Attitude and heading calibration method of strapdown inertial navigation system based on multi-antenna GNSS (Global Navigation Satellite System)

Abstract

The invention relates to a multi-antenna GNSS (Global Navigation Satellite System)-based strapdown inertial navigation system navigation attitude calibration method, which comprises the following steps of: measuring the course and attitude of a ship body by using a three-antenna GNSS, taking the measured course and attitude as reference values of the course and attitude, correcting a strapdown inertial navigation system, and after multiple times of calibration, taking an installation error angle mean value for compensation. The method is low in calibration cost, simple in operation process and particularly suitable for navigation attitude calibration of the strapdown inertial navigation system of a small ship.

Description

Technical Field

[0001] The invention relates to the field of control technology, and in particular to a strapdown inertial navigation system heading calibration method based on a multi-antenna GNSS. Background Art

[0002] The inertial navigation system can use inertial sensitive devices to perform autonomous navigation calculations without relying on external auxiliary information. It has outstanding advantages such as being unaffected by geographical conditions, meteorological conditions and other external interference factors, and is widely used in various fields such as scientific research, exploration, and transportation. With the needs of national defense construction, small surface ship equipment, small unmanned boats, etc. are gradually beginning to be equipped with inertial navigation systems. Therefore, when installing the inertial navigation system, it should be calibrated for heading and attitude errors to eliminate installation errors and improve the measurement accuracy of the system.

[0003] There are differences between small surface ships and other surface ships, which leads to different inertial navigation calibration methods. First, the tonnage is relatively small, and the hull is more easily deformed than that of large ships; second, the state of small surface ships in the water is easily affected by environmental factors and changes. Therefore, choosing the correct calibration method is crucial to the successful completion of the calibration work and the control of calibration accuracy.

[0004] Usually, the calibration of the inertial navigation system of a surface ship is divided into azimuth calibration and horizontal calibration. Azimuth calibration is the process of making the azimuth zero position of the inertial navigation system consistent with the hull when the inertial navigation system is installed on the ship. Horizontal calibration is the process of making the horizontal zero position of the inertial navigation system consistent with the hull.

[0005] The azimuth calibration of the inertial navigation system of surface ships usually adopts the theodolite mutual aiming method and the north angle method. The principle of horizontal calibration is to use a horizontal measuring instrument to synchronously or differentially measure the horizontality of the reference platform and the horizontal reference plane of the inertial navigation system in the local horizontal plane to see whether they are consistent. Generally, necessary adjustments are required to make it meet the accuracy requirements of the inertial navigation system.

[0006] The above calibration methods have the following problems: long dock time, complicated calibration process, high requirements for operators, expensive equipment, and high requirements for the calibration environment. Therefore, there is an urgent need for a heading calibration method suitable for small ships, which can realize the installation calibration of the strapdown inertial navigation system at a low cost. Summary of the invention

[0007] The present invention provides a strapdown inertial navigation system heading and attitude calibration method based on multi-antenna GNSS, which uses three-antenna GNSS to measure the heading and attitude of the ship, and uses them as reference values ​​of the heading and attitude to calibrate the strapdown inertial navigation system. After multiple calibrations, the average value of the installation error angle is taken for compensation.

[0008] The present invention discloses a method for calibration of a strapdown inertial navigation system based on a multi-antenna GNSS, comprising the following steps:

[0009] S1: Select a calibration time and location with good conditions, as well as a GNSS receiver with centimeter-level directional accuracy and a receiving antenna with a directional base. The receiver should be able to output PPS pulses.

[0010] S2: Deploy three GNSS antennas, with antenna 1 as the main antenna. Antenna 1 and antenna 2 form a carrier coordinate system. Antenna 3 is placed in the hull plane and is not collinear with antenna 1 and antenna 2.

[0011] S3: Install the strapdown inertial navigation system inside the hull;

[0012] S4: Select static or dynamic calibration mode to record GNSS data and inertial navigation data;

[0013] S5: Process GNSS data to obtain the heading angle and pitch angle from antenna 1 and antenna 2; and obtain the roll angle from antenna 1 and antenna 3;

[0014] S6: Inertial navigation data processing: At the initial moment, the GNSS is connected and its position information is used for inertial navigation alignment. After alignment, it switches to pure inertial navigation state. The inertial navigation outputs real-time heading information. The output data is matched with GNSS data using PPS pulses per second.

[0015] S7: Select a data segment with relatively stable heading and attitude information for data processing to obtain the inertial navigation installation deviation angle.

[0016] Furthermore, in step S1, the conditions for selecting the calibration time and location include: calm water surface, open location, and ability to ensure GNSS signal quality.

[0017] Furthermore, the step S2 specifically includes:

[0018] Antenna 1 is taken as the main antenna, and the position of its phase center is the origin of the carrier system. The line connecting antenna 1 and antenna 2 is parallel to the longitudinal axis of the vehicle and points to the bow direction, forming the Y axis of the carrier system. The X axis is perpendicular to the Y axis in the hull plane, and the Z axis is perpendicular to the hull and points to the zenith direction, and forms a right-handed coordinate system with the X axis and Y axis. Antenna 3 is placed in the hull plane and is not collinear with antenna 1 and antenna 2.

[0019] Furthermore, the static or dynamic calibration method in step S4 specifically includes:

[0020] In static condition, the hull is in moored state;

[0021] In dynamic conditions, choose a calm water situation and move the boat at a speed of 3 to 5 knots.

[0022] Furthermore, the step S5 specifically includes:

[0023] At each observation epoch, the coordinates of the three antennas in the WGS-84 system are obtained through precise single-point positioning, and the antenna 1-2 baseline vector a in the WGS-84 system is obtained through dynamic baseline calculation. 12-e , and the antenna 1-3 baseline vector a 13-e ;

[0024] The two baseline vectors are transformed into the navigation coordinate system through the coordinate transformation matrix to obtain a 12-n and a 13-n ;

[0025] The baseline vector a under the load system is obtained by single-point positioning 12-b and a 13-b , and then we can get the transformation matrix from b system to n system

[0026] The heading angle and pitch angle are obtained from antenna 1 and antenna 2; the roll angle is obtained from antenna 1 and antenna 3.

[0027] Furthermore, the method further comprises the following steps:

[0028] S8: Repeat the above calibration process and take the average value of the installation deviation angle for compensation.

[0029] Compared with the prior art, the present invention has the following beneficial effects: (1) it is suitable for the heading calibration of small vessels; (2) it can realize the installation calibration of the strapdown inertial navigation system at a low cost; and (3) the calibration process is simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The above and other objects, features and advantages of the present disclosure will become more apparent through a more detailed description of exemplary embodiments of the present disclosure in conjunction with the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present disclosure.

[0031] Figure 1 is a flow chart of an exemplary embodiment according to the present disclosure;

[0032] Figure 2 Schematic diagram of an exemplary GNSS three-antenna installation. DETAILED DESCRIPTION

[0033] The preferred embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the preferred embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present disclosure more thorough and complete, and to fully convey the scope of the present disclosure to those skilled in the art.

[0034] The present disclosure provides a method for heading and attitude calibration of a strapdown inertial navigation system based on a multi-antenna GNSS. The process in an exemplary embodiment is as shown in the attached figure. Figure 1 As shown, it mainly includes the following steps:

[0035] Step 1: Choose a calibration time and location with good weather, which means: the water surface is relatively calm and the location is relatively open, which can ensure the quality of GNSS signal;

[0036] Step 2: Select a GNSS receiver with high directional accuracy and a receiving antenna with a directional base. The receiver should be able to output PPS pulses to facilitate time compensation during data post-processing. The GNSS receiver should preferably use RTK (Real-time kinematic) carrier phase differential technology and a centimeter-level positioning accuracy.

[0037] Step 3: Lay out three GNSS antennas: Take antenna 1 as the main antenna, and the position of its phase center is the origin of the carrier system. The line connecting antenna 1 and antenna 2 is parallel to the longitudinal axis of the vehicle and points to the bow direction, forming the Y axis of the carrier system. The X axis is perpendicular to the Y axis in the hull plane, and the Z axis is perpendicular to the hull and points to the zenith direction, and forms a right-handed coordinate system with the X axis and Y axis. Antenna 3 is placed in the hull plane and is not collinear with antenna 1 and antenna 2. The schematic diagram of the carrier coordinate system and the three antennas is shown in the attached figure. Figure 2 shown.

[0038] Step 4: Install the strapdown inertial navigation system in the hull;

[0039] Step 5: You can choose between static and dynamic calibration methods. In static conditions, the vessel is moored. In dynamic conditions, the vessel is moved at a speed of 3 to 5 knots when the water surface is relatively calm, while recording GNSS data and inertial navigation data.

[0040] Step 6: GNSS data processing: At each observation epoch, the coordinates of the three antennas in the WGS-84 system can be obtained through precise single-point positioning. The baseline vector a of antenna 1-2 in the WGS-84 system can be obtained through dynamic baseline calculation. 12-e , and the antenna 1-3 baseline vector a 13-e . The two baseline vectors are transformed into the navigation coordinate system through the coordinate transformation matrix to obtain a 12-n and a13-n The baseline vector a under the load system can be obtained by single-point positioning. 12-b and a 13-b , and then we can get the transformation matrix from b system to n system The heading angle and pitch angle can be obtained from antenna 1 and antenna 2; the roll angle can be obtained from antenna 1 and antenna 3.

[0041] Step 7: Inertial navigation data processing: The inertial navigation uses GNSS access at the initial moment and uses its position information for alignment. After alignment, the inertial navigation is switched to pure inertial navigation state, and the inertial navigation program is adjusted to output real-time heading information. The host computer is used to save the data and the data output frequency. The output data can be matched with the GNSS data using PPS pulse per second.

[0042] Step 8: Select the data segment with relatively stable heading and attitude information for data processing to obtain the inertial navigation installation deviation angle;

[0043] Step 9: Repeat the above calibration process several times and take the average of the installation error angle for compensation.

[0044] The above technical scheme is only an exemplary embodiment of the present invention. For those skilled in the art, it is easy to make various types of improvements or modifications based on the application methods and principles disclosed in the present invention, and it is not limited to the method described in the above specific embodiment of the present invention. Therefore, the method described above is only preferred and does not have a restrictive meaning.

Claims

1. A method for calibration of a strapdown inertial navigation system based on a multi-antenna GNSS, comprising the following steps: S1: Select a calibration time and location with good conditions, as well as a GNSS receiver with centimeter-level directional accuracy and a receiving antenna with a directional base. The receiver should be able to output PPS pulses. S2: Deploy three GNSS antennas, with antenna 1 as the main antenna. Antenna 1 and antenna 2 form a carrier coordinate system. Antenna 3 is placed in the hull plane and is not collinear with antenna 1 and antenna 2. S3: Install the strapdown inertial navigation system inside the hull; S4: Select static or dynamic calibration mode to record GNSS data and inertial navigation data; S5: Process GNSS data to obtain the heading angle and pitch angle from antenna 1 and antenna 2; and obtain the roll angle from antenna 1 and antenna 3; S6: Inertial navigation data processing: At the initial moment, the GNSS is connected and its position information is used for inertial navigation alignment. After alignment, it switches to pure inertial navigation state. The inertial navigation outputs real-time heading information. The output data is matched with GNSS data using PPS pulses per second. S7: Select a data segment with relatively stable heading and attitude information for data processing to obtain the inertial navigation installation deviation angle.

2. The method according to claim 1, characterized in that In step S1, the conditions for selecting the calibration time and location include: calm water surface, open location, and ability to ensure GNSS signal quality.

3. The method according to claim 1, characterized in that The step S2 specifically includes: Antenna 1 is taken as the main antenna, and the position of its phase center is the origin of the carrier system. The line connecting antenna 1 and antenna 2 is parallel to the longitudinal axis of the vehicle and points to the bow direction, forming the Y axis of the carrier system. The X axis is perpendicular to the Y axis in the hull plane, and the Z axis is perpendicular to the hull and points to the zenith direction, and forms a right-handed coordinate system with the X axis and Y axis. Antenna 3 is placed in the hull plane and is not collinear with antenna 1 and antenna 2.

4. The method according to claim 1, characterized in that The static or dynamic calibration method in step S4 specifically includes: In static condition, the hull is in moored state; In dynamic conditions, choose a calm water situation and move the boat at a speed of 3 to 5 knots.

5. The method according to claim 3, characterized in that: The step S5 specifically includes: At each observation epoch, the coordinates of the three antennas in the WGS-84 system are obtained through precise single-point positioning, and the antenna 1-2 baseline vector a in the WGS-84 system is obtained through dynamic baseline calculation. 12-e , and the antenna 1-3 baseline vector a 13-e ; The two baseline vectors are transformed into the navigation coordinate system through the coordinate transformation matrix to obtain a 12-n and a 13-n ; The baseline vector a under the load system is obtained by single-point positioning 12-b and a 13-b , and then we can get the transformation matrix from b system to n system The heading angle and pitch angle are obtained from antenna 1 and antenna 2; the roll angle is obtained from antenna 1 and antenna 3.

6. The method according to any one of claims 1 to 5, further comprising the following steps: S8: Repeat the above calibration process and take the average value of the installation deviation angle for compensation.

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