Centralized high-precision positioning system and method for underwater mobile carriers in a dock

Abstract

The application discloses a centralized high-precision positioning system of underwater mobile carriers in a dock, and belongs to the technical field of underwater acoustic positioning. The system comprises a shore-based calculation unit, at least one acoustic emission terminal and at least three acoustic receiving stations. The acoustic emission terminal is used for emitting acoustic pulse signals according to a preset TDMA time slot and a specific LFM slope. The acoustic receiving station is used for receiving the acoustic pulse signals and checking them through a double-checking mechanism. The acoustic pulse signals that pass the check are removed, and long-time delay reflected waves and waveform form statistics are discriminated to obtain the acoustic pulse signals that pass the discrimination. The acoustic pulse signals that pass the discrimination are forwarded to the shore-based calculation unit. The shore-based calculation unit is used for extracting the signal arrival time and signal source identification information of the acoustic pulse signals that pass the discrimination, and calculating the coordinates of each underwater mobile carrier based on the arrival time difference to obtain a positioning estimation value. The system can realize the centimeter-level positioning of underwater mobile carriers in a strong multipath environment of a large dock.

Description

Technical Field

[0001] This invention belongs to the field of underwater acoustic positioning technology, and particularly relates to a centralized high-precision positioning system and method for underwater mobile carriers in a dock. Background Technology

[0002] In shipbuilding and repair, the cost of docking time is extremely high. To reduce the waiting time in an empty dock and improve dock turnover efficiency, precise underwater operations need to be performed directly while the dock is flooded, such as intelligent handling and autonomous adjustment of dock piers, hull cleaning, and underwater welding. These operations place centimeter-level or even millimeter-level positioning accuracy requirements on underwater mobile carriers (such as bottom-mounted trolleys and hovering robots).

[0003] Existing underwater positioning technologies mainly include acoustic positioning methods such as ultra-short baseline, short baseline, and long baseline. Among them, the long baseline system constructs an underwater coordinate network by deploying multiple acoustic beacons around or at the bottom of the dock, possessing high potential for positioning accuracy. However, in practical applications in large dry docks, the above-mentioned conventional underwater acoustic positioning methods face a common and particularly prominent technical challenge—strong multipath interference. The dock is surrounded by reinforced concrete pool walls, with a rigid plane at the bottom, and hundreds of rigid dock piers of varying heights are densely distributed within the pool. These walls, bottom surfaces, and obstacles strongly reflect sound waves, creating complex multipath effects, especially "intra-pulse multipath"—the superposition of reflected waves and direct waves within a long pulse window, resulting in severe distortion and peak shift of the received waveform. Although conventional underwater acoustic positioning methods can achieve theoretical accuracy at the decimeter or even centimeter level in ideal water bodies, in the dock environment, due to the aforementioned strong intra-pulse multipath interference, the actual positioning accuracy often degrades to the meter level.

[0004] Furthermore, the positioning terminals of mobile carriers such as bottom-mounted trolleys are installed at low heights due to structural limitations, making their signals easily blocked by dock piers, further reducing the reliability and continuity of conventional positioning methods. Moreover, when multiple mobile carriers operate in parallel within the same dock, if the acoustic signals actively emitted by each carrier lack orderly coordination in the time and frequency domains, the signals will overlap and interfere with each other. The shore-based receiving base station will struggle to effectively separate the signal sources from the aliased signals, leading to chaotic positioning data or even system failure. It is worth noting that compared to the solution of converting hundreds of fixed dock piers into self-propelled intelligent dock piers, the active mobile carriers in this scenario are only a small number of transport trolleys, reducing the number of signal sources by an order of magnitude. This provides a natural convenience for orderly scheduling and centralized high-precision calculation. However, existing conventional underwater acoustic positioning methods suffer from severe degradation in positioning accuracy (typically reduced to the meter level) in the strong multipath environment of docks, failing to meet the centimeter-level positioning requirements for precise underwater operations. Summary of the Invention

[0005] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a centralized high-precision positioning system and method for underwater mobile vehicles in a dock. This system can achieve centimeter-level positioning of underwater mobile vehicles in the strong multipath environment of a large dock, providing a reliable positioning basis for multi-vehicle collaborative operations in the dock and has good adaptability.

[0006] In a first aspect, the present invention provides a centralized high-precision positioning system for an underwater mobile carrier in a dock, the system comprising a shore-based calculation unit, at least one acoustic transmitting terminal and at least three acoustic receiving base stations. The acoustic transmitting terminal is fixedly installed on the top of the underwater mobile carrier. The acoustic transmitting terminal is raised to or directly fixed to the highest point above all static obstacles in the dock through a telescopic mechanism. The acoustic transmitting terminal has a unique identification. The acoustic transmitting terminal is used to transmit acoustic pulse signals according to a preset TDMA time slot and a specific LFM slope. The acoustic receiving base station is deployed on a high platform pre-erected around the pool wall of the dock. The installation height of the acoustic receiving base station exceeds the highest point of all static obstacles in the dock. The acoustic receiving base station is used to receive acoustic pulse signals and verify them through a dual verification mechanism to obtain acoustic pulse signals that have passed the verification. The acoustic receiving base station performs a process to eliminate long-delay reflections and perform waveform morphology statistical discrimination on the verified acoustic pulse signals to obtain the acoustic pulse signals that have passed the discrimination. The acoustic pulse signals that have passed the discrimination are then forwarded to the shore-based calculation unit via wireless or wired communication. The shore-based calculation unit is used to extract the signal arrival time and signal source identification information of the acoustic pulse signals that have passed through, and calculates the coordinates of each underwater mobile carrier based on the time difference of arrival to obtain the positioning estimate.

[0007] According to one embodiment of the present invention, the acoustic receiving base station is used to receive acoustic pulse signals and verify them through a dual verification mechanism to obtain a verified acoustic pulse signal, including: The acoustic receiving base station is used to receive acoustic pulse signals and determine whether the arrival time of the acoustic pulse signal is consistent with the target TDMA time slot. If they are consistent, the acoustic pulse signal is sent to the matched filter group for waveform feature verification. If they are inconsistent, the acoustic pulse signal is marked as a cross-time slot interference signal and discarded. The acoustic pulse signal is slope-checked using a matched filter bank. If the check fails, the acoustic pulse signal is marked as interference and discarded. If the check passes, the acoustic pulse signal that has passed the check is obtained.

[0008] According to one embodiment of the present invention, sending the acoustic pulse signal to a matched filter bank for waveform feature verification includes: The acoustic pulse signal is sent to a matched filter bank to obtain the peak waveforms generated by different filters; Determine whether the filter that generates the maximum correlation peak is the target filter. If it is the target filter, the verification passes; otherwise, the verification fails.

[0009] According to one embodiment of the present invention, the step of removing long-delay reflections and performing waveform morphology statistical discrimination on the verified acoustic pulse signal to obtain the discriminated acoustic pulse signal includes: The acoustic pulse signal that has passed the verification is truncated according to a preset window to obtain the truncated acoustic pulse signal. The starting time of the preset window is the first zero-crossing time. The kurtosis and skewness coefficients of the truncated acoustic pulse signal are calculated. Based on the kurtosis and skewness coefficients, waveform morphology statistical discrimination is performed to obtain the acoustic pulse signal that passes the discrimination.

[0010] According to one embodiment of the present invention, the step of performing waveform morphology statistical discrimination based on kurtosis coefficient and skewness coefficient to obtain the acoustic pulse signal that passes the discrimination includes: Determine the relationship between the kurtosis coefficient and the upper and lower kurtosis thresholds. If the kurtosis coefficient is less than the upper kurtosis threshold or greater than the lower kurtosis threshold, it is judged as severe distortion and the judgment fails. If the kurtosis coefficient is greater than or equal to the upper kurtosis threshold and less than or equal to the lower kurtosis threshold, determine the relationship between the skewness coefficient and the skewness threshold. If the absolute value of the skewness coefficient is greater than the skewness threshold, it is judged as severely distorted and the judgment fails. If the absolute value of the skewness coefficient is less than or equal to the skewness threshold, it is judged as a valid direct wave and an acoustic pulse signal that passes the judgment is obtained.

[0011] According to one embodiment of the present invention, the step of extracting the signal arrival time and signal source identification information of the acoustic pulse signals that have passed the discrimination, and calculating the coordinates of each underwater mobile carrier based on the time difference of arrival to obtain the positioning estimate includes: Extract the arrival time and source identification information of the acoustic pulse signals that have passed the discrimination, establish an effective TDOA equation set, determine the relationship between the number of effective TDOA equations and the positioning dimension, if the number of effective TDOA equations is less than the positioning dimension, abandon the current solution, determine whether the timeliness of the positioning estimate at the previous moment meets the preset time threshold, if it meets the threshold, use the positioning estimate at the previous moment as the positioning estimate, if it does not meet the threshold, report the positioning loss. If the number of effective TDOA equations equals the positioning dimension, solve the effective TDOA equation system to obtain the position sequence, and then smooth the position sequence using Kalman filtering to obtain the positioning estimate. If the number of effective TDOA equations is greater than the positioning dimension, the effective TDOA equations are solved by the iterative least squares method based on Taylor series expansion to obtain the initial position sequence. The initial position sequence is then subjected to time delay consistency verification to obtain the position sequence. The position sequence is then smoothed by Kalman filtering to obtain the positioning estimate.

[0012] According to one embodiment of the present invention, the iterative least squares method based on Taylor series expansion for solving the effective TDOA equation system to obtain the initial position sequence includes: Obtain the TDOA measurement function from the valid TDOA equation system; The TDOA measurement function is expanded into a first-order Taylor series at the initial estimated position to obtain a linearized equation. Substituting the linearized equations into the effective TDOA equation system yields the residual equations; A matrix equation is constructed based on the residual equation, and the position increment is solved using the weighted least squares method. Update the current position estimate based on the position increment, and repeat the above steps until the maximum number of iterations or the convergence condition is reached to obtain the initial position sequence.

[0013] Secondly, the present invention provides a centralized high-precision positioning method for an underwater mobile carrier within a dock, the method comprising: Acoustic pulse signals are transmitted through an acoustic transmitting terminal according to a preset TDMA time slot and a specific LFM slope. The acoustic transmitting terminal is fixedly installed on the top of the underwater mobile carrier. The acoustic transmitting terminal is raised to or directly fixed to the highest point above all static obstacles in the dock through a telescopic mechanism. The acoustic transmitting terminal has a unique identification. Acoustic pulse signals are received by an acoustic receiving base station and verified by a dual verification mechanism to obtain a verified acoustic pulse signal. The acoustic receiving base station is deployed on a high platform pre-erected around the pool wall of the dock, and the installation height of the acoustic receiving base station exceeds the highest point of all static obstacles in the dock. The acoustic pulse signal that has passed the verification is processed by the acoustic receiving base station to remove long-delay reflections and perform waveform morphology statistical discrimination to obtain the acoustic pulse signal that has passed the discrimination. The acoustic pulse signal that has passed the discrimination is then forwarded to the shore-based calculation unit via wireless or wired communication. The arrival time and source identification information of the acoustic pulse signals that have passed through are extracted by the shore-based calculation unit. Based on the time difference of arrival, the coordinates of each underwater mobile carrier are calculated to obtain the positioning estimate.

[0014] According to one embodiment of the present invention, the method further includes: If the underwater mobile vehicle includes a longitudinal direction and needs to obtain the heading angle in real time, two acoustic transmitting terminals are installed on the top of the underwater mobile vehicle. The two acoustic transmitting terminals are arranged one after the other along the longitudinal centerline to form a known fixed baseline. The two acoustic transmitting terminals adopt a simultaneous or staggered transmission mode.

[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 a centralized high-precision positioning system for an underwater mobile carrier 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, wherein the computer program, when executed by a processor, implements a centralized high-precision positioning system for an underwater mobile carrier within a dock as described in the first aspect above.

[0017] Fifthly, the present invention provides a chip comprising 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 a centralized high-precision positioning system for an underwater mobile carrier within a 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 a centralized high-precision positioning system for an underwater mobile carrier within 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 centralized high-precision positioning system for underwater mobile carriers within a dock, which has the following advantages over the prior art: (1) The acoustic receiving base station of the present invention can be erected using the existing structure of the dock, without the need for construction at the bottom of the dock; the acoustic transmitting terminal is directly installed on the top of the carrier, and the modification is simple. The system has low synchronization requirements (one-way broadcast), and the hardware cost is much lower than that of the traditional long baseline response system. The number of transmitting signal sources is only related to the number of active mobile carriers, and is not related to the size of the dock or the total number of dock piers, which has good economic efficiency, flexible deployment, and controllable cost. It also supports bottom-mounted vehicles (simplified to two-dimensional positioning) and suspended robots (three-dimensional positioning), and can adaptively adjust the transmission parameters (such as increasing the transmission power, extending the pulse width, and extending the narrow window interception length) when the water quality is turbid, so as to maintain the continuity of positioning. Through the dual identification mechanism of TDMA time slot planning and LFM acoustic fingerprint, the system can manage and distinguish the signals of dozens of mobile carriers working at the same time in an orderly manner, providing a reliable positioning basis for multi-vehicle collaborative operation in the dock, and has good adaptability.

[0021] (2) This invention ensures direct wave line-of-sight propagation through physical elevation, combined with a five-level anti-multipath graded protection system, and in particular, utilizes the powerful computing power of the shore-based system to run a Taylor series iterative algorithm, effectively eliminating intra-pulse multipath interference and suppressing random noise, making the positioning accuracy significantly better than the traditional scheme that relies on the low-power closed-loop solution of the terminal. The time delay value entering the solution stage after five-level layer-by-layer screening has extremely high confidence, and with the fine approximation of the iterative algorithm, a stable positioning error of better than 5cm can be achieved, meeting the high-precision handling requirements of the dock pier, and the positioning accuracy can reach the centimeter level or even the millimeter level.

[0022] (3) The five-level hierarchical protection system designed in this invention filters out reflected waves and multipath distortion step by step from the signal receiving front end (signal layer dual verification) to the back end solution (time domain, feature, and data layers). Each level of protection is progressive—the physical layer reduces the chance of multipath entry, the signal layer ensures that the signal source is identifiable, the time domain layer eliminates reflected waves with long delays, the feature layer identifies and eliminates residual multipath with waveform distortion, and the data layer eliminates the final outliers through geometric consistency verification and timing filtering. In particular, the second-level signal layer protection completes the cross-verification of time slot assignment and slope characteristics before the signal enters the narrow window interception, eliminating cross-time slot reflected waves and crosstalk signals in advance, which greatly improves the processing efficiency and positioning success rate of subsequent levels and enhances the anti-multipath interference capability.

[0023] (4) By adopting a one-way broadcast communication mode, the mobile carrier does not need to receive a response signal, reducing the problem of bidirectional link interruption caused by obstruction; multiple receiving base stations are redundantly deployed, and the system can still be calculated by the remaining base stations even if individual base stations are momentarily obstructed; when the number of effective base stations is insufficient, the system can automatically reduce the dimensionality (from three-dimensional to two-dimensional) or use the estimated value from the previous moment, improving the continuity of positioning and enhancing the reliability of the system. Under the dual-terminal configuration, the system can still operate in a degraded manner after the failure of a single terminal. The dual-terminal scheme uses a known precise baseline as a constraint, which can simultaneously obtain centimeter-level position and 0.1-metric-level heading angle, and the joint optimization can suppress the random error of single-point positioning in reverse, further improving the overall accuracy and supporting high-precision heading calculation.

[0024] (5) The active signal source of this invention is only a small number of transport trolleys (usually a few to a dozen), and the number of signal sources is far less than the number of dock piers being transported (up to hundreds). This fundamentally reduces the channel congestion problem caused by the concurrent use of large-scale signal sources, eliminates the need for complex conflict resolution mechanisms, and makes the system architecture simple and reliable. At the same time, the positioning and calculation function is entirely deployed on shore, and the mobile terminal only needs to transmit, without the need to integrate complex calculation circuits. The hardware cost is low, the power consumption is low, and it is suitable for long-term underwater operations. This reduces complexity and facilitates large-scale engineering deployment. Attached Figure Description

[0025] 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 top view of the layout of the centralized high-precision positioning system for an underwater mobile carrier in a dock provided in an embodiment of the present invention. Figure 2 This is a layout cross-sectional view of the centralized high-precision positioning system for an underwater mobile carrier in a dock provided in an embodiment of the present invention; Figure 3 This is a logic flowchart of the five-level multipath protection system provided in the embodiments of the present invention; Figure 4 This is a flowchart of an iterative high-precision positioning algorithm based on Taylor series expansion provided in an embodiment of the present invention; Figure 5 This is a flowchart illustrating the centralized high-precision positioning method for underwater mobile carriers within a dock provided in an embodiment of the present invention. Figure 6 This is a geometric relationship diagram between the center position of the dual-terminal calculation carrier and the heading angle provided in an embodiment of the present invention; Figure 7 This is a schematic diagram of the structure of the electronic device provided in an embodiment of the present invention. Detailed Implementation

[0026] 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.

[0027] 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.

[0028] The centralized high-precision positioning system for underwater mobile vehicles in docks, the centralized high-precision positioning method for underwater mobile vehicles in docks, the electronic equipment, and the readable storage medium provided in this invention will be described in detail below with reference to the accompanying drawings and through specific embodiments and application scenarios.

[0029] Among them, the centralized high-precision positioning system for underwater mobile carriers within the dock can be applied to the terminal, specifically executed by the hardware or software within the terminal.

[0030] 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).

[0031] 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.

[0032] The centralized high-precision positioning system for underwater mobile vehicles within 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 capable of implementing the centralized high-precision positioning system for underwater mobile vehicles within a dock. The electronic devices mentioned in this embodiment include, but are not limited to, mobile phones, tablets, computers, cameras, and wearable devices. The centralized high-precision positioning system for underwater mobile vehicles within a dock provided in this embodiment of the invention will be described below using an electronic device as the implementing entity.

[0033] This invention aims to address the problem that existing conventional underwater acoustic positioning methods suffer from severe degradation in positioning accuracy (typically reduced to meter-level) in the strong multipath environment of docks, failing to meet the centimeter-level positioning requirements for precise underwater operations. Specifically, this includes: strong intra-pulse multipath interference caused by the dock walls, bottom, and dense dock piers, resulting in large errors in direct wave time delay extraction; the low installation height of positioning terminals on mobile vehicles (especially bottom-mounted vehicles) makes signals easily blocked by dock piers, causing positioning interruptions or unreliability; existing long-baseline systems require bidirectional communication, which is prone to loss of lock in obstructed environments, and suffers from large computational delays; single-point positioning has large random errors and lacks an effective joint constraint mechanism. When multiple underwater mobile vehicles operate in parallel within a dock, without an effective multi-target signal differentiation and identification mechanism, the acoustic signals emitted by each vehicle may overlap in the time or frequency domains, causing shore-based receiving base stations to be unable to effectively distinguish the signal sources, resulting in chaotic positioning data.

[0034] Figure 1 This is a top view of the layout of the centralized high-precision positioning system for underwater mobile carriers within a dock, as provided in an embodiment of the present invention. Figure 1 The diagram illustrates the layout of the dock, receiving base station (platform), and mobile carriers around the pool walls, as well as the positional relationship between them and their transmitting terminals. 1 represents the shore-based control terminals around the dock; 2 represents the dock walls; 3 represents the acoustic receiving base station; 4 represents the acoustic transmitting terminal; 5 represents the mobile carrier (bottom-mounted vehicle); 6 represents the mobile carrier (suspended robot); and 7 represents obstacles within the dock, such as dock piers.

[0035] Figure 2 This is a layout cross-sectional view of a centralized high-precision positioning system for an underwater mobile carrier in a dock provided in an embodiment of the present invention, showing the vertical height relationship between the transmitting terminal and the receiving base station above the dock pier and obstacles. The centralized high-precision positioning system for an underwater mobile carrier in a dock includes a shore-based calculation unit, at least one acoustic transmitting terminal and at least three acoustic receiving base stations. The acoustic transmitting terminal is fixedly installed on the top of the underwater mobile carrier. The acoustic transmitting terminal is raised to or directly fixed to the highest point above all static obstacles in the dock through a telescopic mechanism. The acoustic transmitting terminal has a unique identification. The acoustic transmitting terminal is used to transmit acoustic pulse signals according to a preset TDMA time slot and a specific LFM slope. As is easily understood, the acoustic transmitting terminal is fixedly installed on top of the underwater mobile platform (a bottom-sitting vehicle or a hovering robot), and its installation height is raised to a point higher than the highest point of all static obstacles (such as fixed dock piers, other underwater facilities, etc.) within the dock via a telescopic mechanism. Each transmitting terminal has a unique identifier and transmits acoustic pulse signals according to a preset TDMA timing sequence and a unique LFM slope. Typical signal parameters are: bandwidth 5kHz, pulse width 10ms, center frequency 20~30kHz. The interval between adjacent transmissions is greater than the maximum propagation delay (e.g., 50ms) to avoid time slot crosstalk.

[0036] The system adopts a one-way broadcast communication mode, where mobile carriers only transmit signals and do not need to receive return signals from acoustic base stations. Regardless of how many mobile carriers are working simultaneously in the dock, the number of signal sources is equal to the number of mobile carriers (usually a few to a dozen), which is far less than the number of fixed dock piers, resulting in a clean and controllable signal environment.

[0037] Regarding the installation method of the launch terminal, for vehicles that do not require heading, only one launch terminal can be installed. The installation position can be the top center of the carrier, or it can be adjusted to other positions according to the center of gravity balance, as long as it is higher than any obstacle. For equipment that requires heading, the baseline length of the dual terminals can be selected within the range of 0.5 meters to 2 meters according to the size of the carrier, and the installation direction can be longitudinal or lateral (corresponding to the calculated roll angle or pitch angle).

[0038] The acoustic receiving base station is deployed on a high platform pre-erected around the pool wall of the dock. The installation height of the acoustic receiving base station exceeds the highest point of all static obstacles in the dock. The acoustic receiving base station is used to receive acoustic pulse signals and verify them through a dual verification mechanism to obtain acoustic pulse signals that have passed the verification. The acoustic receiving base station performs a process to eliminate long-delay reflections and perform waveform morphology statistical discrimination on the verified acoustic pulse signals to obtain the acoustic pulse signals that have passed the discrimination. The acoustic pulse signals that have passed the discrimination are then forwarded to the shore-based calculation unit via wireless or wired communication. In some embodiments, the number of acoustic receiving base stations is at least three, but to balance overall efficiency and complexity, four to six are preferred, deployed on elevated platforms pre-erected around the dock's perimeter. The base stations are installed at a height higher than the highest point of all static obstacles within the dock (such as fixed dock piers, other underwater facilities, etc.), ensuring an unobstructed line-of-sight propagation path with the transmitting terminals on each moving target. The base stations maintain clock synchronization via 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 incorporates a matched filter bank, with each filter corresponding to a specific LFM slope, used to identify signals from different moving carriers.

[0039] Regarding the number and layout of receiving base stations, a minimum of 3 base stations is sufficient to achieve 3D positioning based on time difference of arrival. However, to improve redundancy and coverage, 4, 5, or even more base stations can be used (e.g., 2 on each of the two long sides, 1 on one short side, and no base stations deployed on the dock gate side). Base stations can be installed on high platforms on the pool walls, or they can be erected using existing structures such as existing crane beams and maintenance platforms in the dock.

[0040] After receiving the signal, each receiving base station forwards the signal or the extracted time-delay data to the shore-based processing unit via wireless or wired communication. The receiving base station only passively receives the signal and does not need to transmit any signal to the moving target.

[0041] The shore-based calculation unit is used to extract the signal arrival time and signal source identification information of the acoustic pulse signals that have passed through, and calculates the coordinates of each underwater mobile carrier based on the time difference of arrival to obtain the positioning estimate.

[0042] The shore-based calculation unit connects to all acoustic receiving base stations via radio communication (microwave / 4G / 5G) or wired communication. It receives signal arrival times and signal source identification information recorded by each base station and centrally calculates the three-dimensional (or two-dimensional) coordinates of each moving target based on the TDOA (Time Difference of Arrival) principle. The shore-based calculation unit possesses powerful computing capabilities, capable of running iterative high-precision positioning algorithms based on Taylor series expansions, achieving centimeter-level or even millimeter-level positioning accuracy. The Taylor series expansion iterative method starts from an initial guess and recalculates the partial derivative matrix in each iteration (i.e., relinearizes), gradually approximating the true solution of the nonlinear TDOA equation system. Compared to the single or quadratic closed-form solution of the Chan algorithm, the iterative method has higher estimation accuracy and better convergence performance under conditions of strong noise and poor geometric layout. However, its computational load is large, making it unsuitable for operation on low-power terminals, while the shore-based server can easily handle this computational burden.

[0043] The shore-based calculation unit is responsible for global monitoring, path planning and task scheduling, and can issue operation instructions (such as target points, travel paths, etc.) to each mobile carrier.

[0044] Meanwhile, the shore-based calculation unit displays the final positioning coordinates and status data of each moving target on the monitoring interface in real time, and performs global monitoring, path planning, and task scheduling. Each target does not need to perform calculations itself, but only needs to transmit acoustic signals according to a preset timing sequence. All intelligent processing is completed on the shore, reducing the power consumption and hardware complexity of the mobile terminal.

[0045] The shore-based solution unit will calculate the current coordinates of the carrier. With the pre-issued target locations Perform real-time comparison and calculate the positioning deviation in the horizontal plane: when ( When the preset positioning threshold (typically 1-3cm, which can be dynamically adjusted according to the required work accuracy) is reached, the system determines that the carrier has reached the designated work position and issues a "carrier in position" status indicator.

[0046] In material handling scenarios, the final work object is not the carrier itself, but rather the object being handled (such as dock piers, large components, equipment modules, etc.) held, pushed, or carried by the carrier. The carrier's function is to transport the object from its initial position to a designated placement point within the target area. Therefore, it is essential to map the carrier's high-precision positioning coordinates to the object's actual placement coordinates based on the fixed geometric offset between the carrier and the object to accurately determine whether the handling task has been truly completed.

[0047] Assume the relative positional relationship between the carrier and the object being transported is a known fixed offset in the carrier's local coordinate system. This offset is obtained through precise calibration of the carrier's mechanical structural parameters (such as the length of the robotic arm, the geometry of the push rod, and the relative position of the clamp center to the carrier's positioning reference point). During the transport process, the position of the transported object relative to the carrier remains unchanged (i.e., the transported object is firmly clamped or moved by the carrier). Therefore, the coordinates of the transported object in the global coordinate system are:

[0048] in, The heading rotation matrix of the carrier is determined by the carrier's current heading angle. Decision (For scenarios with a single terminal configuration and no heading requirement, the following can be adopted) It can be a unit matrix, or estimated based on the direction of the vehicle's movement; for a dual-terminal configuration, It can be measured by dual-terminal position calculation). In the two-dimensional bottom-sitting mode ( Given that only the horizontal coordinates need to be calculated... The offset is sufficient.

[0049] The shore-based calculation unit maps the actual placement coordinates of the transported object. With the preset target placement point Compare and calculate the deviation: when ( When the threshold for determining the arrival of the transported object is set (typically 1-2cm, which can be adjusted according to the specific accuracy requirements of the operation), it is determined that the transported object has been accurately transported to the designated location. The system issues a "transportation task completed" status indicator and records the final placement coordinates for quality traceability.

[0050] The shore-based calculation unit will calculate the real-time coordinates of each moving vehicle. With heading angle (When dual-terminal configuration is used) Real-time mapping coordinates of each transported object and its deviation from the target point The arrival / completion status indicators and positioning accuracy status indicators are pushed to the shore-based central control room monitoring platform in real time via fiber optic / Ethernet or wireless communication links. The monitoring platform displays the above information in a visual manner in real time for remote monitoring by operators. At the same time, the shore-based global task scheduling system dynamically plans subsequent operation paths based on the real-time location and task completion status of each carrier, and issues the next operation instructions to each carrier, realizing closed-loop scheduling management of multi-carrier collaborative operations within the dock.

[0051] This invention fundamentally differs from solutions that install positioning terminals on every dock pier by constructing a positioning system that integrates "active transmission from a small number of mobile carriers, centralized reception from shore-based units, and high-precision calculation." In dock construction scenarios, the active mobile carriers are only a few bottom-mounted trolleys or hovering robots used to move dock piers (usually a few to a dozen), while the actual work targets—the fixed dock piers—can number in the hundreds, but they themselves do not require positioning. Based on this, this invention installs acoustic transmission terminals on top of each underwater moving target, allowing the moving target to actively transmit acoustic signals; acoustic receiving base stations are fixedly deployed on high platforms around the dock walls (only 3-6 are needed); the shore-based calculation unit connects to all acoustic receiving base stations via wired or wireless communication, centrally receiving the signal arrival time and signal source identification information recorded by each base station, and centrally calculating the three-dimensional coordinates of each moving target based on the time difference of arrival principle.

[0052] The root cause of underwater acoustic multipath interference within the dock lies in the fact that the reinforced concrete pool walls, rigid bottom, and hundreds of fixed dock piers of varying heights surrounding the dock create a closed, highly reflective space. After multiple reflections by the pool walls, bottom, and dock piers within this confined space, sound waves form multiple coherent components at the receiving end that overlap or are adjacent to the direct wave in the time domain, resulting in severe distortion of the received waveform. This system employs a five-level, progressively layered anti-multipath interference strategy. Figure 3 This is a logical flowchart of the five-level anti-multipath hierarchical protection system provided in this embodiment of the invention. It constructs a five-level anti-multipath hierarchical protection system consisting of a physical layer, signal layer, time domain layer, feature layer, and data layer. From physical layout, signal identification, time domain truncation, waveform discrimination to data verification, multipath interference is eliminated step by step. Simultaneously, it ensures that the delay values ​​entering the TDOA calculation are all high-confidence direct wave delays. The entire process is from signal transmission, reception, time domain truncation, waveform discrimination to data calculation and verification. Each level of protection plays a role at different levels, jointly ensuring the accuracy and reliability of direct wave delay extraction. The specific process is as follows:

[0053] (1) Level 1: Physical layer - spatial isolation and line-of-sight propagation protection The acoustic receiving 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 transmitting 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.

[0054] 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 ,in The speed of sound in water is approximately 1500 m / s. 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. This reduces the number of multipath components entering subsequent processing stages from a physical perspective.

[0055] (2) Second level: Signal layer - dual identification and cross-validation of TDMA time slots and differentiated LFM slopes In some embodiments, the acoustic receiving base station is used to receive acoustic pulse signals and verify them through a dual verification mechanism to obtain acoustic pulse signals that have passed verification, including: The acoustic receiving base station is used to receive acoustic pulse signals and determine whether the arrival time of the acoustic pulse signal is consistent with the target TDMA time slot. If they are consistent, the acoustic pulse signal is sent to the matched filter group for waveform feature verification. If they are inconsistent, the acoustic pulse signal is marked as a cross-time slot interference signal and discarded. The acoustic pulse signal is slope-checked using a matched filter bank. If the check fails, the acoustic pulse signal is marked as interference and discarded. If the check passes, the acoustic pulse signal that has passed the check is obtained.

[0056] In some embodiments, sending the acoustic pulse signal to a matched filter bank for waveform feature verification includes: The acoustic pulse signal is sent to a matched filter bank to obtain the peak waveforms generated by different filters; Determine whether the filter that generates the maximum correlation peak is the target filter. If it is the target filter, the verification passes; otherwise, the verification fails.

[0057] To support simultaneous operation of multiple mobile carriers within the dock, the system employs a dual identification mechanism of "TDMA (Time Division Multiple Access) + signal feature coding" to ensure that the shore-based receiving base station can accurately distinguish the signals of each transmitting terminal, avoiding signal aliasing and misidentification. This mechanism is integrated with the second level of the subsequent five-level anti-multipath protection system, "signal layer protection."

[0058] At the time domain level, a TDMA (Time Division Multiple Address) time slot allocation strategy is adopted. Each mobile carrier is assigned a unique, preset transmission time slot, and each carrier transmits acoustic pulse signals within its own time slot. The interval between adjacent time slots must be greater than the maximum propagation delay (e.g., 50ms) to ensure that any base station receives only the direct wave signal from one carrier at any given time, fundamentally avoiding direct overlap of signals from different carriers in the time domain. When the number of carriers is small, a contention-based transmission protocol (such as ALOHA) can be used as a simplified alternative, but TDMA is the preferred solution, ensuring orderly and reliable signal transmission.

[0059] At the signal level, each carrier's transmitting terminal uses a linear frequency modulated signal with a different slope as its unique "acoustic fingerprint." That is, carrier 1 uses a slope... Carrier 2 uses slope And so on. LFM (Linear Frequency Modulation) signals have good time-frequency coupling characteristics. When LFM signals with different slopes pass through a matched filter, they will only produce significant compression correlation peaks when the filter slope matches the signal slope. Otherwise, the output is extremely low, thus providing a natural ability to distinguish at the waveform feature level.

[0060] At the receiving end, the acoustic receiving base station has a built-in matched filter bank, with each filter corresponding to a specific LFM slope. When a signal arrives, the base station first preliminarily determines its possible source carrier based on the TDMA time slot to which its arrival time belongs. Then, the signal is simultaneously fed into the matched filter bank, and the LFM slope characteristics of the signal are determined by identifying the specific filter that triggers a significantly correlated peak. Only when the time domain assignment matches the preset time slot and the waveform characteristics match is the signal considered a valid direct wave signal from that carrier. If the time domain assignment does not match the waveform characteristics (e.g., an LFM slope not planned for that time slot is detected in the same time slot, or waveform distortion due to reflection), it is considered crosstalk or a reflected wave and discarded.

[0061] This dual verification mechanism, through the synergistic effect of "coarse time slot division + fine waveform division," ensures that even if the arrival time of a signal from a certain carrier slightly exceeds its preset time slot boundary due to propagation delay and falls into an adjacent time slot, or if a reflected wave happens to fall into the time slot window of another carrier, the receiver can still accurately identify its true source through the LFM slope characteristics. This fundamentally avoids calculation errors caused by "misidentification" and "aliasing" of multiple target signals. Regardless of how many mobile carriers are operating simultaneously in the dock, as long as the TDMA time slot planning is reasonable, the signal environment will always remain clean and controllable.

[0062] Each mobile target transmitting terminal uses a linear frequency modulated signal with a different slope as a unique "signal fingerprint" and transmits it in its own dedicated TDMA time slot.

[0063] Let the first The LFM signal transmitted by a moving target can be represented as: in, For signal amplitude, This is the pulse width (typically 10ms). The center frequency is 20~30kHz. For the first The frequency modulation slope of each target.

[0064] At the receiving end, each acoustic receiving base station has a built-in matched filter bank. The impulse response of the matched filter is the time-reversed conjugate of the transmitted signal. 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 are matching LFM components. 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 produces the maximum correlation peak, the signal source target can be uniquely determined.

[0065] The receiver performs dual verification using both "time slot attribution" and "waveform characteristics": Time slot coarse screening: The base station determines the target ID expected to arrive within the current TDMA time slot based on the current time slot. If the arrival time of a signal deviates significantly from its time slot window (e.g., due to long-delay reflection waves falling into adjacent time slots), it is directly marked as cross-time slot interference and discarded, without proceeding to subsequent processing.

[0066] Waveform feature confirmation: For signals that have passed the initial time slot assignment, they are sent to a matched filter bank for slope identification. Only when the signal triggers the matched filter corresponding to its expected source in the time slot and produces a significant correlation peak is it considered a potentially valid signal; if it triggers a filter with a different slope (indicating that the signal actually comes from another target or is a strong reflection crosstalk), it is judged as an interference signal and discarded.

[0067] The core advantage of this stage lies in its ability to accurately separate signals from different targets even when propagation delays cause partial overlap in the time domain, or when reflected waves fall into the TDMA time slots of other targets. This fundamentally avoids computational errors caused by signal "source misidentification." Time slot assignment and LFM slope characteristics form a cross-validation mechanism—the former provides coarse-grained time-domain priors, while the latter provides fine-grained waveform feature confirmation. The combination of these two methods eliminates a large amount of non-direct wave interference (especially cross-time slot reflected waves and crosstalk signals between different targets) at the very beginning of signal processing, significantly reducing the processing burden on subsequent stages.

[0068] It is particularly noteworthy that this dual identification mechanism, while fulfilling the core task of distinguishing multi-target signals, also constitutes a crucial preliminary support for the subsequent multipath protection hierarchy. This dual identification mechanism directly serves the second-level (signal layer) protection: time slot assignment provides coarse-grained time-domain priors, directly discarding signals with significant time-domain mismatches; LFM slope characteristics provide fine-grained waveform confirmation, excluding signals with mismatched waveform characteristics. The combination of these two mechanisms effectively eliminates cross-time slot reflections and crosstalk signals at the very beginning of signal processing (i.e., before entering the third-level narrow window interception), significantly reducing the processing burden on subsequent levels.

[0069] Regarding multiple access methods, in addition to the "TDMA + differentiated LFM slope" combination, the following alternatives can be used: ① Pure CDMA method, where each carrier is assigned an orthogonal spreading code, allowing simultaneous transmission at the same frequency, and the base station identifies the signal source through code division; ② Waveform parameter coding, assigning different pulse widths or different coding sequences to each carrier, and the base station identifies the source by measuring signal parameters; ③ Encoded modulation with embedded carrier ID, modulating a binary carrier ID sequence (such as BPSK modulation) into the LFM signal, and the base station directly reads the carrier number after demodulation. These three methods can be combined as needed to adapt to different numbers of carriers and underwater acoustic environments.

[0070] (3) Third level: Time domain layer - narrow window interception and elimination of time-delayed reflected waves In some embodiments, the step of removing long-delayed reflected waves and performing waveform morphology statistical discrimination on the verified acoustic pulse signal to obtain the discriminated acoustic pulse signal includes: The acoustic pulse signal that has passed the verification is truncated according to a preset window to obtain the truncated acoustic pulse signal. The starting time of the preset window is the first zero-crossing time. The kurtosis and skewness coefficients of the truncated acoustic pulse signal are calculated. Based on the kurtosis and skewness coefficients, waveform morphology statistical discrimination is performed to obtain the acoustic pulse signal that passes the discrimination.

[0071] In some embodiments, the step of performing waveform morphology statistical discrimination based on kurtosis and skewness coefficients to obtain the acoustic pulse signal that passes the discrimination includes: Determine the relationship between the kurtosis coefficient and the upper and lower kurtosis thresholds. If the kurtosis coefficient is less than the upper kurtosis threshold or greater than the lower kurtosis threshold, it is judged as severe distortion and the judgment fails. If the kurtosis coefficient is greater than or equal to the upper kurtosis threshold and less than or equal to the lower kurtosis threshold, determine the relationship between the skewness coefficient and the skewness threshold. If the absolute value of the skewness coefficient is greater than the skewness threshold, it is judged as severely distorted and the judgment fails. If the absolute value of the skewness coefficient is less than or equal to the skewness threshold, it is judged as a valid direct wave and an acoustic pulse signal that passes the judgment is obtained.

[0072] For signals that pass the second-level verification, each acoustic receiving base station uses the first zero-crossing detected by the adaptive threshold 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.

[0073] 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.

[0074] 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.

[0075] Regarding the time-domain truncation window length, 3 milliseconds is a value calculated based on typical dock dimensions. In practical applications, the theoretical minimum reflection delay difference can be recalculated based on the spacing between dock piers and the distance between the dock walls. The window length can be set within the range of 2 to 5 milliseconds. If the transmitted pulse width changes (e.g., from 10 milliseconds to 20 milliseconds), the window length can be extended accordingly.

[0076] (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.

[0077] 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 represents the sequence mean.

[0078] Kurtosis coefficient of an ideal single-peak Gaussian waveform skewness coefficient (Symmetrical distribution). The discrimination criteria are as follows:

[0079] 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.

[0080] It should be noted that the upper kurtosis threshold, lower kurtosis threshold, and skewness threshold can be adaptively adjusted according to the environment.

[0081] 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. This level complements the LFM slope matching of the second level—the second level confirms the "source identity," and the fourth level confirms the "waveform quality," together ensuring the accuracy of time delay extraction.

[0082] Regarding waveform discrimination parameters, the thresholds for kurtosis and skewness can be adjusted according to the actual experimental environment; other waveform features, such as the peak-to-root mean square ratio and rising edge slope, can also be used. Furthermore, machine learning classifiers (such as support vector machines) can be trained offline and then used for online discrimination.

[0083] (5) Level 5: Data Layer - Delay Consistency Check and Kalman Filter Smoothing In some embodiments, the step of extracting the signal arrival time and signal source identification information of the identified acoustic pulse signals, calculating the coordinates of each underwater mobile vehicle based on the time difference of arrival, and obtaining a positioning estimate includes: Extract the arrival time and source identification information of the acoustic pulse signals that have passed the discrimination, establish an effective TDOA equation set, determine the relationship between the number of effective TDOA equations and the positioning dimension, if the number of effective TDOA equations is less than the positioning dimension, abandon the current solution, determine whether the timeliness of the positioning estimate at the previous moment meets the preset time threshold, if it meets the threshold, use the positioning estimate at the previous moment as the positioning estimate, if it does not meet the threshold, report the positioning loss. If the number of effective TDOA equations equals the positioning dimension, solve the effective TDOA equation system to obtain the position sequence, and then smooth the position sequence using Kalman filtering to obtain the positioning estimate. If the number of effective TDOA equations is greater than the positioning dimension, the effective TDOA equations are solved by the iterative least squares method based on Taylor series expansion to obtain the initial position sequence. The initial position sequence is then subjected to time delay consistency verification to obtain the position sequence. The position sequence is then smoothed by Kalman filtering to obtain the positioning estimate.

[0084] The shore-based solution unit performs consistency verification and filtering on the delay data reported by multiple receiving 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) When the depth of the bottom-mounted carrier is known 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:

[0085] (1) Case 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 status flag of "insufficient number of effective base stations, reduced accuracy" to the shore-based monitoring station; once the number of effective base stations recovers to meet the solution conditions in subsequent periods, the normal solution process is automatically resumed.

[0086] (2) 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.

[0087] (3) 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.

[0088] 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: The latency value is then determined to be an outlier and removed, and the remaining base stations are used to recalculate the latency. Since the shore-based base stations possess ample computing power, the data layer of this solution can handle all... The latency values ​​of each base station are globally combined and verified (i.e., groups are eliminated one by one and the residuals are evaluated, and the combination with the smallest residual is selected as the final solution basis), further improving the reliability of outlier detection. If the equation system is still overdetermined or well-determined after elimination ( ), continue solving; if after elimination it becomes underdetermined ( If so, then proceed to case one.

[0089] 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:

[0090] 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 .

[0091] 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).

[0092] 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.

[0093] In some embodiments, the iterative least squares method based on Taylor series expansion for solving the effective TDOA equation system to obtain the initial position sequence includes: Obtain the TDOA measurement function from the valid TDOA equation system; The TDOA measurement function is expanded into a first-order Taylor series at the initial estimated position to obtain a linearized equation. Substituting the linearized equations into the effective TDOA equation system yields the residual equations; A matrix equation is constructed based on the residual equation, and the position increment is solved using the weighted least squares method. Update the current position estimate based on the position increment, and repeat the above steps until the maximum number of iterations or the convergence condition is reached to obtain the initial position sequence.

[0094] It should be noted that, unlike solutions that install positioning terminals on every dock pier and are limited by terminal power consumption and computing power to run only low-complexity closed-form algorithms, the active signal source of this invention consists of only a few transport trolleys, and all raw latency data is aggregated to a shore-based server. The shore-based server possesses powerful computing capabilities and ample power supply, enabling it to employ iterative positioning algorithms with higher computational complexity but significantly better positioning accuracy than closed-form solutions. Figure 4 This is a flowchart of the iterative high-precision positioning algorithm based on Taylor series expansion provided in an embodiment of the present invention, as shown below. Figure 4 As shown, this invention preferably employs an iterative least squares method based on Taylor series expansion. This algorithm, starting from an initial guess, gradually approximates the true location, effectively utilizing redundant observation information and achieving higher positioning accuracy in strong multipath environments. The detailed derivation and implementation steps, using four receiving base stations as an example, are given below.

[0095] Step 1: Signal Transmission The coordinates of the four acoustic receiving base stations deployed on the high platform of the pool wall are known, respectively. to Each moving target transmits acoustic pulses encoded with a unique LFM slope within its designated time slot according to a preset TDMA timing sequence. The interval between adjacent transmissions is greater than the maximum propagation delay (e.g., 50ms) to avoid signal crosstalk.

[0096] Step 2: Signal Reception and Preprocessing Each receiving base station independently performs the following operations on all arriving signals: 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 target 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.

[0097] After the above preprocessing, each receiving base station obtains the effective arrival time estimate of each mobile target signal and reports it to the shore-based calculation unit via wired / wireless network.

[0098] Step 3: TDOA calculation and location determination (iterative algorithm based on Taylor series expansion) 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:

[0099] 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.

[0100] 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:

[0101] 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:

[0102] Number of independent equations in a system of equations Equal to the unknown quantity A unique solution can be obtained by direct solution. In well-posed cases, the system directly uses a single weighted least squares method to solve the closed-form solution without iteration (because when the number of equations equals the number of unknowns, the solution is unique and iteration does not change the result).

[0103] Typical scenarios include: 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, an iterative weighted least squares method based on Taylor series expansion is used to obtain a high-precision estimate in the statistically optimal sense.

[0104] (1) Establish the TDOA measurement equation Target location The goal is to reach the first The actual distance between the base stations is: The actual distance from the target to reference base station 1 is: TDOA measurement value The corresponding distance difference measurement value is: in To measure noise, the TDOA measurement function is defined as follows:

[0105] (2) Taylor series expansion and linearization Let the initial estimated position be The priority for obtaining the initial estimates is as follows: ① the filtered position estimate from the previous time step (when the time sequence is continuous); ② the closed-form solution of the Chan algorithm (when there is no historical data); ③ a rough hyperbolic intersection estimate using the delay data of the first three base stations to arrive (backup plan).

[0106] Will exist Perform a first-order Taylor series expansion at this point (ignoring higher-order terms): The partial derivatives are: Substituting the linearization result into the measurement equation and rearranging, we obtain the residual equation: (3) Construct the matrix equation and solve for the increment. For all The above equation can be written in matrix form: in, Solving for the position increment using weighted least squares method : in The covariance matrix of the TDOA measurements reflects the confidence level of each measurement. In the two-dimensional model ( ,depth (Given), the above matrices and vectors are reduced in dimension accordingly, and the quantities to be found are: , Matrix degenerates into Matrix, partial derivatives retain only the values ​​for... and Items.

[0107] (4) Iterative update and convergence judgment Update current position estimate: Repeat steps (2) and (3) until the convergence condition is met or the maximum number of iterations is reached: in For a preset convergence threshold (e.g.) (meters). In each iteration, Both partial derivatives use the current The calculations are recalculated to achieve a gradual approximation. Due to the powerful computing capabilities of the shore-based server, even dozens of iterations can be performed in milliseconds, far superior to terminal processors.

[0108] Step 4: Delay consistency check and Kalman filter 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:

[0109] 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 measurement. Abnormal observations with deviations exceeding a preset threshold are removed. The target location is then recalculated using the remaining base station data to ensure that all delay observations participating in the final positioning calculation satisfy the geometric consistency constraint. If the number of valid base stations still meets the solution conditions after removing outliers (…), then… If the number of valid base stations is insufficient, the process will switch to the underdetermined case and use the estimated value from the previous time step.

[0110] Kalman filter smoothing: The continuous positioning result sequence after passing the consistency check is smoothed by Kalman filter to suppress measurement random noise and output continuous, stable and smooth centimeter-level positioning results.

[0111] Step 5: Determining arrival status, reporting data, and completing the task loop. After four stages of anti-multipath filtering and data layer verification filtering, the shore-based solution unit obtains the high-precision positioning coordinates of the mobile carrier at the current moment. (3D mode) or (Two-dimensional bottom-sitting mode). This coordinate is the basic data source for subsequent task closure determination.

[0112] For data layer filtering, in addition to Kalman filtering, smoothing methods such as particle filtering, moving average, and median filtering can also be used. Outlier removal can be achieved using the Grubbs criterion or the Laida criterion.

[0113] Regarding communication methods, the receiving base station can use wired Ethernet, fiber optic, or RS-485 to connect to the shore-based processing unit, or it can use wireless Wi-Fi, LoRa, 4G / 5G, etc. Synchronization signals can be achieved through radio broadcasting or based on the NTP / PTP protocol.

[0114] Regarding the method of raising the launch terminal, various structural forms can be adopted, such as fixed rigid brackets, foldable brackets, or telescopic sleeves, as long as the terminal is higher than all static obstacles in the working state.

[0115] Regarding the solution algorithm, in addition to the Taylor series expansion iterative method, TDOA solution can use the Chan algorithm (providing initial values ​​for iteration), particle filtering, and other methods, dynamically switching according to different signal-to-noise ratio and accuracy requirements. When the signal-to-noise ratio is low, the Taylor series expansion method can be used first to obtain higher accuracy; in scenarios with high real-time requirements, the Chan algorithm can be used to quickly obtain initial values ​​before performing a small number of iterations.

[0116] It should be noted that for bottom-mounted mobile carriers such as bottom-sitting trolleys, their working plane can be approximated as a horizontal plane, with a depth of... The pressure is measured independently by a pressure sensor. At this point, the system automatically reduces the dimensionality to two-dimensional positioning, removing the unknown quantity from the three-dimensional Taylor iteration algorithm. Downgraded to , Matrix reduced to The matrix further improves computational efficiency, and the positioning accuracy can be improved with the same number of base stations due to the reduction of unknowns.

[0117] When the mobile carrier is a device requiring full-space movement, such as a hovering robot, the system maintains a three-dimensional positioning mode and performs a complete solution. It provides complete spatial coordinate information.

[0118] The centralized high-precision positioning system for underwater mobile carriers within a dock, provided by an embodiment of the present invention, differs fundamentally from the approach of installing positioning terminals on each dock pier. The latter involves a linear increase in the number of signal sources with the number of dock piers (up to hundreds), posing a significant challenge to multi-access and anti-collision capabilities. Furthermore, each dock pier terminal is limited by power consumption and computing power, typically only able to run low-complexity closed-loop solutions. In contrast, the active signal source in this approach is merely a transport trolley (usually a few to a dozen), with a fixed number of signal sources independent of the total number of dock piers. This results in a clean and controllable signal environment, fundamentally reducing channel congestion caused by large-scale concurrent signal sources. Simultaneously, all raw latency data is aggregated to a shore-based server. This server possesses powerful computing capabilities and ample power supply, enabling it to run iterative positioning algorithms with higher computational complexity but significantly better positioning accuracy than closed-loop solutions, thus achieving a higher upper limit for positioning accuracy in principle. This invention employs a dual identification mechanism of "TDMA time slot division + signal waveform feature encoding". Each moving target transmits signals within a preset TDMA time slot. At the same time, the signals transmitted by each target use LFM signals with different slopes as unique "acoustic ID cards". The shore-based 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".

[0119] This invention also provides a centralized high-precision positioning method for underwater mobile carriers within a dock, such as... Figure 5 As shown, the centralized high-precision positioning method for underwater mobile carriers in the dock includes steps 510, 520, 530 and 540.

[0120] Step 510: Transmit acoustic pulse signals through an acoustic transmitting terminal according to a preset TDMA time slot and a specific LFM slope. The acoustic transmitting terminal is fixedly installed on the top of the underwater mobile carrier. The acoustic transmitting terminal is raised to or directly fixed to the highest point above all static obstacles in the dock through a telescopic mechanism. The acoustic transmitting terminal has a unique identification. Step 520: Receive acoustic pulse signals through an acoustic receiving base station and verify them through a dual verification mechanism to obtain a verified acoustic pulse signal. The acoustic receiving base station is deployed on a high platform pre-erected around the pool walls of the dock. The installation height of the acoustic receiving base station exceeds the highest point of all static obstacles in the dock. Step 530: The acoustic pulse signal that has passed the verification is processed by the acoustic receiving base station to remove long-delay reflections and perform waveform morphology statistical discrimination to obtain the acoustic pulse signal that has passed the discrimination. The acoustic pulse signal that has passed the discrimination is forwarded to the shore-based calculation unit through wireless or wired communication. Step 540: Extract the arrival time and source identification information of the acoustic pulse signals that have passed through the shore-based calculation unit, calculate the coordinates of each underwater mobile carrier based on the time difference of arrival, and obtain the positioning estimate.

[0121] In some embodiments, the method further includes: If the underwater mobile vehicle includes a longitudinal direction and needs to obtain the heading angle in real time, two acoustic transmitting terminals are installed on the top of the underwater mobile vehicle. The two acoustic transmitting terminals are arranged one after the other along the longitudinal centerline to form a known fixed baseline. The two acoustic transmitting terminals adopt a simultaneous or staggered transmission mode.

[0122] Figure 6 This is a geometric diagram illustrating the relationship between the center position and heading angle of the dual-terminal calculation carrier provided in this embodiment of the invention. It shows the geometric calculation relationship between the coordinates of the two transmitting terminals and the carrier center and heading angle. If the underwater mobile carrier has a defined longitudinal direction and needs to acquire the heading angle in real time, two acoustic transmitting terminals are rigidly installed at the top of the carrier along the longitudinal centerline (spaced apart). (Precisely calibrated to an accuracy better than 1mm). Arranged along the longitudinal centerline to form a known fixed baseline (baseline length precisely calibrated to an accuracy better than 1mm). The two terminals can be transmitted simultaneously or at staggered times. For a carrier equipped with dual transmitting terminals, the transmission signals from the front and rear terminals must carry the same "carrier ID" but different "terminal sub-IDs" (e.g., carrier A-front terminal, carrier A-rear terminal) so that the shore-based solution unit can classify the two coordinates as belonging to the same carrier. These two terminals can be transmitted sequentially in two adjacent sub-time slots, or using different LFM slopes (one using...). One using To ensure they can be correctly paired at the base station, if heading information is not required, only one transmitting terminal needs to be installed.

[0123] The shore-based solution unit sequentially solves the independent coordinates of the two terminals. and Using the known baseline length as a strong constraint, a joint optimization method including least squares is employed to suppress random errors in single-point positioning, while simultaneously calculating the vehicle's heading angle. :

[0124] For a dual-terminal configuration, the shore-based solution unit can utilize the coordinates of the two terminals and the known baseline length. A joint optimization problem is constructed to further suppress measurement noise. Let the actual positions of the two terminals be respectively... and ,satisfy By solving a constrained least squares problem, the overall positioning accuracy can be further improved beyond the independent solution for a single terminal.

[0125] In some embodiments, such as Figure 7 As shown, this embodiment of the invention also provides an electronic device 700, including a processor 701, a memory 702, and a computer program stored in the memory 702 and executable on the processor 701. When the program is executed by the processor 701, it implements the various processes of the above-described centralized high-precision positioning system embodiment for underwater mobile carriers in docks and achieves the same technical effect. To avoid repetition, it will not be described again here.

[0126] 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.

[0127] 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 centralized high-precision positioning system embodiment for underwater mobile carriers in docks, and achieves the same technical effects. To avoid repetition, it will not be described again here.

[0128] 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.

[0129] This invention also provides a computer program product, including a computer program that, when executed by a processor, implements the centralized high-precision positioning system for the underwater mobile carrier within the dock.

[0130] 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.

[0131] 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 centralized high-precision positioning system embodiment for underwater mobile carriers in docks, and can achieve the same technical effect. To avoid repetition, it will not be described again here.

[0132] 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.

[0133] 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.

[0134] 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 centralized high-precision positioning system for underwater mobile carriers in docks of the various embodiments of the present invention.

[0135] In the description of this invention, "first feature" and "second feature" may include one or more of the features.

[0136] In the description of this invention, "a plurality of" means two or more.

[0137] 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.

[0138] 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.

[0139] 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 centralized high-precision positioning system for underwater mobile carriers within a dock, characterized in that, The system includes a shore-based computing unit, at least one acoustic transmitting terminal, and at least three acoustic receiving base stations; The acoustic transmitting terminal is fixedly installed on the top of the underwater mobile carrier. The acoustic transmitting terminal is raised to or directly fixed to the highest point above all static obstacles in the dock through a telescopic mechanism. The acoustic transmitting terminal has a unique identification. The acoustic transmitting terminal is used to transmit acoustic pulse signals according to a preset TDMA time slot and a specific LFM slope. The acoustic receiving base station is deployed on a high platform pre-erected around the pool wall of the dock. The installation height of the acoustic receiving base station exceeds the highest point of all static obstacles in the dock. The acoustic receiving base station is used to receive acoustic pulse signals and verify them through a dual verification mechanism to obtain acoustic pulse signals that have passed the verification. The acoustic receiving base station performs a process to eliminate long-delay reflections and perform waveform morphology statistical discrimination on the verified acoustic pulse signals to obtain the acoustic pulse signals that have passed the discrimination. The acoustic pulse signals that have passed the discrimination are then forwarded to the shore-based calculation unit via wireless or wired communication. The shore-based calculation unit is used to extract the signal arrival time and signal source identification information of the acoustic pulse signals that have passed through, and calculates the coordinates of each underwater mobile carrier based on the time difference of arrival to obtain the positioning estimate.

2. The centralized high-precision positioning system for underwater mobile carriers within a dock according to claim 1, characterized in that, The acoustic receiving base station is used to receive acoustic pulse signals and verify them through a dual verification mechanism to obtain acoustic pulse signals that have passed verification, including: The acoustic receiving base station is used to receive acoustic pulse signals and determine whether the arrival time of the acoustic pulse signal is consistent with the target TDMA time slot. If they are consistent, the acoustic pulse signal is sent to the matched filter group for waveform feature verification. If they are inconsistent, the acoustic pulse signal is marked as a cross-time slot interference signal and discarded. The acoustic pulse signal is slope-checked using a matched filter bank. If the check fails, the acoustic pulse signal is marked as interference and discarded. If the check passes, the acoustic pulse signal that has passed the check is obtained.

3. The centralized high-precision positioning system for underwater mobile carriers within a dock according to claim 2, characterized in that, The step of sending the acoustic pulse signal to the matched filter bank for waveform feature verification includes: The acoustic pulse signal is sent to a matched filter bank to obtain the peak waveforms generated by different filters; Determine whether the filter that generates the maximum correlation peak is the target filter. If it is the target filter, the verification passes; otherwise, the verification fails.

4. The centralized high-precision positioning system for underwater mobile carriers within a dock according to claim 1, characterized in that, The process of removing long-delayed reflected waves and performing waveform morphology statistical discrimination on the verified acoustic pulse signals to obtain the discriminated acoustic pulse signals includes: The acoustic pulse signal that has passed the verification is truncated according to a preset window to obtain the truncated acoustic pulse signal. The starting time of the preset window is the first zero-crossing time. The kurtosis and skewness coefficients of the truncated acoustic pulse signal are calculated. Based on the kurtosis and skewness coefficients, waveform morphology statistical discrimination is performed to obtain the acoustic pulse signal that passes the discrimination.

5. The centralized high-precision positioning system for underwater mobile carriers within a dock according to claim 4, characterized in that, The waveform morphology statistical discrimination based on kurtosis and skewness coefficients yields acoustic pulse signals that pass the discrimination, including: Determine the relationship between the kurtosis coefficient and the upper and lower kurtosis thresholds. If the kurtosis coefficient is less than the upper kurtosis threshold or greater than the lower kurtosis threshold, it is judged as severe distortion and the judgment fails. If the kurtosis coefficient is greater than or equal to the upper kurtosis threshold and less than or equal to the lower kurtosis threshold, determine the relationship between the skewness coefficient and the skewness threshold. If the absolute value of the skewness coefficient is greater than the skewness threshold, it is judged as severely distorted and the judgment fails. If the absolute value of the skewness coefficient is less than or equal to the skewness threshold, it is judged as a valid direct wave and an acoustic pulse signal that passes the judgment is obtained.

6. The centralized high-precision positioning system for underwater mobile carriers within a dock according to claim 1, characterized in that, The extraction and discrimination of the acoustic pulse signals' arrival time and signal source identification information, and the calculation of the coordinates of each underwater mobile vehicle based on the time difference of arrival to obtain a positioning estimate, include: Extract the arrival time and source identification information of the acoustic pulse signals that have passed the discrimination, establish an effective TDOA equation set, determine the relationship between the number of effective TDOA equations and the positioning dimension, if the number of effective TDOA equations is less than the positioning dimension, abandon the current solution, determine whether the timeliness of the positioning estimate at the previous moment meets the preset time threshold, if it meets the threshold, use the positioning estimate at the previous moment as the positioning estimate, if it does not meet the threshold, report the positioning loss. If the number of effective TDOA equations equals the positioning dimension, solve the effective TDOA equation system to obtain the position sequence, and then smooth the position sequence using Kalman filtering to obtain the positioning estimate. If the number of effective TDOA equations is greater than the positioning dimension, the effective TDOA equations are solved by the iterative least squares method based on Taylor series expansion to obtain the initial position sequence. The initial position sequence is then subjected to time delay consistency verification to obtain the position sequence. The position sequence is then smoothed by Kalman filtering to obtain the positioning estimate.

7. The centralized high-precision positioning system for underwater mobile carriers within a dock according to claim 6, characterized in that, The iterative least squares method based on Taylor series expansion solves the effective TDOA equation system to obtain the initial position sequence, including: Obtain the TDOA measurement function from the valid TDOA equation system; The TDOA measurement function is expanded into a first-order Taylor series at the initial estimated position to obtain a linearized equation. Substituting the linearized equations into the effective TDOA equation system yields the residual equations; A matrix equation is constructed based on the residual equation, and the position increment is solved using the weighted least squares method. Update the current position estimate based on the position increment, and repeat the above steps until the maximum number of iterations or the convergence condition is reached to obtain the initial position sequence.

8. A centralized high-precision positioning method for underwater mobile vehicles within a dock, implemented using the centralized high-precision positioning system for underwater mobile vehicles within a dock as described in any one of claims 1 to 7, characterized in that, The method includes: Acoustic pulse signals are transmitted through an acoustic transmitting terminal according to a preset TDMA time slot and a specific LFM slope. The acoustic transmitting terminal is fixedly installed on the top of the underwater mobile carrier. The acoustic transmitting terminal is raised to or directly fixed to the highest point above all static obstacles in the dock through a telescopic mechanism. The acoustic transmitting terminal has a unique identification. Acoustic pulse signals are received by an acoustic receiving base station and verified by a dual verification mechanism to obtain a verified acoustic pulse signal. The acoustic receiving base station is deployed on a high platform pre-erected around the pool wall of the dock, and the installation height of the acoustic receiving base station exceeds the highest point of all static obstacles in the dock. The acoustic pulse signal that has passed the verification is processed by the acoustic receiving base station to remove long-delay reflections and perform waveform morphology statistical discrimination to obtain the acoustic pulse signal that has passed the discrimination. The acoustic pulse signal that has passed the discrimination is then forwarded to the shore-based calculation unit via wireless or wired communication. The arrival time and source identification information of the acoustic pulse signals that have passed through are extracted by the shore-based calculation unit. Based on the time difference of arrival, the coordinates of each underwater mobile carrier are calculated to obtain the positioning estimate.

9. The centralized high-precision positioning method for underwater mobile carriers within a dock according to claim 8, characterized in that, The method further includes: If the underwater mobile vehicle includes a longitudinal direction and needs to obtain the heading angle in real time, two acoustic transmitting terminals are installed on the top of the underwater mobile vehicle. The two acoustic transmitting terminals are arranged one after the other along the longitudinal centerline to form a known fixed baseline. The two acoustic transmitting terminals adopt a simultaneous or staggered transmission mode.

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 centralized high-precision positioning method for underwater mobile carriers in a dock as described in any one of claims 8-9.

Images