Acoustic positioning system and method for large underwater multi-targets in a dock

Abstract

The application discloses a kind of underwater large-scale multi-target acoustic positioning system and method in dock, belong to underwater acoustic positioning technical field.System includes underwater mobile target, shore base central control room and at least three acoustic emission base station;Each acoustic emission base station emits acoustic pulse signal in turn according to preset TDMA timing;Underwater mobile target includes acoustic receiving terminal, receiving transducer can be received protective structure, underwater acoustic communication equipment, sealed protective cabin and local solution unit, underwater mobile target receives acoustic pulse signal from each acoustic emission base station, executes hierarchical check and TDOA solution, and outputs the real-time coordinate and state data of underwater mobile target itself, and real-time coordinate and state data are reported to shore base central control room by underwater acoustic communication link;Shore base central control room carries out global monitoring, path planning and task scheduling to underwater mobile target, and issues operation instruction to underwater mobile target.The system provides centimeter-level precision positioning for multiple underwater mobile targets.

Description

Technical Field

[0001] This invention belongs to the field of underwater acoustic positioning technology, and particularly relates to a large-scale underwater multi-target acoustic positioning system and method in a dock. Background Technology

[0002] In shipbuilding and repair, the cost of docking time is extremely high. To improve dock turnover efficiency, multiple underwater mobile carriers need to work together to complete precise operations such as intelligent handling and autonomous adjustment of dock piers, hull cleaning, and underwater welding while the dock is flooded. This requires centimeter-level positioning accuracy for each moving underwater target.

[0003] While existing underwater acoustic positioning methods, such as long-baseline methods, possess high-precision potential in ideal water bodies, they face three major challenges in practical applications in medium to large-sized docks: Strong multipath interference: The reinforced concrete walls, rigid bottom, and hundreds of fixed dock piers of varying heights surrounding the dock strongly reflect sound waves, creating complex "intra-pulse multipath" effects. This leads to severe distortion of the received waveform, reducing the actual positioning accuracy of conventional methods to the meter level. Signal obstruction: Conventional solutions often install acoustic terminals at low points on the mobile platform, making the signal easily obstructed by surrounding fixed dock piers. This results in positioning interruptions or unreliability, failing to meet the requirements for continuous positioning by self-propelled dock piers. Large-scale multi-target signal conflict: When dozens or even hundreds of underwater mobile targets operate in parallel within the same dock, if each target actively transmits acoustic signals in the traditional manner, a large number of signals superimpose in the water and, after multiple reflections from the walls and dock piers, form an extremely complex interference field. Literature studies have shown that in multi-user underwater acoustic networks, although the TDMA (Time Division Multiple Address) scheme can avoid collisions, it will introduce a large system delay; unscheduled concurrent transmission will lead to signal collisions, making it difficult for the receiver to extract effective direct waves from complex signals, resulting in a serious decrease in positioning accuracy or even complete failure.

[0004] When the number of moving targets surges to dozens or even hundreds (such as in the case of a batch of self-propelled intelligent dock piers), the simultaneous or time-sharing transmission of signals by all targets not only increases the power consumption and hardware complexity of each target, but more seriously, the superposition of numerous transmitted signals within the limited space of the dock, and multiple reflections by the pool walls and dock piers, create an extremely complex interference field. The receiving base station struggles to accurately separate the signals from each target, leading to a sharp deterioration in system performance. Studies have shown that in multi-user underwater acoustic networks, while TDMA schemes can avoid collisions, they introduce significant system delays; and if unscheduled concurrent transmission is used, signal collisions will cause complete positioning failure. Therefore, there is an urgent need for a positioning system and method that can fundamentally avoid multi-target signal collisions, has low power consumption, strong anti-interference capabilities, autonomous calculation capabilities, and robust engineering protection to support large-scale underwater multi-target collaborative operations. Summary of the Invention

[0005] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a large-scale underwater multi-target acoustic positioning system and method in a dock. This system can provide centimeter-level positioning accuracy for multiple underwater moving targets (such as self-propelled intelligent dock piers) in the state of flooding of medium and large docks, and has good adaptability.

[0006] In a first aspect, the present invention provides a large-scale underwater multi-target acoustic positioning system in a dock, the system comprising an underwater moving target, a shore-based central control room, and at least three acoustic transmission base stations; The acoustic transmission base stations are deployed on high platforms pre-erected around the dock's pool walls. The installation height of the acoustic transmission base stations is higher than the highest point of all static obstacles in the dock. Each acoustic transmission base station transmits acoustic pulse signals sequentially according to a preset TDMA timing sequence. The underwater moving target includes an acoustic receiving terminal, a retractable protective structure for receiving transducers, underwater acoustic communication equipment, a sealed protective chamber, and a local calculation unit. The underwater moving target receives acoustic pulse signals from various acoustic transmitting base stations through the local calculation unit, performs hierarchical verification and TDOA calculation, outputs its own real-time coordinates and status data, and reports the real-time coordinates and status data to the shore-based central control room through the underwater acoustic communication link. The shore-based central control room receives real-time coordinates and status data of the underwater moving target, performs global monitoring, path planning and task scheduling of the underwater moving target, and issues operation instructions to the underwater moving target.

[0007] According to one embodiment of the present invention, the step of receiving acoustic pulse signals from various acoustic transmitting base stations, performing hierarchical verification and TDOA calculation, and outputting the real-time coordinates and status data of the underwater moving target itself includes: The system receives acoustic pulse signals from various acoustic transmission base stations, sends the acoustic pulse signals to a matched filter bank, and verifies the acoustic pulse signals based on a dual verification mechanism to obtain the acoustic pulse signals that pass the verification. The acoustic pulse signals that pass the verification are subjected to narrow window truncation, matched filtering, and waveform morphology discrimination to obtain the acoustic pulse signals that pass the discrimination. Based on the acoustic pulse signal that has passed the discrimination test, the effective TDOA equations are calculated and the position is solved to obtain a preliminary estimate of the underwater moving target. If the number of effective TDOA equations is greater than the positioning dimension, the initial estimate of the underwater moving target is subjected to time delay consistency verification and Kalman filtering smoothing, and the real-time coordinates and status data of the underwater moving target are output. If the effective TDOA equation number equals the positioning dimension, no time delay consistency check is performed. The initial estimate of the underwater moving target is smoothed by Kalman filtering, and the real-time coordinates and status data of the underwater moving target are output. If the number of valid TDOA equations is less than the positioning dimension, determine whether there is a preliminary estimate of the underwater moving target. If there is, output the preliminary estimate of the underwater moving target; if there is no, report positioning loss.

[0008] According to one embodiment of the present invention, the step of sending the acoustic pulse signal to a matched filter bank and verifying the acoustic pulse signal based on a dual verification mechanism to obtain a verified acoustic pulse signal includes: The acoustic pulse signal is subjected to adaptive threshold detection using a constant false alarm rate detector to locate the pulse start time and obtain the received signal; The received signal is sent to the matched filter bank, the filter number that generates the maximum correlation peak is identified, the base station to which the signal belongs is determined, and double verification is performed in combination with the TDMA time slot to obtain the acoustic pulse signal that passes the verification.

[0009] According to one embodiment of the present invention, the step of performing narrow window truncation, matched filtering, and waveform morphology discrimination on the verified acoustic pulse signal to obtain the discriminated acoustic pulse signal includes: The first zero-crossing point detected is used as the starting point for extracting a window of signal within a preset time range from the acoustic pulse signal that has passed the verification. Matched filtering is performed on the captured window signal to obtain the time delay estimation signal; The kurtosis and skewness coefficients of the time delay estimation signal are calculated, and the effective direct waves are screened to obtain the acoustic pulse signals that are judged to pass.

[0010] According to one embodiment of the present invention, the step of performing effective TDOA equation calculation and position solution based on the determined acoustic pulse signal to obtain a preliminary estimate of the underwater moving target includes: Based on the acoustic pulse signals that have passed the discrimination, the number of effective base stations is obtained, an effective TDOA equation set is established, and the relationship between the number of effective TDOA equations and the positioning dimension is determined. If the number of effective TDOA equations is less than the positioning dimension, the current solution is abandoned. It is then determined whether the timeliness of the positioning estimate at the previous moment meets the preset time threshold. If it does, the positioning estimate at the previous moment is used as the preliminary estimate of the underwater moving target. If it does not meet the threshold, the positioning loss is reported. If the number of effective TDOA equations equals the positioning dimension, the effective TDOA equations are solved using the first weighted least squares method to obtain a preliminary estimate of the underwater moving target. If the number of effective TDOA equations is greater than the positioning dimension, the effective TDOA equations are solved using the quadratic weighted least squares method to obtain a preliminary estimate of the underwater moving target.

[0011] According to an embodiment of the present invention, the step of solving the effective TDOA equations based on the quadratic weighted least squares method to obtain a preliminary estimate of the underwater moving target includes: The distance from the underwater moving target to the reference base station is obtained as an auxiliary variable; Transform the effective TDOA equation system into a pseudo-linear equation system based on auxiliary variables; The pseudo-linear equations are transformed into matrix form and solved to obtain the first preliminary estimate. Calculate the error value of the first preliminary estimate, construct the observation vector and design matrix based on the error value, and solve to obtain the preliminary estimate of the underwater moving target.

[0012] According to one embodiment of the present invention, the step of performing time delay consistency verification and Kalman filtering smoothing on the preliminary estimate of the underwater moving target, and outputting the real-time coordinates and status data of the underwater moving target itself, includes: The expected latency of each acoustic transmission base station is calculated based on the preliminary estimate of the underwater moving target. The result is compared with the measured latency. Abnormal observations with deviations exceeding a preset threshold are removed to obtain the remaining acoustic transmission base station data. The coordinates of the underwater moving target are recalculated based on the remaining acoustic transmission base station data until a continuous positioning result sequence after consistency verification is obtained. The continuous positioning result sequence is smoothed by Kalman filtering to suppress random noise in the measurement and output the real-time coordinates and status data of the underwater moving target.

[0013] According to one embodiment of the present invention, the underwater moving target further includes a first receiver and a second receiver. The first receiver and the second receiver are arranged at a predetermined distance from each other along the longitudinal centerline on the top of the underwater moving target. The first receiver and the second receiver independently receive acoustic pulse signals from each acoustic transmitting base station and calculate their own coordinates. The coordinates of the first receiver and the second receiver are used to solve the heading angle of the underwater moving target.

[0014] Secondly, the present invention provides an acoustic localization method for large-scale underwater multi-target positioning within a shipyard, the method comprising: Acoustic pulse signals are transmitted sequentially through an acoustic transmission base station according to a preset TDMA timing sequence. The acoustic transmission base station is deployed on a high platform pre-erected around the pool wall of the dock, and the installation height of the acoustic transmission base station is higher than the highest point of all static obstacles in the dock. The local calculation unit receives acoustic pulse signals from various acoustic transmission base stations, performs hierarchical verification and TDOA calculation, outputs the real-time coordinates and status data of the underwater moving target, and reports the real-time coordinates and status data to the shore-based central control room through the underwater acoustic communication link. The underwater moving target includes an acoustic receiving terminal, a retractable protective structure for receiving transducers, underwater acoustic communication equipment, a sealed protective chamber, and a local calculation unit. It receives real-time coordinates and status data of underwater moving targets, performs global monitoring, path planning and task scheduling of underwater moving targets through the shore-based central control room, and issues operation instructions to underwater moving targets.

[0015] Thirdly, the present invention provides an electronic device including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements the acoustic positioning system for large-scale underwater multi-target positioning in a dock as described in the first aspect above.

[0016] Fourthly, the present invention provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the large-scale underwater multi-target acoustic positioning system in a dock as described in the first aspect above.

[0017] Fifthly, the present invention provides a chip including a processor and a communication interface, the communication interface being coupled to the processor, the processor being used to run programs or instructions to realize the large-scale underwater multi-target acoustic positioning system in the dock as described in the first aspect.

[0018] In a sixth aspect, the present invention provides a computer program product, including a computer program that, when executed by a processor, implements the acoustic positioning system for large-scale underwater multi-target positioning in a dock as described in the first aspect above.

[0019] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

[0020] The present invention provides a large-scale underwater multi-target acoustic positioning system for docks, which has the following advantages over the prior art: (1) This invention employs a signal flow design with a few fixed base stations transmitting and multiple targets passively receiving signals. The number of transmitting signal sources is fixed and independent of the number of targets. Regardless of how many moving targets are operating simultaneously in the dock, the signal environment remains clean and controllable. This reduces the signal chaos problem caused by the linear increase in the number of signal sources with the number of targets in traditional solutions, truly realizing large-scale parallel deployment of multiple targets and reducing large-scale multi-target signal conflicts. Through the synergistic effect of fixed base station transmission, physical elevation of line-of-sight propagation, a five-level anti-multipath protection system, and a dual signal identification mechanism, the problem of positioning accuracy degradation in the strong multipath environment of the dock is effectively solved. It can stably achieve centimeter-level positioning errors, meeting the needs of various underwater precision operations.

[0021] (2) This invention employs a dual identification mechanism of TDMA time slot division and differentiated LFM slope. The moving target initially determines the signal source through time slot assignment, and then performs secondary confirmation through waveform characteristics. Even if the signals from different base stations overlap in the time domain due to propagation delay, or if the reflected wave falls into other time slots due to multipath effects, the receiver can still accurately identify the signal source through signal characteristics, fundamentally reducing the calculation errors caused by "false identification" and improving the reliability of signal source identification. The moving target of this invention only needs to integrate the receiving circuit, without the need for a transmitting power amplifier or a high-power sound source, which significantly reduces the power consumption and hardware cost of each target, extends the underwater operation time, and improves the system reliability, making it particularly suitable for large-scale deployment scenarios.

[0022] (3) This invention completes local positioning calculations for each moving target. Even if the underwater acoustic communication link is briefly interrupted, each target can still continuously and autonomously locate itself and record its trajectory. After communication is restored, data is transmitted back in batches, greatly enhancing robustness to complex working conditions. It has high autonomy and resistance to communication interruptions. Moreover, both the transmitting base station and the receiving terminal are erected on all static obstacles, forming an unobstructed line-of-sight propagation path, reducing the problem of signal obstruction by low obstacles, and realizing continuous and reliable positioning throughout the entire dock area, with unobstructed coverage of the entire pool area.

[0023] (4) This invention, through its retractable acoustic transducer design, can reduce the risk of target damage under dry pressure conditions or reduce the impact of surface contaminant adhesion on acoustic performance, depending on the specific application scenario. The fully waterproof penetration joint and high-level sealed protective chamber ensure long-term stable operation of the electronic system underwater, providing comprehensive engineering protection and accommodating various working conditions. This system can automatically switch positioning dimensions based on the number of effective base stations: when there are sufficient base stations, it provides complete three-dimensional centimeter-level coordinates; when only three effective base stations remain, if the moving target is a bottom-mounted carrier with known depth, the system automatically reduces to two-dimensional positioning, still outputting high-precision horizontal coordinates. This effectively improves the system's availability and robustness when some base stations are blocked or malfunction, reducing overall positioning interruptions caused by individual base station loss of lock. Attached Figure Description

[0024] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a schematic diagram of a large-scale underwater multi-target acoustic positioning system in a dock provided in an embodiment of the present invention; Figure 2 This is a flowchart of the five-level multipath protection system provided in the embodiments of the present invention; Figure 3 This is a flowchart illustrating the acoustic localization method for large-scale underwater multi-target positioning in a dock provided in an embodiment of the present invention. Figure 4 This is a flowchart of the local TDOA autonomous positioning calculation process for dock piers provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of the structure of the electronic device provided in an embodiment of the present invention. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0026] The terms "first," "second," etc., used in the specification and claims of this invention are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of the invention can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and the number of objects is not limited; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0027] The acoustic positioning system for large-scale underwater multi-targets in a dock, the acoustic positioning method for large-scale underwater multi-targets in a dock, the electronic equipment, and the readable storage medium provided in the embodiments of the present invention will be described in detail below with reference to the accompanying drawings and through specific embodiments and application scenarios.

[0028] Among them, the large-scale underwater multi-target acoustic positioning system in the dock can be applied to the terminal, which can be executed by the hardware or software in the terminal.

[0029] The terminal includes, but is not limited to, portable communication devices such as mobile phones or tablets with touch-sensitive surfaces (e.g., touchscreen displays and / or touchpads). It should also be understood that, in some embodiments, the terminal may not be a portable communication device, but rather a desktop computer with touch-sensitive surfaces (e.g., touchscreen displays and / or touchpads).

[0030] The following embodiments describe a terminal including a display and a touch-sensitive surface. However, it should be understood that the terminal may include one or more other physical user interface devices such as a physical keyboard, mouse, and joystick.

[0031] The acoustic positioning system for large-scale underwater multi-targets in a dock provided in this embodiment of the invention can be implemented by an electronic device or a functional module or entity within an electronic device that can realize the acoustic positioning system for large-scale underwater multi-targets in a dock. The electronic devices mentioned in this embodiment of the invention include, but are not limited to, mobile phones, tablets, computers, cameras, and wearable devices. The following description uses an electronic device as the implementing entity to illustrate the acoustic positioning system for large-scale underwater multi-targets in a dock provided in this embodiment of the invention.

[0032] The present invention aims to solve the following technical problems existing in the underwater multi-target positioning in the dock: (1) Large-scale multi-target signal conflict leads to limited system capacity: When a large number of moving targets actively emit acoustic signals, the number of signal sources increases linearly with the number of targets. The signals in the limited space of the dock are superimposed and reflected, and the receiver cannot effectively separate the signals of each target. The system performance deteriorates sharply with the increase of the number of targets. (2) Low positioning accuracy in strong multipath environment: In the strong multipath environment of the dock, the actual positioning accuracy of the existing underwater acoustic positioning method degrades to the meter level, which cannot meet the centimeter-level high-precision positioning requirements required for the autonomous operation of underwater moving targets. (3) Positioning interruption caused by signal blockage: Conventional schemes install the acoustic terminal at a low position on the moving vehicle. The signal is easily blocked by the surrounding fixed dock piers, resulting in discontinuous and unreliable positioning. (4) The power consumption and hardware complexity of the moving vehicle increase linearly with the deployment scale: Conventional systems require each moving target to integrate acoustic transmission and reception circuits at the same time. When the number of targets increases to hundreds, the total power consumption and system complexity increase linearly, which is not conducive to long-term large-scale underwater deployment. (5) Insufficient engineering protection for underwater equipment: For moving targets that need to alternate between the two working conditions of dock flooding and drainage (such as self-propelled intelligent dock piers, which need to withstand huge pressure from the hull after drainage), the acoustic transducers installed on their tops are easily crushed under pressure; at the same time, pollutants from operations such as bottom painting may adhere to the radiating surface of the transducers, affecting acoustic performance. Existing positioning solutions lack engineering protection designs for such working condition switching.

[0033] Figure 1This is a schematic diagram of a large-scale underwater multi-target acoustic positioning system provided in an embodiment of the present invention, as shown below. Figure 1 As shown, 1 is the shore-based central control room, 2 is the acoustic transmission base station fixed on the wall of the dock pool, 3 is the dock, 4 is the underwater moving target to be located, and 5 is the receiving terminal deployed on the target.

[0034] In some embodiments, the system includes an underwater moving target, a shore-based central control room, and at least three acoustic transmission base stations; The acoustic transmission base stations are deployed on high platforms pre-erected around the dock's perimeter. The installation height of the acoustic transmission base stations is higher than the highest point of all static obstacles within the dock. Each acoustic transmission base station transmits acoustic pulse signals sequentially according to a preset TDMA timing sequence.

[0035] For example, the number of acoustic transmission base stations is at least three, but to balance overall efficiency and complexity, four to six are preferred, and they are deployed on raised platforms pre-erected around the dock's perimeter. The installation height of the base stations is higher than the highest point of all static obstacles (such as fixed dock piers, other underwater facilities, etc.) within the dock, ensuring an unobstructed line-of-sight propagation path between the base stations and the receiving terminals on each moving target.

[0036] Each acoustic transmitting base station maintains clock synchronization with a wired synchronization line or a high-precision timing module (such as GPS / BeiDou), with a synchronization accuracy better than 1 microsecond. Each base station transmits acoustic pulse signals sequentially according to a preset TDMA timing sequence. To prevent misidentification of the signal source due to multipath propagation or clock drift, each base station uses a different modulation slope (i.e., modulation coefficient) for its transmitted LFM (Linear Frequency Modulation) signal. This forms a unique "signal fingerprint" for the base station. Typical signal parameters are: bandwidth 5kHz, pulse width 10ms, and center frequency 20~30kHz. The interval between adjacent transmissions is greater than the maximum propagation delay (e.g., 50ms) to avoid time slot crosstalk. Specific values ​​are calibrated based on the actual dock size and water sound speed.

[0037] Optionally, if wired synchronization cannot be deployed, each base station can be independently configured with a high-precision temperature-controlled crystal oscillator, and clock calibration can be performed periodically via radio or underwater acoustics.

[0038] The system adopts a one-way broadcast communication mode, where the base station only transmits signals and does not need to receive any return signals from moving targets. Regardless of the number of moving targets in the dock, the number of transmitting base stations remains constant (only 3 to 6), ensuring a clean and controllable signal environment.

[0039] The underwater moving target includes an acoustic receiving terminal, a retractable protective structure for receiving transducers, underwater acoustic communication equipment, a sealed protective chamber, and a local calculation unit. The underwater moving target receives acoustic pulse signals from various acoustic transmitting base stations through the local calculation unit, performs hierarchical verification and TDOA calculation, outputs its own real-time coordinates and status data, and reports the real-time coordinates and status data to the shore-based central control room through the underwater acoustic communication link. It should be noted that the "underwater moving target" referred to in this invention includes, but is not limited to, self-propelled intelligent docking piers, bottom-sitting vehicles, underwater robots (ROV / AUV), underwater unmanned vehicles, underwater work platforms, and other carriers capable of underwater movement and requiring real-time positioning. The configurations of each moving target are as follows:

[0040] (1) Acoustic receiving terminal The acoustic receiving terminal is installed on the top or side of the moving target and must be retractable / foldable for storage so that the installation height of the receiving transducer is higher than the highest point of all static obstacles in the dock. The transducer's operating frequency is matched with the transmitting base station (20~30kHz), and the receiving sensitivity is not less than -180dB (typical value, the specific value is determined according to the transducer selection).

[0041] Each mobile target's receiver has a built-in matched filter bank, with each filter corresponding to a specific LFM slope of a base station. When a signal arrives, it is only considered a direct wave signal from that base station if its time-domain arrival time falls within a preset TDMA time slot and produces a significant correlation peak after passing through the filter with the corresponding slope; otherwise, it is considered crosstalk or a reflected wave and discarded. This dual verification mechanism ensures that each mobile target can accurately identify the signal source under all circumstances.

[0042] (2) Retractable protective structure for receiving transducer For mobile targets that require both underwater operation and dry parking (such as self-propelled intelligent dock piers, which need to withstand the pressure of the ship's hull after the dock is drained), the transducer is installed in a retractable sealed cavity. This protective design serves two purposes: firstly, to prevent crushing; when the target is under pressure (such as the top of the dock pier needing to withstand the enormous pressure of the ship's hull), the transducer automatically retracts into the cavity and does not protrude from the target's upper surface, thus avoiding damage; secondly, to prevent surface contamination; in situations where the target surface may come into contact with contaminants (such as paint sprayed on the ship's bottom), the retracted transducer is not exposed, preventing paint and other contaminants from adhering to the transducer's radiating surface and affecting acoustic performance.

[0043] During operation (underwater positioning), the protective cover opens, and the transducer extends from the cavity to receive signals. The extension and retraction of the cover and the opening of the cover are automatically controlled by the target main control board according to the operational status.

[0044] For underwater mobile targets that do not require pressure-bearing conditions (such as hovering underwater robots), this storage structure can be omitted, and a fixed installation method can be adopted.

[0045] Alternatively, for the transducer extension and retraction drive method, alternative solutions such as hydraulic drive, screw motor, or spring reset plus electromagnet attraction can be adopted.

[0046] (3) Underwater acoustic communication equipment When a moving target operates underwater, data transmission between it and the shore-based base is achieved via underwater acoustic communication (radio waves such as 4G / 5G and Wi-Fi are severely attenuated in water and are unsuitable for use). Underwater acoustic communication transducers are installed on the target's sidewalls to transmit its calculated coordinates and status information to the underwater acoustic communication base station in the shore-based control room via an underwater acoustic link. The underwater acoustic communication transducers can also be designed with a retractable and protective structure as needed.

[0047] (4) Sealed protective chamber The moving target has an independent sealed chamber with a protection level of no less than IP68. The chamber integrates a local computing unit, power management module, storage unit, motor drive circuit, etc. All external cables (including receiving transducer signal lines, communication transducer cables, motor control lines, sensor lines, etc.) enter the sealed chamber through waterproof penetration joints to ensure overall watertightness.

[0048] (5) Local solution unit The local calculation unit receives signals from multiple acoustic transmission base stations, performs signal acquisition, matched filter bank identification, narrow window truncation, matched filtering, waveform morphology discrimination, TDOA calculation and other processing, outputs the real-time coordinates of the moving target, and reports them to the shore-based central control room through the underwater acoustic communication link.

[0049] In some embodiments, the underwater moving target further includes a first receiver and a second receiver. The first receiver and the second receiver are arranged at a predetermined distance from each other along the longitudinal centerline on the top of the underwater moving target. The first receiver and the second receiver independently receive acoustic pulse signals from each acoustic transmitting base station and calculate their own coordinates. The coordinates of the first receiver and the second receiver are used to solve the heading angle of the underwater moving target.

[0050] Optionally, if the underwater moving target needs to obtain its heading angle in real time, two acoustic receivers (with precisely calibrated spacing) can be installed on the top of the target along its longitudinal centerline. Each receiver independently receives signals from its respective base station and calculates its coordinates, using the difference between the two coordinates to calculate the heading angle.

[0051] in, and These are the planar coordinates obtained from the solutions of the two receivers. This is the heading angle.

[0052] If the receiver adopts a retractable design, the actual stability accuracy of the baseline length will be slightly lower compared to a fixed, rigid installation, due to factors such as the reset accuracy of the retraction mechanism and minor positional deviations after the transducer extends. In scenarios where heading information is not required, only one receiver needs to be installed.

[0053] The shore-based central control room receives real-time coordinates and status data of the underwater moving target, performs global monitoring, path planning and task scheduling of the underwater moving target, and issues operation instructions to the underwater moving target.

[0054] As is easily understood, the shore-based control room receives real-time coordinates and status data reported by each of the respective docking piers, performs global monitoring, path planning, and task scheduling, and can issue operational instructions (such as target locations and travel paths) to the docking piers. The shore-based system does not participate in real-time positioning calculations, but only performs data aggregation and monitoring, thereby reducing its reliance on the real-time performance of the communication link.

[0055] In one implementation, the root cause of underwater acoustic multipath interference within the dock lies in the fact that the reinforced concrete pool walls, rigid bottom surface, and hundreds of fixed dock piers of varying heights surrounding the dock constitute a closed, highly reflective space. After multiple reflections by the pool walls, bottom surface, and dock piers within this confined space, sound waves form multiple coherent components at the receiving end that overlap with or are adjacent to the direct wave in the time domain, resulting in severe distortion of the received waveform. Figure 2 This is a flowchart of the five-level multipath protection system provided in the embodiments of the present invention, as follows: Figure 2 As shown, this system adopts a five-level progressive anti-multipath interference strategy. Each level of protection plays a role at different levels, eliminating multipath interference step by step, and jointly ensuring the accuracy and reliability of direct wave delay extraction.

[0056] (1) Level 1: Physical layer - spatial isolation and line-of-sight propagation protection The acoustic transmitting base station is fixedly deployed on a high platform pre-erected around the dock's perimeter, with its installation height exceeding the highest point of all static obstacles within the dock (such as fixed dock piers, other underwater facilities, etc.). The acoustic receiving terminals on each moving target are also raised to a position higher than all static obstacles via a telescopic mechanism. An unobstructed line-of-sight propagation path is formed between the transmitting and receiving ends.

[0057] The core physical significance of this measure lies in ensuring that the direct wave is the first component to reach the receiver, while significantly increasing the path length of primary and secondary reflected waves from the pool walls and bottom. Let the propagation distance of the direct wave be... The total propagation distance of a certain reflection path is The time difference between their arrival times is

[0058] in, The speed of sound in water is approximately 1500 m / s.

[0059] By raising the height of the transmitter and receiver, the difference between the reflected path and the direct path increases significantly, causing at least part of the reflected wave's arrival time to exceed the receiving pulse window of the direct wave. (The specific time threshold can be adjusted according to the actual situation), thereby reducing the number of multipath components entering the subsequent processing stage from a physical perspective.

[0060] (2) Second level: Signal layer - Differentiated LFM slope coding and matched filter identification In some embodiments, receiving acoustic pulse signals from various acoustic transmitting base stations, performing hierarchical verification and TDOA calculation, and outputting the real-time coordinates and status data of the underwater moving target itself includes: The system receives acoustic pulse signals from various acoustic transmission base stations, sends the acoustic pulse signals to a matched filter bank, and verifies the acoustic pulse signals based on a dual verification mechanism to obtain the acoustic pulse signals that pass the verification. In some embodiments, sending the acoustic pulse signal to a matched filter bank and verifying the acoustic pulse signal based on a dual verification mechanism to obtain a verified acoustic pulse signal includes: The acoustic pulse signal is subjected to adaptive threshold detection using a constant false alarm rate detector to locate the pulse start time and obtain the received signal; The received signal is sent to the matched filter bank, the filter number that generates the maximum correlation peak is identified, the base station to which the signal belongs is determined, and double verification is performed in combination with the TDMA time slot to obtain the acoustic pulse signal that passes the verification.

[0061] Each transmitting base station uses a linear frequency modulated signal with a different slope as its unique "signal fingerprint." Let the... The LFM signal transmitted by each base station can be represented as:

[0062] in, For signal amplitude, This is the pulse width (typically 10ms). The center frequency is 20~30kHz. For the first Frequency modulation slope (i.e., frequency change rate, unit Hz / s) of each base station. This is a rectangular function. The frequency modulation slope of each base station. They are all different, forming unique waveform characteristics.

[0063] The moving target receiver has a built-in matched filter bank, with each filter matched to a specific slope. A match is found. The impulse response of the matched filter is the time-reversed conjugate of the transmitted signal:

[0064] When the received signal passes through the matched filter When, only when the input signal contains and A significant correlation peak is only generated when there is a matching LFM component. The peak position of the matched filter output corresponds to the arrival time of the signal, and the peak amplitude reflects the signal strength. By identifying the filter number that generates the maximum correlation peak, the source base station of the signal can be uniquely determined.

[0065] The core advantage of this level is that even if the signals from different base stations partially overlap in the time domain due to propagation delay, or if the reflected wave falls into the TDMA time slot of other base stations, the receiver can still accurately separate each signal through waveform characteristics (frequency modulation slope), fundamentally avoiding the calculation error caused by signal "source misidentification".

[0066] Alternatively, in addition to the "TDMA + differentiated LFM slope" combination, the following alternative solutions can be used for multiple access methods: ① Pure CDMA: Each base station is assigned an orthogonal spreading code, allowing simultaneous transmission at the same frequency. Moving targets identify the signal source through code division; ② Waveform parameter coding: Different pulse widths or different coding sequences are assigned to each base station, and the receiver identifies the source by measuring signal parameters; ③ Encoded modulation with embedded base station ID: A binary base station ID sequence (such as BPSK modulation) is modulated into the LFM signal, and the receiver directly reads the base station number after demodulation. These three methods can be combined as needed.

[0067] (3) Third level: Time domain layer - narrow window interception and elimination of time-delayed reflected waves The acoustic pulse signals that pass the verification are subjected to narrow window truncation, matched filtering, and waveform morphology discrimination to obtain the acoustic pulse signals that pass the discrimination. In some embodiments, the step of performing narrow window truncation, matched filtering, and waveform morphology discrimination on the verified acoustic pulse signal to obtain the discriminated acoustic pulse signal includes: The first zero-crossing point detected is used as the starting point for extracting a window of signal within a preset time range from the acoustic pulse signal that has passed the verification. Matched filtering is performed on the captured window signal to obtain the time delay estimation signal; The kurtosis and skewness coefficients of the time delay estimation signal are calculated, and the effective direct waves are screened to obtain the acoustic pulse signals that are judged to pass.

[0068] It is easy to understand that the local solution unit takes the first zero-crossing point detected by the adaptive threshold (the zero-crossing point of the rising edge of the matched filter output envelope) as the pulse start time. Only extract to Data within the time window undergoes subsequent matching and filtering processing. Window width The preset time is 3ms (which can be adjusted according to the actual dock size and the speed of sound in the water), corresponding to a propagation distance of about 4.5 meters in water.

[0069] The selection of this window width is based on the fact that the difference in propagation distance between the reflection path and the direct path between the nearest major reflector (fixed dock pier, pool wall, etc.) and the receiving terminal is typically greater than 4.5 meters, corresponding to a reflection wave arrival time difference greater than 3 ms. Therefore, The window ensures that the direct wave is completely captured while excluding most primary and secondary reflected waves with an arrival time lag of more than 3ms.

[0070] Let the arrival time of the direct wave be... The arrival time of a certain reflected wave is The window capture condition is: This measure achieves the initial filtering of most long-delay multipath components in the time domain with extremely low computational cost.

[0071] (4) Fourth level: Feature layer - Waveform morphology statistical discrimination Morphological statistical discrimination is performed on the output waveform of the matched filter within the captured window. Under ideal conditions (direct wave dominance, no multipath interference), the output of the matched filter should present a single symmetrical main peak, and its waveform is approximately Gaussian. However, when the reflected wave and the direct wave are superimposed within the window, the output waveform will be distorted—possibly exhibiting characteristics such as multiple peaks, asymmetry, and kurtosis deviating from the normal distribution.

[0072] Calculate the matched filter output sequence within the truncated window kurtosis coefficient Skewing coefficient : in, This represents the number of sampling points within the window. This is the sequence mean.

[0073] Kurtosis coefficient of an ideal single-peak Gaussian waveform skewness coefficient (Symmetrical distribution). The discrimination criteria are as follows:

[0074] like or This indicates that the waveform kurtosis deviates from the Gaussian distribution—the former indicates that the waveform is too flat (multiple peaks superimposed, causing energy dispersion), and the latter indicates that the waveform is too sharp (there may be narrowband interference or abnormal peaks), which is judged as severe distortion; like This indicates that the waveform is severely asymmetrical (the superposition of the reflected wave and the direct wave destroys the symmetry of the waveform), and is judged to be severely distorted; Only when and If the signal is valid, it is considered a direct wave and its time delay estimate is retained for subsequent calculations; otherwise, the data is discarded.

[0075] This level of measure uses statistical discrimination to eliminate the dominant reflected wave signal with severe waveform distortion, ensuring that the time delay estimate entering the final calculation stage has high reliability. The upper and lower thresholds of the kurtosis coefficient and the threshold of the skewness coefficient mentioned above can be fine-tuned according to the actual situation.

[0076] (5) Level 5: Data Layer - Delay Consistency Check and Kalman Filter Smoothing Based on the acoustic pulse signal that has passed the discrimination test, the effective TDOA equations are calculated and the position is solved to obtain a preliminary estimate of the underwater moving target. In some embodiments, the step of calculating the effective TDOA equations and solving the position based on the determined acoustic pulse signal to obtain a preliminary estimate of the underwater moving target includes: Based on the acoustic pulse signals that have passed the discrimination, the number of effective base stations is obtained, an effective TDOA equation set is established, and the relationship between the number of effective TDOA equations and the positioning dimension is determined. If the number of effective TDOA equations is less than the positioning dimension, the current solution is abandoned. It is then determined whether the timeliness of the positioning estimate at the previous moment meets the preset time threshold. If it does, the positioning estimate at the previous moment is used as the preliminary estimate of the underwater moving target. If it does not meet the threshold, the positioning loss is reported. If the number of effective TDOA equations equals the positioning dimension, the effective TDOA equations are solved using the first weighted least squares method to obtain a preliminary estimate of the underwater moving target. If the number of effective TDOA equations is greater than the positioning dimension, the effective TDOA equations are solved using the quadratic weighted least squares method to obtain a preliminary estimate of the underwater moving target.

[0077] The calculation unit performs consistency verification and filtering on the latency data from multiple base stations based on positioning geometric constraints. Let the number of valid base stations that have passed the first four levels of filtering be... Positioning dimension is (in 3D mode) In two-dimensional mode Then the number of effective TDOA equations is: Based on the relationship between the number of equations and the number of unknowns, the system automatically classifies the following three cases:

[0078] Scenario 1: (Undetermined) When the number of independent equations provided by effective base stations is less than the number of unknowns to be solved, the positioning equation set is underdetermined and a unique solution cannot be obtained. The system abandons the position calculation for the current period, uses the effective positioning estimate from the previous moment, and reports a "insufficient number of effective base stations, reduced accuracy" status flag to the shore-based control room via the underwater acoustic communication link; if the underdetermined state continues for more than a preset time limit... If the location lock is lost (typically 5 seconds), a location lock loss status will be reported. Once the number of valid base stations recovers to the required level in subsequent cycles, the normal solution process will automatically resume.

[0079] Scenario 2: (Appropriate) When the number of independent equations provided by the effective base stations is exactly equal to the number of unknowns to be solved, the system of equations is well-determined and has a unique solution, but there are no redundant observations, making statistical delay consistency verification impossible. The system directly substitutes the delay values ​​of all effective base stations into the TDOA equation system to solve, skipping the consistency verification step.

[0080] Scenario 3: (Over-order) When the number of independent equations provided by the effective base stations exceeds the number of unknowns, the system of equations becomes overdetermined, resulting in redundant observations. In this case, the statistically optimal estimate can be obtained through least squares solving, and delay consistency verification can be performed.

[0081] Substitute any set of time delay values ​​into the TDOA equations to obtain the candidate positions. Then, calculate the expected latency of each base station: If the measured latency of a certain base station Compared with expected delay The deviation exceeds the preset threshold ( The typical value is 0.1ms, corresponding to a distance error of approximately 0.15 meters, that is: If the delay value is deemed an outlier and removed, the remaining base stations will be used to recalculate the problem. If the equations are still overdetermined or adequately determined after removal, the problem will be resolved. ), continue solving; if after elimination it becomes underdetermined ( If so, then proceed to case one.

[0082] Regardless of the system's state, for every period in which a position result is successfully calculated, the continuously calculated position sequence is smoothed using Kalman filtering to suppress random measurement noise. In three-dimensional mode, let the state vector be:

[0083] in For the goal The three-dimensional position at a given moment. For the corresponding three-dimensional velocity, the state vector in the two-dimensional mode is reduced to = .

[0084] The system state equation and observation equation are as follows: in, This is the state transition matrix (using a uniform motion model). For the observation matrix, and These are the process noise covariance matrix and the observation noise covariance matrix, respectively. Kalman filtering, through two iterative steps of prediction and update, suppresses measurement random noise while maintaining the ability to track the target's motion state, ultimately outputting continuous, stable, and smooth centimeter-level positioning results (output in 3D mode). Output in 2D mode ,depth (Measured independently by the sensor).

[0085] The protection measures at each level are not simply superimposed, but rather progressively advanced and selectively applied at each stage: the physical layer reduces the chance of multipath interference, the signal layer ensures the signal source is identifiable, the time-domain layer eliminates reflected waves with long delays, the feature layer identifies and eliminates residual multipath interference caused by waveform distortion, and the data layer eliminates outliers through geometric consistency checks and timing filtering. Multipath interference that was not completely eliminated in the previous stage is gradually identified and eliminated in subsequent stages, ultimately ensuring that the delay values ​​entering the TDOA solution are all high-confidence direct wave delays.

[0086] In this embodiment, a dual identification mechanism of "TDMA time slot division + signal waveform feature encoding" is adopted: each transmitting base station transmits signals within a preset TDMA time slot, and the signals transmitted by each base station use linear frequency modulated signals with different slopes as unique "acoustic ID cards". The mobile target receiver initially determines the signal source by time slot assignment, and then performs secondary confirmation by waveform features, fundamentally reducing the calculation errors caused by signal "misidentification". At the same time, a five-level anti-multipath hierarchical protection system of "physical layer – signal layer – time domain layer – feature layer – data layer" is constructed to eliminate multipath interference step by step from physical layout, signal identification, time domain interception, waveform discrimination to data verification. In addition, considering the characteristics of underwater mobile targets that need to take into account various working conditions such as underwater operation and dry parking, the acoustic receiving transducer, communication equipment and other components are designed with retractable protection to reduce the signal identification error rate of multiple transmitting base stations and adapt to the engineering protection requirements under different working conditions.

[0087] This invention also provides a method for acoustic localization of large-scale underwater multi-target targets within a dock, such as... Figure 3 As shown, the acoustic localization method for large-scale underwater multi-target positioning in the dock includes steps 310, 320, and 330.

[0088] Step 310: Transmit acoustic pulse signals sequentially through the acoustic transmission base station according to the preset TDMA timing sequence. The acoustic transmission base station is deployed on a high platform pre-erected around the pool wall of the dock. The installation height of the acoustic transmission base station is higher than the highest point of all static obstacles in the dock. Step 320: Receive acoustic pulse signals from various acoustic transmission base stations through the local calculation unit, perform hierarchical verification and TDOA calculation, output the real-time coordinates and status data of the underwater moving target, and report the real-time coordinates and status data to the shore-based central control room through the underwater acoustic communication link. The underwater moving target includes an acoustic receiving terminal, a retractable protective structure for receiving transducers, underwater acoustic communication equipment, a sealed protective chamber, and a local calculation unit. Step 330: Receive the real-time coordinates and status data of the underwater moving target, perform global monitoring, path planning and task scheduling of the underwater moving target through the shore-based central control room, and issue operation instructions to the underwater moving target.

[0089] Figure 4 The flowchart of the local TDOA autonomous positioning calculation for dock piers provided in this embodiment of the invention is as follows: Figure 4 As shown, taking four base stations as an example, the location of a moving target is calculated using the following method: (1) First step: Signal transmission The coordinates of the four acoustic transmission base stations deployed on the high platform of the pool wall are known, respectively. to Acoustic pulses are transmitted sequentially according to a preset TDMA timing sequence. The slope of the LFM signal transmitted by each base station is different. This creates a unique signal fingerprint. The interval between adjacent transmissions is greater than the maximum propagation delay (e.g., 50ms) to avoid signal crosstalk.

[0090] (2) Second step: Signal reception and preprocessing The receiving terminals on each mobile target sequentially receive signals from each base station and independently perform the following operations for each signal: Adaptive threshold detection: A constant false alarm rate detector is used to locate the pulse start time. The detection threshold is adaptively adjusted based on the ambient noise power. Matched filter bank identification: The received signal is passed through a set of matched filters (each filter is matched separately). The filter number that generates the maximum correlation peak is identified, the base station to which the signal belongs is determined, and dual verification is performed in conjunction with the TDMA time slot. Narrow window truncation: Starting from the first detected zero crossing, truncation is performed. The window data will be processed subsequently; Matched filtering: Perform matched filtering on the signal within the truncated window to obtain a high-precision time delay estimate; Waveform morphology identification: Calculation of kurtosis coefficient Skewing coefficient , and filter out the effective direct waves.

[0091] After the above preprocessing, the effective arrival time estimates of each base station signal are obtained. .

[0092] (3) Third step: TDOA calculation and location solution Upon proceeding to this step, first determine the positioning dimensions. If the target depth Given (e.g., a base-mounted carrier), then The unknown quantity is the horizontal coordinate. ;otherwise The unknown quantity is a three-dimensional coordinate. Let the number of effective base stations be... The number of effective TDOA equations is Based on the relationship between the number of equations and the number of unknowns, the following three cases can be distinguished:

[0093] Scenario 1: (Undetermined) The number of independent equations is less than the number of unknowns, the system of location equations is underdetermined, and a unique solution cannot be obtained. The system abandons the current cycle's solution and uses the valid coordinates from the previous time step, resulting in reduced reporting accuracy.

[0094] Scenario 2: (Appropriate) The number of independent equations is exactly equal to the number of unknowns, the system of equations is well-determined, and has a unique solution. Taking base station 1 as the reference base station, calculate the arrival time difference between the other base stations and the reference base station:

[0095] The corresponding distance difference is: in, For target location To the The distance between each base station. Therefore, a system of hyperbolic equations is established:

[0096] Number of independent equations in a system of equations Equal to the unknown quantity A unique solution can be obtained by direct solution. Typical scenarios include:

[0097] 3D mode ( )and Solving 3 equations Two-dimensional mode ( )and Solving two equations Scenario 3: (Over-order) When the number of independent equations exceeds the number of unknowns, the system of equations is overdetermined, and there is no exact solution that satisfies all equations simultaneously. In this case, least squares is used to obtain the best estimate in the statistically optimal sense. The TDOA system of equations has the same form as in case two, but the number of equations... .

[0098] Typical scenarios include: 3D mode ( )and Solving more than 4 equations Two-dimensional mode ( )and Solving more than 3 equations Taking into account factors such as computing resources, real-time performance, and accuracy, the local solution unit adopts a closed-form solution similar to the Chan algorithm as the solution scheme. This algorithm transforms the nonlinear TDOA equation system into a linear equation system through one or two weighted least squares operations, eliminating the need for iteration and resulting in high computational efficiency. The algorithm's output characteristics differ between well-determined and over-determined cases.

[0099] Appropriate circumstances ( The system of equations has a unique exact solution. The Chan algorithm can directly give the closed-form expression of this unique solution by a single weighted least squares operation. The output is an analytical solution that exactly satisfies all the equations, without the need for iteration.

[0100] Additional explanation: Under well-posed conditions, a second weighted least squares operation can also be performed. The purpose of the second weighted least squares operation is not to solve the problem (because the equation is already well-posed), but to perform consistency checks and normalization on the exact solution at the geometric constraint level, ensuring that the output strictly satisfies the condition. Geometric constraints ensure the self-consistency of the solution in a physical sense.

[0101] Over-determined situation ( The system of equations does not have an exact solution that satisfies all equations simultaneously. Chan's algorithm handles this by: first, using weighted least squares to obtain an initial closed-form solution (i.e., the statistically optimal estimate with the minimum sum of squared residuals); second, using weighted least squares to utilize the constraints between unknowns (in three-dimensional mode...). In two-dimensional mode, and The initial estimate is further optimized, and the final output is the optimal closed-form solution in the least squares sense, rather than an iterative approximation of some ideal exact solution. Redundant observations naturally suppress the influence of measurement noise in this process through the statistical averaging effect of least squares.

[0102] It should be noted that the solution obtained by quadratic weighted least squares is more accurate than the solution obtained by single weighted least squares.

[0103] In some embodiments, the step of solving the effective TDOA equations using the quadratic weighted least squares method to obtain a preliminary estimate of the underwater moving target includes: The distance from the underwater moving target to the reference base station is obtained as an auxiliary variable; Transform the effective TDOA equation system into a pseudo-linear equation system based on auxiliary variables; The pseudo-linear equations are transformed into matrix form and solved to obtain the first preliminary estimate. Calculate the error value of the first preliminary estimate, construct the observation vector and design matrix based on the error value, and solve to obtain the preliminary estimate of the underwater moving target.

[0104] First weighted least squares (initial estimate) In three-dimensional mode ( Introducing auxiliary variables (Distance from the target to the reference base station), transforming the original nonlinear equation into one concerning... The pseudo-linear system of equations: Write in matrix form ,in The first weighted least squares result is... Initial estimate:

[0105] in, This is the covariance matrix of the TDOA measurements.

[0106] Second weighted least squares (constrained optimization) The first weighted least squares result The components are estimated independently, which does not satisfy the condition that each component is independent. This inherent constraint (i.e.) When the reference base station is located at the origin; generally speaking, The purpose of the second weighted least squares is to refine the estimate under this constraint.

[0107] Construct about the target location The equation is given. Let the error of the first WLS estimation be... Its covariance matrix is:

[0108] use Constraints between components: Expand and rearrange into a linear form with respect to position coordinates. Construct a new observation vector by taking the squares or cross terms of each component in the first WLS estimation vector. and design matrix ,make:

[0109] in, The target location is to be determined. The covariance matrix is ​​the residual vector after the first estimation error undergoes a nonlinear transformation. can be The solution is approximated by a first-order Taylor expansion. The second weighted least squares solution is:

[0110] This yields the final closed-form solution for the target location.

[0111] In terms of the solution algorithm, TDOA can be solved using Chan's algorithm, Taylor series expansion method or particle filtering, etc., and can be dynamically switched according to different signal-to-noise ratios.

[0112] (4) Fourth step: Delay consistency check and Kalman filtering smoothing After the algorithm calculates a preliminary estimate of the target location, the result is sent to the data layer processing flow. The data layer processing performs the following two operations in sequence:

[0113] Delay consistency verification. The expected delay of each base station signal is calculated using the preliminary positioning results and compared with the measured delay obtained from the front end. Abnormal observations with deviations exceeding a preset threshold are eliminated, and the target position is recalculated using the remaining base station data to ensure that all delay observations participating in the final positioning calculation meet the geometric consistency constraints.

[0114] Kalman filtering smoothing. The continuous positioning result sequence after passing the consistency check is smoothed using Kalman filtering to suppress random measurement noise and output continuous, stable, and smooth centimeter-level positioning results.

[0115] (5) Fifth step: Data reporting After data layer verification and filtering smoothing, the moving target transmits its final positioning coordinates to the shore-based control room via an underwater acoustic communication link, while simultaneously storing the trajectory data locally for future tracking. Each target calculates and reports independently; the shore-based control room only performs data aggregation and global monitoring, and does not participate in real-time positioning calculations.

[0116] It should be noted that all underwater moving targets operate in passive receiving mode, meaning they only receive acoustic signals and do not actively transmit any acoustic signals. Regardless of the number of moving targets operating simultaneously within the dock, the number of acoustic transmission base stations remains constant (only 3-6), ensuring a clean and controllable signal environment and fundamentally avoiding signal collisions in large-scale, multi-target scenarios. Theoretically, this system can support any number of moving targets operating simultaneously within the same dock without affecting their positioning accuracy.

[0117] The acoustic localization method for large-scale underwater multi-target positioning within a dock, provided in this invention, changes the signal flow design of conventional underwater acoustic positioning systems. Acoustic transmitting base stations are fixedly deployed on elevated platforms around the dock walls (only 3-6 are needed), while acoustic receiving terminals are installed on top of various underwater mobile targets (such as self-propelled dock piers, underwater robots, etc.). After receiving acoustic signals from multiple base stations, each mobile target autonomously calculates its own coordinates locally using the time difference of arrival principle, without needing two-way communication with the base stations or relying on real-time calculations from shore-based systems. The fundamental difference between this scheme and the existing "mobile carrier transmitting, fixed base station receiving" scheme is that the latter is suitable for a small number of mobile targets (a few to a dozen), where each target actively transmits signals and the base station passively receives them; this invention is suitable for a large number of mobile targets (dozens to hundreds), where a few fixed base stations uniformly transmit signals, and each target passively receives and autonomously calculates its coordinates. The former's number of signal sources increases linearly with the number of targets, while the latter's number of signal sources is fixed and independent of the number of targets, thus offering a fundamental advantage in large-scale multi-target scenarios.

[0118] In some embodiments, such as Figure 5 As shown, this embodiment of the invention also provides an electronic device 500, including a processor 501, a memory 502, and a computer program stored in the memory 502 and executable on the processor 501. When the program is executed by the processor 501, it implements the various processes of the above-described embodiment of the acoustic positioning system for large-scale underwater multi-targets in a dock, and achieves the same technical effect. To avoid repetition, it will not be described again here.

[0119] It should be noted that the electronic devices in the embodiments of the present invention include the mobile electronic devices and non-mobile electronic devices described above.

[0120] This invention also provides a non-transitory computer-readable storage medium storing a computer program. When executed by a processor, the computer program implements the various processes of the above-described embodiment of the large-scale underwater multi-target acoustic positioning system in a dock, and achieves the same technical effect. To avoid repetition, it will not be described again here.

[0121] The processor is the processor in the electronic device described in the above embodiments. The readable storage medium includes computer-readable storage media, such as computer read-only memory (ROM), random access memory (RAM), magnetic disk, or optical disk.

[0122] This invention also provides a computer program product, including a computer program that, when executed by a processor, implements the aforementioned large-scale underwater multi-target acoustic positioning system within a dock.

[0123] The processor is the processor in the electronic device described in the above embodiments. The readable storage medium includes computer-readable storage media, such as computer read-only memory (ROM), random access memory (RAM), magnetic disk, or optical disk.

[0124] This invention also provides a chip, which includes a processor and a communication interface. The communication interface and the processor are coupled. The processor is used to run programs or instructions to implement the various processes of the above-described embodiment of the large-scale underwater multi-target acoustic positioning system in the dock, and can achieve the same technical effect. To avoid repetition, it will not be described again here.

[0125] It should be understood that the chip mentioned in the embodiments of the present invention may also be referred to as a device-level chip, device chip, chip device, or on-chip device chip, etc.

[0126] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Furthermore, it should be noted that the scope of the methods and apparatuses in the embodiments of the present invention is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

[0127] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods of the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a computer software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) and includes several instructions to cause a terminal (which may be a mobile phone, computer, server, or network device, etc.) to execute the large-scale underwater multi-target acoustic positioning system in the dock of the various embodiments of the present invention.

[0128] In the description of this invention, "first feature" and "second feature" may include one or more of the features.

[0129] In the description of this invention, "a plurality of" means two or more.

[0130] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of the present invention.

[0131] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0132] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A large-scale underwater multi-target acoustic positioning system for use in a dry dock, characterized in that, The system includes an underwater moving target, a shore-based central control room, and at least three acoustic transmission base stations; The acoustic transmission base stations are deployed on high platforms pre-erected around the dock's pool walls. The installation height of the acoustic transmission base stations is higher than the highest point of all static obstacles in the dock. Each acoustic transmission base station transmits acoustic pulse signals sequentially according to a preset TDMA timing sequence. The underwater moving target includes an acoustic receiving terminal, a retractable protective structure for receiving transducers, underwater acoustic communication equipment, a sealed protective chamber, and a local calculation unit. The underwater moving target receives acoustic pulse signals from various acoustic transmitting base stations through the local calculation unit, performs hierarchical verification and TDOA calculation, outputs its own real-time coordinates and status data, and reports the real-time coordinates and status data to the shore-based central control room through the underwater acoustic communication link. The shore-based central control room receives real-time coordinates and status data of the underwater moving target, performs global monitoring, path planning and task scheduling of the underwater moving target, and issues operation instructions to the underwater moving target.

2. The large-scale underwater multi-target acoustic positioning system in a dock according to claim 1, characterized in that, The process of receiving acoustic pulse signals from various acoustic transmitting base stations, performing hierarchical verification and TDOA calculation, and outputting the real-time coordinates and status data of the underwater moving target includes: The system receives acoustic pulse signals from various acoustic transmission base stations, sends the acoustic pulse signals to a matched filter bank, and verifies the acoustic pulse signals based on a dual verification mechanism to obtain the acoustic pulse signals that pass the verification. The acoustic pulse signals that pass the verification are subjected to narrow window truncation, matched filtering, and waveform morphology discrimination to obtain the acoustic pulse signals that pass the discrimination. Based on the acoustic pulse signal that has passed the discrimination test, the effective TDOA equations are calculated and the position is solved to obtain a preliminary estimate of the underwater moving target. If the number of effective TDOA equations is greater than the positioning dimension, the initial estimate of the underwater moving target is subjected to time delay consistency verification and Kalman filtering smoothing, and the real-time coordinates and status data of the underwater moving target are output. If the effective TDOA equation number equals the positioning dimension, no time delay consistency check is performed. The initial estimate of the underwater moving target is smoothed by Kalman filtering, and the real-time coordinates and status data of the underwater moving target are output. If the number of valid TDOA equations is less than the positioning dimension, determine whether there is a preliminary estimate of the underwater moving target. If there is, output the preliminary estimate of the underwater moving target; if there is no, report positioning loss.

3. The large-scale underwater multi-target acoustic positioning system in a dock according to claim 2, characterized in that, The process of sending the acoustic pulse signal to the matched filter bank and verifying the acoustic pulse signal based on a dual verification mechanism to obtain a verified acoustic pulse signal includes: The acoustic pulse signal is subjected to adaptive threshold detection using a constant false alarm rate detector to locate the pulse start time and obtain the received signal; The received signal is sent to the matched filter bank, the filter number that generates the maximum correlation peak is identified, the base station to which the signal belongs is determined, and double verification is performed in combination with the TDMA time slot to obtain the acoustic pulse signal that passes the verification.

4. The large-scale underwater multi-target acoustic positioning system in a dock according to claim 2, characterized in that, The process of performing narrow-window truncation, matched filtering, and waveform morphology discrimination on the verified acoustic pulse signal to obtain the approved acoustic pulse signal includes: The first zero-crossing point detected is used as the starting point for extracting a window of signal within a preset time range from the acoustic pulse signal that has passed the verification. Matched filtering is performed on the captured window signal to obtain the time delay estimation signal; The kurtosis and skewness coefficients of the time delay estimation signal are calculated, and the effective direct waves are screened to obtain the acoustic pulse signals that are judged to pass.

5. The large-scale underwater multi-target acoustic positioning system in a dock according to claim 2, characterized in that, The calculation of effective TDOA equations and position solving based on the discriminated acoustic pulse signals yields a preliminary estimate of the underwater moving target, including: Based on the acoustic pulse signals that have passed the discrimination, the number of effective base stations is obtained, an effective TDOA equation set is established, and the relationship between the number of effective TDOA equations and the positioning dimension is determined. If the number of effective TDOA equations is less than the positioning dimension, the current solution is abandoned. It is then determined whether the timeliness of the positioning estimate at the previous moment meets the preset time threshold. If it does, the positioning estimate at the previous moment is used as the preliminary estimate of the underwater moving target. If it does not meet the threshold, the positioning loss is reported. If the number of effective TDOA equations equals the positioning dimension, the effective TDOA equations are solved using the first weighted least squares method to obtain a preliminary estimate of the underwater moving target. If the number of effective TDOA equations is greater than the positioning dimension, the effective TDOA equations are solved using the quadratic weighted least squares method to obtain a preliminary estimate of the underwater moving target.

6. The large-scale underwater multi-target acoustic positioning system in a dock according to claim 5, characterized in that, The preliminary estimate of the underwater moving target is obtained by solving the effective TDOA equations using the quadratic weighted least squares method, including: The distance from the underwater moving target to the reference base station is obtained as an auxiliary variable; Transform the effective TDOA equation system into a pseudo-linear equation system based on auxiliary variables; The pseudo-linear equations are transformed into matrix form and solved to obtain the first preliminary estimate. Calculate the error value of the first preliminary estimate, construct the observation vector and design matrix based on the error value, and solve to obtain the preliminary estimate of the underwater moving target.

7. The large-scale underwater multi-target acoustic positioning system in a dock according to claim 2, characterized in that, The initial estimate of the underwater moving target is subjected to time delay consistency verification and Kalman filtering smoothing, and the real-time coordinates and status data of the underwater moving target are output, including: The expected latency of each acoustic transmission base station is calculated based on the preliminary estimate of the underwater moving target. The result is compared with the measured latency. Abnormal observations with deviations exceeding a preset threshold are removed to obtain the remaining acoustic transmission base station data. The coordinates of the underwater moving target are recalculated based on the remaining acoustic transmission base station data until a continuous positioning result sequence after consistency verification is obtained. The continuous positioning result sequence is smoothed by Kalman filtering to suppress random noise in the measurement and output the real-time coordinates and status data of the underwater moving target.

8. The large-scale underwater multi-target acoustic positioning system in a dock according to claim 1, characterized in that, The underwater moving target also includes a first receiver and a second receiver. The first receiver and the second receiver are arranged at a predetermined distance from each other along the longitudinal centerline on the top of the underwater moving target. The first receiver and the second receiver independently receive the acoustic pulse signals from each acoustic transmitting base station and calculate their own coordinates. The coordinates of the first receiver and the second receiver are used to solve the heading angle of the underwater moving target.

9. A method for acoustic localization of large-scale underwater multiple targets within a dock, implemented using the acoustic localization system for large-scale underwater multiple targets within a dock as described in any one of claims 1 to 8, characterized in that, The method includes: Acoustic pulse signals are transmitted sequentially through an acoustic transmission base station according to a preset TDMA timing sequence. The acoustic transmission base station is deployed on a high platform pre-erected around the pool wall of the dock, and the installation height of the acoustic transmission base station is higher than the highest point of all static obstacles in the dock. The local calculation unit receives acoustic pulse signals from various acoustic transmission base stations, performs hierarchical verification and TDOA calculation, outputs the real-time coordinates and status data of the underwater moving target, and reports the real-time coordinates and status data to the shore-based central control room through the underwater acoustic communication link. The underwater moving target includes an acoustic receiving terminal, a retractable protective structure for receiving transducers, underwater acoustic communication equipment, a sealed protective chamber, and a local calculation unit. It receives real-time coordinates and status data of underwater moving targets, performs global monitoring, path planning and task scheduling of underwater moving targets through the shore-based central control room, and issues operation instructions to underwater moving targets.

10. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the acoustic localization method for large-scale underwater multi-target positioning in a dock as described in claim 9.

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