MEMS inertial navigation self-calibration method based on double-shaft pod multi-position rotation

Abstract

The invention discloses an MEMS inertial navigation self-calibration method based on multi-position rotation of a double-shaft pod. The method comprises the following steps: (1) issuing a calibration instruction, satellite navigation information and a double-shaft frame angle to MEMS inertial navigation by the pod through a communication interface; (2) feeding back double-frame transposition to the pod in the MEMS inertial navigation self-calibration process, assisting the double-shaft pod to execute 8-position rotation in the calibration stage, and estimating instrument errors, mounting deviation angles and datum plane deviation angles by the MEMS inertial navigation in the rotation process; (3) after the 8-position rotation in the calibration stage is completed, the MEMS inertial navigation enters a calibration self-inspection state; (4) feeding back double-frame transposition to the pod in the MEMS inertial navigation calibration self-inspection process, assisting the pod in executing 5-position rotation in the detection stage, and detecting the correctness of calibration parameters in the rotation process; and (5) after MEMS inertial navigation calibration self-inspection is completed, feeding back a calibration state, and storing a calibration result. According to the invention, the problem of calibration error caused by incapability of providing a horizontal reference or an uneven reference surface due to environmental factors is solved.

Description

Technical Field

[0001] The invention relates to a MEMS inertial navigation self-calibration method based on dual-axis pod multi-position rotation, which is used in the field of inertial navigation. Background Art

[0002] MEMS inertial navigation is installed inside the airborne optoelectronic pod ( Figure 1 ), which is used for the attitude and heading information of sensitive pods and assists the aiming and positioning of airborne optoelectronic pods. To ensure the accuracy of the attitude and heading information fed back by the MEMS inertial navigation to the pod, it is necessary to correct the deviation angle between the MEMS inertial navigation system and the pod coordinate system. In addition, based on the long-term stability characteristics of MEMS instruments, the instruments need to be calibrated and maintained regularly to maintain accuracy.

[0003] In the past, the calibration of the installation deviation angle required a calibrated marble slab or turntable as a horizontal reference surface to ensure tracking of the ground. However, in actual engineering applications, the test conditions in the ideal laboratory environment mentioned above may not be available, resulting in the vertical axis of the pod not being perpendicular to the geoid. Under this condition, the installation deviation angle calibrated by the MEMS inertial navigation is inaccurate. Therefore, it is necessary to find a MEMS inertial navigation installation deviation angle calibration method that does not rely on an absolute zero reference to ensure calibration accuracy. Summary of the invention

[0004] The technical problem to be solved by the present invention is: to overcome the shortcomings of the prior art and provide a MEMS inertial navigation self-calibration method based on dual-axis pod multi-position rotation, which can calibrate the installation deviation angle of the MEMS inertial navigation inside the pod without relying on a horizontal reference plane while estimating and compensating instrument errors, thereby solving the problem of calibration errors caused by environmental factors that cannot provide a horizontal reference or an uneven reference plane.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A MEMS inertial navigation self-calibration method based on dual-axis pod multi-position rotation includes the following steps:

[0007] (1) The pod sends calibration instructions, satellite navigation information, and dual-axis frame angles to the MEMS inertial navigation system through the communication interface;

[0008] (2) During the self-calibration process, the MEMS inertial navigation system feeds back the dual-frame rotation to the pod, assisting the dual-axis pod in performing the 8-position rotation during the calibration phase. During the rotation, the MEMS inertial navigation system estimates the instrument error, installation deviation angle, and reference surface deviation angle.

[0009] (3) After completing the 8-position rotation in the calibration phase, the MEMS inertial navigation enters the calibration self-test state;

[0010] (4) During the MEMS inertial navigation calibration self-test, the dual-frame rotation is fed back to the pod to assist the pod in executing the 5-position rotation during the test phase. During the rotation, the correctness of the calibration parameters is tested;

[0011] (5) After the MEMS inertial navigation calibration self-check is completed, the calibration status is fed back and the calibration results are stored.

[0012] In one embodiment of the present invention, the communication interface adopts any one of RS232 serial port, RS422 serial port, RS485 serial port and CAN bus.

[0013] In one embodiment of the present invention, the satellite navigation information includes geographic system (northeast sky) speed and position information.

[0014] In one embodiment of the present invention, the dual-axis frame angle includes a pod pitch axis angle and an azimuth axis angle.

[0015] In one embodiment of the present invention, the MEMS inertial navigation is an inertial measurement unit that uses a three-axis micro-electromechanical gyroscope and a three-axis micro-electromechanical accelerometer as sensors, is installed inside the pod, and can rotate with the pod.

[0016] In one embodiment of the present invention, when the MEMS inertial navigation rotates with the pod, the pod azimuth axis corresponds to the MEMS inertial navigation heading axis, and the pod pitch axis corresponds to the MEMS inertial navigation roll axis.

[0017] In one embodiment of the present invention, the instrument error is the three-axis gyroscope zero drift, the three-axis accelerometer zero bias and the scale factor, the installation deviation angle is the deviation angle of the MEMS inertial navigation relative to the horizontal plane and the normal plane where the pod optical axis is located, and the reference plane deviation angle is the deviation angle of the pod optical axis relative to the geoid.

[0018] In one embodiment of the present invention, the position rotation sequence and the dual-axis frame angle of the calibration stage 8 in step (2) are detailed in Figure 2 Middle ①~⑧.

[0019] In one embodiment of the present invention, the rotation sequence of the position of the detection stage 5 and the angle of the dual-axis frame in step (4) are as follows: Figure 2 Middle 9~

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention realizes multi-position rotation of MEMS inertial navigation by means of the pitch and azimuth dual-axis frame angles of the pod. When calibrating the installation deviation angle between the MEMS inertial navigation and the reference surface, the error angle of the reference surface itself relative to the geoid is estimated through the attitude errors at different positions, and compensation is performed to ensure that the obtained MEMS inertial navigation installation deviation angle is a real deviation relative to the geoid, so that the horizontal reference surface is no longer relied on or calibrated during self-calibration of the MEMS inertial navigation. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 System diagram

[0023] Figure 2 This is the MEMS inertial navigation self-calibration flow chart.

[0024] Figure 3 FIG. 4 is an instrument error estimation curve of an embodiment.

[0025] Figure 4 The figure is a curve of gyro zero drift, accelerometer zero bias, and accelerometer scale factor estimated by MEMS inertial navigation during the rotation of the embodiment. DETAILED DESCRIPTION

[0026] 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.

[0027] A MEMS inertial navigation self-calibration method based on dual-axis pod multi-position rotation includes the following steps:

[0028] (1) The pod sends inertial navigation calibration instructions, satellite navigation information and dual-axis frame angles to the MEMS through the communication interface. The communication interface can be any one of RS232 serial port, RS422 serial port, RS485 serial port, and CAN bus. The satellite navigation information includes the speed and position information in the geographic system. The dual-axis frame angles include the pod azimuth frame angle and the pitch frame angle.

[0029] (2) During the self-calibration process, the MEMS inertial navigation system provides feedback on the dual-frame rotation to the pod, assisting the dual-axis pod in performing the eight-position rotation during the calibration phase. During the rotation, the MEMS inertial navigation system estimates the instrument error, installation deviation angle, and reference surface deviation angle.

[0030] The target rotation of the pod's dual-axis frame is fed back by the MEMS inertial navigation system. The initial zero position of the dual-axis frame is (azimuth 0°, pitch 0°). The order of the eight rotations in the calibration phase is: initial zero position -> (azimuth 90°, pitch 0°) -> (azimuth 90°, pitch -90°) -> (azimuth 0°, pitch -90°) -> (azimuth 0°, pitch 0°) -> (azimuth 180°, pitch 0°) -> (azimuth 0°, pitch 0°) -> (azimuth 0°, pitch 0°) -> (azimuth 0°, pitch -90°) -> (azimuth 0°, pitch 0°).

[0031] The MEMS inertial navigation instrument error is estimated by establishing a feedback correction Kalman filter model with 19-dimensional state quantities and 7-dimensional observation quantities. Among them, the state quantities include 3D attitude error, 3D velocity error, 3D position error, 3D gyro zero drift, 3D accelerometer zero bias, 3D accelerometer scale factor, and heading deviation angle. The observation quantities include velocity, position, and reference heading. The model is as follows:

[0032]

[0033] In the formula, n is the local geographic coordinate system, and b is the local system; is the pitch angle error estimate, is the roll angle error estimate, is the azimuth error estimate; is the eastward velocity error estimate, is the north velocity error estimate, is the celestial velocity error estimate; δL n is the latitude error estimate, δλ n is the longitude error estimate, δh n is the height error estimate; is the right gyro zero drift estimate, is the forward gyro zero drift estimate, It is the vertical gyro zero drift estimation; is the right accelerometer bias estimate, is the forward accelerometer bias estimate, is the vertical accelerometer bias estimate; is the right accelerometer scale factor estimate, is the forward accelerometer scale factor estimate, is the vertical accelerometer scale factor estimate; ψ n Install deviation estimate for reference heading.

[0034] The eastward speed, northward speed, celestial speed, latitude, longitude, altitude and reference heading are used as observation quantities, and the model is as follows:

[0035]

[0036] In the formula, Z k is the observed quantity, which can be decomposed into Z vk is the velocity observation, Z pk is the position observation, is the azimuth observation; v ins is the MEMS inertial navigation velocity, v gps is the satellite guidance speed, p ins is the MEMS inertial navigation position, p gps For the position of the guard guide, is the MEMS inertial navigation azimuth, is the reference azimuth angle, ψ is the estimated azimuth installation deviation angle; H is the observation matrix, which can be decomposed into H v is the velocity observation matrix, H p is the position observation matrix, is the azimuth observation matrix; X k is the system state variable; V k is the noise matrix.

[0037] The closed-loop Kalman filter equation is as follows:

[0038] 1) Equation of state:

[0039]

[0040] Where, X k is the system state variable, F k / k-1 is the one-step transfer matrix from time k-1 to time k, W k is the noise matrix; Z k is the observed quantity, H k is the observation matrix at time k, V k is the noise matrix.

[0041] 2) Filter equation

[0042]

[0043] In the formula, is the predicted value of the system state from time k-1 to time k, O is a zero matrix; F k is the system state matrix at time k, P k is the system state covariance matrix at time k, Q k is the system noise covariance matrix at time k, for The covariance matrix of is the gain matrix at time k, H k is the observation matrix at time k, P k / k-1 For X k / k-1 The covariance matrix, R k is the measurement noise covariance matrix at time k; is the obtained system state covariance matrix at time k, I is the unit matrix; To obtain the estimated value of the system state at time k, Z k is the observed quantity.

[0044] Installation deviation angle and reference surface deviation angle estimation process reference Figure 2 In steps ④ to ⑧, when the dual-axis frame angle is at the angle in step ④, calculate the installation deviation angle and When the dual-axis frame angle is at the angle in step ⑤, calculate the installation deviation angle and As shown below:

[0045]

[0046] Where, B is the base coordinate system; It is the horizontal attitude angle of the MEMS inertial navigation system converted from the b system to the B system in step ④; It is the horizontal attitude angle of the MEMS inertial navigation system converted from the b system to the B system in step ⑤; is the reference attitude angle (with 0° as the calculation reference); is the reference plane deviation angle.

[0047] When the dual-axis frame angle is at the angle in step ⑥, calculate As shown below:

[0048]

[0049] When the dual-axis frame angle is at the angle in step ⑦, calculate the vertical installation deviation angle As shown below:

[0050]

[0051] In the formula, It is the roll angle of the MEMS inertial navigation converted from the B system to the B system at the current position.

[0052] When the dual-axis frame angle is at the angle in step ⑧, calculate the horizontal installation deviation angle after compensating the reference surface deviation angle, as follows:

[0053]

[0054] Then according to the MEMS inertial navigation, the rotation matrix between the B system and the B system is converted Convert the installation deviation angle under the B system to the b system as follows:

[0055]

[0056] In the formula, θ b is the pitch installation deviation angle in the b system, γ b is the roll installation deviation angle of the b system, θ is the azimuth installation deviation angle of system b; B is the pitch installation deviation angle under the B system, γ B is the B-frame roll installation deviation angle, It is the deviation angle of the B system azimuth installation.

[0057] (3) After completing the 8-position rotation in the calibration phase, the MEMS inertial navigation enters the calibration self-test state. The gyro zero drift estimation can be obtained through step (2) Accelerometer bias estimation Accelerometer scale factor estimation Installation deviation angle θ after deviation from the reference surface b , γ b , The MEMS inertial navigation system performs realignment and compensates for the above error terms as shown in the following equation:

[0058]

[0059] In the formula, I is the unit matrix, (φ×) is the matrix of θ b , γ b , The antisymmetric matrix.

[0060] After instrument error compensation and installation deviation angle compensation, the inertial navigation attitude and azimuth are recalculated and the angle is tested, that is, the calibration self-test process is executed, see step (4).

[0061] (4) During the MEMS inertial navigation calibration self-test, the dual-frame rotation is fed back to the pod to assist the pod in executing the five-position rotation during the detection phase. During the rotation process, the correctness of the calibration parameters is tested.

[0062] The pod's dual-axis frame target rotation is fed back by the MEMS inertial navigation system. The order of the five rotations during the calibration self-test phase is: initial zero position -> (azimuth 180°, pitch 0°) -> (azimuth 0°, pitch 0°) -> (azimuth 0°, pitch -90°) -> (azimuth 0°, pitch 0°).

[0063] Calibration self-test process reference Figure 2 Step 9~ The residual error of the MEMS inertial navigation attitude angle at each position after deducting the reference plane deviation angle is calculated. The calibration is completed when the error does not exceed 0.1°, otherwise the calibration fails.

[0064] Example:

[0065] The present invention is described in detail below through specific examples.

[0066] The application of the method of the present invention is described by taking the data of a MEMS inertial navigation calibration process as an example. Before the test, the horizontal deflection angles of the reference surface measured by a level meter were approximately 0.26° and -0.08°.

[0067] (1) The pod sends calibration instructions, satellite navigation information, and dual-axis frame angles to the MEMS inertial navigation system through the communication interface.

[0068] (2) During the MEMS inertial navigation self-calibration process, the dual-frame rotation is fed back to the pod to assist the dual-axis pod in performing the 8-position rotation during the calibration phase (the dual-axis frame angle during the rotation process is as follows Figure 3 (a) During the rotation process, the MEMS inertial navigation system estimates the instrument error, installation deviation angle, and reference surface deviation angle.

[0069] The gyro zero drift, accelerometer zero bias, and accelerometer scale factor estimated by the MEMS inertial navigation during rotation are as follows: Figure 4 As shown, the estimated gyro zero drift is The accelerometer bias is The accelerometer scale factor is

[0070] Measured during the transfer process The calculated reference surface deviation angle is It is basically consistent with the reference surface deviation angle measured before the test, so the installation deviation angle for compensating the reference surface deviation angle is θ b =0.0064°,γ b =-0.0017°,

[0071] (3) After completing the 8-position rotation in the calibration phase, the MEMS inertial navigation enters the calibration self-test state.

[0072] (4) During the MEMS inertial navigation calibration self-test, the dual-frame rotation is fed back to the pod to assist the pod in executing the 5-position rotation during the detection phase (the dual-axis frame angle during the rotation is as follows: Figure 3 (b)) During the rotation process, the calibration parameters are checked for correctness. After the self-check process, the residual attitude deviation is obtained after realignment using the instrument information that compensates for the above errors: All are less than 0.1°, and the calibration is completed.

[0073] (5) After the MEMS inertial navigation calibration self-check is completed, the calibration status is fed back and the calibration results are stored.

[0074] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

[0075] 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 MEMS inertial navigation self-calibration method based on dual-axis pod multi-position rotation, characterized in that: include: (1) The pod sends calibration instructions, satellite navigation information, and dual-axis frame angles to the MEMS inertial navigation system through the communication interface; (2) During the self-calibration process, the MEMS inertial navigation system feeds back the dual-frame rotation to the pod, assisting the dual-axis pod in performing the 8-position rotation during the calibration phase. During the rotation, the MEMS inertial navigation system estimates the instrument error, installation deviation angle, and reference surface deviation angle. (3) After completing the 8-position rotation in the calibration phase, the MEMS inertial navigation enters the calibration self-test state; (4) During the MEMS inertial navigation calibration self-test, the dual-frame rotation is fed back to the pod to assist the pod in executing the 5-position rotation during the test phase. During the rotation, the correctness of the calibration parameters is tested; (5) After the MEMS inertial navigation calibration self-check is completed, the calibration status is fed back and the calibration results are stored.

2. The MEMS inertial navigation self-calibration method according to claim 1, characterized in that: The communication interface adopts any one of RS232 serial port, RS422 serial port, RS485 serial port and CAN bus.

3. The MEMS inertial navigation self-calibration method according to claim 1, characterized in that: The satellite navigation information includes geographic speed and position information.

4. The MEMS inertial navigation self-calibration method according to claim 1, characterized in that: The dual-axis frame angle includes a pod pitch axis angle and an azimuth axis angle.

5. The MEMS inertial navigation self-calibration method according to claim 1, characterized in that: MEMS inertial navigation is an inertial measurement unit that uses a three-axis micro-electromechanical gyroscope and a three-axis micro-electromechanical accelerometer as sensors, is installed inside the pod, and can rotate with the pod.

6. The MEMS inertial navigation self-calibration method according to claim 1, characterized in that: As the MEMS inertial navigation rotates with the pod, the pod azimuth axis corresponds to the MEMS inertial navigation heading axis, and the pod pitch axis corresponds to the MEMS inertial navigation roll axis.

7. The MEMS inertial navigation self-calibration method according to claim 1, characterized in that: The instrument error is the three-axis gyro zero drift, the three-axis accelerometer zero bias and the scale factor. The installation deviation angle is the deviation angle of the MEMS inertial navigation relative to the horizontal plane and the normal plane where the pod optical axis is located. The reference plane deviation angle is the deviation angle of the pod optical axis relative to the geoid.

8. The MEMS inertial navigation self-calibration method according to claim 1, characterized in that: The order of the 8 rotations in the calibration phase is: initial zero position -> (azimuth 90°, pitch 0°) -> (azimuth 90°, pitch -90°) -> (azimuth 0°, pitch -90°) -> (azimuth 0°, pitch 0°) -> (azimuth 180°, pitch 0°) -> (azimuth 0°, pitch 0°) -> (azimuth 0°, pitch -90°) -> (azimuth 0°, pitch 0°).

9. The MEMS inertial navigation self-calibration method according to claim 1, characterized in that: The order of the five rotations in the calibration self-test phase is: initial zero position -> (azimuth 180°, pitch 0°) -> (azimuth 0°, pitch 0°) -> (azimuth 0°, pitch -90°) -> (azimuth 0°, pitch 0°).

10. The MEMS inertial navigation self-calibration method according to claim 1, characterized in that: During the calibration self-check process, the calibration is completed when the residual error of the MEMS inertial navigation attitude angle at each position after deducting the reference surface deviation angle does not exceed 0.1°.

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