Neutral buoyancy dynamic electrode differential capacitance vector hydrophone and its frequency band extension method

Abstract

The present invention relates to a neutrally buoyant moving electrode differential capacitance vector hydrophone and its frequency band expansion method, belonging to the field of low-frequency vector hydrophone devices and their frequency band expansion methods. An underwater acoustic acquisition mechanism with a differential capacitance function is approximately suspended within a pressure-resistant insulating liquid in an underwater acoustic channel. A floater, which functions as a moving electrode, brings the density of the neutrally buoyant moving electrode mechanism close to that of the pressure-resistant insulating liquid, forming a nearly suspended "neutral buoyancy" unit. The underwater acoustic vibration signal is transmitted through the pressure-resistant insulating liquid and directly acts on the surface of the nearly suspended moving electrode. Low-frequency underwater acoustic velocity information is obtained by detecting the displacement change of the neutrally buoyant moving electrode relative to the fixed electrode. Low-frequency displacement detection replaces inertial acceleration detection, significantly improving the sensitivity of low-frequency underwater acoustic signal detection. A linear motor composed of a magnet within the moving electrode plate and a coil within the fixed electrode plate serves as a feedback force output unit, employing force balance negative feedback technology to further expand the frequency band of the hydrophone.

Description

Technical Field

[0001] The present invention belongs to the field of low-frequency vector hydrophone devices and frequency band extension methods thereof, and particularly relates to a neutral buoyancy dynamic electrode differential capacitance vector hydrophone and a frequency band extension method thereof. Background Art

[0002] Vector hydrophones are sensors used to measure the velocity vector of particles in the underwater acoustic field. Compared to scalar hydrophones, they offer superior immunity to coherent interference and isotropic noise, making them widely used in sonar systems, underwater target identification, and ocean noise measurement. Low-frequency underwater acoustic signals exhibit minimal attenuation over long distances. Monitoring low-frequency radiated noise is a primary method for long-range passive positioning of underwater targets, and low- and ultra-low-frequency vector hydrophones are key sensors.

[0003] There are many types of vector hydrophones, each employing vastly different transduction principles, resulting in significantly different structures and characteristics, as well as varying advantages and disadvantages. Structurally, vector hydrophones can be categorized as inertial, differential pressure, and ciliary. Transduction methods include piezoelectric, capacitive, fiber optic, hot wire, and electrochemical. Currently, the most frequently used vector hydrophone is the inertial type, which uses an inertial accelerometer or velocimeter as its core unit. This type of inertial vector hydrophone is also known as the co-oscillation type.

[0004] In 2016, researchers Sun Qindong and others published a coherent vector hydrophone in their paper "Design and Implementation of a Coherent Triaxial Vector Hydrophone." This device consists of a triaxial inertial accelerometer packaged in a small rigid housing, with its overall density adjusted to approximate that of seawater. The inertial vector hydrophone is suspended from a rigid bracket using elastic rubber cord, maintaining its free position within the measured liquid environment. Based on the well-known principle that the motion response of a freely moving rigid sphere in an ideal fluid medium in a low-frequency plane wave field is equal to the measured seawater's vibration velocity, the device records the change in the inertial sensor's output voltage caused by the rigid object's motion, enabling particle velocity measurements in the underwater sound field. This type of co-oscillating vector hydrophone, suspended from a fixed frame by rubber ropes, has a force model that can be approximated as a typical second-order mass / spring / damper system. Essentially, this vector hydrophone uses its accelerometer to measure the acceleration of a moving object. However, the signal representing the acceleration of the acoustic particle vibration, corresponding to the low-frequency velocity of the acoustic particle, is extremely weak. This causes the sensitivity of this acceleration-based inertial vector hydrophone to decrease in the ocean's background noise environment as the target detection frequency decreases, or the proportion of background noise in its sensitivity index increases as the measured frequency decreases, hindering low-frequency measurement of underwater acoustic signals. Furthermore, the multiple elastic rubber ropes used to suspend the accelerometers in this co-oscillating triaxial vector hydrophone are crucial components of the inertial vector hydrophone unit. The radial stiffness of these elastic components, along with their specific suspension angle and position, significantly impact the overall performance of the vector hydrophone, leading to poor consistency and long-term stability in inertial vector hydrophone applications.

[0005] In 2013, researchers such as Gong Zhanjiang published a capacitive vector hydrophone in the paper "Development of a Novel Three-Dimensional MEMS Capacitive Vector Hydrophone." This device essentially employed an inertial accelerometer for a differential capacitive vector hydrophone. This differential capacitive inertial accelerometer was encapsulated within a cylindrical rigid object to form the capacitive vector hydrophone. A more accurate description of this device would be "an inertial vector hydrophone with a differential capacitive inertial accelerometer as its core unit." The accelerometer used in this capacitive hydrophone is based on the piezoelectric transduction principle, resulting in better low-frequency characteristics than piezoelectric accelerometers. This helped further reduce the low-frequency sensitivity of the inertial vector hydrophone, but the improvement was still unsatisfactory and fell short of meeting application requirements. Furthermore, this approach did not address the poor performance consistency and long-term stability of accelerometer-based inertial vector hydrophones during application.

[0006] Patent application publication number CN 116878645 A, "An Electrochemical Vector Hydrophone with a Bionic Jellyfish Ear Structure," discloses an electrochemical vector hydrophone. Its core principle is to develop a vector hydrophone based on the principle of electrochemical transduction. This device utilizes the vibration of an underwater acoustic particle to stimulate the vibration of the electrolyte within the hydrophone, thereby inducing an electrochemical current response at the sensitive electrode, enabling the measurement of the vibration velocity of the underwater acoustic particle. This device features high low-frequency sensitivity and is easier to install than an inertial hydrophone. However, this electrochemical vector hydrophone requires an electrolyte as the electrochemical reaction medium. This electrolyte is highly corrosive, oxidizing, and volatile, requiring the cavity containing the electrolyte to be stable and well-sealed. Otherwise, the concentration of the active substance in the electrolyte will readily decay over time, resulting in reduced sensitivity and a shortened service life. Furthermore, this type of electrochemical vector hydrophone is an open-loop measurement system and does not involve frequency band expansion control technology based on force balance negative feedback. Force balance negative feedback control for liquids is more difficult than for solids. Summary of the Invention

[0007] In order to solve the problem that the vibration acceleration signal of the underwater acoustic particle corresponding to the physical quantity of the low-frequency underwater acoustic particle vibration velocity is extremely weak, the sensitivity of the existing three-axis co-vibration inertial vector hydrophone based on acceleration detection quantity decreases as its target detection frequency decreases in the ocean background noise environment, causing its sensitivity to decrease with frequency or the background noise ratio to increase as the measured frequency decreases, which is not conducive to the low-frequency measurement of underwater acoustic signals; moreover, the three-axis co-vibration inertial vector hydrophone also has the inherent problem that its overall performance is significantly affected by the radial stiffness of its elastic components and the specific suspension method, resulting in poor consistency of measurement indicators and poor long-term stability.

[0008] Although existing capacitive vector hydrophones have replaced the old piezoelectric accelerometers by adopting accelerometers based on the piezoelectric transducer principle with better low-frequency characteristics, and have helped to further reduce the low-frequency sensitivity of inertial vector hydrophones, the improvement in the low-frequency signal measurement sensitivity of the hydrophones is still unsatisfactory and difficult to meet the needs. Moreover, it does not help to solve the inherent problem of poor consistency of indicators of inertial vector hydrophones based on accelerometers.

[0009] In order to solve the problem that the existing electrochemical vector hydrophone needs to use an electrolyte with extremely strong corrosiveness, strong oxidizing and volatility as the electrochemical reaction medium, which requires the cavity material containing the electrolyte to be stable and well-sealed, otherwise the concentration of the effective substance in the electrolyte will easily decay over time, causing the sensitivity of the hydrophone to decrease and the service life to be shortened; at the same time, since the force balance negative feedback control of liquids is more difficult than that of solids, most of the existing electrochemical vector hydrophones are open-loop measurement systems, and do not involve frequency band expansion control technology based on force balance negative feedback, which is not conducive to the calibration and adjustment of measurement results, the present invention provides a neutral buoyancy dynamic electrode differential capacitive vector hydrophone and a frequency band expansion method thereof.

[0010] The technical solutions adopted by the present invention to solve the technical problems are as follows:

[0011] A neutral buoyancy dynamic electrode differential capacitive vector hydrophone comprises an underwater acoustic collection mechanism, an underwater acoustic channel cylinder, a pressure-resistant insulating liquid, a circuit board compartment and a circuit board; a horizontally penetrating underwater acoustic channel is provided in the middle of the underwater acoustic channel cylinder, both ends of the underwater acoustic channel are sealed by two underwater acoustic windows in the underwater acoustic channel cylinder, the underwater acoustic channel is filled with pressure-resistant insulating liquid and the underwater acoustic collection mechanism is completely immersed in the pressure-resistant insulating liquid; the underwater acoustic collection mechanism is coaxially fixed to the center of the underwater acoustic channel and is used to collect underwater acoustic signals transmitted into the underwater acoustic channel through the pressure-resistant insulating liquid; the circuit board compartment is located outside the underwater acoustic channel cylinder and is waterproofly isolated from it, the circuit board is sealed in the circuit board compartment and is connected to the underwater acoustic collection mechanism signal; the circuit board is used to process and output the underwater acoustic signals transmitted by the underwater acoustic collection mechanism.

[0012] The beneficial effects of the present invention are:

[0013] The neutral buoyancy moving electrode differential capacitance vector hydrophone of the present invention has an underwater acoustic channel sealed with a pressure-resistant insulating liquid, and the underwater acoustic vibration signal enters the underwater acoustic channel through the underwater acoustic window with high transmittance. The underwater acoustic collection mechanism is coaxially fixed to the center of the underwater acoustic channel and completely immersed in the pressure-resistant insulating liquid. The neutral buoyancy moving electrode mechanism with the function of a differential capacitance sensor moving electrode plate has a density close to that of the pressure-resistant insulating liquid, so that the buoyancy force on the neutral buoyancy moving electrode mechanism of the present invention is approximately equal to the gravity, thereby obtaining the "neutral buoyancy" property.

[0014] 1. The neutral buoyancy moving electrode mechanism vibrates synchronously with the underwater acoustic particle. By utilizing the characteristic that the vibration displacement of the underwater acoustic particle increases with decreasing frequency, the displacement response of the neutral buoyancy moving electrode mechanism relative to the fixed electrode plate is detected to measure the vibration velocity information of the low-frequency underwater acoustic particle, thereby achieving a significant improvement in the low-frequency underwater acoustic signal detection capability.

[0015] 2. The neutrally buoyant moving electrode mechanism with "neutral buoyancy" properties is suspended in the pressure-resistant insulating liquid of the underwater acoustic channel by two three-arm planar springs whose radial stiffness is much greater than the axial stiffness. This avoids the inherent problems of inconsistent indicators and poor long-term stability caused by the suspension of multiple sets of rubber ropes in the old inertial vector hydrophone, thereby significantly improving the compactness and ease of use of the neutrally buoyant moving electrode differential capacitive vector hydrophone of the present invention.

[0016] 3. The pressure-resistant insulating liquid sealed and filled in the underwater acoustic channel does not directly participate in the detection of the underwater acoustic vibration signal. The pressure-resistant insulating liquid has loose requirements on the filling material, completely eliminating the high standards for sealing and storing highly corrosive and highly oxidizing electrolytes during the use of electrochemical vector hydrophones. As a result, the neutral buoyancy dynamic electrode differential capacitive vector hydrophone of the present invention does not suffer from the problems of reduced sensitivity or unstable indicators after long-term use.

[0017] 4. The float body of the neutral buoyancy moving electrode mechanism, the annular magnet fixed at the center and the two electromagnetic coils embedded in the fixed pole plate constitute the feedback motor of the neutral buoyancy moving electrode differential capacitive vector hydrophone, thereby making the neutral buoyancy moving electrode differential capacitive vector hydrophone using force balance feedback control of the present invention have more flexible and adjustable low-frequency detection capabilities. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the three-dimensional structure of the neutral buoyancy dynamic electrode differential capacitance vector hydrophone of the present invention;

[0019] Figure 2 This is a schematic diagram of the preliminary exploded assembly of the neutral buoyancy dynamic electrode differential capacitance vector hydrophone of the present invention;

[0020] Figure 3 This is a schematic diagram of the explosion assembly of the underwater acoustic channel cylinder of the present invention;

[0021] Figure 4 Schematic diagram of the three-dimensional structure of the hydroacoustic window of the present invention;

[0022] Figure 5 1 is a schematic diagram of an axial cross-section of the cylinder of the water acoustic channel of the present invention;

[0023] Figure 6 yes Figure 5 AA section view in;

[0024] Figure 7 yes Figure 5 Stereoscopic image of

[0025] Figure 8 It is a schematic diagram of the three-dimensional structure of the underwater sound collection mechanism of the present invention;

[0026] Figure 9This is a schematic diagram of the exploded assembly of the underwater sound collection mechanism of the present invention;

[0027] Figure 10 1 is a side view of the underwater sound collection mechanism of the present invention and a partial enlarged view of part I thereof;

[0028] Figure 11 It is a schematic axial cross-sectional view of the coaxially nested float body and annular magnet of the present invention;

[0029] Figure 12 This is a front view of the three-arm planar spring of the present invention;

[0030] Figure 13 It is a schematic diagram of the three-dimensional structure of the present invention after the central supporting ring and the float body with an embedded annular magnet are coaxially connected to the two three-arm planar springs;

[0031] Figure 14 yes Figure 13 Exploded assembly diagram of

[0032] Figure 15 yes Figure 13 An axial cross-sectional view of the device and a partial enlarged view of part II in the figure;

[0033] Figure 16 1. It is an assembly diagram and an exploded diagram of the fixed pole plate and the electromagnetic coil of the present invention;

[0034] Figure 17 This is a front view of the fixed plate blank before the acoustic damping hole array is formed in the present invention;

[0035] Figure 18 yes Figure 17 A three-dimensional cross-section view under the middle BB;

[0036] Figure 19 This is an axial cross-sectional perspective view of the assembly structure of the fixed pole plate and the electromagnetic coil of the present invention;

[0037] Figure 20 This is an axial cross-sectional perspective view of the underwater sound collection mechanism of the present invention;

[0038] Figure 21 It is a schematic axial cross-sectional view of the underwater acoustic channel cylinder including the underwater acoustic collection mechanism of the present invention;

[0039] Figure 22 1 is a schematic cross-sectional view of the three-dimensional structure of the neutral buoyancy dynamic electrode differential capacitance vector hydrophone of the present invention;

[0040] Figure 23 This is a schematic diagram of the frequency band expansion principle of the force balance negative feedback method of the present invention; DETAILED DESCRIPTION

[0041] The present invention will be further described in detail below with reference to the accompanying drawings.

[0042] like Figures 1 to 22 As shown, the neutral buoyancy dynamic electrode differential capacitive vector hydrophone of the present invention includes an underwater acoustic collection mechanism A, an underwater acoustic channel cylinder B, a pressure-resistant insulating liquid, a circuit board compartment C and a circuit board; a horizontally penetrating underwater acoustic channel is provided in the middle of the underwater acoustic channel cylinder B, and both ends of the underwater acoustic channel are respectively sealed by two underwater acoustic windows B3 in the underwater acoustic channel cylinder B. The underwater acoustic channel is filled with pressure-resistant insulating liquid and the underwater acoustic collection mechanism A is completely immersed in the pressure-resistant insulating liquid; the underwater acoustic collection mechanism A is coaxially fixed to the center of the underwater acoustic channel and is used to collect the underwater acoustic signal transmitted into the underwater acoustic channel through the pressure-resistant insulating liquid; the circuit board compartment C is located outside the underwater acoustic channel cylinder B and is waterproofly isolated from it, the circuit board is sealed in the circuit board compartment C and is signal-connected to the underwater acoustic collection mechanism A; the circuit board is used to process and output the underwater acoustic signal transmitted by the underwater acoustic collection mechanism A.

[0043] The underwater acoustic collection mechanism A includes two fixed pole plates 1, two spring pressure rings 2, two three-arm plane springs 3, a channel center bearing ring 4, a float body 5, an annular magnet 6 and two electromagnetic coils 7; the three-arm plane spring 3 includes a spring disc inner ring 3-1, a spring disc outer ring 3-2 and three arc-shaped connecting ribs 3-3 arranged coaxially and coplanarly with each other, and the three arc-shaped connecting ribs 3-3 are evenly distributed between the spring disc inner ring 3-1 and the spring disc outer ring 3-2 in the circumferential direction; the two three-arm plane springs 3 are respectively connected to the front of the channel center bearing ring 4 through the spring disc outer ring 3-2 on the outside. , and the rear end faces are coaxially fixedly connected; the two three-arm planar springs 3 are coaxially fixedly connected to the front and rear end faces of the float body 5 through the spring disc inner ring 3-1 at the center position; the annular magnet 6 is coaxially embedded in the center of the float body 5; the two electromagnetic coils 7 are respectively embedded and coaxially fixedly connected to the coil assembly ring groove 1-2 in the middle of the outer end face of the corresponding fixed pole plate 1; the spring pressure ring 2 is made of insulating material, and the two spring pressure rings 2 are respectively fixedly connected to the outer end faces of the corresponding spring disc outer ring 3-2; the two fixed pole plates 1 are respectively fixedly connected to the outer end faces of the corresponding spring pressure rings 2.

[0044] The underwater acoustic channel cylinder B is made of insulating material, which includes a cylindrical arc-shaped shell B1, two sound-gathering rings B2, two underwater acoustic windows B3, two clamping rings B4 and a cylinder radial sealing ring B5; the cylindrical arc-shaped shell B1 includes an integrally formed underwater acoustic channel shell B1-1 and a connecting ring seat B1-2 radially perpendicular to it; a horizontally penetrating underwater acoustic channel is opened in the axial center of the underwater acoustic channel shell B1-1, and the underwater acoustic collection mechanism A is coaxially fixed to the horizontal center position of the underwater acoustic channel shell B1-1 and is clamped and fixed by the front and rear clamping rings B4; the underwater acoustic window B3 includes an annular ring B3-1 and a sound-transmitting membrane B3-2 fixed on its inner wall, and the underwater acoustic window B3 is used to measure the underwater acoustic channel through its sound-transmitting membrane B3-2. The two ends of the channel shell B1-1 are sealed, and the sound-permeable membrane B3-2 is used to allow the underwater acoustic vibration signal to enter the underwater acoustic channel with high transmittance and isolate the contact between the pressure-resistant insulating liquid and seawater; each sound-focusing ring B2 presses the corresponding underwater acoustic window B3 with the front and rear end faces of the underwater acoustic channel shell B1-1 respectively; the connecting ring seat B1-2 is used to coaxially fix the cylindrical arc shell B1 and the circuit board bin C, and an axially through-bin hole B1-1-1 is provided in the center of the end face of the connecting ring seat B1-2; the cylindrical radial sealing ring B5 is coaxially fixed to the end face of the through-bin hole B1-1-1 and seals it; the cylindrical radial sealing ring B5 is used for electrical connection between the underwater acoustic collection mechanism A and the circuit board fixed inside the circuit board bin C.

[0045] The pressure-resistant insulating liquid is a low-viscosity liquid that has electrical insulation properties, a large bulk modulus, and a density close to that of seawater. The pressure-resistant insulating liquid fills the water acoustic channel shell B1-1 and completely immerses the water acoustic collection mechanism A in the pressure-resistant insulating liquid. The fixed plate 1 is made of metal material, and an array of axially penetrating sound-transmitting damping holes 1-1-1 is provided on the end face of the fixed plate 1. A coil assembly ring groove 1-2 is provided in the middle of the fixed plate 1 for installing and fixing the electromagnetic coil 7. The float body 5 is made of a low-density pressure-resistant material.

[0046] The pressure-resistant insulating liquid includes castor oil, silicone oil or transformer oil; preferably, the pressure-resistant insulating liquid is 25# transformer oil; preferably, the float body 5 described in the present invention is a low-density pressure-resistant material of epoxy resin with hollow glass beads solidified inside; the sound-transmitting membrane B3-2 is a rubber membrane; the annular magnet 6 is a radially magnetized magnetic ring; the radial stiffness of the three-arm planar spring 3 is at least 10 times its axial stiffness.

[0047] The spring disk inner ring 3-1, the float body 5 and the annular magnet 6 inside the two three-arm planar springs 3 together constitute a neutral buoyancy dynamic electrode mechanism; the three-arm planar spring 3 is made of metal conductor material, the two spring disk inner rings 3-1 are electrically short-circuited, and serve as the movable electrode plate of the differential capacitance sensing structure; the two fixed electrodes 1 are symmetrically and closely arranged on both sides of the neutral buoyancy dynamic electrode mechanism, and the movable electrode plate of the neutral buoyancy dynamic electrode mechanism and the two fixed electrodes 1 together constitute the differential capacitance sensing structure of the neutral buoyancy dynamic electrode differential capacitance vector hydrophone; the annular magnet 6 coaxially embedded in the center of the float body 5 and the two electromagnetic coils 7 coaxially embedded in the fixed electrode 1 together constitute a feedback motor for closed-loop feedback control of the neutral buoyancy dynamic electrode mechanism.

[0048] The acoustically transparent damping hole array 1-1-1 is used to apply fluid damping to the pressure-resistant insulating liquid carrying the hydroacoustic signal flowing through it, thereby equivalently forming motion damping for the neutrally buoyant moving electrode mechanism, thereby providing a basis for constructing the mass / damping equation.

[0049] The float body 5 is used to adjust the overall density of the neutral buoyancy moving electrode mechanism and make it close to the density of the pressure-resistant insulating liquid, and to make the difference between the overall density of the neutral buoyancy moving electrode mechanism and the density of seawater converge within the range of ±5%.

[0050] The circuit board includes a conditioning unit and a feedback unit; the conditioning unit is used for electromechanical signal conversion of the underwater acoustic vibration signal pickup structure of the neutral buoyancy dynamic electrode differential capacitive vector hydrophone; the feedback unit is used for closed-loop feedback control of the neutral buoyancy dynamic electrode mechanism to achieve frequency band expansion of the hydrophone.

[0051] The feedback unit of the circuit board includes at least two of the second-order differential feedback circuit, the first-order differential feedback circuit and the zero-order differential feedback circuit connected in parallel with each other; preferably, the feedback unit of the circuit board includes the second-order differential feedback circuit, the first-order differential feedback circuit and the zero-order differential feedback circuit connected in parallel with each other at the same time.

[0052] like Figure 23 As shown, the frequency band extension method based on the neutral buoyancy dynamic electrode differential capacitive vector hydrophone of the present invention includes the following steps:

[0053] Step 1: Design a pressure-resistant insulating liquid with a density close to that of seawater and a neutrally buoyant moving electrode mechanism, wherein the conditioning unit includes at least functional units such as an AC power supply, a charge amplifier unit, a phase-sensitive detection unit, and a low-pass filter unit, which are well-known in the field of automatic control. These units are then integrated into a differential capacitor operational amplifier circuit on a circuit board using known methods.

[0054] Step 1: Design a pressure-resistant insulating liquid with a density close to that of seawater and a neutrally buoyant moving electrode mechanism;

[0055] Step 2: Construct the motion equation of the underwater acoustic particle:

[0056] Assume that the underwater acoustic particle is located at the center of an aquatic channel with a length of l and a cross-sectional area of ​​A in the propagation direction of the underwater acoustic vibration signal. The sound pressure gradient in the underwater acoustic channel is Forces in the hydroacoustic channel The motion equation of the water sound particle constructed from this is:

[0057]

[0058] In formula (1), m W is the mass of the water sound particle, is the vibration acceleration of the water sound particle, ρ is the density of seawater, s is the complex frequency, v W is the vibration velocity of the water sound particle;

[0059] Step 3: Construct the response equation of the neutral buoyancy moving electrode mechanism under underwater acoustic vibration excitation:

[0060]

[0061] In formula (2), x p is the displacement of the neutral buoyancy moving electrode mechanism, m s =ρlA is the mechanical mass of the neutral buoyancy moving electrode mechanism, H s is the mechanical damping of the neutral buoyancy moving electrode mechanism, C s is the parallel mechanical stiffness of the two three-arm planar springs (3) and the two acoustically transparent membranes (B3-2);

[0062] Step 4: Build the conditioning circuit of the underwater acoustic vibration signal pickup structure:

[0063]

[0064] In formula (3), V o is the output voltage of the conditioning unit, D is the conversion ratio of the underwater acoustic vibration signal pickup structure, and K is the signal amplification factor;

[0065] Step 5: Construct a feedback function for closed-loop control of the underwater acoustic vibration signal pickup structure:

[0066]

[0067] In formula (4), V f is the output voltage of the feedback unit, V o is the input voltage of the feedback unit, k T is the gain of the second-order differential feedback circuit, k D is the gain of the first-order differential feedback circuit, k Ris the amplification factor of the zero-order differential feedback circuit;

[0068] Step 6: Construct the feedback motor transfer function:

[0069]

[0070] In formula (5), F f is the output force of the feedback motor, G f is the electromotive constant of the feedback motor, R is the series resistance of the two electromagnetic coils;

[0071] Step 7: Based on the force balance negative feedback control method and equations (1) to (5), the system transfer function of the neutral buoyancy dynamic electrode differential capacitance vector hydrophone including the closed-loop feedback link is obtained:

[0072]

[0073] In formula (6), m s is the mechanical mass of the neutral buoyancy moving electrode mechanism, s is the complex frequency;

[0074] is the equivalent mass generated by the feedback system;

[0075] is the equivalent damping generated by the system;

[0076] is the equivalent stiffness generated by the system;

[0077] m e , H e and C e Can be adjusted through the circuit system, The adjustment of can achieve the expansion of the frequency band of the hydrophone.

Claims

1. Neutral buoyancy dynamic electrode differential capacitance vector hydrophone, characterized by: The differential capacitive vector hydrophone comprises an underwater acoustic collection mechanism (A), an underwater acoustic channel cylinder (B), a pressure-resistant insulating liquid, a circuit board compartment (C), and a circuit board; a horizontally penetrating underwater acoustic channel is provided in the middle of the underwater acoustic channel cylinder (B), both ends of the underwater acoustic channel are sealed by two underwater acoustic windows (B3) in the underwater acoustic channel cylinder (B), the underwater acoustic channel is filled with pressure-resistant insulating liquid, and the underwater acoustic collection mechanism (A) is completely immersed in the pressure-resistant insulating liquid; the underwater acoustic collection mechanism (A) is coaxially fixed to the center of the underwater acoustic channel and is used to collect underwater acoustic signals transmitted into the underwater acoustic channel through the pressure-resistant insulating liquid; the circuit board compartment (C) is located outside the underwater acoustic channel cylinder (B) and is waterproofly isolated therefrom; the circuit board is sealed in the circuit board compartment (C) and is signal-connected to the underwater acoustic collection mechanism (A); the circuit board is used to process and output the underwater acoustic signals transmitted by the underwater acoustic collection mechanism (A); The underwater sound collection mechanism (A) comprises two fixed pole plates (1), two spring pressure rings (2), two three-arm plane springs (3), a channel center bearing ring (4), a float body (5), an annular magnet (6) and two electromagnetic coils (7); The spring disc inner ring (3-1), the float body (5) and the annular magnet (6) inside the two three-arm planar springs (3) together constitute a neutral buoyancy dynamic electrode mechanism; the three-arm planar spring (3) is made of a metal conductor material, the two spring disc inner rings (3-1) are electrically short-circuited, and serve as movable pole plates of a differential capacitance sensing structure; the two fixed pole plates (1) are symmetrically and closely arranged on both sides of the neutral buoyancy dynamic electrode mechanism, and the movable pole plates of the neutral buoyancy dynamic electrode mechanism and the two fixed pole plates (1) together constitute a differential capacitance sensing structure of a neutral buoyancy dynamic electrode differential capacitance vector hydrophone; the annular magnet (6) coaxially embedded in the center of the float body (5) and the two electromagnetic coils (7) coaxially embedded in the fixed pole plates (1) together constitute a feedback motor for closed-loop feedback control of the neutral buoyancy dynamic electrode mechanism.

2. The neutral buoyancy dynamic electrode differential capacitance vector hydrophone according to claim 1, characterized in that: The underwater sound collection mechanism (A) is a cylindrical structure as a whole. The three-arm plane spring (3) comprises a spring disc inner ring (3-1), a spring disc outer ring (3-2) and three arc-shaped connecting ribs (3-3) arranged coaxially and coplanar with each other. The three arc-shaped connecting ribs (3-3) are evenly distributed between the spring disc inner ring (3-1) and the spring disc outer ring (3-2) in the circumferential direction. The two three-arm plane springs (3) are respectively coaxially fixedly connected to the front and rear end surfaces of the channel center bearing ring (4) through the spring disc outer ring (3-2) outside the two three-arm plane springs (3). The two three-arm plane springs (3) are respectively The spring disc inner ring (3-1) at its center position is coaxially fixedly connected to the front and rear end surfaces of the float body (5); the annular magnet (6) is coaxially embedded in the center of the float body (5); the two electromagnetic coils (7) are respectively embedded and coaxially fixedly connected to the coil assembly ring groove (1-2) in the middle of the outer end surface of the corresponding fixed pole plate (1); the spring pressure ring (2) is made of insulating material, and the two spring pressure rings (2) are respectively fixedly connected to the outer end surface of the corresponding spring disc outer ring (3-2); the two fixed pole plates (1) are respectively fixedly connected to the outer end surface of the corresponding spring pressure ring (2).

3. The neutral buoyancy dynamic electrode differential capacitance vector hydrophone according to claim 1, characterized in that: The underwater acoustic channel cylinder (B) is made of insulating material and includes a cylindrical arc-shaped shell (B1), two sound-gathering rings (B2), two underwater acoustic windows (B3), two clamping rings (B4) and a cylinder radial sealing ring (B5); the cylindrical arc-shaped shell (B1) includes an integrally formed underwater acoustic channel shell (B1-1) and a connecting ring seat (B1-2) perpendicular to the radial direction thereof; a horizontally penetrating underwater acoustic channel is provided at the axial center of the underwater acoustic channel shell (B1-1); the underwater acoustic collection mechanism (A) is coaxially fixed to the horizontal center of the underwater acoustic channel shell (B1-1) and is connected to the front and rear clamping rings (B4) by the two clamping rings (B4) at the front and rear. ) is clamped and fixed; the underwater acoustic window (B3) includes an annular ring (B3-1) and a sound-transmitting membrane (B3-2) fixed on its inner wall; each sound-focusing ring (B2) presses the corresponding underwater acoustic window (B3) to the front and rear end faces of the underwater acoustic channel shell (B1-1) respectively; the connecting ring seat (B1-2) is used for coaxially fixing the cylindrical arc shell (B1) and the circuit board bin (C), and an axially through-bin hole (B1-1-1) is provided in the center of the end face of the connecting ring seat (B1-2); the cylindrical radial sealing ring (B5) is coaxially fixed to the end face of the bin hole (B1-1-1) and seals it.

4. The neutral buoyancy dynamic electrode differential capacitance vector hydrophone according to claim 2 or 3, characterized in that: The pressure-resistant insulating liquid is a low-viscosity liquid that has electrical insulation properties, a large bulk modulus, and a density close to that of seawater. The pressure-resistant insulating liquid fills the water sound channel shell (B1-1) and completely immerses the water sound collection mechanism (A) in the pressure-resistant insulating liquid. The fixed plate (1) is made of metal material, and an array of axially penetrating sound-transmitting damping holes (1-1-1) is provided on the end face of the fixed plate (1) to apply fluid damping to the pressure-resistant insulating liquid flowing therethrough. A coil assembly ring groove (1-2) is provided in the middle of the fixed plate (1) for mounting a fixed electromagnetic coil (7). The float body (5) is made of a low-density pressure-resistant material.

5. The neutral buoyancy dynamic electrode differential capacitance vector hydrophone according to claim 4, characterized in that: Pressure-resistant insulating liquids include castor oil, silicone oil, or transformer oil; The float body (5) is a low-density, pressure-resistant material made of epoxy resin with hollow glass beads solidified inside; The sound-transmitting membrane (B3-2) is a rubber membrane; The annular magnet (6) is a radially magnetized magnetic ring; The radial rigidity of the three-arm planar spring (3) is at least 10 times its axial rigidity.

6. The neutral buoyancy dynamic electrode differential capacitance vector hydrophone according to claim 4, characterized in that: The pressure-resistant insulating liquid is 25# transformer oil.

7. The neutral buoyancy dynamic electrode differential capacitance vector hydrophone according to claim 6, characterized in that: The difference between the overall density of the neutral buoyancy dynamic electrode mechanism and the density of seawater is ±5%.

8. The neutral buoyancy dynamic electrode differential capacitance vector hydrophone according to claim 1, characterized in that: The circuit board includes a conditioning unit and a feedback unit; the conditioning unit is used for electromechanical signal conversion of the underwater acoustic vibration signal pickup structure of the neutral buoyancy dynamic electrode differential capacitive vector hydrophone; the feedback unit is used for closed-loop feedback control of the neutral buoyancy dynamic electrode mechanism to achieve frequency band expansion of the hydrophone.

9. The neutral buoyancy dynamic electrode differential capacitance vector hydrophone according to claim 8, characterized in that: The feedback unit of the circuit board includes at least two of a second-order differential feedback circuit, a first-order differential feedback circuit and a zero-order differential feedback circuit connected in parallel with each other.

10. The neutral buoyancy dynamic electrode differential capacitance vector hydrophone according to claim 9, characterized in that: The feedback unit of the circuit board includes a second-order differential feedback circuit, a first-order differential feedback circuit and a zero-order differential feedback circuit connected in parallel.

11. A method for extending the frequency band of a neutral buoyancy dynamic electrode differential capacitance vector hydrophone according to any one of claims 1 to 10, characterized in that: The method comprises the following steps: Step 1: Design a pressure-resistant insulating liquid with a density close to that of seawater and a neutrally buoyant moving electrode mechanism; Step 2: Construct the motion equation of the underwater acoustic particle: Assume that the underwater acoustic particle is located at the center of an aquatic channel with a length of l and a cross-sectional area of ​​A in the propagation direction of the underwater acoustic vibration signal. The sound pressure gradient in the underwater acoustic channel is Forces in the hydroacoustic channel The motion equation of the water sound particle constructed from this is: In formula (1), m W is the mass of the water sound particle, is the vibration acceleration of the water sound particle, ρ is the density of seawater, s is the complex frequency, v W is the vibration velocity of the water sound particle; Step 3: Construct the response equation of the neutral buoyancy moving electrode mechanism under underwater acoustic vibration excitation: In formula (2), x p is the displacement of the neutral buoyancy moving electrode mechanism, m s =ρlA is the mechanical mass of the neutral buoyancy moving electrode mechanism, H s is the mechanical damping of the neutral buoyancy moving electrode mechanism, C s is the parallel mechanical stiffness of the two three-arm planar springs (3) and the two acoustically transparent membranes (B3-2); Step 4: Build the conditioning circuit of the underwater acoustic vibration signal pickup structure: In formula (3), V o is the output voltage of the conditioning unit, D is the conversion ratio of the underwater acoustic vibration signal pickup structure, and K is the signal amplification factor; Step 5: Construct a feedback function for closed-loop control of the underwater acoustic vibration signal pickup structure: In formula (4), V f is the output voltage of the feedback unit, V o is the input voltage of the feedback unit, k T is the gain of the second-order differential feedback circuit, k D is the gain of the first-order differential feedback circuit, k R is the amplification factor of the zero-order differential feedback circuit; Step 6: Construct the feedback motor transfer function: In formula (5), F f is the output force of the feedback motor, G f is the electromotive constant of the feedback motor, R is the series resistance of the two electromagnetic coils; Step 7: Based on the force balance negative feedback control method and equations (1) to (5), the system transfer function of the neutral buoyancy dynamic electrode differential capacitance vector hydrophone including the closed-loop feedback link is obtained: In formula (6), is the equivalent mass generated by the feedback system; is the equivalent damping generated by the system; is the equivalent stiffness generated by the system; m e , H e and C e Can be adjusted through the circuit system, The adjustment of can achieve the expansion of the frequency band of the hydrophone.

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