Spherical complex resonance type vector hydrophone based on MEMS (Micro Electro Mechanical System) accelerometer

Abstract

The invention provides a spherical complex vibration type vector hydrophone based on an MEMS accelerometer, and relates to the technical field of underwater acoustic signal detection, and the spherical complex vibration type vector hydrophone comprises an MEMS accelerometer, a built-in core, a piezoelectric ceramic spherical shell, a sound transmission sealing shell, and a suspension ring. The MEMS accelerometer is orthogonally arranged in the built-in core; the built-in core is nested in the lower half ball of the piezoelectric ceramic spherical shell; the upper hemisphere of the perforated piezoelectric ceramic spherical shell is adhered to the upper edge of the built-in core; the sound transmission sealing shell coats the piezoelectric ceramic spherical shell through an encapsulation process; the suspension ring is bonded with the sound transmission sealing shell, and the hydrophone is suspended on the fixing support for use. The composite hydrophone can detect sound pressure signals and vibration velocity signals at the same position underwater, solves the problem of omnidirectional detection of the composite hydrophone on the sound pressure signals, and has the advantages of small size, simple structure, high reliability, wide application range and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of underwater acoustic signal detection, and in particular to a spherical composite isotropic vector hydrophone based on a MEMS accelerometer. Background Art

[0002] Water is an elastic medium, and any disturbance in it propagates as waves from its source. The fundamental parameters of these acoustic waves are amplitude and frequency. Functionally, the pressure changes of acoustic waves generated in water, or changes in acoustic velocity that are strictly related to pressure, along with other noise within the detectable frequency bandwidth, reach a vector hydrophone or hydrophone array. These signals are then converted into electrical or optical signals by the hydrophone. By processing the acoustic field information received by the hydrophone, the presence of underwater targets can be determined and even their status characteristics can be determined.

[0003] Based on two easily detectable characteristics of sound waves, hydrophones are divided into scalar hydrophones and vector hydrophones. Scalar hydrophones are mainly based on various piezoelectric sensors, which mainly detect the pressure changes of sound waves and determine the target state in the form of an array; while vector hydrophones include different structural types, such as optical fiber type, ciliary type, and synchronous type based on acceleration sensors. They determine the target state by detecting the vibration velocity or vibration acceleration of sound waves.

[0004] The typical structure of a scalar hydrophone array is a towed array, which has problems such as excessive size and blurred port and starboard images. Vector hydrophones can solve the problems faced by scalar detection because the detected vector signals are directional. However, due to the presence of noise in actual waters, it is not feasible to detect the target state with a single vector hydrophone. To solve this problem, some scholars have proposed combining piezoelectric ceramics with accelerometers to form a composite hydrophone. Due to the incoherence of noise in sound pressure and vibration velocity, simultaneous detection of scalar and vector signals and signal processing through methods such as average sound intensity detection can effectively eliminate weaker noise.

[0005] Existing research on composite hydrophones has mostly focused on two-dimensional hydrophones, primarily detecting horizontal signals and not considering vertical signal detection. Research on composite isotropic three-dimensional vector hydrophones, while capable of detecting vertical signals in the vector portion, still utilizes discrete pressure channel sensors for sound pressure detection, lacking vertical omnidirectionality and preventing accurate acquisition of sound field information. To address these issues, the following proposes a solution. Summary of the Invention

[0006] The present invention provides a spherical composite isotropic vector hydrophone based on a MEMS accelerometer. This hydrophone can detect sound pressure and velocity signals at the same underwater location in all directions. It not only has the advantages of small size, simple structure, and good reliability, but also has wide applicability, meeting various underwater acoustic signal detection requirements.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows: A spherical composite isostatic vector hydrophone based on a MEMS accelerometer comprises a hydrophone body and a suspension ring. The hydrophone body comprises an upper hemisphere of a piezoelectric ceramic shell, a lower hemisphere of a piezoelectric ceramic shell, and an acoustically sealed shell embedded in the outer surface of the piezoelectric ceramic shell. The upper hemisphere of the piezoelectric ceramic shell is provided with a cable lead-out hole. The piezoelectric ceramic hemispheres and shells are connected in parallel to each other and are connected to the outside via cables. The hydrophone body also comprises an internal core and at least three MEMS accelerometers, namely an X-axis accelerometer, a Y-axis accelerometer, and a Z-axis accelerometer. The internal core is located within the piezoelectric ceramic shell, the X-axis accelerometer and the Y-axis accelerometer are vertically mounted within the internal core, and the Z-axis accelerometer is horizontally mounted within the internal core. All MEMS capacitive accelerometers are orthogonal to each other, and the sensitive units of each MEMS accelerometer are at the same geometric center distance from the hydrophone body. The MEMS accelerometers are connected to the outside via cables that penetrate the cable lead-out hole and the acoustically sealed shell.

[0008] Furthermore, the suspension ring has four through holes and is connected to the external suspension frame through rubber ropes or springs.

[0009] Furthermore, the diameter of the central circular hole of the suspension ring is the same as the outer diameter of the sound-transmitting sealed shell. The suspension ring is bonded to the outer side of the sound-transmitting sealed shell. The suspension ring is horizontal to the hydrophone body and the geometric centers of the two coincide.

[0010] Furthermore, the built-in core body is a hemispherical shell, embedded in the lower hemisphere of the piezoelectric ceramic shell, the outer diameter of the built-in core hemisphere is equal to the inner diameter of the piezoelectric ceramic shell, and the center of the built-in core hemisphere coincides with the center of the piezoelectric ceramic shell.

[0011] Furthermore, the interior of the built-in core spherical shell has four centrally symmetrical quadrangular prisms, the top of the quadrangular prisms and one side of the rectangular parallelepiped are embedded with nuts, the side of the hemispherical shell where the nuts are embedded has an opening, and the MEMS accelerometer has through holes at the four corners and is mounted on the built-in core by screws.

[0012] Furthermore, the center of gravity of the hydrophone including the suspension ring coincides with its geometric center.

[0013] Furthermore, the material of the sound-transmitting sealing shell is polyurethane.

[0014] Furthermore, the material of the suspension ring is photosensitive resin.

[0015] Furthermore, the built-in core material is aluminum alloy or nylon material.

[0016] The beneficial effects of the present invention are: 1. The present invention uses a piezoelectric ceramic spherical shell as the sound pressure sensitive unit and the outer shell, which can not only detect underwater sound pressure signals in all directions, but also simplifies the hydrophone structure and makes it have good consistency.

[0017] 2. The present invention uses a MEMS accelerometer as a vibration velocity sensitive unit and integrates relevant ASIC circuits on the accelerometer, thereby avoiding problems such as signal interference and attenuation caused by an external signal processing circuit.

[0018] 3. The present invention improves the accuracy of underwater acoustic signal detection by simultaneously measuring the scalar signal and vector signal at the same underwater position by merging the center of gravity of the hydrophone, the geometric center of the piezoelectric ceramic shell, and the detection center of the orthogonal accelerometer. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0020] Figure 1 It is an exploded view of the structure of the present invention; Figure 2 It is a cross-sectional view of the main body of the present invention; Figure 3 This is a schematic diagram of the hydrophone-suspension ring assembly of the present invention; In the figure: 1. Hydrophone body; 2. Suspension ring; 11. Upper hemisphere of the piezoelectric ceramic shell; 12. Lower hemisphere of the piezoelectric ceramic shell; 13. Internal core; 14. X-axis accelerometer; 15. Y-axis accelerometer; 16. Z-axis accelerometer; 17. Screws; 111. Cable lead-out hole; 131. Square prism; 132. Nut. DETAILED DESCRIPTION

[0021] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0022] The theoretical basis of the present invention's design is: For the sound pressure signal, when the radially polarized piezoelectric ceramic shell is in the underwater sound field, it will be deformed by the excitation of the underwater acoustic signal and generate electric charge based on the piezoelectric effect, thereby converting the detected underwater acoustic pressure signal into an electrical signal output.

[0023] For vector signals, if the geometric size of a rigid sphere is much smaller than the wavelength, then when it vibrates freely under the action of sound waves in water, the vibration velocity amplitude of the rigid sphere and the vibration velocity amplitude of the water particle at the center of gravity of the sphere in the sound field have the following relationship: in, is the vibration velocity amplitude of the rigid sphere, is the vibration velocity amplitude of the water particle at the geometric center of the sphere in the sound field, is the density of the aqueous medium, is the average density of the rigid cylinder.

[0024] According to the above principle, for a spherical isotropic vector hydrophone, if the hydrophone as a whole meets the isotropic condition, that is, the average density is equal to the density of water, the internal MEMS accelerometer can detect the vibration acceleration of the hydrophone and output an electrical signal to detect the vibration acceleration of the water particle corresponding to the center of gravity of the hydrophone.

[0025] In summary, if the center of gravity of the hydrophone, the geometric center of the piezoelectric ceramic shell, and the detection center of the orthogonal accelerometer are unified, the complete signal including sound pressure and vibration velocity in the same water particle can be detected.

[0026] The following is a specific embodiment: like Figure 1-Figure 3 As shown, the spherical composite isostatic vector hydrophone based on a MEMS accelerometer provided in an embodiment of the present invention uses a MEMS capacitive accelerometer and a piezoelectric ceramic shell as its primary sensing components. The hydrophone includes a hydrophone body 1 and a suspension ring 2. The hydrophone body 1 includes an upper piezoelectric ceramic shell hemisphere 11, a lower piezoelectric ceramic shell hemisphere 12, an internal core 13, an X-axis accelerometer 14, a Y-axis accelerometer 15, and a Z-axis accelerometer 16.

[0027] The X-axis accelerometer 14 and the Y-axis accelerometer 15 are orthogonally fixed to the built-in core 13 by screws 17 and kept perpendicular to the horizontal plane. The Z-axis accelerometer 16 is fixed to the built-in core 13 by screws 17 and kept parallel to the horizontal plane. The three MEMS capacitive accelerometers are orthogonal to each other, and the sensitive units of each accelerometer are at the same distance from the geometric center of the hydrophone.

[0028] The material of the built-in core is very low-density nylon PA12, and the main body is a hemispherical shell. The core hemispherical shell has openings in the installation direction of the X-axis accelerometer and the Y-axis accelerometer, which is used to balance the center of gravity of the hydrophone and facilitate the installation of the accelerometer; the outer diameter of the core hemisphere is equal to the inner diameter of the piezoelectric ceramic shell, and a ring extends outward from the upper edge of the core hemisphere, and the outer diameter of the ring is equal to the outer diameter of the piezoelectric ceramic shell; the built-in core is embedded in the lower hemisphere of the piezoelectric ceramic shell, and the center of gravity of the core and accelerometer assembly coincides with the geometric center of the hydrophone.

[0029] The upper hemisphere of the piezoelectric ceramic shell, the built-in core, and the lower hemisphere of the piezoelectric ceramic are bonded together with glue. The wires connected to the MEMS capacitive accelerometer and the piezoelectric ceramic shell are led out through the cable lead-out hole of the upper hemisphere of the piezoelectric ceramic shell. The cross-sectional view of the hydrophone body after assembly and bonding is shown in the figure. Figure 2 shown.

[0030] After assembly and bonding, the hydrophone body needs to be enclosed in an acoustically transparent, sealed housing. This seal isolates the hydrophone's primary sensing elements from water, ensuring adequate watertightness and insulation. Furthermore, the housing is acoustically transparent, transmitting the sound pressure signal in the water to the piezoelectric ceramic sphere without attenuation. The acoustically transparent, sealed housing is made of polyurethane, which is cured in a custom mold through a potting process.

[0031] After potting, the overall density of the hydrophone is close to 1g / cm³, which meets the co-oscillation condition. The hydrophone can accurately reflect the vibration of the water particle corresponding to the center of gravity.

[0032] After potting is completed, the center of gravity of the hydrophone coincides with the geometric center, and the scalar and vector parts of the underwater acoustic signal can be measured simultaneously and concurrently.

[0033] After potting is completed, a suspension ring is bonded to the outside of the sound-transmitting sealed shell, and 8 rubber ropes are used to fix the hydrophone to the bracket through the through holes of the suspension ring, so that the hydrophone can maintain a stable posture while being able to vibrate freely.

[0034] The performance of the hydrophone of the present invention is mainly characterized by scalar channel sensitivity and vector channel sensitivity.

[0035] The sensitivity of the vector channel is determined by the sensitivity of the accelerometer and is calculated as follows: in, is the vector channel sensitivity of the hydrophone, is the accelerometer sensitivity, is the angular frequency of the sound wave, is the average density of the hydrophone, and c is the speed of sound waves.

[0036] Typically, the sensitivity performance of a hydrophone is determined by the sound pressure sensitivity level. Characterization, the relationship between the sound pressure sensitivity level and the vector channel sensitivity is as follows: In this embodiment, the sensitivity of the selected MEMS capacitive accelerometer is 1200 mV / g. According to the formula, the sound pressure sensitivity level of the vector channel at 1 kHz is -185.5 dB.

[0037] For a radially polarized piezoelectric ceramic shell, the scalar channel sensitivity is calculated as follows: in, is the scalar channel sensitivity of the hydrophone, is the radial piezoelectric coefficient of the piezoelectric ceramic shell, is the tangential piezoelectric coefficient of the piezoelectric ceramic shell, a is the inner radius of the piezoelectric ceramic shell, and b is the outer radius of the piezoelectric ceramic shell.

[0038] The outer radius of the piezoelectric ceramic shell used in this embodiment is 31.5 mm, and the inner radius is 29.5 mm. for , for , the calculated scalar channel sensitivity level is -188dB.

[0039] In summary, the scalar channel sensitivity and vector channel sensitivity of the hydrophone described in this embodiment are far higher than the minimum standards specified by the national metrology and calibration regulations, and have good performance.

[0040] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiment. All technical solutions based on the concept of the present invention are within the scope of protection of the present invention. It should be noted that for those skilled in the art, various improvements and modifications that do not depart from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A spherical composite isotropic vector hydrophone based on a MEMS accelerometer, comprising a hydrophone body (1) and a suspension ring (2), wherein the hydrophone body comprises an upper hemisphere (11) of a piezoelectric ceramic shell, a lower hemisphere (12) of a piezoelectric ceramic shell, and a sound-transmitting sealed shell embedded in the outer surface of the piezoelectric ceramic shell; the upper hemisphere of the piezoelectric ceramic shell is provided with a cable lead-out hole (111); the piezoelectric ceramic hemispheres and shells are connected in parallel and connected to the outside via cables; and characterized in that: The hydrophone body also includes a built-in core (13) and at least three MEMS accelerometers, wherein the MEMS accelerometers are an X-axis accelerometer (14), a Y-axis accelerometer (15), and a Z-axis accelerometer (16); the built-in core (13) is located inside the piezoelectric ceramic spherical shell, the X-axis accelerometer and the Y-axis accelerometer are vertically installed inside the built-in core (13), and the Z-axis accelerometer is horizontally installed inside the built-in core (13); all MEMS accelerometers are orthogonal to each other, and the sensitive units of each MEMS accelerometer are at the same distance from the geometric center of the hydrophone body (1); the MEMS accelerometer is connected to the outside through a cable penetrating the cable lead-out hole and the sound-transmitting sealed shell.

2. The spherical composite isotropic vector hydrophone based on a MEMS accelerometer according to claim 1, characterized in that: The suspension ring (2) has four through holes and is connected to an external suspension frame via a rubber rope or a spring.

3. The spherical composite isotropic vector hydrophone based on a MEMS accelerometer according to claim 2, characterized in that: The diameter of the central circular hole of the suspension ring (2) is the same as the outer diameter of the sound-transmitting sealed shell. The suspension ring (2) is bonded to the outer side of the sound-transmitting sealed shell. The suspension ring (2) is horizontal to the hydrophone body and the geometric centers of the two coincide.

4. The spherical composite isotropic vector hydrophone based on a MEMS accelerometer according to claim 1, characterized in that: The main body of the built-in core (13) is a hemispherical shell, which is embedded in the lower hemisphere of the piezoelectric ceramic shell. The outer diameter of the hemisphere of the built-in core (13) is equal to the inner diameter of the piezoelectric ceramic shell, and the center of the hemisphere of the built-in core (13) coincides with the center of the piezoelectric ceramic shell.

5. The spherical composite isotropic vector hydrophone based on a MEMS accelerometer according to claim 4, characterized in that: The spherical shell of the built-in core (13) has four centrally symmetrical quadrangular prisms (131), the top of the quadrangular prisms (131) and one side of the rectangular parallelepiped are embedded with nuts (132), and the side of the hemispherical shell where the nuts (132) are embedded has an opening. The MEMS accelerometer has through holes at the four corners and is mounted on the built-in core (13) by screws (17).

6. The spherical composite isotropic vector hydrophone based on a MEMS accelerometer according to claim 1, characterized in that: The center of gravity of the suspension ring (2) and the hydrophone body (1) as a whole coincides with their geometric center.

7. The spherical composite isotropic vector hydrophone based on a MEMS accelerometer according to claim 1, characterized in that: The material of the sound-transmitting sealing shell is polyurethane.

8. The spherical composite isotropic vector hydrophone based on a MEMS accelerometer according to claim 1, characterized in that: The material of the suspension ring (2) is photosensitive resin.

9. The spherical composite isotropic vector hydrophone based on a MEMS accelerometer according to claim 1, characterized in that: The built-in core (13) is made of aluminum alloy or nylon.

Images