Error self-calibration and compensation method for liquid floated gyroscope platform type inertial navigation system

Abstract

The invention relates to an error self-calibration and compensation method for a liquid floated gyroscope platform type inertial navigation system, which comprises the following steps of: locking a platform body at 13 frame angle positions under the condition of a static base, controlling the platform body to track an inertial coordinate system through a stable loop, and collecting measured values of an accelerometer and a frame angle sensor. And calculating an attitude angle of the table body under an earth coordinate system by using a table body attitude calculation method of an inertial navigation system, and comparing the attitude angle with a table body attitude angle measured by a platform frame angle sensor to obtain an attitude misalignment angle observed quantity. And performing linear fitting on the state misalignment angle sequence of each section of the process of tracking the inertial coordinate system to obtain the comprehensive angular velocity error of the inertial navigation system at the respective calibration position. The total least square algorithm is adopted to solve residual errors of drift error coefficients of all zero-order terms, first-order terms and cross terms, estimated values of measured parameters are corrected, the corrected error coefficient estimated values are used for iterative calculation until an iterative convergence criterion is met, and self-calibration results of all the drift error coefficients are obtained.

Description

Technical Field

[0001] The invention relates to an error self-calibration and compensation method for a liquid floating gyro platform type inertial navigation system, belonging to the technical field of inertial navigation. Background Art

[0002] The inertial navigation system uses accelerometers and gyroscopes to measure the angular and linear motion parameters of the carrier, and obtains the carrier's speed, position, attitude and other information through navigation calculations. According to the way the inertial measurement reference is established, the inertial navigation system can be divided into two categories: platform-based inertial navigation systems and strapdown inertial navigation systems.

[0003] The platform-type inertial navigation system (also known as inertial platform) installs inertial measurement elements (mainly including gyroscopes and accelerometers) on the same inertial measurement assembly (hereinafter referred to as the platform), uses the gyroscope to sense the angular motion of the platform, controls the platform to track the navigation coordinate system through a rotating frame mechanism, and isolates the angular motion of the carrier; then uses the accelerometer to measure the acceleration information (specific force) of the platform in the navigation coordinate system, and uses the navigation computer to perform integral calculations to obtain information such as the speed and position of the platform's movement.

[0004] The liquid-floating gyro platform inertial navigation system is based on the liquid-floating gyro control body tracking navigation coordinate system. The liquid-floating gyro is a type of mechanical rotor gyroscope. It is sensitive to the angular motion of the gyroscope relative to the inertial space based on the gyroscope's fixed axis, precession and other characteristics. It includes full liquid-floating gyroscopes, three-floating gyroscopes, etc. The liquid-floating gyro platform inertial navigation system is currently mainly used in high-precision application fields such as navigation and guidance of long-range missile weapon systems. Common types include three-axis frame platform systems and four-axis frame platform systems. Their typical feature is that the platform tracks the inertial coordinate system.

[0005] In the application of inertial navigation system, it is necessary to compensate the error of inertial instrument to improve navigation accuracy. For inertial navigation system using liquid floating gyroscope, the error coefficient of gyroscope is expressed as drift angular velocity relative to inertial space, including constant drift, drift error proportional to a certain axial overload (first order), drift error proportional to the square of a certain axial overload (second order), and drift error proportional to the product of two axial overloads (cross order), etc. Among them, the second order of gyroscope is generally not significant in 1g gravity field environment, and needs to be calibrated under high overload conditions. Summary of the invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and solve the error self-calibration and compensation problem of a liquid floating gyro platform type inertial navigation system.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] A method for self-calibration and compensation of errors of a liquid-floating gyro platform inertial navigation system is disclosed. Under static base conditions, the platform is locked at 13 frame angle positions, and then the platform is controlled to track the inertial coordinate system through a stabilization loop, and the measurement values ​​of the accelerometer and frame angle sensor are collected. The attitude angle of the platform in the ground coordinate system is calculated by the platform attitude solution method of the inertial navigation system, and compared with the attitude angle of the platform measured by the platform frame angle sensor to obtain the attitude misalignment angle observation. The state misalignment angle sequence of each section of the inertial coordinate system tracking process is linearly fitted to obtain the comprehensive angular velocity error of the inertial navigation system at each calibration position. The total least squares algorithm can be used to calculate the residuals of the drift error coefficients of each zero-order term, first-order term, and cross-term, and the estimated value of the measured parameter is corrected. The corrected error coefficient estimate is used for iterative calculation until the iterative convergence criterion is met to obtain the self-calibration results of each drift error coefficient. 21 error coefficients such as zero-order term, first-order term, and cross-term of the liquid-floating gyro can be calibrated, and the base azimuth of the inertial navigation system can be estimated. Through self-calibration and compensation of error coefficients, the inertial navigation accuracy of the liquid floating platform inertial navigation system and the attitude measurement accuracy of the carrier or base can be improved.

[0009] A method for self-calibration and compensation of errors of a liquid floating gyro platform inertial navigation system, such as Figure 4 As shown, the following steps are included:

[0010] (1) The liquid-floating gyro platform inertial navigation system to be tested is placed on a stable foundation with seismic isolation, such as a marble slab or a turntable, so that the horizontal attitude angle of the inertial navigation system base is less than 3°. By adjusting the attitude angle of the inertial navigation system base and controlling the frame transfer mechanism, the inertial navigation system frame orientation is adjusted as follows: Figure 1 For a four-axis platform inertial measurement system, one axis needs to be locked so that it works in three-axis mode. Figure 1 The following table shows the definition of the polarity of the accelerometer's X, Y, and Z channels and input axes: p , Z p The axes are perpendicular to each other in a nearly horizontal position, Y p Axis perpendicular to X p OZ p Plane, X p , Y p , Z p According to the right-hand rule, an orthogonal coordinate system is formed, pointing to the front, top, and right directions of the platform coordinate system. The zero position of the frame angle sensor is defined as: when the output of the frame angle sensor of the inertial navigation system is zero, the base coordinate system and the platform coordinate system are approximately coincident, with the same polarity, and X p , Y p , Z p They point to the front, top, and right directions of the base coordinate system respectively, X p , Yp , Z p Respectively with X F , Y F , Z F Parallel, with the same polarity. Assume that the range of the frame angle sensor measurement value is [0,360°].

[0011] (2) Control the rotation frame of the inertial navigation system, lock the platform at the frame angle positions shown in Table 1 below, and after the locking is stable, make the system work in the navigation application working mode of tracking the inertial coordinate system, that is, the rotation control loop of the inertial navigation system controls the platform to be stable in the inertial space based on the angular motion information sensitive to the gyroscope. At this time, the angular velocity of the platform relative to the inertial space is composed of drift errors such as the gyroscope constant drift, first-order terms, and cross terms. The measurement value of the inertial navigation system frame angle sensor is collected at a frequency of more than 10 Hz for no less than 3 minutes, in units of: °. There is no requirement for the order of the frame angle positions locked for data acquisition in Table 1.

[0012] Table 1 Initial values ​​of the angular position of the self-calibrated locking frame of the inertial navigation system

[0013] Position number Outer ring frame angle (°) Center frame angle (°) Inner ring frame angle (°) 1 0 0 0 2 0 0 90 3 0 0 180 4 0 0 270 5 270 0 0 6 180 0 0 7 90 0 0 8 90 <![CDATA[β1]]> 0 9 90 <![CDATA[360-β1]]> 0 10 <![CDATA[β2]]> 0 0 11 <![CDATA[360-β2]]> 0 0 12 0 0 <![CDATA[β3]]> 13 0 0 <![CDATA[360-β3]]>

[0014] Among them, β j The value can be in the range of [5°,85°], usually 15°≤|β j |≤75°, j=1,2,3.

[0015] For inertial measurement systems with different frame orientations, this requirement may not be required. Figure 1 The frame orientation shown in the figure, but the initial angular position relationship between the inertial measurement system platform and the base during the self-calibration process needs to be the same as Figure 1 Same as described in Table 1.

[0016] (3) Perform self-alignment of the inertial navigation system and determine the azimuth angle α of the inertial navigation system base p . (Take north by west as positive, that is, α p It is the angle from geographic north to the X direction of the inertial navigation system base in a counterclockwise direction.

[0017] (4) Calculate the error coefficient measurement matrix of each calibration position and form the overall error coefficient measurement matrix. Suppose the direction cosine matrix expression from the platform coordinate system to the single-axis turntable base coordinate system in the ideal case is:

[0018]

[0019] In the formula, c ij For the elements of this direction cosine matrix, are the outer ring, middle ring, and inner ring frame angle values ​​of the kth row in Table 1, respectively. Then the error coefficient observation matrix H of the kth self-calibration locking position is (k) The calculation method is

[0020]

[0021] In the formula, H (k) Medium ij The calculation result at the kth position should be taken. The superscript T indicates the transpose of the matrix.

[0022] The expression of the error coefficient overall observation matrix is:

[0023]

[0024] (5) Calculate the direction cosine matrix from the platform coordinate system p to the geographic coordinate system g at the initial moment of tracking the inertial coordinate system navigation at each calibration position:

[0025]

[0026] In the formula, The base attitude matrix determined for the inertial navigation system self-alignment, It is the direction cosine matrix from the platform coordinate system p to the geographic coordinate system g at the initial time t0 of each location navigation, and the expression is

[0027]

[0028] Where k = 1, 2, ... 9; They are the measured values ​​of the outer ring, middle ring, and inner ring frame angle sensors, in rad; are the zero bias of the middle ring and inner ring frame angles, in rad, j=1,2,3; γ ij is the frame non-orthogonality error angle, unit: rad,i,j=x,y,z.

[0029] (6) Define the navigation coordinate system i (inertial coordinate system) to coincide with the geographic coordinate system g at the initial time. Then the direction cosine matrix from the platform coordinate system p to the inertial coordinate system i at the initial time is:

[0030]

[0031] (7) At each calibration position, the inertial navigation attitude solution is performed periodically using the measurement values ​​of the inertial navigation system accelerometer during the entire process of tracking the inertial coordinate system navigation. The specific method is as follows:

[0032] The accelerometer measurement value at time t is used to calculate the specific force measurement value of the inertial navigation system in the platform coordinate system at each locked position. The expression of the specific force measurement value at time t at the kth position is:

[0033]

[0034] Where, k = 1, 2, ... 13; K 0j is the zero bias of the accelerometer in the j direction, unit: pulse number / s; K 1j E is the accelerometer scale factor, unit: pulse number / (s·g0); ij is the installation error angle, which indicates the influence of the i-direction specific force on the j-direction accelerometer measurement value, unit: rad; Δ nj is the asymmetric scale error coefficient of the accelerometer in the j direction, unit: 1, i, j = x, y, z; calibration parameter K 0j ,E ij ,Δ nj The initial value of K is 0. 1j The initial value is the factory nominal value of the instrument. The output value of the accelerometer at the kth position at time t, unit: number of pulses / s.

[0035] The angular velocity of the platform relative to the inertial space can be calculated from the gyroscope drift mathematical model:

[0036]

[0037] Where D 0j is the zero-order drift error coefficient of the gyroscope, unit: ° / h; D ij D is the first-order drift error coefficient of the gyroscope, unit: ° / h / g; i2j is the cross-term drift error coefficient related to the product of the overload of the j gyroscope and the two axes other than the i axis of the platform coordinate system, unit: ° / h / g 2 ;

[0038] Calculate the direction cosine matrix from the platform coordinate system p to the inertial coordinate system i at time t+Δt The expression is

[0039]

[0040] In the formula, ω j for The j-direction component of

[0041] Calculate the direction cosine matrix from the inertial coordinate system i to the geographic coordinate system g at time t+Δt The expression is

[0042]

[0043] In the formula, ω ie is the angular velocity of the earth, and L is the local latitude. Then the direction cosine matrix from the platform coordinate system p to the geographic coordinate system g is The expression is

[0044]

[0045] (8) Use the inertial navigation system frame angle sensor measurement value at time t+Δt to calculate the direction cosine matrix from the platform coordinate system p to the geographic coordinate system g

[0046]

[0047] In the formula, m3 is the inner ring frame coordinate system, m2 is the middle ring frame coordinate system, and m1 is the outer ring frame coordinate system. The expressions of each matrix factor are as follows:

[0048] ① The direction cosine matrix from the platform coordinate system to the inner ring frame coordinate system is

[0049]

[0050] In the formula, γ zx ,γ zy is the non-orthogonal error angle of the inner ring frame.

[0051] ② The direction cosine matrix from the inner ring frame coordinate system to the middle ring frame coordinate system is

[0052]

[0053] In the formula, γ yz is the non-orthogonal error angle of the middle ring frame, is the measurement value of the inner ring frame angle sensor at time t+Δt, It is the zero bias of the inner ring frame angle sensor.

[0054] ③ The direction cosine matrix from the middle ring frame coordinate system to the outer ring frame coordinate system is

[0055]

[0056] In the formula, γ xy is the non-orthogonal error angle of the table axis, is the measured value of the ring frame angle sensor at time t+Δt, It is the zero bias of the center ring frame angle sensor.

[0057] ④ The direction cosine matrix from the outer ring frame coordinate system to the base coordinate system is

[0058]

[0059] In the formula, It is the measurement value of the outer ring frame angle sensor at time t+Δt.

[0060] (9) Since the attitude angle of the platform base coordinate system measured by the frame angle sensor is not affected by the gyroscope drift error, it can be used as a reference for the error angle of the inertial coordinate system attitude measurement tracked by the gyroscope control stabilization loop. The attitude misalignment angle expression of the optical liquid floating gyro platform inertial navigation system at time t+Δt is calculated as follows:

[0061]

[0062] In the formula, φ j is the attitude misalignment angle of the inertial navigation system in the j direction, j = x, y, z.

[0063] (10) The attitude misalignment angle of all N navigation calculation cycles in each flight navigation process is calculated, and the comprehensive drift error angular velocity of each calibration position is calculated using a linear fitting algorithm. The expression of the j-direction comprehensive drift error angular velocity of the inertial navigation system at the kth position is:

[0064]

[0065] Where, j = x, y, zn = 1, 2, 3, ..., N, N is the number of navigation calculation cycles at each position; Δt is the navigation calculation cycle, unit: s; the angular velocity vector of the integrated drift error at the kth position is

[0066]

[0067] (11) The estimated value of the error coefficient is obtained using the total least squares algorithm:

[0068] X=(H T H) -1 H T Z=[X1 X2 … X 22 ] T

[0069] In the formula, Z is The total observation quantity composed of

[0070]

[0071] (12) The estimated values ​​of the calibrated parameters and the base attitude angle are corrected using the least squares estimation results. The calculation method is as follows:

[0072] Base azimuth:

[0073]

[0074] Gyroscope zero-order term:

[0075] D fx | (l+1) =D fx |(l) +X2

[0076] D fy | (l+1) =D fy | (l) +X3

[0077] D fz | (l+1) =D fz | (l) +X4

[0078] Gyroscope first order term:

[0079] D xx | (l+1) =D xx | (l) +X5

[0080] D xy | (l+1) =D xy | (l) +X6

[0081] D xz | (l+1) =D xz | (l) +X7

[0082] D yx | (l+1) =D yx | (l) +X8

[0083] D yy | (l+1) =D yy | (l) +X9

[0084] D yz | (l+1) =D yz | (l) +X 10

[0085] D zx | (l+1) =D zx | (l) +X 11

[0086] D zy | (l+1) =D zy | (l) +X 12

[0087] D zz | (l+1) =Dzz | (l) +X 13

[0088] Gyroscope cross term:

[0089] D x2x | (l+1) = D x2x | (l) +X 14

[0090] D y2x | (l+1) = D y2x | (l) +X 15

[0091] D z2x | (l+1) = D z2x | (l) +X 16

[0092] D x2y | (l+1) = D x2y | (l) +X 17

[0093] D y2y | (l+1) = D y2y | (l) +X 18

[0094] D z2y | (l+1) = D z2y | (l) +X 19

[0095] D x2z | (l+1) = D x2z | (l) +X 20

[0096] D y2z | (l+1) = D y2z | (l) +X 21

[0097] D z2z | (l+1) = D z2z | (l) +X 22

[0098] In the above formulas, l is the number of iterative calculations, representing the result of the lth error separation, l = 0, 1, 2, ..., where l = 0 represents the initial value of the error coefficient.

[0099] (13) Iterate the calculation using the corrected error coefficient estimate, i.e. repeat steps (5) to (12) until each component X of the correction value X (least squares estimation result) is i All satisfy the iterative convergence criterion: (X i is the convergence criterion value of the i-th dimension component), then the estimated values ​​of the error coefficients after the current least squares estimation result is corrected are the self-calibration results of the error coefficients. (i=1,2,…,22) In engineering applications, the number of iterations N can generally be directly set to 5 to 10 times.

[0100] Compared with the prior art, the present invention has the following beneficial effects:

[0101] The present invention can realize the self-calibration of all zero-order terms, first-order terms and cross-term drift error coefficients for the liquid floating gyro platform inertial navigation system, and can accurately estimate the azimuth of the base of the inertial navigation system. Through the self-calibration and compensation of the error coefficient, the inertial navigation accuracy of the liquid floating platform inertial navigation system and the attitude measurement accuracy of the carrier or base can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0102] Figure 1 This is the frame orientation of the frame-type inertial navigation system of the present invention.

[0103] Figure 2 It is the measurement value curve of the frame angle sensor in the process of tracking the inertial space at each calibration position simulated and generated in the simulation verification of the present invention.

[0104] Figure 3 It is the measurement value curve of the accelerometer in the process of tracking the inertial space at each calibration position simulated and generated in the simulation verification of the present invention.

[0105] Figure 4 It is a schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0106] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0107] Based on simulation experiments, the specific implementation methods and application effects of the present invention are given. A method for self-calibration and compensation of errors of a liquid floating gyro platform inertial navigation system is provided. Assume that the frame orientation of the inertial navigation system is as follows: Figure 1As shown. Assume that all error coefficients of the inertial navigation system are normally distributed random constants: the accelerometer equivalent value range is 5000±50 pulses / (s·g0), and the error range of the nominal value used in this calibration method is [-1e-5,1e-5]; the accelerometer zero bias value range is [-0.25,0.25] pulses / s, and the error range of the nominal value used in this calibration method is [-1e-5,1e-5]; the accelerometer asymmetric scale error range is [-1e-5,1e-5]g0; the accelerometer installation error range is [-180,180] arc seconds, and the error range of the nominal value used in this calibration method is is [-5,5] arc seconds; the value range of the frame non-orthogonality error angle is [-180,180] arc seconds, and the error range of the nominal value used in this calibration method is [-5,5] arc seconds; the zero bias value range of the frame angle sensor is [-180,180] arc seconds, and the error range of the nominal value used in this calibration method is [-5,5] arc seconds; the horizontal attitude angle range of the inertial navigation system base is [-3°,3°], and the azimuth angle of the base is uniformly distributed in the range of [0°,360°). The error range of the self-alignment result used in this calibration method is [-5,5] arc seconds for the horizontal alignment error and [-60,60] arc seconds for the azimuth alignment error. Assume that the gyroscope drift error coefficients to be calibrated in the inertial navigation system are all normally distributed random constants, the value range of the zero-order term is [-0.1, 0.1]° / h, the value range of the first-order term is [-0.1, 0.1]° / h / g0, and the value range of the cross term is [-0.1, 0.1]° / h / g0 2 The initial values ​​of self-calibration for zero-order terms, first-order terms, and cross terms are all 0.

[0108] The self-calibration locking frame angular positions used for self-calibration are shown in Table 2 below.

[0109] Table 2 Initial values ​​of the angular position of the self-calibrated locking frame of the inertial navigation system

[0110] Position number Outer ring frame angle (°) Center frame angle (°) Inner ring frame angle (°) 1 0 0 0 2 0 0 90 3 0 0 180 4 0 0 270 5 270 0 0 6 180 0 0 7 90 0 0 8 90 30 0 9 90 330 0 10 30 0 0 11 330 0 0 12 0 0 30 13 0 0 330

[0111] The angular position relationship of the platform relative to the geographic coordinate system is simulated according to the angular velocity model of the liquid floating gyro drift of the platform inertial navigation system. The real-time output value of each frame angle sensor is calculated according to the mathematical model of the platform frame angle direction cosine matrix and the non-orthogonal error model of the frame angle axis system. The gravity acceleration is projected to the platform coordinate system to obtain the actual sensitive specific force of the accelerometer combination. The real-time measurement value of the accelerometer specific force at each calibration position is calculated according to the accelerometer specific force output error model. The data sampling frequency is 100Hz, and the data collection time for each position is 3 minutes. The accelerometer output value and frame angle output value of each segment of the inertial coordinate system tracking process generated by the simulation are as follows: Figure 2 , Figure 3 shown.

[0112] Before the self-calibration process begins, the self-alignment of the liquid floating gyro platform inertial navigation system is performed to determine the attitude angle of the platform base. Here is an analytical rough alignment method: (The principle is a well-known technology in the field of inertial navigation and is not a feature of the present invention.)

[0113] The platform inertial navigation system is locked at the zero position of the frame angle through the stabilization loop torque control. After the lock is stable, the accelerometer measurement value and gyroscope torque current are collected for 3 minutes. (In the torque lock stable state, the torque current of the liquid floating gyroscope is equivalent to its angular velocity measurement value.) Calculate the average value of the specific force vector measurement value of the three accelerometers (Unit: m / s 2 ) and the average of the angular velocity measurement vectors of the three gyroscopes (Unit: rad / s). Then the calculation method of the platform attitude matrix for locking the frame angle zero position is:

[0114]

[0115] The attitude matrix calculation method of the inertial navigation system base is:

[0116]

[0117] The method of steps (2) to (11) of the present invention is applied to process the simulated accelerometer measurement values, and the number of iterations N is taken as 10. The self-calibration results obtained are shown in Table 3 below.

[0118] Table 3 Self-calibration simulation test results

[0119]

[0120]

[0121] The simulation test results verify the effectiveness of the method of the present invention.

[0122] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

[0123] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for self-calibration and compensation of errors of a liquid floating gyro platform inertial navigation system, characterized in that: include: (1) The liquid-floating gyro platform inertial navigation system to be tested is placed on a stable foundation with seismic isolation, so that the horizontal attitude angle of the inertial navigation system base is less than 3°; (2) Control the rotating frame of the inertial navigation system, lock the platform at 13 different frame angle positions, and collect the measurement values ​​of the inertial navigation system frame angle sensor; (3) Perform self-alignment of the inertial navigation system and determine the azimuth angle of the inertial navigation system base; (4) Calculate the error coefficient observation matrix of each calibration position and form the overall error coefficient observation matrix; (5) Calculate the direction cosine matrix from the platform coordinate system to the geographic coordinate system at the initial moment of tracking the inertial coordinate system navigation at each calibration position; (6) Define the coincidence of the navigation coordinate system and the geographic coordinate system at the initial time, and determine the direction cosine matrix from the platform coordinate system to the inertial coordinate system at the initial time; (7) At each calibration position, periodically perform inertial navigation attitude solution using the measurements of the inertial navigation system accelerometer during the entire process of tracking inertial coordinate system navigation; (8) Calculate the direction cosine matrix from the platform coordinate system to the geographic coordinate system using the inertial navigation system frame angle sensor measurement value; (9) calculating the attitude misalignment angle of the optical liquid floating gyro platform type inertial navigation system according to the reference datum of the error angle of the inertial coordinate system attitude measurement tracked by the gyro control stabilization loop; (10) Calculate the attitude misalignment angle of all N navigation calculation cycles in each flight navigation process, calculate the comprehensive drift error angular velocity of each calibration position using a linear fitting algorithm, and determine the comprehensive drift error angular velocity of the inertial navigation system in different directions at each calibration position; (11) Use the total least squares algorithm to obtain an estimate of the error coefficient; (12) Correcting the estimated values ​​of the calibrated parameters and the base attitude angle using the estimated value of the error coefficient; (13) Perform iterative calculation using the corrected estimated value and repeat steps (5) to (12) until the correction amount in the estimated value of the error coefficient meets the iterative convergence criterion.

2. The error self-calibration and compensation method of the liquid floating gyro platform inertial navigation system according to claim 1, characterized in that: In step (2), the inertial navigation system self-calibrates the locked frame angle position as shown in the following table: There is no requirement for the order of the frame angle positions locked for data acquisition in the table.

3. The error self-calibration and compensation method of the liquid floating gyro platform inertial navigation system according to claim 2, characterized in that: In step (4), the direction cosine matrix expression from the platform coordinate system to the single-axis turntable base coordinate system in the ideal case is: In the formula, c ij For the elements of this direction cosine matrix, are the outer ring, middle ring, and inner ring frame angle values ​​of the kth row in Table 1, respectively. Then the error coefficient observation matrix H of the kth self-calibration locking position is (k) The calculation method is: In the formula, H (k) Medium ij The calculation result at the kth position should be taken; the superscript T indicates the transpose of the matrix; The expression of the error coefficient overall observation matrix is:

4. The error self-calibration and compensation method of the liquid floating gyro platform inertial navigation system according to claim 3, characterized in that: In step (5), the direction cosine matrix of the initial moment of the platform coordinate system p to the geographic coordinate system g at each calibration position tracking inertial coordinate system navigation is: In the formula, The base attitude matrix determined for the inertial navigation system self-alignment, It is the direction cosine matrix from the platform coordinate system p to the geographic coordinate system g at the initial time t0 of each location navigation, and the expression is: Where k = 1, 2, ... 9; They are the measured values ​​of the outer ring, middle ring, and inner ring frame angle sensors respectively; are the zero bias angles of the middle and inner ring frames, j = 1, 2, 3; γ ij is the frame non-orthogonal error angle, i, j = x, y, z.

5. The error self-calibration and compensation method of the liquid floating gyro platform inertial navigation system according to claim 4, characterized in that: In step (7), at each calibration position, the inertial navigation attitude solution is performed periodically using the measurement value of the inertial navigation system accelerometer during the whole process of tracking the inertial coordinate system navigation. The specific method is as follows: The accelerometer measurement value at time t is used to calculate the specific force measurement value of the inertial navigation system in the body coordinate system of each locked position. The expression of the specific force measurement value at time t at the kth position is: Where, k = 1, 2, ... 13; K 0j is the zero bias of the accelerometer in the j direction; K 1j is the accelerometer scale factor; E ij is the installation error angle, which indicates the influence of the i-direction specific force on the j-direction accelerometer measurement value; Δ nj is the asymmetric scaling error coefficient of the accelerometer in the j direction, i,j = x, y, z; calibration parameter K 0j ,E ij ,Δ nj The initial value of K is 0. 1j The initial value of is the factory nominal value of the instrument; is the output value of the accelerometer at the kth position at time j; The angular velocity of the platform relative to the inertial space can be calculated from the gyroscope drift mathematical model: Where D 0j is the zero-order drift error coefficient of the gyroscope; D ij is the first-order drift error coefficient of the gyroscope; D i2j is the cross-term drift error coefficient related to the product of the overloads of the j gyroscope and the two axes other than the i axis of the platform coordinate system; Calculate the direction cosine matrix from the platform coordinate system p to the inertial coordinate system i at time t+Δt The expression is In the formula, ω j for The j-direction component of Calculate the direction cosine matrix from the inertial coordinate system i to the geographic coordinate system g at time t+Δt The expression is In the formula, ω ie is the angular velocity of the earth, L is the local latitude; then the direction cosine matrix from the platform coordinate system p to the geographic coordinate system g The expression is 6. The error self-calibration and compensation method of the liquid floating gyro platform inertial navigation system according to claim 5, characterized in that: In step (8), the direction cosine matrix from the platform coordinate system p to the geographic coordinate system g is calculated using the inertial navigation system frame angle sensor measurement value at time t+Δt: Where m3 is the inner ring frame coordinate system, m2 is the middle ring frame coordinate system, and m1 is the outer ring frame coordinate system; the expressions of each matrix factor are as follows: ① The direction cosine matrix from the platform coordinate system to the inner ring frame coordinate system is In the formula, γ zx ,γ zy is the non-orthogonal error angle of the inner ring frame; ② The direction cosine matrix from the inner ring frame coordinate system to the middle ring frame coordinate system is In the formula, γ yz is the non-orthogonal error angle of the middle ring frame, is the measurement value of the inner ring frame angle sensor at time t+Δt, It is the zero bias of the inner ring frame angle sensor; ③ The direction cosine matrix from the middle ring frame coordinate system to the outer ring frame coordinate system is In the formula, γ xy is the non-orthogonal error angle of the table axis, is the measured value of the ring frame angle sensor at time t+Δt, Zero bias for the center ring frame angle sensor; ④ The direction cosine matrix from the outer ring frame coordinate system to the base coordinate system is In the formula, It is the measurement value of the outer ring frame angle sensor at time t+Δt.

7. The error self-calibration and compensation method of a liquid floating gyro platform inertial navigation system according to claim 6, characterized in that: In step (9), since the attitude angle of the platform base coordinate system measured by the frame angle sensor is not affected by the gyroscope drift error, it can be used as a reference for the error angle of the inertial coordinate system attitude measurement tracked by the gyroscope control stabilization loop. The attitude misalignment angle expression of the optical liquid floating gyro platform inertial navigation system at time t+Δt is calculated as follows: In the formula, φ j is the attitude misalignment angle of the inertial navigation system in the j direction, j = x, y, z.

8. The error self-calibration and compensation method of the liquid floating gyro platform inertial navigation system according to claim 7, characterized in that: In step (10), the attitude misalignment angle of all N navigation calculation cycles in each flight navigation process is calculated, and the comprehensive drift error angular velocity of each calibration position is calculated using a linear fitting algorithm. The expression of the j-direction comprehensive drift error angular velocity of the inertial navigation system at the kth position is: Where, j = x, y, zn = 1, 2, 3, ..., N, N is the number of navigation calculation cycles at each position; Δt is the navigation calculation cycle; the angular velocity vector of the integrated drift error at the kth position is 9. The error self-calibration and compensation method of the liquid floating gyro platform inertial navigation system according to claim 8, characterized in that: In step (11), the total least squares algorithm is used to find the estimated value of the error coefficient: X =(H T H) -1 H T Z=[X1 X2 … X 22 ] T In the formula, Z is The total observation quantity composed of 10. The error self-calibration and compensation method of the liquid floating gyro platform inertial navigation system according to claim 9, characterized in that: In step (12), the least squares estimation result is used to correct the estimated value of the calibrated parameter and the base attitude angle. The calculation method is as follows: Base azimuth: Gyroscope zero-order term: D fx | (l+1) =D fx | (l) +X2 D fy | (l+1) =D fy | (l) +X3 D fz | (l+1) =D fz | (l) +X4 Gyroscope first order term: D xx | (l+1) =D xx | (l) +X5 D xy | (l+1) =D xy | (l) +X6 D xz | (l+1) =D xz | (l) +X7 D yx | (l+1) =D yx | (l) +X8 D yy | (l+1) =D yy | (l) +X9 D yz | (l+1) =D yz | (l) +X 10 D zx | (l+1) =D zx | (l) +X 11 D zy | (l+1) =D zy | (l) +X 12 D zz | (l+1) =D zz | (l) +X 13 Gyroscope cross terms: D x2x | (l+1) =D x2x | (l) +X 14 D y2x | (l+1) =D y2x | (l) +X 15 D z2x | (l+1) =D z2x | (l) +X 16 D x2y | (l+1) =D x2y | (l) +X 17 D y2y | (l+1) =D y2y | (l) +X 18 D z2y | (l+1) =D z2y | (l) +X 19 D x2z | (l+1) =D x2z | (l) +X 20 D y2z | (l+1) =D y2z | (l) +X 21 D z2z | (l+1) =D z2z | (l) +X 22 In the above formulas, l is the number of iterative calculations, representing the result of the lth error separation, l = 0, 1, 2, ..., where l = 0 represents the initial value of the error coefficient.

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