Optical fiber compass and magnetic compass integrated calibration method

Abstract

The invention relates to the field of marine navigation, in particular to an optical fiber compass and magnetic compass integrated calibration method, which comprises the following steps of: compensating a magnetic compass by using an optical fiber compass, and constraining course output of the optical fiber compass by using the magnetic compass as an observed quantity. According to the optical fiber compass and magnetic compass integrated calibration method provided by the invention, the working characteristics of the optical fiber compass and the magnetic compass are combined, so that the optical fiber compass and the magnetic compass are mutually complemented and mutually calibrated, the system reliability is improved, and the system precision can be improved through data fusion.

Description

Technical Field

[0001] The invention relates to the technical field of ship navigation, and in particular to an integrated calibration method for an optical fiber compass and a magnetic compass. Background Art

[0002] Compass is an instrument used to determine the heading of a ship. It is widely used in marine navigation to ensure the safe navigation of ships. The fiber optic compass senses the angular motion of the ship through the fiber optic gyroscope, uses the earth's rotation information, and calculates the heading and attitude information of the carrier in the local geographic coordinate system through a strapdown mathematical platform.

[0003] A magnetic compass is a device that uses the earth's magnetic field to observe the geographic position and heading of a ship. The two are usually used in parallel on ships: the fiber optic compass uses the compass effect to perform horizontal leveling and heading correction, and has the advantage of good dynamic performance, but the heading accuracy depends on the operation of the compass loop and the Kalman filter, and its long-term stability needs to be improved; while the magnetic compass is susceptible to interference and its output accuracy is poor. Summary of the invention

[0004] In order to ensure the reliability of the navigation system and improve the system accuracy, the present invention provides an integrated calibration method for a fiber optic compass and a magnetic compass. Combining the working characteristics of the fiber optic compass and the magnetic compass, a magnetic sensor measurement module and a data fusion calculation module are added. The fiber optic compass and the magnetic compass complement and calibrate each other, which not only increases the system reliability, but also improves the system accuracy through data fusion.

[0005] A method for integrating a fiber optic compass and a magnetic compass, comprising the following steps:

[0006] S1, constructing a magnetic compensation algorithm based on the influence of complex magnetic environment on the magnetic compass and the angle data actually output by the fiber optic compass;

[0007] S2, when the integrated fiber optic compass and magnetic compass device enters a working state, determining a working calibration mode of the integrated fiber optic compass and magnetic compass device, wherein the working calibration mode includes a magnetic calibration mode and a fiber optic compass calibration mode;

[0008] When the integrated fiber optic compass and magnetic compass device enters the magnetic calibration mode, the information currently output by the fiber optic compass and the local magnetic field information of the current position of the ship are substituted into the magnetic compensation algorithm to calculate the compensated true north heading output by the magnetic compass;

[0009] When the integrated fiber optic compass and magnetic compass device enters the fiber optic compass calibration mode, the measurement result of the fiber optic compass is corrected by using the compensated true north heading output by the magnetic compass through the Kalman filter algorithm.

[0010] Preferably, the specific steps of constructing a magnetic compensation algorithm in step S1 according to the influence of the complex magnetic environment on the magnetic compass and the angle data actually output by the fiber optic compass are:

[0011] The true value of the local magnetic field is calculated based on the angle data actually output by the fiber optic compass and the projection of the local magnetic field in the east, north and sky directions;

[0012] According to the actual value of the local magnetic field and the magnetic field data actually measured by the magnetic compass, a magnetic compensation calculation formula is derived to compensate the magnetic field data measured by the magnetic compass using the angle data actually output by the optical fiber compass;

[0013] The compensation calculation formula of the true north heading of the magnetic compass is calculated by using the compensated magnetic field data output by the magnetic compass and the magnetic declination of the local magnetic field.

[0014] Preferably, the specific steps of calculating the true value of the local magnetic field based on the angle data actually output by the fiber optic compass and the projections of the local magnetic field in the east, north and sky directions are:

[0015] First, according to the angle data actually output by the fiber optic compass, the navigation coordinate system X is obtained. n Y n Z n To the carrier coordinate system X b Y b Z b The coordinate transformation matrix

[0016] Then, according to the coordinate transformation matrix The true value of the local magnetic field is calculated by the projection of the local magnetic field in the east, north and sky directions.

[0017] Preferably, the coordinate transformation matrix The calculation formula is:

[0018]

[0019] Among them, ψ is the heading angle actually output by the fiber optic compass, θ is the pitch angle actually output by the fiber optic compass, and γ is the roll angle actually output by the fiber optic compass;

[0020] The calculation formula for the true value of the local magnetic field is:

[0021]

[0022] Among them, [M E M N M U ] T It is the projection of the local magnetic field in the east, north and sky directions.

[0023] Preferably, the specific steps of deriving the magnetic compensation calculation formula according to the true value of the local magnetic field and the magnetic field data actually measured by the magnetic compass are:

[0024] Considering the influence of complex magnetic environment on the magnetic compass, the magnetic field data actually output by the magnetic compass can be expressed as:

[0025]

[0026] Among them, [M x M y M z ] T is the projection of the magnetic field intensity actually output by the magnetic compass in the x, y, and z directions, [H x H y H z ] T is the true value of the local magnetic field, and B0 represent the effects of soft magnetic interference and hard magnetic interference on the magnetic field, respectively;

[0027] Formula (3) can be further expressed as:

[0028]

[0029] in,

[0030] Substituting the actual value of the local magnetic field and the magnetic field data actually measured by the magnetic compass into formula (4) we can obtain the relationship between the ferromagnetic interference coefficients A and B;

[0031] The relationship between the ferromagnetic interference coefficients A and B is fitted by least squares, and the ferromagnetic interference coefficients A and B are calculated;

[0032] Substituting the ferromagnetic interference coefficients A and B into formula (4) yields a magnetic compensation calculation formula for compensating the magnetic field data actually measured by the magnetic compass using the angle output by the fiber optic compass.

[0033] Preferably, the specific steps of obtaining the true north heading compensation calculation formula of the magnetic compass using the compensated magnetic field data output by the magnetic compass and the magnetic declination of the local magnetic field are:

[0034] Projection of the magnetic compass output in the x and y directions after compensation and Calculate the magnetic heading angle;

[0035] According to the magnetic heading angle and the magnetic declination of the local magnetic field, the true north heading compensation calculation formula of the magnetic compass is obtained.

[0036] Preferably, the calculation formula of the magnetic heading angle is:

[0037]

[0038] in, is the projection of the output of the magnetic compass in the x and y directions after compensation;

[0039] The calculation formula for the true north heading compensation of the magnetic compass is:

[0040]

[0041] Among them, ψ M is the compensated true north heading output by the magnetic compass, ψ M0 is the local magnetic declination, which is obtained by looking up the table according to the longitude and latitude output by the fiber optic compass.

[0042] Preferably, in step S2, the specific steps of correcting the measurement result of the fiber optic compass using the compensated true north heading output by the magnetic compass through the Kalman filter algorithm are:

[0043] Selecting the INS navigation parameter error and the drift error of the inertial sensor as the state vector of the filter, we can get

[0044]

[0045] Considering the noise of the magnetic compass, the observation equation of the magnetic compass is:

[0046] Z(t)=H(t)x(t)+υ(t)(8)

[0047] H(t)=[0 1×2 10 1×18 ] 1×21 (9)

[0048] The observed quantity actually measured by the magnetic compass is:

[0049] Z(t)=ψ INS -ψ M (10)

[0050] Among them, ψ M is the compensated true north heading output by the magnetic compass, ψ INS is the heading value output by the fiber optic compass.

[0051] According to formulas (7)-(10), the state variable x(t) is estimated in real time based on the Kalman filter algorithm, and the measurement results of the fiber optic compass are corrected in an open loop.

[0052] Preferably, the state vector component process of the filter is:

[0053] The disturbance analysis of the measurement results of the fiber optic compass is carried out, and the high-order terms of the basic error are omitted. The linearized inertial navigation attitude, velocity, and position error equations are obtained as follows:

[0054]

[0055] In the formula, α, δv n ,δp n Represents three-dimensional attitude, velocity, and position error.

[0056] M pv With M pp The rest of the elements in are zero, L is the local latitude, R M , R N are the meridian radius and the zodiac radius respectively, h is the ship's altitude, v E 、v N are the eastward and northward speeds of the ship, respectively;

[0057] The drift error of fiber optic compass and accelerometer can be modeled as:

[0058]

[0059] Constant zero bias ε b and It can be expressed as:

[0060]

[0061] First-order Gauss-Markov process ε r and It can be expressed as:

[0062]

[0063] The state vector of the filter is constructed based on the inertial navigation attitude, velocity, and position error equations after the linearization of the fiber optic compass and the drift errors of the fiber optic compass and accelerometer:

[0064]

[0065] The system state equation of the inertial navigation system is:

[0066]

[0067] In the formula, the sub-matrix F 12 ~F 33 is the expanded form of formula (11), where 0 represents a 3×3 zero matrix.

[0068]

[0069] Where I is a 3×3 unit matrix, [w gx wgy w gz w ax w ay w az ] T is the fiber optic gyro compass and accelerometer white noise in the x, y, and z directions, [w rgx w rgy w rgz w rax w ray w raz ] T is the first-order Gauss-Markov process noise of the fiber optic gyro compass and accelerometer in the x, y, and z directions.

[0070] In summary, the present invention includes at least one of the following beneficial technical effects:

[0071] 1. The present invention provides an integrated calibration method for a fiber optic compass and a magnetic compass, which combines the working characteristics of the fiber optic compass and the magnetic compass to make the fiber optic compass and the magnetic compass complement and calibrate each other, thereby increasing system reliability and improving system accuracy through data fusion. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 It is a flow chart of the integrated calibration method of the fiber optic compass and the magnetic compass.

[0073] Figure 2 It is a schematic diagram of magnetic compass error in the integrated calibration method of fiber optic compass and magnetic compass. DETAILED DESCRIPTION

[0074] In order to make the purpose, technical solution and advantages of the present invention more clear, the present invention is described below by means of specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention. Figure 1 The present invention is described in further detail.

[0075] The present invention discloses a method for integrating optical fiber compass and magnetic compass, referring to Figure 1 The output of the fiber optic compass can be used to compensate the measurement data of the magnetic compass. At the same time, the output of the magnetic compass can be used as an observation to constrain the heading output of the fiber optic compass.

[0076] The integrated calibration method of the optical fiber compass and the magnetic compass of the present invention specifically comprises the following steps:

[0077] S1, construct a magnetic compensation algorithm based on the influence of complex magnetic environment on the magnetic compass and the angle data actually output by the fiber optic compass.

[0078] A fiber optic gyrocompass (including an inertial measurement unit and a navigation computer circuit board) can receive information from a satellite navigation system (GNSS) or a Doppler odometer (DVL) and output information such as heading angle and rate of turn (ROT).

[0079] A magnetic sensor measurement module is added to the fiber optic compass. The magnetic sensor measurement axis is consistent with the sensitive axis of the fiber optic compass gyro and accelerometer, pointing to the right, front, and top axes of the fiber optic / magnetic integrated compass respectively. The magnetic field data actually measured by the magnetic sensor are M x 、M y 、M z .

[0080] Specifically, the steps of constructing the magnetic compensation algorithm are:

[0081] S11, calculating the true value of the local magnetic field according to the angle data actually output by the fiber optic compass and the projections of the local magnetic field in the east, north and sky directions.

[0082] That is, first, according to the angle data actually output by the fiber optic compass, the navigation coordinate system X is obtained. n Y n Z n To the carrier coordinate system X b Y b Z b The coordinate transformation matrix

[0083]

[0084] Among them, ψ is the heading angle actually output by the fiber optic compass, θ is the pitch angle actually output by the fiber optic compass, and γ is the roll angle actually output by the fiber optic compass;

[0085] Then, according to the coordinate transformation matrix The true value of the local magnetic field is calculated by the projection of the local magnetic field in the east, north and sky directions.

[0086] The calculation formula for the true value of the local magnetic field is:

[0087]

[0088] Among them, [M E M N M U ] T It is the projection of the local magnetic field in the east, north and sky directions.

[0089] S12, deriving a magnetic compensation calculation formula for compensating the magnetic field data measured by the magnetic compass using the angle data actually output by the fiber optic compass based on the actual value of the local magnetic field and the magnetic field data actually measured by the magnetic compass.

[0090] In the process of azimuth calculation, the magnetic compass needs to use a three-axis magnetic sensor to measure the local geomagnetic field vector information, but the magnetic compass will inevitably be affected by various ferromagnetic interferences, which will cause errors in the azimuth of the magnetic compass.

[0091] That is, considering the influence of complex magnetic environment on the magnetic compass, the magnetic field data actually output by the magnetic compass can be expressed as:

[0092]

[0093] Among them, [M x M y M z ] T is the projection of the magnetic field intensity actually output by the magnetic compass in the x, y, and z directions, [H x H y H z ] T is the true value of the local magnetic field, and B0 represent the effects of soft magnetic interference and hard magnetic interference on the magnetic field, respectively;

[0094] Formula (3) can be further expressed as:

[0095]

[0096] in,

[0097] The actual value of the local magnetic field (the value calculated by the above formula (2) [H x H y H z ] T ) and the magnetic field data actually measured by the magnetic compass ([M x M y M z ] T , where the magnetic field data actually measured by the magnetic compass is the value actually measured before the data correction by the method of the present invention, that is, the uncorrected measured value) is substituted into formula (4) to obtain the relationship between the ferromagnetic interference coefficients A and B;

[0098] The relationship between the ferromagnetic interference coefficients A and B is fitted by least squares, and the ferromagnetic interference coefficients A and B are calculated;

[0099] Substituting the ferromagnetic interference coefficients A and B into formula (4) yields a magnetic compensation calculation formula for compensating the magnetic field data actually measured by the magnetic compass using the angle output by the fiber optic compass.

[0100] S13, using the compensated magnetic field data output by the magnetic compass and the magnetic declination of the local magnetic field, a true north heading compensation calculation formula of the magnetic compass is calculated.

[0101] That is, firstly, the projection of the output of the magnetic compass in the x and y directions after compensation and Solve for the magnetic heading angle:

[0102]

[0103] in, is the projection of the output of the magnetic compass in the x and y directions after compensation;

[0104] Then, according to the magnetic heading angle And the magnetic declination of the local magnetic field, the true north heading compensation calculation formula of the magnetic compass is obtained:

[0105]

[0106] Among them, ψ M is the compensated true north heading output by the magnetic compass, ψ M0 It is the local magnetic declination. In addition to outputting heading and heading turning rate information, the fiber optic compass can also output longitude and latitude information. The local magnetic declination is obtained by looking up the table based on the longitude and latitude output by the fiber optic compass.

[0107] S2, when the fiber optic compass and magnetic compass integrated device enters the working state, determining the working calibration mode of the fiber optic compass and magnetic compass integrated device, wherein the working calibration mode includes a magnetic calibration mode and a fiber optic compass calibration mode.

[0108] When the integrated fiber optic compass and magnetic compass device enters the magnetic calibration mode, the information currently output by the fiber optic compass and the local magnetic field information of the current position of the ship are substituted into the magnetic compensation algorithm to calculate the compensated true north heading output by the magnetic compass.

[0109] Assuming that the angle data actually measured by the fiber optic compass at 00:01 Beijing time, the magnetic field data actually measured by the magnetic compass, and the local magnetic field data at the current location of the ship are used to obtain the magnetic compensation calculation formula according to the above steps S11 and S12 (of course, the magnetic compensation algorithm can also be calculated using the historical data actually measured by the fiber optic compass and the magnetic compass during the ship's historical voyage and the local magnetic field data at the corresponding measurement location). Then, assuming that the magnetic field data actually measured by the magnetic compass is corrected using the angle output by the fiber optic compass at 00:02 Beijing time, then it is only necessary to recalculate the local magnetic field true value at that moment based on the angle output by the fiber optic compass at 00:02 Beijing time, and then substitute the current local magnetic field true value and the ferromagnetic interference coefficients A and B into the magnetic compensation calculation formula to calculate the compensated magnetic field data output by the magnetic compass. Then the compensated magnetic field data output by the magnetic compass is Substituting into the formula of step S13, the compensated true north heading output by the magnetic compass can be calculated.

[0110] When the integrated fiber optic compass and magnetic compass device enters the fiber optic compass calibration mode, the measurement result of the fiber optic compass is corrected by using the compensated true north heading output by the magnetic compass through the Kalman filter algorithm.

[0111] The fiber optic compass is essentially a strapdown compass system that performs iterative calculations through the compass effect. Although the magnetic compass has large measurement noise, it has stable performance and is suitable for long-term operation. Combining the characteristics of the fiber optic compass and the magnetic compass, a Kalman filter is constructed, and the magnetic compass is used as the observation quantity to constrain the fiber optic compass.

[0112] Specifically, the specific steps of correcting the measurement result of the fiber optic compass using the compensated true north heading output by the magnetic compass through the Kalman filter algorithm are as follows:

[0113] The disturbance analysis of the measurement results of the fiber optic compass is carried out, and the high-order terms of the basic error are omitted. The linearized inertial navigation attitude, velocity, and position error equations are obtained as follows:

[0114]

[0115] In the formula, α, δv n ,δp n Represents three-dimensional attitude, velocity, and position error.

[0116] M pv With M pp The rest of the elements in are zero, L is the local latitude, R M , R Nare the meridian radius and the zodiac radius respectively, h is the ship's altitude, v E 、v N are the eastward and northward speeds of the ship, respectively;

[0117] The drift error of fiber optic compass and accelerometer can be modeled as:

[0118]

[0119] Constant zero bias ε b and It can be expressed as:

[0120]

[0121] First-order Gauss-Markov process ε r and It can be expressed as:

[0122]

[0123] The state vector of the filter is constructed based on the inertial navigation attitude, velocity, and position error equations after the linearization of the fiber optic compass and the drift errors of the fiber optic compass and accelerometer (that is, the INS navigation parameter error and the drift error of the inertial sensor are selected as the state vector of the filter):

[0124]

[0125] The system state equation of the inertial navigation system is expressed as:

[0126]

[0127] In the formula, the sub-matrix F 12 ~F 33 is the expanded form of formula (7), where 0 represents a 3×3 zero matrix.

[0128]

[0129] Where I is a 3×3 unit matrix, [w gx w gy w gz w ax w ay w az ] T is the fiber optic gyro compass and accelerometer white noise in the x, y, and z directions, [w rgx w rgy w rgz w rax w ray w raz ] Tis the first-order Gauss-Markov process noise of the fiber optic gyro compass and accelerometer in the x, y, and z directions.

[0130] Since the magnetic compass data as an observation also contains errors, considering the noise of the magnetic compass, the observation equation of the magnetic compass is:

[0131] Z(t)=H(t)x(t)+υ(t) (16)

[0132] H(t)=[0 1×2 10 1×18 ] 1×21 (17)

[0133] The observed quantity actually measured by the magnetic compass is:

[0134] Z(t)=ψ INS -ψ M (18)

[0135] Among them, ψ M is the compensated true north heading output by the magnetic compass, ψ INS It is the heading value output by the fiber optic compass.

[0136] According to formulas (7)-(18), a Kalman filter can be constructed. Based on the Kalman filter algorithm, the state variable x(t) is estimated in real time and the measurement results of the fiber optic compass are corrected in an open loop.

[0137] Figure 2 A schematic diagram of magnetic compass error of an integrated calibration method of a fiber optic compass and a magnetic compass of the present invention is given, and the X-axis and the Y-axis represent the outputs of the two axes of the magnetic compass carrier, the right direction and the forward direction, respectively. When there is no external magnetic interference and the XOY plane is parallel to the local horizontal plane, the magnetic compass rotates horizontally for one circle, and the outputs of the two horizontal magnetic field vectors of the X-axis and the Y-axis are circles with the center at the origin, as shown by the solid line A; soft magnetic interference causes the magnetic compass output to become an ellipse, and the major axis of the ellipse forms a certain angle with the coordinate axis, as shown by the dotted line B; hard magnetic interference causes the center of the magnetic compass output curve to shift, as shown by the dotted line C.

[0138] It should be clear that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Claims

1. A method for calibrating an integrated optical fiber compass and a magnetic compass, characterized in that: The specific steps include: S1, constructing a magnetic compensation algorithm based on the influence of complex magnetic environment on the magnetic compass and the angle data actually output by the fiber optic compass; S2, when the integrated fiber optic compass and magnetic compass device enters a working state, determining a working calibration mode of the integrated fiber optic compass and magnetic compass device, wherein the working calibration mode includes a magnetic calibration mode and a fiber optic compass calibration mode; When the integrated fiber optic compass and magnetic compass device enters the magnetic calibration mode, the information currently output by the fiber optic compass and the local magnetic field information of the current position of the ship are substituted into the magnetic compensation algorithm to calculate the compensated true north heading output by the magnetic compass; When the integrated fiber optic compass and magnetic compass device enters the fiber optic compass calibration mode, the measurement result of the fiber optic compass is corrected by using the compensated true north heading output by the magnetic compass through the Kalman filter algorithm.

2. The integrated calibration method of optical fiber compass and magnetic compass according to claim 1, characterized in that: The specific steps of constructing a magnetic compensation algorithm in step S1 according to the influence of the complex magnetic environment on the magnetic compass and the angle data actually output by the fiber optic compass are: The true value of the local magnetic field is calculated based on the angle data actually output by the fiber optic compass and the projection of the local magnetic field in the east, north and sky directions; According to the actual value of the local magnetic field and the magnetic field data actually measured by the magnetic compass, a magnetic compensation calculation formula is derived to compensate the magnetic field data measured by the magnetic compass using the angle data actually output by the optical fiber compass; The compensation calculation formula of the true north heading of the magnetic compass is calculated by using the compensated magnetic field data output by the magnetic compass and the magnetic declination of the local magnetic field.

3. The integrated calibration method of optical fiber compass and magnetic compass according to claim 2, characterized in that: The specific steps to calculate the true value of the local magnetic field based on the angle data actually output by the fiber optic compass and the projection of the local magnetic field in the east, north and sky directions are as follows: First, according to the angle data actually output by the fiber optic compass, the navigation coordinate system X is obtained. n Y n Z n To the carrier coordinate system X b Y b Z b The coordinate transformation matrix Then, according to the coordinate transformation matrix The true value of the local magnetic field is calculated by the projection of the local magnetic field in the east, north and sky directions.

4. The integrated calibration method of optical fiber compass and magnetic compass according to claim 3, characterized in that: The coordinate transformation matrix The calculation formula is: Among them, ψ is the heading angle actually output by the fiber optic compass, θ is the pitch angle actually output by the fiber optic compass, and γ is the roll angle actually output by the fiber optic compass; The calculation formula for the true value of the local magnetic field is: Among them, [M E M N M U ] T It is the projection of the local magnetic field in the east, north and sky directions.

5. The integrated calibration method of optical fiber compass and magnetic compass according to claim 2, characterized in that: The specific steps to derive the magnetic compensation calculation formula based on the actual value of the local magnetic field and the magnetic field data actually measured by the magnetic compass are: Considering the influence of complex magnetic environment on the magnetic compass, the magnetic field data actually output by the magnetic compass can be expressed as: Among them, [M x M y M z ] T is the projection of the magnetic field intensity actually output by the magnetic compass in the x, y, and z directions, [H x H y H z ] T is the true value of the local magnetic field, and B0 represent the effects of soft magnetic interference and hard magnetic interference on the magnetic field, respectively; Formula (3) can be further expressed as: in, Substituting the actual value of the local magnetic field and the magnetic field data actually measured by the magnetic compass into formula (4) we can obtain the relationship between the ferromagnetic interference coefficients A and B; The relationship between the ferromagnetic interference coefficients A and B is fitted by least squares, and the ferromagnetic interference coefficients A and B are calculated; Substituting the ferromagnetic interference coefficients A and B into formula (4) yields a magnetic compensation calculation formula for compensating the magnetic field data actually measured by the magnetic compass using the angle output by the fiber optic compass.

6. The integrated calibration method of optical fiber compass and magnetic compass according to claim 2, characterized in that: The specific steps of obtaining the true north heading compensation calculation formula of the magnetic compass using the compensated magnetic field data output by the magnetic compass and the magnetic declination of the local magnetic field are as follows: Projection of the magnetic compass output in the x and y directions after compensation and Calculate the magnetic heading angle; According to the magnetic heading angle and the magnetic declination of the local magnetic field, the true north heading compensation calculation formula of the magnetic compass is obtained.

7. The integrated calibration method of optical fiber compass and magnetic compass according to claim 6, characterized in that: The calculation formula of magnetic heading angle is: in, is the projection of the output of the magnetic compass in the x and y directions after compensation; The calculation formula for the true north heading compensation of the magnetic compass is: Among them, ψ M is the compensated true north heading output by the magnetic compass, ψ M0 is the local magnetic declination, which is obtained by looking up the table according to the longitude and latitude output by the fiber optic compass.

8. The integrated calibration method of optical fiber compass and magnetic compass according to claim 1, characterized in that: In step S2, the specific steps of correcting the measurement result of the fiber optic compass using the compensated true north heading output by the magnetic compass through the Kalman filter algorithm are as follows: Selecting the INS navigation parameter error and the drift error of the inertial sensor as the state vector of the filter, we can get Considering the noise of the magnetic compass, the observation equation of the magnetic compass is: Z(t)=H(t)x(t)+υ(t) (8) H(t)=[0 1×2 10 1×18 ] 1×21 (9) The observed quantity actually measured by the magnetic compass is: Z(t)=ψ INS -ψ M (10) Among them, ψ M is the compensated true north heading output by the magnetic compass, ψ INS It is the heading value output by the fiber optic compass; According to formulas (7)-(10), the state variable x(t) is estimated in real time based on the Kalman filter algorithm, and the measurement results of the fiber optic compass are corrected in an open loop.

9. The integrated calibration method of optical fiber compass and magnetic compass according to claim 8, characterized in that: The state vector construction process of the filter is: The disturbance analysis of the measurement results of the fiber optic compass is carried out, and the high-order terms of the basic error are omitted. The linearized inertial navigation attitude, velocity, and position error equations are obtained as follows: In the formula, α, δv n ,δp n Represents three-dimensional attitude, velocity, and position error, M pv With M pp The rest of the elements in are zero, L is the local latitude, R M , R N are the meridian radius and the zodiac radius respectively, h is the ship's altitude, v E 、v N are the eastward and northward speeds of the ship, respectively; The drift error of fiber optic compass and accelerometer can be modeled as: Constant zero bias ε b and It can be expressed as: First-order Gauss-Markov process ε r and It can be expressed as: The state vector of the filter is constructed based on the inertial navigation attitude, velocity, and position error equations after the linearization of the fiber optic compass and the drift errors of the fiber optic compass and accelerometer: The system state equation of the inertial navigation system is: In the formula, the sub-matrix F 12 ~F 33 is the expanded form of formula (11), where 0 represents a 3×3 zero matrix. Where I is a 3×3 unit matrix, [w gx w gy w gz w ax w ay w az ] T is the fiber optic gyro compass and accelerometer white noise in the x, y, and z directions, [w rgx w rgy w rgz w rax w ray w raz ] T is the first-order Gauss-Markov process noise of the fiber optic gyro compass and accelerometer in the x, y, and z directions.

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