Multi-beam bathymetric sonar tunnel effect correction method, device, equipment and medium

Abstract

The present invention discloses a method, device, equipment, and medium for correcting the tunnel effect of multi-beam bathymetric sonar. The present invention corrects the sidelobe echo based on the distribution characteristics of strong mirror echoes in the distance and beam dimensions, effectively eliminating the influence of the tunnel effect on measurement results.

Description

Technical Field

[0001] The present invention belongs to the technical field of sonar signal processing, and in particular relates to a method, device, equipment and medium for correcting tunnel effects of multi-beam bathymetric sonar. Background Art

[0002] Multibeam bathymetric sonar is widely used for high-precision measurements of seafloor topography. The "tunnel effect" refers to a "bathymetric artifact" that occurs when multibeam bathymetric sonar uses digital beamforming to image the seafloor. This artifact is caused by strong reflections from certain directions on the seafloor leaking into sidelobes in other directions, creating interference. When the beamforming method's sidelobe suppression capability is insufficient, the sidelobe energy in the direction of strong echoes is greater than the mainlobe energy in the direction of weak echoes. This artifact is characterized by the formation of an arc-shaped "bathymetric artifact" on the sonar image, which can severely affect the multibeam bathymetric sonar's measurements of seafloor topography.

[0003] Currently, there are two common solutions: one is to use an adaptive sidelobe canceller; the other is to optimize the beamforming algorithm, such as windowing and adopting a high-resolution beamforming algorithm.

[0004] For example, Chinese invention patent publication number CN101187579A introduces a method that first pre-processes the original signal into multiple beams to determine whether there is a strong mirror echo. For beam data with interference, the interference beam is used as a reference input, and sidelobe interference is eliminated through recursive iteration and grid prediction. However, this method requires multiple iterations, has a large amount of calculation, and requires pre-collection of the original signal to predict strong mirror echoes, which increases the complexity of system use.

[0005] In optimized beamforming algorithms, the commonly used windowing process will cause the main lobe to widen, thereby affecting the angular resolution capability; high-resolution beamforming algorithms, such as LCMV and MUSIC, are rarely used in engineering due to their large computational complexity and insufficient adaptability to complex underwater environments. Summary of the Invention

[0006] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide a method, device, equipment and medium for correcting the tunnel effect of multi-beam bathymetric sonar. Without significantly increasing the complexity and computational complexity of the system, the beam sidelobe energy at the typical distance where the tunnel effect exists is corrected, thereby reducing the impact of the difference in echo signal intensity at different angles on the bathymetric effect.

[0007] The object of the present invention is achieved through the following technical solutions:

[0008] A method for correcting tunnel effects in a multi-beam bathymetric sonar, the method comprising:

[0009] Obtain seabed imaging results of multibeam bathymetric sonar after beamforming, and select range cells affected by the tunnel effect;

[0010] The sidelobe correction coefficients generated by the receive beam pattern are used to correct the sidelobe energies of all range cells to be corrected, and a corrected beamforming result is obtained.

[0011] Furthermore, the method for generating the sidelobe correction coefficient includes:

[0012] dividing the receive beam pattern into three segments;

[0013] The first and last segments are smoothed, and the middle segment is empty data to obtain the optimized directional map;

[0014] The sidelobe correction coefficient is obtained by calculating the difference between the mean value of the receiving noise of the receiving beam pattern and the optimized pattern.

[0015] Furthermore, the correcting of the sidelobe energies of all the range cells to be corrected specifically includes:

[0016] Each distance unit that needs to be optimized is corrected using the sidelobe correction coefficient to obtain the optimized beamforming result of each distance unit. After all distance units that need to be optimized are corrected, the corrected beamforming result is obtained.

[0017] Furthermore, obtaining the seabed imaging result of the multi-beam bathymetric sonar after beamforming specifically includes:

[0018] Arrange the transceiver sensor array;

[0019] Generate multi-beam sounding echo receiving signal;

[0020] Perform conventional beamforming processing to obtain seabed imaging results.

[0021] Furthermore, the arrangement of the transceiver sensor array specifically includes:

[0022] The transceiver sensor array is placed on the sea surface to measure the flat seabed, and the transceiver sensor array and the sea surface have the same geometric center.

[0023] Furthermore, generating a multi-beam sounding echo reception signal specifically includes:

[0024] Performing Fourier transform on the echo signal of the array center channel of the transmitting array to obtain a normalized frequency spectrum distribution of the echo signal of the array center channel.

[0025] Furthermore, performing conventional beamforming processing to obtain seabed imaging results specifically includes:

[0026] The beam scanning range and beam scanning interval are set, and conventional digital beamforming is performed on the receiving signals of all channels to obtain the beamforming results of seabed imaging affected by the tunnel effect.

[0027] On the other hand, the present invention further provides a multi-beam bathymetric sonar tunnel effect correction device, which is used to implement the multi-beam bathymetric sonar tunnel effect correction method according to claim 1, and the device comprises:

[0028] The range unit acquisition module is used to obtain the seabed imaging results of the multi-beam bathymetric sonar after beamforming and select the range units affected by the tunnel effect;

[0029] The beam correction module is used to use the sidelobe correction coefficient generated by the receiving beam pattern to correct the sidelobe energy of all range units to be corrected, so as to obtain a corrected beamforming result.

[0030] On the other hand, the present invention also provides a computer device, which includes a processor and a memory, wherein a computer program is stored in the memory, and the computer program is loaded and executed by the processor to implement the above-mentioned multi-beam depth sounding sonar tunnel effect correction method.

[0031] On the other hand, the present invention also provides a computer-readable storage medium, in which a computer program is stored. The computer program is loaded and executed by a processor to implement the above-mentioned multi-beam depth sounding sonar tunnel effect correction method.

[0032] The beneficial effects of the present invention are:

[0033] (1) The present invention generates sidelobe cancellation coefficients by calculating the array pattern of the receiving beamforming algorithm and the receiving noise level, thereby offsetting the sidelobe energy of the range unit beam with the "tunnel effect" and removing the influence of the "tunnel effect" on the sounding structure.

[0034] (2) The present invention can generate sidelobe cancellation coefficients by loading the receiving pattern and the receiving noise level without changing the existing hardware architecture and preset beamforming processing algorithm of the system, thereby correcting the "tunnel effect depth sounding artifact". This will neither cause beam broadening to affect the resolution nor significantly increase the amount of calculation to affect engineering applications.

[0035] (3) In engineering applications, the present invention can generate and store sidelobe correction coefficients of different beamforming algorithms in advance according to the receiver noise level and the receiving array radiation patterns of different algorithms, and synchronously switch the sidelobe correction coefficients when the algorithm is switched, which has good engineering adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1This is a flow chart of a method for correcting tunnel effects using a multi-beam bathymetric sonar according to an embodiment of the present invention;

[0037] Figure 2 Schematic diagram of sidelobe correction coefficient generation according to an embodiment of the present invention, wherein: Figure 2 (a) is a schematic diagram of receiving beam segmentation. Figure 2 (b) is a schematic diagram of receiving sidelobe processing. Figure 2 (c) Schematic diagram of sidelobe correction coefficient generation;

[0038] Figure 3 This is a schematic diagram of the working scenario of an embodiment of the present invention;

[0039] Figure 4 : is a time domain waveform diagram of an echo signal according to an embodiment of the present invention, wherein: Figure 4 (a) is the waveform of channel 1, Figure 4 (b) is the waveform of channel 21, Figure 4 (c) is the waveform of channel 41, Figure 4 (d) is the waveform diagram of channel 61;

[0040] Figure 5 This is a normalized spectrum distribution diagram of channel 61 according to an embodiment of the present invention;

[0041] Figure 6 FIG is a diagram showing beam imaging results affected by the tunnel effect in an embodiment of the present invention;

[0042] Figure 7 is a typical angle beamforming result diagram of an embodiment of the present invention, wherein: Figure 7 (a) is the beamforming result diagram of 60°. Figure 7 (b) is the 45° beamforming result diagram. Figure 7 (c) is the beamforming result diagram of 30°. Figure 7 (d) is the beamforming result diagram at 0°;

[0043] Figure 8 is a diagram showing sidelobe correction coefficient generation at a typical distance according to an embodiment of the present invention;

[0044] Figure 9 is the corrected range-dimensional beam pattern according to the embodiment of the present invention;

[0045] Figure 10 This is a diagram of the seabed beamforming result after correction in an embodiment of the present invention;

[0046] Figure 11 This is a structural block diagram of a multi-beam bathymetric sonar tunnel effect correction device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0047] The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. The details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other unless they conflict.

[0048] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0049] Existing methods for solving the tunnel effect require multiple iterations, large amounts of calculation, and the need to pre-collect the original signal to predict strong mirror echoes, which increases the complexity of system use and lacks adaptability to complex underwater environments.

[0050] In order to solve the above technical problems, the following embodiments of the multi-beam bathymetric sonar tunnel effect correction method, device, equipment and medium of the present invention are proposed.

[0051] Example 1

[0052] Reference Figure 1 ,like Figure 1 FIG. 1 is a flow chart of a method for correcting tunnel effects using a multi-beam bathymetric sonar according to an embodiment of the present invention. The method specifically includes the following steps:

[0053] Step 1: For an existing multibeam bathymetric sonar system, obtain its beamformed seafloor imaging result P1(R,θ) and select the range unit affected by the tunneling effect. Assuming the selected range unit is R0, the energy distribution at different angles in the current range unit is P1(R0,θ).

[0054] Step 2: Combine the receiving array pattern P2(θ) and the receiving noise mean P n , and the sidelobe correction coefficient P3(θ) is calculated.

[0055] Reference Figure 2 ,like Figure 2 FIG. 1 is a schematic diagram showing the generation of the sidelobe correction coefficients in this embodiment, wherein: Figure 2 (a) is a schematic diagram of receiving beam segmentation. Figure 2 (b) is a schematic diagram of receiving sidelobe processing. Figure 2 (c) is a schematic diagram of sidelobe correction coefficient generation. The specific processing method is as follows:

[0056] Divide P2(θ) into 3 segments, with the segment nodes being the two “first zero points” of the array pattern. Smooth the first and third segments, and set the second segment between the two zero points as “empty” data to obtain the optimized sidelobe array pattern P'2(θ). Then calculate P'2(θ) and the noise floor P n The difference between the two is used to calculate the sidelobe correction coefficient P3(θ), that is, P3(θ)=P'2(θ)-P n .

[0057] Step 3: Use the sidelobe correction coefficient P3(θ) to correct the sidelobe energy P1(R0,θ) of the current range unit to obtain the optimized beamforming result P'1(θ). That is, P'1(R0,θ) = P1(R0,θ) - P3(θ).

[0058] It should be noted that, in this embodiment, the blank portion is not processed.

[0059] Step 4: Select other distance units R that need to be optimized i Repeat steps 1 to 3 until all distance units R i Correction completed.

[0060] As an implementation method, this embodiment provides the following method for obtaining seabed imaging results of a multibeam bathymetric sonar after beamforming:

[0061] Reference Figure 3 ,like Figure 3 The figure shows a schematic diagram of the working scene of the embodiment. This embodiment designs a typical multi-beam bathymetric sonar working scene, which is as follows:

[0062] The transceiver arrays are placed on the sea surface, sharing the same geometric center. The target is a flat seafloor at a depth of 100 meters. The transmitting array is omnidirectional. After irradiating the seafloor, its backscattered signal returns to the receiving transducer array. Using conventional digital beamforming algorithms, the receiving transducer array generates a two-dimensional azimuth-range image of the seafloor for depth measurement.

[0063] Generate multi-beam echo receiving signals. Assume that the transmitting array is omnidirectional, the speed of sound in water is C = 1500m / s, the transmitting signal is a sinusoidal pulse signal, the signal frequency is f = 200kHz (corresponding to the signal wavelength of λ = C / f = 0.0075m), the signal pulse width is 1ms, and the signal processing period is 400ms; Assume that the receiving array elements are omnidirectional, there are 121 receiving array elements, and the array spacing is half a wavelength d = λ / 2 = 0.00375m. Assume that the sampling rate of the received signal is 1MHz and the signal-to-noise ratio of the received signal is 10dB. Figure 4 ,like Figure 4The figure shows the time domain waveform of the echo signal in this embodiment, where: Figure 4 (a) is the waveform of channel 1, Figure 4 (b) is the waveform of channel 21, Figure 4 (c) is the waveform of channel 41, Figure 4 (d) is the waveform diagram of channel 61. Figure 4 The signal time domain characteristics of some channels (channels 1, 21, 41, and 61) are shown in the figure. It can be seen that the target echo begins to appear at a distance of 100m (corresponding to about 0.134s, calculated by the formula t=2R / C).

[0064] Reference Figure 5 ,like Figure 5 The figure shows the normalized spectrum distribution diagram of channel 61 in this embodiment. The echo signal of channel 61 (the center channel of the array) is Fourier transformed to obtain its normalized spectrum distribution. It can be seen that the spectrum energy is mainly distributed around 200kHz.

[0065] Perform conventional beamforming processing to obtain seabed imaging results. Perform conventional digital beamforming (without windowing) on ​​the received signals of 121 channels, with a beam scanning range of -65° to 65° and a beam scanning interval of 1°. Figure 6 ,like Figure 6 The figure shows the beam imaging result of this embodiment affected by the tunnel effect. Figure 6 It can be seen that at a distance of 100m, a "tunnel effect depth measurement illusion" was generated.

[0066] Select the distance dimension waveforms of the four typical directions of 0°, 30°, 45° and 60° in this figure, and refer to Figure 7 ,like Figure 7 The figure shows a typical angle beamforming result of this embodiment, where: Figure 7 (a) is the beamforming result diagram of 60°. Figure 7 (b) is the 45° beamforming result diagram. Figure 7 (c) is the beamforming result diagram of 30°. Figure 7 (d) shows the beamforming result at 0°. It can be seen that at 30°, 45°, and 60°, the echo sidelobe intensity at a distance of 100 m is higher than the backscattered echo at the corresponding angles, which seriously affects the measurement of seabed depth.

[0067] This embodiment selects the imaging result of a typical distance unit and uses the sidelobe correction coefficient generated by the receiving beam pattern to correct the sidelobe energy of the current distance unit. Assume that the waveform of the distance unit with a distance of 100m is selected, refer to Figure 8 ,like Figure 8The figure shows the sidelobe correction coefficients generated at typical distances in this embodiment. It can be observed that the waveform is highly similar to the array pattern of conventional beamforming. The figure also plots the noise floor energy and its mean at different beam angles. It can be seen that the sidelobe energy level at the current distance unit is significantly higher than the noise floor.

[0068] By using the above method to calculate the sidelobe correction coefficient, the sidelobe correction coefficient of the current range unit can be obtained. The range beam is subtracted from the correction coefficient to obtain the corrected range beam. Figure 9 ,like Figure 9 The figure shows the corrected range-dimensional beam pattern of this embodiment.

[0069] After correcting all the distance units to be corrected, the corrected beamforming results are obtained, refer to Figure 10 ,like Figure 10 The figure shows the result of the seabed beam forming after correction in this embodiment.

[0070] The multi-beam bathymetric sonar tunnel effect correction method provided in this embodiment generates a sidelobe cancellation coefficient by calculating the array pattern of the receiving beamforming algorithm and the receiving noise level, thereby offsetting the sidelobe energy of the range unit beam with the "tunnel effect" and removing the influence of the "tunnel effect" on the bathymetric structure.

[0071] Example 2

[0072] Reference Figure 11 ,like Figure 11 FIG. 1 is a block diagram of a multi-beam bathymetric sonar tunneling correction device provided in this embodiment. The device specifically includes the following structures:

[0073] The range unit acquisition module is used to obtain the seabed imaging results of the multi-beam bathymetric sonar after beamforming and select the range units affected by the tunnel effect;

[0074] The beam correction module is used to use the sidelobe correction coefficient generated by the receiving beam pattern to correct the sidelobe energy of all range units to be corrected, so as to obtain a corrected beamforming result.

[0075] The multi-beam bathymetric sonar tunnel effect correction device provided in this embodiment generates a sidelobe cancellation coefficient by receiving the array pattern of the beamforming algorithm and the receiving noise level calculation, thereby offsetting the sidelobe energy of the distance unit beam with the "tunnel effect" and removing the influence of the "tunnel effect" on the bathymetric structure.

[0076] Example 3

[0077] This preferred embodiment provides a computer device that can implement the steps of any embodiment of the multi-beam bathymetric sonar tunnel effect correction method provided in the embodiments of the present application. Therefore, the beneficial effects of the multi-beam bathymetric sonar tunnel effect correction method provided in the embodiments of the present application can be achieved. Please refer to the previous embodiments for details and will not be repeated here.

[0078] Example 4

[0079] Those skilled in the art will appreciate that all or part of the steps in the various methods of the above embodiments can be accomplished through instructions, or by controlling related hardware through instructions. The instructions can be stored in a computer-readable storage medium and loaded and executed by a processor. To this end, an embodiment of the present invention provides a storage medium storing a plurality of instructions that can be loaded by a processor to execute the steps of any of the embodiments of the multi-beam bathymetric sonar tunneling correction method provided in the embodiments of the present invention.

[0080] The storage medium may include a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, etc.

[0081] Since the instructions stored in the storage medium can execute the steps in any embodiment of the multi-beam bathymetric sonar tunnel effect correction method provided in the embodiments of the present invention, the beneficial effects that can be achieved by any multi-beam bathymetric sonar tunnel effect correction method provided in the embodiments of the present invention can be achieved. Please refer to the previous embodiments for details and will not be repeated here.

[0082] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for correcting the tunnel effect of a multi-beam bathymetric sonar, characterized in that: The method comprises: Obtain seabed imaging results of multibeam bathymetric sonar after beamforming, and select range cells affected by the tunnel effect; Using the sidelobe correction coefficients generated by the receive beam pattern, the sidelobe energies of all range cells to be corrected are corrected to obtain a corrected beamforming result; The generation of the sidelobe correction coefficient includes: dividing the receive beam pattern into three segments; The first and last segments are smoothed, and the middle segment is empty data to obtain the optimized directional map; The sidelobe correction coefficient is obtained by calculating the difference between the mean value of the receiving noise of the receiving beam pattern and the optimized pattern.

2. The multi-beam sounding sonar tunneling correction method according to claim 1, wherein: The correcting of the sidelobe energies of all the range cells to be corrected specifically includes: Each distance unit that needs to be optimized is corrected using the sidelobe correction coefficient to obtain the optimized beamforming result of each distance unit. After all distance units that need to be optimized are corrected, the corrected beamforming result is obtained.

3. The multi-beam sounding sonar tunneling correction method according to claim 1, wherein: The obtaining of the seabed imaging result of the multibeam bathymetric sonar after beamforming specifically includes: Arrange the transceiver sensor array; Generate multi-beam sounding echo receiving signal; Perform conventional beamforming processing to obtain seabed imaging results.

4. The multi-beam sounding sonar tunneling correction method according to claim 3, characterized in that: The arrangement of the transceiver sensor array specifically includes: The transceiver sensor array is placed on the sea surface to measure the flat seabed, and the transceiver sensor array and the sea surface have the same geometric center.

5. The multi-beam sounding sonar tunnel effect correction method according to claim 4, characterized in that: Generating a multi-beam sounding echo receiving signal specifically includes: Performing Fourier transform on the echo signal of the array center channel of the transmitting array to obtain a normalized frequency spectrum distribution of the echo signal of the array center channel.

6. The multi-beam sounding sonar tunneling correction method according to claim 5, characterized in that: The conventional beamforming process to obtain seabed imaging results specifically includes: The beam scanning range and beam scanning interval are set, and conventional digital beamforming is performed on the receiving signals of all channels to obtain the beamforming results of seabed imaging affected by the tunnel effect.

7. A multi-beam sounding sonar tunnel effect correction device, characterized in that: The device is used to implement the multi-beam bathymetric sonar tunnel effect correction method according to claim 1, and the device includes: The range unit acquisition module is used to obtain the seabed imaging results of the multi-beam bathymetric sonar after beamforming and select the range units affected by the tunnel effect; The beam correction module is configured to use the sidelobe correction coefficient generated by the receive beam pattern to correct the sidelobe energy of all range cells to be corrected, thereby obtaining a corrected beamforming result. The generation of the sidelobe correction coefficient includes: dividing the receive beam pattern into three segments; The first and last segments are smoothed, and the middle segment is empty data to obtain the optimized directional map; The sidelobe correction coefficient is obtained by calculating the difference between the mean value of the receiving noise of the receiving beam pattern and the optimized pattern.

8. A computer device, characterized in that: The computer device includes a processor and a memory, wherein a computer program is stored in the memory, and the computer program is loaded and executed by the processor to implement the multi-beam bathymetric sonar tunnel effect correction method according to claim 1 or 2.

9. A computer-readable storage medium, characterized in that The storage medium stores a computer program, which is loaded and executed by a processor to implement the multi-beam bathymetric sonar tunnel effect correction method according to claim 1 or 2.

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