A general filtering method for pod master-slave inertial navigation transfer alignment and integrated navigation

Abstract

The present invention discloses a universal filtering method for pod master-sub inertial navigation transfer alignment and combined navigation, and relates to the technical field of airborne pods. The present invention adopts a speed plus position matching method for transfer alignment during the master-sub inertial navigation transfer alignment process. In the combined navigation state, in order to reduce the influence of the lever arm between the master-sub inertial navigation during the pod scanning and the turning of the carrier aircraft, the motion state of the sub-inertial navigation is judged by the angular velocity of the sub-inertial system, and the position or speed + position matching method is selected respectively, which can improve the rapidity of the filter convergence under the non-rotational working condition of the system, and overcome the influence of the lever arm under the rotational working condition. The present invention solves the problems of low transfer alignment accuracy and low combined navigation performance in the prior art.

Description

Technical Field

[0001] The invention relates to the technical field of airborne pods, and in particular to a universal filtering method for pod master-sub inertial navigation transmission alignment and integrated navigation. Background Art

[0002] In the military field, with the continuous development of technology and changes in combat requirements, pods will continue to play a key role in precision strikes, intelligence reconnaissance, target indication, etc., and can be widely used in land, sea, air and space. In order to keep the pod relatively stable during the movement of the carrier and improve the optoelectronic equipment to continuously and effectively track the target, a strapdown inertial navigation system (sub-inertial navigation system) is installed on the pod to accurately measure the attitude angle and heading angle of the pod, etc., to ensure that the optoelectronic equipment is stable and accurately points to the target. At the same time, combined with the high-precision inertial navigation (main inertial navigation) navigation information of the carrier, the pod inertial navigation system is assisted to perform combined navigation, improve the navigation accuracy of the pod, realize autonomous navigation of the pod to a certain extent, and reduce dependence on external navigation sources. Using the main inertial navigation system of the carrier to improve the high-precision rapid transmission alignment and effective combined navigation of the pod sub-inertial navigation system is a key technology to achieve relative stability of the pod. In order to effectively meet the alignment accuracy requirements and improve observability, the carrier is required to perform some kind of maneuvering movement during the transfer alignment process. The maneuvering method of the alignment process is strictly restricted by the carrier, and the accuracy is low compared to the main inertial navigation. In addition, the accumulated error is serious during long flight time. At the same time, the sub-inertial navigation is installed inside the pod, which is different from the installation position of the pod and the main inertial navigation in space, so there will inevitably be multi-bar arm errors. Summary of the invention

[0003] In view of the above-mentioned deficiencies in the prior art, the universal filtering method for pod master inertial navigation transfer alignment and integrated navigation provided by the present invention solves the problems of low transfer alignment accuracy and low integrated navigation performance in the prior art.

[0004] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is: a general filtering method for pod master-sub inertial navigation transfer alignment and integrated navigation, comprising the following steps:

[0005] S1: Power on the pod system. When the sub-INS receives the main INS information, it enters the transfer alignment state of speed + position matching.

[0006] S2: Determine whether the sub-INS transfer alignment time has arrived, if yes, proceed to step S5, otherwise proceed to step S3;

[0007] S3: Update the filter time of the sub-INS according to the filter time update cycle, and determine whether the update of the main INS information is valid based on the update cycle of the main INS. If yes, proceed to step S4, otherwise return to step S2;

[0008] S4: Calculate the observed value, and perform the measurement update of the filter based on the observed value, and return to step S2;

[0009] S5: When the alignment is completed, the sub-INS enters the navigation working state and performs pure inertial solution;

[0010] S6: Update the filter time according to the filter time update cycle, and determine whether the main inertial navigation information update is valid. If so, enter the main and sub-inertial navigation combined navigation working state, otherwise return to step S5;

[0011] S7: in the working state of the master inertial navigation integrated navigation, the current motion state of the pod is judged by using the three-axis angular rate, the adopted filtering mode is determined, and the filtering observation quantity under the filtering mode is calculated;

[0012] S8: performing filter measurement update based on the filter observation under the filtering mode;

[0013] S9: Determine whether the pod system is powered off, if not, return to step S5, if yes, complete the general filtering for the pod main and sub inertial navigation transfer alignment and integrated navigation.

[0014] The beneficial effect of the above scheme is as follows: the present invention provides a general filtering method for pod master-sub inertial navigation transfer alignment and integrated navigation, in which the speed plus position matching method is used for transfer alignment during the master-sub inertial navigation transfer alignment process, and in the integrated navigation state, in order to reduce the influence of the lever arm between the master-sub inertial navigation during the pod scanning and the turning of the carrier aircraft, the motion state of the sub-inertial navigation is judged by the angular velocity of the sub-inertial navigation system, and the position or speed+position matching method is selected respectively, and different observation quantity updates are performed for different matching methods, which can improve the rapidity of filter convergence under the non-rotational working condition of the system, and overcome the influence of the lever arm under the rotational working condition. The present invention solves the problems of low transfer alignment accuracy and low integrated navigation performance in the prior art.

[0015] Furthermore, the filter time update period formula is:

[0016]

[0017] in, for The predicted state at the moment, for The state transfer equation of the filter at time instant, for The optimal estimate of the state at time for The variance matrix of for The variance matrix of is the transpose of the matrix, is the noise driving matrix.

[0018] The beneficial effect of the above further solution is: through the above technical solution, the time update of the filter is achieved.

[0019] Furthermore, the observation quantity is calculated in S4 The formula is:

[0020]

[0021]

[0022]

[0023]

[0024] in, is the measurement equation of velocity and position, for The state variables at the moment, for The noise vector is measured at time, is the steady-state transfer matrix of the system, for The state variables at the moment, Assign the matrix to the system noise, is the system noise vector, is a 3×3 zero matrix, is a 3×3 unit matrix, is a 3×6 zero matrix, Sub-INS Tie to The attitude transformation matrix of the system, for Relative to The antisymmetric matrix of the angular velocity of the system, is a 3×3 matrix, is the local latitude, is the radius of curvature of the Earth's meridian plane, is the radius of curvature of the Earth's angular surface.

[0025] The beneficial effect of the above further solution is: through the above technical solution, the observed quantity is updated according to the measurement equation of speed and position, which is used for subsequent filtering measurement update.

[0026] Furthermore, in S4, the filter is updated based on the observed value, and the formula is:

[0027]

[0028]

[0029]

[0030] in, Based on speed and position The optimal estimate of the state at time is the filter gain matrix, is the measurement noise variance matrix, for of The optimal estimated variance matrix at the moment, is the identity matrix.

[0031] The beneficial effect of the above further solution is that: through the above technical solution, the filter measurement update is performed according to the speed + position observation quantity, which is conducive to achieving rapid alignment during the master inertial navigation transfer alignment process.

[0032] Furthermore, in S7, the three-axis angular rate is used to determine the current motion state of the pod and determine the filtering method to be used, specifically including the following situations:

[0033] (1) When the three-axis angular rate Less than or equal to the set value When , the pod is in a low-speed motion state, and the speed + position measurement is updated;

[0034] (2) When the three-axis angular rate Greater than the set value When the pod is in high-speed motion, the position measurement is updated.

[0035] The beneficial effect of the above further scheme is: the three-axis angular rate is used to determine the current motion state of the pod, so as to select a suitable filtering method. Through the above technical scheme, the influence of the lever arm between the main and sub-inertial navigation systems during the pod scanning and the turning of the carrier aircraft can be reduced, and the rapidity of the filter convergence under the non-rotating condition of the system can be improved, while overcoming the influence of the lever arm under the rotating condition.

[0036] Furthermore, the three-axis angular rate The calculation formula is:

[0037]

[0038] in, , and are the angular velocities on different coordinate axes respectively.

[0039] Furthermore, when the speed+position measurement update is performed, the filtered observation is the observation .

[0040] Furthermore, when the position measurement update is performed, the filtered observation is the observation , the formula is:

[0041]

[0042]

[0043] in, is the position measurement equation.

[0044] Furthermore, in S8, based on the filtered observations in the filtering mode, the filter measurement update is performed, including the following situations:

[0045] (1) When the velocity + position measurement update is performed, the filtered observation is the observation ,based on Realize the measurement update of the filter;

[0046] (2) When the position measurement is updated, the filtered observation is the observation ,based on Implements measurement update of the filter.

[0047] The beneficial effect of the above further solution is that: through the above technical solution, different filter measurement updates are performed based on different matching methods, which can improve the performance of the pod system in the integrated navigation state. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 The present invention is a flow chart of a general filtering method for pod master-slave inertial navigation transfer alignment and integrated navigation.

[0049] Figure 2 This is the schematic diagram of the main inertial navigation installation. DETAILED DESCRIPTION

[0050] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0051] like Figure 1 As shown, a general filtering method for pod master-slave inertial navigation transfer alignment and integrated navigation includes the following steps:

[0052] S1: Power on the pod system. When the sub-INS receives the main INS information, it enters the transfer alignment state of speed + position matching.

[0053] S2: Determine whether the sub-INS transfer alignment time has arrived, if yes, proceed to step S5, otherwise proceed to step S3;

[0054] S3: Update the filter time of the sub-INS according to the filter time update cycle, and determine whether the update of the main INS information is valid based on the update cycle of the main INS. If yes, proceed to step S4, otherwise return to step S2;

[0055] S4: Calculate the observed value, and perform the measurement update of the filter based on the observed value, and return to step S2;

[0056] S5: When the alignment is completed, the sub-INS enters the navigation working state and performs pure inertial solution;

[0057] S6: Update the filter time according to the filter time update cycle, and determine whether the main inertial navigation information update is valid. If so, enter the main and sub-inertial navigation combined navigation working state, otherwise return to step S5;

[0058] S7: in the working state of the master inertial navigation integrated navigation, the current motion state of the pod is judged by using the three-axis angular rate, the adopted filtering mode is determined, and the filtering observation quantity under the filtering mode is calculated;

[0059] S8: performing filter measurement update based on the filter observation under the filtering mode;

[0060] S9: Determine whether the pod system is powered off, if not, return to step S5, if yes, complete the general filtering for the pod main and sub inertial navigation transfer alignment and integrated navigation.

[0061] In one embodiment of the present invention, the pod on the carrier aircraft is generally installed under the belly of the aircraft, and is not installed in the same position as the main inertial navigation system. The relative distance between the main and sub-inertial navigation systems is called the lever arm vector. The carrier will produce a centrifugal effect when turning during the transmission alignment and combined navigation process. Due to the lever arm effect, the main and sub-inertial navigation systems have different speeds. At the same time, constrained by the optical factors of the pod, the sub-inertial navigation system cannot be installed at the geometric center of the pod frame axis. In addition, during the scanning process of the pod frame axis during operation, the sub-inertial navigation system has a dynamic lever arm error relative to the main inertial navigation system. Therefore, the lever arm length cannot be accurately measured and compensated. In this solution, the lever arm is included in the state equation when designing the filter, and the error caused by the lever arm effect is compensated and calculated in the measurement equation.

[0062] Different matching methods have different effects on the accuracy and convergence speed of transfer alignment. By analyzing the application conditions of the pod, the maneuverability of the master-slave inertial navigation transfer alignment process is limited. Position matching can overcome the influence of the lever arm effect better than speed matching. However, the position matching filter requires a longer alignment time, which is not conducive to rapid alignment. Therefore, this scheme uses speed + position matching to transfer alignment. In the combined navigation state, in order to reduce the influence of the lever arm between the master and slave inertial navigation during the pod scanning and aircraft turning process, the motion state of the slave inertial navigation is judged by the angular velocity of the slave inertial navigation system, and position or speed + position are used as the measurement to improve the rapidity of filter convergence under non-rotating conditions of the system, while overcoming the influence of the lever arm under rotating conditions.

[0063] Assume the main inertial navigation installation position and the load system ( system) origin Coincident, the accelerometer of the main inertial navigation is installed at a fixed point in the carrier coordinate system, is the origin position vector of the carrier coordinate system, is the position vector of the sub-INS relative to the inertial coordinate origin, is the position vector of the sub-inertia relative to the origin of the carrier coordinate system. The vector relationship between the three vectors is as follows: Figure 2 shown.

[0064] , and The relationship between the three is:

[0065]

[0066] Differentiating the above, The position vector of the origin of the carrier coordinate system is fixed and unchanged, and according to the Coriolis theorem:

[0067]

[0068] in, is the speed of the INS relative to the Earth coordinate system, is the velocity of the main inertial navigation relative to the earth coordinate system, Main Inertial Navigation Relative to The rotational angular velocity of the system;

[0069] Navigation coordinates If the system is projected, then:

[0070]

[0071]

[0072] in, is the velocity of the main inertial navigation in the navigation coordinate system, is the speed of the sub-INS in the navigation coordinate system, For The relative lever arm between the master and slave inertial navigation system is set. for Relative to The angular velocity of the system is The projection of the system, that is, the gyro measurement value ; for Relative The angular velocity of the system is The projection of the system, that is, the component of the Earth's rotation angular rate in the navigation system, where , is the Earth's rotation angular velocity, is the local latitude; for Relative The angular velocity of the system is The projection on the system, that is , , The east and north speeds of the carrier, is the radius of curvature of the Earth's meridian plane, is the radius of curvature of the Earth's angular surface.

[0073] Then the lever arm velocity error of the master inertial navigation is for:

[0074]

[0075]

[0076] in, , , They are The length of the arms in the east, north and sky directions.

[0077] Position error between master and slave inertial navigation caused by lever arm for:

[0078]

[0079] To account for the error introduced by the lever arm, the lever arm is included in the filter state. Select the state variable It is 18-dimensional, as shown below, including the sub-inertial misalignment angle , Inertia velocity error , Sub-INS position error , Inertial Guidance Gyro Bias 、Zero bias , dynamic lever arm .

[0080]

[0081] According to the attitude, velocity and position error equations of the strapdown inertial navigation, the discrete state space model of the master-slave inertial navigation integrated navigation is established with velocity and position errors as observation quantities as follows:

[0082]

[0083] When combining speed and position, it is necessary to compensate the speed and position of the output of the main and sub-INS for the lever arm before using them as observations. The speed + position measurement equation considering the lever arm error and the position measurement equation are:

[0084]

[0085]

[0086] The time is updated according to the update frequency of the sub-INS system, and the measurement is updated according to the frequency of the information transmitted from the main INS to the sub-INS, as follows.

[0087] The filter time update cycle formula is:

[0088]

[0089] in, for The predicted state at the moment, for The state transfer equation of the filter at time instant, for The optimal estimate of the state at time for The variance matrix of for The variance matrix of is the transpose of the matrix, is the noise driving matrix.

[0090] Calculation of observations in S4 The formula is:

[0091]

[0092]

[0093]

[0094]

[0095] in, is the measurement equation of velocity and position, for The state variables at the moment, for The noise vector is measured at time, is the steady-state transfer matrix of the system, for The state variables at the moment, Assign the matrix to the system noise, is the system noise vector, is a 3×3 zero matrix, is a 3×3 unit matrix, is a 3×6 zero matrix, Sub-INS Tie to The attitude transformation matrix of the system, for Relative to The antisymmetric matrix of the angular velocity of the system, is a 3×3 matrix, is the local latitude, is the radius of curvature of the Earth's meridian plane, is the radius of curvature of the Earth's angular surface.

[0096] In S4, the filter is updated based on the observed value, and the formula is:

[0097]

[0098]

[0099]

[0100] in, Based on speed and position The optimal estimate of the state at time is the filter gain matrix, is the measurement noise variance matrix, for of The optimal estimated variance matrix at the moment, is the identity matrix.

[0101] In order to quickly converge the filter and reduce the influence of the boom arm during the integrated navigation process, the To judge the motion state of the pod, speed + position are used as the observation quantity in the low-speed motion state, and only position is used as the observation quantity in the high-speed mode.

[0102] In S7, the three-axis angular rate is used to determine the current motion state of the pod and determine the filtering method to be used, including the following situations:

[0103] (1) When the three-axis angular rate Less than or equal to the set value When , the pod is in a low-speed motion state, and the speed + position measurement is updated;

[0104] (2) When the three-axis angular rate Greater than the set value When the pod is in high-speed motion, the position measurement is updated.

[0105] In general <2~3° / s is low rate mode, otherwise it is high speed mode, depending on the working conditions and system accuracy requirements.

[0106] Three-axis angular rate The calculation formula is:

[0107]

[0108] in, , and are the angular velocities on different coordinate axes respectively.

[0109] When the velocity + position measurement update is performed, the filtered observation is the observation .

[0110] When the position measurement update is performed, the filtered observation is the observation , the formula is:

[0111]

[0112]

[0113] in, is the position measurement equation.

[0114] In S8, based on the filtered observations in the filtering mode, the filter measurement update is performed, including the following situations:

[0115] (1) When the velocity + position measurement update is performed, the filtered observation is the observation ,based on Realize the measurement update of the filter;

[0116] (2) When the position measurement is updated, the filtered observation is the observation ,based on Implements measurement update of the filter.

[0117] The present invention proposes a universal filtering method for the transfer alignment and combined navigation of the main and sub-inertial navigation systems of a pod, which can complete the transfer alignment under maneuverability-restricted conditions, and at the same time improve the accuracy of the combined navigation of the main and sub-inertial navigation systems during the flight process of the carrier aircraft and the swaying state of the pod, simplify the filtering algorithm, and is suitable for the transfer alignment and combined navigation of the main and sub-inertial navigation systems of the pod, and can also be applied to the combined navigation of the sub-inertial navigation system and GNSS to improve the heading accuracy during turns.

[0118] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific variations and combinations that do not deviate from the essence of the present invention based on the technical revelations disclosed by the present invention, and these variations and combinations are still within the protection scope of the invention.

Claims

1. A general filtering method for pod master-slave inertial navigation transfer alignment and integrated navigation, characterized in that: The following steps are involved: S1: Power on the pod system. When the sub-INS receives the main INS information, it enters the transfer alignment state of speed + position matching. S2: Determine whether the sub-INS transfer alignment time has arrived, if yes, proceed to step S5, otherwise proceed to step S3; S3: Update the filter time of the sub-INS according to the filter time update cycle, and determine whether the update of the main INS information is valid based on the update cycle of the main INS. If yes, proceed to step S4, otherwise return to step S2; S4: Calculate the observed value, and perform the measurement update of the filter based on the observed value, and return to step S2; S5: When the alignment is completed, the sub-INS enters the navigation working state and performs pure inertial solution; S6: Update the filter time according to the filter time update cycle, and determine whether the main inertial navigation information update is valid. If so, enter the main and sub-inertial navigation combined navigation working state, otherwise return to step S5; S7: in the working state of the master inertial navigation integrated navigation, the current motion state of the pod is judged by using the three-axis angular rate, the adopted filtering mode is determined, and the filtering observation quantity under the filtering mode is calculated; S8: performing filter measurement update based on the filter observation under the filtering mode; S9: Determine whether the pod system is powered off, if not, return to step S5, if yes, complete the general filtering for the pod main and sub inertial navigation transfer alignment and integrated navigation.

2. The universal filtering method for pod master-slave inertial navigation transfer alignment and integrated navigation according to claim 1, characterized in that: The filter time update period formula is: in, for The predicted state at the moment, for The filter state transfer equation at time instant, for The optimal estimate of the state at time for The variance matrix of for The variance matrix of is the transpose of the matrix, is the noise driving matrix.

3. The universal filtering method for pod master-slave inertial navigation transfer alignment and integrated navigation according to claim 2 is characterized in that: The observation quantity is calculated in S4 The formula is: in, is the measurement equation of velocity and position, for The state variables at the moment, for The noise vector is measured at time, is the steady-state transfer matrix of the system, for The state variables at the moment, Assign the matrix to the system noise, is the system noise vector, is a 3×3 zero matrix, is a 3×3 unit matrix, is a 3×6 zero matrix, Sub-INS Tie to The attitude transformation matrix of the system, for Relative to The antisymmetric matrix of the angular velocity of the system, is a 3×3 matrix, is the local latitude, is the radius of curvature of the Earth's meridian plane, is the radius of curvature of the Earth's angular surface.

4. The universal filtering method for pod master-slave inertial navigation transfer alignment and integrated navigation according to claim 3 is characterized in that: In S4, the filter is updated based on the observed value, and the formula is: in, Based on speed and position The optimal estimate of the state at time is the filter gain matrix, is the measurement noise variance matrix, for of The optimal estimated variance matrix at the moment, is the identity matrix.

5. The universal filtering method for pod master-slave inertial navigation transfer alignment and integrated navigation according to claim 4, characterized in that: In S7, the three-axis angular rate is used to judge the current motion state of the pod and determine the filtering method to be used, which specifically includes the following situations: (1) When the three-axis angular rate Less than or equal to the set value When , the pod is in a low-speed motion state, and the speed + position measurement is updated; (2) When the three-axis angular rate Greater than the set value When the pod is in high-speed motion, the position measurement is updated.

6. The universal filtering method for pod master-slave inertial navigation transfer alignment and integrated navigation according to claim 5, characterized in that: The three-axis angular rate The calculation formula is: in, , and are the angular velocities on different coordinate axes respectively.

7. The universal filtering method for pod master-slave inertial navigation transfer alignment and integrated navigation according to claim 5, characterized in that: When the velocity + position measurement update is performed, the filtered observation is the observation .

8. The universal filtering method for pod master-slave inertial navigation transfer alignment and integrated navigation according to claim 7, characterized in that: When the position measurement update is performed, the filtered observation is the observation , the formula is: in, is the position measurement equation.

9. The universal filtering method for pod master-slave inertial navigation transfer alignment and integrated navigation according to claim 8, characterized in that: In S8, based on the filtered observation quantity in the filtering mode, the filter measurement update is performed, including the following situations: (1) When the velocity + position measurement update is performed, the filtered observation is the observation ,based on Realize the measurement update of the filter; (2) When the position measurement is updated, the filtered observation is the observation ,based on Implements measurement update of the filter.

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