A passive sonar ranging method and apparatus for a linear fiber optic hydrophone array

Abstract

The application discloses a passive sonar ranging method and device for a linear fiber hydrophone array, which comprises the following steps: performing primary beam forming according to original data at a first position, searching for a first azimuth angle with the maximum signal strength according to the primary beam forming result; performing secondary beam forming according to original data at a second position, searching for a second azimuth angle with the maximum signal strength according to the secondary beam forming result; and then calculating the target distance according to the first azimuth angle, the second azimuth angle, the speed and the running time. Compared with triangulation, the method and the device can reduce the measurement deviation caused by the uncertainty of the position of the fiber hydrophone array, the distance variance is smaller, and the reliability is higher in actual use.

Description

Technical Field

[0001] This invention belongs to the field of underwater acoustic target localization technology, specifically relating to a passive sonar ranging method and device for a linear fiber optic hydrophone array. Background Technology

[0002] A fiber optic hydrophone is an underwater acoustic signal sensor based on fiber optic and optoelectronic technologies. It converts underwater acoustic vibrations into optical signals through highly sensitive optical coherent detection, which are then transmitted via optical fiber to a signal processing system to extract the acoustic signal information.

[0003] A fiber optic hydrophone array is composed of fiber optic hydrophone arrays. Compared with traditional hydrophones, fiber optic hydrophones have high sensitivity, can detect weak signals, have strong resistance to electromagnetic interference and signal crosstalk, can transmit over long distances, are small in size, are easy to deploy and implement, are easy to deploy and retrieve, have high reliability, and can be networked on a large scale.

[0004] Fiber optic hydrophone technology brings a new direction to traditional measurement methods. Fiber optic hydrophone arrays measure spatial signals and, by processing the acoustic signals measured by hydrophones at each fixed location, determine the location of the sound source, enabling underwater detection, underwater target detection, and underwater / surface target radiated noise measurement. It is applied to fields such as underwater security, earthquake prediction, and offshore oil and gas exploration, providing technical support for port protection, underwater acoustic intelligence gathering, and target detection.

[0005] The TDOA (Time Difference of Arrival) algorithm is a positioning method that utilizes time differences. By measuring the time it takes for a signal to arrive at a monitoring station, the distance to the signal source can be determined. Using the distances from the signal source to each monitoring station (drawing circles with the monitoring station as the center and the distance as the radius), the signal's location can be determined. However, absolute time is generally difficult to measure. By comparing the absolute time differences of signal arrival at each monitoring station, a hyperbola can be constructed with the monitoring station as the focus and the distance difference as the major axis. The intersection of the hyperbolas is the signal's location. Unlike TOA (Time of Arrival), the TDOA algorithm determines the mobile station's location by detecting the absolute time difference of signal arrival at two base stations, rather than the time of flight. This reduces the time synchronization requirements between the signal source and each monitoring station, but increases the time synchronization requirements between the monitoring stations themselves. Using three different base stations, two TDOA measurements can be obtained, and the mobile station is located at the intersection of the hyperbolas determined by the two TDOA measurements.

[0006] The current mainstream ranging algorithm for one-dimensional linear fiber optic hydrophone arrays is various optimized algorithms based on the TDOA algorithm. However, in actual use, the positional accuracy of fiber optic hydrophones is usually not high, which leads to inaccurate calculated time difference of arrival. The TDOA algorithm is based on triangulation to calculate distance, which is very sensitive to the positional accuracy of fiber optic hydrophones. Therefore, the accuracy of the TDOA algorithm is not high under the actual use environment. Summary of the Invention

[0007] To address the aforementioned technical problems, the purpose of this invention is to provide a passive sonar ranging method and apparatus for linear fiber optic hydrophone arrays, thereby improving the accuracy of sonar ranging.

[0008] In a first aspect, to achieve the above-mentioned objective, the present invention provides a passive sonar ranging method for a linear fiber optic hydrophone array, comprising the following steps:

[0009] The raw data received in real time by the linear fiber optic hydrophone array is acquired, beamforming is performed based on the raw data, and the first azimuth angle with the strongest signal strength is searched based on the beamforming result.

[0010] The raw data received in real time after the linear fiber optic hydrophone array moves at a constant speed in a straight line for a certain period of time is acquired. Secondary beamforming is performed based on the raw data, and the second azimuth angle with the maximum signal strength is searched based on the secondary beamforming result.

[0011] The target distance is calculated based on the first azimuth angle, the second azimuth angle, the speed, and the running time.

[0012] In one embodiment, beamforming based on raw data includes:

[0013] The original data is subjected to Fast Fourier Transform (FFT) to obtain the complex output of the FFT.

[0014] Specify the beamforming search angle range and the total number of beams, and calculate the time of arrival of each element in each beam relative to the first element within the search angle range based on the element spacing.

[0015] The phase shift of the complex output of the Fast Fourier Transform is calculated based on the time difference of arrival of each beam.

[0016] The complex outputs of the Fast Fourier Transform of all channels are summed by phase shifting according to frequency, and the magnitude of the summation is used as the signal strength of each beam.

[0017] Based on the required bandwidth, the signal strength of the corresponding frequency is accumulated to obtain the signal strength of each beam under the total bandwidth, and the angle with the maximum signal strength is taken as the azimuth of arrival.

[0018] In one embodiment, the time of arrival (dT) of each element in each beam relative to the first element is calculated using the following formula based on the element spacing. m :

[0019]

[0020] Among them, A n Let d1 and d be the direction of arrival of the nth beam.m Let C represent the distances of the 1st and mth array elements relative to the origin, respectively, and let C represent the speed of sound.

[0021] In one embodiment, the signal strength of each beam is calculated using the following formula:

[0022]

[0023] Where f is the frequency, i is the channel index, m is the total number of channels, and dT i Let C be the time difference of arrival for the i-th channel. f,i R is the complex output of the Fast Fourier Transform of the i-th channel. n,f Let n be the signal strength of beam n.

[0024] In one embodiment, the target distance D is calculated using the following formula based on the first azimuth angle az1, the second azimuth angle az2, the velocity v, and the running time t. target :

[0025]

[0026]

[0027]

[0028] X and Y are intermediate variables.

[0029] Secondly, in order to achieve the above-mentioned objectives, the present invention also provides a passive sonar ranging device for a linear fiber optic hydrophone array, including a first azimuth angle calculation module, a second azimuth angle calculation module, and a target distance calculation module.

[0030] The first azimuth angle calculation module is used to obtain the raw data received in real time by the linear fiber optic hydrophone array, perform beamforming based on the raw data, and search for the first azimuth angle with the largest signal strength based on the beamforming result.

[0031] The second azimuth angle calculation module is used to obtain the raw data received in real time after the linear fiber optic hydrophone array moves at a constant speed in a straight line for a certain period of time, perform secondary beamforming based on the raw data, and search for the second azimuth angle with the largest signal strength based on the secondary beamforming result.

[0032] The target distance calculation module is used to calculate the target distance based on the first azimuth angle, the second azimuth angle, the speed, and the running time.

[0033] In one embodiment, beamforming is performed based on the original data in the first azimuth calculation module and the second azimuth calculation module, including:

[0034] The original data is subjected to Fast Fourier Transform (FFT) to obtain the complex output of the FFT.

[0035] Specify the beamforming search angle range and the total number of beams, and calculate the time of arrival of each element in each beam relative to the first element within the search angle range based on the element spacing.

[0036] The phase shift of the complex output of the Fast Fourier Transform is calculated based on the time difference of arrival of each beam.

[0037] The complex outputs of the Fast Fourier Transform of all channels are summed by phase shifting according to frequency, and the magnitude of the summation is used as the signal strength of each beam.

[0038] Based on the required bandwidth, the signal strength of the corresponding frequency is accumulated to obtain the signal strength under the total bandwidth of each beam, and the angle with the maximum signal strength is taken as the azimuth of arrival.

[0039] In one embodiment, the target distance calculation module uses the following formula to calculate the target distance D based on the first azimuth angle az1, the second azimuth angle az2, the velocity v, and the running time t. target :

[0040]

[0041]

[0042]

[0043] X and Y are intermediate variables.

[0044] Thirdly, to achieve the above-mentioned objectives, embodiments of the present invention also provide a computing device, including a memory and one or more processors, wherein the memory stores executable code, and when the one or more processors execute the executable code, they are used to implement the passive sonar ranging method for a linear fiber optic hydrophone array provided in the first aspect of the present invention.

[0045] Fourthly, to achieve the above-mentioned objectives, embodiments of the present invention also provide a computer-readable storage medium having a program stored thereon, which, when executed by a processor, implements the passive sonar ranging method for a linear fiber optic hydrophone array provided in the first aspect of the present invention.

[0046] Compared with the prior art, the beneficial effects of the present invention include at least the following:

[0047] First, beamforming is performed on the original data at the first location, and the first azimuth angle with the strongest signal strength is searched based on the beamforming result. Second, beamforming is performed on the original data at the second location, and the second azimuth angle with the strongest signal strength is searched based on the second beamforming result. Then, the target distance is calculated based on the first azimuth angle, the second azimuth angle, the speed, and the travel time. Based on this, a beamforming algorithm is adopted, using data from the entire fiber optic hydrophone array to calculate the angle of arrival. Since in real-world environments, when a ship travels in a straight line, the fiber optic hydrophone array can be approximated as being uniformly distributed on both sides of an ideal straight line. Compared to triangulation, beamforming using the original data from the entire fiber optic hydrophone array reduces measurement errors caused by the uncertainty of the fiber optic hydrophone array's position, resulting in a smaller variance in the calculated distance and higher reliability in practical use. Attached Figure Description

[0048] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0049] Figure 1 This is a flowchart of a passive sonar ranging method for a linear fiber optic hydrophone array provided in an embodiment of the present invention;

[0050] Figure 2 This is a schematic diagram of the real-time reception of raw data by a sonar array provided in an embodiment of the present invention;

[0051] Figure 3 This is a flowchart of beamforming based on raw data provided in an embodiment of the present invention;

[0052] Figure 4 This is a schematic diagram of the passive sonar ranging device for a linear fiber optic hydrophone array provided in an embodiment of the present invention.

[0053] Figure 5 This is a schematic diagram of the structure of the computing device provided in an embodiment of the present invention. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the scope of protection of this invention.

[0055] The technical concept of this invention is as follows: In view of the technical problem that the TDOA algorithm used in the prior art to calculate distance based on triangulation is very sensitive to the accuracy of the fiber optic hydrophone position, and therefore the accuracy of the TDOA algorithm is not high under the use environment, this invention provides a passive sonar ranging method and device for linear fiber optic hydrophone arrays to improve the accuracy of sonar ranging.

[0056] Figure 1 This is a flowchart of a passive sonar ranging method for a linear fiber optic hydrophone array provided in an embodiment of the present invention. Figure 1 As shown in the embodiment, the passive sonar ranging method for a linear fiber optic hydrophone array includes the following steps:

[0057] S110: Acquire the raw data received in real time by the linear fiber optic hydrophone array, perform beamforming based on the raw data, and search for the first azimuth angle with the strongest signal strength based on the beamforming result.

[0058] In this embodiment, the linear fiber optic hydrophone array is a linearly arranged fiber optic hydrophone array, such as... Figure 2 As shown, this method is used to collect the raw data returned by the target.

[0059] Specifically, the linear fiber optic hydrophone array contains m array elements S1, S2, ..., S... m Taking the first array element as the origin, the distances of each array element relative to the first array element are d1, d2, ..., d... m The linear fiber optic hydrophone array, used as an underwater signal acquisition device, is towed by a tugboat.

[0060] Perform beamforming based on the raw data, such as Figure 2 As shown, it includes:

[0061] S310 performs a Fast Fourier Transform (FFT) on the raw data received by the m-channel linear fiber optic hydrophone to obtain the complex FFT output C. f,m ;

[0062] S320 specifies the beamforming search angle range and the total number of beams n. Each beam corresponds to a direction of arrival, resulting in n uniformly distributed directions of arrival A1, A2, ..., A1. n The search angle range is calculated based on the element spacing, and the time of arrival (dT1, ..., dT) of each element in each beam relative to the first element is calculated. m This can be expressed as a formula:

[0063]

[0064] Among them, A n Let d1 and d be the direction of arrival of the nth beam. mLet represent the distances of the 1st and mth array elements relative to the origin, respectively, and let C represent the speed of sound;

[0065] S330 calculates the phase shift of the complex output of the fast Fourier transform based on the time difference of arrival of each beam;

[0066] S340 performs a phase-shifted summation of the complex outputs of the Fast Fourier Transform of m channels according to frequency. The magnitude of the summation is used as the signal strength of each beam, expressed by the formula:

[0067]

[0068] Where f is the frequency, i is the channel index, m is the total number of channels, and dT i Let C be the time difference of arrival for the i-th channel. f,i R is the complex output of the Fast Fourier Transform of the i-th channel. n,f For the direction of arrival A n The signal strength;

[0069] S350, based on the required bandwidth, accumulates the signal strength of the corresponding frequency to obtain the signal strength R under the total bandwidth of each beam. n The azimuth angle of arrival is taken as the angle with the strongest signal strength, and is expressed by the formula:

[0070] R n =∑ f R n,f .

[0071] S120 acquires the raw data received in real time after the linear fiber optic hydrophone array moves at a constant speed in a straight line for a certain period of time, performs secondary beamforming based on the raw data, and searches for the second azimuth angle with the largest signal strength based on the secondary beamforming result.

[0072] In this embodiment, the linear fiber optic hydrophone array moves at a constant speed in a straight line underwater. The raw data received in real time after the linear fiber optic hydrophone array moves at a constant speed in a straight line for a certain period of time is obtained. Then, the raw data is subjected to secondary beamforming. The method of secondary beamforming is the same as that of primary beamforming, and will not be described again here.

[0073] S130 calculates the target distance based on the first azimuth angle, the second azimuth angle, the speed, and the running time.

[0074] In this embodiment, after obtaining the first azimuth angle az1, the second azimuth angle az2, the velocity v, and the running time t, the target distance D is calculated using the following formula based on the first azimuth angle az1, the second azimuth angle az2, the velocity v, and the running time t. target :

[0075]

[0076]

[0077]

[0078] X and Y are intermediate variables.

[0079] In the above method, a beamforming algorithm is used to calculate the angle of arrival using data from the entire fiber optic hydrophone array. Since in real-world environments, when a ship travels in a straight line, the fiber optic hydrophone array can be approximated as being uniformly distributed on both sides of an ideal straight line. Compared to triangulation, beamforming using the raw data from the entire fiber optic hydrophone array reduces measurement errors caused by the uncertainty of the array's position, resulting in a smaller variance in the calculated distance and higher reliability in practical applications.

[0080] Based on the same inventive concept, such as Figure 4 As shown, the embodiment also provides a passive sonar ranging device 400 for a linear fiber optic hydrophone array, including a first azimuth angle calculation module 410, a second azimuth angle calculation module 420, and a target distance calculation module 430.

[0081] The first azimuth angle calculation module 410 is used to acquire the raw data received in real time by the linear fiber optic hydrophone array, perform beamforming based on the raw data, and search for the first azimuth angle with the largest signal strength based on the beamforming result.

[0082] The second azimuth angle calculation module 420 is used to obtain the raw data received in real time after the linear fiber optic hydrophone array moves at a constant speed in a straight line for a certain period of time, perform secondary beamforming based on the raw data, and search for the second azimuth angle with the largest signal strength based on the secondary beamforming result.

[0083] The target distance calculation module 430 is used to calculate the target distance based on the first azimuth angle, the second azimuth angle, the speed, and the running time.

[0084] It should be noted that the passive sonar ranging device for linear fiber optic hydrophone arrays provided in the above embodiments should be illustrated using the above-described functional module division as an example when performing passive sonar ranging. The functions described above can be assigned to different functional modules as needed, that is, the internal structure of the terminal or server can be divided into different functional modules to complete all or part of the functions described above. Furthermore, the passive sonar ranging device for linear fiber optic hydrophone arrays provided in the above embodiments and the passive sonar ranging method embodiments for linear fiber optic hydrophone arrays belong to the same concept. For details of its implementation, please refer to the passive sonar ranging method embodiments for linear fiber optic hydrophone arrays, which will not be repeated here.

[0085] Based on the same inventive concept, the embodiment also provides a computing device, including a memory and one or more processors. The memory stores executable code, and when the one or more processors execute the executable code, it is used to implement the above-described passive sonar ranging for a linear fiber optic hydrophone array, specifically including the following steps:

[0086] S110: Acquire the raw data received in real time by the linear fiber optic hydrophone array, perform beamforming based on the raw data, and search for the first azimuth angle with the strongest signal strength based on the beamforming result.

[0087] S120: Acquire the raw data received in real time after the linear fiber optic hydrophone array moves at a constant speed in a straight line for a certain period of time, perform secondary beamforming based on the raw data, and search for the second azimuth angle with the maximum signal strength based on the secondary beamforming result.

[0088] S130 calculates the target distance based on the first azimuth angle, the second azimuth angle, the speed, and the running time.

[0089] like Figure 5 As shown, the computing device provided in this embodiment, at the hardware level, includes not only a processor and memory, but also internal buses, network interfaces, memory, and other hardware required for business operations. The memory is non-volatile memory. The processor reads the corresponding computer program from the non-volatile memory into memory and then runs it to implement the passive sonar ranging method described in S110-S130 above. Of course, in addition to software implementation, this invention does not exclude other implementation methods, such as logic devices or a combination of hardware and software, etc. That is to say, the execution subject of the following processing flow is not limited to individual logic units, but can also be hardware or logic devices.

[0090] Based on the same inventive concept, the embodiments also provide a computer-readable storage medium storing a program thereon, which, when executed by a processor, implements the above-described passive sonar ranging method for a linear fiber optic hydrophone array, specifically including the following steps:

[0091] S110: Acquire the raw data received in real time by the linear fiber optic hydrophone array, perform beamforming based on the raw data, and search for the first azimuth angle with the strongest signal strength based on the beamforming result.

[0092] S120: Acquire the raw data received in real time after the linear fiber optic hydrophone array moves at a constant speed in a straight line for a certain period of time, perform secondary beamforming based on the raw data, and search for the second azimuth angle with the maximum signal strength based on the secondary beamforming result.

[0093] S130 calculates the target distance based on the first azimuth angle, the second azimuth angle, the speed, and the running time.

[0094] In this embodiment, computer-readable media includes both permanent and non-permanent, removable and non-removable media, and information storage can be implemented by any method or technology. Information can be computer-readable instructions, data structures, program modules, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, magnetic magnetic disk storage or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by a computing device. As defined herein, computer-readable media does not include transient computer-readable media, such as modulated data signals and carrier waves.

[0095] The specific embodiments described above illustrate the technical solution and beneficial effects of the present invention in detail. It should be understood that the above description is only the most preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, additions, and equivalent substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A passive sonar ranging method for a linear fiber optic hydrophone array, characterized in that, Includes the following steps: The raw data received in real time by the linear fiber optic hydrophone array is acquired, beamforming is performed based on the raw data, and the first azimuth angle with the strongest signal strength is searched based on the beamforming result. When the ship is traveling in a straight line, it is approximately assumed that the fiber optic hydrophone array is uniformly distributed on both sides of an ideal straight line. The raw data received in real time after the linear fiber optic hydrophone array moves at a constant speed in a straight line for a certain period of time is obtained. Secondary beamforming is performed based on the raw data, and the second azimuth angle with the maximum signal strength is searched based on the secondary beamforming result. The target distance is calculated based on the first azimuth angle, the second azimuth angle, the speed, and the travel time. The calculation formula is as follows: Where X and Y are intermediate variables, For the first azimuth angle, For the second azimuth angle, For speed, For runtime, The target distance.

2. The passive sonar ranging method for a linear fiber optic hydrophone array according to claim 1, characterized in that, Beamforming is performed based on the raw data, including: Perform a Fast Fourier Transform on the original data to obtain a complex Fast Fourier Transform output; Specify the beamforming search angle range and the total number of beams, and calculate the time of arrival of each element in each beam relative to the first element within the search angle range based on the element spacing. The phase shift of the complex output of the Fast Fourier Transform is calculated based on the time difference of arrival of each beam. The complex outputs of the Fast Fourier Transform of all channels are summed by phase shifting according to frequency, and the magnitude of the summation is used as the signal strength of each beam. According to the required bandwidth, the signal strength of the corresponding frequency is accumulated to obtain the signal strength of each beam under the total bandwidth, and the angle with the maximum signal strength is used as the azimuth of arrival.

3. The passive sonar ranging method for a linear fiber optic hydrophone array according to claim 2, characterized in that, The following formula is used to calculate the time of arrival (TOA) of each element in each beam relative to the first element, based on the element spacing. : in, The direction of arrival of the nth beam. and Let C represent the distances of the 1st and mth array elements relative to the origin, respectively, and let C represent the speed of sound.

4. The passive sonar ranging method for a linear fiber optic hydrophone array according to claim 2, characterized in that, The signal strength of each beam is calculated using the following formula: in, For frequency, For channel indexing, The total number of channels. For the first Time difference of arrival for each channel For the first Complex output of Fast Fourier Transform for each channel. Let n be the signal strength of beam n.

5. A passive sonar ranging device for a linear fiber optic hydrophone array, characterized in that, It includes a first azimuth angle calculation module, a second azimuth angle calculation module, and a target distance calculation module; The first azimuth angle calculation module is used to obtain the raw data received in real time by the linear fiber optic hydrophone array, perform beamforming based on the raw data, and search for the first azimuth angle with the largest signal strength based on the beamforming result. The second azimuth angle calculation module is used to approximate the fiber optic hydrophone array being evenly distributed on both sides of an ideal straight line when the ship is traveling in a straight line. It obtains the raw data received in real time after the linear fiber optic hydrophone array moves at a constant speed in a straight line for a certain period of time. Based on the raw data, it performs secondary beamforming and searches for the second azimuth angle with the largest signal strength based on the secondary beamforming result. The target distance calculation module is used to calculate the target distance based on the first azimuth angle, the second azimuth angle, the speed, and the running time. The calculation formula is as follows: Where X and Y are intermediate variables, For the first azimuth angle, For the second azimuth angle, For speed, For runtime, The target distance.

6. The passive sonar ranging device for a linear fiber optic hydrophone array according to claim 5, characterized in that, In the first azimuth calculation module and the second azimuth calculation module, beamforming is performed based on the original data, including: The original data is subjected to Fast Fourier Transform (FFT) to obtain the complex output of the FFT. Specify the beamforming search angle range and the total number of beams, and calculate the time of arrival of each element in each beam relative to the first element based on the element spacing. The phase shift of the complex output of the Fast Fourier Transform is calculated based on the time difference of arrival of each beam. The complex outputs of the Fast Fourier Transform of all channels are summed by phase shifting according to frequency, and the magnitude of the summation is used as the signal strength of each beam. Based on the required bandwidth, the signal strength of the corresponding frequency is accumulated to obtain the signal strength of each beam under the total bandwidth, and the angle with the maximum signal strength is taken as the azimuth of arrival.

7. A computing device comprising a memory and one or more processors, wherein the memory stores executable code, characterized in that, When the one or more processors execute the executable code, they are used to implement the passive sonar ranging method for a linear fiber optic hydrophone array as described in any one of claims 1-4.

8. A computer-readable storage medium, characterized in that, It stores a program that, when executed by a processor, implements the passive sonar ranging method for a linear fiber optic hydrophone array as described in any one of claims 1-4.

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