Underwater acoustic stealth positioning system

Abstract

The invention discloses an underwater acoustic stealth positioning system, and the system comprises a cylindrical underwater Lunberg stealth lens which is used for stealth and is provided with a stealth accommodation groove in the center; a housing; and one end of the positioner is connected with the focal point of the edge of the underwater acoustic Lunberg stealth lens, and the other end of the positioner extends towards the radial outer side of the underwater acoustic Lunberg stealth lens. Therefore, the underwater acoustic Lunberg stealth lens is arranged to be cylindrical, and the stealth accommodating groove is formed in the middle of the underwater acoustic Lunberg stealth lens, so that an object in the stealth accommodating groove can be stealthy and is prevented from being detected; the acoustic signals transmitted to the underwater acoustic Lunberg stealth lens by the detector are focused at the focal point of the edge of the underwater acoustic Lunberg stealth lens and are received by the positioner, so that the position of the detector is reversely positioned, the stealth and positioning functions are achieved, the structure is simple, manufacturing is convenient, and cost is low.

Description

Technical Field

[0001] The present invention relates to the field of underwater stealth technology, and more particularly to an underwater acoustic stealth positioning system. Background Art

[0002] With the rapid development of marine resource exploitation and underwater military activities, the acoustic stealth and active detection capabilities of underwater devices have become key technological requirements. Traditional underwater stealth technologies mainly rely on sound-absorbing materials (such as sonar tiles) or structural shape optimization, but these methods have inherent defects such as limited frequency bands, sensitivity to incident angles, and difficulty in integrating with functional modules. For example, a stealth device based on hydrogel realizes acoustic wave diffraction through the composite design of a rigid sheet and a flexible layer, but its multi-layer structure results in a large volume and is difficult to adapt to the requirements of dynamic scenarios. In addition, existing active positioning technologies mostly rely on independent sonar systems, resulting in bulky devices and the stealth performance being easily invalidated due to the exposure of external sensors, making it difficult to meet the requirements of high concealment and multi-functional collaboration for devices such as underwater unmanned submersibles (UUS).

[0003] In terms of acoustic stealth theory, although the linear transformation method provides a basic framework for the design of stealth devices, the anisotropic parameters generated by it often lead to impedance mismatch, limiting the broadband performance. For example, a five-mode material stealth blanket optimizes the impedance matching through quasi-conformal transformation, but its function is limited to static stealth and it cannot work in collaboration with an active detection module. Moreover, it is difficult to balance the adaptability to the underwater high-pressure environment and the dynamic switching requirements of the stealth-positioning mode in the microstructure design of five-mode materials. For example, although a stealth device based on hydrogel can suppress the conversion of shear waves through sub-wavelength structures, its material mechanical properties are difficult to adapt to the deep-sea high-pressure environment and lack an integrated design with the active detection function. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, an object of the present invention is to propose an underwater acoustic stealth positioning system, which not only has better stealth performance but also can perform active reverse positioning.

[0005] An underwater acoustic stealth positioning system according to an embodiment of the present invention includes: a housing; an underwater Luneburg stealth lens, the underwater Luneburg stealth lens is arranged in a ring shape in the housing, a stealth accommodation groove is provided in the middle of the underwater Luneburg stealth lens, an object to be stealth is suitable to be placed in the stealth accommodation groove, and a focal point is provided at the edge of the underwater Luneburg stealth lens; wherein, the material property distribution of the underwater Luneburg stealth lens is:

[0006]

[0007] wherein, a and b are respectively the inner diameter and outer diameter of the underwater Luneburg stealth lens; ρ n, K n is the density and modulus of the circular Luneburg lens before transformation, ρ0 = 1000 kg / m 3 , K0 = 2.25 GPa are the density and modulus of the background medium; ρ, K r , K θ are respectively the density, radial modulus and tangential modulus of the underwater acoustic Luneburg invisibility lens; is the refractive index of the cylindrical Luneburg lens before transformation; parameter The underwater acoustic Luneburg invisibility lens is obtained by linearly mapping a cylindrical Luneburg lens, mapping a two-dimensional circle to a two-dimensional ring through a mapping function, and the radial mapping relationship from the circular region R ∈ [0, b] in the virtual space to the annular region r ∈ [a, b] in the physical space in the polar coordinate system: R = f(r) and Θ = θ, where,

[0008] Thus, by setting the underwater acoustic Luneburg invisibility lens as a cylinder and arranging an invisibility accommodation groove in the middle of the underwater acoustic Luneburg invisibility lens, the object inside the invisibility accommodation groove can be made invisible and avoid being detected. Further, the acoustic wave signal transmitted by the detector to the underwater acoustic Luneburg invisibility lens will be focused at the focal point on the edge of the underwater acoustic Luneburg invisibility lens and received by the locator, thereby reversely locating the position of the detector. In this way, it not only has the functions of invisibility and positioning, but also has a simple structure, is convenient to manufacture, and has a low cost.

[0009] In some examples of the present invention, the underwater acoustic Luneburg invisibility lens includes multiple layers of five-mode material layers, the five-mode material layers are in a circular ring shape, and the multiple layers of five-mode material layers are concentrically arranged and stacked in the radial direction to form the cylindrical underwater acoustic Luneburg invisibility lens.

[0010] In some examples of the present invention, the five-mode material layer has multiple unit cells, and each unit cell includes an inclined plate and a mass block. The inclined plate includes a first inclined plate, a second inclined plate and a third inclined plate. The first inclined plate extends in the radial direction. The second inclined plate and the third inclined plate are both connected to the outer radial end of the first inclined plate and form an angle φ with the first inclined plate. The angle formed between the second inclined plate and the third inclined plate is φ. The mass block includes a first mass block and a second mass block. The first mass block is arranged on the first inclined plate, and the second mass block is arranged on the second inclined plate.

[0011] In some examples of the present invention, in each five-mode material layer, multiple unit cells are arranged in the circumferential direction, and the second inclined plate of one of the adjacent two unit cells is connected to the third inclined plate of the other.

[0012] In some examples of the present invention, two adjacent layers in the radial direction of the multiple layers of the five-mode material layer are respectively set as the first five-mode material layer and the second five-mode material layer. The first five-mode material layer is located radially outside the second five-mode material layer. The inner ends of the first inclined plates of the first five-mode material layer are respectively connected to the outer ends of the second inclined plates and the outer ends of the third inclined plates of two adjacent cell units in the second five-mode material layer.

[0013] In some examples of the present invention, in the direction extending from the radial outside to the inside of the underwater acoustic Luneburg invisibility lens, the mass blocks in the multiple layers of the five-mode material layer gradually decrease.

[0014] In some examples of the present invention, the cell unit is made of an aluminum alloy material.

[0015] In some examples of the present invention, the locator is a hydrophone.

[0016] In some examples of the present invention, there are multiple hydrophones, and the multiple locators are arranged at intervals in the circumferential direction of the underwater acoustic Luneburg invisibility lens.

[0017] In some examples of the present invention, the hydrophone includes a main body member and a connecting member. The connecting member includes a first connecting portion and a second connecting portion. One end of the first connecting portion is connected to the focal point at the edge of the underwater acoustic Luneburg invisibility lens and extends radially outside the underwater acoustic Luneburg invisibility lens. One end of the second connecting portion is connected to the other end of the first connecting portion, and the second connecting portion extends along the axial direction of the underwater acoustic Luneburg invisibility lens. The main body member is arranged at the other end of the second connecting portion.

[0018] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present invention. Description of the Drawings

[0019] The above and / or additional aspects and advantages of the present invention will become apparent and easy to understand from the description of the embodiments in conjunction with the following drawings, where:

[0020] Figure 1 is a schematic diagram of an underwater acoustic stealth positioning system according to an embodiment of the present invention;

[0021] Figure 2 is a schematic diagram of an underwater acoustic stealth positioning system according to an embodiment of the present invention;

[0022] Figure 3 is a schematic diagram of an underwater acoustic Luneburg invisibility lens according to an embodiment of the present invention;

[0023] Figure 4 is a schematic diagram of a locator according to an embodiment of the present invention;

[0024] Figure 5 is a schematic diagram of a unit cell according to an embodiment of the present invention;

[0025] Figure 6 is a partial schematic diagram of a unit cell according to an embodiment of the present invention;

[0026] Figure 7 is a sound pressure value distribution field diagram of 5 - 15 kHz frequency under the incidence of sound waves at 30°, 60°, and 90° according to an embodiment of the present invention;

[0027] Figure 8 is a background pressure field diagram of sound waves incident at 30°, 60°, and 90° at 10 kHz frequency according to an embodiment of the present invention;

[0028] Figure 9 is a structural diagram of a unit cell according to an embodiment of the present invention;

[0029] Figure 10 is a design diagram of an underwater Luneburg stealth lens according to an embodiment of the present invention;

[0030] Figure 11 is a schematic diagram of implanting a unit cell into an underwater Luneburg stealth lens according to an embodiment of the present invention;

[0031] Figure 12 is Figure 11 a schematic diagram of area A in

[0032] Figure 13 is Figure 11 a schematic diagram of area B in

[0033] Figure 14 is a reflection cross - sectional diagram of an underwater Luneburg stealth lens according to an embodiment of the present invention;

[0034] Figure 15 is a schematic diagram of an underwater Luneburg stealth lens transformed from a traditional underwater Luneburg lens into a toroid according to an embodiment of the present invention.

[0035] Reference numerals:

[0036] 100, underwater acoustic stealth positioning system;

[0037] 10, underwater Luneburg stealth lens; 11, stealth accommodation groove; 12, five - mode material layer; 121, unit cell; 1211, first inclined plate; 1212, second inclined plate; 1213, third inclined plate; 1214, first mass block; 1215, second mass block; 20, housing; 21, avoidance opening; 30, locator; 31, connecting member; 311, first connecting portion; 312, second connecting portion; 32, main body member. Detailed implementation manners

[0038] Embodiments of the present invention will be described in detail below. The embodiments described with reference to the accompanying drawings are exemplary. Embodiments of the present invention will be described in detail below.

[0039] Reference will be made below Figures 1 - 15 to describe an underwater acoustic stealth positioning system 100 according to an embodiment of the present invention.

[0040] In combination with Figures 1 - 11 as shown, an underwater acoustic stealth positioning system 100 according to the present invention may mainly include: an acoustic Luneburg stealth lens 10, a housing 20, and a locator 30. Among them, the housing 20, the acoustic Luneburg stealth lens 10, and the locator 30. The acoustic Luneburg stealth lens 10 is arranged in a ring shape inside the housing 20. An stealth accommodation groove 11 is provided in the middle of the acoustic Luneburg stealth lens 10. An object to be stealth is suitable to be placed in the stealth accommodation groove 11. A focus is provided at the edge of the acoustic Luneburg stealth lens 10. The locator 30 is arranged inside the housing 20. One end of the locator 30 is arranged at the focus at the edge of the acoustic Luneburg stealth lens 10, and the other end of the locator 30 is connected to the housing.

[0041] Specifically, by setting the acoustic Luneburg stealth lens 10 as a cylinder, and an stealth accommodation groove 11 is provided in the middle of the acoustic Luneburg stealth lens 10. An object to be stealth is arranged in the stealth accommodation groove 11. When the acoustic signal generated by the detector is transmitted to the acoustic Luneburg stealth lens 10, the acoustic wave can be focused at the focus at the edge of the acoustic Luneburg stealth lens 10, so as to avoid the acoustic wave being transmitted to the object in the stealth accommodation groove 11, thereby making the object in the stealth accommodation groove 11 stealth.

[0042] It should be noted that because the acoustic Luneburg stealth lens 10 can focus acoustic waves in any direction, that is, the acoustic Luneburg stealth lens 10 can focus acoustic waves transmitted from the circumferential 360° direction. While retaining the functions of acoustic wave focusing and plane wave conversion, complete stealth of the object in the stealth accommodation groove 11 inside the cylindrical acoustic Luneburg stealth lens 10 is achieved.

[0043] Furthermore, one end of the locator 30 is connected to the focus at the edge of the acoustic Luneburg stealth lens 10, and the other end of the locator 30 extends radially outward of the acoustic Luneburg stealth lens 10. The locator 30 can detect acoustic waves and can reverse-locate the position of the detector, so as to reverse-locate the position of the detector on the premise of achieving target hiding, so that an underwater acoustic stealth positioning system 100 can have both underwater stealth and positioning functions at the same time.

[0044] As Figure 15As shown, embodiments of the present invention can transform the traditional cylindrical Luneburg lens into an underwater acoustic Luneburg stealth lens 10 of a cylinder by transforming the acoustic theory, and can achieve acoustic stealth of the internal stealth accommodation groove 11 while retaining the positioning ability.

[0045] The underwater acoustic Luneburg stealth lens 10 is obtained by linearly mapping a cylindrical Luneburg lens, and maps a two-dimensional circle into a two-dimensional ring through a mapping function. To design a two-dimensional ring-shaped five-mode material Luneburg lens, as Figure 15 shown, considering the radial mapping relationship R = f(r) and Θ = θ from the circular region R ∈ [0, b] of the traditional underwater acoustic Luneburg lens to the annular region r ∈ [a, b] of the underwater acoustic Luneburg stealth lens in the polar coordinate system.

[0046] Among them,

[0047]

[0048] Under the above radial mapping relationship, the distribution of the material properties of the required underwater acoustic Luneburg stealth lens 10 can be obtained as:

[0049]

[0050] Among them, a = 0.05 m, b = 0.177 m, a and b are the inner diameter and outer diameter of the underwater acoustic Luneburg stealth lens 10 respectively; ρ n , K n are the density and modulus of the two-dimensional circular Luneburg lens before transformation; ρ0 = 1000 kg / m 3 , K0 = 2.25 GPa are the density and modulus of the background medium (i.e., water); ρ, K r , K θ are the density, radial modulus and tangential modulus of the underwater acoustic Luneburg stealth lens 10 respectively; is the refractive index of the two-dimensional circular Luneburg lens before transformation.

[0051] It should be noted that since f(a) = 0 will cause singularities in the material parameters at r = a of the underwater acoustic Luneburg stealth lens, a small parameter is selected such that f(a) = δ to avoid material parameter singularities.

[0052] In some embodiments of the present invention, the underwater acoustic Luneburg stealth lens 10 is made of a five-mode material. Specifically, the equivalent fluid characteristics of the underwater acoustic Luneburg stealth lens 10 made of a five-mode material achieve acoustic concealment of the internal sensors or energy modules in the stealth accommodation groove 11, and the concealment effect is better.

[0053] An underwater acoustic stealth positioning system 100 according to an embodiment of the present invention is applicable to the concealed deployment and collaborative operation of an underwater unmanned submersible (UUS). For example, in deep-sea exploration, the stealth accommodation groove 11 can accommodate a sensor array, and high-precision target tracking can be achieved through the reverse positioning function.

[0054] As shown in combination with Figure 3 The underwater acoustic Luneburg stealth lens 10 includes multiple layers of five-mode material layers 12. The five-mode material layers 12 are annular in shape, and the multiple layers of five-mode material layers 12 are concentrically arranged and stacked in the radial direction to form a cylindrical underwater acoustic Luneburg stealth lens 10. Specifically, by concentrically arranging and stacking the multiple layers of five-mode material layers 12 in the radial direction, the stealth performance of the stealth accommodation groove 11 of the underwater acoustic Luneburg stealth lens 10 for the objects therein can be further improved.

[0055] As shown in combination with Figure 5 The five-mode material layer 12 has multiple unit cells 121. The unit cell 121 includes an inclined plate and a mass block. The inclined plate includes a first inclined plate 1211, a second inclined plate 1212, and a third inclined plate 1213. The first inclined plate 1211 extends in the radial direction. The second inclined plate 1212 and the third inclined plate 1213 are both connected to the outer end of the first inclined plate 1211 in the radial direction and form an angle φ with the first inclined plate 1211. The angle formed between the second inclined plate 1212 and the third inclined plate 1213 is φ. The mass block includes a first mass block 1214 and a second mass block 1215. The first mass block 1214 is arranged on the first inclined plate 1211, and the second mass block 1215 is arranged on the second inclined plate 1212.

[0056] In each five-mode material layer 12, the multiple unit cells 121 are arranged in the circumferential direction, and the second inclined plate 1212 of one of the adjacent two unit cells 121 is connected to the third inclined plate 1213 of the other. Assume that the two layers adjacent in the radial direction in the multiple layers of five-mode material layers 12 are the first five-mode material layer and the second five-mode material layer respectively. The first five-mode material layer is located radially outside the second five-mode material layer. The inner ends of the first inclined plates 1211 of the first five-mode material layer are respectively connected to the outer ends of the second inclined plates 1212 and the outer ends of the third inclined plates 1213 of two adjacent unit cells 121 in the second five-mode material layer. In the direction extending from the radial outside to the inside of the underwater acoustic Luneburg stealth lens 10, the mass blocks in the multiple layers of five-mode material layers 12 gradually shrink, so that the underwater acoustic Luneburg stealth lens 10 can be constructed into a lens structure with a graded layer.

[0057] As shown in Figure 5 and Figure 14 The underwater acoustic Luneburg stealth lens 10 is a five-mode metamaterial acoustic lens. The unit cell 121 is hexagonal, the edge part is air, and the central part is aluminum alloy (density ρ Al = 2700 kg / m 3, a sloping plate and a mass block with Young's modulus E = 70 GPa and Poisson's ratio μ = 0.33). For a single unit cell 121, the wall thickness of the sloping plate is t, the length of the second or third sloping plate is l, the length of the first sloping plate is m, the length and width of the mass block are w and h respectively, the angle between the second sloping plate and the extension line of the first sloping plate is β, and the angle between the third sloping plate and the extension line of the first sloping plate is β.

[0058] To facilitate the construction of the hierarchical and gradually varying underwater Luneburg stealth lens 10, the unit cell 121 is adjusted by five dimensionless parameters: β, By adjusting these parameters, the anisotropy of the underwater Luneburg stealth lens 10 is ensured, and a refractive index with a gradient distribution is obtained to meet the requirements of the underwater Luneburg stealth lens 10 for the refractive index of the material.

[0059] As Figure 6 , Figure 10 , Figure 11 , Figure 12 and Figure 13 shown, it is the design diagram of the underwater Luneburg stealth lens 10 according to the embodiment of the present invention. Figure 10 Shows the continuous profile of the material properties determined by formula (2) and its layered approximation; Figure 6 The drawn is a partial schematic diagram of half of a circumferential period, which shows the way of transforming the frame of the local rectangular unit cell 121 into a local sector-shaped cylinder. According to parameters, the microstructure of each layer is established and the underwater Luneburg stealth lens 10 can be obtained in a circular array; Figure 11 Is a quarter layout of the designed underwater Luneburg stealth lens 10.

[0060] Specifically, as shown in Table 1, the detailed microstructure parameters of each layer are listed.

[0061] Table 1:

[0062]

[0063] Among them, the sector angle: The area between the dashed line and the solid line represents the structure of the five-mode material layer 12 in one radial layer. Each layer can be further divided into two small layers. Assume that the radial starting position of the i-th layer is: R i-1 , the geometric parameters of the unit cell 121 are: β i , m i , then there are the following geometric relationships: From the above relational expressions, the length of the sloping plate in the five-mode material layer 12 in the first small layer can be obtained:

[0064] Similarly, the initial radial position and the length of the sloping plate in the five-mode material layer 12 in the second small layer can be obtained:

[0065]

[0066] After obtaining the length of the inclined plate, according to the other three geometric parameters the specific dimensions of the five-mode material layer 12 of this layer can be determined. The end position of the unit cell 121 of this layer is the starting radial position R of the next layer i = α i 2 R i-1 . By iterating in this way, the specific microstructure within a circumferential period can be designed. By replicating multiple periods along the circumferential direction, the underwater acoustic Luneburg invisibility lens 10 can be obtained.

[0067] Figure 8 is the evaluation of the positioning performance of this system. Among them, Figure 8 (a), (b), and (c) are the background pressure fields of sound waves incident at 30°, 60°, and 90° at a frequency of 10 kHz respectively. After passing through the underwater acoustic Luneburg invisibility lens 10, they are all perfectly focused on the foci in the corresponding directions on the other side of the underwater acoustic Luneburg invisibility lens 10; Figure 7 (d), (e), and (f) are the distribution field diagrams of the sound pressure values at frequencies of 5 - 15 kHz when the sound waves are incident at 30°, 60°, and 90° respectively. The abscissa is the incident angle, and the ordinate is the incident frequency of the plane wave. It can be seen that the corresponding sound pressure values at their respective angular positions are the highest at different frequencies. From this, it can be concluded that an underwater acoustic stealth positioning system has good positioning performance and has broadband effectiveness while being able to perform good positioning and recognition in all directions.

[0068] As Figure 14 shown, it is the reflection cross-section diagram, which is the evaluation of the stealth performance of this system. Since most of the sonar detectors currently in use are of the self-transmitting and self-receiving type, considering the actual requirements, only minimizing the echo energy, that is, the reflected sound energy, can avoid the detection of self-transmitting and self-receiving type underwater sonar signals and obtain a good stealth effect. Therefore, the reflection cross-section σ is defined to quantitatively describe the reflected sound

[0069] energy Er. The smaller the reflection cross-section, the less likely it is to be detected during detection at the incident end, and the better the stealth effect.

[0070] Figure 14 The square marking line in

[0071] The square marking line and the triangular marking line have the same height, indicating that the cylindrical underwater Luneburg stealth lens 10 in the embodiment of the present invention obtained through mapping can achieve stealth inside the hollow cylindrical interior; combined with the circular marking line comparison, it can be concluded that directly digging a cylinder in the center of the traditional Luneburg lens cannot achieve the effect of stealth for objects inside the cylinder.

[0072] The diamond marking line is approximately the same height as the square marking line and the triangular marking line, and is significantly lower than the pentagonal marking line. From this, it can be concluded that the underwater Luneburg stealth lens 10 of the present invention has good stealth performance and can better protect the objects inside the ring from being detected. Among them, the two positions where the diamond marking line is significantly higher may be due to the resonance formed inside the underwater Luneburg stealth lens 10.

[0073] Combined Figure 1 、 Figure 2 and Figure 4 As shown, the locator 30 is a hydrophone, and the hydrophone can be used to receive the detected acoustic wave signals focused by the underwater Luneburg stealth lens 10 from the outside, so as to achieve reverse positioning.

[0074] Combined Figure 1 As shown, there are multiple hydrophones, and the multiple locators 30 are arranged at intervals in the circumferential direction of the underwater Luneburg stealth lens 10. In this way, the hydrophones can receive the acoustic waves at the focal points in the circumferential direction of the underwater Luneburg stealth lens 10 more comprehensively, thereby improving the stability and reliability of the reverse positioning of the hydrophones.

[0075] Combined Figure 4 As shown, the hydrophone includes a main body member 32 and a connecting member 31. The connecting member 31 includes a first connecting portion 311 and a second connecting portion 312. One end of the first connecting portion 311 is connected to the focal point at the edge of the underwater Luneburg stealth lens 10 and extends radially outward of the underwater Luneburg stealth lens 10. One end of the second connecting portion 312 is connected to the other end of the first connecting portion 311, and the second connecting portion 312 extends along the axial direction of the underwater Luneburg stealth lens 10. The main body member 32 is arranged at the other end of the second connecting portion 312.

[0076] Specifically, one end of the connecting member 31 is connected to the focal point at the edge of the underwater Luneburg stealth lens 10, and the other end of the connecting member 31 is connected to the main body member 32. The connecting member 31 can transmit the acoustic waves at the focal point at the edge of the underwater Luneburg stealth lens 10 to the main body member 32. The main body member 32 can reverse-locate the position of the detector according to the acoustic waves at the focal point at the edge of the underwater Luneburg stealth lens 10. In this way, not only can the reverse positioning of the hydrophone be made simpler, but also the structural design of the hydrophone can be simplified.

[0077] Furthermore, by connecting one end of the first connecting portion 311 to the focal point at the edge of the underwater Luneburg stealth lens 10 and extending it in the radial direction of the underwater Luneburg stealth lens 10, and connecting the second connecting portion 312 to the other end of the first connecting portion 311 and extending it in the axial direction of the underwater Luneburg stealth lens 10, the size in the radial direction and the size in the axial direction of an underwater acoustic stealth positioning system 100 can be balanced. Thus, it can prevent the size of an underwater acoustic stealth positioning system 100 from being too large in a certain direction, and can optimize the structural design of an underwater acoustic stealth positioning system 100.

[0078] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. are based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention.

[0079] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples", or "some examples", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example.

[0080] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and purposes of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. An underwater acoustic stealth positioning system, characterized in that, Comprising: A housing; An underwater Luneburg stealth lens, the underwater Luneburg stealth lens is arranged in a ring shape within the housing, a stealth accommodation groove is provided in the middle of the underwater Luneburg stealth lens, an object to be hidden is placed in the stealth accommodation groove, a hydrophone is provided at the edge of the underwater Luneburg stealth lens, and the material property distribution of the underwater Luneburg stealth lens is: ρ n = ρ0n, Among them, the underwater Luneburg invisibility lens is obtained by transforming the ordinary underwater Luneburg lens acoustically. The density and modulus of the ordinary underwater Luneburg lens are set as ρ n and K n , is the refractive index of the underwater Luneburg lens before transformation, and a and b are the inner diameter and outer diameter of the underwater Luneburg invisibility lens respectively; ρ0 = 1000 kg / m 3 , K0 = 2.25 GPa are the density and modulus of the background medium; ρ, K r , K θ are the density, radial modulus and tangential modulus of the underwater Luneburg invisibility lens respectively, The radial mapping relationship from the circular region R ∈ [0, b] of the ordinary underwater Luneburg lens in the polar coordinate system to the annular region r ∈ [a, b] of the underwater Luneburg invisibility lens is R = f(r) and Θ = θ; and A locator, the locator is arranged in the housing, and the locator is located at the focal point of the edge of the underwater Luneburg stealth lens.

2. An underwater acoustic stealth positioning system according to claim 1, characterized in that, The underwater Luneburg stealth lens includes multiple layers of five-mode material layers, the five-mode material layers are circular rings, and the multiple layers of five-mode material layers are concentrically arranged and stacked in the radial direction to form the cylindrical underwater Luneburg stealth lens.

3. An underwater acoustic stealth positioning system according to claim 2, characterized in that, The five-mode material layer has multiple unit cells, the unit cell includes a sloping plate and a mass block, the sloping plate includes a first sloping plate, a second sloping plate and a third sloping plate, the first sloping plate extends in the radial direction, the second sloping plate and the third sloping plate are both connected to the outer end of the first sloping plate in the radial direction and form an angle φ with the first sloping plate, and the angle formed between the second sloping plate and the third sloping plate is φ, the mass block includes a first mass block and a second mass block, the first mass block is arranged on the first sloping plate, and the second mass block is arranged on the second sloping plate.

4. An underwater acoustic stealth positioning system according to claim 3, characterized in that, In each of the five-mode material layers, multiple unit cells are arranged in the circumferential direction, and the second sloping plate of one of the adjacent two unit cells is connected to the third sloping plate of the other.

5. An underwater acoustic stealth positioning system according to claim 3, characterized in that, Assume that two adjacent layers in the radial direction of the multiple layers of five-mode material layers are respectively a first five-mode material layer and a second five-mode material layer, the first five-mode material layer is located radially outside the second five-mode material layer, and the inner ends of the first sloping plates of the first five-mode material layer are respectively connected to the outer ends of the second sloping plates and the outer ends of the third sloping plates of two adjacent unit cells in the second five-mode material layer.

6. An underwater acoustic stealth positioning system according to claim 3, characterized in that, In the direction extending from the radial outside to the inside of the underwater Luneburg stealth lens, the mass blocks in the multiple layers of five-mode material layers gradually shrink.

7. An underwater acoustic stealth positioning system according to claim 3, characterized in that, The unit cell is made of aluminum alloy material.

8. An underwater acoustic stealth positioning system according to claim 1, characterized in that, There are multiple hydrophones, and the multiple locators are spaced apart in the circumferential direction of the underwater Luneburg stealth lens.

9. An underwater acoustic stealth positioning system according to claim 1, characterized in that, The hydrophone includes a main body part and a connecting part, the connecting part includes a first connecting part and a second connecting part, one end of the first connecting part is connected to the focal point of the edge of the underwater Luneburg stealth lens and extends towards the radial outside of the underwater Luneburg stealth lens, the other end of the second connecting part is connected to the other end of the first connecting part, the second connecting part extends along the axial direction of the underwater Luneburg stealth lens, and the main body part is arranged at the other end of the second connecting part.

Images