetic posture of the electromagnetic receiver (3) relative to the electromagnetic transmitter (2), and the MIMU measurement data is the inertial posture; Step S24, calibrating the electromagnetic field relative distortion matrix at each calibration position based on the measured electromagnetic posture, the inertial posture, and the installation posture of the high-precision MIMU sensor (7) and the electromagnetic receiver (3), wherein the electromagnetic field relative distortion matrix is ​​represented as a discrete matrix of each calibration position relative to the first point position.

8. The calibration method according to claim 5, characterized in that: The step S3 comprises: Step S31, obtaining the electromagnetic field relative distortion matrix and electromagnetic measurement position data at each of the calibrated positions; Step S32, selecting a polynomial fitting method to fit the discrete electromagnetic field relative distortion matrix and the electromagnetic measurement position data to obtain fitting coefficients; Step S33: establishing a posture correction model of relative electromagnetic field distortion based on the fitting coefficients.

9. The calibration method according to claim 5, characterized in that: The step S4 comprises: Step S41, calculating the relative distortion of the electromagnetic field at the electromagnetic receiver (3) in the application environment based on the posture correction model of the relative distortion of the electromagnetic field; Step S42, calculating the electromagnetic field distortion at the first point position during the calibration process of the electromagnetic receiver (3) based on the electromagnetic field distortion at the installation position of the electromagnetic receiver (3) and the relative electromagnetic field distortion; Step S43, calculating the relative distortion of the electromagnetic field at each calibration position during the calibration process, and establishing a posture correction model of the electromagnetic field distortion; Step S44: outputting the distortion-corrected electromagnetic posture at the current position based on the posture correction model of electromagnetic field distortion and the electromagnetic measurement data of the current position of the electromagnetic receiver (3).

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