A reference-free single-axis turntable optical fiber strapdown inertial navigation field full-automatic calibration method

Abstract

The application provides a kind of reference-free single-axis rotary table optical fiber strapdown inertial navigation field full-automatic calibration method, which can be realized by only needing a single-axis rotary table, replaces the higher precision double-axis or three-axis rotary table and other equipment calibrated by traditional calibration method, reduces the demand for equipment of field calibration, replaces the requirement of accurate north induction and leveling of traditional calibration method, has better adaptability to harsh environment, meets the demand of complex and changeable field, first calibrates horizontal constant bias, then calibrates sky direction gyro scale coefficient and sky direction to horizontal axis gyro installation error, finally calibrates three-axis gyro constant bias, compensates coupling error of each parameter according to the set calibration order, iteratively reduces, generates automatic calibration program by combining the calibration method designed by the application with rotary table control program, realizes full automation of field calibration process, greatly shortens the calibration time compared with traditional calibration method, has the characteristics of simple method, high efficiency and full automation.

Description

Technical Field

[0001] This invention relates to the field of inertial navigation, and more particularly to a fully automatic field calibration method for a fiber optic strapdown inertial navigation system with a referenceless single-axis turntable. Background Technology

[0002] Due to the characteristics of inertial sensors, the navigation accuracy of fiber optic strapdown inertial navigation systems changes slowly with usage or storage time.

[0003] To improve the practicality of fiber optic strapdown inertial navigation systems, a key issue is how to quickly and accurately identify and calibrate the error parameters of these systems in the field to meet usage requirements and extend the time between calibrations at the factory.

[0004] Traditional calibration methods often require the use of calibrated dual-axis or tri-axis turntables to calibrate inertial navigation error parameters. Portable single-axis turntables are convenient to carry and have high relative rotation angle accuracy, but the external environment is complex and variable, making it difficult to quickly and accurately guide northward leveling.

[0005] Therefore, it is necessary to provide a fully automatic field calibration method for fiber optic strapdown inertial navigation systems on a single-axis turntable without a reference to solve the above-mentioned technical problems. Summary of the Invention

[0006] This invention provides a fully automatic field calibration method for fiber optic strapdown inertial navigation systems on a single-axis turntable without a reference, which solves the problem that traditional calibration methods are difficult to quickly and accurately perform north-pointing and leveling due to the complex and variable field environment.

[0007] To solve the above-mentioned technical problems, this invention provides a fully automatic field calibration method for a referenceless single-axis turntable fiber optic strapdown inertial navigation system, comprising the following steps:

[0008] S1: Place the product on the turntable, power it on and preheat for half an hour to allow the inertial sensor to stabilize. Then begin calibration data acquisition. The specific operation process is as follows: Acquire static IMU data for 5 minutes at the initial position, and record the initial position as position 0; Rotate the single-axis turntable clockwise 180°, record it as position 1, acquire IMU data during the rotation, and acquire static IMU data at position 1 for 5 minutes; Rotate the single-axis turntable clockwise 180° back to the initial position, record it as position 2, acquire IMU data during the rotation, and acquire static IMU data at position 2 for 5 minutes; Rotate the single-axis turntable clockwise 90°, record it as position 3, and acquire static IMU data for 5 minutes; Rotate the single-axis turntable clockwise 180°, record it as position 4, acquire IMU data during the rotation, and acquire static IMU data at position 4 for 5 minutes; Rotate the single-axis turntable clockwise 180° back to position 3, record it as position 4, acquire IMU data during the rotation, and acquire static IMU data at position 4 for 5 minutes;

[0009] S2: Establish the velocity and attitude error equations for the static base of the fiber optic strapdown inertial navigation system based on the North-West-Sky navigation coordinate system;

[0010] S3: Based on the above steps, establish the state equation using horizontal velocity error, misalignment angle error, horizontal accelerometer constant bias, and gyroscope constant bias as state variables, and establish the measurement equation using horizontal velocity error as the measurement variable. The above state equation and measurement equation constitute the Kalman filter state space model:

[0011] Equations of state:

[0012] Observation equation: Z = HX + V

[0013] S4: Based on the obtained Kalman filter model, the horizontal accelerometer constant bias of the four rotation data is calculated using the enhanced interrupt alignment method, and the average value is used as the final horizontal accelerometer constant bias and compensation is performed.

[0014] S5: The turntable rotates around the Z-axis. Before and after the rotation, the azimuth angle changes from ψ0 to ψ1. During the rotation, the horizontal attitude angle is relatively small. Let the misalignment angle change from φ0 to φ1. Then, the change in misalignment angle is Δφ = φ1 - φ0, which is only related to... The relevant attitude error is:

[0015]

[0016] Based on the above formula, the calibration coefficients of the azimuth gyroscope and the installation error of the azimuth gyroscope relative to the horizontal axis gyroscope are completed. The results are calculated four times at positions 0-1, 1-2, 3-4, and 4-5. The average of the four results is the final δK. gxz δK gyz δK gzz And compensation;

[0017] S6: The turntable has no reference and has a horizontal error. Calculate the constant bias of the three-axis gyroscope using the following formula:

[0018]

[0019]

[0020] The constant bias of the three-axis gyroscope is calibrated using the above formula. The results are calculated four times at positions 0-1, 1-2, 3-4, and 4-5. The average of the four results is the final gyroscope drift δε. b And compensation.

[0021] Preferably, in step S2, the velocity error equation is:

[0022]

[0023] Expanding, we get:

[0024]

[0025] Attitude error equation:

[0026]

[0027] Expanding, we get:

[0028]

[0029] Where, δv n Indicates speed error, This represents the measurement error added in the navigation coordinate system n, where φ represents the misalignment angle error. This represents the measurement error of the gyroscope in the navigation coordinate system n. This is the Earth's rotation speed.

[0030] Preferably, in step S3, the state vector X is as follows:

[0031]

[0032] Based on the velocity error equation and attitude error equation of the fiber optic strapdown inertial navigation static base system in S1, the continuous one-step transfer matrix F can be obtained:

[0033]

[0034]

[0035] In a static state, the velocity output of the fiber optic strapdown inertial navigation system is the velocity error, and the measurement matrix is:

[0036] H = [I 2×2 0 2×8 ]

[0037] W is the system noise vector, and V is the observation noise vector.

[0038] Preferably, the accelerometer constant bias compensation method in step S4 is as follows:

[0039]

[0040] Where: f b This indicates the output of the accelerometer; This represents the bias of the horizontal accelerometer constant estimated by filtering.

[0041] Preferably, in step S5, integrating both sides yields:

[0042]

[0043] It can achieve:

[0044]

[0045] Wherein, φ0=

[000] ;

[0046] Based on the above formula, complete the calibration of the scale coefficient of the astronomical gyroscope and the installation error of the astronomical gyroscope relative to the horizontal axis gyroscope.

[0047] Preferably, the specific calculation process of S5 is as follows:

[0048] S51: att0 is obtained by aligning static 5-minute data at position 0, and att1 is obtained by navigating to position 1 and ending after 5 minutes;

[0049] S52: att2 is obtained by aligning static 5-minute data from position 1;

[0050] S53: Calculate the misalignment angle error φ1 between att1 and att2;

[0051] S54: The scale coefficient of the astrogyroscope and the installation error δK of the astrogyroscope relative to the horizontal axis are calculated according to formula 3-2. gxz δK gyz δK gzz ;

[0052] S55: For positions 1-2, 3-4, and 4-5, calculate the remaining three results according to S51 to S54. The average of the four results is the final δK. gxz δK gyz δK gzz And compensation;

[0053] The following are the methods for compensating for the scale coefficients of the gyroscope and the installation error of the gyroscope relative to the horizontal axis:

[0054] ω b =ω b *[eye(3)-δK GZ ]'

[0055] Where: ω b This indicates the output of a three-axis gyroscope.

[0056] Preferably, the specific calculation process in step S6 is as follows:

[0057] S61: Att0 and AT0 are obtained by aligning static 5-minute data from position 0. Navigate to location 1 for 5 minutes to get att1 and

[0058] S62: Calculate the average angular rate output of the gyroscope after 5 minutes of static data at position 0. The average angular rate output of the gyroscope after 5 minutes of static data at position 1 is obtained.

[0059] S63: δε is calculated using the above formula. b ;

[0060] S64: For positions 1-2, 3-4, and 4-5, the remaining three results can be obtained by following S61-S63. The average of the four results is the final gyroscope drift δε. b And compensation;

[0061] The method for compensating for constant bias in a three-axis gyroscope is as follows:

[0062] ω b =ω b -δε b

[0063] Where: ω b This indicates the output of a three-axis gyroscope.

[0064] Preferably, in step S1 of the fully automatic calibration method for fiber optic strapdown inertial navigation in the field without reference single-axis turntable, the product needs to be placed on the turntable, which includes: the turntable body;

[0065] A turntable is rotatably mounted in the middle of the top of the turntable. A movable groove is opened in the middle of the top of the turntable. A fixed block is fixedly installed in the middle of the movable groove. Limiting rods are fixedly installed on both sides of the outer surface of the fixed block. An elastic element is sleeved on one side of the outer surface of the limiting rod, and a limiting device is slidably installed on the other side of the outer surface of the limiting rod.

[0066] A limiting device is fixedly installed on the top of the turntable body, and the limiting device includes a mounting ring block, an angle indicator plate, a threaded hole, and a threaded rod;

[0067] The four indicator blocks are equidistantly fixed around the top of the turntable body, and the outer surface of the turntable body is provided with multiple limiting holes.

[0068] Preferably, the limiting device includes a limiting slider, a clamping plate, a pressing inclined plate, and a connecting plate. The limiting slider is slidably mounted on the outer surface of the limiting rod, the clamping plate is fixedly connected to the top of the limiting slider, the pressing inclined plate is fixedly connected to the top of the clamping plate, and the connecting plate is fixedly connected to one side of the outer surface of the clamping plate.

[0069] Preferably, the mounting ring block is fixedly mounted on the top of the turntable body, a plurality of angle indicator plates are fixedly mounted at equal intervals on the top of the mounting ring block, a plurality of threaded holes are equally spaced on the outer surface of the mounting ring block, and the threaded rod is threaded into the interior of the threaded hole.

[0070] Compared with related technologies, the fully automatic field calibration method for a referenceless single-axis turntable fiber optic strapdown inertial navigation system provided by this invention has the following advantages:

[0071] This invention provides a fully automated field calibration method for fiber optic strapdown inertial navigation systems (INS) without a reference single-axis turntable. This method requires only a single-axis turntable, replacing traditional calibration methods that necessitate calibrated, higher-precision dual-axis or tri-axis turntables, significantly reducing equipment requirements for field calibration. It also replaces the traditional method's requirement for precise turntable north alignment and leveling, offering better adaptability to harsh environments and meeting the complex and variable needs of field calibration. The method first calibrates the constant bias of the horizontal accelerator, then calibrates the scale coefficient of the astronomical gyroscope and the installation error of the astronomical gyroscope relative to the horizontal axis, and finally calibrates the constant bias of the tri-axis gyroscope. The coupling error of each parameter is reduced through iterative compensation according to the set calibration sequence. By combining the calibration method designed in this invention with the turntable control program to generate an automatic calibration program, the entire field calibration process can be automated, significantly shortening the calibration time compared to traditional methods. This method is characterized by its simplicity, high efficiency, and full automation. Attached Figure Description

[0072] Figure 1 A flowchart illustrating a fully automated field calibration method for a referenceless single-axis turntable fiber optic strapdown inertial navigation system provided by the present invention.

[0073] Figure 2 This is an external view of the single-axis rotary table upon which the present invention is based;

[0074] Figure 3 This is an external view of the fiber optic strapdown inertial navigation product upon which this invention is based;

[0075] Figure 4 The navigation calculation speed error diagram before calibration is used to verify the present invention.

[0076] Figure 5 This invention provides an experimental verification diagram of the navigation calculation speed error after calibration.

[0077] Figure 6 This is a schematic diagram of the second embodiment of the fully automatic field calibration method for a referenceless single-axis turntable fiber optic strapdown inertial navigation system provided by the present invention;

[0078] Figure 7 for Figure 6 The enlarged schematic diagram at point A is shown below;

[0079] Figure 8 for Figure 6 The enlarged schematic diagram at point B is shown below;

[0080] Figure 9 for Figure 6 The diagram shows the structure of the limiting device.

[0081] The following are the labeling elements in the diagram: 10. Turntable body; 20. Turntable; 30. Limiting device; 301. Limiting slider; 302. Clamping plate; 303. Extrusion inclined plate; 304. Connecting plate; 40. Moving groove; 50. Fixing block; 60. Limiting rod; 70. Elastic element; 80. Limiting device; 801. Mounting ring block; 802. Angle indicator plate; 803. Threaded hole; 804. Threaded rod; 90. Indicator block; 100. Limiting hole. Detailed Implementation

[0082] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0083] Please refer to the following: Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 ,in, Figure 1 A flowchart illustrating a fully automated field calibration method for a referenceless single-axis turntable fiber optic strapdown inertial navigation system provided by the present invention. Figure 2 This is an external view of the single-axis rotary table upon which the present invention is based; Figure 3 This is an external view of the fiber optic strapdown inertial navigation product upon which this invention is based;

[0084] Figure 4 The navigation calculation speed error diagram before calibration is used to verify the present invention. Figure 5 This invention provides an experimental verification of the navigation calculation speed error diagram after calibration. A fully automated field calibration method for a referenceless single-axis turntable fiber optic strapdown inertial navigation system includes the following steps:

[0085] S1: Place the product on the turntable, power it on and preheat for half an hour to allow the inertial sensor to stabilize. Then begin calibration data acquisition. The specific operation process is as follows: Acquire static IMU data for 5 minutes at the initial position, and record the initial position as position 0; Rotate the single-axis turntable clockwise 180°, record it as position 1, acquire IMU data during the rotation, and acquire static IMU data at position 1 for 5 minutes; Rotate the single-axis turntable clockwise 180° back to the initial position, record it as position 2, acquire IMU data during the rotation, and acquire static IMU data at position 2 for 5 minutes; Rotate the single-axis turntable clockwise 90°, record it as position 3, and acquire static IMU data for 5 minutes; Rotate the single-axis turntable clockwise 180°, record it as position 4, acquire IMU data during the rotation, and acquire static IMU data at position 4 for 5 minutes; Rotate the single-axis turntable clockwise 180° back to position 3, record it as position 4, acquire IMU data during the rotation, and acquire static IMU data at position 4 for 5 minutes;

[0086] S2: Establish the velocity and attitude error equations for the static base of the fiber optic strapdown inertial navigation system based on the North-West-Sky navigation coordinate system;

[0087] S3: Based on the above steps, establish the state equation using horizontal velocity error, misalignment angle error, horizontal accelerometer constant bias, and gyroscope constant bias as state variables, and establish the measurement equation using horizontal velocity error as the measurement variable. The above state equation and measurement equation constitute the Kalman filter state space model:

[0088] Equations of state:

[0089] Observation equation: Z = HX + V

[0090] S4: Based on the obtained Kalman filter model, the horizontal accelerometer constant bias of the four rotation data is calculated using the enhanced interrupt alignment method, and the average value is used as the final horizontal accelerometer constant bias and compensation is performed.

[0091] S5: The turntable rotates around the Z-axis. Before and after the rotation, the azimuth angle changes from ψ0 to ψ1. During the rotation, the horizontal attitude angle is relatively small. Let the misalignment angle change from φ0 to φ1. Then, the change in misalignment angle is Δφ = φ1 - φ0, which is only related to... The relevant attitude error is:

[0092]

[0093] Based on the above formula, the calibration coefficients of the azimuth gyroscope and the installation error of the azimuth gyroscope relative to the horizontal axis gyroscope are completed. The results are calculated four times at positions 0-1, 1-2, 3-4, and 4-5. The average of the four results is the final δK. gxz δK gyz δK gzz And compensation;

[0094] S6: The turntable has no reference and has a horizontal error. Calculate the constant bias of the three-axis gyroscope using the following formula:

[0095]

[0096] The constant bias of the three-axis gyroscope is calibrated using the above formula. The results are calculated four times at positions 0-1, 1-2, 3-4, and 4-5. The average of the four results is the final gyroscope drift δε. b And compensation.

[0097] In step S2, the velocity error equation is:

[0098]

[0099] Expanding, we get:

[0100]

[0101] Attitude error equation:

[0102]

[0103] Expanding, we get:

[0104]

[0105] Where, δv n Indicates speed error, This represents the measurement error added in the navigation coordinate system n, where φ represents the misalignment angle error. This represents the measurement error of the gyroscope in the navigation coordinate system n. This is the Earth's rotation speed.

[0106] In step S3, the state vector X is as follows:

[0107]

[0108] Based on the velocity error equation and attitude error equation of the fiber optic strapdown inertial navigation static base system in S1, the continuous one-step transfer matrix F can be obtained:

[0109]

[0110]

[0111] In a static state, the velocity output of the fiber optic strapdown inertial navigation system is the velocity error, and the measurement matrix is:

[0112] H = [I 2×2 0 2×8 ]

[0113] W is the system noise vector, and V is the observation noise vector.

[0114] Preferably, the accelerometer constant bias compensation method in step S4 is as follows:

[0115]

[0116] Where: f b This indicates the output of the accelerometer; This represents the bias of the horizontal accelerometer constant estimated by filtering.

[0117] In step S5, integrating both sides yields:

[0118]

[0119] It can achieve:

[0120]

[0121] Wherein, φ0=

[000] ;

[0122] Based on the above formula, complete the calibration of the scale coefficient of the astronomical gyroscope and the installation error of the astronomical gyroscope relative to the horizontal axis gyroscope.

[0123] The specific calculation process for S5 is as follows:

[0124] S51: att0 is obtained by aligning static 5-minute data at position 0, and att1 is obtained by navigating to position 1 and ending after 5 minutes;

[0125] S52: att2 is obtained by aligning static 5-minute data from position 1;

[0126] S53: Calculate the misalignment angle error φ1 between att1 and att2;

[0127] S54: The scale coefficient of the astrogyroscope and the installation error δK of the astrogyroscope relative to the horizontal axis are calculated according to formula 3-2. gxz δK gyz δK gzz ;

[0128] S55: For positions 1-2, 3-4, and 4-5, calculate the remaining three results according to S51 to S54. The average of the four results is the final δK. gxz δK gyz δK gzz And compensation;

[0129] The following are the methods for compensating for the scale coefficients of the gyroscope and the installation error of the gyroscope relative to the horizontal axis:

[0130] ω b =ω b *[eye(3)-δK GZ ]'

[0131] Where: ω b This indicates the output of a three-axis gyroscope.

[0132] The specific calculation process in step S6 is as follows:

[0133] S61: Att0 and AT0 are obtained by aligning static 5-minute data from position 0. Navigate to location 1 for 5 minutes to get att1 and

[0134] S62: Calculate the average angular rate output of the gyroscope after 5 minutes of static data at position 0. The average angular rate output of the gyroscope after 5 minutes of static data at position 1 is obtained.

[0135] S63: δε is calculated using the above formula. b ;

[0136] S64: For positions 1-2, 3-4, and 4-5, the remaining three results can be obtained by following S61-S63. The average of the four results is the final gyroscope drift δε. b And compensation;

[0137] The method for compensating for constant bias in a three-axis gyroscope is as follows:

[0138] ω b =ω b -δε b

[0139] Where: ω b This indicates the output of a three-axis gyroscope.

[0140] By using a fiber optic strapdown inertial navigation system ( Figure 3 The correctness and feasibility of the above field calibration method were verified, with the fiber optic gyroscope accuracy being 0.02° / h and the accelerator accuracy being 5×10⁻⁶. -5 g. The sampling frequency is 100Hz. The product is mounted on a single-axis CNC rotary table, and the field calibration is completed using the executable program implemented according to the above calibration method. After calibration, the product is powered off and restarted, and static rotation data is collected: the product is stationary for 30 minutes, then the heading is rotated 180°, and then stationary for another 30 minutes. This is used to excite the system error, and the calibration results are verified by comparing the speed error before and after the calibration parameters are compensated.

[0141] Depend on Figure 4-5 As shown in Table 1, the RMS values ​​of the east and north directions before calibration were 0.77 m / s and 1.45 m / s, respectively. After calibration, the RMS values ​​of the east and north directions calculated by navigation were 0.098 m / s and 0.108 m / s, respectively. The navigation speed error was significantly reduced, and the navigation accuracy was improved.

[0142] Table 1 Field calibration results

[0143]

[0144] The working principle of the fully automatic field calibration method for a referenceless single-axis turntable fiber optic strapdown inertial navigation system provided by this invention is as follows:

[0145] During operation, the product is first installed on a single-axis turntable to continuously collect static data at six positions and data from five rotations. After data collection, the constant bias of the accelerator is calculated using the velocity error as a measurement and the enhanced interrupted alignment method. Secondly, the scale coefficient of the astronomical gyroscope and the installation error of the astronomical gyroscope relative to the horizontal axis are calculated based on the misalignment angle error before and after each rotation. Finally, the constant bias of the gyroscope is calculated based on the multi-position data, and dynamic verification is performed using laboratory data. The results show that the constant bias of the horizontal accelerator, the constant bias of the three-axis gyroscope, the scale coefficient of the astronomical gyroscope, and the installation error of the astronomical gyroscope relative to the horizontal axis can be accurately calibrated, thereby improving the accuracy of fiber optic strapdown inertial navigation.

[0146] Compared with related technologies, the fully automatic field calibration method for a referenceless single-axis turntable fiber optic strapdown inertial navigation system provided by this invention has the following advantages:

[0147] This invention provides a fully automated field calibration method for fiber optic strapdown inertial navigation systems (INS) without a reference single-axis turntable. This method requires only a single-axis turntable, replacing traditional calibration methods that necessitate calibrated, higher-precision dual-axis or tri-axis turntables, significantly reducing equipment requirements for field calibration. It also replaces the traditional method's requirement for precise turntable north alignment and leveling, offering better adaptability to harsh environments and meeting the complex and variable needs of field calibration. The method first calibrates the constant bias of the horizontal accelerator, then calibrates the scale coefficient of the astronomical gyroscope and the installation error of the astronomical gyroscope relative to the horizontal axis, and finally calibrates the constant bias of the tri-axis gyroscope. The coupling error of each parameter is reduced through iterative compensation according to the set calibration sequence. By combining the calibration method designed in this invention with the turntable control program to generate an automatic calibration program, the entire field calibration process can be automated, significantly shortening the calibration time compared to traditional methods. This method is characterized by its simplicity, high efficiency, and full automation.

[0148] Second Embodiment

[0149] Please refer to the following: Figure 6 , Figure 7 , Figure 8 and Figure 9 Based on the first embodiment of this application, which provides a reference-free single-axis turntable fiber optic strapdown inertial navigation system (FIS) field fully automatic calibration method, the second embodiment of this application proposes another reference-free single-axis turntable FIS field fully automatic calibration method. The second embodiment is merely a preferred embodiment of the first embodiment, and its implementation will not affect the separate implementation of the first embodiment.

[0150] Specifically, the difference between the second embodiment of this application and the fully automatic calibration method for fiber optic strapdown inertial navigation in the field without reference is that, in step S1 of the fully automatic calibration method for fiber optic strapdown inertial navigation in the field without reference, the product needs to be placed on the turntable, and the turntable includes: a turntable body 10.

[0151] Turntable 20 is rotatably mounted in the middle of the top of turntable 1. A movable groove 40 is provided in the middle of the top of turntable 20. A fixed block 50 is fixedly installed in the middle of the movable groove 40. Limiting rods 60 are fixedly installed on both sides of the outer surface of the fixed block 50. An elastic element 70 is sleeved on one side of the outer surface of the limiting rod 60. A limiting device 30 is slidably installed on the other side of the outer surface of the limiting rod 60.

[0152] A limiting device 80 is fixedly installed on the top of the turntable body 10. The limiting device 80 includes a mounting ring block 801, an angle indicator plate 802, a threaded hole 803, and a threaded rod 804.

[0153] Indicator blocks 90, four of the indicator blocks 90 are fixedly installed at equal intervals around the top of the turntable body 10, and the outer surface of the turntable body 10 is provided with multiple limiting holes 100.

[0154] The limiting device 30 includes a limiting slider 301, a clamping plate 302, a pressing inclined plate 303, and a connecting plate 304. The limiting slider 301 is slidably mounted on the outer surface of the limiting rod 60. The clamping plate 302 is fixedly connected to the top of the limiting slider 301. The pressing inclined plate 303 is fixedly connected to the top of the clamping plate 302. The connecting plate 304 is fixedly connected to one side of the outer surface of the clamping plate 302.

[0155] The mounting ring block 801 is fixedly mounted on the top of the turntable body 10, and a plurality of angle indicator plates 802 are fixedly mounted at equal intervals on the top of the mounting ring block 801. A plurality of threaded holes 803 are equally spaced on the outer surface of the mounting ring block 801, and the threaded rod 804 is threadedly engaged with the inside of the threaded hole 803.

[0156] The elastic element 70 adopts a spring structure. One end of the elastic element 70 is fixedly connected to one side of the inner wall of the moving groove 40, and the other end of the elastic element 70 is fixedly connected to one side of the outer surface of the limiting slider 301.

[0157] The limiting hole 100 has thirty-six holes, and four indicator blocks 90 are respectively set around the top of the turntable 20 to indicate 90 degrees, 180 degrees, 270 degrees and 360 degrees.

[0158] The angle indicator plate 802 has thirty-six parts, which matches the number of 100 limit holes. The indicator plates for 90 degrees, 180 degrees, 270 degrees and 0 degrees are longer, which makes them stand out.

[0159] The turntable 20 is manually rotated, increasing the precision of angle adjustment.

[0160] The working principle of the fully automatic field calibration method for a referenceless single-axis turntable fiber optic strapdown inertial navigation system provided by this invention is as follows:

[0161] During operation, the product is first placed on top of the two extrusion inclined plates 303 and pushed downward. The extrusion inclined plates 303 are driven by the extrusion force of the product to move the clamping plate 302 and the limiting slider 301. The limiting slider 301 slides inside the moving groove 40 and extrudes the elastic member 70.

[0162] When the product is placed at the top center of the turntable 20, the restoring elastic force of the elastic element 70 pushes the limiting slider 301 to slide, and the limiting slider 301 drives the clamping plate 302 to move, so that the two clamping plates 302 fit against the two sides of the product surface to restrict the product.

[0163] The four indicator blocks 90 serve as angle references. When the turntable 20 needs to be adjusted to the four marked positions, the operator can observe whether the rotation angle is accurate by referring to the indicator blocks 90 and the angle indicator plate 802. When the turntable 20 is rotated, the indicator blocks 90 are rotated, and the indicator blocks 90 rotate on the surface of the angle indicator plate 802, making it easy for the operator to observe the rotation angle.

[0164] When the turntable 20 rotates 90 degrees or 180 degrees, the user rotates the threaded rod 804 to engage the threaded hole 803, which then inserts into the corresponding limiting hole 100 on the outer surface of the turntable 20, thereby restricting the turntable 200.

[0165] Compared with related technologies, the fully automatic field calibration method for a referenceless single-axis turntable fiber optic strapdown inertial navigation system provided by this invention has the following advantages:

[0166] This invention provides a fully automatic field calibration method for fiber optic strapdown inertial navigation systems (INS) on a single-axis turntable without a reference. When installing the INS, it is simply placed between the top of two sets of limiting devices 30 and rests on the surface of the turntable 20. The restoring elastic force of the elastic element 70 pushes the clamping plate 302 to restrain the INS, preventing positional deviation due to external factors during testing. The arrangement of the indicator block 90, limiting device 80, and limiting hole 100 ensures accurate positioning of the INS on the turntable surface. The INS provides a reference point when mounted on the turntable, and provides angular reference when adjusting to 90 and 180 degrees, improving the accuracy of rotation angles, maintaining the accuracy of test records, and enhancing the accuracy of calibration position and experimental data recording during testing.

[0167] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A fully automated field calibration method for a referenceless single-axis turntable fiber optic strapdown inertial navigation system, characterized in that, Includes the following steps: S1: Place the product on the turntable, power it on and preheat for half an hour to allow the inertial sensor to stabilize before starting calibration data acquisition. The specific operation process is as follows: Acquire static IMU data for 5 minutes at the initial position, and record the initial position as position 0; rotate the single-axis turntable clockwise by 180°, record the position as position 1, acquire IMU data during the rotation process, and acquire static IMU data for 5 minutes at position 1. Rotate the single-axis turntable clockwise 180° back to the initial position, record position 2, collect IMU data during the rotation process, and collect static IMU data at position 2 for 5 minutes; Rotate the single-axis turntable clockwise by 90°, record 3 positions, and collect static IMU data for 5 minutes; Rotate the single-axis turntable 180° clockwise, record 4 positions, collect IMU data during the rotation process, and collect static IMU data at the 4 positions for 5 minutes; Rotate the single-axis turntable clockwise 180° back to position 3, record position 5, collect IMU data during the rotation process, and collect static IMU data at position 4 for 5 minutes; S2: Establish the velocity and attitude error equations for the static base of the fiber optic strapdown inertial navigation system based on the North-West-Sky navigation coordinate system; S3: Based on the above steps, establish the state equation using horizontal velocity error, misalignment angle error, horizontal accelerometer constant bias, and gyroscope constant bias as state variables, and establish the measurement equation using horizontal velocity error as the measurement variable. The above state equation and measurement equation constitute the Kalman filter state space model: Equations of state: Observation equation: in, For state vectors, The state matrix, Let be the system noise vector. For measurement vectors, For the measurement matrix, For measuring the noise vector; S4: Based on the obtained Kalman filter model, the horizontal accelerometer constant bias of the four rotation data is calculated using the Kalman filter alignment method based on velocity error observation. The average of the four results is used as the final compensation value to compensate the original output of the inertial sensor in real time. S5: The turntable rotates around the Z-axis. The azimuth angle before and after rotation is from... Change to During the rotation, the horizontal attitude angle is relatively small, and the misalignment angle is recorded from... Change to The change in the misalignment angle is Only with The relevant attitude error is: in, To calculate the misalignment angle between the navigation system and the ideal navigation system, Output to the gyroscope. For position rotation; Based on the above formula, the calibration coefficients of the azimuth gyroscope and the installation error of the azimuth gyroscope relative to the horizontal axis gyroscope are completed. The results are calculated four times at positions 0-1, 1-2, 3-4, and 4-5. The average of the four results is the final value. , , And compensate for the previous pose matrix; This refers to the gyroscope's calibration coefficients and the cross-coupling error between the gyroscope and the horizontal axis. This refers to the Z-axis to X-axis cross-coupling error. This refers to the Z-axis to Y-axis cross-coupling error. This refers to the Z-axis scale coefficient error. S6: The turntable has no reference and has a horizontal error. Calculate the constant bias of the three-axis gyroscope using the following formula: in, This represents the average angular velocity of the static three-axis gyroscope after rotation. The mean angular velocity of the static three-axis gyroscope before rotation; in, This is the navigation attitude array after the transposition. Alignment with attitude array before transposition; in, for misalignment angle in, This is the Earth's rotational angular rate. The latitude is the local latitude. in, The estimated gyroscope constant is zero bias; The constant bias of the three-axis gyroscope is calibrated using the above formula. The results are calculated four times at positions 0-1, 1-2, 3-4, and 4-5. The average of the four results is the final gyroscope drift. And compensation.

2. The fully automatic field calibration method for a referenceless single-axis turntable fiber optic strapdown inertial navigation system according to claim 1, characterized in that, In step S2, the velocity error equation is: Expanding, we get: in, For the differential of velocity error, For speed error, Acceleration for the navigation system To calculate the misalignment angle between the navigation system and the ideal navigation system, For the measurement error of the accelerometer in the navigation system; Attitude error equation: Expanding, we get: in, To calculate the differential of the misalignment angle between the navigation frame and the ideal navigation frame, For the measurement error of the navigation system gyroscope; in, Indicates speed error, This represents the measurement error added in the navigation coordinate system n. Indicates the misalignment angle error. This represents the measurement error of the gyroscope in the navigation coordinate system n. This refers to the Earth's rotation speed; in, Let be the attitude matrix. For the measurement error of the accelerometer of the machine system This refers to the measurement error of the gyroscope in the machine system.

3. The fully automatic field calibration method for a referenceless single-axis turntable fiber optic strapdown inertial navigation system according to claim 1, characterized in that, In step S3, the state vector X is as follows: Based on the velocity error equation and attitude error equation of the fiber optic strapdown inertial navigation static base system in S2, the continuous one-step transfer matrix F is obtained: In a static state, the velocity output of the fiber optic strapdown inertial navigation system is the velocity error, and the measurement matrix is: Let be the system noise vector. This is the observed noise vector.

4. The fully automatic field calibration method for a referenceless single-axis turntable fiber optic strapdown inertial navigation system according to claim 1, characterized in that, The accelerometer constant bias compensation method in step S4 is as follows: in: This indicates the output of the accelerometer; This represents the bias of the horizontal accelerometer constant estimated by filtering; These are accelerometer sample values.

5. The fully automatic field calibration method for a referenceless single-axis turntable fiber optic strapdown inertial navigation system according to claim 1, characterized in that, In step S5, integrating both sides yields: It can achieve: in, ; Based on the above formula, complete the calibration of the scale coefficient of the astrogyroscope and the installation error of the astrogyroscope relative to the horizontal axis gyroscope.

6. The fully automatic field calibration method for a referenceless single-axis turntable fiber optic strapdown inertial navigation system according to claim 1, characterized in that, The specific calculation process for S5 is as follows: S51: att0 is obtained by aligning static 5-minute data at position 0, and att1 is obtained by navigating to position 1 for 5 minutes. S52: att2 is obtained by aligning static 5-minute data from position 1; S53: Calculate the misalignment angle error between att1 and att2 ; S54: Calculate the gyroscope scale coefficient and the gyroscope installation error relative to the horizontal axis using the integral formula in S5. , , ; S55: For positions 1-2, 3-4, and 4-5, calculate the remaining three results according to S51 to S54. The average of the four results is the final value. , , And compensation; The following are the methods for compensating for the scale coefficients of the gyroscope and the installation error of the gyroscope relative to the horizontal axis: in: This indicates the output of the three-axis gyroscope; att0 is the heading and attitude angle at position 0, att1 is the heading and attitude angle at position 1 when navigation ends, and att2 is the heading and attitude angle at position 1.

7. The fully automatic field calibration method for a referenceless single-axis turntable fiber optic strapdown inertial navigation system according to claim 1, characterized in that, The specific calculation process in step S6 is as follows: S61: Att0 and att0 are obtained by aligning static 5-minute data from position 0. Navigate to location 1 for 5 minutes to get att1 and ; S62: Calculate the average angular rate output of the gyroscope after 5 minutes of static data at position 0. The average angular rate output of the gyroscope at position 1 after 5 minutes of static data is obtained. ; S63: Calculated according to the gyroscope drift calculation formula in S6. ; S64: For positions 1-2, 3-4, and 4-5, the remaining three results can be obtained by following S61-S63. The average of the four results is the final gyroscope drift. And compensation; The method for compensating for constant bias in a three-axis gyroscope is as follows: in: This indicates the output of the three-axis gyroscope; att0 is the heading attitude angle aligned to position 0. For the corresponding attitude matrix, att1 is the heading attitude angle at the end of navigation at position 1; This is the corresponding attitude matrix.

8. The fully automatic field calibration method for a referenceless single-axis turntable fiber optic strapdown inertial navigation system according to claim 1, characterized in that, In step S1 of the aforementioned fully automatic calibration method for fiber optic strapdown inertial navigation system in the field without reference, the product needs to be placed on the turntable, which includes: the turntable body; A turntable is rotatably mounted in the middle of the top of the turntable. A movable groove is opened in the middle of the top of the turntable. A fixed block is fixedly installed in the middle of the movable groove. Limiting rods are fixedly installed on both sides of the outer surface of the fixed block. An elastic element is sleeved on one side of the outer surface of the limiting rod, and a limiting device is slidably installed on the other side of the outer surface of the limiting rod. A limiting device is fixedly installed on the top of the turntable body, and the limiting device includes a mounting ring block, an angle indicator plate, a threaded hole, and a threaded rod; The four indicator blocks are equidistantly fixed around the top of the turntable body, and the outer surface of the turntable body is provided with multiple limiting holes.

9. The fully automatic field calibration method for a referenceless single-axis turntable fiber optic strapdown inertial navigation system according to claim 8, characterized in that, The limiting device includes a limiting slider, a clamping plate, a pressing inclined plate, and a connecting plate. The limiting slider is slidably mounted on the outer surface of the limiting rod. The clamping plate is fixedly connected to the top of the limiting slider. The pressing inclined plate is fixedly connected to the top of the clamping plate. The connecting plate is fixedly connected to one side of the outer surface of the clamping plate.

10. The fully automatic field calibration method for a referenceless single-axis turntable fiber optic strapdown inertial navigation system according to claim 8, characterized in that, The mounting ring block is fixedly installed on the top of the turntable body, and multiple angle indicator plates are fixedly installed at equal intervals on the top of the mounting ring block. Multiple threaded holes are equally spaced on the outer surface of the mounting ring block, and the threaded rod is threaded into the interior of the threaded hole.

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