CN117309004A - Orthogonality static calibration method for triaxial fiber optic gyroscope - Google Patents

Abstract

The invention discloses a triaxial fiber optic gyroscope orthogonality static calibration method, which comprises the following steps: the installation step comprises the following steps: the three optical fiber gyroscopes are respectively arranged on the triaxial base and fixed on the table top of the turntable, the sensitive axis of the optical fiber gyroscopes is parallel to the rotation axis of the turntable, and the optical fiber gyroscopes are driven to rotate by the rotation of the turntable; and a data acquisition step: in the rotating process of the fiber optic gyroscope system, angle speed values without zero offset of three sensitive axes of the fiber optic gyroscope are collected statically at a plurality of positions; the optical fiber gyro calibration step: and according to the acquired angular velocity value without zero offset, carrying out orthogonality calibration calculation of the triaxial fiber-optic gyroscope according to the principle that the square sum of the triaxial angular velocity is equal to the rotation angular velocity of the earth.

Description

Orthogonality static calibration method of three-axis fiber optic gyroscope

Technical field

The invention belongs to the field of fiber optic gyroscope calibration, and in particular relates to a three-axis fiber optic gyroscope orthogonal static calibration method.

Background technique

Fiber optic gyroscope is a sensing instrument based on the Sagnac effect. Its measurement principle is to determine the rotation angle and angular velocity by measuring the optical path difference of two beams of light. It has been widely used in inertial navigation systems and maritime north-finding systems. . The calibration and installation error compensation of fiber optic gyroscope is a process of establishing a mathematical model for the coordinate system and calculating the parameters of the mathematical model. During the installation process of the fiber optic gyro system, three single-axis fiber optic gyroscopes need to be installed on the corresponding base, which will cause a non-negligible installation error between the actual fiber optic gyro sensor coordinate system and the ideal carrier coordinate system. The non-orthogonal phenomenon of the three axes as shown in Figure 1 will greatly affect the output accuracy of the fiber optic gyroscope, so the system must be corrected for orthogonality.

As shown in Figure 2, in the traditional orthogonal compensation of fiber optic gyro sensors, a dynamic calibration method is often used, that is, the angular deviation of the fiber optic gyro is corrected by obtaining the actual rotation speed of the electric turntable. This method is simple and easy to operate, but The requirements for the turntable are very high. The basic requirement is that the accuracy of the turntable is one order of magnitude greater than the accuracy of the fiber optic gyroscope itself. When the turntable cannot be orthogonal to the base, it is impossible to obtain correct output on all axes. There is another general method, as shown in Figure 3, which is to use the real attitude angle to correct the three-axis fiber optic gyroscope. This method needs to obtain the heading angle, roll angle and pitch angle at the current position, and then substitute it into the error equation to obtain the optimal solution, but there are situations where it is difficult to obtain an accurate attitude angle. The above two methods have good calibration effects when using high-precision precision instruments, but they may increase errors when the experimental conditions cannot meet the requirements.

To sum up, the current method of correcting non-orthogonal errors using rotational speed and correcting non-orthogonal errors using attitude angle has certain limitations.

Contents of the invention

The purpose of the embodiments of this application is to provide an orthogonal static calibration method for a three-axis fiber optic gyroscope in view of the shortcomings of the prior art. The technical solution is as follows:

A static calibration method for orthogonality of a three-axis fiber optic gyroscope, including:

(1) Installation steps: Install the three fiber optic gyroscopes on the three-axis base and fix them to the table of the turntable. Make the sensitive axis of the fiber optic gyroscope parallel to the rotation axis of the turntable. The rotation of the turntable drives the fiber optic gyroscope to rotate. ;

(2) Data collection step: During the rotation of the fiber optic gyroscope system, statically collect the angular rate values without zero bias of the three sensitive axes of the fiber optic gyroscope at several positions;

(3) Fiber optic gyroscope calibration step: Based on the collected angular rate values without zero bias, and based on the principle that the sum of the squares of the three-axis angular rates is equal to the earth's rotation angular velocity, the orthogonality calibration calculation of the three-axis fiber optic gyroscope is performed.

Further, the fiber optic gyroscope installed in step (1) is the fiber optic gyroscope after the zero bias is removed. The method of removing the zero bias is:

Place three fiber optic gyroscopes horizontally on the horizontal plane. According to the right-hand screw rule, the direction of their sensitive axes is vertically upward;

Let the fiber optic gyroscope stand for 5-10 hours and collect the original output data of the fiber optic gyroscope's static long-term angular velocity value;

After analyzing the collected fiber optic gyroscope data, after removing the low-frequency noise, the celestial component of the fiber optic gyroscope according to the earth's angular velocity was obtained, and the constant bias of the three fiber optic gyroscopes was calibrated and removed based on the local latitude information of the experiment.

Further, the calculation expression of the input angular rate without zero offset is

G _X =ω _X cos(Ψ _X )+ω _Y sin(θ _XY )+ω _Z sin(θ _XZ )

G _Y =ω _X sin(θ _YX )+ω _Y cos(Ψ _Y )+ω _Z sin(θ _YZ )

G _Z =ω _X sin(θ _ZX )+ω _Y sin(θ _ZY )+ω _Z cos(Ψ _Z )

_{Among them , G _ _ The rate values , Ψ _ _ _ _} Cross-axis effects of quasi-error angle.

Further, in step (2), the static collection specifically includes: waiting for a predetermined period of time after rotation before collecting.

Furthermore, during the rotation process of the fiber optic gyroscope system, each rotation simultaneously changes the direction of the sensitive axis of the three-axis fiber optic gyroscope.

Further, step (3) is specifically:

According to the principle that the sum of the squares of the three-axis angular rates is equal to the angular velocity of the earth's rotation, several sets of equations are listed. Through data fitting, the optimal solution of the angular error that makes the sum of the squares of the three-axis angular rates of the fiber optic gyroscope closest to the angular velocity of the earth's rotation is found. Calculate the calibrated output angular rate of the sensitive axis of the fiber optic gyroscope, and perform the calibration calculation of the fiber optic gyroscope based on the optimal solution and the calibrated output angular rate.

Furthermore, the principle is that the sum of the squares of the three-axis angular rates is equal to the angular velocity of the earth's rotation, and its specific expression is:

ω _X ² +ω _Y ² +ω _Z ² =ω _ie ²

ω _ie represents the earth's rotation angular velocity, and ω _X , ω _Y , and ω _Z represent the true angular velocity value, that is, the calibrated output angular rate value.

Furthermore, the least squares method is used to find the optimal solution for the angular error that makes the square sum of the fiber optic gyroscope's three-axis angular rate closest to the earth's rotation angular velocity:

f(x)＝ω _ie ² -(ω _X ² +ω _Y ² +ω _Z ² )

ω _ie represents the earth's rotation angular velocity, and ω _X , ω _Y , and ω _Z represent the true angular velocity value, that is, the calibrated output angular rate value.

Further, the calibration calculation of the fiber optic gyroscope is performed based on the optimal solution and the calibration output angular rate, specifically as follows:

The angular velocity output value of the three-axis fiber optic gyroscope in the orthogonal coordinate system can be obtained.

The technical solutions provided by the embodiments of this application may include the following beneficial effects:

It can be seen from the above embodiments that the present application can better calibrate the non-orthogonal error of the three-axis fiber optic gyroscope during the testing process of the fiber optic gyroscope. The invention does not need to be equipped with a high-precision electric turntable, has low requirements on the experimental environment, simplifies repeated operations during the test process, and ensures that the expected test allowable test system error can be achieved.

It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and do not limit the present application.

Description of the drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the application and together with the description, serve to explain the principles of the application.

Figure 1 is a schematic diagram of non-orthogonal errors of a three-axis fiber optic gyroscope according to an exemplary embodiment.

Figure 2 is a schematic diagram of the non-orthogonal error velocity calibration method.

Figure 3 is a schematic diagram of the non-orthogonal error angle calibration method.

FIG. 4 is a flow chart illustrating a method for removing the bias of a fiber optic gyroscope according to an exemplary embodiment.

Figure 5 is a schematic diagram of a three-axis fiber optic gyroscope orthogonal static calibration method according to an exemplary embodiment.

Figure 6 is a schematic diagram of an electric turntable according to an exemplary embodiment.

FIG. 7 is a schematic diagram of the three-axis sum of squares effect after orthogonality correction of a three-axis fiber optic gyroscope according to an exemplary embodiment.

Figure 8 is a schematic diagram showing the north-seeking effect of a three-axis fiber optic gyroscope after orthogonality correction according to an exemplary embodiment.

Detailed ways

Exemplary embodiments will be described in detail herein, examples of which are illustrated in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings refer to the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with this application.

The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this application and the appended claims, the singular forms "a," "the" and "the" are intended to include the plural forms as well, unless the context clearly dictates otherwise. It will also be understood that the term "and/or" as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

It should be understood that although the terms first, second, third, etc. may be used in this application to describe various information, the information should not be limited to these terms. These terms are only used to distinguish information of the same type from each other. For example, without departing from the scope of the present application, the first information may also be called second information, and similarly, the second information may also be called first information. Depending on the context, the word "if" as used herein may be interpreted as "when" or "when" or "in response to determining."

Three-axis fiber optic gyroscope refers to an independent fiber optic gyroscope with three sensitive axes. They have their own zero offset values and scaling factors. Before performing orthogonality correction, the zero offset value and scaling factor of the fiber optic gyroscope need to be corrected. Calibration, if solved with zero bias error and calibration factor error, will expand the instability of orthogonality correction. As shown in Figure 4 is a method for removing zero offset, which includes the following steps:

Placement step S1: Place the three fiber optic gyroscopes horizontally on the horizontal plane. According to the right-hand screw rule, the sensitive axis direction is vertically upward.

Collection step S2: Let the fiber optic gyroscope stand for 5-10 hours, and collect the original output data of the fiber optic gyroscope's static long-term angular velocity value.

Analysis and calculation step S3: Analyze the collected fiber optic gyroscope data. After removing the low-frequency noise, obtain the sky component of the fiber optic gyroscope according to the earth's angular velocity as ω _ie sinφ, where φ represents the latitude of the current position, combined with the local latitude information of the laboratory. Calibration removal. After calibration, the constant biases of the three light gyros are approximately 7.1259×10 ^-5 °/s, -3.6910×10 ^-5 °/s, and -6.5618×10 ^-5 °/s respectively.

Since the fiber optic gyroscope is a high-precision precision sensor, the manufacturer has calibrated the scale factor of the fiber optic gyroscope before leaving the factory, and the nonlinearity and asymmetry of the scale factor are on the order of a few parts per million. It has basically no impact on the calibration results.

Figure 1 shows a general model of non-orthogonal errors in fiber optic gyroscope installation. OXYZ is the global coordinate system of the fiber optic gyroscope. The XYZ three axes in this coordinate system are perpendicular to each other to form an orthogonal coordinate system. The intersection of the three axes is the origin of the coordinate system. , the coordinate system is usually set according to the carrier. _{OG X} G _{Y G Z is} the coordinate axis where the fiber optic gyroscope is actually installed. The three axes G There are non-orthogonal angle errors. This embodiment provides a static calibration method for three-axis fiber optic gyroscope orthogonality, with the purpose of correcting the angular error between the above coordinate axes. The method is shown in Figure 5 and includes the following steps:

(1) Installation steps: Install the three fiber optic gyroscopes on the three-axis base and fix them to the table of the turntable. Make the sensitive axis of the fiber optic gyroscope parallel to the rotation axis of the turntable. The rotation of the turntable drives the fiber optic gyroscope to rotate. ;

Specifically, the turntable used in this system is shown in Figure 6. The stage body adopts a U-U-T structure, which can simulate the three-dimensional movement of the carrier. The use of this kind of turntable can well fix the fiber optic gyroscope device and reduce the problems caused by loose fixation. Shake. In this embodiment, the three-axis fiber optic gyroscope needs to be fixed to the three rotation axes of the base.

(2) Data collection step: During the rotation of the fiber optic gyro system, statically collect the angular rate values of the three sensitive axes of the fiber optic gyro at at least 9 positions at a frequency of 1000 Hz. When the turntable rotates, the three sensitive axes of the fiber optic gyro need to be changed. the direction of the axis;

In one embodiment, it is necessary to rotate the fiber optic gyroscope to 68 different positions through an electric turntable, and record 68 groups of input angular rates without bias on the sensitive axes of the three fiber optic gyroscopes. Collecting multiple sets of data can reduce abnormality. The impact caused by interference is taken as an example to collect 68 sets of data during calibration in this implementation plan. Normally, there are only 9 unknowns in the equation system, so at least 9 sets of data are required. The purpose of using a frequency of 1000 Hz for acquisition is to meet the factory-set acquisition frequency of the fiber optic gyroscope in this embodiment, so as to avoid linear errors in numerical values. When the turntable rotates, it is necessary to change the directions of the sensitive axes of the three fiber optic gyroscopes at the same time in order to change the three input quantities of the equation system, otherwise it will lead to repeated inputs to the equation system. And after each rotation, you should wait 5s before collecting. Because the fiber optic gyroscope will have short-term numerical fluctuations after rotation, you need to wait for the fiber optic gyroscope to stabilize before collecting, and the acquisition time should be greater than 20s, in order to ensure the stability of the average data. .

(3) Fiber optic gyroscope calibration step: Based on the collected static three-axis angular rate values, and based on the principle that the sum of the squares of the three-axis angular rates is equal to the earth's rotation angular velocity, perform the orthogonality calibration calculation of the three-axis fiber optic gyroscope;

In this embodiment, based on the principle that the sum of the squares of the three-axis angular rates is equal to the earth's rotation angular velocity, 68 sets of equations are listed. Through data fitting, the equation that makes the sum of the squares of the three-axis angular rates of the fiber optic gyroscope closest to the earth's rotation angular velocity is found. The optimal solution of the angle error is to calculate the calibrated output angular rate of the sensitive axis of the fiber optic gyroscope, and perform the calibration calculation of the fiber optic gyroscope based on the optimal solution and the calibrated output angular rate.

The calculation expression of the input angular rate without zero offset is

G _X =ω _X cos(Ψ _X )+ω _Y sin(θ _XY )+ω _Z sin(θ _XZ )

G _Y =ω _X sin(θ _YX )+ω _Y cos(Ψ _Y )+ω _Z sin(θ _YZ )

G _Z =ω _X sin(θ _ZX )+ω _Y sin(θ _ZY )+ω _Z cos(Ψ _Z )

Among them, _Gx , G _Y and G _Z represent the angular rates measured by the three fiber optic gyroscope _sensitive axes. This angular rate has removed the influence of _zero bias and calibration coefficient. ω _{Values , Ψ _ _ _ _ _ _} Cross-axis effects of error angle.

For the principle that the sum of the squares of the three-axis angular rates is equal to the earth's rotation angular velocity, the specific expression is:

ω _X ² +ω _Y ² +ω _Z ² =ω _ie ²

In the formula, ω _ie represents the earth's rotation angular velocity, that is, ω _ie =15.041°/h.

The data fitting method is the least squares method, which is a mathematical optimization technique. It finds the best functional match of the data by minimizing the sum of squared errors. The least squares method can be used to easily obtain unknown data, and minimize the sum of squares of errors between the obtained data and the actual data. The basic idea is

In the formula, _Li (x) is called the residual function, y _i is called the target value, f (x _i , ω _i ) is the current function, and f (x) is called the objective function.

According to the principle of least squares method, applied to fiber optic gyroscope calibration, its expression is:

f(x)＝ω _ie ² -(ω _X ² +ω _Y ² +ω _Z ² )

In this way, the minimum solution to the calibrated linear equations is obtained.

According to the calibration error equations, the angular rate value in the orthogonal case is back-solved, and its calculation expression is:

Through this expression, the angular velocity output value of the three-axis fiber optic gyroscope in the orthogonal coordinate system can be obtained.

As shown in Figure 7, the static sum of squares average value at each position of the corrected three-axis fiber optic gyroscope angular velocity value is reduced from 4.1836e-05 under the original data to 4.1803e-05, and the variance is reduced from 4.904e-05 to 2.462e-05, when the average change is small, the variance is reduced to 49.8% of the original value. It can be seen that this calibration method can effectively reduce the error caused by non-orthogonality.

As shown in Figure 8, the calibrated three-axis fiber optic gyroscope has significantly improved its north-seeking application. The average north-seeking value of the true value is 57.5384°, and the average north-seeking value of the original data is 58.1646°. After correction, The final average value of north seeking is 57.3968°, and the error is reduced from 0.6° to 0.1°. The error is reduced by 83.3%, which improves the north seeking accuracy and is closer to the true value.

Other embodiments of the present application will be readily apparent to those skilled in the art from consideration of the specification and practice of the disclosure herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary technical means in the technical field that are not disclosed in this application. .

It is to be understood that the present application is not limited to the precise structures described above and illustrated in the accompanying drawings, and that various modifications and changes may be made without departing from the scope thereof.

Claims (9)

1. The method for calibrating orthogonality static state of the triaxial fiber optic gyroscope is characterized by comprising the following steps:

(1) The installation step comprises the following steps: the three optical fiber gyroscopes are respectively arranged on the triaxial base and fixed on the table top of the turntable, the sensitive axis of the optical fiber gyroscopes is parallel to the rotation axis of the turntable, and the optical fiber gyroscopes are driven to rotate by the rotation of the turntable;

(2) And a data acquisition step: in the rotating process of the fiber optic gyroscope system, angle speed values without zero offset of three sensitive axes of the fiber optic gyroscope are collected statically at a plurality of positions;

(3) The optical fiber gyro calibration step: and according to the acquired angular velocity value without zero offset, carrying out orthogonality calibration calculation of the triaxial fiber-optic gyroscope according to the principle that the square sum of the triaxial angular velocity is equal to the rotation angular velocity of the earth.

2. The method of claim 1, wherein the fiber-optic gyroscope installed in step (1) is a fiber-optic gyroscope with zero bias removed, and the method for removing zero bias is as follows:

placing the three fiber optic gyroscopes horizontally on a horizontal plane, and vertically upwards in the direction of a sensitive axis according to a right-hand spiral rule;

standing the fiber-optic gyroscope for 5-10 hours, and collecting original output data of a static long-time angular velocity value of the fiber-optic gyroscope;

analyzing the collected data of the fiber-optic gyroscope, removing low-frequency noise, obtaining the opposite-to-sky component of the fiber-optic gyroscope according to the earth angular velocity, and carrying out calibration removal of the constant zero offset of the three fiber-optic gyroscopes by combining the local latitude information of the experiment.

3. The method of claim 2, wherein the calculated expression of the zero offset free input angular rate is

G _X ＝ω _X cos(Ψ _X )+ω _Y sin(θ _XY )+ω _Z sin(θ _XZ )

G _Y ＝ω _X sin(θ _YX )+ω _Y cos(Ψ _Y )+ω _Z sin(θ _YZ )

G _z ＝ω _X sin(θ _ZX )+ω _Y sin(θ _ZY )+ω _Z cos(Ψ _Z )

Wherein G is _X 、G _Y 、G _Z Representing the angular rate measured by the sensitive axes of three fiber optic gyroscopes, which has been freed from the effects of zero offset and calibration coefficients, ω _X 、ω _Y 、ω _Z Indicating true angular velocity values, i.e. nominal output angular velocity values, ψ _X 、Ψ _Y 、Ψ _Z Representing the alignment error angle theta of the three axial directions of the fiber optic gyroscope and the global coordinate system _XY 、θ _YX 、θ _YZ 、θ _ZY 、θ _ZX 、θ _ZY Representing the trans-axial effect of the alignment error angle.

4. The method according to claim 1, wherein in step (2), the static acquisition is specifically: and waiting for a preset time period after rotation and collecting.

5. The method of claim 1, wherein during rotation of the fiber-optic gyroscope system, each rotation simultaneously changes the direction of the sensitive axis of the tri-axis fiber-optic gyroscope.

6. The method according to claim 1, wherein step (3) is specifically:

according to the principle that the square sum of the three-axis angular velocity is equal to the earth rotation angular velocity, a plurality of sets of equations are listed, an optimal solution of an angle error which enables the square sum of the three-axis angular velocity of the optical fiber gyroscope to be closest to the earth rotation angular velocity is obtained through a data fitting mode, the calibration output angular velocity of the sensitive axis of the optical fiber gyroscope is calculated, and the calibration calculation of the optical fiber gyroscope is carried out according to the optimal solution and the calibration output angular velocity.

7. The method according to claim 6, wherein the principle that the sum of squares of the three-axis angular velocity is equal to the rotational angular velocity of the earth is expressed as follows:

ω _X ² +ω _Y ² +ω _Z ² ＝ω _ie ²

ω _ie indicating the rotational angular velocity, ω, of the earth _X 、ω _Y 、ω _Z The true angular velocity value is represented as a nominal output angular velocity value.

8. The method of claim 6, wherein the optimal solution of the angle error that causes the sum of squares of the three-axis angular rates of the fiber-optic gyroscope to be closest to the rotational angular velocity of the earth is obtained by a least square method:

f(x)＝ω _ie ² -(ω _X ² +ω _Y ² +ω _Z ² )

ω _ie indicating the rotational angular velocity, ω, of the earth _X 、ω _Y 、ω _Z The true angular velocity value is represented as a nominal output angular velocity value.

9. The method according to claim 6, wherein the calculating of the calibration of the fiber-optic gyroscope is performed according to the optimal solution and the calibration output angular rate, specifically:

the output value of the triaxial fiber optic gyroscope angular velocity under the orthogonal coordinate system can be obtained.