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

Abstract

A rotating platform-based ultra-short baseline installation error calibration system and method is described. The system comprises a rotating platform for securing a SINS / USBL integrated system to a mother vessel; and an underwater robot (ROV) for carrying a fixed transponder to a designated location in the water. The rotating platform rotates the SINS / USBL integrated system, during which the USBL continuously measures the transponder, calculating the installation error angle of the USBL relative to the SINS. This solution is simple to operate; the USBL installation error angle can be conveniently calibrated while the mother vessel is stationary, without the need for navigation. Multiple SINS and USBL integrated systems can also be calibrated simultaneously, significantly improving calibration efficiency.

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) systems are increasingly used in underwater navigation and positioning due to their advantages such as small size and strong flexibility.

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

[0004] If the strapdown inertial navigation system (SINS) and USBL are not integrated, they need to be recalibrated after each disassembly and assembly. This 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, requiring the carrier to execute a series of complex navigation trajectories. However, due to environmental reasons, the carrier cannot ideally navigate the predetermined trajectory on the lake. At the same time, the USBL is easily disturbed by the underwater environment during navigation, such as interference from the propeller, impact of water flow, and noise generated by aquatic organisms. These factors will further affect the positioning accuracy.

[0006] Before calibrating the installation angle, the position 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 offset in the position and orientation of the transponder. Summary of the Invention

[0007] In response to these problems existing in traditional calibration methods, the present disclosure 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 disclosure, the USBL and SINS are installed on the mother ship in an integrated manner via a rotating platform, while 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 USBL's deviation angle relative to the SINS without sailing.

[0009] Further:

[0010] The ROV is equipped with a SINS, DVL (Doppler Velocity Logger), GNSS (Global Navigation Satellite System Antenna) and a depth gauge to form a navigation system. The transponder is fixed on the top of the ROV.

[0011] The integrated SINS / USBL system consists of a SINS and USBL mounted vertically, securely installed, and sealed within a housing. The integrated system is then secured to a tabletop axis that can rotate 360 ​​degrees. If multiple integrated SINS / USBL systems need to be calibrated simultaneously, multiple tables are provided, one for each integrated SINS / USBL system, and each table is secured sequentially to one side of the mother ship, facing the transponder.

[0012] The present invention utilizes a small ROV to carry a transponder, and utilizes a combination of SINS and DVL to dive into a predetermined location and carry a cable. It can work for a long time and can 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.

[0013] The specific calibration method includes the following steps:

[0014] Transponder location determination;

[0015] Fix the SINS / USBL integrated system to the corresponding rotating platform table, fixed on the side of the mother ship facing the transponder;

[0016] 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;

[0017] The rotating platform table rotates a certain angle at a set time interval at a set speed 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.

[0018] 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 measurement 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.

[0019] 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, and the mother ship does not need to sail, but can be fixed, without the need for a complicated calibration route; (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

[0020] 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.

[0021] Figure 1 is a flow chart of an exemplary embodiment according to the present disclosure;

[0022] Figure 2 Schematic diagram of the rotating platform equipped with the SINS / USBL integrated system. DETAILED DESCRIPTION

[0023] The preferred embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although 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. Rather, 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.

[0024] The present disclosure provides a USBL installation error calibration system and method using a rotating platform and an underwater robot to calibrate the installation deviation angle of the USBL relative to the SINS in an integrated SINS / USBL system.

[0025] In one exemplary embodiment, the system includes:

[0026] (1) Rotating platform

[0027] The integrated SINS / USBL system consists of the SINS and USBL fixed up and down, tightly installed and sealed in a shell. The integrated system is then fixed to the table axis, and the table can rotate 360 ​​degrees.

[0028] As attached Figure 2As shown, the tabletop is used to mount the integrated SINS / USBL system, and the tabletop and shaft are rigidly connected. The table body is the base of the single-axis turntable. The motor, encoder, bearings, and slip rings are installed between the tabletop and the shaft. The motor drives the turntable, the encoder measures the angle of shaft rotation, the bearings support the shaft, and the slip rings transmit various electrical signals between the turntable and the tabletop. The tabletop is rigidly connected to the mothership. This ensures that the integrated SINS / USBL system remains level to prevent transponder signals from being lost when the tabletop rotates.

[0029] If multiple integrated SINS / USBL systems need to be calibrated simultaneously, multiple tables are set up, each corresponding to a multiple integrated SINS / USBL system, and fixed on one side of the mother ship in sequence, facing the position of the transponder.

[0030] In addition, a first GNSS system is installed on the mother ship to obtain the position of the mother ship.

[0031] (2) Transponder carrier

[0032] 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 can 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.

[0033] 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.

[0034] Based on the above system, the calibration method includes the following steps:

[0035] Step 1: Determine the transponder's position: Using a small ROV, install a second SINS, DVL, second GNSS antenna, and depth gauge on the ROV to form a navigation system. A transponder is then fixed to the top of the ROV. First, calibrate the parameters of the second SINS and DVL. After aligning the surface, dive into the water until the DVL's effective bottoming depth exceeds the lake's water depth. The DVL is effectively bottom-reaching throughout the entire dive. Enter the second SINS and DVL combined state, carry the power cable to the desired location, and hover or bottom-reach. The absolute position of the transponder is determined based on the second SINS and DVL combination, allowing for extended operation.

[0036] Step 2: Multiple SINS / USBL integrated systems are mounted on the corresponding platforms and then on one side of the mother ship, facing the transponder. GNSS position information with RTK fixed solution accuracy and SINS provide heading and attitude information, providing a more accurate attitude matrix and position for the USBL calibration method.

[0037] Step 3: Use the pulse-per-second source of the first GNSS to generate a precise pulse signal every second.

[0038] Use a cable to connect the PPS output port of the first GNSS system to the PPS input ports of the first INS and USBL. Ensure that the system can correctly identify and process the PPS signal from the first GNSS system. Before performing PPS synchronization, calibrate the time of the first INS, USBL, and first GNSS system to ensure that the time difference between them is within an acceptable range.

[0039] Step 4: The rotating platform table is then rotated and stopped at a certain time interval, and rotated 360 degrees. During this process, the SINS / USBL integrated system is controlled by the synchronous pulse trigger of the main control computer system, so that it works in sequence at a certain time, and collects the navigation attitude, position, slant range and azimuth of multiple sets of SINS / USBL integrated systems, and the absolute geographical location and depth information of the transponders in real time.

[0040] Step 5:

[0041] Record the first GNSS position of each measurement 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.

[0042] The slant range between the ultra-short baseline array and the transponder can be expressed as the Euclidean distance between their coordinates, as shown in the following formula:

[0043]

[0044] 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.

[0045] It can be expressed as follows:

[0046] (1)

[0047] (2)

[0048] 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, where the e system is the earth coordinate system and the n system is the navigation coordinate system.

[0049] According to the coordinate transformation relationship, we can get:

[0050] (3)

[0051] 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.

[0052] Substituting formula (3) into formula (1),

[0053] (4)

[0054] In the formula Can be provided by GNSS equipment, Measured by attitude sensors, they are all observation quantities.

[0055] The key to ultra-short baseline system calibration is to determine the three-dimensional distance between the first GNSS and the USBL arm and installation angle error angle 3D distance between the first GNSS and the USBL arm Can be directly measured.

[0056] 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 posture shift matrix Calculate the installation error angle .

[0057] Rewrite formula (4) into the following form:

[0058] (5)

[0059] in , , for The coordinates of the three axes, for The coordinates of the three axes are expanded to (5)

[0060] (6)

[0061] in

[0062] 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 .

[0063] The integrated SINS / USBL system has a small installation error angle. It can be approximated by an antisymmetric matrix:

[0064] (7)

[0065] Formula (6) can be changed to:

[0066] (8)

[0067] Where:

[0068] (9)

[0069] (10)

[0070] The optimal solution can be obtained directly using the least squares method:

[0071] (11)

[0072] The calibrated installation error angle is calculated from this.

[0073] The above technical solutions are only exemplary embodiments 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 are not limited to the methods described in the above specific embodiments of the present invention. Therefore, the methods described above are only preferred and do 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 for fixing the SINS / USBL integrated system on the mother ship; An underwater robot (ROV) used to carry a fixed transponder to a designated 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 calculation. The rotating platform includes: a table, 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 fixed to the shaft and can rotate 360 ​​degrees. The platform is a single-axis turntable base, which is fixed 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 process; The SINS / USBL integrated system consists of a SINS and a USBL fixed up and down, tightly mounted and sealed in a housing, and fixed to the central axis of the table; The mother ship is also equipped with a first GNSS system for acquiring the position of the mother ship; The transponder is fixed on the top of the underwater robot ROV, and is also equipped with a second SINS system, DVL, a second GNSS system and a depth gauge to form a navigation system for controlling the ROV to reach a predetermined position and ensuring that the transponder maintains a fixed position and attitude.

2. The system according to claim 1, wherein: include: The multiple rotating platforms are used to calibrate multiple SINS / USBL integrated systems simultaneously. Each platform corresponds to one integrated SINS / USBL system and is fixed in sequence on the side of the mother ship facing the transponder.

3. A method for calibrating an ultra-short baseline installation error based on the system of claim 1 or 2, 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: Utilizes 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 for a total of 360 degrees. During this process, the SINS / USBL integrated system's attitude, position, slant range, and azimuth, as well as the transponder's absolute geographic location and depth information are collected in real time. S5: Using the positions of each measurement 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, the installation error angle of the USBL relative to the SINS in the SINS / USBL integrated system to be calibrated is calculated.

4. The method according to claim 3, 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.

5. The method according to claim 3 or 4, 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.

6. The method according to claim 3, 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: Where, is the coordinate of the USBL array in the earth coordinate system, is the coordinate of the transponder in the earth coordinate system; Will Expressed as: Where, To measure the coordinates of the mother ship in the earth coordinate system, L b 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 the e-system to the n-system; the e-system is the earth coordinate system, and the n-system is the navigation coordinate system; According to the coordinate transformation relationship, we get: 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), 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 L between the first GNSS on the mother ship and the USBL arm. b and installation error angle θ x ,θ y ,θ z ; Among them, the three-dimensional distance L between the first GNSS and the USBL arm b Directly derived from measurement; When calibrating the installation error angle, first calculate L b and Substitute the obtained result into formula (4) to calculate the attitude transfer matrix Then according to the posture transfer matrix Calculate the installation error angle θ x ,θ y ,θ z : Rewrite formula (4) into the following form: in for The coordinates of the three axes, for The coordinates of the three axes are expanded to (5) in is the coordinate of the transponder in the array coordinate system The expanded form of The three-dimensional distance between the first GNSS and the USBL arm, L b The expanded form of For the integrated SINS / USBL system, It can be approximated by an antisymmetric matrix: Then formula (6) can be transformed into: Where: Directly use the least squares method to obtain the optimal solution: The installation error angle to be calibrated is calculated accordingly.

7. The method according to claim 3, characterized in that When multiple integrated SINS / USBL systems are calibrated simultaneously, the step S4 further includes the following steps: The integrated SINS / USBL system is controlled by the synchronous pulse trigger of the main control computer system, so that it works in sequence at a certain time.

Images