An underwater vehicle low frequency broadband vibration reduction device

Abstract

The application discloses an unmanned underwater vehicle low-frequency wide-range damping device, which comprises a hollow-structured cylinder segment, end covers arranged at the axial two ends of the cylinder segment and surrounding the cylinder segment to form a closed chamber, an elastic structure arranged in the chamber and connected with the end covers, and a liquid medium filled in the chamber and immersed in the elastic structure; wherein the chamber is symmetrically distributed along the circumference of the cylinder segment. The application breaks the vibration propagation path along the continuous shell through the symmetric chamber layout of the cylinder segment, utilizes the fluid-structure coupling system composed of the elastic structure and the liquid medium to play the liquid additional mass effect and viscous damping dissipation characteristics, significantly improves the capture and suppression ability of low-frequency characteristic noise, and meanwhile, the liquid medium in the closed chamber can balance the external hydrostatic pressure, ensures the stability of the dynamic performance of the device in the full sea depth environment, effectively reduces the interference of the self-noise of the underwater vehicle on the bow acoustic load, and improves the sensitivity of acoustic detection.

Description

Technical Field

[0001] This invention belongs to the field of underwater autonomous vehicle technology, and particularly relates to a low-frequency wide-range vibration reduction device for unmanned underwater vehicles. Background Technology

[0002] As unmanned underwater vehicles (UUVs) develop towards higher performance, longer endurance, and greater stealth, the requirements for their acoustic reconnaissance sensitivity are increasing. The self-noise of autonomous underwater vehicles mainly originates from the mechanical vibrations generated by the propulsion system, motors, and servo mechanisms. These vibrations are transmitted along the vehicle's hull and internal support structure to the bow acoustic load area, creating strong near-field interference and severely limiting the hydrophone's ability to detect distant, weak targets. Currently, acoustic management of underwater vehicles has become a core aspect of improving their overall combat effectiveness. How to cut off the transmission path of vibration from the power source to the acoustic receiver and construct a full-frequency, multi-dimensional acoustic blocking interface has become a research focus in the field of underwater unmanned detection equipment.

[0003] However, existing vibration reduction and noise reduction methods have significant limitations in addressing low-frequency, wide-range noise from submersibles. On one hand, traditional single-stage elastic isolators or damping layers are often only effective against high-frequency vibrations. For low-frequency structural noise with high energy and strong penetrating power, they lack sufficient added mass and nonlinear dissipation mechanisms, making deep attenuation difficult. On the other hand, conventional vibration isolation components are usually installed inside the cabin, separate from the external hull. Under the high pressure conditions of the deep sea, they are prone to losing their vibration reduction performance due to material stiffness drift or structural instability, and they are also unable to address lateral radiated sound propagating along the skin. Furthermore, existing technologies lack effective fluid-structure interaction energy dissipation structures, making it impossible to balance structural strength and wide-band vibration absorption within a compact space. Therefore, there is an urgent need for a low-frequency, wide-range vibration reduction device that can conform to the vehicle hull, possess multi-stage impedance matching, and fluid-structure interaction characteristics to eliminate "sound bridges" in existing structures and improve acoustic stealth performance. Summary of the Invention

[0004] In view of the problems existing in the prior art, such as insufficient low-frequency vibration attenuation capability, unstable vibration reduction performance under high pressure environment in the deep sea, and the inability to block lateral sound radiation and fluid-induced noise due to the separation of the vibration reduction device from the submersible shell, the present invention provides a low-frequency wide-range vibration reduction device for unmanned underwater vehicles.

[0005] This invention is implemented as follows: a low-frequency wide-range vibration reduction device for an unmanned underwater vehicle, characterized in that it includes a cylindrical section, end caps, an elastic structure, and a liquid medium; the cylindrical section is a hollow structure, and the interior of the cylindrical section has multiple chambers symmetrically distributed along the circumference; the end caps are disposed at both ends of the cylindrical section and form closed chambers with the cylindrical section; the elastic structure is disposed in the chamber and connected to the end caps; the liquid medium fills the chamber and immerses the elastic structure.

[0006] The present invention provides a low-frequency wide-range vibration reduction device for unmanned underwater vehicles, which has the following significant advantages and technical effects compared with the prior art: First, this invention constructs a multi-path vibration reduction configuration with spatial symmetry by setting up a hollow cylindrical section and symmetrically distributing multiple chambers within it. This structural design allows the vibration reduction device to be directly integrated into the submersible's structural sequence, not only bearing the necessary mechanical loads but also breaking the path of vibration propagation along the continuous metal shell at the structural source through the discontinuous physical interface formed by the chambers. The circumferentially symmetrically distributed chambers ensure the consistency of the device's dynamic characteristics in all radial directions, effectively suppressing the off-center load transmission problem caused by load fluctuations during dynamic conditions such as turning and pitching, and solving the technical problems of existing vibration reduction structures being unable to adapt to complex dynamic environments and having insufficient lateral sound radiation blocking capabilities.

[0007] Secondly, this invention introduces a fluid-structure interaction system between an elastic structure and a liquid medium within a closed cavity, significantly improving the attenuation capability for low-frequency vibrations. The elastic structure immersed in the liquid utilizes the added mass effect of the liquid to lower the system's natural frequency without increasing physical space, enabling it to accurately capture and suppress low-frequency characteristic noise generated by propulsion systems, etc. Simultaneously, the shear damping effect generated by the liquid medium during the vibration of the mass block provides an energy dissipation rate far exceeding that of traditional dry vibration isolators, achieving efficient absorption of low-frequency and broadband vibration energy. This fluid-structure interaction mechanism overcomes the problems of insufficient low-frequency attenuation capability and narrow bandwidth inherent in existing technologies that rely solely on elastic elements.

[0008] Finally, this invention employs an integral design filled with a liquid medium and sealed by end caps, enhancing the performance stability of the device in extreme deep-sea environments. This design ensures that the device maintains stable damping characteristics and frequency response across the entire ocean depth range, from shallow to deep water. Furthermore, the direct assembly and sealing of the cylindrical section and end caps achieves functional integration of the vibration damping device with the submersible's fuselage, avoiding the cavity resonance and fluid-induced vibrations caused by the separation of traditional internal vibration isolators from the hull, significantly improving the submersible's acoustic stealth performance under actual operating conditions.

[0009] In the above technical solution, preferably, the cylinder segment is made of vibration-damping material, and metal face rings are provided at both ends of the cylinder segment. The metal face rings are fixedly connected to the cylinder segment through a vulcanization process to form a multi-level impedance change region in the vibration propagation path.

[0010] In the above technical solution, preferably, the metal face ring is provided with a hole feature, and the end cap is provided with a cylindrical boss, the cylindrical boss and the hole feature are tightly nested and sealed.

[0011] In the above technical solution, preferably, the number of chambers is an even number between 2 and 8, and they are evenly and symmetrically distributed along the circumference of the cylindrical section, so that the dynamic characteristics of the device remain consistent in different radial directions.

[0012] In the above technical solution, preferably, the elastic structure includes an elastic element and a mass block. The elastic element is fixed on the end cap and is fixedly connected to the mass block. Under inertia, the mass block couples with the liquid medium through shearing and pressure fluctuations.

[0013] In the above technical solution, preferably, the elastic element is a spring or a metal sheet.

[0014] In the above technical solution, preferably, the end cap includes a first end cap and a second end cap located on both sides of the cylindrical section; the elastic structure is respectively installed on the first end cap and the second end cap to form an axial double-end vibration absorption layout at both ends of the same chamber.

[0015] In the above technical solution, preferably, the elastic structure located on the first end cap and the elastic structure located on the second end cap have different stiffness parameters or mass parameters, so as to form multiple differentiated tuning points and broaden the attenuation frequency band.

[0016] In the above technical solution, preferably, the end cap is provided with a filling port that communicates with the chamber, and the filling port is sealed by a sealing threaded plug.

[0017] In the above technical solution, preferably, one end of the vibration damping device is connected to the main body of the submersible via a connector, and the other end is connected to the hydrophone via an acoustic load mounting bracket.

[0018] In summary, this technical solution further utilizes heterogeneous material vulcanization and nested sealing structures to ensure structural reliability under deep-sea high pressure while suppressing structural acoustic transmission through impedance mismatch. Combined with the centrally symmetrical layout of the chambers and the internal fluid-structure interaction vibration absorption mechanism, it achieves precise capture and efficient dissipation of low-frequency line spectrum noise through the added mass of the liquid and viscous damping. Furthermore, the axial dual-end differentiated tuning design further broadens the effective vibration reduction bandwidth, ensuring the extreme stability of the bow acoustic load detection environment under complex maneuvering conditions. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the vibration reduction device described in this invention; Figure 2 This is a schematic diagram of the connection structure between the metal face ring and the cylinder section in the vibration damping device; Figure 3 This is a schematic diagram of the internal structure of the cylinder section in the vibration damping device; Figure 4This is a schematic diagram of the end cap structure of the vibration damping device; Figure 5 This is a schematic diagram of the installation structure of the elastic structure in the vibration damping device; Figure 6 This is a schematic diagram of the working state of the vibration reduction device described in this invention; Figure 7 This is a cross-sectional view of the vibration damping device described in this invention in its working state. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0021] This embodiment provides a low-frequency wide-range vibration reduction device for unmanned underwater vehicles (UUVs), which aims to solve the problem of wide-frequency mechanical vibrations generated by the UUV's propulsion system, motors, and servo motors being transmitted to the bow acoustic load area. To further illustrate the structure of this invention, a detailed description is provided below in conjunction with the accompanying drawings: like Figures 1 to 3 As shown, the vibration damping device includes a cylindrical section 1, end caps 2, an elastic structure, and a liquid medium. The cylindrical section is a hollow structure with multiple chambers symmetrically distributed circumferentially inside. The end caps are located at both ends of the cylindrical section along its axial direction and are connected to the cylindrical section by circumferentially distributed bolts, thus forming a closed chamber 3 in cooperation with the internal structure of the cylindrical section.

[0022] The elastic structure is disposed in the cavity and connected to the end cap. The liquid medium fills the cavity and completely submerges the elastic structure, thereby dissipating vibration energy through fluid-structure interaction.

[0023] In terms of specific structure, the cylindrical section is made of a vibration-damping material with high internal loss characteristics. In this embodiment, the cylindrical section is made of rubber, utilizing the internal friction of rubber molecules to initially attenuate high-frequency elastic waves.

[0024] In this embodiment, to facilitate assembly, the end cap is designed as a split component, with a thin metal ring 4 provided on one side of the corresponding cylindrical section. Both axial end faces of the cylindrical section are coaxially connected to the metal rings. To ensure the connection strength and airtightness of the metal and non-metal materials under deep-water, high-pressure conditions, the covering surface of the metal ring is pre-polished and coated with adhesive. Subsequently, it is integrally fixed to the rubber cylindrical section through a high-temperature, high-pressure vulcanization process, forming a metal end face for the cylindrical section. This combination of heterogeneous materials not only improves structural rigidity but also creates a significant multi-level impedance variation region along the vibration propagation path, involving metal, elastomer, and metal, inducing multiple reflections and scatterings of vibration energy at the interface.

[0025] Please see Figure 4 The metal face ring has a machined hole, and the inner side of the end cap has a matching cylindrical boss 2-1. In the assembled state, the cylindrical boss and the hole fit tightly together and achieve radial positioning. To further enhance the sealing effect, a sealing ring can be provided between the mating surfaces of the cylindrical boss and the hole, or a bolt preload can be used to achieve end-face sealing at the contact surface between the end cap and the metal face ring to prevent leakage of the internal liquid medium under the hydrostatic pressure difference caused by the deep descent of the submersible.

[0026] Considering the load-bearing reliability and acoustic symmetry of the rubber section, the number of chambers is set to an even number between 2 and 8, and they are evenly distributed symmetrically along the circumference of the cylindrical section. Specifically, they are formed inside the cylindrical section, that is, radial dividing ribs are provided inside the cylindrical section. The side of the dividing ribs near the metal face ring leaves a gap with the metal face ring to ensure communication between the chambers. This layout enables the vibration damping device to maintain a high degree of consistency in its structural dynamic characteristics in different radial directions, ensuring that the aircraft can effectively suppress acoustic interference caused by off-center load vibration transmission even under unsteady conditions such as turning and pitching.

[0027] Please see Figure 5 The elastic structure includes an elastic element 5 and a mass block 6, serving as the core vibration-absorbing unit in this embodiment. One end of the elastic element is fixed to the protrusion inside the end cap by bolts, and the other end is fixedly connected to the mass block.

[0028] The elastic element can be a spring or a metal sheet. The system's support stiffness can be flexibly adjusted by changing the spring's wire diameter and number of turns, or the metal sheet's thickness and material. To ensure the mass block does not rigidly collide with the cavity wall during reciprocating vibration within the chamber, the radial dimension of the mass block is designed to be smaller than the inner diameter of the chamber, thus maintaining an annular fluid channel between the mass block and the cavity wall. When structural vibration is transmitted to the end cap, the mass block, under inertia, generates a reciprocating displacement relative to the end cap, forcing the liquid medium within the chamber to generate a high-speed extrusive or shear flow through this annular fluid channel. This fluid-structure interaction not only utilizes the added mass effect of the liquid to lower the system's natural frequency but also dissipates a significant amount of vibrational energy using the liquid's viscosity.

[0029] In this embodiment, the liquid medium fills each symmetrically distributed cavity, completely immersing the mass block and the elastic element. The liquid medium is preferably silicone oil or special hydraulic oil with a high flash point, stable chemical properties, and minimal viscosity change with temperature. Its filling rate must reach at least 95% of the cavity volume, with a very small proportion of expansion space or compensation structure reserved to accommodate volume changes of the vehicle at different sea depths and ambient temperatures. The presence of the liquid medium allows the device to suppress structurally transmitted noise while also absorbing some of the acoustic energy penetrating the shell through the fluid's elastic damping effect. Furthermore, due to the incompressibility of the liquid, the fluid pressure field formed within the cavity provides additional radial constraint to the elastic element, enhancing the motion stability of the mass block under complex overload conditions and avoiding the instability that may occur with a purely mechanical spring under lateral impact.

[0030] The end caps include a first end cap and a second end cap located on both sides of the cylindrical section. As a preferred embodiment, the elastic structure is installed only on the end cap on the side closest to the submersible body (i.e., the vibration source side), using a single-sided cantilevered oscillator structure to pre-treat the vibration before it enters the cylindrical section. This layout is simple in structure and helps to simplify the fluid pressure distribution model within the chamber.

[0031] As an alternative extended implementation, to further broaden the attenuation bandwidth, elastic structures can be installed on the first and second end caps respectively, thereby forming an axial double-end vibration absorption layout at both ends of the same chamber. In this alternative, the elastic structures on both sides can be configured with different stiffness or mass parameters, utilizing the interference effect generated by multi-frequency tuning to eliminate the vibration reduction blind zone that may exist in a single-oscillator system, thus adapting to more complex broadband mechanical excitation environments.

[0032] The end cap has a filling port 2-2 on its radially outer side or end face, connecting to the chamber. To ensure the purity of the liquid medium inside the chamber and to eliminate residual air from the assembly, the filling process is recommended to be carried out in a vacuum environment. After the liquid fills the chamber and air bubbles are removed, it is tightened using a plug with a high-strength sealing thread. A corrosion-resistant copper gasket or fluororubber O-ring can be added between the plug and the filling port to ensure that the filling interface does not experience fatigue leakage under high-pressure cyclic loads in the deep sea. In addition, a small bellows-type pressure compensation structure can be reserved on the inner wall of the chamber to balance the effect of the slight elastic deformation of the shell caused by changes in sea depth on the internal fluid pressure, ensuring the constant dynamic performance of the vibration damping device throughout the entire depth range.

[0033] To achieve interconnectivity of the entire electrical system of the submersible, the cylindrical section and each end cap of this device are equipped with coaxial, collinear central through holes at their central axes. After assembly, these through holes form a sealed cable passage that runs through the entire device, specifically for laying power cables and signal transmission optical fibers connecting the bow acoustic loads and the main control compartment of the submersible. This axial cable passage design not only ensures that communication lines avoid the dynamic movement areas of the internal elastic structure, preventing cable wear and breakage due to mechanical vibration or reciprocating impacts from the mass blocks, but also utilizes the spatial stability of the central axis to reduce the interference of the cable bundle on the dynamic characteristics of the vibration reduction system. Simultaneously, this cable passage, in conjunction with dedicated watertight penetration components, maintains the sealing reliability of each chamber after it is independently filled with liquid media, while ensuring the continuity of wiring between compartments, achieving a high degree of unity between structural vibration reduction functions and the requirements of submersible system integration.

[0034] Please see Figure 6 and Figure 7 In the overall assembly, the vibration damping device serves as a core connecting segment of the submersible. One end is connected to the submersible body 7 (such as the power compartment section) via high-strength bolts and locating pins, receiving the initial vibration excitation from the propulsion system; the other end is connected to precision detection equipment such as hydrophones via acoustic load mounting brackets 8 and has a forward fairing installed. During installation, the end caps at both ends of the cylindrical section ensure the coaxiality of the submersible axis through the rigid reference provided by the metal face rings. This assembly sequence of metal, vibration damping material, and metal allows the device to withstand longitudinal thrust and bending moment while blocking high-frequency structural sound through the rubber cylindrical section and precisely absorbing low-frequency characteristic vibrations through internal elastic elements, mass blocks, and a fluid-structure interaction system. After assembly, the outer surface of the cylindrical section smoothly transitions with the adjacent compartments, forming part of the submersible's external fluid configuration. This conformal design not only suppresses fluid-induced vibration noise at high speeds by eliminating external protrusions and internal cavities, but also cleverly utilizes the compression effect of deep-sea hydrostatic pressure on the cylindrical material, improving the loss factor of the vibration-damping material under extreme conditions. More importantly, while maintaining the overall structural rigidity and navigation stability of the submersible, this solution creates an acoustic impedance break at the entire outer shell level through a sudden change in the modulus of the outer shell material, greatly reducing the lateral radiation effect of noise propagating along the shell skin.

[0035] The vibration damping device provided in this embodiment constructs a multi-stage vibration filtering system through impedance mismatch in the cylindrical section material, symmetrical layout of the chamber, and dissipation mechanism of fluid-structure interaction within the chamber. Compared to traditional single vibration isolators, this device utilizes the added mass and viscous damping of the liquid medium to successfully extend the vibration suppression frequency band down to the low-frequency region without significantly increasing the device volume, effectively covering the propulsion motor frequency and its low-order harmonic noise of the submarine. Simultaneously, the adjustable parameters of the multiple oscillators within the chamber provide engineering feasibility for targeted noise attenuation of specific noise spectra for different types of submarines, significantly improving the survivability and reconnaissance sensitivity of the submarine in complex acoustic environments.

[0036] Furthermore, the device of this invention features separation of dynamic and static loads and stiffness decoupling. Unlike traditional vibration dampers that fail at low frequencies due to material pre-compression under deep-sea high pressure, this solution utilizes the pressure balance mechanism between the outer shell and the internal incompressible liquid medium, ensuring that the internal elastic structure maintains stable dynamic stiffness. Experiments have shown that with increasing sea depth, the damping enhancement effect generated by the compression of the shell material and the low-frequency notch effect of the internal fluid-structure interaction system form a dynamic gain complementarity, ensuring that the device can accurately lock and suppress the low-frequency characteristic line spectrum noise of the propulsion system under all sea depth conditions, exhibiting an adaptive optimization effect of vibration reduction performance with environmental pressure.

[0037] Example 2 To achieve precise suppression of specific fundamental frequency noise from the propulsion motor of a submersible, this solution provides a vibration absorption frequency design model based on the fluid-structure interaction effect. The equivalent physical parameters of the mass block in the elastic structure are related to the target suppression frequency. The following empirical design formula must be satisfied:

[0038] in: The static stiffness of the elastic element; The mass of the mass block itself; The density of the liquid medium being filled; The volume of water drained by the mass block; Let be the cross-sectional area of ​​the mass block in the direction of vibration; The cross-sectional area of ​​the chamber; This is the fluid resistance correction factor, with a value range of [value range missing]. .

[0039] Traditional mechanical vibration absorption calculation formulas are not applicable to the fluid-structure interaction environment of this scheme. This model introduces an additional mass correction term:

[0040] It reveals the ratio of the annular flow channel area between the mass block and the cavity wall (i.e. and The relationship between the frequency and the vibration reduction frequency. When designers determine the main noise frequency of the submarine through spectrum analysis... Then, the optimal cross-sectional area of ​​the mass block can be derived by working backwards from this formula. This design model ensures that the vibration reduction frequency band can be customized simply by adjusting the gap width between the mass block and the chamber wall without changing the overall dimensions of the device. Experiments show that when the cross-sectional area ratio designed according to this formula is... In In the intermediate range, the shear dissipation power of the liquid medium in the annular channel reaches its peak, which can generate a depth of... The above narrowband notch filters effectively eliminate characteristic line spectrum noise of the propulsion system at its source.

[0041] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A low-frequency wide-range vibration reduction device for unmanned underwater vehicles, characterized in that, include: The cylindrical section has a hollow structure, and the interior of the cylindrical section has multiple chambers symmetrically distributed along the circumference; End caps are disposed at both axial ends of the cylindrical section and form a closed chamber with the cylindrical section; An elastic structure is disposed within the cavity and connected to the end cap; as well as A liquid medium is filled in the cavity and submerges the elastic structure.

2. The low-frequency wide-range vibration reduction device for unmanned underwater vehicles according to claim 1, characterized in that, The cylindrical section is made of vibration-damping material, and metal face rings are provided at both ends of the cylindrical section. The metal face rings are fixedly connected to the cylindrical section through a vulcanization process to form a multi-level impedance change region in the vibration propagation path.

3. The low-frequency wide-range vibration reduction device for unmanned underwater vehicles according to claim 2, characterized in that, The metal face ring has a hole feature, and the end cap has a cylindrical boss. The cylindrical boss and the hole feature are tightly nested and sealed.

4. The low-frequency wide-range vibration reduction device for unmanned underwater vehicles according to claim 1, characterized in that, The number of chambers is an even number, between 2 and 8, and they are evenly and symmetrically distributed along the circumference of the cylindrical section to ensure that the dynamic characteristics of the device remain consistent in different radial directions.

5. The low-frequency wide-range vibration reduction device for unmanned underwater vehicles according to claim 1, characterized in that, The elastic structure includes an elastic element and a mass block. The elastic element is fixed to the end cap and is fixedly connected to the mass block. Under inertia, the mass block is coupled with the liquid medium to generate shear and pressure fluctuations.

6. The low-frequency wide-range vibration reduction device for unmanned underwater vehicles according to claim 5, characterized in that, The elastic element is a spring or a metal sheet.

7. The low-frequency wide-range vibration reduction device for unmanned underwater vehicles according to claim 5, characterized in that, The end caps include a first end cap and a second end cap located on both sides of the cylindrical section; the elastic structure is respectively installed on the first end cap and the second end cap to form an axial double-end vibration absorption layout at both ends of the same chamber.

8. The low-frequency wide-range vibration reduction device for unmanned underwater vehicles according to claim 7, characterized in that, The elastic structure on the first end cap and the elastic structure on the second end cap have different stiffness or mass parameters to form multiple differentiated tuning points and broaden the attenuation frequency band.

9. The low-frequency wide-range vibration reduction device for unmanned underwater vehicles according to claim 1, characterized in that, The end cap is provided with a filling port that communicates with the chamber, and the filling port is sealed by a sealing threaded plug.

10. The low-frequency wide-range vibration reduction device for unmanned underwater vehicles according to claim 1, characterized in that, One end of the vibration damping device is connected to the main body of the submersible via a connector, and the other end is connected to the hydrophone via an acoustic load mounting bracket.

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