An in-situ measurement system and method for low-frequency acoustic characteristics of seabed sediments

Abstract

The present invention discloses an in-situ measurement system and method for low-frequency acoustic characteristics of seabed sediments, comprising a load-bearing frame, a control cabin, a hydraulic cabin, a vertical probe penetration mechanism and a horizontal probe support mechanism, a lifting ring is provided at the top of the load-bearing frame, and two receiving transducers are fixedly provided at the bottom of the vertical probe at intervals; the horizontal probe support mechanism comprises a driving device fixedly provided on the load-bearing frame, the output shaft of the driving device is perpendicular to and fixedly connected to one end of the horizontal probe, the driving device can drive the horizontal probe to rotate with the output shaft as the central axis, and a transmitting transducer is provided at the other end of the horizontal probe; a control circuit is provided in the control cabin, a penetration oil cylinder pressure sensor electrically connected to the control circuit is provided in the hydraulic cabin, and the control circuit is electrically connected to the display and control system through a cable. The present invention realizes the in-situ measurement of the propagation characteristics of low-frequency and medium-frequency sound waves in sediments.

Description

Technical Field

[0001] The present invention relates to the technical field of seabed measurement equipment, and in particular to an in-situ measurement system and method for low-frequency acoustic characteristics in seabed sediments. Background Art

[0002] The seabed is an important boundary of the underwater sound field. The acoustic characteristics of the seabed have an important influence on the propagation law of sound waves in seawater and the spatial structure of the underwater sound field. The measurement and research of the acoustic characteristics of the seabed has important application value in military, marine science and production fields such as ocean sound field prediction, underwater target detection, underwater communication and navigation, seabed topography mapping and seabed resource exploration. There are two main direct measurement methods for the acoustic characteristics of the seabed. There are two types of direct measurement methods: laboratory measurement of sediment samples and in-situ measurement of the seabed. The in-situ measurement of seabed sediment acoustics is to place the acoustic instrument on the seabed and directly measure the propagation characteristics of sound waves in the sediment. This method avoids the disturbance of the sediment caused by sample sampling and transportation, and the surrounding environment has not changed. Therefore, the measurement results are more accurate and reliable than measuring samples in the laboratory.

[0003] The currently used in-situ measurement systems for the acoustic properties of seabed sediments, whether using lateral or longitudinal measurement methods, can only measure the propagation characteristics of high-frequency sound waves in sediments, but cannot measure the propagation characteristics of medium and low-frequency sound waves in sediments. Summary of the invention

[0004] The purpose of the present invention is to provide an in-situ measurement system and method for low-frequency acoustic characteristics of seabed sediments, so as to solve the problems existing in the above-mentioned prior art and realize the measurement of the propagation characteristics of low-frequency sound waves in sediments.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] The present invention provides an in-situ measurement system for low-frequency acoustic characteristics of seabed sediments, comprising a load-bearing frame, wherein a control cabin, a hydraulic cabin, a vertical probe rod penetration mechanism and a horizontal probe rod support mechanism are arranged in the load-bearing frame, wherein the vertical probe rod mechanism comprises a vertical guide rail fixedly arranged on the load-bearing frame, wherein a penetration oil cylinder is fixedly arranged at the top end of the guide rail, wherein the oil cylinder rod of the penetration oil cylinder is fixedly connected to a slider, wherein the slider is slidably matched with the guide rail, wherein a movable clamping oil cylinder is fixedly arranged on the slider, wherein a fixed clamping oil cylinder is fixedly arranged at the bottom end of the guide rail, wherein the movable clamping oil cylinder and the fixed clamping oil cylinder respectively clamp the same vertical probe rod, wherein the bottom end of the vertical probe rod is fixedly provided with two upper and lower spaced-apart cylinders. The receiving transducer is capable of driving the vertical probe rod to be lifted or lowered; the horizontal probe rod supporting mechanism comprises a driving device fixedly mounted on the bearing frame, the output shaft of the driving device is perpendicular to and fixedly connected to one end of the horizontal probe rod, the driving device can drive the horizontal probe rod to rotate with the output shaft as the central axis, a transmitting transducer is arranged at the other end of the horizontal probe rod, the transmitting transducer is a medium and low frequency sound wave transmitting transducer, and the receiving transducer can receive medium and low frequency sound waves; a control circuit is arranged in the control cabin, a penetration cylinder pressure sensor electrically connected to the control circuit is arranged in the hydraulic cabin, and the control circuit is electrically connected to the display and control system through a cable.

[0007] Preferably, a lifting cylinder is also provided on the horizontal probe rod, the cylinder rod of the lifting cylinder is perpendicular to the horizontal probe rod, the transmitting transducer is fixedly connected to the cylinder rod of the lifting cylinder, and the lifting cylinder can drive the transmitting transducer to move up and down.

[0008] Preferably, the horizontal probe rod supporting mechanism also includes a horizontal position limiting bracket and a vertical position limiting plate, the driving device is a hydraulic motor, the horizontal position limiting bracket is fixed on the supporting frame, and the hydraulic motor is fixed on the horizontal position limiting bracket; a receiving hole is provided at the top end of the supporting bracket corresponding to the horizontal probe rod, and the receiving hole is provided with a notch, and the horizontal probe rod passes through the receiving hole when in a vertical state, and the vertical position limiting plate is detachably installed at the notch by bolts.

[0009] Preferably, the hydraulic cabin is sealed, and is further provided with a penetration cylinder pressure sensor, a hydraulic motor pressure sensor and a lifting cylinder pressure sensor which are electrically connected to the control circuit respectively; the control cabin is sealed, and is further provided with a posture sensor which is electrically connected to the control circuit; the slider is provided with a displacement sensor which is electrically connected to the control circuit, and the output shaft of the hydraulic motor is provided with an angle sensor which is electrically connected to the control circuit.

[0010] Preferably, a plurality of feet are provided at the bottom end of the load-bearing frame, a lifting ring is provided at the top end of the load-bearing frame, and the load-bearing frame, the lifting ring and the feet constitute a load-bearing platform.

[0011] Preferably, the transmitting transducer is electrically connected to the sound wave transmitting circuit in the control circuit, and the receiving transducer is electrically connected to the sound wave receiving circuit in the control circuit.

[0012] The present invention also provides an in-situ measurement method for low-frequency acoustic characteristics of seabed sediments. The in-situ measurement system for low-frequency acoustic characteristics of seabed sediments comprises the following steps:

[0013] (1) Electrically connect the control circuit in the control cabin to the real-time display and control unit of the deck control console;

[0014] (2) The horizontal probe rod is retracted to a vertical state through the real-time display and control unit, and the vertical position limit plate is opened to ensure that the horizontal probe rod can be retracted and extended underwater.

[0015] (3) The in-situ measurement system is placed in the water by means of a lifting device until the supporting platform touches the bottom, that is, is located above the seabed sediment and cannot sink any further; during the placement process, the horizontal probe rod is kept in a vertical state;

[0016] (4) driving the vertical probe rod downward by means of a penetration cylinder until the receiving transducer at the bottom end of the vertical probe rod is located at a preset depth in the seabed sediment; and driving the horizontal probe rod to a horizontal state by means of a hydraulic motor;

[0017] (5) sending sound wave emission and acquisition parameters and instructions to the sound wave emission and acquisition system in the control circuit encapsulated in the control cabin through the real-time display and control system, the transmitting transducer transmits medium and low frequency sound wave signals, the receiving transducer receives the medium and low frequency sound wave signals, and the receiving transducer uploads the collected data to the real-time display and control system;

[0018] (6) The horizontal probe rod is restored to a vertical state by the hydraulic motor, and the vertical probe rod is driven to rise by the penetration cylinder until the vertical probe rod is restored to its original position;

[0019] (7) The in-situ measurement system is recovered to the mother ship through the lifting equipment.

[0020] Preferably, in step (4), when the penetration cylinder is unable to drive the vertical probe rod to the preset depth at one time, the penetration cylinder drives the vertical probe rod to perform several downward insertion actions until the receiving transducer at the bottom end of the vertical probe rod is located at the preset depth in the seabed sediment.

[0021] Compared with the prior art, the in-situ measurement system for low-frequency acoustic characteristics of seabed sediments of the present invention has achieved the following technical effects:

[0022] The in-situ measurement system for medium- and low-frequency acoustic characteristics of seabed sediments of the present invention realizes the in-situ measurement of the propagation characteristics of medium- and low-frequency sound waves in sediments. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 It is a structural schematic diagram of the working state of the in-situ measurement system of low-frequency acoustic characteristics of seabed sediments of the present invention;

[0025] Figure 2 It is a structural schematic diagram of the zero-position state of the in-situ measurement system of low-frequency acoustic characteristics of seabed sediments of the present invention;

[0026] Figure 3 It is a structural schematic diagram of a vertical probe rod penetration mechanism in the in-situ measurement system of low-frequency acoustic characteristics of seabed sediments of the present invention;

[0027] Figure 4 It is a schematic diagram of the transmission and reception of transducer signals in the in-situ measurement system of low-frequency acoustic characteristics of seabed sediments of the present invention;

[0028] Figure 5 The circuit schematic diagram of the control unit in the in-situ measurement system of low-frequency acoustic characteristics in seabed sediments of the present invention;

[0029] Among them: 1. Vertical probe rod; 2. Vertical probe rod penetration mechanism; 2-1. Penetration cylinder; 2-2. Movable clamping cylinder; 2-3. Slider; 2-4. Guide rail; 2-5. Fixed clamping cylinder; 3. Load-bearing platform; 3-1. Load-bearing frame; 3-2. Lifting ring; 3-3. Base; 4. Horizontal probe rod support mechanism; 4-1. Vertical position limit plate; 4-2. Horizontal position limit bracket; 4-3. Hydraulic motor; 5. Horizontal probe rod; 6. Control cabin; 7. Hydraulic cabin; 8. Transmitting transducer; 9. Receiving transducer; 10. Attitude sensor, 11. Penetration cylinder pressure sensor; 12. Hydraulic motor pressure sensor; 13. Lifting cylinder pressure sensor; 14. Angle sensor; 15. Displacement sensor; 16. Lifting cylinder. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] The purpose of the present invention is to provide an in-situ measurement system and method for low-frequency acoustic characteristics of seabed sediments, so as to solve the problems existing in the above-mentioned prior art and realize the measurement of the propagation characteristics of low-frequency sound waves in sediments.

[0032] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] like Figures 1 to 4 As shown: the in-situ measurement system of low-frequency acoustic characteristics of seabed sediments in this embodiment includes a bearing frame 3-1, in which a control cabin 6, a hydraulic cabin 7, a vertical probe rod penetration mechanism 2 and a horizontal probe rod support mechanism 4 are arranged, a lifting ring 3-2 is arranged at the top of the bearing frame 3-1, and the vertical probe rod 1 mechanism includes a vertical guide rail 2-4 fixedly arranged on the bearing frame 3-1, a penetration cylinder 2-1 is fixedly arranged at the top of the guide rail 2-4, the cylinder rod of the penetration cylinder 2-1 is fixedly connected to a slider 2-3, the slider 2-3 is slidably matched with the guide rail 2-4, a movable clamping cylinder 2-2 is fixedly arranged on the slider 2-3, and the guide rail 2-4 is provided with a movable clamping cylinder 2-2. A fixed clamping cylinder 2-5 is fixedly provided at the bottom end of the rail 2-4, and the movable clamping cylinder 2-2 and the fixed clamping cylinder 2-5 respectively clamp the same vertical probe rod 1, and two receiving transducers 9 arranged at intervals up and down are fixedly provided at the bottom end of the vertical probe rod 1; the horizontal probe rod supporting mechanism 4 includes a driving device fixedly provided on the supporting frame 3-1, and the output shaft of the driving device is perpendicular and fixedly connected to one end of the horizontal probe rod 5, and the driving device can drive the horizontal probe rod 5 to rotate with the output shaft as the center axis, and a transmitting transducer 8 is provided at the other end of the horizontal probe rod 5, and the receiving transducer 9 is a broadband transducer, and the receiving transducer 9 can receive medium and low frequency sound waves.

[0034] The vertical probe rod penetration mechanism can continuously insert the vertical probe rod 1 through the coordinated action of the movable clamping cylinder 2-2, the fixed clamping cylinder 2-5, and the penetration cylinder 2-1, so that the receiving transducer 9 can be inserted into the sediment to a sufficient depth; the horizontal probe rod support mechanism drives the horizontal probe rod 5 to a horizontal position, so that the transmitting transducer 8 and the receiving transducer 9 can reach a sufficiently long distance, and the lifting cylinder 16 can realize the lifting and lowering of the transmitting transducer 8 on the horizontal probe rod 5, ensuring that the transmitting transducer 8 can be close to the surface of the seabed sediment, so that it meets the measurement conditions of medium and low frequency acoustic characteristics.

[0035] A lifting cylinder 16 is also provided on the horizontal probe rod 5. The cylinder rod of the lifting cylinder 16 is perpendicular to the horizontal probe rod 5. The transmitting transducer 8 is fixedly connected to the cylinder rod of the lifting cylinder 16. The horizontal probe rod support mechanism 4 also includes a horizontal position limit bracket 4-2 and a vertical position limit plate 4-1. The driving device is a hydraulic motor 4-3. The horizontal position limit bracket 4-2 is fixedly mounted on the bearing frame 3-1. The hydraulic motor 4-3 is fixedly mounted on the horizontal position limit bracket 4-2. The top of the bearing bracket is provided with a receiving hole corresponding to the horizontal probe rod 5. The receiving hole is provided with a notch. The horizontal probe rod 5 passes through the receiving hole when it is in a vertical state. The vertical position limit plate 4-1 is detachably installed at the notch by bolts. When the measuring system is in a storage state, the vertical position limit plate 4-1 fixes the horizontal probe rod 5 in the receiving hole to prevent it from swinging outwards due to vibration or other reasons. A plurality of feet 3 - 3 are arranged at the bottom end of the load-bearing frame 3 - 1 , a lifting ring 3 - 2 is arranged at the top end of the load-bearing frame 3 - 1 , and the load-bearing frame 3 - 1 , the lifting ring 3 - 2 and the feet 3 - 3 constitute the load-bearing platform 3 .

[0036] The control cabin 6 is provided with a control circuit and a posture sensor 10 electrically connected to the control circuit. The hydraulic cabin 7 is sealed. The hydraulic cabin 7 is provided with a penetration cylinder pressure sensor 11, a hydraulic motor pressure sensor 12, and a lifting cylinder pressure sensor 13 electrically connected to the control circuit. The penetration cylinder pressure sensor 11, the hydraulic motor pressure sensor 12, and the lifting cylinder pressure sensor 13 are connected to corresponding oil pipes respectively. The oil pipes of the penetration cylinder 2-1, the hydraulic motor 4-3, and the lifting cylinder 16 all pass through the hydraulic cabin. The control circuit is electrically connected to the display and control system through a cable; a displacement sensor 15 electrically connected to the control circuit is provided on the slider 2-3, and an angle sensor 14 electrically connected to the control circuit is provided on the output shaft of the hydraulic motor 4-3.

[0037] The values ​​detected by the above-mentioned sensors can all be displayed in the display and control system, wherein the posture sensor 10 measures the real-time posture of the supporting frame 3-1, and determines whether the posture of the supporting frame 3-1 underwater meets the measurement requirements; the angle sensor 14 measures the real-time swing angle of the horizontal probe 5, and determines whether it swings to a horizontal or vertical position; the displacement sensor 15 measures the real-time insertion depth of the vertical probe; the hydraulic motor pressure sensor 12 measures the real-time pressure of the hydraulic motor, and assists in judging whether the horizontal probe has swung to the extreme position; the lifting cylinder pressure sensor 13 measures the real-time pressure of the lifting cylinder 16, and determines whether the lifting cylinder 16 has been lifted to the extreme position.

[0038] The transmitting transducer 8 is a mosaic cylindrical transducer, which is installed at the head of the horizontal probe 5 and can emit low- and medium-frequency sound waves with a frequency of 1-10kHz in the radial direction and is omnidirectional. In order to meet the needs of medium- and low-frequency sound wave emission, the transmitting transducer 8 adopts a circular mosaic structure. The transmitting transducer 8 is bonded into a circular ring by multiple piezoelectric ceramic strips and filling materials (metal splicing strips), and metal covers are installed at the top and bottom ends of the assembled piezoelectric ceramic ring. The transmitting transducer 8 is omnidirectional in the radial direction to ensure that the transmitting transducer 8 has a good sound source level in the plane composed of the receiving hydrophone, the vertical probe 1, the horizontal probe 5 and the transmitting transducer 8. The receiving transducer 9 is a broadband hydrophone embedded in the vertical probe 1. A sound-transmitting window is opened at the embedded part so that the sound waves can be transmitted to the hydrophone. During the insertion process of the vertical probe 1, the vertical probe 1 can well protect the receiving transducer 9 to prevent the receiving transducer 9 from being damaged by pressure. Two receiving transducers 9 are installed at the bottom of the vertical probe rod 1 at a certain distance; the receiving transducer 9 has a large beam opening angle in the vertical direction to ensure good receiving sensitivity in the oblique sound line direction. Both receiving transducers 9 receive the medium and low frequency sound wave signals from the transmitting transducer 8 for test data backup, so as to obtain the medium and low frequency acoustic characteristics of the measured seabed sediments.

[0039] The length of the vertical probe rod 1 and the length of the horizontal probe rod 5 are both greater than 3m. When the vertical probe rod 1 is inserted into the seabed sediment to the maximum depth and the horizontal probe rod 5 is fully extended to the horizontal position, the distance between the transmitting transducer 8 and the two receiving transducers 9 is greater than 3m, so that the transmission and reception interval is not less than the distance of two sound wave wavelengths (for the lowest frequency of 1kHz that can be measured by this system, the sound wave wavelength is about 1.5m), which meets the needs of measuring the acoustic characteristics of medium and low frequency sediments.

[0040] When the in-situ measurement system for low-frequency acoustic characteristics of seabed sediments of this embodiment is in working state, the receiving transducer 9 is inserted into the sediment at a depth of 3m, the transmitting transducer 8 is arranged on the surface of the sediment, and the connecting line between the transmitting transducer 8 and the receiving transducer 9 is an oblique line with a certain angle to the sediment surface. The whole system constitutes an oblique measurement method.

[0041] The real-time display and control system realizes the real-time operation and monitoring of the measurement system on the deck. The display and control system allows the surveyor to determine the actual insertion depth of the receiving transducer 9, the swing angle of the transmitting transducer 8 and other parameters according to the actual seabed topography and the actual posture of the bearing frame on the seabed, and can judge whether the receiving transducer 9 and the transmitting transducer 8 are in place according to the real-time measurement values ​​of each sensor; and can observe the sediment acoustic characteristic curve obtained by the measurement system in real time to judge the progress of the measurement operation.

[0042] This embodiment also provides an in-situ measurement method for low-frequency acoustic characteristics in seabed sediments, comprising the following steps:

[0043] (1) Connect the deck control console to the optical cable of the photoelectric winch, and connect the optical cable of the photoelectric winch to the control circuit in the control cabin 6 on the carrying platform 3, and perform transmission parameter preset and collection parameter preset in the real-time display and control system of the deck control console;

[0044] (2) Debug the transmitting transducer 8, the receiving transducer 9 and their signal processing modules through the real-time display and control unit of the deck console, debug the insertion and lifting actions of the vertical probe rod 1 and the displacement sensor 15; debug the retraction and extension actions of the horizontal probe rod 5, debug the penetration cylinder pressure sensor 11, the hydraulic motor pressure sensor 12, the lifting cylinder pressure sensor 13, the attitude sensor 10, and the angle sensor 14;

[0045] (3) Lift the vertical probe rod 1 to the highest position, and return the displacement sensor 15 to zero; retract the horizontal probe rod 5 to a vertical state, return the angle sensor 14 of the horizontal probe rod 5 to zero, and open the vertical position limit plate 4-1 of the horizontal probe rod 5 to ensure that the horizontal probe rod 5 can be retracted and extended underwater;

[0046] (4) Swing the mother ship to hoist the equipment and release the optical cable, and place the in-situ measurement system into the water. During this process, the equipment must be properly stopped. During the placement of the measurement system, the horizontal probe 5 is kept in the vertical storage position to prevent the impact force from causing damage to the transmitting transducer 8;

[0047] (5) When the bearing platform 3 touches the bottom, confirm whether the angle value transmitted by the posture sensor 10 to the real-time display and control system is within the allowable range of the in-situ measurement. If the angle value transmitted by the posture sensor 10 to the real-time display and control system is not within the allowable range of the in-situ measurement, lift the bearing platform 3 and repeat step (4) until the angle value transmitted by the posture sensor 10 to the real-time display and control system is within the allowable range of the in-situ measurement. After confirming that the angle value transmitted by the posture sensor 10 to the real-time display and control system is within the allowable range of the in-situ measurement, start the penetration cylinder 2-1 and slowly insert the vertical probe rod 1 into the sediment. During this process, it is necessary to observe the real-time value of the displacement sensor 15 in the real-time display and control unit to determine whether the vertical probe rod 1 is inserted into place, and observe the value of the penetration cylinder pressure sensor 11. When the pressure is too high, the vertical probe rod 1 can be repeatedly lifted up and inserted down to reduce the load of the hydraulic system. When the vertical probe rod 1 is inserted into place, shut down the penetration cylinder 2-1.

[0048] (6) Start the hydraulic motor 4-3 of the horizontal probe rod support mechanism 4. During this process, it is necessary to observe the real-time value of the angle sensor 14 of the horizontal probe rod 5 in the real-time display and control system, and observe the value of the pressure sensor to determine whether the transmitting transducer 8 contacts the seabed sediment. The horizontal limit bracket is installed at the bottom of the bearing platform 3. When the horizontal probe rod 5 is swung outward to a horizontal position underwater, the horizontal limit bracket provides a limit for the horizontal probe rod 5 so that it can no longer swing outward;

[0049] (7) The real-time display and control system sends the parameters and instructions of sound wave transmission and collection to the sound wave transmission and collection system in the control circuit encapsulated in the control cabin 6, wherein the transmission circuit generates a medium-low frequency waveform signal of a specified frequency, which is amplified and transmitted to the transmitting transducer 8, and the transmitting transducer 8 transmits a medium-low frequency sound wave signal, which is received by the receiving transducer 9 after propagation in the sediment, and then collected by the collection circuit, and the collected data is uploaded to the real-time display and control system on the ship through the optoelectronic composite cable, and the data is saved; the collected data is also saved in the storage unit of the collection circuit as a backup;

[0050] (8) After the horizontal probe support mechanism 4 is deployed, the following three states are used to comprehensively judge whether the transmitting transducer 8 has contacted the sediment:

[0051] a) Whether the value of the angle sensor 14 of the horizontal probe rod 5 is near 90 degrees, if so, it means that the horizontal probe rod 5 is basically in a horizontal position;

[0052] b) Whether the pressure sensor of the hydraulic motor 4-3 is too large. If it is too large, it means that the horizontal probe rod 5 or the transmitting transducer 8 has been placed in contact with the sediment;

[0053] c) Observe the received low- and medium-frequency sound wave waveform curve: when the transmitting transducer 8 has not reached the sediment surface, the sound wave propagation route is a distance in water plus a distance in sediment. When the horizontal probe rod 5 slowly rotates to a horizontal position, the distance in water gradually decreases, and the distance in sediment gradually increases. The phenomenon reflected in the sound wave waveform curve is that the propagation characteristics in water gradually decrease, and the propagation characteristics in sediment gradually increase. When the sound wave curve is close to stability, it means that the transmitting transducer 8 has contacted with the sediment;

[0054] When the a) and b) states appear but the c) state does not appear, it means that the horizontal probe rod 5 has reached the sediment surface, but the transmitting transducer 8 has not yet reached the sediment surface. At this time, the lifting cylinder 16 needs to be started to drive the transmitting transducer 8 to move vertically downward until it contacts the sediment. In this process, whether the transmitting transducer 8 has contacted the sediment is comprehensively judged by the following two states:

[0055] 1) Is the lifting cylinder pressure sensor 13 too large? If so, it means that the transmitting transducer 8 has come into contact with the sediment;

[0056] 2) Observe the received low- and medium-frequency sound wave waveform curve: When the transmitting transducer 8 has not reached the sediment surface, the sound wave propagation route is a distance in water plus a distance in sediment. When the horizontal probe rod 5 slowly rotates to a horizontal position, the distance in water gradually decreases, and the distance in sediment gradually increases. The phenomenon reflected in the sound wave waveform curve is that the propagation characteristics in water gradually decrease, and the propagation characteristics in sediment gradually increase. When the sound wave curve is close to stability, it means that the transmitting transducer 8 has contacted with the sediment;

[0057] (9) When the transmitting transducer 8 contacts the sediment, the hydraulic motor 4-3 of the horizontal probe support mechanism 4 and the lifting cylinder 16 are turned off, and the acoustic characteristic measurement is started and the received sound wave curve is observed to complete the acoustic measurement;

[0058] (10) After the acoustic measurement is completed, the acoustic wave transmitting module and the acoustic wave receiving module are turned off, and the transmitting transducer 8 lifting cylinder 16 is started. After the transmitting transducer 8 is lifted to the zero position, the transmitting transducer 8 lifting cylinder 16 is turned off; the hydraulic motor 4-3 of the horizontal probe rod supporting mechanism 4 is started, and the horizontal probe rod 5 is recovered to the vertical position and then the hydraulic motor 4-3 is turned off; when the horizontal probe rod 5 is in the vertical position, the vertical position limit plate 4-1 fixes the horizontal probe rod 5 in the receiving hole. At this time, when the hydraulic motor 4-3 does not provide driving force, the horizontal probe rod 5 will not tilt in the horizontal direction;

[0059] (11) Start the penetration cylinder 2-1 and slowly lift the vertical probe rod 1 from the sediment. During this process, it is necessary to observe the real-time value of the displacement sensor 15 in the real-time display and control system to determine whether the vertical probe rod 1 is lifted into place, and observe the value of the pressure sensor. When the pressure is too high, the vertical probe rod 1 is repeatedly lifted up and inserted down to reduce the load of the hydraulic system; when the vertical probe rod 1 is lifted into place, the penetration cylinder 2-1 is shut down;

[0060] (12) Recover the optical cable, recycle the carrying platform 3 to the mother ship, and install the vertical position limit plate 4-1.

[0061] The present specification uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. An in-situ measurement system for low-frequency acoustic characteristics of seafloor sediments, characterized by: The invention comprises a supporting frame, in which a control cabin, a hydraulic cabin, a vertical probe rod penetration mechanism and a horizontal probe rod support mechanism are arranged, the vertical probe rod penetration mechanism comprises a vertical guide rail fixedly arranged on the supporting frame, a penetration oil cylinder is fixedly arranged on the top of the guide rail, the cylinder rod of the penetration oil cylinder is fixedly connected to a slider, the slider is slidably matched with the guide rail, a movable clamping oil cylinder is fixedly arranged on the slider, a fixed clamping oil cylinder is fixedly arranged on the bottom end of the guide rail, the movable clamping oil cylinder and the fixed clamping oil cylinder respectively clamp the same vertical probe rod, two receiving transducers spaced apart up and down are fixedly arranged on the bottom end of the vertical probe rod, the penetration oil cylinder can drive the vertical probe rod to rise and fall; the horizontal probe rod support mechanism comprises a driving device fixedly arranged on the supporting frame, the output shaft of the driving device is perpendicular to and fixedly connected to one end of the horizontal probe rod, and the driving device can drive the horizontal probe rod to output the oil cylinder. The axis rotates around the central axis, and a transmitting transducer is arranged at the other end of the horizontal probe rod, and the transmitting transducer is a medium and low frequency sound wave transmitting transducer, and the receiving transducer can receive medium and low frequency sound waves; a control circuit is arranged in the control cabin, and a penetration cylinder pressure sensor electrically connected to the control circuit is arranged in the hydraulic cabin, and the control circuit is electrically connected to the display and control system through a cable; a lifting cylinder is also arranged on the horizontal probe rod, and the cylinder rod of the lifting cylinder is perpendicular to the horizontal probe rod, and the transmitting transducer is fixedly connected to the cylinder rod of the lifting cylinder, and the lifting cylinder can drive the transmitting transducer to be lifted and lowered; the length of the vertical probe rod and the length of the horizontal probe rod are both greater than 3m, and when the vertical probe rod is inserted into the seabed sediment to the maximum depth and the horizontal probe rod is fully unfolded to the horizontal position, the distance between the transmitting transducer and the two receiving transducers is greater than 3m.

2. The in-situ measurement system for low-frequency acoustic characteristics of seabed sediments according to claim 1, characterized in that: The horizontal probe rod supporting mechanism also includes a horizontal position limiting bracket and a vertical position limiting plate. The driving device is a hydraulic motor. The horizontal position limiting bracket is fixed on the supporting frame, and the hydraulic motor is fixed on the horizontal position limiting bracket. The top of the supporting frame is provided with a receiving hole corresponding to the horizontal probe rod, and the receiving hole is provided with a notch. The horizontal probe rod passes through the receiving hole when in a vertical state, and the vertical position limiting plate is detachably installed at the notch by bolts.

3. The in-situ measurement system for low-frequency acoustic characteristics of seabed sediments according to claim 2, characterized in that: The hydraulic cabin is sealed, and is further provided with a penetration cylinder pressure sensor, a hydraulic motor pressure sensor and a lifting cylinder pressure sensor which are respectively electrically connected to the control circuit; the control cabin is sealed, and is further provided with a posture sensor which is electrically connected to the control circuit; the slider is provided with a displacement sensor which is electrically connected to the control circuit, and the output shaft of the hydraulic motor is provided with an angle sensor which is electrically connected to the control circuit.

4. The in-situ measurement system for low-frequency acoustic characteristics of seabed sediments according to claim 1, characterized in that: The bottom end of the bearing frame is provided with a plurality of feet, the top end of the bearing frame is provided with a lifting ring, and the bearing frame, the lifting ring and the feet constitute a bearing platform.

5. The in-situ measurement system for low-frequency acoustic characteristics of seabed sediments according to claim 1, characterized in that: The transmitting transducer is electrically connected to the sound wave transmitting circuit in the control circuit, and the receiving transducer is electrically connected to the sound wave receiving circuit in the control circuit.

6. An in-situ measurement method for low-frequency acoustic characteristics in seabed sediments, characterized in that: An in-situ measurement system for low-frequency acoustic characteristics in seabed sediments based on any one of claims 1 to 5, and comprising the following steps: (1) Electrically connect the control circuit in the control cabin to the real-time display and control unit on the deck control console; (2) Retract the horizontal probe rod to a vertical state through the real-time display and control unit, and open the vertical position limit plate to ensure that the horizontal probe rod can be retracted and extended underwater; (3) The in-situ measurement system is placed in the water by means of a lifting device until the supporting platform touches the bottom, that is, is located above the seabed sediment and cannot sink any further; during the placement process, the horizontal probe rod is kept in a vertical state; (4) driving the vertical probe rod downward by means of a penetration cylinder until the receiving transducer at the bottom end of the vertical probe rod is located at a preset depth in the seabed sediment; and driving the horizontal probe rod to a horizontal state by means of a hydraulic motor; (5) The parameters and instructions of sound wave transmission and collection are sent to the sound wave transmission and collection system in the control circuit encapsulated in the control cabin through the real-time display and control unit, the transmitting transducer transmits medium and low frequency sound wave signals, the receiving transducer receives the medium and low frequency sound wave signals, and the receiving transducer uploads the collected data to the real-time display and control unit; (6) The horizontal probe rod is restored to a vertical state by the hydraulic motor, and the vertical probe rod is driven to rise by the penetration cylinder until the vertical probe rod returns to its original position; (7) Recover the in-situ measurement system to the mother ship through the lifting equipment.

7. The in-situ measurement method of low-frequency acoustic characteristics in seabed sediments according to claim 6, characterized in that: In step (4), when the penetration cylinder is unable to drive the vertical probe rod to the preset depth at one time, the penetration cylinder drives the vertical probe rod to perform several downward insertion actions until the receiving transducer at the bottom end of the vertical probe rod is located at the preset depth in the seabed sediment.

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