A method and system for underwater navigation and positioning without equivalent sound velocity estimation

Abstract

The application discloses a kind of underwater acoustic navigation positioning method and system without equivalent sound velocity estimation, method includes: obtaining the sound velocity profile data of positioning operation sea area;And layout receiving array, realize receiving end and the high-precision clock synchronization of all transmitting beacon;Receiving end receives the sending signal of individual transmitting beacon, decoding obtains the position, transmission time and transmission depth of each transmitting beacon, and records the absolute time and receiving depth of signal arrival, and then calculates the propagation time of each signal;Wherein;Sound velocity profile data, and transmitting beacon position, receiving depth and propagation time are used as input, abandon traditional approximate model of equivalent sound velocity, directly based on the physical model of sound ray propagation Calculation of the estimated propagation time corresponding to the virtual target position, and the target position is solved by optimization algorithm iteration to make the estimated propagation time match the actual propagation time;Output target estimated position that meets the iteration stop condition, realize underwater acoustic navigation positioning.

Description

Technical Field

[0001] This invention belongs to the field of underwater acoustic signal processing technology, specifically relating to an underwater acoustic navigation and positioning method and system that does not require equivalent sound speed estimation. Background Technology

[0002] Underwater acoustic navigation and positioning technology provides fundamental support for marine development and scientific research. In complex marine environments, the propagation speed of sound waves is not constant; it exhibits significant spatial and temporal dependence with variations in temperature, salinity, and depth, resulting in a complex and variable sound velocity profile. Many traditional underwater acoustic positioning methods, such as those based on Time of Arrival (TOA), Time Difference of Arrival (TDOA), or other common positioning models, typically introduce the concept of "equivalent sound velocity" or "average sound velocity" to simplify calculations. This method approximates the propagation of sound signals along an actual curved path as propagation in a straight line at a constant speed in a homogeneous medium, thus linearizing the nonlinear positioning problem.

[0003] However, this approximation method based on equivalent sound velocity introduces non-negligible systematic errors, leading to a decrease in positioning accuracy. Treating sound velocity as a parameter to be estimated and solving it together with the target position introduces approximations in the model, and the results may be unstable or have large deviations due to the coupling of model errors or observation noise.

[0004] Therefore, there is an urgent need in the existing technology for a technical solution that can avoid the dependence on the intermediate parameter of equivalent sound speed and directly start from observation data to achieve high-precision positioning based on the real physical propagation law of sound waves in non-uniform media. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies that rely on equivalent sound velocity estimation, which result in limited accuracy and poor stability, and to provide a method and system for direct underwater acoustic target localization.

[0006] In view of this, the present invention proposes an underwater acoustic navigation and positioning method that does not require equivalent sound speed estimation, comprising: Step 1: Acquire sound velocity profile data of the positioning operation sea area; and deploy a receiving array to achieve high-precision clock synchronization between the receiving end and all transmitting beacons; Step 2: Receiver receives The transmitted signals of each transmitting beacon are decoded to obtain the position, transmission time, and transmission depth of each beacon. The absolute arrival time and reception depth of the signals are recorded, and the propagation time of each signal is then calculated. ; Step 3: Using the sound speed profile data obtained in Step 1, as well as the transmitting beacon position, transmitting and receiving depth, and propagation time obtained in Step 2 as input, we abandon the traditional approximation model of equivalent sound speed and directly calculate the estimated propagation time corresponding to the virtual target position based on the physical model of sound ray propagation. We then use an optimization algorithm to iteratively solve for the target position that matches the estimated propagation time with the actual propagation time. Step 4: Output the estimated position of the target that meets the iteration cutoff condition to achieve underwater acoustic navigation and positioning.

[0007] As an improvement to the above method, the acquisition of sound velocity profile data in step 1 includes acquisition through historical databases and / or on-site drop-out temperature depth meters.

[0008] As an improvement to the above method, step 3 includes the following steps: Step 3.1: Algorithm Input: Input The location, transmission depth, reception depth, propagation time, and preset algorithm parameters of each transmitting beacon, including: error tolerance. Reflectance coefficient Expansion coefficient Shrinkage coefficient ; Total shrinkage coefficient and maximum number of iterations ; Step 3.2: Initialization: Establishing assumptions for the current location. The initial target latitude and longitude are used as the virtual target location, where... ; Step 3.3: Based on the sound speed profile data obtained in Step 1, the physical model of sound ray propagation is used to calculate the estimated propagation time between each virtual target location and each transmitting beacon. Step 3.4: Based on the results obtained in Step 2 The location of the transmitting beacon, obtained in step 3.3 Estimate the propagation time of each virtual target location and calculate the propagation time error for each virtual target location; Step 3.5: Sort the propagation time errors of all virtual target positions and determine whether the iteration cutoff condition is met. If not, proceed to step 3.6; otherwise, the algorithm ends and proceeds to step 4. Step 3.6: Iteratively optimize the current set of virtual target locations to generate new virtual target locations, and return to step 3.3 for the next iteration.

[0009] As an improvement to the above method, step 3.3 uses a ray propagation physical model, specifically a ray-based sound propagation model, which employs ray tracing to determine the propagation depth at a given emission depth. reception depth The location of the beacon is latitude and longitude. Virtual target location latitude and longitude Under the given conditions, search for sound ray trajectories that satisfy the horizontal distance between transmission and reception, and calculate their propagation time. ,in, , ; but The estimated propagation time for each virtual target location is: ,…, .

[0010] As an improvement to the above method, step 3.4 calculates the propagation time error corresponding to each virtual target position. for: , ; in, Let n be the signal propagation time of the nth transmitting beacon. For the first m The location of the virtual target is related to the first n Estimated propagation time between each transmitting beacon.

[0011] As an improvement to the above method, the iteration cutoff condition in step 3.5 is: sorting the propagation time errors of all virtual target positions: ,when Less than the tolerance Or the number of iterations equals the maximum number of iterations. If the iteration deadline is met, then the iteration deadline condition is satisfied.

[0012] As an improvement to the above method, step 3.6 iteratively optimizes the current set of virtual target locations to generate new virtual target locations, specifically including: Step 3.6.1: Discard the point with the largest error Calculate the centroids of the remaining M points. ; Step 3.6.2: Calculate the reflection point ;in, Let be the reflection coefficient, if Then let Proceed to step 3.3; Step 3.6.3: If Then calculate the extension point. ; For expansion coefficients; if ,make Proceed to step 3.3, otherwise Proceed to step 3.3; Step 3.6.4: If Calculate the contraction point ;if Then let Proceed to step 3.5; otherwise, proceed to step 3.6.5; if Calculate the internal contraction point: ,in, The shrinkage coefficient; if Then let If yes, proceed to step 3.5; otherwise, proceed to step 3.6.5. Step 3.6.5: Remove the current optimal point from the list. All other points are in accordance with Replacement is performed, where, To shrink all coefficients, proceed to step 3.3.

[0013] On the other hand, the present invention provides an underwater acoustic navigation and positioning system that does not require equivalent sound speed estimation, the system comprising: At least three transmitting beacons are used to transmit acoustic signals containing information about their own location, transmission time, and transmission depth. A receiving array is used to receive acoustic signals and is equipped with a high-precision clock to record the absolute time of signal arrival, and a depth sensor to obtain the receiving depth in real time. The data processing unit, connected to the receiving array, abandons the traditional approximation model of equivalent sound speed and directly calculates the estimated propagation time corresponding to the virtual target position based on the physical model of sound ray propagation. It then uses an optimization algorithm to iteratively solve for the target position that matches the estimated propagation time with the actual propagation time, and outputs the estimated target position that meets the iteration cutoff condition, thus realizing underwater acoustic navigation and positioning.

[0014] As an improvement to the above system, the data processing unit includes: The input module is used to receive and store the sound speed profile data of the positioning operation sea area, the position, transmission depth, reception depth, propagation time of each transmitting beacon, and preset algorithm parameters; the algorithm parameters include: error tolerance. Reflectance coefficient Expansion coefficient Shrinkage coefficient ; Total shrinkage coefficient and maximum number of iterations ; Initialization module, used to generate The initial target latitude and longitude are used as the virtual target location, where... ; The ray tracking module is used to calculate the estimated propagation time between each virtual target location and each transmitting beacon based on sound speed profile data and a ray propagation physical model. The optimization solution module is used to iteratively optimize the virtual target position based on the error between the actual propagation time and the estimated propagation time; and The output module is used to output the estimated position of the target that meets the iteration cutoff condition, so as to realize underwater acoustic navigation and positioning.

[0015] Compared with the prior art, the advantages of the present invention are: The core of this method lies in abandoning the traditional approximation model of equivalent sound speed and instead directly relying on the physical propagation model of sound waves under a known or measurable sound speed profile. This transforms the target localization problem into a matching mathematical optimization or geometric solution problem. This method does not require estimating or assuming a global or local equivalent sound speed value; instead, it utilizes the physical propagation model, the actual propagation time of the sound signal, the location of the transmitting beacon, and the transmission and reception depth information to solve for the target position. Compared to traditional localization methods based on equivalent sound speed, it achieves higher positioning accuracy. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the underwater acoustic navigation and positioning method and system that does not require equivalent sound speed estimation according to the present invention; Figure 2 This is a sound velocity profile diagram of Example 2; Figure 3 This is a comparison chart of the target positioning performance results in Example 2. Detailed Implementation

[0017] The core of this method lies in abandoning the traditional approximation model of equivalent sound speed and instead directly using the physical propagation model of sound waves under a known or measurable sound speed profile to construct the target localization problem as a matching mathematical optimization or geometric solution problem. This method does not require estimating or assuming a global or local equivalent sound speed value; instead, it uses the physical propagation model, the actual propagation time of the sound signal, the location of the transmitting beacon, and the transmission and reception depth information to solve for the target location. This method includes: Step 1: Acquire sound velocity profile data of the positioning operation sea area; and deploy a receiving array to achieve high-precision clock synchronization between the receiving end and all transmitting beacons; Step 2: Receiver receives The transmitted signals of each transmitting beacon are decoded to obtain the position, transmission time, and transmission depth of each beacon. The absolute arrival time and reception depth of the signals are recorded, and the propagation time of each signal is then calculated. ; Step 3: Using the sound speed profile data obtained in Step 1, as well as the transmitting beacon position, transmitting and receiving depth, and propagation time obtained in Step 2 as input, we abandon the traditional approximation model of equivalent sound speed and directly calculate the estimated propagation time corresponding to the virtual target position based on the physical model of sound ray propagation. We then use an optimization algorithm to iteratively solve for the target position that matches the estimated propagation time with the actual propagation time. Step 4: Output the estimated position of the target that meets the iteration cutoff condition to achieve underwater acoustic navigation and positioning.

[0018] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0019] Example 1 Embodiment 1 of the present invention proposes an underwater acoustic navigation and positioning method that does not require equivalent sound speed estimation. The overall process is as follows: Figure 1 As shown, it mainly includes: environmental data preparation, observation data acquisition, direct target localization and solution based on the ray propagation physical model, and result output.

[0020] The method includes: (I) Environmental Data Preparation Acquire sound velocity profile data for the positioning operation area. This data can be obtained through methods such as historical databases and on-site drop-in thermo-depth meters, which is known as SVP (Sound Velocity Profile). Deploy a receiving array, which can obtain the receiving depth in real time through depth sensors. The array receiver is synchronized with a high-precision clock of all transmitting beacons.

[0021] (II) Acquisition of Observational Data Assumption The number of beacons to be transmitted typically needs to meet certain conditions. The receiving end received Each transmitting beacon can be used for positioning after it sends its own signal. The transmitting beacon sends a signal containing its latitude and longitude coordinates. Launch time and launch depth The audio signal of the information is recorded by the target receiver at the absolute time of arrival. reception depth ,in, .

[0022] (III) Direct Target Localization and Solution Based on the Physical Model of Sound Propagation Once the amount of observation data meets the positioning requirements, the target is located. Specifically, 3.1. Algorithm Input: For one-time positioning The signal decoded Latitude and longitude of the transmitting beacon , Indicates longitude. Indicates dimension; corresponding The transmission depth of each signal and reception depth ; The propagation time of a signal ,in ; Error tolerance Reflectance coefficient Expansion coefficient Shrinkage coefficient ; Total shrinkage coefficient Maximum number of iterations .

[0023] 3.2. Initialization: This is the assumption for this positioning. Initial target latitude and longitude ,in , Typically, it needs to meet the following requirements. .

[0024] 3.3. Construct a physical model for forward sound ray propagation. Here, the ray sound propagation model is used for illustration, but it is not limited to this physical model for sound ray propagation.

[0025] Sound ray propagation time calculation: Based on the known SVP, the ray tracing method is used at a given emission depth. reception depth Launch latitude and longitude Virtual target latitude and longitude Under the given conditions, search for sound ray trajectories that satisfy the horizontal distance between transmission and reception, and calculate their propagation time. ,here , ; 3.4. From 3.3, we can see that for N transmitting beacons with latitude and longitude coordinates, The estimated propagation time for each target is ,…, ;calculate The propagation time error corresponding to each position: , ; 3.5. Sort according to error magnitude: Let Check if the iteration deadline condition is met. ( (For convergence tolerance) or the number of iterations equals the maximum number of iterations. If the conditions are not met, continue to step 3.6; 3.6. Center of gravity: Discard the point with the largest error. Calculate the centroid of the first M points. ; 3.7. Reflection: Calculate the reflection point ;if Then let Continue with step 3.3; 3.8. Extension: If Then calculate the extension point. ;if ,make Continue with step 3.3, otherwise Continue with step 3.3; 3.9. Contraction: If Calculate the contraction point ;if Then let Continue to step 3.5; otherwise, proceed to step 3.10; if Calculate the internal contraction point: ,if Then let If not, proceed to step 3.5; otherwise, proceed to step 3.10. 3.10. Revert: Remove all values ​​except the current best value. Use all other points Replace it, and then continue to step 3.3; (iv) Results Output Step (iii) After satisfying the iteration cutoff condition, output the estimated target position, i.e., the position with the smallest propagation time error. .

[0026] Example 2 Embodiment 2 of the present invention provides an underwater acoustic navigation and positioning method that does not require equivalent sound speed estimation. The core of this method is to bypass equivalent sound speed estimation and directly use known sound speed profile data and sound ray propagation physical model to solve for the target position by using the observed sound signal propagation time, transmitting beacon position, and receiving depth.

[0027] This embodiment uses deep-sea acoustic positioning as the application background, and the effectiveness of the invention is demonstrated through simulation. Specifically, it includes: Step 1: Select existing sound velocity profiles from the historical database of the surrounding sea area as hydrological parameters. The specific sound velocity profile structure is as follows: Figure 2 As shown.

[0028] Step 2: Assuming the receiver receives and successfully decodes the information sent by the transmitting beacon, this embodiment uses three-point positioning, i.e. The coordinates of transmitting beacon 1 (converted to Cartesian coordinates) are [0,0] m, those of transmitting beacon 2 (converted to Cartesian coordinates) are [50000, 86602.5] m, and those of transmitting beacon 3 (converted to Cartesian coordinates) are [100000,0] m. Each beacon transmits 18 sets of signals. The propagation times of each set of signals transmitted by transmitting beacons 1, 2, and 3 are [7.40 63.02 63.02], [8.13 62.44 62.44], [8.86 61.81 61.81], [9.60 59.56 59.56], [10.34 58.96 58.96], [11.09 57.99 57.99], [11.84 ... [57.3857.38], [12.59 56.78 56.78], [13.34 56.18 56.18], [14.62 55.57 55.57], [15.3354.98 54.98], [16.04 54.39 54.39], [16.76 53.81 53.81], [17.48 53.22 53.22], [18.21 53.13 53.13], [18.93 52.57 52.57], [19.69 52.01 52.01], [20.42 51.46 51.46] The transmission depth of all signals is 4000m, and the reception depth is 100m.

[0029] Step 3: Input the above information into the positioning method and set the algorithm parameters: error tolerance. Reflection coefficient p=1; Expansion coefficient γ=2; Contraction coefficient α=0.5; Total contraction coefficient σ=0.5; Maximum number of iterations Max_I=200.

[0030] Taking the first set of positioning as an example, specifically, Step 3.1, Algorithm Input: For one-time positioning The signal decoded One launch beacon location , [50000, 86602.5]m, [100000,0]m; corresponding The transmission depth of each signal [ and reception depth [ ; The propagation time of a signal s; Error tolerance Reflection coefficient p=1; Expansion coefficient γ=2; Contraction coefficient α=0.5; Total contraction coefficient σ=0.5; Maximum number of iterations. =200.

[0031] Step 3.2, Initialization, establishing the hypotheses for this localization. Initial target position , [50000, 86602.5]m, [100000,0]m; Step 3.3, Calculation of sound ray propagation time: Based on Figure 2 The known SVP shown uses ray tracing at a given emission depth. reception depth 3 launch positions [50000, 86602.5] m, [100000, 0] m, the latitude and longitude of 3 virtual targets. Under the conditions of [50000, 86602.5] m and [100000, 0] m, search for the sound ray trajectory that satisfies the horizontal distance between transmission and reception, and calculate its propagation time; Step 3.4, from step 3.3, the estimated propagation time of the three targets is... ,…, The values ​​are [2.5596 68.6198 68.6198], [68.6198 2.5596 68.6198], and [68.6198 68.6198 2.5596], respectively. Calculate the propagation time error corresponding to the three positions: , thus obtaining [87.1727 7433.9064 7433.9064].

[0032] Step 3.5, sort according to error magnitude: Let The check indicates that the iteration cutoff condition is not met. ( (or the number of iterations equals the maximum number of iterations) =200, continue with step 3.6; Step 3.6, Center of Gravity: Discard the point with the largest error. Calculate the centroid of the first M points. The value is [2500, 43301.2701]m; Step 3.7, Reflection: Calculate the reflection point We obtain [-50000 86602.5404]m, and calculate... = 6565.2804, which satisfies the condition. Then let Continue with step 3.3; continue iterating until convergence. Perform the 18 localizations sequentially.

[0033] Step 4: After the algorithm converges, the error values ​​between the 18 sets of positioning results and the actual target position are [0.70 12.83 45.25 90 3.93 386.79 2.07 1.11 3.97 4.96 8.25 10.45 6.93 9.45 1.11 7.99 8.92 7.73 5.94] m.

[0034] Furthermore, by comparing the positioning results with those obtained using traditional methods based on equivalent sound speed estimation, the following results were obtained: Figure 3 The comparison chart of positioning errors shown demonstrates that the proposed method achieves higher positioning accuracy compared to traditional positioning methods based on equivalent sound velocity.

[0035] Example 3 Embodiment 3 of the present invention provides an underwater acoustic navigation and positioning system that does not require equivalent sound speed estimation, implemented based on the method of Embodiment 1. The system includes: At least three transmitting beacons are used to transmit acoustic signals containing information about their own location, transmission time, and transmission depth. A receiving array is used to receive acoustic signals and is equipped with a high-precision clock to record the absolute time of signal arrival, and a depth sensor to obtain the receiving depth in real time. The data processing unit, connected to the receiving array, abandons the traditional approximation model of equivalent sound speed and directly calculates the estimated propagation time corresponding to the virtual target position based on the physical model of sound ray propagation. It then uses an optimization algorithm to iteratively solve for the target position that matches the estimated propagation time with the actual propagation time, and outputs the estimated target position that meets the iteration cutoff condition, thus realizing underwater acoustic navigation and positioning.

[0036] Specifically, the data processing unit includes: The input module is used to receive and store the sound speed profile data of the positioning operation sea area, the position, transmission depth, reception depth, propagation time of each transmitting beacon, and preset algorithm parameters; the algorithm parameters include: error tolerance. Reflectance coefficient Expansion coefficient Shrinkage coefficient ; Total shrinkage coefficient and maximum number of iterations ; Initialization module, used to generate The initial target latitude and longitude are used as the virtual target location, where... ; The ray tracking module is used to calculate the estimated propagation time between each virtual target location and each transmitting beacon based on sound speed profile data and a ray propagation physical model. The optimization solution module is used to iteratively optimize the virtual target position based on the error between the actual propagation time and the estimated propagation time. The output module is used to output the estimated position of the target that meets the iteration cutoff condition, so as to realize underwater acoustic navigation and positioning.

[0037] It is worth noting that in the embodiments of the above system, the modules included are divided according to functional logic, but are not limited to the above division, as long as the corresponding functions can be achieved; in addition, the specific names of each functional module are only for easy differentiation and are not used to limit the scope of protection of the present invention.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for underwater acoustic navigation and positioning that does not require equivalent sound velocity estimation, comprising: Step 1: Obtain sound velocity profile data for the positioning operation sea area; A receiver array is deployed to achieve high-precision clock synchronization between the receiver and all transmitting beacons; Step 2: Receiver receives The transmitted signals of each transmitting beacon are decoded to obtain the position, transmission time, and transmission depth of each beacon. The absolute arrival time and reception depth of the signals are recorded, and the propagation time of each signal is then calculated. ; Step 3: Using the sound speed profile data obtained in Step 1, as well as the transmitting beacon position, transmitting and receiving depth, and propagation time obtained in Step 2 as input, we abandon the traditional approximation model of equivalent sound speed and directly calculate the estimated propagation time corresponding to the virtual target position based on the physical model of sound ray propagation. We then use an optimization algorithm to iteratively solve for the target position that matches the estimated propagation time with the actual propagation time. Step 4: Output the estimated position of the target that meets the iteration cutoff condition to achieve underwater acoustic navigation and positioning; Step 3 includes the following steps: Step 3.1: Algorithm Input: Input The location, transmission depth, reception depth, propagation time, and preset algorithm parameters of each transmitting beacon, including: error tolerance. Reflectance coefficient Expansion coefficient Shrinkage coefficient ; Total shrinkage coefficient and maximum number of iterations ; Step 3.2: Initialization: Establishing assumptions for the current location. The initial target latitude and longitude are used as the virtual target location, where... ; Step 3.3: Based on the sound speed profile data obtained in Step 1, the physical model of sound ray propagation is used to calculate the estimated propagation time between each virtual target location and each transmitting beacon. Step 3.4: Based on the results obtained in Step 2 The location of the transmitting beacon, obtained in step 3.3 Estimate the propagation time of each virtual target location and calculate the propagation time error for each virtual target location; Step 3.5: Sort the propagation time errors of all virtual target positions and determine whether the iteration cutoff condition is met. If not, proceed to step 3.6; otherwise, the algorithm ends and proceeds to step 4. Step 3.6: Iteratively optimize the current set of virtual target locations to generate new virtual target locations, and return to step 3.3 for the next iteration; The sound ray propagation physical model used in step 3.3 is the ray sound propagation model. Using the ray tracing method, at a given emission depth... reception depth The location of the beacon is latitude and longitude. Virtual target location latitude and longitude Under the given conditions, search for sound ray trajectories that satisfy the horizontal distance between transmission and reception, and calculate their propagation time. ,in, , ; but The estimated propagation time for each virtual target location is: ,…, ; Step 3.4 calculates the propagation time error corresponding to each virtual target position. for: ， ； in, Let n be the signal propagation time of the nth transmitting beacon. For the first m The location of the virtual target is related to the first n Estimated propagation time between each transmitting beacon.

2. The underwater acoustic navigation and positioning method without equivalent sound speed estimation according to claim 1, characterized in that, The acquisition of sound velocity profile data in step 1 includes acquisition through historical databases and / or on-site drop-out temperature and depth meters.

3. The underwater acoustic navigation and positioning method without equivalent sound speed estimation according to claim 1, characterized in that, The iteration cutoff condition in step 3.5 is: sorting the propagation time errors of all virtual target positions: ,when Less than the tolerance Or the number of iterations equals the maximum number of iterations. If the iteration deadline is met, then the iteration deadline condition is satisfied.

4. The underwater acoustic navigation and positioning method without equivalent sound speed estimation according to claim 3, characterized in that, Step 3.6 iteratively optimizes the current set of virtual target locations to generate new virtual target locations, specifically including: Step 3.6.1: Discard the point with the largest error Calculate the centroids of the remaining M points. ; Step 3.6.2: Calculate the reflection point ;in, Let be the reflection coefficient, if Then let Proceed to step 3.3; Step 3.6.3: If Then calculate the extension point. ; For expansion coefficients; if ,make Proceed to step 3.3, otherwise Proceed to step 3.3; Step 3.6.4: If Calculate the contraction point ;if Then let Proceed to step 3.5; otherwise, proceed to step 3.6.5; if Calculate the internal contraction point: ,in, The shrinkage coefficient; if Then let If yes, proceed to step 3.5; otherwise, proceed to step 3.6.

5. Step 3.6.5: Remove the current optimal point from the list. All other points are as follows Replacement is performed, where, To shrink all coefficients, proceed to step 3.

3.

5. A system based on the underwater acoustic navigation and positioning method without equivalent sound speed estimation as described in claim 1, characterized in that, The system includes: At least three transmitting beacons are used to transmit acoustic signals containing information about their own location, transmission time, and transmission depth. A receiving array for receiving acoustic signals, equipped with a high-precision clock to record the absolute time of signal arrival, and a depth sensor to acquire the receiving depth in real time; and The data processing unit, connected to the receiving array, abandons the traditional approximation model of equivalent sound speed and directly calculates the estimated propagation time corresponding to the virtual target position based on the physical model of sound ray propagation. It then uses an optimization algorithm to iteratively solve for the target position that matches the estimated propagation time with the actual propagation time, and outputs the estimated target position that meets the iteration cutoff condition, thus realizing underwater acoustic navigation and positioning.

6. The system according to claim 5, characterized in that, The data processing unit includes: The input module is used to receive and store the sound speed profile data of the positioning operation sea area, the position, transmission depth, reception depth, propagation time of each transmitting beacon, and preset algorithm parameters; the algorithm parameters include: error tolerance. Reflectance coefficient Expansion coefficient Shrinkage coefficient ; Total shrinkage coefficient and maximum number of iterations ; Initialization module, used to generate The initial target latitude and longitude are used as the virtual target location, where... ; The ray tracking module is used to calculate the estimated propagation time between each virtual target location and each transmitting beacon based on sound speed profile data and a ray propagation physical model. The optimization solution module is used to iteratively optimize the virtual target position based on the error between the actual propagation time and the estimated propagation time; and The output module is used to output the estimated position of the target that meets the iteration cutoff condition, so as to realize underwater acoustic navigation and positioning.

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