Optical fiber inertial navigation magnetic shielding test and compensation method and medium

Abstract

This invention discloses a method for testing and compensating the magnetic shielding effect of fiber optic inertial navigation systems, belonging to the field of magnetic shielding testing and compensation for inertial measurement units. The method includes: generating a controllable magnetic field using a triaxial Helmholtz coil; measuring the magnetic field strength and calculating the shielding effectiveness using internal and external magnetometers; acquiring multiple sets of test data under different magnetic field conditions to establish a mathematical model of the residual magnetic field and the output errors of the gyroscope and accelerometer; calibrating the sensitivity coefficient and constant zero bias using the least squares method; and measuring the internal residual magnetic field in real time during actual operation, calculating the estimated error, and subtracting it from the original output to achieve error compensation. This invention can quantitatively evaluate the magnetic shielding effect and significantly improve the output accuracy of fiber optic inertial navigation systems under magnetic field interference environments through error modeling and real-time compensation.

Description

Technical Field

[0001] This invention relates to the field of magnetic shielding effect testing and compensation technology for fiber optic inertial measurement units, specifically to a method and medium for testing and compensating magnetic shielding of fiber optic inertial navigation systems. Background Technology

[0002] Fiber optic inertial navigation (INS), as a next-generation INS, offers numerous advantages over laser INS. Its accuracy is comparable to that of conventional laser INS, while its weight, size, power consumption, and price are significantly reduced. With technological advancements, the accuracy of fiber optic INS continues to improve. In the near future, we will be able to obtain fiber optic INS with even higher accuracy and lower weight, size, power consumption, and price. Fiber optic gyroscopes and accelerometers, as the core measurement devices of fiber optic INS, are susceptible to environmental factors that can lead to reduced accuracy. External magnetic fields are a significant influencing factor; for fiber optic gyroscopes without any shielding or compensation, the bias error caused by the Earth's magnetic field alone can reach the order of 1° / h. Therefore, it is necessary to test and compensate for the magnetic shielding effectiveness of fiber optic INS to improve its accuracy. Summary of the Invention

[0003] This invention provides a method and medium for testing and compensating magnetic shielding of fiber optic inertial navigation systems. The method tests the magnetic shielding effect of the fiber optic inertial navigation system and establishes an error model based on the test data to compensate for the output of the fiber optic inertial navigation system, thereby further improving the accuracy of the fiber optic inertial navigation system.

[0004] In a first aspect, the present invention provides a method for testing and compensating magnetic shielding of optical fiber inertial navigation systems, comprising: A controllable magnetic field environment is constructed by generating a uniform magnetic field with known intensity, direction and frequency in the central region using a triaxial Helmholtz coil to simulate external magnetic field disturbances. Reference probes were placed at key locations outside the magnetic shielding shell of the fiber optic inertial navigation system under test and near the internal sensitive components to simultaneously measure the strength of the externally applied magnetic field and the strength of the internal residual magnetic field. Based on the measured external magnetic field strength and internal residual magnetic field strength, the shielding effectiveness of the magnetic shielding structure is calculated, and the shielding effect under various axial and magnetic field conditions is evaluated. Multiple sets of test data under different magnetic field conditions were obtained, and a mathematical model was established between the internal residual magnetic field strength and the output error of the fiber optic gyroscope and the output error of the accelerometer. Based on the mathematical model, the sensitivity coefficients and constant zero bias of the fiber optic gyroscope and accelerometer to the magnetic field component were calibrated using a system identification method. During actual operation of the fiber optic inertial navigation system, the internal residual magnetic field strength is measured in real time by the built-in magnetometer. The estimation error under the current magnetic field is calculated using the model parameters obtained from the calibration. The estimation error is then subtracted from the original output of the sensor to obtain the compensated output signal, which is used for subsequent navigation calculations.

[0005] In some instances, by Achieve shielding effectiveness The shielding effectiveness values ​​were calculated for the X, Y, and Z axes, and for different magnetic field strengths and frequencies. Apply a magnetic field strength to the outside. The value represents the internal residual magnetic field strength.

[0006] In some instances, by Establish fiber optic gyroscope output error ,in, , , These are the three axial components of the internal residual magnetic field. , , These are the sensitivity coefficients of the fiber optic gyroscope to the three magnetic field components. The constant zero bias is independent of the magnetic field. i The X, Y, and Z axes represent the fiber optic gyroscope.

[0007] In some instances, by Establish an accelerometer output error model ,in, , , These are the three axial components of the internal residual magnetic field. , , These are the sensitivity coefficients of the accelerometer to the three magnetic field components, respectively. The constant zero bias is independent of the magnetic field. j The X, Y, and Z axes represent the accelerometer.

[0008] In some instances, the method of calibrating the sensitivity coefficients and constant zero bias of the fiber optic gyroscope and accelerometer to the magnetic field component using a system identification method includes: The least squares method is used to construct multiple sets of test data into a matrix form. ,in, To output the error vector, , This is a matrix of magnetic field measurements. , The parameter vector to be identified, The residual vector; The least squares solution for the parameter vector is: .

[0009] In some instances, the constructed controllable magnetic field environment includes both DC and AC magnetic fields, covering different frequency ranges, to simulate complex external magnetic field interference environments.

[0010] In some instances, critical external locations include seams, openings, and corners of the magnetically shielded enclosure, while locations near internal sensitive components include the mounting sites of fiber optic gyroscopes and accelerometers.

[0011] In some instances, when establishing a mathematical model, the fiber optic inertial navigation system under test is fixed on a high-precision three-axis turntable. By changing the orientation of the turntable, the Earth's gravity component is separated, and the magnetic sensitivity error of the accelerometer is extracted. By providing a known angular rate through the turntable, the magnetic sensitivity error and constant drift of the fiber optic gyroscope are separated.

[0012] In some instances, the output signal after real-time compensation is represented as: , ,in, and These are the raw outputs from the fiber optic gyroscope and the accelerometer, respectively. and This represents the estimated error calculated based on real-time magnetic field measurements and the calibration model.

[0013] In a second aspect, the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of any of the methods described above.

[0014] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects: A method for testing and compensating for the magnetic shielding effect of fiber optic inertial navigation systems (FISs) is designed. This method can evaluate the quality of the magnetic shielding structure design and identify the optimal design through comparative analysis. Furthermore, it can establish a model between the residual magnetic field strength and the output error of the FISs based on test data. Once the error model is obtained, it can be used to compensate for the error in subsequent outputs, thereby further improving the output accuracy of the FISs. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the method provided in an embodiment of the present invention. Detailed Implementation

[0017] 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 some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] In the following description, specific embodiments of the invention will be illustrated with reference to steps and symbols performed by one or more computers, unless otherwise stated. Therefore, these steps and operations will be referred to several times as being performed by a computer, and computer execution as referred to herein includes operations by a computer processing unit representing electronic signals of data in a structured format. This operation transforms the data or maintains it at a location in the computer's memory system, which can be reconfigured or otherwise alter the operation of the computer in a manner well known to those skilled in the art. The data structure maintained by the data is the physical location of the memory, which has specific characteristics defined by the data format. However, the principles of the invention described above are not intended to be limiting, and those skilled in the art will understand that many of the following steps and operations can also be implemented in hardware.

[0019] The terms "module" or "unit" as used herein can be considered as software objects executing on the computing system. Different components, modules, engines, and services described herein can be considered as implementations on the computing system. The apparatus and methods described herein are preferably implemented in software, but can also be implemented in hardware, both of which are within the scope of this invention.

[0020] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this specification means the presence of features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. It should be understood that when we say an element is “connected” or “coupled” to another element, it can be directly connected or coupled to the other element, or there may be intermediate elements. Furthermore, “connected” or “coupled” as used herein can include wireless connections or wireless coupling. The term “and / or” as used herein includes all or any units and all combinations of one or more associated listed items.

[0021] This invention proposes a novel technology for testing and compensating the magnetic shielding effect of fiber optic inertial navigation systems, which mainly includes the following: 1. Use a triaxial Helmholtz coil to generate a magnetic field with known strength and direction, use a magnetometer to measure the magnetic field strength inside and outside the magnetic shielding structure, and calculate the shielding effectiveness.

[0022] 2. Perform multiple tests by changing the strength and direction of the generated magnetic field.

[0023] 3. Establish the relationship between residual magnetic field strength and gyroscope output error and accelerometer output error based on test data.

[0024] 4. Subtract the estimation error from the original sensor output and send the corrected output into the navigation solution algorithm.

[0025] In this embodiment of the invention, a method for testing and compensating magnetic shielding of optical fiber inertial navigation systems is provided, such as... Figure 1 As shown, it includes the following steps: S101: Construct a controllable magnetic field environment by generating a uniform magnetic field with known intensity, direction and frequency in the central region using a triaxial Helmholtz coil to simulate external magnetic field disturbances; S102: Reference probes are placed at key locations outside the magnetic shielding shell of the fiber optic inertial navigation system under test and near the internal sensitive components to simultaneously measure the strength of the externally applied magnetic field and the strength of the internal residual magnetic field. S103: Calculate the shielding effectiveness of the magnetic shielding structure based on the measured external applied magnetic field strength and internal residual magnetic field strength, and evaluate the shielding effect under various axial and magnetic field conditions. S104: Acquire multiple sets of test data under different magnetic field conditions, and establish a mathematical model between the internal residual magnetic field strength and the output error of the fiber optic gyroscope and the output error of the accelerometer. S105: Based on a mathematical model, the sensitivity coefficients and constant zero bias of the fiber optic gyroscope and accelerometer to the magnetic field component are calibrated using a system identification method. S106: During actual operation of the fiber optic inertial navigation system, the internal residual magnetic field strength is measured in real time by the built-in magnetometer. The estimation error under the current magnetic field is calculated using the model parameters obtained from the calibration. The estimation error is then subtracted from the original output of the sensor to obtain the compensated output signal, which is used for subsequent navigation calculations.

[0026] In this embodiment of the invention, a triaxial Helmholtz coil system is used to generate a uniform DC or AC magnetic field of known strength and direction in its central region, serving as an external magnetic field perturbation to simulate fiber optic inertial navigation. The magnetic field strength is then measured using a high-precision, calibrated triaxial fluxgate magnetometer or Hall effect magnetometer as a reference probe.

[0027] Place the reference probe firmly against a key location on the outside of the magnetic shielding shell of the inertial navigation system under test, and measure the external magnetic field applied at that point. Inside the shielding shell, close to the sensitive element, another high-precision triaxial magnetometer probe is placed to measure the residual magnetic field inside the shielded enclosure. .

[0028] Then, the shielding effectiveness is calculated. Shielding effectiveness is a core indicator for measuring the magnetic shielding effect, usually expressed in decibels. The specific calculation formula is as follows:

[0029] For each axis (X, Y, Z), each magnetic field strength, and each frequency, the shielding effectiveness (SE) is calculated separately. Evaluating the magnetic shielding effect in each direction using shielding effectiveness can guide the design of magnetic shielding structures. If the shielding effectiveness is high but the residual magnetic field is small, and the residual magnetic field cannot be completely eliminated through magnetic shielding design, then error modeling and compensation are necessary.

[0030] An error model was established based on the above test data, and the residual magnetic field was established. With fiber optic gyroscope output error and accelerometer output error The mathematical model between them.

[0031] For accelerometers: In order to separate constant zero bias from magnetic sensitivity error, the IMU is usually fixed on a high-precision three-axis turntable and excited by an external magnetic field in different orientations to change the Earth's gravitational component, thereby extracting the magnetic sensitivity error of the accelerometer.

[0032] For fiber optic gyroscopes, magnetic sensitivity error and constant drift can be separated based on the known angular rate provided by a high-precision three-axis turntable.

[0033] Fiber optic gyroscope output error The model is as follows:

[0034] in , , This represents the sensitivity coefficient of the gyroscope to the three magnetic field components. The constant zero bias of the gyroscope is independent of the magnetic field.

[0035] Similarly, accelerometer output error The model is as follows:

[0036] in , , This represents the sensitivity coefficient of the accelerometer on this axis to the three magnetic field components. This is the constant zero bias of the accelerometer on this axis, independent of the magnetic field.

[0037] Write the N equations in matrix form:

[0038] in: ,

[0039] The goal of least squares is to find To minimize the sum of squared residuals: if If it is reversible, then the solution is: .

[0040] The specific implementation steps can be divided into three steps: calibration, error calculation, and real-time compensation. The specific implementation process is as follows: The detailed calibration process is as follows: 1. Place the fiber optic IMU with an internal magnetometer inside a precision turntable and a temperature chamber.

[0041] 2. Place the entire system in a controllable magnetic field environment (Helmholtz coil). 3. Under each magnetic field condition, record the raw output of the IMU and the zero bias of the IMU.

[0042] Calculation error: Using system identification techniques such as least squares method, based on a large number of ( , , ) data points, fit the compensation model parameters for each gyroscope and accelerometer ( , , , ).

[0043] Real-time compensation technology: During actual operation of the inertial navigation system, the internal magnetic intensity and measured values ​​are measured in real time. ; Using the calibrated model parameters, the estimation error of each gyroscope and accelerometer under the current magnetic field is calculated in real time. and Subtract the estimation error from the original sensor data:

[0044]

[0045] Corrected and The input is then fed into the navigation solution algorithm (such as the inertial navigation equation or the Kalman filter).

[0046] Those skilled in the art will understand that all or part of the steps in the various methods of the above embodiments can be performed by instructions, or by instructions controlling related hardware. These instructions can be stored in a computer-readable storage medium and loaded and executed by a processor.

[0047] Therefore, embodiments of the present invention provide a computer-readable storage medium having a computer program stored thereon, the computer program being loaded by a processor to execute the steps of any method provided in the embodiments of the present invention.

[0048] For details on the implementation of each of the above operations, please refer to the previous examples, which will not be repeated here.

[0049] The computer-readable storage medium may include: read-only memory (ROM), random access memory (RAM), disk or optical disk, etc.

[0050] Since the computer program stored in the computer-readable storage medium can execute the steps of any of the methods provided in the embodiments of the present invention, the beneficial effects that any of the methods provided in the embodiments of the present invention can achieve can be realized, as detailed in the preceding embodiments, and will not be repeated here.

[0051] The foregoing has provided a detailed description of the fiber optic inertial navigation magnetic shielding testing and compensation method and medium provided by the embodiments of the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for testing and compensating magnetic shielding of fiber optic inertial navigation systems, characterized in that, include: A controllable magnetic field environment is constructed by generating a uniform magnetic field with known intensity, direction and frequency in the central region using a triaxial Helmholtz coil to simulate external magnetic field disturbances. Reference probes were placed at key locations outside the magnetic shielding shell of the fiber optic inertial navigation system under test and near the internal sensitive components to simultaneously measure the strength of the externally applied magnetic field and the strength of the internal residual magnetic field. Based on the measured external magnetic field strength and internal residual magnetic field strength, the shielding effectiveness of the magnetic shielding structure is calculated, and the shielding effect under various axial and magnetic field conditions is evaluated. Multiple sets of test data under different magnetic field conditions were obtained, and a mathematical model was established between the internal residual magnetic field strength and the output error of the fiber optic gyroscope and the output error of the accelerometer. Based on the mathematical model, the sensitivity coefficients and constant zero bias of the fiber optic gyroscope and accelerometer to the magnetic field component were calibrated using a system identification method. During actual operation of the fiber optic inertial navigation system, the internal residual magnetic field strength is measured in real time by the built-in magnetometer. The estimation error under the current magnetic field is calculated using the model parameters obtained from the calibration. The estimation error is then subtracted from the original output of the sensor to obtain the compensated output signal, which is used for subsequent navigation calculations.

2. The method according to claim 1, characterized in that, Depend on Achieve shielding effectiveness The shielding effectiveness values ​​were calculated for the X, Y, and Z axes, and for different magnetic field strengths and frequencies. Apply a magnetic field strength to the outside. The value represents the internal residual magnetic field strength.

3. The method according to claim 1 or 2, characterized in that, Depend on Establish fiber optic gyroscope output error ,in, , , These are the three axial components of the internal residual magnetic field. , , These are the sensitivity coefficients of the fiber optic gyroscope to the three magnetic field components. The constant zero bias is independent of the magnetic field. i The X, Y, and Z axes represent the fiber optic gyroscope.

4. The method according to claim 3, characterized in that, Depend on Establish an accelerometer output error model ,in, , , These are the three axial components of the internal residual magnetic field. , , These are the sensitivity coefficients of the accelerometer to the three magnetic field components, respectively. The constant zero bias is independent of the magnetic field. j The X, Y, and Z axes represent the accelerometer.

5. The method according to claim 4, characterized in that, The method of calibrating the sensitivity coefficients and constant zero bias of the fiber optic gyroscope and accelerometer to the magnetic field component using a system identification method includes: The least squares method is used to construct multiple sets of test data into a matrix form. ,in, To output the error vector, , This is a matrix of magnetic field measurements. , The parameter vector to be identified, The residual vector; The least squares solution for the parameter vector is: .

6. The method according to claim 1, characterized in that, The constructed controllable magnetic field environment includes DC and AC magnetic fields, covering different frequency ranges, to simulate complex external magnetic field interference environments.

7. The method according to claim 1, characterized in that, Key external locations include the seams, openings, and corners of the magnetic shielding shell, while the areas near internal sensitive components include the mounting locations of fiber optic gyroscopes and accelerometers.

8. The method according to claim 1, characterized in that, When establishing the mathematical model, the fiber optic inertial navigation system under test is fixed on a high-precision three-axis turntable. By changing the orientation of the turntable, the Earth's gravity component is separated, and the magnetic sensitivity error of the accelerometer is extracted. By providing a known angular rate through the turntable, the magnetic sensitivity error and constant drift of the fiber optic gyroscope are separated.

9. The method according to claim 5, characterized in that, The output signal after real-time compensation is expressed as: , ,in, and These are the raw outputs from the fiber optic gyroscope and the accelerometer, respectively. and This represents the estimated error calculated based on real-time magnetic field measurements and the calibration model.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 9.

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