A large-scale flat plate type underwater member target strength measurement method and device

Abstract

The application discloses a large-scale flat plate type underwater component target strength measurement method and device, which comprises a high-frequency transducer for acoustic ranging and lateral measurement; a signal generator for generating specific acoustic signals; a low-frequency power amplification module for amplifying low-frequency electric signals; a high-frequency power amplification module for amplifying radio frequency signals; a low-frequency transducer for generating acoustic signals for testing; a hydrophone for measuring acoustic signals; and a lifting and rotating mechanism for lifting and rotating the underwater component. The application breaks the original underwater target strength measurement and underwater acoustic signal processing thought, can greatly reduce the lower limit of the free field test frequency of the large-scale flat plate type underwater component, and facilitates the measurement of the target strength of the large-scale flat plate type underwater component.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of acoustic measurement and testing, and particularly relates to a large-scale flat plate type underwater member target strength measurement method and device. BACKGROUND

[0002] Underwater acoustic stealth technology refers to a series of technical measures taken to reduce the radiated noise and acoustic target strength of equipment. Acoustic stealth technology can not only reduce the distance and probability of being discovered by the enemy, but also improve the ability to detect the enemy. With the rapid development of submarine vibration and noise reduction technology, the radiated noise of the submarine tends to be close to zero sea state, and the effective distance of passive detection is greatly shortened. Low-frequency active detection has become the main means of detecting submarines.

[0003] Submarines and other underwater navigation equipment are generally hollow shell structures. In order to achieve active acoustic stealth function, a large amount of sound-absorbing materials such as sound-absorbing tiles and stealth clothes are often laid on the outer shell, which have good sound-absorbing effect on acoustic waves with a frequency above kilohertz (kHz). As an important part of underwater navigation equipment, the rudder wing structure is also a key factor affecting its acoustic stealth performance. The rudder wing structure is similar to a flat plate structure in appearance and has a large size in the mid-longitudinal section, thereby forming a large acoustic scattering cross section, which makes the ship easy to be detected by sonar devices and reduces the concealment of the ship. In order to increase the acoustic stealth performance of the rudder, the structure of the rudder is often optimized during the development process, and composite materials are also applied to the structural design to further reduce the acoustic scattering of the rudder wing. On the other hand, during the development of stealth clothes and sound-absorbing tiles, a flat plate is often selected as a backing to test the acoustic performance of the flat plate after wearing the stealth clothes and sound-absorbing tiles, thereby evaluating the acoustic stealth performance of the stealth clothes and sound-absorbing tiles.

[0004] Target strength is an important parameter for evaluating the active acoustic stealth capability of flat plate type underwater members. Due to the large size of the flat plate type underwater member, the far-field distance of the test is far, so the target strength is generally measured in large open waters such as lakes and seas. However, the sound field environment of natural waters such as lakes and seas is complex, and underwater positioning is difficult. Especially for flat plate type members, the spatial directivity of the scattered sound field is very sharp, and the target strength of large-scale flat plate type underwater members changes by tens of decibels in a very small angle range. It can be seen that determining the underwater attitude of large-scale flat plate type underwater members is a difficult problem that needs to be overcome in target strength measurement technology. In addition, during low-frequency testing, the wavelength of the acoustic wave is large, and it is difficult to separate the interface reflected sound signal and the scattered sound signal in the time domain, which further increases the difficulty of target strength measurement of large-scale flat plate type underwater members. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a large-scale flat plate type underwater member target strength measurement method and device, which solves the above technical problem and breaks the original underwater target strength measurement and underwater acoustic signal processing thought, and can greatly reduce the lower limit of the free field test frequency of the large-scale flat plate type underwater member, and facilitate the measurement of the target strength of the large-scale flat plate type underwater member.

[0006] The technical solution of the present application is to provide a large-scale flat plate type underwater member target strength measurement device, comprising

[0007] A high-frequency transducer is used for acoustic ranging and lateral;

[0008] A signal generator is used to generate a specific acoustic signal;

[0009] A low-frequency power amplification module is used for amplifying low-frequency electrical signals;

[0010] A high-frequency power amplification module is used for amplifying radio frequency signals;

[0011] A low-frequency transducer is used to generate a test acoustic signal;

[0012] A hydrophone is used to measure the acoustic signal;

[0013] A lifting and rotating mechanism is used for lifting and rotating the underwater member;

[0014] A signal processing machine is used for processing acoustic signals.

[0015] As a preferred, the number of high-frequency transducers is not less than 4, and they are fixedly installed on the large-scale flat plate type underwater member; the high-frequency transducer is a planar piston type, and its resonance frequency is not less than 100 kHz, and the -6dB beam width is less than 10°.

[0016] As a preferred, the determination method of the installation position of the high-frequency transducer is as follows:

[0017] Taking the center of gravity of the large-scale flat plate type underwater member as the center, find the largest rectangle, and draw two center axis symmetry lines;

[0018] At least 4 points are found on the center axis symmetry line, which are symmetric about the center axis of the rectangle, and the high-frequency transducer is installed and fixed at the above-mentioned points.

[0019] As a preferred, the hydrophone has at least 3, wherein

[0020] The hydrophone without preamplifier is at the same water depth as the acoustic center of the low-frequency transducer, and is used to measure the incident acoustic wave and the high-frequency acoustic wave emitted by the high-frequency transducer;

[0021] The hydrophone two-band preamplifier is arranged between the low-frequency transducer and the large-scale flat underwater member, and the acoustic centers of the hydrophone two, the low-frequency transducer and the large-scale flat underwater member are on the same straight line, and is used for measuring the scattered acoustic waves and the high-frequency acoustic waves emitted by the high-frequency transducer.

[0022] The hydrophone three is a high-frequency hydrophone, which is fixed at the middle part of the low-frequency transducer, and is used for receiving the high-frequency acoustic waves emitted by the high-frequency transducer.

[0023] Preferably, the low-frequency transducer is omnidirectional in the horizontal direction, the bandwidth is not less than 50% of the resonant frequency, and the sending voltage response is not less than 120 dB.

[0024] Further, the application also provides a large-scale flat underwater member target strength measurement method, which comprises the following steps,

[0025] Step one, the hydrophone, the low-frequency transducer and the large-scale flat member are put into water, and the low-frequency transducer and the hydrophone are adjusted so that the acoustic centers of the large-scale flat underwater member, the low-frequency transducer and the hydrophone are on the same straight line;

[0026] Step two, the distance L between the center of the large-scale flat underwater member and the hydrophone one is determined h1

[0027] Step three, the signal generator and the low-frequency power amplification module are set to generate a high-power electrical signal to excite the low-frequency transducer to generate a low-frequency sinusoidal pulse acoustic signal with a pulse width of T0, and the acoustic signal acts on the large-scale flat underwater member to generate acoustic scattering signals;

[0028] Step four, the amplitude of the signal generator is adjusted so that the sound pressure level of the scattering acoustic signal is higher than the underwater background noise level by more than 20 dB;

[0029] Step five, the hydrophone one and the hydrophone two receive the acoustic signals generated by the low-frequency transducer and the large-scale flat underwater member, and transmit them to the signal processing machine, and the signal processing machine obtains the time t1 and t2 of the acoustic wave propagating from the low-frequency transducer to the hydrophone one and the hydrophone two, respectively, through signal processing, and performs Fourier transform on the received signal of the hydrophone one and takes the logarithm to obtain

[0030]

[0031] In the formula, The Fourier transform of the signal is represented; s1(t) is the acoustic signal received by the hydrophone 1;

[0032] Step six, take out the large-scale flat plate underwater structure, according to the electrical signal generated in step three to stimulate the low-frequency transducer to generate acoustic signals, received by hydrophone two, and transmitted to the signal processor, the signal processor processes the acoustic signals received by the hydrophone to obtain

[0033]

[0034] In the formula, s2(t) is the acoustic signal received by hydrophone two, the starting time of the signal is t2, and the signal duration is 2T0;

[0035] Step seven, through the signal processor to process S'1(ω) and S'2(ω) in (5) and (6) to obtain

[0036]

[0037] Indicates the inverse Fourier transform of the signal. Then the target strength of the large-scale flat plate underwater structure is

[0038]

[0039] In the formula, ΔM is the difference between the sensitivities of hydrophone 1 and hydrophone 2.

[0040] As preferred, in step one, the method for adjusting the low-frequency transducer and the hydrophone so that the acoustic centers of the large-scale flat plate underwater structure, the low-frequency transducer and the hydrophone are located on the same straight line is as follows,

[0041] (1) The high-frequency transducer generates an acoustic pulse signal, which is received by the hydrophone and transmitted to the signal processor;

[0042] (2) The signal processor calculates the time required for the acoustic wave to be transmitted from the position of the high-frequency transducer to the position of the hydrophone;

[0043] (3) The distance between the hydrophone and the center of gravity of the large-scale flat plate underwater structure is

[0044]

[0045] Wherein, L1 is the distance between the acoustic centers of the two high-frequency transducers on the center axis, L2=cτ1, L2 is the distance between the high-frequency transducer at one end of the center axis and the hydrophone, τ1 is the time for the acoustic wave to be transmitted from the position of the high-frequency transducer at one end of the center axis to the position of the hydrophone, c is the speed of sound in water; L3=cτ2, L3 is the distance between the high-frequency transducer at the other end of the center axis and the hydrophone, τ2 is the time for the acoustic wave to be transmitted from the position of the high-frequency transducer at the other end of the center axis to the position of the hydrophone; The calculation formula of θ is

[0046]

[0047] (4) Calculate the distance L5 and L6 between the two high frequency transducers and the hydrophone on the other central axis, and get the horizontal azimuth angle of the hydrophone relative to the large-scale flat underwater structure and the vertical azimuth angle respectively

[0048]

[0049] and

[0050]

[0051] wherein, L4 is the distance between the sound centers of the two high frequency transducers on the central axis; L5 is mainly used to verify whether the two high frequency transducers are symmetric about the center of the flat, and the distance between the hydrophone and the center of gravity of the large-scale flat underwater structure is calculated by using the values of L5 and L6 in the manner of (3) above, if it is consistent with the result in (3), it indicates that the two high frequency transducers are symmetric about the center of the flat. It should be noted that in step two, the distance L h1 between the center of the large-scale flat underwater structure and the hydrophone 1 can be determined by the same method.

[0052] (5) Adjust the spatial position of the hydrophone and the low frequency transducer by the horizontal azimuth angle and the vertical azimuth angle .

[0053] (1)-(4) in the above steps are the methods of distance measurement and orientation by high frequency transducers.

[0054] As preferred, the method of adjusting the spatial position of the hydrophone and the low frequency transducer by the horizontal azimuth angle and the vertical azimuth angle is as follows,

[0055] Move the hydrophone horizontally by the lifting and rotating mechanism, and the distance of the horizontal translation of the hydrophone is

[0056]

[0057] If x H is positive, translate to the right, otherwise translate to the left.

[0058] Move the hydrophone vertically by the lifting and rotating mechanism, and the distance of the vertical translation of the hydrophone is

[0059]

[0060] If x V is positive, translate downward, otherwise translate upward.

[0061] After the horizontal and vertical translation, the hydrophone will be located on the acoustic axis of the flat plate underwater structure. Similarly, the hydrophone is fixed in the middle of the low frequency transducer, and by translating the low frequency transducer in the horizontal and vertical directions, the low frequency transducer is on the acoustic axis of the flat plate underwater structure.

[0062] Compared with the prior art, the present application has the following advantages:

[0063] The present application accurately monitors the underwater space posture of the large-scale flat plate underwater structure by using multiple high-frequency transducers, measures the incident sound signals and scattered sound signals by using two high and low sensitivity hydrophones respectively, processes the sound signals with and without the flat plate underwater structure, and finally obtains the target strength of the large-scale flat plate underwater structure. The original underwater target strength measurement and underwater acoustic signal processing ideas are broken, and the lower limit of the free field test frequency of the large-scale flat plate underwater structure can be greatly reduced. BRIEF DESCRIPTION OF DRAWINGS

[0064] Figure 1 The present application is a structural block diagram of a large-scale flat plate underwater structure target strength measurement device.

[0065] Figure 2 The present application is a large-scale flat plate underwater structure target strength measurement sound field layout diagram.

[0066] Figure 3 The present application is a high-frequency transducer installation position diagram.

[0067] Figure 4 The present application is a geometric position diagram of the hydrophone and the high-frequency transducer.

[0068] Figure 5 A(t) is a curve varying with time t. DETAILED DESCRIPTION

[0069] The present application will be further described in conjunction with the specific embodiments and the accompanying drawings:

[0070] A large-scale flat plate underwater structure target strength measurement device determines the spatial posture of the underwater structure by using high-frequency acoustic transducers, measures incident sound waves and scattered sound waves by using multiple hydrophones, separates scattered sound waves and interface reflected sound waves by using acoustic signal processing methods, and realizes low-frequency measurement of the target strength of the large-scale flat plate underwater structure. The device mainly includes:

[0071] High-frequency transducers for acoustic ranging and lateral;

[0072] Signal generator for generating specific sound signals;

[0073] Low-frequency power amplification module for amplifying low-frequency electrical signals;

[0074] High-frequency power amplifier module, used for amplifying radio frequency signals;

[0075] Low-frequency transducers are used to generate acoustic signals for testing.

[0076] Hydrophones are used to measure sound wave signals;

[0077] A lifting and rotating mechanism is used for lifting and rotating underwater components;

[0078] A signal processor is used for processing audio signals.

[0079] This embodiment uses a 4m×1.5m×0.1m stainless steel plate as the test object for a large-scale flat underwater component, and the device of the present invention is described as follows.

[0080] like Figure 1 As shown, one channel of the signal generator 12 is connected to the low-frequency power amplifier module 13, which together drive the low-frequency transducer 1 to generate low-frequency sinusoidal pulse sound waves in the water. The other channel of the signal generator 12 is connected to the high-frequency power amplifier 14, which together drive the high-frequency transducers 5, 6, 7, and 8 to generate high-frequency sound signals. All four high-frequency transducers are fixedly mounted on the stainless steel plate 9.

[0081] like Figure 3 As shown, high-frequency transducer 5 and high-frequency transducer 7 are on the same central axis and are symmetrical about the center point 10 of the stainless steel plate 9. The acoustic centers of high-frequency transducer 5 and high-frequency transducer 7 are 1m apart. Similarly, high-frequency transducer 6 and high-frequency transducer 8 are on the same central axis and are also symmetrical about the center point 10. The acoustic centers of high-frequency transducer 6 and high-frequency transducer 8 are 1m apart.

[0082] The signal processor 11 is connected to the lifting and rotating mechanism 15, controlling the lifting and rotating of the mechanism 15. The signal processor 11 is also connected to the signal generator 12, controlling it to generate electrical signals of different frequencies in two channels. The signal output terminals of hydrophones 2, 3, and 4 are connected to the signal processor 11. Hydrophone 2 is fixedly installed in the middle of the low-frequency transducer 1. The signal processor 11 generates control commands, causing the signal generator 12 to generate an electrical signal with a frequency of 180kHz. This signal is amplified by the high-frequency power amplifier 14 and applied to the ends of high-frequency transducers 5, 6, 7, and 8, generating a 180kHz pulse sound signal in the water, which is received by hydrophones 2 and 3.

[0083] The low frequency transducer 1, the hydrophone three 2, the hydrophone two 3, the hydrophone one 4 and the stainless steel plate 9 are placed in water at a depth of 35 m, the hydrophone two 3 is located between the low frequency transducer 1 and the stainless steel plate 9, the hydrophone three 2 faces the stainless steel plate 9, the water depth of the hydrophone one 4 is consistent with that of the hydrophone two 3, and the leveler two 3 and the hydrophone one 4 are both located in the far field of the low frequency transducer 1. The stainless steel plate 9 is rotated by the lifting and rotating mechanism 15, so that the hydrophone three 2 and the hydrophone two 3 can receive the high frequency pulse sound signals generated by the four high frequency transducers, i.e., the high frequency transducer one 5, the high frequency transducer two 6, the high frequency transducer three 7 and the high frequency transducer four 8. The signal processing machine 11 calculates the time τ required for the sound waves generated by the above four high frequency transducers to propagate to the hydrophone three 2 and the hydrophone two 3 through the rising edge algorithm 25 、τ 26 、τ 27 、τ 28 、τ 35 、τ 36 、τ 37 、τ 38 The distance between the center point 10 and the hydrophone three 2 is calculated as

[0084]

[0085] The calculation formula of θ2 is

[0086]

[0087] The distance between the center point 10 and the hydrophone two 3 is calculated as

[0088]

[0089] The calculation formula of θ3 is

[0090]

[0091] Further, the horizontal azimuth angle of the hydrophone three 2 relative to the stainless steel plate 9 is calculated as

[0092]

[0093] The vertical azimuth angle of the hydrophone three 2 relative to the stainless steel plate 9 is calculated as

[0094]

[0095] The hydrophone three 2 is moved along the horizontal direction by

[0096]

[0097] When x 2H > 0, the hydrophone three 2 is moved rightward by |x 2HOtherwise, move left |x 2H .

[0098] Move hydrophone three 2 along vertical direction

[0099]

[0100] When x 2V > 0, move down |x 2V , otherwise, move up |x 2V .

[0101] Further, the horizontal azimuth angle of hydrophone two 3 relative to stainless steel plate 9 is calculated as

[0102]

[0103] The vertical azimuth angle of hydrophone two 3 relative to stainless steel plate 9 is calculated as

[0104]

[0105] Move hydrophone two 3 along horizontal direction

[0106]

[0107] When x 3H > 0, move right |x 3H , otherwise, move left |x 3H .

[0108] Move hydrophone two 3 along vertical direction

[0109]

[0110] When x 3V > 0, move down |x 3V , otherwise, move up |x 3V .

[0111] The control command is generated by signal processing machine 11, so that signal generator 12 generates radio frequency pulse electric signal, which is power amplified by high frequency power amplifier 14, and then excites high frequency transducer one 5 and high frequency transducer three 7 to generate high frequency pulse acoustic signal. Signal processing machine 11 calculates the time τ' required for the sound wave to propagate from high frequency transducer one 5 and high frequency transducer three 7 to hydrophone two 3 through rising edge detection algorithm. 35 τ' 37 At this time, there should be τ' 35 = τ' 37 , and the distance between hydrophone two 3 and center point 10 is calculated as

[0112]

[0113] wherein,

[0114]

[0115] The signal generator 12 generates a low-frequency sinusoidal pulse electric signal under the control of the signal processor 11, and the low-frequency power amplifier module 13 amplifies the power of the signal to load on both ends of the low-frequency transducer 1, and excite the low-frequency transducer 1 to generate a low-frequency sinusoidal pulse acoustic signal in water. The frequency of the acoustic signal is 250Hz, and the pulse width is 12ms. Adjust the amplitude of the signal generator 12 so that the sound pressure level of the scattered acoustic signal is 20dB higher than the underwater background noise level. The hydrophone two 3 and the hydrophone one 4 respectively receive the acoustic signal and transmit it to the signal processor 11. The signal processor 11 obtains the time t1 and t2 of the acoustic wave propagating from the low-frequency transducer to the hydrophone two 3 and the hydrophone one 4 respectively through the rising edge detection algorithm. The received acoustic signal of the hydrophone one 4 is subjected to Fourier transform and logarithm to obtain

[0116]

[0117] Take out the stainless steel plate 9 in the same emission state, so that the transducer generates an acoustic signal with a frequency of 250Hz and a pulse width of 12ms, which is received by the hydrophone two 3 and transmitted to the signal processor 11. The signal processor 11 processes the acoustic signal to obtain

[0118]

[0119] The starting time of the signal s2(t) is t2, and the signal length is 2T0. It is worth noting that when the Fourier transform of s2(t) is performed, the signal needs to be zero-padded so that the signal length of s2(t) is consistent with that of s1(t).

[0120] Further calculation obtains,

[0121]

[0122] Figure 5 A(t) is the curve of the change of A(t) with time t. Through calculation, it is found that there is a large-size flat plate underwater component scattering acoustic signal at 16.2ms.

[0123] Finally, the target strength of the stainless steel plate 9 is obtained as

[0124]

[0125] In the formula, ΔM is the difference between the sensitivities of the hydrophone two 3 and the hydrophone one 4.

[0126] The above description is only for the preferred embodiments of the present application, and should not be understood as a limitation to the claims. Any equivalent structure or equivalent process transformation made by using the present application description shall be included in the patent protection scope of the present application.

Claims

1. A large-scale flat-plate underwater component target strength measuring device, characterized in that: include High-frequency transducers are used for acoustic ranging and lateral positioning. A signal generator is used to produce specific sound wave signals; Low-frequency power amplifier module, used for amplifying low-frequency electrical signals; High-frequency power amplifier module, used for amplifying radio frequency signals; Low-frequency transducers are used to generate acoustic signals for testing. Hydrophones are used to measure sound wave signals; A lifting and rotating mechanism is used for lifting and rotating underwater components; A signal processor is used for processing audio signals. There are at least three hydrophones, among which, A hydrophone without a preamplifier is placed at the same water depth as the acoustic center of the low-frequency transducer and is used to measure the incident sound wave and the high-frequency sound wave emitted by the high-frequency transducer. Hydrophone 2 with a preamplifier is placed between the low-frequency transducer and the large-scale flat underwater component, with the acoustic centers of hydrophone 2, the low-frequency transducer and the large-scale flat underwater component on the same straight line, used to measure the scattered sound waves and the high-frequency sound waves emitted by the high-frequency transducer. Hydrophone number three is a high-frequency hydrophone, fixed in the middle of the low-frequency transducer, used to receive high-frequency sound waves emitted by the high-frequency transducer.

2. The large-scale flat underwater component target strength measuring device according to claim 1, characterized in that: There are no fewer than four high-frequency transducers, all of which are fixedly installed on a large-scale flat underwater structure. The high-frequency transducers are planar piston type, and their resonant frequency is not less than 100kHz, and their -6dB beamwidth is less than 10°.

3. The large-scale flat-plate underwater component target strength measuring device according to claim 2, characterized in that: The method for determining the installation location of a high-frequency transducer is as follows: Using the center of gravity of the large-scale flat underwater component as the center, find the largest rectangle and draw two lines of symmetry along the central axis; Find at least four points on the central axis of symmetry, each pair of which is symmetrical about the central axis of the rectangle, and install fixed high-frequency transducers at these points.

4. The large-scale flat underwater component target strength measuring device according to claim 1, characterized in that: The low-frequency transducer is omnidirectional in the horizontal direction, with a bandwidth of not less than 50% of the resonant frequency and a transmission voltage response of not less than 120dB.

5. A method for measuring the strength of a large-scale flat underwater component, characterized in that: Includes the following steps, Step 1: Place the hydrophone, low-frequency transducer, and large-scale flat panel component into the water, and adjust the low-frequency transducer and hydrophone so that the acoustic centers of the large-scale flat panel underwater component, low-frequency transducer, and hydrophone are on the same straight line. Step 2: Determine the distance L between the center of the large-scale flat underwater component and hydrophone 1. h1 Step 3: Set up a signal generator and a low-frequency power amplifier module to generate a high-power electrical signal, which excites the low-frequency transducer to generate a low-frequency sinusoidal pulse acoustic signal with a pulse width of T0. The acoustic signal acts on the large-scale flat underwater structure and generates an acoustic scattering signal. Step 4: Adjust the amplitude of the signal generator so that the sound pressure level of the scattered sound signal is more than 20dB higher than the underwater background noise level; Step 5: Hydrophone 1 and Hydrophone 2 receive the acoustic signals generated by the low-frequency transducer and the large-scale flat underwater component, and transmit them to the signal processor. The signal processor processes the signals to obtain the time t1 and t2 for the sound wave to travel from the low-frequency transducer to Hydrophone 1 and Hydrophone 2, respectively. It then performs a Fourier transform on the received signal from Hydrophone 1 and takes its logarithm to obtain... In the formula, The Fourier transform of the signal is represented; s1(t) is the acoustic signal received by hydrophone 1; Step Six: Remove the large-scale flat underwater component. Excite the low-frequency transducer to generate an acoustic signal according to the electrical signal produced in Step Three. This signal is received by hydrophone 2 and transmitted to the signal processor. The signal processor processes the received acoustic signal from the hydrophone to obtain... In the formula, s2(t) is the acoustic signal received by hydrophone 2, the start time of the signal is t2, and the signal duration is 2T0; Step 7: Process S′1(ω) and S′2(ω) in (5) and (6) using a signal processor to obtain... Representing the inverse Fourier transform of the signal, the target strength of a large-scale flat underwater component is: In the formula, ΔM is the difference in sensitivity between hydrophone one and hydrophone two.

6. The method for measuring the target strength of large-scale flat underwater components according to claim 5, characterized in that: In step one, the method for adjusting the low-frequency transducer and hydrophone so that the acoustic centers of the large-scale flat underwater component, the low-frequency transducer, and the hydrophone are on the same straight line is as follows: (1) The high-frequency transducer generates an acoustic pulse signal, which is received by the hydrophone and transmitted to the signal processor. (2) The signal processor calculates the time required for the sound wave to travel from the location of the high-frequency transducer to the location of the hydrophone. (3) The distance between the hydrophone and the center of gravity of the large-scale flat underwater component is: Where L1 is the distance between the sound centers of the two high-frequency transducers on the central axis; L2 = cτ1, where L2 is the distance between the high-frequency transducer at one end of the central axis and the hydrophone, τ1 is the time it takes for the sound wave to travel from the position of the high-frequency transducer at one end of the central axis to the position of the hydrophone, and c is the speed of sound in water; L3 = cτ2, where L3 is the distance between the high-frequency transducer at the other end of the central axis and the hydrophone, and τ2 is the time it takes for the sound wave to travel from the position of the high-frequency transducer at the other end of the central axis to the position of the hydrophone; the formula for calculating θ is... (4) Calculate the distances L5 and L6 between the two high-frequency transducers and the hydrophone on the other central axis to obtain the horizontal azimuth angle of the hydrophone relative to the large-scale flat underwater component. With vertical azimuth They are respectively and Where L4 is the distance between the acoustic centers of the two high-frequency transducers on the central axis; (5) By horizontal azimuth angle With vertical azimuth Adjust the spatial position of the hydrophone and the low-frequency transducer.

7. The method for measuring the target strength of large-scale flat underwater components according to claim 6, characterized in that: The horizontal azimuth angle With vertical azimuth The method for adjusting the spatial position of the hydrophone and the low-frequency transducer is as follows. The hydrophone is moved horizontally by a lifting and rotating mechanism. The distance the hydrophone moves horizontally is... If x H If the value is positive, shift to the right; otherwise, shift to the left. The hydrophone is moved vertically by a lifting and rotating mechanism; the distance the hydrophone moves vertically is... If x V If the value is positive, shift downwards; otherwise, shift upwards.

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