A real-time self-measurement and evaluation method for underwater radiated noise of aircraft

Abstract

The present invention discloses a method for real-time self-measurement and evaluation of underwater radiation noise of an aircraft, and belongs to the technical field of underwater aircraft noise monitoring and evaluation. The method uses a specific maneuvering method when the underwater aircraft is in a towed sonar state to keep a stable relative position relationship with the towed array for a period of time, and completes the measurement of the self-radiated noise level and characteristics through array estimation, focused beam forming and other methods, so that the underwater aircraft can finally understand its own radiation noise situation without geographical and time restrictions when it is in navigation, and grasp the current acoustic stealth situation. The method can be used as a supplement and reference means for evaluating the radiation noise of the underwater aircraft during navigation.

Description

Technical Field

[0001] The invention belongs to the technical field of underwater vehicle noise monitoring and evaluation, and in particular relates to a real-time self-measurement and evaluation method for underwater radiation noise of a vehicle. Background Art

[0002] The existing underwater radiated noise measurement methods mainly include fixed and mobile methods. The fixed method refers to fixing the hydrophone (array) at a specified position in a specific sea area to measure the radiated noise, such as CN116929531A "A UUV navigation radiated noise measurement system"; while the mobile method mainly relies on auxiliary measurement ships to deploy the noise measurement system in the experimental sea area for noise measurement, such as CN117647796A "A method for simulating passive detection data of a towed array in a deep-sea environment". These two measurement methods have high requirements for the environment and auxiliary facilities, and cannot achieve online measurement and prediction of radiated noise in any marine environment.

[0003] Compared with traditional underwater radiation noise measurement methods such as test sites and auxiliary measurement ships, the ship uses its own towed array to measure the body noise, which has many advantages such as flexibility, convenience and low cost. For underwater vehicles, using towed sonar to measure the body self-noise can enable underwater vehicles to quickly understand the body radiation noise level during navigation, grasp their own acoustic stealth status, and provide reference for underwater vehicle action decisions.

[0004] If the underwater vehicle can maintain a relatively stable posture with the entire or part of the towed array for a period of time through certain maneuvers during the towed sonar process, and is in a position close to the horizontal direction of the towed array, the underwater vehicle can be continuously detected by the towed array sonar as a target, thereby realizing the measurement of its own radiated noise. Summary of the invention

[0005] In view of the above technical problems and application background, the present invention provides a method for real-time self-measurement and evaluation of underwater radiated noise of an aircraft, which uses a towed sonar of an underwater aircraft to measure the radiated noise of the body in real time, so that the towed sonar of the underwater aircraft can quickly measure the radiated noise during navigation, including the following steps:

[0006] S1. Determine whether the current environment is suitable for deploying towed sonar and measuring radiated noise.

[0007] S2. Determine the maneuvering method to be adopted for measurement according to the task requirements.

[0008] S3. Determine the background noise level based on the measured ocean ambient noise and sonar flow noise levels NL , determine the sound source level based on the predicted underwater vehicle radiated noise level SL.

[0009] S4, the background noise level in step S3 NL and sound source level SL Substitute into the sonar equation to calculate the appropriate underwater vehicle radiated noise measurement time T , measure distance R And the number of sonar array elements selected N .

[0010] S5. According to the underwater vehicle control theory and the length of the underwater vehicle d， Sonar array size h , determine the underwater vehicle maneuvering route parameters and measurement timing.

[0011] S6. Perform formation estimation and calculate the coordinates of the towed array sonar elements.

[0012] S7. According to the parameters determined in steps S4-S6, the position and distance of the underwater vehicle are determined by focusing the beam forming space scanning method.

[0013] S8. Calculate time domain beam data according to the underwater vehicle position and distance in step S7.

[0014] S9. Perform power spectrum analysis on the time domain beam data to obtain the power spectrum of the radiated noise.

[0015] S10, converting the power spectrum measured in step S9 into the sound source level of the underwater vehicle radiated noise.

[0016] Furthermore, the current environment described in step S1 requires that the sea depth meets the minimum depth requirements for the underwater vehicle to dive and the towed sonar to be deployed, the height from the bottom of the underwater vehicle and the towed sonar meets the safety indicators, there are no seabed obstacles in the surrounding sea area, and the sea condition is not greater than level 3.

[0017] Furthermore, the maneuvering mode described in step S2 includes a U-shaped maneuvering mode and a circular maneuvering mode.

[0018] Further, the calculation method in step S4 is to refer to the energy relationship in the passive sonar equation. For the line spectrum signal, the signal-to-noise ratio is

[0019] ;

[0020] For a broadband radiated noise signal, the signal-to-noise ratio is

[0021] ;

[0022] In the formula DF is the processing gain of Fourier transform for single-frequency signal, DI is the space gain, TL is the propagation loss, where:

[0023] ;

[0024] ;

[0025] ;

[0026] In the formula T To measure time, N To select the number of sonar array elements, R is the measured distance from the sound source to the receiving array.

[0027] At the same time, in order to average the results of multiple measurements to reduce errors, the measurement time needs to be increased; in order to ensure that the array is close to a linear array to the greatest extent, reduce the difficulty of array estimation and the influence of array distortion, it is necessary to select part of the array to participate in the calculation; reducing the distance between the underwater vehicle and the towed array can reduce the propagation loss, but it will shorten the stable measurement time; considering the above factors comprehensively, according to the preset signal-to-noise ratio requirements, SNR ≥3dB, calculate the reasonable measurement time , Detection duration , measure distance R Number of array elements N ,in, , n is the number of measurement segments to be averaged.

[0028] Further, the underwater vehicle maneuvering path parameter in step S5 is: Γ , towed sonar cable length L and underwater vehicle speed V ;in, .

[0029] The measurement timing is the time when the measurement starts and ends. and location , so that the underwater vehicle is located in the horizontal direction of the towed array,

[0030] ;

[0031] .

[0032] Furthermore, in step S6, during the formation estimation measurement, the heading data measured by the heading sensors distributed at the fixed positions of the towed array are interpolated and fitted to analyze the duration. The coordinates of each sonar array element are estimated for the unit x 1 , x 2 , … , x N .

[0033] Further, in step S7, by focusing the beam forming spatial scanning method, refer to the towed array reference element to find the maximum noise energy The corresponding position θ and distance D , i.e. the acoustic center position of the underwater vehicle ;in, is the time delay from the scanning position to each array element and the reference array element, , c is the speed of sound in seawater, is the time domain data of each array element, and 0≤ t ≤ T .

[0034] Further, in step S8, the time delay from the underwater vehicle sound center position to each array element and the reference array element is For the time domain data of each array element Time shift to obtain , add up to get the time domain beam data x ( t ), i =1,2,…, N -1, the calculation method is:

[0035] ;

[0036] ;

[0037] .

[0038] Further, in step S9, steps S6-S8 are repeated until the detection time is reached. T s ; Perform power spectrum analysis on the obtained time domain data in segments and take the average to obtain the power spectrum of the radiated noise :

[0039] .

[0040] Further, in step S10, according to the propagation loss formula, the measured power spectrum is converted to 1 meter away from the equivalent sound center of the underwater vehicle to obtain the sound source level of the underwater vehicle radiated noise , the calculation formula is: . Beneficial Effects

[0041] 1. Compared with traditional underwater radiated noise measurement methods such as test sites and auxiliary measurement ships, the ship uses its own towed array to measure the main body noise, which has the advantages of flexible and convenient use and low cost.

[0042] 2. By using a specific maneuvering method when the underwater vehicle is towing the sonar, the underwater vehicle can maintain a stable relative position relationship with the towed array for a period of time, and complete the measurement of its own radiation noise level and characteristics through methods such as formation estimation and focused beam forming. Ultimately, the underwater vehicle can understand its own radiation noise situation without geographical and time restrictions while sailing, and grasp the current acoustic stealth situation. This can serve as a supplement and reference means for the rapid evaluation of the radiation noise of the underwater vehicle during navigation, and provide a reference for the underwater vehicle's action decision-making. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to make the contents of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings.

[0044] Figure 1 It is a schematic flow chart of the real-time self-measurement and evaluation method for underwater vehicle radiated noise in the present invention;

[0045] Figure 2 It is a schematic diagram of the mobile measurement situation in the present invention;

[0046] Figure 3 It is a schematic diagram of the hydrophone array signal processing flow in the present invention;

[0047] Figure 4 This is a schematic diagram of a U-shaped maneuver of an underwater vehicle in the present invention;

[0048] Figure 5 It is a schematic diagram of the circular maneuver of the underwater vehicle in the present invention. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the method of the present invention and are not used to limit the method of the present invention.

[0050] The present invention provides a method for real-time self-measurement and evaluation of underwater radiated noise of an aircraft, which uses a towed sonar of an underwater aircraft to measure the radiated noise of the body in real time, so that the towed sonar of the underwater aircraft can quickly measure the radiated noise during navigation. For example, the flow chart of the towed sonar of an underwater submarine measuring radiated noise is as follows: Figure 1 , specifically including the following steps:

[0051] S1. Determine whether the current environment is suitable for deploying towed sonar and measuring radiated noise.

[0052] S2. Determine the maneuvering method to be adopted for measurement according to the task requirements.

[0053] S3. Determine the background noise level based on the measured ocean ambient noise and sonar flow noise levels NL , determine the sound source level based on the predicted underwater vehicle radiated noise level SL.

[0054] S4, the background noise level in step S3 NL and sound source level SL Substitute into the sonar equation to calculate the appropriate underwater vehicle radiated noise measurement time T , measure distance R And the number of sonar array elements selected N .

[0055] S5. According to the underwater vehicle control theory and the length of the underwater vehicle d， Sonar array size h , determine the underwater vehicle maneuvering route parameters and measurement timing.

[0056] S6. Perform formation estimation and calculate the coordinates of the towed array sonar elements.

[0057] S7. According to the parameters determined in steps S4-S6, the position and distance of the underwater vehicle are determined by focusing the beam forming space scanning method.

[0058] S8. Calculate time domain beam data according to the underwater vehicle position and distance in step S7.

[0059] S9. Perform power spectrum analysis on the time domain beam data in step S8 to obtain a power spectrum of the radiated noise.

[0060] S10, converting the power spectrum measured in step S9 into the sound source level of the underwater vehicle radiated noise.

[0061] Furthermore, the current environment described in step S1 requires that the sea depth meets the minimum depth requirements for the underwater vehicle to dive and the towed sonar to be deployed, the height from the bottom of the underwater vehicle and the towed sonar meets the safety indicators, there are no seabed obstacles in the surrounding sea area, and the sea condition is not greater than level 3.

[0062] Furthermore, the maneuvering mode described in step S2 includes a U-shaped maneuvering mode and a circular maneuvering mode.

[0063] Further, the calculation method in step S4 is to refer to the energy relationship in the passive sonar equation. For the line spectrum signal, the signal-to-noise ratio is

[0064] ;

[0065] For a broadband radiated noise signal, the signal-to-noise ratio is

[0066] ;

[0067] In the formula DF is the processing gain of Fourier transform for single-frequency signal, DI is the space gain, TL is the propagation loss, where:

[0068] ;

[0069] ;

[0070] ;

[0071] In the formula T To measure time, N To select the number of sonar array elements, R is the measured distance from the sound source to the receiving array.

[0072] At the same time, in order to average the results of multiple measurements to reduce errors, the measurement time needs to be increased; in order to ensure that the array is close to a linear array to the greatest extent, reduce the difficulty of array estimation and the influence of array distortion, it is necessary to select part of the array to participate in the calculation; reducing the distance between the underwater vehicle and the towed array can reduce the propagation loss, but it will shorten the stable measurement time; considering the above factors comprehensively, according to the preset signal-to-noise ratio requirements, SNR ≥3dB, calculate the reasonable measurement time , Detection duration , measure distance R Number of array elements N ,in, , n is the number of measurement segments to be averaged.

[0073] Further, the underwater vehicle maneuvering path parameter in step S5 is: Γ , towed sonar cable length L and underwater vehicle speed V ;in, .

[0074] The measurement timing is the time when the measurement starts and ends. and location , so that the underwater vehicle is located in the horizontal direction of the towed array,

[0075] ;

[0076] .

[0077] For measurement duration , Detection duration , measure distance R Number of array elements N , and the turning radius of the underwater vehicle Γ , towed sonar cable length L and underwater vehicle speed V The reasonable calculation is obtained by continuously adjusting the value combination that meets the principles described in step S4 and the restrictions described in step S5, and finally selecting the value combination according to the actual difficulty of operation.

[0078] Furthermore, in step S6, during the formation estimation measurement, the heading data measured by the heading sensors distributed at the fixed positions of the towed array are interpolated and fitted to analyze the duration. The coordinates of each sonar array element are estimated for the unit x 1 , x 2 , … , x N .

[0079] Further, in step S7, by focusing the beam forming spatial scanning method, refer to the towed array reference element to find the maximum noise energy The corresponding position θ and distance D ,like Figure 2 , i.e. the acoustic center position of the underwater vehicle ;in, is the time delay from the scanning position to each array element and the reference array element, , c is the speed of sound in seawater, (0≤ t ≤ T ) is the time domain data of each array element.

[0080] Further, in step S8, the time delay from the underwater vehicle sound center position to each array element and the reference array element is For the time domain data of each array element Time shift to obtain , add up to get the time domain beam data x ( t ), i =1,2,…, N -1, calculated as:

[0081] ;

[0082] ;

[0083] ;

[0084] Further, in step S9, steps S6-S8 are repeated until the detection time is reached. T s;like Figure 3 The signal processing flow of the hydrophone array is shown in the figure. The power spectrum of the radiated noise is obtained by segmenting the obtained time domain data and averaging it. :

[0085] .

[0086] Further, in step S10, according to the propagation loss formula, the measured power spectrum is converted to 1 meter away from the equivalent sound center of the underwater vehicle to obtain the sound source level of the underwater vehicle radiated noise , the calculation formula is:

[0087] .

[0088] Furthermore, in step S6, the method of formation estimation includes but is not limited to posture sensor difference fitting, fluid mechanics calculation and other methods.

[0089] Furthermore, in step S7, the process of searching the acoustic center by focusing beamforming may also use a frequency domain beamforming method.

[0090] Furthermore, in steps S8-S9, a frequency domain beamforming method may also be used to directly obtain a power spectrum result.

[0091] Furthermore, in steps S7-S9, when frequency domain beamforming is performed, the beamformer includes but is not limited to conventional beamforming, and other beamformers may be used as needed.

[0092] The following introduces an embodiment of the control of underwater vehicle radiated noise measurement according to the different maneuvering modes described in step S2.

[0093] Embodiment 1, the motor mode is as follows Figure 4 In the U-shaped maneuver shown, the specific operations can be performed as follows:

[0094] (1) The underwater vehicle sails straight and deploys the towed array to a certain length, with all the acoustic array segments and zero buoyancy cables deployed. The deployment length of the gravity cable is determined according to the conditions. The attitude sensor data of the towed array is observed, and the acoustic array segments are roughly in a straight line, and the depth difference before and after the acoustic array is relatively stable.

[0095] (2) The underwater vehicle maintains its speed, changes the rudder angle as quickly as possible, and performs a turning maneuver. The moment of starting to turn is T0, and the initial heading is γ;

[0096] (3) After the heading is γ+180°, keep the heading γ+180° unchanged, observe the data of the towed array attitude sensor, wait for the acoustic array segment to be in a straight line state, and the heading of the towed array differs from that of the underwater vehicle by about 180°;

[0097] (4) Observe the A display and process interface of the towed array sonar integrated display and control console, select the 500-1000 Hz processing band (#2 and #3 array segments), and check whether there is a body energy track in the direction of a small side angle and the side angle continues to increase, and perform angle tracking on the target;

[0098] (5) Observe the measurement algorithm interface of this project and solve the relative situation between the underwater vehicle and the towed array;

[0099] (6) When the underwater vehicle is located near the 90° side angle of the towed array, the measurement conditions are met.

[0100] Embodiment 2, the motor mode is as follows Figure 5 In the circular maneuver shown, the specific operation can be performed according to the following steps:

[0101] (1) The underwater vehicle sails straight and deploys the towed array to a certain length, with all the acoustic array segments deployed. The zero buoyancy cable is deployed to a certain length based on the conditions. The attitude sensor data of the towed array is observed, and the acoustic array segments are roughly in a straight line state, and the depth difference between the front and rear of the acoustic array is relatively stable.

[0102] (2) The underwater vehicle maintains its speed and gradually changes the rudder angle to β, then performs a circular maneuver at the rudder angle β. The rudder angle is determined by the turning radius. The moment of starting the turn is T0, and the initial heading is γ.

[0103] (3) After the heading is γ+180°, observe the towed array attitude sensor data, wait for the depth difference between the front and rear of the acoustic array to be relatively stable, and for the acoustic array segment to present a relatively stable arc;

[0104] (4) Observe the A-display and process interface of the towed array sonar integrated display and control console, select the 500-1000 Hz processing band, and check whether there is a body energy track in the direction of about 90° at a side angle and whether it remains stable; if conditions permit, perform angle tracking on the target;

[0105] (5) Observe the measurement algorithm interface of this project to see whether the distance between the underwater vehicle and the towed array remains stable and the relative side angle is about 90°;

[0106] (6) If the distance between the underwater vehicle and the towed array remains stable and the relative beam angle is approximately 90°, the measurement conditions are met.

[0107] Obviously, the above embodiments are merely examples for clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention. It is easy for those skilled in the art to understand that the above description is only a preferred embodiment of the invention, and is not intended to limit the invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the invention should be included in the scope of protection of the invention.

Claims

1. A real-time self-measurement and evaluation method for underwater radiated noise of an aircraft, characterized in that: The underwater radiated noise of the underwater vehicle is measured in real time using the underwater vehicle's own towed sonar. The following steps are performed in sequence: S1. Determine whether the current environment is suitable for deploying towed sonar and measuring radiated noise; S2. Determine the maneuvering method to be adopted for measurement according to the task requirements; S3. Determine the background noise level based on the measured ocean ambient noise and sonar flow noise levels NL , determine the sound source level based on the predicted underwater vehicle radiated noise level SL; S4, the background noise level in step S3 NL and sound source level SL Substitute into the sonar equation to calculate the appropriate underwater vehicle radiated noise measurement time T , measure distance R And the number of sonar array elements selected N ; S5. According to the underwater vehicle control theory and the length of the underwater vehicle d， Sonar array size h , determine the underwater vehicle maneuvering route parameters and measurement timing; S6, performing formation estimation and calculating the coordinates of the towed array sonar elements; S7, determining the position and distance of the underwater vehicle by focusing beamforming spatial scanning according to the parameters determined in steps S4-S6; S8, calculating time domain beam data according to the underwater vehicle position and distance in step S7; S9, performing power spectrum analysis on the time domain beam data to obtain a power spectrum of the radiated noise; S10, converting the power spectrum measured in step S9 into the sound source level of the underwater vehicle radiated noise.

2. The method according to claim 1, characterized in that: The current environment described in step S1 requires that the sea depth meets the minimum depth requirements for the underwater vehicle to dive and the towed sonar to be deployed, the height from the bottom of the underwater vehicle and the towed sonar meets the safety indicators, there are no seabed obstacles in the surrounding sea area, and the sea condition is not greater than level 3.

3. The method according to claim 2, characterized in that: The maneuvering mode described in step S2 includes a U-shaped maneuvering mode and a circular maneuvering mode.

4. The method according to claim 3, characterized in that: The calculation method in step S4 is to refer to the energy relationship in the passive sonar equation. For the line spectrum signal, the signal-to-noise ratio is ； For a broadband radiated noise signal, the signal-to-noise ratio is ； In the formula DF is the processing gain of Fourier transform for single-frequency signal, DI is the space gain, TL is the propagation loss, where: ； ； ； In the formula T To measure time, N To select the number of sonar array elements, R is the measurement distance from the sound source to the receiving array; At the same time, in order to average the results of multiple measurements to reduce errors, the measurement time needs to be increased; in order to ensure that the array is close to a linear array to the greatest extent, reduce the difficulty of array estimation and the influence of array distortion, it is necessary to select part of the array to participate in the calculation; reducing the distance between the underwater vehicle and the towed array can reduce the propagation loss, but it will shorten the stable measurement time; considering the above factors comprehensively, according to the preset signal-to-noise ratio requirements, SNR ≥3dB, calculate the reasonable measurement time , Detection duration , measure distance R Number of array elements N ,in, , n is the number of measurement segments to be averaged.

5. The method according to claim 4, characterized in that: The underwater vehicle maneuvering path parameters in step S5 are: Γ , towed sonar cable length L and underwater vehicle speed V ;in, ; The measurement timing is the time when the measurement starts and ends ( ) and location ( ), so that the underwater vehicle is located in the horizontal direction of the towed array, ； 。 6. The method according to claim 5, characterized in that In step S6, during the formation estimation measurement, the heading data measured by the heading sensors distributed at the fixed positions of the towed array are interpolated and fitted to measure the time The coordinates of each sonar array element are estimated for the unit x 1 , x 2 , … , x N .

7. The method according to claim 6, characterized in that In step S7, the maximum noise energy is found by focusing the beam forming spatial scanning method and referring to the reference array element of the towed array. The corresponding position θ and distance D , i.e. the acoustic center position of the underwater vehicle ;in, is the time delay from the scanning position to each array element and the reference array element, , c is the speed of sound in seawater, is the time domain data of each array element, and 0≤ t ≤ T .

8. The method according to claim 7, characterized in that: In step S8, the time delay from the underwater vehicle sound center position to each array element and the reference array element is For the time domain data of each array element Time shift to obtain , add up to get the time domain beam data x ( t ), i =1,2,…, N -1, calculated as: ； ； 。 9. The method according to claim 8, characterized in that In step S9, repeat steps S6-S8 until the detection time is reached. T s ; Perform power spectrum analysis on the obtained time domain data in segments and take the average to obtain the power spectrum of the radiated noise : 。 10. The method according to claim 9, characterized in that In step S10, the measured power spectrum is converted to 1 meter from the equivalent sound center of the underwater vehicle according to the propagation loss formula to obtain the sound source level of the underwater vehicle radiated noise. , the calculation formula is: 。

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