An underwater robot self-adjusting channel-oriented acousto-optic communication positioning method

Abstract

The application discloses an underwater robot self-adjusting channel-oriented acousto-optic communication positioning method, through constructing an underwater dynamic acousto-optic fusion repeater, first, an acoustic link is used to realize wide-area guaranteed connection with an underwater robot, provide meter-level precision coarse positioning covering the whole operation area, provide prior information for subsequent fast establishment of an optical link, then dynamically compress the optical search area to realize fast and accurate link establishment, and then according to real-time link quality evaluation (signal-to-noise ratio), realize self-adjusting and smooth switching among three transmission modes of acoustics, optics and acousto-optics, so that the depth coupling and cooperative scheduling of acousto-optics are realized, and the advantages of reliable connection at a long distance, high-speed data return at a short distance and high-precision positioning are combined, and the core technical problems that distance and speed cannot be compatible and positioning precision and coverage range are mutually restricted in the prior art are solved.

Description

An acoustic-optical communication-based positioning method for autonomous channel adjustment of underwater robots Technical Field

[0001] This invention relates to a communication and positioning method for underwater robots, and more particularly to an acoustic-optical communication and positioning method for underwater robots with autonomous channel adjustment. Background Technology

[0002] Currently, autonomous underwater vehicles (AUVs) are widely used in complex tasks such as marine exploration and environmental monitoring. Highly reliable data communication and precise positioning capabilities are two key supports for AUVs to complete complex collaborative operations. Traditional underwater communication and positioning technologies mainly rely on two independent modes: acoustic or optical. Although acoustic communication has the advantage of long propagation distance, its inherent low bandwidth and high latency severely limit the real-time transmission of large amounts of data (such as images). Optical communication, while potentially offering high bandwidth and low latency, suffers from severe signal attenuation in water, resulting in a short effective range and high requirements for link alignment accuracy. Furthermore, it is highly susceptible to interference from environmental factors such as water turbidity, platform sway, and biological obstruction, leading to poor link stability.

[0003] To overcome the technological limitations of traditional single-modal communication, the industry has proposed acoustic-optical fusion communication and positioning systems. However, existing acoustic-optical fusion systems mostly remain at the level of simple functional superposition. Specifically, the system relies on fixed distance thresholds or manual commands to mechanically switch between acoustic and optical communication modes. The acoustic and optical modules are isolated from each other during operation, lacking intelligent collaborative decision-making and closed-loop control based on real-time link quality and task requirements. It is still difficult to simultaneously meet the dual requirements of reliable long-distance control and high-speed short-distance data transmission, and there are core technical challenges such as the trade-off between distance and data rate, and the mutual constraints between positioning accuracy and coverage. Summary of the Invention

[0004] The present invention aims to solve the aforementioned technical problems existing in the prior art by providing an acoustic-optical communication positioning method for autonomous channel adjustment of underwater robots.

[0005] The technical solution of this invention is: an acoustic-optical communication positioning method for autonomous channel adjustment of underwater robots, comprising a surface mother ship, an underwater robot, an acoustic communication module, and a laser communication system, and equipped with an underwater mobile repeater, wherein the underwater mobile repeater carries the acoustic communication module and the laser communication system, and the surface mother ship, the acoustic communication module, and the laser communication system communicate with the underwater mobile repeater respectively, and is carried out according to the following steps:

[0006] Step 1. The surface mother ship issues mission instructions;

[0007] Step 2. The underwater mobile repeater establishes a wide-area connection with the underwater robot through an acoustic channel;

[0008] Step 3. The underwater mobile repeater determines the optical communication area of ​​the laser communication system based on acoustic information;

[0009] Step 4. Calculate the optical communication signal-to-noise ratio (SNR) for the underwater mobile repeater;

[0010] Step 5. The underwater mobile repeater determines the relationship between the optical communication signal-to-noise ratio (SNR) and the threshold. If the optical communication SNR is greater than the maximum threshold SNR... high Data is transmitted using an optical channel; if the optical communication signal-to-noise ratio (SNR) is less than the minimum threshold SNR... low Data is transmitted using an acoustic channel; if the optical communication signal-to-noise ratio (SNR) is greater than or equal to the minimum threshold SNR... low And less than or equal to the maximum threshold SNR high Data can be transmitted simultaneously using an optical-acoustic channel;

[0011] Step 6. The underwater robot collects data and transmits it back to the underwater mobile repeater;

[0012] Step 7. The underwater mobile repeater fuses and processes the data and transmits it back to the surface mother ship;

[0013] Step 8. The surface mother ship analyzes the data and generates new instructions, then returns to Step 1.

[0014] Step 3 involves determining the optical communication area of ​​the laser communication system according to the following formula:

[0015] ;

[0016] in, For optical communication area, Pi The distance between the repeater and the target underwater robot estimated for acoustic localization. The laser beam divergence angle is... This represents the standard deviation of the positioning error of the acoustic positioning system.

[0017] Step 4 involves calculating the optical communication signal-to-noise ratio (SNR) using the following formula:

[0018]

[0019] in, , , , , These are, respectively, the transmit power, transmit efficiency, receive efficiency, receive aperture area, and beam divergence angle. and The distance between the repeater and the target underwater robot is estimated by the water attenuation coefficient and acoustic positioning, respectively. and For noise power spectral density and system bandwidth.

[0020] The specific operation of transmitting data simultaneously using the optical-acoustic channel in step 5 involves transmitting key data through the acoustic channel and transmitting large amounts of data through the optical channel, using the following weighting function. Dynamically adjust the data load of the optical channel:

[0021] ;

[0022] in This is for adjusting the coefficient.

[0023] This invention constructs an underwater dynamic acoustic-optical fusion repeater. First, it utilizes an acoustic link to achieve a wide-area guaranteed connection with an underwater robot, providing meter-level precision coarse positioning covering the entire operating area. This provides prior information for the rapid establishment of subsequent optical links. Then, it dynamically compresses the optical search area to achieve rapid and accurate link establishment. Based on real-time link quality assessment (signal-to-noise ratio), it autonomously and smoothly switches between acoustic, optical, and acoustic-optical hybrid transmission modes, thereby achieving deep coupling and collaborative scheduling of acoustic and optical signals. It combines the advantages of long-distance reliable connection, short-distance high-speed data backhaul, and high-precision positioning, solving the core technical problems of existing technologies where distance and speed are mutually exclusive and positioning accuracy and coverage are mutually constrained. Attached Figure Description

[0024] Figure 1 is a flowchart of an embodiment of the present invention. Detailed Implementation

[0025] This invention discloses an acoustic-optical communication positioning method for autonomous channel adjustment of underwater robots. Similar to existing technologies, it includes a surface mother ship, an underwater robot, an acoustic communication module (acoustic transducer array), and a laser communication system. The acoustic communication module and the laser communication system communicate with the underwater robot. Unlike existing technologies, this invention includes an underwater mobile repeater connected to the surface mother ship by a cable. The surface mother ship provides a continuous power supply to the underwater mobile repeater. The underwater mobile repeater carries the acoustic communication module and the laser communication system. The surface mother ship, the acoustic communication module, and the laser communication system communicate with the underwater mobile repeater.

[0026] The specific settings for the equipment are as follows:

[0027] Surface mothership: The hardware is equipped with a high-performance industrial control computer as the central processing unit, and integrates an EvoLogics S2C acoustic modem to realize remote communication with underwater nodes. It provides power supply and data transmission link to the underwater mobile repeater through a cable. The software is developed on the Ubuntu operating system and ROS robot framework to realize global control, intelligent scheduling and closed-loop management of the entire system.

[0028] Underwater mobile repeater: The hardware core adopts an embedded AI platform, equipped with an acoustic communication module to maintain network connectivity, integrates the BlueRobotics laser communication system to achieve high-speed data transmission, and is equipped with a FLIR industrial camera to complete optical positioning. It achieves underwater movement and precise position adjustment through a multi-thrust system. The software runs an acousto-optic protocol conversion gateway and a fast acquisition algorithm under the ROS framework. It has real-time link quality monitoring and intelligent beam alignment capabilities, and can dynamically optimize communication performance according to channel conditions, achieving a smooth transition from acoustic baseline to optical enhancement.

[0029] The underwater robot uses a computing module as the main controller, integrates a miniature acoustic modem to receive control commands, is equipped with a high-power LED optical beacon for positioning assistance, and carries a high-definition camera sensor to complete underwater image acquisition, forming a complete perception and communication terminal. The node agent software is written in Python 3.8 to realize acoustic command parsing, rapid establishment of optical links, and intelligent management of sensor data, ensuring reliable communication connection and data transmission capabilities in complex underwater environments.

[0030] Task scenario description:

[0031] The mission scenario of this invention is nearshore coral reef ecological monitoring, which involves using an underwater robot swarm to acquire high-definition images and transmit environmental data back to the coral reef area. The mission area is at a depth of 50 meters, covering an area of ​​approximately 500 meters × 500 meters, with significant variations in water turbidity, posing risks of biological obstruction and platform swaying. Mission requirements:

[0032] 1. Achieve cooperative positioning for underwater robot swarms (accuracy requirements: acoustic meter-level, optical centimeter-level);

[0033] 2. High-speed transmission of high-definition video data (rate ≥ 50 Mbps);

[0034] 3. Ensure that the communication link is not interrupted under turbidity fluctuations.

[0035] The flowchart of the method of this embodiment is shown in Figure 1, and it is carried out according to the following steps:

[0036] Step 1. The surface mother ship issues mission instructions.

[0037] Step 2. The underwater mobile repeater (hereinafter referred to as the repeater) establishes a wide-area connection with the underwater robot through an acoustic channel, transmitting small-volume, high-reliability signaling such as system wake-up, scheduling commands, and status feedback to ensure uninterrupted control link and provide meter-level accuracy coarse positioning covering the entire operating area, providing prior information for the rapid establishment of subsequent optical links. Specifically, this can be achieved by deploying an acoustic transducer array on the underwater mobile repeater to transmit specific frequency acoustic signals into the working water area. After receiving the acoustic signal, the underwater robot returns a response signal, and the system measures the round-trip time of the signal. Combined with the speed of sound propagation in water Calculate the distance between the robot and the reference node. When multiple reference nodes are used, the system uses the time difference of arrival. Measurements were taken to establish the positioning equations.

[0038]

[0039] in, This represents the distance difference between the i-th reference node and reference node 0. The target location is to be determined. For the first The coordinates of each reference node. The coordinates of the specified reference node 0 (usually referring to the coordinates of the surface mother ship). By solving this system of equations, coarse positioning with meter-level accuracy can be achieved within a range of several hundred meters. This provides an initial position estimate for subsequent precise optical positioning.

[0040] Step 3. The repeater determines the optical communication area of ​​the laser communication system based on acoustic information. After that, the optical system only needs to be in the area Scanning within the area allows for rapid link establishment. The optical communication area of ​​the laser communication system is determined using the following formula:

[0041]

[0042] in, For optical communication area, Pi The distance between the repeater and the target underwater robot estimated for acoustic positioning ( ), The laser beam divergence angle is... The standard deviation of the positioning error of the acoustic positioning system. , .

[0043] Step 4. Calculate the optical communication signal-to-noise ratio (SNR) of the underwater mobile repeater using the following formula:

[0044]

[0045] in, , , , , These are, respectively, the transmit power, transmit efficiency, receive efficiency, receive aperture area, and beam divergence angle. and These represent the distance between the repeater and the target underwater robot, estimated by the water attenuation coefficient and acoustic positioning, respectively. and For noise power spectral density and system bandwidth.

[0046] Step 5. The underwater mobile repeater determines the relationship between the optical communication signal-to-noise ratio (SNR) and the threshold. If the optical communication SNR is greater than the maximum threshold SNR... high Using optical channels to transmit data maximizes data transmission rate and positioning accuracy; if the optical communication signal-to-noise ratio (SNR) is less than the minimum threshold SNR... low Data is transmitted using an acoustic channel to ensure uninterrupted basic connectivity; if the optical communication signal-to-noise ratio (SNR) is greater than or equal to the minimum threshold SNR... low And less than or equal to the maximum threshold SNR high Data is transmitted simultaneously using an optical-acoustic channel. Specifically, critical data (such as control commands) is transmitted error-free through the acoustic channel, while large data volumes (such as images) are transmitted through the optical channel, using the following weighting function. Dynamically adjust the data load of the optical channel:

[0047]

[0048] in To adjust the coefficient, let's assume... Calculated This means that the optical channel load is reduced to 40%, avoiding link oscillation. This function allows the system to smoothly transition between acoustic backstop and optical enhancement, avoiding link oscillation caused by frequent switching, thereby achieving the optimal balance between communication performance and reliability in complex and variable underwater environments.

[0049] Step 6. The underwater robot collects data and transmits it back to the underwater mobile repeater. That is, the collected sensing data and its own status information are transmitted back to the repeater through the established communication link.

[0050] Step 7. The underwater mobile repeater fuses and processes the data and transmits it back to the surface mother ship. Specifically, the underwater mobile repeater performs preliminary integration of the received data (acoustic positioning data, optical images, robot status) and forwards it to the surface mother ship through the uplink.

[0051] Step 8. The surface mothership analyzes the data and generates new instructions. Specifically, the central processing unit on the surface mothership uses a Kalman filter to fuse acoustic and optical positioning results, generating a high-precision trajectory map. Simultaneously, the surface mothership dynamically adjusts the position of the underwater mobile repeater based on the fused data (e.g., avoiding areas with high turbidity) and issues new task instructions (e.g., focusing on monitoring areas of coral reef degradation), forming a closed loop of "perception-transmission-decision-control," before returning to Step 1. The optical positioning is based on machine vision principles, capturing the light signals emitted by the target node through an image sensor and establishing the following projection equation:

[0052]

[0053] in, This represents the pixel coordinates of the light spot on the image plane. For the camera intrinsic parameter matrix, For the camera extrinsic matrix, The world coordinates of the target node. This is the scaling factor. By solving this projection equation and combining data from multiple observation points, precise positioning with centimeter-level accuracy can be achieved within a certain range.

[0054] The effects of implementing this invention are as follows:

[0055] Improved communication performance: The optical link achieves high-speed data transmission of 100 Mbps over a distance of 50 meters, a 10-fold improvement over single acoustic communication (10 kbps). 4 The acoustic backstop mechanism ensures zero link interruption even under turbidity fluctuations.

[0056] Positioning accuracy optimization: The positioning accuracy has been improved from ±2 meters for acoustic positioning to ±5 centimeters for optical positioning, meeting the needs of fine monitoring of coral reefs.

[0057] System Adaptive Capability: The SNR-based adaptive decision-making mechanism enables the system to smoothly transition between acoustic, optical, and acousto-optic hybrid transmission modes, reducing the number of switching operations by up to 70% and improving task efficiency.

[0058] Task completion rate: The underwater robot cluster completed full coverage monitoring of a 500m×500m area within 4 hours, with a data transmission integrity rate of ≥95% and a continuous positioning trajectory without any breaks.

Claims

1. A method for acoustic-optical communication positioning for autonomous channel adjustment of underwater robots, comprising a surface support vessel, an underwater robot, an acoustic communication module, and a laser communication system, characterized in that: An underwater mobile repeater is provided, connected to a surface mother ship by a cable. The underwater mobile repeater carries an acoustic communication module and a laser communication system. The surface mother ship, the acoustic communication module, and the laser communication system communicate with the underwater mobile repeater according to the following steps: Step 1. The surface mother ship issues a mission command; Step 2. The underwater mobile repeater establishes a wide-area connection with the underwater robot through an acoustic channel; Step 3. The underwater mobile repeater determines the optical communication area of ​​the laser communication system based on acoustic information according to the following formula: ;in, For optical communication area, Pi The distance between the repeater and the target underwater robot estimated for acoustic positioning. The laser beam divergence angle is... Step 4. The underwater mobile repeater calculates the optical communication signal-to-noise ratio (SNR); Step 5. The underwater mobile repeater determines the relationship between the optical communication SNR and a threshold. If the optical communication SNR is greater than the maximum threshold SNR... high Data is transmitted using an optical channel; if the optical communication signal-to-noise ratio (SNR) is less than the minimum threshold SNR... low Data is transmitted using an acoustic channel; if the optical communication signal-to-noise ratio (SNR) is greater than or equal to the minimum threshold SNR... low And less than or equal to the maximum threshold SNR high Data is transmitted simultaneously using an optical-acoustic channel. Specifically, key data is transmitted via the acoustic channel, while large amounts of data are transmitted via the optical channel, using the following weighting function. Dynamically adjust the data load of the optical channel: ;in To adjust the coefficients; Step 6. The underwater robot collects data and transmits it back to the underwater mobile repeater; Step 7. The underwater mobile repeater fuses and processes the data and transmits it back to the surface mother ship; Step 8. The surface mother ship analyzes the data and generates new instructions. That is, the central processing unit of the surface mother ship uses a Kalman filter to fuse the acoustic and optical positioning results to generate a high-precision trajectory map. At the same time, the surface mother ship dynamically adjusts the position of the underwater mobile repeater according to the fused data and issues new task instructions, returning to Step 1.

2. The acoustic-optical communication positioning method for autonomous channel adjustment of underwater robots according to claim 1, characterized in that... Step 4 involves calculating the optical communication signal-to-noise ratio (SNR) using the following formula: ;in, ， ， ， ， These are, respectively, the transmit power, transmit efficiency, receive efficiency, receive aperture area, and beam divergence angle. and These represent the distance between the repeater and the target underwater robot, estimated by the water attenuation coefficient and acoustic positioning, respectively. and For noise power spectral density and system bandwidth.

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