Ultra-short baseline installation error calibration system and calibration method based on rotating platform

Abstract

The invention discloses an ultra-short baseline installation error calibration system and calibration method based on a rotating platform. The system comprises the rotating platform used for fixing an SINS / USBL integrated system on a mother ship; the ROV is used for carrying the fixed transponder to a designated position in water; the rotating platform drives the SINS / USBL integrated system to rotate, the USBL continuously measures the transponder in the rotating process, and the installation error angle of the USBL relative to the SINS is obtained through calculation. According to the scheme, operation is easy and convenient, a mother ship does not need to sail, and the installation error angle of the USBL can be conveniently calibrated through fixing; and a plurality of SINS and USBL integrated systems can be calibrated at the same time, so that the calibration efficiency is greatly improved.

Description

Technical Field

[0001] The present invention relates to the field of navigation technology, and in particular to an ultra-short baseline installation error calibration system and method. Background Art

[0002] Ultra-Short Baseline (USBL) system is increasingly widely used in underwater navigation and positioning due to its advantages such as small size and strong flexibility.

[0003] For the integrated design system of Strapdown Inertial Navigation System (SINS) and USBL, the USBL installation error calibration mainly refers to the calibration of the USBL deviation angle relative to SINS.

[0004] If the strapdown inertial navigation system (SINS) and USBL are not integrated designs, they need to be recalibrated after each disassembly and assembly, which is not only time-consuming and labor-intensive, but also requires the cooperation of the manufacturer, greatly reducing the efficiency of use.

[0005] The existing USBL installation error is calibrated on the lake, which requires the carrier to execute a series of complex navigation trajectories. However, due to environmental reasons, the carrier cannot ideally navigate along the predetermined trajectory on the lake. At the same time, the USBL is easily disturbed by the underwater environment when the carrier is navigating, such as interference from propellers, impact of water flow, noise generated by aquatic organisms, etc. These factors will further affect the positioning accuracy.

[0006] Before calibrating the installation angle, the location information of the transponder is required. When placing the transponder using the traditional calibration method, a float is used to keep the transponder facing upward. Although there is a cement block underneath, the float is affected by the complex underwater environment, resulting in a certain deviation in the position and direction of the transponder. Summary of the invention

[0007] In view of these problems existing in traditional calibration methods, the present invention provides a USBL installation error calibration solution based on a rotating device and an underwater robot, which can simply and efficiently complete the USBL installation error calibration and improve the underwater positioning accuracy.

[0008] In the calibration solution provided by the present invention, USBL and SINS are installed on the mother ship in an integrated manner through a rotating platform, and the transponder is installed on an underwater robot, namely an unmanned remotely operated vehicle (ROV). Through the cooperation of the two, the mother ship can complete the calibration of the deviation angle of USBL relative to SINS without sailing.

[0009] Further: The ROV is equipped with SINS, DVL (Doppler Velocity Logger), GNSS (Global Navigation Satellite System Antenna) and depth gauge to form a navigation system. The transponder is fixed on the top of the ROV. The integrated SINS / USBL system consists of SINS and USBL fixed up and down, fastened and sealed in a housing, and then the integrated system is fixed to the table axis, and the table can rotate 360 ​​degrees. If multiple integrated SINS / USBL systems need to be calibrated at the same time, multiple tables are set up, each corresponding to an integrated SINS / USBL system, and fixed on one side of the mother ship in turn, facing the position of the transponder.

[0010] The present invention utilizes a small ROV to carry a transponder, utilizes a method of combining SINS and DVL, dives into a predetermined position, and carries a cable, can work for a long time, and can control the position and posture of the ROV, ensure that the transponder maintains a fixed position and posture, and reduce the influence of water flow on the position of the transponder.

[0011] The specific calibration method includes the following steps: Transponder location determination; The SINS / USBL integrated system is fixed to the corresponding rotating platform table, fixed on the side of the mother ship facing the transponder; Using the pulse-per-second source of the first GNSS system on the mother ship, a precise pulse signal is generated every second; using a cable to connect the pulse-per-second output port of the first GNSS system on the mother ship with the pulse-per-second input ports of the SINS and USBL on the mother ship; The rotating platform table rotates a certain angle at a set rotation speed at regular intervals for a total of 360 degrees. During this process, the SINS / USBL integrated system's attitude, position, slant range and azimuth, and the transponder's absolute geographic location and depth information are collected in real time; The installation error angle of USBL relative to SINS in the SINS / USBL integrated system to be calibrated is calculated using the position of each measuring point obtained by the first GNSS system, the attitude data provided by the SINS on the mother ship, and the slant range data and azimuth provided by the USBL system.

[0012] Compared with the prior art, the advantages of the present invention are: (1) the installation error angle of USBL can be calibrated efficiently and accurately; (2) the operation is simple, the mother ship does not need to sail, it can be fixed, and no complicated calibration route is required; (3) multiple SINS and USBL integrated systems can be calibrated at the same time, saving calibration time; (4) the SINS / USBL integrated system only needs to be calibrated once before leaving the factory, and no recalibration is required afterwards, which is convenient for customers to use; (5) the transponder is carried by a small ROV, which can work for a long time and reduce the influence of water flow on the position of the transponder. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] 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.

[0014] Figure 1 is a flow chart of an exemplary embodiment according to the present disclosure; Figure 2 Schematic diagram of the rotating platform equipped with the SINS / USBL integrated system. DETAILED DESCRIPTION

[0015] 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.

[0016] The present invention provides a USBL installation error calibration system and method using a rotating platform and an underwater robot, so as to calibrate the installation deviation angle of the USBL relative to the SINS in an integrated SINS / USBL system.

[0017] In one exemplary embodiment, the system includes: (1) Rotating platform The integrated SINS / USBL system consists of SINS and USBL fixed up and down, tightly installed and sealed in a housing, and then the integrated system is fixed to the table axis, and the table can rotate 360 ​​degrees.

[0018] As attached Figure 2As shown, the table is used to install the integrated system of SINS / USBL, and the table is fixedly connected to the shaft. The table body is the entire single-axis turntable base, and the motor, encoder, bearing and conductive slip ring are installed between the table body and the shaft. The motor is used to drive the turntable to rotate, the encoder is used to measure the angle of rotation of the shaft, the bearing is used to carry the shaft, and the conductive slip ring is used to transmit various electrical signals between the turntable and the table body. The table body is fixedly connected to the mother ship. Ensure that the integrated system of SINS / USBL is in a horizontal state to avoid the situation where the transponder signal cannot be received when the table rotates.

[0019] If multiple integrated SINS / USBL systems need to be calibrated simultaneously, multiple tables are set up, each corresponding to the multiple integrated SINS / USBL systems, and fixed in sequence on one side of the mother ship, facing the position of the transponder.

[0020] In addition, a first GNSS system is installed on the mother ship to obtain the position of the mother ship.

[0021] (2) Transponder carrier In this embodiment, a small ROV is used to carry the transponder, and a combination of SINS and DVL is used to dive into a predetermined position and carry a cable. It can work for a long time and control the position and posture of the ROV to ensure that the transponder maintains a fixed position and posture, reducing the impact of water flow on the position of the transponder.

[0022] The ROV is equipped with a second SINS (to distinguish it from the SINS on the mother ship), a DVL, a second GNSS antenna and a depth gauge to form a navigation system, and a transponder is fixed on the top of the ROV.

[0023] Based on the above system, the calibration method includes the following steps: Step 1: Determine the position of the transponder: Use a small ROV to install the second SINS, DVL, second GNSS antenna, and depth gauge on the ROV to form a navigation system, and fix the transponder on the top of the ROV. First calibrate the parameters of the second SINS and DVL. After the surface alignment is completed, after diving, the effective bottoming depth of the DVL basically exceeds the depth of the lake. The DVL is basically effective for the bottom throughout the whole process. Enter the second SINS and DVL combination state, carry the power cable to the predetermined position, hover or bottom, and determine the absolute position of the transponder according to the second SINS and DVL combination, and it can work for a long time.

[0024] Step 2: Fix multiple SINS / USBL integrated systems to each corresponding table, and then fix them to one side of the mother ship, which faces the transponder. Use GNSS position information with RTK fixed solution positioning accuracy and SINS to provide heading, thereby providing a more accurate attitude matrix and position for the USBL calibration method.

[0025] Step 3: Utilize the pulse-per-second source of the first GNSS and generate a precise pulse signal every second.

[0026] Use a cable to connect the pulse-per-second output port of the first GNSS system to the pulse-per-second input port of the first inertial navigation system and USBL. Ensure that the system can correctly identify and process the pulse-per-second signal from the first GNSS system. Before performing pulse-per-second synchronization, the time of the first inertial navigation system, USBL and the first GNSS system needs to be calibrated to ensure that the time difference between the three is within an acceptable range.

[0027] Step 4: The rotating platform table then turns and stops at a certain time interval and rotates 360 degrees. During this process, the SINS / USBL integrated system controlled by the synchronous pulse trigger of the main control computer system works in sequence at a certain time, and collects the navigation attitude, position, slant range and azimuth of multiple SINS / USBL integrated systems, and the absolute geographical location and depth information of the transponders in real time.

[0028] Step 5: The first GNSS position of each measuring point on the track, the attitude data provided by the first SINS, and the slant range data and azimuth provided by the ultra-short baseline system are recorded.

[0029] The slant distance between the ultra-short baseline array and the transponder can be expressed as the Euclidean distance between their coordinates. The specific formula is as follows:

[0030] In the formula is the coordinate of the ultra-short baseline array in the earth coordinate system, is the coordinate of the transponder in the earth coordinate system.

[0031] It can be expressed as follows: (1) (2) In the formula is the coordinate of the measuring ship in the earth coordinate system, is the three-dimensional distance between the GNSS and USBL arm, is the attitude transfer matrix from the carrier coordinate system of the USBL array to the navigation coordinate system, It is the transformation matrix from the e system to the n system, the e system is the earth coordinate system, and the n system is the navigation coordinate system.

[0032] According to the coordinate transformation relationship, we can get: (3) In the formula is the attitude transfer matrix corresponding to the installation angle error angle, is the coordinate of the transponder in the array coordinate system.

[0033] Substituting formula (3) into formula (1), (4) In the formula Can be provided by GNSS equipment, Measured by attitude sensors, they are all observed quantities.

[0034] The key to the calibration of the ultra-short baseline system is to determine the three-dimensional distance between the first GNSS and the USBL arm and installation angle error angle . The three-dimensional distance between the first GNSS and the USBL arm Can be directly measured.

[0035] Therefore, when calibrating the installation error, it is necessary to first obtain and , put the result into formula (4) to calculate the attitude shift matrix , and then according to the attitude shift matrix Calculate the installation error angle .

[0036] Rewrite formula (4) into the following form: (5) in , , for The coordinates of the three axes, for The coordinates of the three axes are expanded to get (6) in

[0037] is the coordinate of the transponder in the array coordinate system The expanded form of represents the three-dimensional distance between the first GNSS and the USBL arm, The expanded form of .

[0038] The integrated SINS / USBL system has a small installation error angle. It can be approximated by an antisymmetric matrix: (7) Formula (6) can be transformed into: (8) Where: (9) (10) The optimal solution can be obtained directly using the least squares method: (11) The calibrated installation error angle is calculated from this.

[0039] 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. An ultra-short baseline installation error calibration system based on a rotating platform, characterized in that: include: A rotating platform used to fix the SINS / USBL integrated system on the mother ship; An underwater robot ROV used to carry a fixed transponder to a specified location in the water; The rotating platform drives the SINS / USBL integrated system to rotate. During the rotation process, the USBL continuously measures the transponder, and the installation error angle of the USBL relative to the SINS is obtained by solving the measurement.

2. The system according to claim 1, characterized in that The rotating platform comprises: a table top, a rotating shaft, a table body, and a control actuator for rotating the rotating shaft; wherein: The table is used to install the SINS / USBL integrated system. The table is fixedly connected to the shaft and can rotate 360 ​​degrees. The platform body is a single-axis turntable base, and the platform body is fixedly connected to the mother ship on the side facing the transponder; During the rotation of the shaft, the rotating platform ensures that the SINS / USBL integrated system is in a horizontal state, avoiding the situation where the transponder signal cannot be received during the rotation; The SINS / USBL integrated system is composed of SINS and USBL fixed up and down, tightly installed and sealed in a housing, and fixed to the central axis of the table.

3. The system according to claim 1, characterized in that include: The plurality of rotating platforms are used to calibrate a plurality of SINS / USBL integrated systems simultaneously. Each platform corresponds to a set of integrated SINS / USBL systems and are fixed in sequence on the side of the mother ship facing the transponder.

4. A system according to any one of claims 1 to 3, characterized in that: The mother ship is also equipped with a first GNSS system for acquiring the position of the mother ship.

5. The system according to claim 4, characterized in that The transponder is fixed on the top of the underwater robot ROV, and a second SINS system, a DVL, a second GNSS system and a depth gauge are also installed to form a navigation system for controlling the ROV to reach a predetermined position and ensuring that the transponder maintains a fixed position and posture.

6. A method for calibrating an ultra-short baseline installation error based on the system of claim 5, comprising the following steps: S1: Transponder position determination; S2: Fix the SINS / USBL integrated system to the corresponding rotating platform table, fixed on the side of the mother ship facing the transponder; S3: Use the pulse-per-second source of the first GNSS system on the mother ship to generate a precise pulse signal per second; Use a cable to connect the pulse-per-second output port of the first GNSS system on the mother ship to the pulse-per-second input ports of the SINS and USBL on the mother ship; S4: The rotating platform table rotates a certain angle at regular intervals, a total of 360 degrees, during which the SINS / USBL integrated system's attitude, position, slant range and azimuth, and the transponder's absolute geographic location and depth information are collected in real time; S5: Calculate the installation error angle of USBL relative to SINS in the SINS / USBL integrated system to be calibrated by using the position of each measuring point obtained by the first GNSS system, the attitude data provided by the SINS on the mother ship, and the slant range data and azimuth provided by the USBL system.

7. The method according to claim 6, characterized in that The step S1 comprises: Install the second SINS, DVL, second GNSS, and depth gauge on the small ROV to form a navigation system, and fix the transponder on the top of the ROV; First calibrate the parameters of the second SINS and DVL. After the surface alignment is completed, dive into the water, enter the second SINS and DVL combination state, carry the power cable to the predetermined position, hover or bottom, and determine the absolute position of the transponder based on the second SINS and DVL combination.

8. The method according to claim 6 or 7, characterized in that: In step S3, before performing second pulse synchronization, the time of the SINS system, USBL and the first GNSS system on the mother ship needs to be calibrated to ensure that the time difference between the three is within a set threshold range.

9. The method according to claim 6, characterized in that The solution method of step S5 includes: The slant distance between the USBL array and the transponder is expressed as the Euclidean distance between their coordinates. The specific formula is as follows: In the formula, is the coordinate of the USBL array in the earth coordinate system, is the coordinate of the transponder in the earth coordinate system; Will It is expressed as: (1) (2) In the formula, To measure the coordinates of the mother ship in the earth coordinate system, is the three-dimensional distance between the first GNSS and the USBL arm, is the attitude transfer matrix from the USBL array carrier coordinate system to the navigation coordinate system, is the transformation matrix from e system to n system; e system is the earth coordinate system, n system is the navigation coordinate system; According to the coordinate transformation relationship, we get: (3) In the formula is the attitude transfer matrix corresponding to the installation angle error angle, is the coordinate of the transponder in the array coordinate system; Substituting formula (3) into formula (1), (4) In the formula Provided by the first GNSS equipment, Measured by the attitude sensor of the mother ship SINS, all are observation quantities; The key to the calibration of the ultra-short baseline system is to determine the three-dimensional distance between the first GNSS on the mother ship and the USBL arm and installation error angle ; Among them, the three-dimensional distance between the first GNSS and the USBL arm Directly derived from measurement; When calibrating the installation error angle, first obtain and , Substitute the result into formula (4) to calculate the attitude transfer matrix , and then according to the attitude transfer matrix Calculate the installation error angle : Rewrite formula (4) into the following form: (5) in , , for The coordinates of the three axes, for The coordinates of the three axes are expanded to get (6) in is the coordinate of the transponder in the array coordinate system The expanded form of represents the three-dimensional distance between the first GNSS and the USBL arm, The expanded form of For the integrated SINS / USBL system, It can be approximated by an antisymmetric matrix: (7) Then formula (6) can be transformed into: (8) Where: (9) (10) Directly use the least squares method to get the optimal solution: (11) The installation error angle to be calibrated is calculated accordingly.

10. The method according to claim 6, characterized in that When multiple integrated SINS / USBL systems are calibrated simultaneously, S4 further includes the following steps: The integrated system of SINS / USBL is controlled by the synchronous pulse trigger of the main control computer system, so that it works in sequence at a certain time.

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