A fiber-optic strapdown inertial measurement unit free-decimation calibration method and device thereof

Abstract

The application discloses a kind of optical fiber strapdown inertial measurement unit disassembly-free calibration method and device, belong to optical fiber strapdown inertial measurement unit calibration field, by being directly installed in rotating mechanism by aircraft or functional module cabin section being installed with to-be-calibrated inertial measurement unit, and to-be-calibrated inertial measurement unit is powered on, so that inertial measurement unit outputs effective data collected by it, and actual rotation information is acquired, and the information is combined, the secondary calibration work to inertial measurement unit is completed, also proposes a kind of inertial measurement unit disassembly-free calibration device, the device includes first rotating mechanism and second rotating mechanism, can be carried out horizontal plane rotation and vertical plane rotation respectively, is provided with optical measurement component to acquire actual rotation information.The method and the effective amount of inertial measurement unit after calibration output are secondary calibrated, do not need to disassemble the carrier loaded with inertial measurement unit, also do not need to modify initial calibration parameter, meet the disassembly-free demand of installation to-be-calibrated inertial measurement unit carrier, improve inertial measurement unit calibration efficiency, with good application value.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of optical fiber strapdown inertial measurement unit calibration, and particularly relates to a kind of optical fiber strapdown inertial measurement unit disassembly-free calibration method and device thereof. BACKGROUND

[0002] In small aircraft, inertial devices play a role in real-time measurement of angular velocity, acceleration, attitude, speed and displacement, etc. The strapdown inertial measurement unit is a kind of inertial device, and generally consists of three mutually perpendicular gyroscopes and three accelerometers. When in use, the strapdown inertial measurement unit is directly installed on the carrier.

[0003] The calibration technology of the strapdown inertial measurement unit is one of the core technologies in the field of inertial navigation, which effectively eliminates the errors in the output signals of the gyroscopes and accelerometers in the inertial measurement unit. According to the calibration method, it can be divided into separate calibration, system calibration and online calibration. The separate calibration and system calibration are traditional calibration methods, which require the inertial measurement unit to be disassembled from the carrier and calibrated in the laboratory using special equipment such as turntable, marble platform and hexahedron. This calibration method has the advantages of high precision and good reliability, and plays a decisive role in error separation. However, since the strapdown inertial measurement unit is a precision measurement device, its error characteristics will change significantly over time, resulting in poor performance when used for navigation. To solve this problem, the product can be disassembled from the carrier and returned to the factory for re-calibration, or online calibration can be used to eliminate some errors to a certain extent.

[0004] Modern small aircraft are usually stored as a whole or split into functional cabin sections, and one of their characteristics is that they do not need to be disassembled for calibration, the application method should not be changed, and the precision performance should not be reduced. Therefore, the overall structure or modular functional cabin sections do not need to be disassembled during the entire service life. The current disassembly-free calibration method is usually online calibration. Online calibration can solve the problems of disassembly-free and insignificant reduction in precision performance, but unless the carrier itself has the online calibration function, it is difficult to achieve the unchanged application method. In many cases, online calibration requires various auxiliary mechanisms, means and peripheral devices, making it difficult for small aircraft carriers to respond quickly in emergency situations.

[0005] Therefore, there is an urgent need for a calibration method for the inertial measurement unit that can calibrate the strapdown inertial measurement unit in the aircraft while ensuring the integrity of the aircraft or modular equipment structure, to meet the application and storage requirements of the aircraft. SUMMARY

[0006] In order to solve one or more of the above defects or improvement needs of the prior art, the present application provides a fiber-optic strapdown inertial measurement unit calibration method and device, wherein the effective data output by the to-be-calibrated inertial measurement unit and the actual rotation information are compared and calculated to complete the secondary calibration data calculation.

[0007] To achieve the above object, the present application provides a fiber-optic strapdown inertial measurement unit calibration method and device, which comprises the following steps:

[0008] S1, installing a carrier loaded with a to-be-calibrated inertial measurement unit in a rotation frame, and arranging the body coordinates of the inertial measurement unit parallel to the body coordinates of the rotation frame , with the vertical downward direction as the first direction and the vertical upward direction as the second direction;

[0009] S2, powering on the inertial measurement unit, and after the to-be-calibrated inertial measurement unit is powered on and stabilized, the inertial measurement unit can output an effective amount, which includes gyro output values and accelerometer output values;

[0010] S3, performing accelerometer and axis gyro calibration of Z1 axis and Y1 axis, including the following steps:

[0011] A1, taking the to-be-calibrated axis as the reference axis, rotating the inertial measurement unit so that the reference axis points to the first direction, adjusting the inertial measurement unit to a stationary state, collecting the effective amount, and calculating the heading angle , the pitch angle , and the roll angle in the current state, and then calculating the first to-be-calibrated axis accelerometer residual error ;

[0012] A2, adjusting the inertial measurement unit to an inertial navigation state, rotating the carrier around the reference axis to a specified position, measuring the actual rotation difference between the current position and the initial position , and after the carrier starts to move to the stable state for a time T, obtaining the difference between the change amount of the inertial navigation heading angle output and the actual rotated heading angle change amount ;

[0013] A3, rotating the carrier so that the reference axis points to the second direction, adjusting the inertial measurement unit to a stationary state, collecting the effective amount, and calculating the second to-be-calibrated axis accelerometer residual error in the stationary state ;

[0014] A4, adjusting the inertial measurement unit to an inertial navigation state, rotating the carrier around the reference axis to a specified position, measuring the actual rotation difference , and after the inertial navigation stage for a time t, obtaining the difference between the change amount of the inertial navigation heading angle output and the actual rotated heading angle change amount ;

[0015] A5, calculating the bias residual of the to-be-calibrated axis accelerometer, the bias residual of the to-be-calibrated axis gyroscope and the scale factor correction value of the to-be-calibrated axis gyroscope;

[0016] S4, correcting the X1 axis accelerometer and the X1 axis gyroscope, including the following steps:

[0017] B1, taking any calibrated axis in the inertial measurement unit as a reference axis, and revising the output valid amount of the calibrated part;

[0018] B2, repeating the operations in A1-A5 in step 3 to calculate the bias residual of the X1 axis accelerometer, the bias residual of the X1 axis gyroscope and the scale factor correction value of the X1 axis gyroscope;

[0019] S5, verifying the calibration result and outputting the calibration result.

[0020] As a further improvement of the application, the valid amount of the output of the inertial measurement unit before calibration includes and ;

[0021] wherein, is the output value of the gyroscope at time i, is the output value of the accelerometer at time i.

[0022] As a further improvement of the application, the first accelerometer residual and the second accelerometer residual of the Z1 axis and the Y1 axis are obtained by formula (1) and formula (2) respectively,

[0023] (1)

[0024] (2)

[0025] wherein, represents the mean value calculation of the accelerometer output values collected in a period of time, and the formula is: .

[0026] As a further improvement of the application, the first accelerometer residual and the second accelerometer residual of the X1 axis are obtained by formula (3) and formula (4) respectively,

[0027] (3)

[0028] (4)

[0029] wherein, represents the mean value calculation of the X1 axis accelerometer output values collected in a period of time.

[0030] As a further improvement of the present application, the calculation formula of the bias residual error of the accelerometer is

[0031] (5)

[0032] The calculation formula of the zero bias residual error of the gyroscope is

[0033] (6)

[0034] The calculation formula of the scale factor correction value of the gyroscope is

[0035] (7).

[0036] As a further improvement of the present application, in step S1, the effective amount is revised, and the revised gyroscope output value is , and the revision formula is

[0037] (8)

[0038] The revised accelerometer output value is , and the revision formula is

[0039] (9).

[0040] As a further improvement of the present application, the rotation of the inertial measurement unit in the inertial navigation state is horizontal rotation, and the rotation is 360°.

[0041] As a further improvement of the present application, in step S6, the inertial measurement unit is rotated so that the body coordinate of the inertial measurement unit points to an arbitrary position, the body coordinate direction pointed by the body coordinate of the inertial measurement unit is measured, and is compared with the calibrated effective amount output by the inertial measurement unit, to confirm whether the calibration result is qualified, if yes, the calibration result is output, if not, the calibration is re-performed.

[0042] The application further provides a fiber-optic strapdown inertial measurement unit disassembly-free calibration device, which is characterized by comprising a rotating frame and an optical measurement assembly.

[0043] The rotating frame comprises a first rotating mechanism and a second rotating mechanism, the first rotating mechanism comprises a base provided with an annular sliding groove at the top and a stand column slidably matched with the annular sliding groove at one end, and the other end of the stand column is fixedly connected with the second rotating mechanism to drive the second rotating mechanism to horizontally rotate.

[0044] The second rotating mechanism comprises an outer ring and an inner ring, and the inner ring is slidably connected with the outer ring, so that the inner ring can rotate in a vertical plane relative to the outer ring. ​​​

[0045] The optical measuring assembly comprises an optical prism and an optical theodolite, the optical prism is fixedly arranged on the inner ring, so that the optical theodolite obtains the rotation information of the inner ring by measuring the position of the optical prism.

[0046] As a further improvement of the application, the inner ring and the outer ring are in a cylindrical structure,

[0047] And / or

[0048] The bottom of the base is provided with a height adjusting support to realize the leveling of the base.

[0049] The above technical features can be combined with each other as long as they do not conflict with each other.

[0050] Overall, compared with the prior art, the above technical scheme conceived by the application has the following beneficial effects:

[0051] (1) The optical fiber strapdown inertial measurement unit calibration method and device, by directly installing the aircraft or functional cabin segment to be calibrated in the rotating frame, and comparing and correcting the effective amount output by the to-be-calibrated inertial measurement unit and the related parameters measured by the optical theodolite, the calibration of the to-be-calibrated inertial measurement unit is realized, without the need to modify the factory calibration parameters of the to-be-calibrated inertial measurement unit, and the effective amount output by the inertial measurement unit is calibrated twice in actual application, so that accurate position information, angle information and acceleration information are output by the inertial measurement unit;

[0052] (2) The optical fiber strapdown inertial measurement unit calibration method and device, by parallelizing the body coordinates of the inertial measurement unit body and the body coordinates of the rotating frame at the initial setting, selecting the North-East-Down ONED coordinate system as the reference navigation coordinate system, and preferably selecting the vertical downward and vertical upward directions as the first direction and the second direction, and collecting for 3 minutes, the calculation process in the calibration process is simple and fast, and the calibration efficiency is improved without affecting the calibration effect;

[0053] (3) The optical fiber strapdown inertial measurement unit calibration method and device, by providing a calibration device to realize the calibration method, which comprises a rotating frame, an optical prism and an optical theodolite, the rotating frame comprises a first rotating mechanism and a second rotating mechanism, which respectively rotate in the horizontal plane and the vertical plane, wherein the inner ring in the second rotating mechanism is directly fixedly connected with the carrier of the to-be-calibrated inertial measurement unit, and the optical prism is arranged on the inner ring, so that the optical theodolite measures the actual rotation difference between the current position and the initial position and the actual change of the heading angle, and the values are used in the calibration calculation;

[0054] (4) The optical fiber strapdown inertial measurement unit free disassembly calibration method and device, the first rotating mechanism includes a base, adjustable legs are arranged at the bottom of the base and can be adjusted in height to perform horizontal leveling, an annular sliding groove is arranged at the top of the base, and a column structure is arranged in sliding connection in correspondence, the column has at least one group, each group of columns includes two columns arranged symmetrically about the center of the annular sliding groove, so as to realize stable support of the second rotating mechanism, at the same time, the second rotating mechanism includes an inner ring and an outer ring, the outer ring is fixedly connected with the column, and the inner ring is in sliding connection with the outer ring, so as to realize vertical plane rotation of the carrier, and the outer ring and the inner ring can adopt a cylindrical structure, so that the rotating frame rotates the carrier with large weight, and the deformation is within a limited range, so as to match the optical prism and the optical theodolite, and the calibration work is completed. BRIEF DESCRIPTION OF DRAWINGS

[0055] Fig. 1 is the front view of the optical fiber strapdown inertial measurement unit free disassembly calibration device in the embodiment of the application;

[0056] Fig. 2 is the top view of the optical fiber strapdown inertial measurement unit free disassembly calibration device in the embodiment of the application;

[0057] In all the drawings, the same reference signs represent the same technical features, specifically: 1, base; 101, annular sliding groove; 2, column; 3, outer ring; 4, inner ring; 5, adjustable leg. DETAILED DESCRIPTION

[0058] In order to make the purpose, technical scheme and advantages of the present application clearer and more apparent, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not to limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0059] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore it cannot be understood as a limitation on the present application.

[0060] In addition, the terms "first", "second", etc. are used only for descriptive purposes and are not to be construed as indicating or implying relative importance or an ordered sequence among or between the indicated features. Thus, features defined with "first", "second" can include, explicitly or implicitly, at least one of such features. In the description of the present application, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise explicitly specified and limited.

[0061] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting", "fixing" and the like should be understood broadly, for example, can be fixedly connected, or can be detachably connected, or can be integrated; can be mechanically connected, or can be electrically connected; can be directly connected, or can be indirectly connected through an intermediate medium; can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0062] In the present application, unless otherwise explicitly specified and limited, the first feature is "on" or "under" the second feature, which can be direct contact between the first and second features, or indirect contact between the first and second features through an intermediate medium. Moreover, the first feature "above", "over" and "on" the second feature can be directly above or obliquely above the first feature, or only indicate that the horizontal height of the first feature is higher than that of the second feature. The first feature "below", "under" and "under" the second feature can be directly below or obliquely below the first feature, or only indicate that the horizontal height of the first feature is less than that of the second feature.

[0063] Embodiments:

[0064] Please refer to Figs. 1-2 The optical fiber strapdown inertial measurement unit calibration method and device of the preferred embodiment of the present application, wherein the application proposes a calibration device comprising a rotating frame, an optical prism and an optical theodolite, the rotating frame comprising a first rotating mechanism and a second rotating mechanism, the rotation of the horizontal plane and the vertical plane is realized through the two rotating mechanisms, thereby driving the aircraft or module cabin section (i.e. the carrier with the inertial measurement unit) to be calibrated to rotate to complete the calibration work.

[0065] Further, the first rotating mechanism comprises a base 1 and a column 2 in sliding connection with the base 1, the upper surface of the base 1 is provided with a ring-shaped sliding groove 101, and one end of the column 2 is embedded in the ring-shaped sliding groove 101, so that the column 2 can move circumferentially along the ring-shaped sliding groove 101. At least one column group is arranged in the first rotating mechanism, which comprises two columns 2 symmetrically arranged about the center of the ring (i.e. the ring-shaped sliding groove). The end of the column 2 away from the base 1 is fixedly connected with the second rotating mechanism, so that when the column 2 moves circumferentially, the second rotating mechanism is driven by the column 2 to rotate horizontally. The second rotating mechanism comprises an outer ring 3 and an inner ring 4, the outer ring 3 is fixedly connected with the column 2, and the inner ring 4 is used to load the carrier. The outer ring 3 and the inner ring 4 can rotate relative to each other, thereby driving the carrier to rotate in the vertical plane.

[0066] Further, in actual application, the aircraft or module cabin section to be calibrated has a large overall structure, a heavy weight, and a certain length. Correspondingly, the outer ring 3 and the inner ring 4 in the second rotating mechanism are both in a cylindrical structure to realize the loading of the large-weight carrier. Further preferably, the first rotating mechanism comprises two column groups, one group of columns 2 is arranged on both sides of the cylindrical structure of the outer ring 3, and the other group of columns 2 is fixedly connected with the bottom or end of the cylindrical structure of the outer ring 3, which can be selected according to the length of the cylindrical structure of the outer ring 3.

[0067] Further, since the inner ring 4 is directly connected with the carrier to be calibrated, in order to measure the actual rotation angle of the carrier, an optical prism is correspondingly installed on the inner ring 4, and an optical theodolite is correspondingly arranged to measure the rotation angle of the inner ring 4, thereby obtaining the actual rotation angle of the carrier. Further preferably, adjustable feet 5 are arranged at the bottom of the base 1, the bottom of the adjustable feet 5 is provided with rolling wheels to drive the rotary table to move in position, and is fixed to the ground after reaching the specified position. The adjustable feet 5 are arranged at four corners of the base 1, and the height of each adjustable foot 5 is adjustable. The height of each adjustable foot 5 can be adjusted to adjust the base 1 to be horizontal (horizontal inclination ≤1°), so as to ensure the calibration accuracy.

[0068] In a preferred embodiment, the fiber-optic strapdown inertial unit to be calibrated comprises a fiber-optic gyroscope and a quartz accelerometer, wherein the accuracy of the fiber-optic gyroscope is between 0.1° / h and 0.001° / h, and the accuracy of the quartz accelerometer is ≤200μg. The related calibration parameters of the fiber-optic strapdown inertial unit are complete when it is delivered from the factory, and the installation error after calibration is within 20". In order to realize effective measurement, the rotation deformation of the rotary table under the load condition is not more than 3°. Further, the diameter of the carrier to be calibrated is not more than 1.5m, the length is not more than 5m, and the mass is not more than 5 tons.

[0069] Based on the calibration device, the application further provides a fiber-optic strapdown inertial unit calibration method without disassembly, which comprises the following steps:

[0070] S1, install a carrier with a to-be-calibrated inertial measurement unit in a rotation frame, and align the body coordinate of the inertial measurement unit with the body coordinate of the rotation frame parallel to each other, with a vertically downward direction as a first direction and a vertically upward direction as a second direction;

[0071] S2, power on the inertial measurement unit, and after the power on is stable, enable the inertial measurement unit to output an effective amount, the effective amount including a gyro output value and an accelerometer output value;

[0072] S3, perform calibration of the accelerometer and the axis gyroscope of the Z1 axis and the Y1 axis, including the following steps:

[0073] A1, take the to-be-calibrated axis as a reference axis, rotate the inertial measurement unit so that the reference axis points to the first direction, adjust the inertial measurement unit to a stationary state, collect the effective amount, and calculate a heading angle in the current state , a pitch angle , and a roll angle , and then calculate a first to-be-calibrated axis accelerometer residual error ;

[0074] A2, adjust the inertial measurement unit to an inertial navigation state, rotate the carrier around the reference axis to a specified position, measure an actual rotation difference between the current position and the initial position , the time experienced in the inertial navigation stage is T, and the difference between the change amount of the inertial navigation heading angle output and the actual rotation change amount of the heading angle is obtained ;

[0075] A3, rotate the carrier so that the reference axis points to the second direction, adjust the inertial measurement unit to a stationary state, collect the effective amount, and calculate a second to-be-calibrated axis accelerometer residual error in the stationary state ;

[0076] A4, adjust the inertial measurement unit to an inertial navigation state, rotate the carrier around the reference axis to a specified position, measure an actual rotation difference , the time experienced in the inertial navigation stage is t, and the difference between the change amount of the inertial navigation heading angle output and the actual rotation change amount of the heading angle is ;

[0077] A5, calculate a to-be-calibrated axis accelerometer bias residual error, a to-be-calibrated axis gyroscope zero offset residual error, and a to-be-calibrated axis gyroscope scale factor correction value;

[0078] S4, perform correction of the X1 axis accelerometer and the X1 axis gyroscope, including the following steps:

[0079] ​B1. Take any calibrated axis in the inertial navigation system as the reference axis, and revise the calibrated portion of the output effective quantity.

[0080] B2. Repeat steps A1 to A5 in step 3 to calculate the bias residual of the X1-axis accelerometer, the zero bias residual of the X1-axis gyroscope, and the scale factor correction value of the X1-axis gyroscope.

[0081] S5. Verify the calibration results and output the calibration results.

[0082] Furthermore, step S1 includes the following specific steps:

[0083] S11. Fix the rotating frame to the ground and adjust the height of the adjustable support 5 to level the base 1 so that the base 1 is in a horizontal state.

[0084] S12. Install the carrier with the inertial navigation system to be calibrated onto the inner ring 4, and make the volume coordinate axis of the inertial navigation system consistent with the volume coordinate axis of the rotation frame.

[0085] S13. Rotate its column 2 and / or inner ring 4 to determine the geographic orientation of their body coordinates;

[0086] S14. Set up the optical theodolite and fix the optical prism at a suitable position on the four sides of the inner ring, and determine the initial angle position through the optical theodolite.

[0087] Further explanation: In steps S12 and S13, the column 2 and / or inner ring 4 can be adjusted first to determine the body coordinate orientation of the indexing frame, and then the installation work can be completed. More preferably, the body coordinate of the indexing frame... Pointing to the northeast, the corresponding volume coordinates of the inertial navigation system. volume coordinates of the indexing frame Both are parallel, and both use this orientation as their initial orientation, making the navigation coordinate system for calibration reference oriented northeast-southeast. Coordinate system, the calibrated correction parameters are The coordinate reference is used, and the body coordinates of the inertial navigation system are... volume coordinates of the indexing frame The angular deviation of each axis is within ±1°. In step S14, the appropriate position of the four sides of the inner ring is determined so as not to affect the optical aiming path.

[0088] Further, in step S2, after the inertial navigation system (INS) is powered on and stabilized, the INS outputs a set of signals at regular time intervals (e.g., 0.1ms to 1s). These signals include signals related to angular velocity from the fiber optic gyroscope and signals related to acceleration from the quartz accelerometer. These signals are processed using relevant calibration parameters from the factory or before calibration to obtain effective quantities related to angular velocity and acceleration. These effective quantities include… , , , , , ,in For time i Axis gyroscope output value, For time i Axis gyroscope output value, For time i Axis gyroscope output value, For time i Axis accelerometer output value, For time i Axis accelerometer output value, For time i Axis accelerometer output value;

[0089] In step S3, the accelerometers and gyroscopes of the Z1 and Y1 axes are calibrated, including the following steps:

[0090] S301. Perform accelerometer and gyroscope calibration on the Z1 axis. Adjust the inertial navigation system to a stationary state, using the initial position as a reference. The Z1 axis of the inertial navigation system should point in the first direction. When the body coordinate system... When pointing to the northeast geographical direction, the Z1 axis points vertically downwards. Valid data is collected over a certain period to obtain the first valid quantity, which is then combined with the local latitude value. Gravitational acceleration value Earth's rotational angular velocity The heading angle under the current state is calculated using the coarse alignment formula. Pitch angle Roll angle Then, the residual of the first Z1 axis accelerometer was calculated. , ;

[0091] To further explain, the average of the effective quantities over a certain period of time under this state is taken, where, , , , , , The system defaults to a coarse alignment ending with an initial navigation velocity of 0, and a default initial position based on local geographical longitude, latitude, and altitude. More preferably, the effective data acquisition time is 3 minutes.

[0092] S302. Adjust the inertial navigation system to inertial navigation mode, rotate the vehicle around the Z-axis of the inertial navigation system to a designated position, and calculate the actual rotation difference between its current position and its initial position. , the carrier starts to move to stable time T1, the change of the inertial navigation heading angle output by the inertial measurement unit, the actual change of the heading angle measured by the optical theodolite, and the difference between the two ;

[0093] Further, when the inertial measurement unit is converted from the static state to the inertial navigation state, the position parameter in the navigation solution is locked and not updated, and the position information measured in the static state is used as the reference.

[0094] S303, rotate the carrier so that the Z1 axis points to a second direction, which is a vertical upward direction, adjust the inertial measurement unit to a static state, collect a second effective amount, and calculate the 、 , heading angle , pitch angle , roll angle and the residual error of the second Z1 axis accelerometer , ;

[0095] S304, adjust the inertial measurement unit to an inertial navigation state, rotate the carrier around the Z axis of the inertial measurement unit to a specified position, and obtain the actual rotation difference , the time experienced in the inertial navigation stage is T2, and the difference between the change of the navigation heading angle output and the actual change of the heading angle is ;

[0096] Further, in steps S32 and S34, in order to facilitate measurement and calculation, the stand 2 is usually rotated to drive the inertial measurement unit to be calibrated to rotate horizontally for one revolution (i.e. 360°), and the actual rotation difference 、 is measured by aiming the optical theodolite at the optical prism. After the rotation frame is stationary and completely stable, the inertial navigation solution is stopped, so that the time experienced in the inertial navigation segment is the time for the carrier to move to stable, which is T1 and T2.

[0097] S305, calculate the bias residual error of the Z1 axis accelerometer, the zero bias residual error of the Z1 axis gyroscope, and the scale factor correction value of the Z1 axis gyroscope;

[0098] Further, the bias residual error of the Z1 axis accelerometer is

[0099]

[0100] The zero bias residual error of the Z1 axis gyroscope is

[0101]

[0102] Scale factor correction value of Z1 axis gyroscope

[0103]

[0104] S306, accelerometer and gyroscope calibration of Y1 axis is performed, the inner ring 4 is rotated to make the inertial measurement unit Y1 axis point to the first direction, i.e. vertical downward direction, the inertial measurement unit is adjusted to be in a static state, valid data in a certain time is collected, the third valid amount is obtained, and the local latitude value is combined , gravity acceleration value , earth rotation angular velocity , the heading angle in the current state is calculated through the coarse alignment formula , pitch angle , roll angle , then the first Y1 axis accelerometer residual error is calculated , ;

[0105] S307, the inertial measurement unit is adjusted to be in an inertial navigation state, the carrier is rotated around the Y axis of the inertial measurement unit to a specified position, and the actual rotation difference between the current position and the initial position is measured and calculated , the carrier starts to move to be stable, the time is T3, the change amount of the inertial navigation heading angle output, the actual rotation change amount of the heading angle and the difference between the two are obtained ;

[0106] S308, the carrier is rotated to make the Y1 axis point to the second direction, i.e. vertical upward direction, the inertial measurement unit is adjusted to be in a static state, the fourth valid amount is collected, and the , , heading angle in the static state is calculated , pitch angle , roll angle and the second Y1 axis accelerometer residual error are calculated , ;

[0107] S309, the inertial measurement unit is adjusted to be in an inertial navigation state, the carrier is rotated around the Y axis of the inertial measurement unit to a specified position, and the actual rotation difference is obtained , the time experienced in the inertial navigation stage is T4, and the difference between the change amount of the navigation heading angle output and the actual rotation change amount of the heading angle is ;

[0108] Further, in steps S42 and S44, the column 2 is also rotated to drive the inertial measurement unit to be calibrated to rotate 1 week (i.e. 360°), and the actual rotation difference is measured and calculated through the optical theodolite and the optical prism , And after the indexing frame is stationary and completely stable, the inertial navigation solution stops, so that the time experienced by the inertial navigation segment is the time of the carrier moving to stable, which is T3 and T4.

[0109] S310, the bias residual of the Y1 axis accelerometer, the zero bias residual of the Y1 axis gyro and the scale factor correction value of the Y1 axis gyro are calculated;

[0110] Further, the bias residual of the Y1 axis accelerometer

[0111]

[0112] The zero bias residual of the Y1 axis gyro

[0113]

[0114] The scale factor correction value of the Y1 axis gyro

[0115]

[0116] S4, the correction of the X1 axis accelerometer and the X1 axis gyro is carried out, including the following steps:

[0117] S41, rotate the column 2 and / or the inner ring 4, point the Z1 axis of the inertial measurement unit to the first direction, so that the inertial measurement unit restores the front right down state (i.e. the inertial measurement unit body coordinate points to the northeast local position), and at the same time, the Y1 axis gyro, the Y1 axis accelerometer, the Z1 axis gyro and the Z1 axis accelerometer are revised, specifically:

[0118] The effective amount of the Y1 axis gyro output is revised to - The effective amount of the Y1 axis accelerometer output is revised to - The effective amount of the Z1 axis gyro output is revised to - The effective amount of the Z1 axis accelerometer output is revised to - ;

[0119] S42, adjust the inertial measurement unit to a stationary state, collect effective data within a certain time to obtain a fifth effective amount, and take the average to obtain , , , , , , and the heading angle in the current state is calculated by a coarse alignment formula , the pitch angle , the roll angle , and then the first X1-axis accelerometer residual error is calculated , ;

[0120] wherein, , , , is the mean value calculated by averaging the revised effective values;

[0121] S43, adjust the inertial navigation state of the inertial measurement unit, rotate the inner ring 4 clockwise to rotate the inertial measurement unit by 360°, and measure the actual rotation difference between the current position and the initial position by the optical theodolite and the optical prism , and the inertial navigation calculation stops after the rotation frame is stable; the time experienced in the inertial navigation stage is T5, and the difference between the change amount of the navigation roll angle output and the actual roll angle change amount is ;

[0122] S44, rotate the inner ring 4 to rotate the inertial measurement unit by 180° around the X-axis, so that the Z1-axis of the inertial measurement unit points to the second direction, i.e. the vertical upward direction, and the inertial measurement unit is in the front left upper initial state. Adjust the inertial measurement unit to the static state, collect effective data within a certain time, output the sixth effective value, take the mean value, and calculate the current state of , , the heading angle , the pitch angle , the roll angle , and then the second X1-axis accelerometer residual error is calculated , ;

[0123] S45, adjust the inertial measurement unit to the inertial navigation state, rotate the carrier by 360° counterclockwise around the X-axis of the inertial measurement unit, and measure the actual rotation difference , the time experienced in the inertial navigation stage is T6, and the difference between the change amount of the navigation heading angle output and the actual heading angle change amount is ;

[0124] S46, calculate the bias residual error of the X1-axis accelerometer, the zero bias residual error of the X1-axis gyroscope, and the scale factor correction value of the X1-axis gyroscope.

[0125] Further, the bias residual error of the X1-axis accelerometer is

[0126]

[0127] X1 axis gyro zero bias residual error

[0128]

[0129] X1 axis gyro scale factor correction value

[0130]

[0131] S47, complete the revision of the effective amount of gyro output of X1 axis and the effective amount of X1 axis accelerometer output:

[0132] The effective amount of X1 axis gyro output is revised to - The effective amount of X1 axis accelerometer output is revised to - .

[0133] S5, verify the calibration results, rotate the column 2 and / or the inner ring 4, so that the inertial measurement unit body coordinate points to any position, by comparing the effective amount of inertial measurement unit output and the relevant value measured by optical theodolite, confirm whether the calibration result is qualified, if so, output the calibration result, if not, recalibrate.

[0134] Further, in the subsequent application of the inertial measurement unit, the factory calibration parameters are still effective, that is, the effective amount after tool error compensation includes , , , , , , but revised to - , - , - , - , - , - to complete the secondary calibration on the basis of the original calibration parameters.

[0135] The optical fiber strapdown inertial measurement unit free disassembly calibration method and device provided by the application, which proposes an optical fiber strapdown inertial measurement unit free disassembly calibration method, directly installs an aircraft or a functional module cabin section provided with a to-be-calibrated inertial measurement unit in a rotating mechanism, energizes the to-be-calibrated inertial measurement unit, so that the inertial measurement unit outputs collected data information, collects actual rotation information through an optical assembly, combines the two information, performs secondary calibration correction factor calculation, and completes secondary calibration of the inertial measurement unit. The method does not change the calibration parameters before leaving the factory or calibration, but performs secondary calibration on the effective amount of the calibrated output of the inertial measurement unit, so that the carrier loaded with the inertial measurement unit does not need to be disassembled, and the initial calibration parameters do not need to be modified, thereby meeting the free disassembly requirement of the carrier provided with the to-be-calibrated inertial measurement unit, improving the calibration efficiency of the inertial measurement unit, and having good application value. A corresponding inertial measurement unit free disassembly calibration device is also proposed, which includes a first rotating mechanism and a second rotating mechanism, can be rotated in a horizontal plane and a vertical plane respectively, and is provided with an optical measurement assembly corresponding to the actual rotation information measurement, so as to realize the calculation of the secondary calibration revision data.

[0136] Those skilled in the art can easily understand that the above description is only a preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for non-disassembly calibration of fiber optic strapdown inertial navigation systems, characterized in that, Includes the following steps: S1. Install the carrier containing the inertial navigation system to be calibrated in the indexing frame, and set the volume coordinates of the inertial navigation system... volume coordinates of the indexing frame Parallel, with the vertically downward direction as the first direction and the vertically upward direction as the second direction; S2. Power on the inertial navigation system. After the power supply stabilizes, the inertial navigation system can output effective values, including gyroscope output values ​​and accelerometer output values. S3. Perform calibration of the Z1-axis and Y1-axis accelerometers and gyroscopes, including the following steps: A1. Using the axis to be calibrated as the reference axis, rotate the inertial navigation system (INS) until the reference axis points to the first direction, adjust the INS to a stationary state, collect effective data, and calculate the heading angle in the current state. Pitch angle Roll angle Then, the residual of the first fixed-axis accelerometer to be calibrated is calculated. ; A2. Adjust the inertial navigation system to inertial navigation mode, rotate the carrier around the reference axis to a designated position, and measure the actual rotation difference between its current position and its initial position. The time T after the carrier starts moving and stabilizes is used to obtain the difference between the change in the inertial navigation heading angle output and the actual change in the heading angle turned. ; A3. Rotate the carrier so that the reference axis points to the second direction, adjust the inertial navigation system to a stationary state, collect effective data, and calculate the residual of the second calibrated axis accelerometer in this stationary state. ; A4. Adjust the inertial navigation system to inertial navigation mode, rotate the carrier around the reference axis to the designated position, and measure the actual rotation difference. The inertial navigation phase lasts for t, and the difference between the change in the navigation heading angle output and the actual change in the heading angle is... ; A5. Calculate the bias residual of the accelerometer of the axis to be calibrated, the zero bias residual of the gyroscope of the axis to be calibrated, and the scale factor correction value of the gyroscope of the axis to be calibrated. S4. Perform calibration of the X1-axis accelerometer and X1-axis gyroscope, including the following steps: B1. Take any calibrated axis in the inertial navigation system as the reference axis, and revise the calibrated portion of the output effective quantity. B2. Repeat steps A1 to A5 in step 3 to calculate the bias residual of the X1-axis accelerometer, the zero bias residual of the X1-axis gyroscope, and the scale factor correction value of the X1-axis gyroscope. S5. Verify the calibration results and output the calibration results.

2. The fiber optic strapdown inertial navigation system calibration method without disassembly according to claim 1, wherein, The effective quantities output by the inertial navigation system before calibration include and ; in, Let i be the output value of the gyroscope at time i. This is the output value of the accelerometer at time i.

3. The fiber optic strapdown inertial navigation system calibration method without disassembly according to claim 2, wherein, The first and second accelerometer residuals of the Z1 and Y1 axes are obtained by formulas (1) and (2), respectively. （1） （2） in, This indicates that the average value of the accelerometer output values ​​collected over a period of time is calculated using the following formula: .

4. The fiber optic strapdown inertial navigation system calibration method without disassembly according to claim 3, wherein, The first and second accelerometer residuals of the X1 axis are obtained from formulas (3) and (4), respectively. （3） （4） in, This indicates that the average value of the X1-axis accelerometer output values ​​collected over a period of time is calculated.

5. The fiber optic strapdown inertial navigation system calibration method without disassembly according to claim 4, wherein, Accelerometer bias residual The calculation formula is: （5） Zero bias residual of a gyroscope The calculation formula is: （6） Scale factor correction value of the gyroscope The calculation formula is: （7） 。 6. The fiber optic strapdown inertial navigation system calibration method without disassembly according to claim 5, wherein, In step S1, the effective quantity is revised, and the revised gyroscope output value is... The revised formula is as follows: （8） The revised accelerometer output value is The revised formula is as follows: （9）。 7. The method for non-disassembly calibration of fiber optic strapdown inertial navigation systems according to any one of claims 1 to 6, wherein, The rotation performed by the inertial navigation system in inertial navigation mode is a horizontal rotation, and it rotates 360°.

8. The method for non-disassembly calibration of fiber optic strapdown inertial navigation systems according to any one of claims 1 to 6, wherein, In step S6, the inertial navigation system (INS) is rotated so that its volume coordinates point to any position. The volume coordinate orientation pointed to by the INS volume coordinates is measured and compared with the calibrated effective quantity output by the INS to confirm whether the calibration result is qualified. If it is, the calibration result is output; otherwise, the calibration is recalibrated.

9. A fiber optic strapdown inertial navigation system (INS) calibration device that does not require disassembly, used to perform the fiber optic strapdown INS calibration method according to any one of claims 1 to 8, characterized in that, Includes indexing frame and optical measurement components; The indexing frame includes a first rotating mechanism and a second rotating mechanism. The first rotating mechanism includes a base with an annular groove on the top and a column with one end slidingly matched with the annular groove. The other end of the column is fixedly connected to the second rotating mechanism to drive the second rotating mechanism to rotate horizontally. The second rotating mechanism includes an outer ring and an inner ring, wherein the inner ring and the outer ring are slidably connected, allowing the inner ring to rotate relative to the outer ring in a vertical plane. The optical measurement component includes an optical prism and an optical theodolite. The optical prism is fixedly mounted on the inner ring, so that the optical theodolite obtains the rotation information of the inner ring by measuring the position of the optical prism.

10. The fiber optic strapdown inertial navigation system calibration device without disassembly according to claim 9, wherein, The inner ring and the outer ring are cylindrical structures. and / or The base is equipped with a height adjustment bracket at its bottom to achieve leveling of the base.

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