An alignment error calibration method and azimuth angle measurement method of an inertial platform

Abstract

The application relates to the field of inertial measurement, and specifically discloses an alignment error calibration method of an inertial platform and an azimuth angle measurement method. The alignment error calibration method comprises the following steps: acquiring a plurality of self-alignment azimuth angles of the platform, the plurality of self-alignment azimuth angles corresponding to a plurality of real azimuth angles in one-to-one manner; fitting an alignment error function according to the difference between the plurality of real azimuth angles and the plurality of self-alignment azimuth angles, the alignment error function being used for indicating the alignment error corresponding to any azimuth angle, and the alignment error and the self-alignment azimuth angle being used for indicating the measurement result of the real azimuth angle. The azimuth angle measurement method comprises the following steps: acquiring a current self-alignment azimuth angle; and determining a current real azimuth angle according to the current self-alignment azimuth angle and the alignment error function. The scheme of the application realizes the self-alignment error calibration of different base positions, and performs error compensation when the equipment is running, so that accurate self-alignment is realized, and the alignment precision level is improved.

Description

Technical Field

[0001] This application relates to the technical field of inertial measurement, and in particular to a method for calibrating alignment errors and measuring azimuth angles of an inertial platform. Background Technology

[0002] As a key component of the equipment, the alignment accuracy of the inertial platform directly affects the navigation accuracy of the equipment. Extensive engineering data analysis has revealed a correlation between the self-alignment error of the inertial platform and the base orientation, exhibiting good repeatability; this phenomenon is known as the heading effect. How to calibrate the self-alignment error for different base orientations and how to achieve accurate self-alignment during equipment operation are the technical problems this application aims to solve. Summary of the Invention

[0003] This application provides an alignment error calibration method and an azimuth angle measurement method for an inertial platform. The purpose is to calibrate the self-alignment error of different base azimuths and compensate for the self-alignment result of the current azimuth, so as to achieve accurate self-alignment during equipment operation and improve the alignment accuracy level.

[0004] Firstly, a method for calibrating the alignment error of an inertial platform is provided, including:

[0005] Multiple self-aligned azimuth angles are obtained from the platform, and each of the multiple self-aligned azimuth angles corresponds one-to-one with a multiple real azimuth angles.

[0006] Based on the differences between the plurality of true azimuth angles and the plurality of self-alignment azimuth angles, an alignment error function is fitted to indicate the alignment error corresponding to any self-alignment azimuth angle. The alignment error and the self-alignment azimuth angle are used to indicate the measurement results of the true azimuth angle.

[0007] Compared with the prior art, the solution provided in this application has at least the following beneficial technical effects:

[0008] By calibrating the self-alignment error of different base orientations, the alignment accuracy can be improved by compensating for the self-alignment result of the current orientation during equipment operation.

[0009] In conjunction with the first aspect, in some implementations of the first aspect, the alignment error function satisfies:

[0010]

[0011] Where Δα is the alignment error. K1, K2, K3, and K4 are the self-alignment azimuth angles, and K1, K2, K3, and K4 are the error coefficients.

[0012] The alignment error function described above is beneficial for improving the accuracy of alignment error calculation.

[0013] In conjunction with the first aspect, in certain implementations of the first aspect, the fitting to obtain the alignment error function includes:

[0014] The optimization of the cost function is performed, wherein the cost function satisfies:

[0015]

[0016] in, α i Let be the true azimuth angle of the i-th position. Let q be the self-alignment azimuth angle of the i-th direction. i These are the weighting coefficients.

[0017] The cost function takes into account the difference between the true azimuth and the self-aligned azimuth, as well as the corresponding alignment error, which is beneficial for fitting an accurate alignment error function.

[0018] In conjunction with the first aspect, in some implementations of the first aspect, the cost function is solved by particle swarm optimization, wherein the number of particles is 10 to 50, the number of iterations is 50 to 500, and the optimization interval is [-0.5, 0.5].

[0019] Choosing appropriate cost function parameters is beneficial for fitting an accurate alignment error function.

[0020] In conjunction with the first aspect, in some implementations of the first aspect, the weighting coefficient q i satisfy:

[0021]

[0022] in, Let be the self-alignment standard deviation of the i-th orientation platform. This is the sum of the standard deviations of self-alignment for all orientations.

[0023] The optimization weights corresponding to multiple true azimuth angles can be different. This allows for weakening of self-aligned azimuth angles with larger dispersion and strengthening of self-aligned azimuth angles with smaller dispersion. In other words, it enables targeted fitting for different azimuth angles.

[0024] In conjunction with the first aspect, in some implementations of the first aspect, the true azimuth angle is obtained by detecting a gyroscope, and the true azimuth angle satisfies:

[0025]

[0026] ω xi (i = 1, 2, 3) is X p axial angular velocity, α is X pThe angle between the axis at the zero position of the platform and the due north direction is θ, which is the rotation angle of the three-position alignment.

[0027] In conjunction with the first aspect, in some implementations of the first aspect, the self-alignment azimuth angle is obtained by detecting the current, and the self-alignment azimuth angle satisfies:

[0028]

[0029] Among them, I xi (i = 1, 2, 3) represents the average value of the leveling torque current at position i, and θ represents the rotation angle at the three positions.

[0030] In conjunction with the first aspect, in some implementations of the first aspect, the plurality of real azimuth angles are 8 to 32 azimuths with equal angular intervals.

[0031] Choosing the right number of azimuth angles is beneficial for fitting an accurate alignment error function.

[0032] Secondly, a method for measuring the azimuth angle of an inertial platform is provided, including:

[0033] Obtain the platform's current self-alignment azimuth angle;

[0034] Based on the current self-alignment azimuth angle And the alignment error function Δα obtained by the method described in any of the first aspects above, when compensated, has the following:

[0035] This indicates the azimuth angle after compensation.

[0036] Compensated azimuth It is closer to the current actual azimuth angle, improving the level of alignment accuracy.

[0037] In conjunction with the second aspect, in some implementations of the second aspect, the true azimuth angle is used to indicate the initial azimuth angle for navigation calculation.

[0038] This facilitates higher accuracy of orientation measurements at the start of navigation, thereby reducing navigation calculation errors and improving navigation accuracy.

[0039] Thirdly, an electronic device is provided for performing the method as described in any of the implementations of the first to second aspects above. Attached Figure Description

[0040] Figure 1 This is a schematic flowchart illustrating an alignment error calibration method for an inertial platform provided in an embodiment of this application.

[0041] Figure 2This relates to the relationship between the platform coordinate system and the geographic coordinate system.

[0042] Figure 3 This is a schematic flowchart illustrating an azimuth measurement method for an inertial platform provided in an embodiment of this application.

[0043] Figure 4 This is a schematic diagram of a three-position self-alignment error curve fitting and compensation process for an inertial platform, provided as an embodiment of this application.

[0044] Figure 5 The particle swarm cost function fitness value convergence curve provided in the embodiments of this application.

[0045] Figure 6 The alignment error function fitting curve provided in the embodiments of this application. Detailed Implementation

[0046] The present application will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0047] The self-alignment error of an inertial platform is correlated with the orientation of the base. To obtain the omnidirectional self-alignment error of the inertial platform and compensate for it during alignment, this application provides a method for calibrating the alignment error of an inertial platform.

[0048] Figure 1 This is a schematic flowchart of an alignment error calibration method for an inertial platform provided in an embodiment of this application.

[0049] 110, obtain multiple self-aligned azimuth angles from the platform, and each of the multiple self-aligned azimuth angles corresponds one-to-one with multiple real azimuth angles.

[0050] To compensate for the heading effect of platform system drift, a multi-azimuth method was used to test the true north alignment accuracy of the platform system in various azimuths. True north alignment testing was conducted within the range of 0°–360° north of west. A starting angle A and angular interval B were set as needed. Angles were selected within the interval A+B×k to A+B×(k+1) (k=0,1,2,3...,(360 / B-1)), meaning one azimuth was selected within each B-degree range for true north alignment accuracy testing. During actual testing, the platform was placed on a marble platform with an isolated foundation. The platform was manually rotated to adjust the base azimuth. The accuracy requirement for rotating the base to the desired azimuth was not high. In each azimuth, the inertial platform performed six self-alignments. At the zero-locking and leveling position of the platform, the true azimuth of the hexahedron installed on the platform was measured using a gyrotheodolite or theodolite.

[0051] During inertial platform self-alignment, the quartz watch senses the gravity component, and the gyroscope torque converter applies torque to keep the platform level and maintain the azimuth axis at the desired angle. The amount of torque applied by the gyroscope torque converter represents the projection of the ground velocity component on the corresponding axis. Three-position self-alignment involves rotating the platform to three azimuth positions and calculating the azimuth angle of the inertial platform using the torque current values ​​of the gyroscope torque converters in different azimuth positions.

[0052] The relationship between the platform coordinate system and the geographic coordinate system is as follows: Figure 2 As shown, the platform azimuth angle α is defined as the angle between the platform's X-axis and geographic north, with north-west being positive. p Y p Z p These are the X, Y, and Z axes of the platform, respectively.

[0053] The true azimuth angle is obtained by using a gyro theodolite or a theodolite:

[0054] The true azimuth angle satisfies:

[0055]

[0056] Where, ω xi (i = 1, 2, 3) represents the i-th position X. p Angular rate of axis, θ is the rotation angle of the three-position alignment.

[0057] The self-alignment azimuth angle is obtained by detecting the current, and the self-alignment azimuth angle satisfies:

[0058]

[0059] Among them, I xi (i = 1, 2, 3) represents the average value of the leveling torque current at position i, and θ represents the rotation angle at the three positions.

[0060] 120. Based on the differences between multiple true azimuth angles and multiple self-alignment azimuth angles, an alignment error function is fitted to obtain the alignment error function. The alignment error function is used to indicate the alignment error corresponding to any self-alignment azimuth angle. The alignment error and the self-alignment azimuth angle are used to indicate the measurement results of the true azimuth angle.

[0061] The alignment error function can satisfy the following form, for example:

[0062]

[0063] Where Δα is the alignment error. K1, K2, K3, and K4 are the azimuth angles, and K1, K2, K3, and K4 are the error coefficients.

[0064] In this embodiment of the application, an alignment error function can be fitted by establishing an optimization cost function. Specifically, based on the established alignment error function, and combined with the self-alignment data obtained from tests at multiple locations on the base and the actual azimuth data of the optical sight, the optimization cost function is established as follows:

[0065] in, α i Let be the true azimuth angle of the i-th position. Let q be the self-alignment azimuth angle of the i-th direction. i These are the weighting coefficients.

[0066] In some embodiments, the weighting coefficient q i It can take the value 1. That is to say, the optimization weights corresponding to multiple true azimuth angles can be the same.

[0067] In other embodiments, the weighting coefficient q i satisfy:

[0068]

[0069] in, Let be the self-alignment standard deviation of the i-th orientation platform. This is the sum of the standard deviations of all azimuth self-alignment angles. In other words, the optimization weights for multiple self-alignment azimuth angles can be different. This allows for the weakening of self-alignment azimuth angles with larger dispersion and the strengthening of self-alignment azimuth angles with smaller dispersion.

[0070] There are various methods to fit a function to a known model, such as least squares and optimization algorithms. In some embodiments, particle swarm optimization (PSO) is used to fit the alignment error coefficients. By finding the minimum value of the cost function using PSO, the alignment error coefficient values ​​can be obtained.

[0071] Figure 3 This is a schematic flowchart of an azimuth angle measurement method for an inertial platform provided in an embodiment of this application.

[0072] 210, obtain the platform's current self-alignment azimuth angle.

[0073] 220. Based on the current self-alignment azimuth and the alignment error function, determine the current true azimuth. The alignment error function is determined as follows: Figure 1 The method shown is used to obtain it.

[0074] In some embodiments, the minimum value of |current self-alignment azimuth + alignment error - true azimuth| can be found near the current self-alignment azimuth, and the found alignment error can be output.

[0075] In some possible scenarios, the estimated true azimuth angle is used to indicate the initial attitude direction of the navigation solution, which helps to reduce inertial navigation errors, especially in GPS-denied or restricted environments, to obtain higher accuracy navigation results and avoid excessive yaw. When used, the measured self-alignment azimuth angle and the error are superimposed to estimate the true azimuth angle.

[0076] This application also provides an electronic device for performing, for example, Figure 1 or Figure 3 The method shown.

[0077] This application will be further described in detail below.

[0078] Example 1

[0079] This invention relates to a method for calibrating alignment errors of an inertial platform and a method for measuring azimuth angles, the process of which is as follows: Figure 4 As shown, the specific steps are as follows:

[0080] (1) Multi-directional alignment test of the base

[0081] To compensate for alignment errors in the platform system, a multi-directional method is used to test the alignment accuracy of the platform system in various directions. This patent example tests the alignment accuracy of the platform system in 16 different orientations of the base. The alignment accuracy test is conducted within the range of 0° west of north to 360°. A starting angle is set as needed, taking 0° west of north as an example. Angles are selected within the interval of 0°+22.5°×k to 0°+22.5°×(k+1) (k=0, 1, 2, 3...15), meaning one base orientation is selected for alignment accuracy testing every 22.5°. In actual testing, the platform is placed on a marble platform with an isolated foundation. The platform is manually rotated to adjust the base orientation. The accuracy requirement for rotating the base to the desired orientation is not high. In each orientation, the inertial platform performs six self-aiming cycles. At the zero-locking and leveling position of the platform, the azimuth deviation between the hexahedron and true north is measured using a gyrotheodolite or theodolite.

[0082] (2) Establishing an optimization cost function based on the alignment error function

[0083] Based on the established alignment error function, and combining the self-alignment data obtained from tests at multiple locations on the base and the actual azimuth data of the optical sight, the optimization cost function is established as follows:

[0084] in, α i Let be the true azimuth angle of the i-th position. Let q be the self-alignment azimuth angle of the i-th direction. i As weighting coefficients, we have:

[0085]

[0086] in, Let be the self-alignment standard deviation of the i-th orientation platform. This is the sum of the standard deviations of self-alignment for all orientations.

[0087] (3) Particle swarm optimization solution

[0088] This patent employs a particle swarm optimization (PSO) algorithm to fit alignment error coefficients. A four-dimensional particle is established, with each dimension representing an alignment error coefficient value. The particle population size is set to 30, the iteration count to 500, and the optimization interval to [-0.5, 0.5]. After optimizing the cost function using the PSO algorithm, the alignment error coefficient values ​​can be obtained. The convergence curve of the cost function fitness value is shown below. Figure 5 As shown, the alignment error fitting curve is as follows: Figure 6 As shown. Figure 6 In the diagram, the red curve represents the fitted alignment error function curve, and the black asterisks represent the measured self-alignment error of the platform. Figure 5 It can be seen that the alignment error function fitting curve can fit the actual alignment error of the platform well, and can be used for alignment error compensation.

[0089] (4) Use alignment error function for all-round error compensation

[0090] After obtaining the self-alignment result at any base orientation, the alignment error function obtained by prior fitting is used to compensate for the alignment result.

[0091] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims of the present invention.

Claims

1. A method for calibrating the alignment error of an inertial platform, characterized in that, include: Multiple self-aligned azimuth angles are obtained from the platform, and each of the multiple self-aligned azimuth angles corresponds one-to-one with a multiple real azimuth angles. Based on the differences between the plurality of true azimuth angles and the plurality of self-alignment azimuth angles, an alignment error function is fitted to indicate the alignment error corresponding to any self-alignment azimuth angle. The alignment error and the self-alignment azimuth angle are used to indicate the measurement results of the true azimuth angle. The alignment error function satisfies: ， in, For alignment error, For self-alignment azimuth, , , , The error coefficient; The fitting yields an alignment error function, including: The optimization of the cost function is performed, wherein the cost function satisfies: ， in, , Let be the true azimuth angle of the i-th position. Let be the self-alignment azimuth angle of the i-th orientation. These are weighting coefficients; The cost function is solved by particle swarm optimization, where the number of particles is 10 to 50, the number of iterations is 50 to 500, and the optimization interval is [-0.5, 0.5]. Weighting coefficients satisfy: ， in, Let be the self-alignment standard deviation of the i-th orientation platform. This is the sum of the standard deviations of self-alignment for all orientations; The true azimuth angle of the hexahedron mounted on the platform is obtained by measuring with a gyro theodolite or a theodolite, and the true azimuth angle satisfies: ， (i=1,2,3) is The angular velocity of the axis at the self-aligned i-th position. for The angle between the axis at the zero position of the platform and the due north direction. The rotation angle is for three-position alignment.

2. The method according to claim 1, characterized in that, The self-alignment azimuth angle is obtained by detecting the current, and the self-alignment azimuth angle satisfies: ， in, (i=1,2,3) represents the average value of the leveling torque current at the i-th position. The rotation angle is for three-position alignment.

3. The method according to claim 1, characterized in that, The multiple true azimuth angles are 8 to 32 azimuths with equal angular intervals.

4. A method for measuring the azimuth angle of an inertial platform, characterized in that, include: Obtain the current self-alignment azimuth angle of the platform ; Based on the current self-alignment azimuth angle And the alignment error function obtained by the method of any one of claims 1 to 3. The compensation includes: , This indicates the azimuth angle after compensation.

5. The method according to claim 4, characterized in that, The true azimuth angle is used to indicate the initial azimuth for navigation calculation.

6. An electronic device, characterized in that, The electronic device is used to perform the method as described in any one of claims 1 to 5.

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