Large-curvature broadband radar infrared compatible stealth design method

Abstract

The invention provides a large-curvature broadband radar infrared compatible stealth design method, and belongs to the field of electromagnetic multi-spectrum stealth. The method comprises the following steps: S1, defining materials of different layers in the radar infrared compatible stealth structure; s2, defining structure parameters of different layers in the radar infrared compatible stealth structure; s3, parameter optimization of different layers in the radar infrared compatible stealth structure is carried out; s4, selecting a typical aircraft large-curvature curved surface as an engineering application object; and S5, performing electromagnetic simulation on the large-curvature curved surface, and verifying the result of the design method. The method provided by the invention is not only suitable for radar infrared compatible stealth design of a flat plate piece, but also is used for large-curvature curved surface radar infrared compatible stealth design, the radar infrared compatible stealth design is pushed to engineering practicability, and a radar infrared compatible stealth structure can be designed in a real aircraft surface shape.

Description

Technical Field

[0001] The invention belongs to the field of electromagnetic multi-spectrum stealth, and specifically relates to a large-curvature wide-band radar infrared compatible stealth design method. Background Art

[0002] Radar detection plays an important role in reconnaissance, surveillance and detection / locking / attack in the fields of aircraft, ships and satellites. According to current statistical analysis, radar threats to aircraft account for more than 60%, including airborne fire control radar, airborne early warning reconnaissance radar, ground-to-air guided fire control radar and ground-to-air warning or surveillance radar. With the development of radar detection technology, such as the application of digital active phased array technology in radar, the angle and distance accuracy of radar have been greatly improved, bringing more challenges to current and future aircraft. In the next generation of fighters developed by major military powers in the world, radar detection threats are given priority. Radar detection threats include detection threats in different frequency bands such as C, S, and X bands, under different polarizations such as VV and HH polarization, and detection threats in different threat sectors. Therefore, the radar stealth of aircraft needs to consider coping with multi-spectrum and multi-polarization. Detection threats in the diagonal domain.

[0003] Infrared detection systems and infrared-guided air-to-air missiles are the biggest threats facing aircraft. According to Planck's law, all objects with a temperature greater than absolute zero (0K, -273℃) will continuously emit infrared radiation. Infrared detection technology is more concealed than radar detection, and has developed rapidly in terms of strike accuracy and anti-interference capabilities. Unlike radar detection, which relies on radar waves reflected by the target for positioning and tracking, infrared detection is based on the spontaneous infrared thermal radiation of the object. It is a passive detection method, while infrared stealth is a technical means of reducing the detection probability by reducing the infrared radiation characteristics of the target. Low-emissivity materials and selected radiators are often used to achieve infrared stealth. Therefore, in the face of the increasingly serious threat of infrared-guided missiles and infrared detection systems, in order to improve the survivability and combat effectiveness of aircraft and avoid being discovered by the opponent first in beyond-visual-range air combat, countries around the world are working hard to research and develop infrared stealth technology.

[0004] For aircraft, radar and infrared stealth capabilities are indispensable. However, the principles of various detection technologies are different. Radar detection and laser detection are active detection, relying on target echo signals to achieve detection, positioning and tracking; while infrared detection is passive detection, and the detection signal comes from the heat signal emitted by the target itself and the infrared signal reflected by the environment; therefore, the realization of multi-spectrum compatible stealth puts forward higher requirements for its basic theory and simulation design. For example, the low reflectivity required by microwave stealth and the low emissivity (high reflectivity) required by infrared stealth are theoretically contradictory. For actual engineering applications, the surface curvature of the aircraft varies greatly, and the principles of achieving radar stealth at different curvatures are different. For example, the main radar scattering mechanism of the aircraft fuselage surface comes from traveling wave scattering, while the radar scattering at the leading edge with large curvature mainly comes from mirror reflection. In addition, the surface with large curvature is not suitable for radar infrared compatible simulation of simple flat parts. Usually, the surface has large curvature and large area, and it is necessary to directly perform radar infrared compatible simulation of large curved surfaces. Summary of the invention

[0005] The present invention aims to provide a large curvature wide band radar infrared compatible stealth design method, which is a radar infrared compatible stealth design based on the electromagnetic stealth principle of aircraft. In electromagnetic design, the electromagnetic wave radar absorption principle and infrared low emission principle are fully utilized, and the surface is kept in a low emissivity state by reasonably designing the duty cycle of the surface infrared low emissivity layer to achieve infrared stealth, and the thickness, unit size, and periodic form of the radar absorbing layer are optimized to achieve radar band stealth while coupling with the infrared low emissivity layer. In engineering application design, according to the radar stealth principle of the designed radar infrared stealth compatible structure, different curvatures such as the leading and trailing edges of the wing or the fuselage surface are reasonably used as application objects, and the absorbing material layer is arranged at the bottom layer, the infrared low emissivity layer is arranged at the top layer, and the wave-transmitting bearing layer is applied in the middle, and the electromagnetic simulation software is used for radar analysis, and the infrared stealth calculation is performed using the basic infrared principle. Using the above method, design cases show that this method can achieve large curvature radar infrared compatible stealth in a specific band, simulate the actual structure of the aircraft, and promote the engineering application of radar stealth compatibility. At the same time, this method also has the advantages of not relying on the performance of radar absorbing coatings and the thin thickness of the entire compatible stealth structure.

[0006] The technical solution of the present invention:

[0007] A method for designing a large curvature wide-band radar infrared compatible stealth, comprising the following steps:

[0008] S1: Define the materials of different layers in the radar infrared compatible stealth structure;

[0009] S2: Define the structural parameters of different layers in the radar infrared compatible stealth structure;

[0010] S3: Optimize the parameters of different layers in the radar infrared compatible stealth structure;

[0011] S4: Select typical large curvature surfaces of aircraft as engineering application objects;

[0012] S5: Perform electromagnetic simulation on large curvature surfaces to verify the results of the design method.

[0013] Furthermore, in step S1, define the materials of different layers in the radar infrared compatible stealth structure: select absorbing materials with certain losses (absorbing coatings, honeycombs, rubber plates, adhesive films, etc.), low emissivity materials (such as gold, silver, ITO and other highly conductive materials), and wave-transmitting materials (such as polyimide films, polyester resin films, polyester films, etc.), and input the characteristic parameters of the above materials into the electromagnetic software.

[0014] Furthermore, step S2 includes the following sub-steps: using the above-mentioned absorbing material, low emissivity material and wave-transmitting material to design a unit structure

[0015] The bottom layer as the first layer is a metal bottom layer with a thickness greater than 0.017 mm, simulating the surface of the components in actual application;

[0016] The second layer is an absorbing material layer. The unit structure on the second layer is a regular polygon with a side length of n≥4. The side length of the regular polygon is 1≤P0≤20, and the thickness is 1≤T0≤5. The function of the second layer is to couple with the third and fourth layers to jointly absorb radar waves.

[0017] The third layer is a wave-transmitting bearing layer. The shape and side length of the unit structure of this layer are the same as those of the second layer, and the thickness is 0.01≤T1≤0.1. The function of this layer is to bear the top layer and connect with the second layer.

[0018] The top layer is an infrared low emissivity layer. The unit structure of this layer is a regular polygon with a side length of n ≥ 4, a side length of K*P0 (0.5 < K < 1), and a thickness of 0.017 ≤ T2 ≤ 0.05. The function of this layer is to achieve infrared stealth as a low emissivity layer, and at the same time couple with the second and third layers to achieve radar absorption.

[0019] Furthermore, in step S3, the sub-steps are included: assigning different material properties to each layer of material respectively, optimizing the optimal size of each layer by using an optimization algorithm such as a differential evolution algorithm, and obtaining an optimized radar infrared stealth compatible structure; specifically, initializing the target parameters of each layer, calculating and evaluating the fitness values ​​of different parameters in each layer, then selecting different parameters of each layer as basis vectors, performing differential mutation recombination, and then performing mutation and crossover operations on the test individuals of each layer, performing fitness evaluation, and obtaining a new generation of populations. By comparing with the termination conditions initially set, if the conditions are met, the optimization can be terminated, and if not, it can be iterated again.

[0020] Furthermore, step S4 includes the following sub-steps: selecting a typical aircraft wing leading edge or fuselage surface curved surface as an application object according to the optimized radar infrared stealth compatible structure mechanism, coupling the optimized radar infrared stealth compatible structure with the curved surface application object, and structurally ensuring that the radar infrared stealth compatible structure is tightly connected with the curved surface.

[0021] Furthermore, step S5 includes sub-steps: performing tight meshing, electromagnetic simulation and infrared calculation on the surface application object described in step S4 and the optimized radar infrared stealth compatible structure, respectively obtaining radar scattering characteristics and infrared characteristics of the surfaces at different azimuths, elevations and polarizations after the optimized radar infrared stealth compatible structure is applied to the surface, and comparing them with the radar scattering characteristics and infrared of the surface to which only the coating is applied and without the radar infrared compatible stealth structure.

[0022] Beneficial effects of the present invention:

[0023] The beneficial effects of a large curvature wide-band radar infrared compatible stealth design method provided by the present invention include the following advantages: 1) The method provided by the present invention is not only applicable to the radar infrared compatible stealth design of flat panels, but also to the radar infrared compatible stealth design of curved surfaces with large curvature. The method pushes the radar infrared compatible stealth design to engineering practicality, which is conducive to designing a radar infrared compatible stealth structure in a real aircraft surface shape; 2) The method provided by the present invention does not rely on the performance of the absorbing coating, has a wider range of material selection, more design options, and is more economical; 3) The method provided by the present invention has wide practicality, and the material selection of the second layer, the third layer, and the top layer of the designed radar infrared compatible stealth structure is wide, and the material selection can be carried out according to other requirements of the aircraft, including the top layer can be selected from gold, silver, palladium, ITO or other metal materials, the third layer can be selected from polyimide, polyurethane film, etc., and the second layer can be selected from various absorbing rubbers, absorbing adhesive films, absorbing coatings, absorbing honeycombs, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some implementation cases of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0025] Figure 1 It is a multi-layer schematic diagram of a radar infrared compatible stealth structure in an embodiment of the present invention.

[0026] Figure 2 This is a RL diagram for optimizing the radar infrared compatible stealth structure in an embodiment of the present invention.

[0027] Figure 3 Schematic diagram of the airfoil leading edge surface selected in the embodiment of the present invention.

[0028] Figure 4 It is a schematic diagram of a radar infrared compatible stealth structure applied to a leading edge curved surface in an embodiment of the present invention.

[0029] Figure 5 This is a VV polarization RCS diagram at different pitch angles after the leading edge curved surface in an embodiment of the present invention applies a radar infrared compatible stealth structure.

[0030] Figure 6 This is the HH polarization RCS diagram at different pitch angles after the leading edge curved surface in an embodiment of the present invention applies a radar infrared compatible stealth structure.

[0031] Figure 7 This is a VV polarization RCS diagram at different elevation angles after the leading edge curved surface is applied with a radar stealth structure in an embodiment of the present invention.

[0032] Figure 8 This is the HH polarization RCS diagram at different elevation angles after the radar stealth structure is applied to the leading edge surface in an embodiment of the present invention.

[0033] Fig. 9 1 is a VV polarization RCS diagram of the leading edge curved surface at different pitch angles in an embodiment of the present invention.

[0034] Fig.10 1 is the HH polarization RCS diagram of the leading edge curved surface at different pitch angles in an embodiment of the present invention. DETAILED DESCRIPTION

[0035] All features disclosed in all embodiments in this specification, or steps in all methods or processes implicitly disclosed, except for mutually exclusive features and / or steps, can be combined and / or expanded or replaced in any way.

[0036] A large curvature wide-band radar infrared compatible stealth design method, comprising:

[0037] Step 1: The radar infrared compatible stealth structure in this case has four layers in total. The first layer is the metal bottom layer, the second layer is the wave absorbing material layer, the third layer is the wave transparent bearing layer, and the fourth layer is the infrared low emissivity layer. See attached Figure 1 Define the materials of different layers in the radar infrared compatible stealth structure. In this case, a certain type of absorbing honeycomb is selected as the second layer material, with a dielectric constant of 2.5-6 and a loss tangent of 0.5-0.95; a polyimide film is selected as the third layer material, with a dielectric constant of 2.8-3.5 and a loss of 0.001-0.008; Au is selected as the top layer material, with a conductivity ≥10 7 S / m. Input the typical electromagnetic parameters of the above materials into the electromagnetic software.

[0038] Step 2: Define the structural parameters of different layers in the radar infrared compatible stealth structure.

[0039] After defining the material parameters in step 1, you need to assign structural unit sizes to the materials of different layers. The bottom metal layer has a thickness greater than 0.017mm. In this case, the thickness of the metal layer is 0.2mm, and the side length is P0; the second layer of the unit structure is the absorbing material layer, which is usually a regular polygon (n≥4). In this case, the unit structure is a regular quadrilateral with a side length of P0 and a thickness of T0; the third layer is the wave-transmitting bearing layer. In this case, the wave-transmitting film is a polyimide film. The thickness of this layer is defined as T1 and the side length is P0; the top layer is the infrared low-emissivity layer. This layer is a regular polygon or a circle. In this case, it is defined as a regular quadrilateral with a side length of K*P0 (0.5<K<1) and a thickness of T (2≥0.017);

[0040] Step 3: Optimize the parameters of different layers in the radar infrared compatible stealth structure. After defining the material properties and structural unit parameters according to steps 1 and 2, in this case, the electromagnetic optimization algorithm is used for optimization in step 3. In this case, the optimization goal is: the average vertical reflectivity (RL) of the entire radar infrared stealth compatible structure in the applied band is lower than -8dB; the side length of the top infrared low emissivity layer is K>0.5, 1≤T0≤5, 0.01≤T1≤0.1, 0.017≤T2≤0.05, 1≤P0≤20. The optimized band in this case takes the X-band (8-12GHz), which is the typical fire control radar band with the greatest threat to aircraft, as the working band. After optimization by the electromagnetic optimization algorithm, the optimized unit size results in this case are: RL average value <-8dB, see attached Figure 2; K=0.8~0.95, the value in this case is 0.9; T0=1.5~3.5, the value in this case is 2, T1=0.01~0.1, the value in this case is 0.05; T2=0.017~0.05, the value in this case is 0.02; P=2.9~4.5, the value in this case is 4.

[0041] Step 4: Select a typical aircraft large curvature surface as the engineering application object. In this case, the leading edge of the NACA0012 airfoil is selected as the typical engineering application object. The leading edge length is 500mm, and the airfoil is 100mm from the leading edge vertex to the chord direction as the leading edge structure. See the attached Figure 3 The optimized radar stealth structure is tightly coupled with the leading edge surface, see attached Figure 4 .

[0042] Step 5: Perform electromagnetic simulation on the large curvature surface to verify the design method results.

[0043] The leading edge surface in step 4 and the radar infrared stealth compatible structure applied thereto are subjected to radar electromagnetic simulation and external low emissivity calculation. The radar simulation frequency is the typical X-band frequency of 9.4GHZ, the simulation angle range is forward 0-30°, down 5°, 0°, up 5°, the polarization mode is VV polarization and HH polarization, and the radar simulation schematic diagram is attached Figure 5 The surface infrared low emissivity calculation formula is:

[0044] τ surface = τ Au *K 2 +τMaterial*(1-K 2 )

[0045] where τ Au The surface emissivity of Au is 0.05, and the surface emissivity of τ material is 0.7 for the absorbing material.

[0046] Results Analysis

[0047] Analysis of infrared stealth results. The infrared surface emissivity of this case, designed by a large curvature wide-band radar infrared compatible stealth design method, is 0.17, which is significantly lower than the emissivity of the radar stealth structure that only uses absorbing materials, achieving a better infrared stealth effect.

[0048] Analysis of radar stealth results. This case compares the X-band, VV, HH polarization, 5, 0, 5 in the angular domain RCS of 0-30 for three structures, namely the leading edge surface using the radar infrared stealth compatible structure in this case, the leading edge surface using the absorbing material in this case, and the leading edge metal surface. The RCS results are attached Figure 5 , Figure 6 , Figure 7 , Figure 8 , Fig. 9, Fig.10 Through simulation comparison, it can be seen that the RCS reduction of the leading edge curved surface with the radar infrared stealth compatible structure is significantly better than that of the other two cases, and the reduction values ​​are shown in Table 1. Through the analysis of the experimental results, it can be seen that the large curvature wide-band radar infrared compatible stealth design method based on the present invention can well design a radar infrared stealth compatible structure applied to a large curved surface.

[0049] Table 1 RCS values ​​of leading edge surfaces with radar infrared compatible stealth structure, radar absorbing structure and no material applied

[0050]

[0051]

[0052] The present invention provides a wide-band radar infrared compatible stealth design method applicable to flat plate parts and large curved surface parts of aircraft. The design key points are that, in view of the urgent needs of aircraft for radar and infrared stealth, a radar infrared compatible stealth structure is designed according to the radar stealth principle and the infrared stealth principle. The structure is not only applicable to flat plate parts without curvature, but can also be further extended to be applicable to different curved surfaces of aircraft, so that the structural engineering of radar infrared stealth design is applied to aircraft, which can enable the aircraft to have stronger survivability when facing the threats of advanced radar detection, surface-to-air missiles, infrared guided missiles and infrared detection systems, thereby enhancing its own penetration capability. At present, a major problem in the engineering application of radar infrared stealth design is how to apply the radar infrared compatible stealth structure established based on flat plate simulation and experiment to the surface of aircraft with complex curvature changes. The key lies in that, first, it is necessary to design according to the radar scattering characteristics of different curvature parts of the aircraft surface. For example, when the first-order derivative of the curvature changes linearly, the radar scattering should be suppressed according to the mirror reflection mechanism first. When the first-order derivative of the curvature does not change significantly, the radar scattering should be suppressed according to the traveling wave scattering first; second, it is necessary to construct a low emissivity surface layer in the radar infrared compatible stealth structure according to the infrared stealth principle; third, considering the scouring of airflow, the erosion of other particles in the atmosphere, and the vibration suffered by itself during actual application, it is necessary to establish a strong connection relationship between different layers of the entire radar infrared compatible stealth structure. Therefore, the key to the design method of the present invention is that the radar infrared compatible stealth structure designed by the method can meet the requirements of being suitable for surfaces with complex curvature changes after fully considering the above key points, and the surface infrared emissivity is low. At the same time, there can be a wave-transmitting medium layer in the middle for strong connection. This method can better design a radar infrared compatible stealth structure with certain engineering application value.

[0053] The parts not involved in the present invention are the same as the prior art or can be implemented by using the prior art.

[0054] The above technical solution is only one implementation mode of the present invention. For those skilled in the art, it is easy to make various types of improvements or modifications based on the application methods and principles disclosed in the present invention, and is not limited to the methods described in the above specific implementation modes of the present invention. Therefore, the method described above is only preferred and has no restrictive meaning.

[0055] In addition to the above examples, those skilled in the art may obtain other embodiments based on the above disclosure or by utilizing knowledge or technical changes in related fields. The features of each embodiment may be interchangeable or replaced. The changes and modifications made by those skilled in the art do not depart from the spirit and scope of the invention and should be within the scope of protection of the claims attached to the invention.

Claims

1. A method for designing a large curvature wide-band radar infrared compatible stealth, characterized in that the steps include: S1: Define the materials of different layers in the radar infrared compatible stealth structure; S2: Define the structural parameters of different layers in the radar infrared compatible stealth structure; S3: Optimize the parameters of different layers in the radar infrared compatible stealth structure; S4: Select typical large curvature surfaces of aircraft as engineering application objects; S5: Perform electromagnetic simulation on large curvature surfaces to verify the results of the design method.

2. The method for designing a large curvature wide-band radar infrared compatible stealth device according to claim 1, characterized in that: In step S1, the materials of different layers in the radar infrared compatible stealth structure are defined: absorbing materials with certain losses, low emissivity materials, and wave-transmitting materials are selected, and the characteristic parameters of the above materials are input into the electromagnetic software.

3. The method for designing a large curvature wide-band radar infrared compatible stealth device according to claim 2, characterized in that: The absorbing material is an absorbing coating, a honeycomb, a rubber plate or a film; the low-emissivity material is gold, silver or ITO; and the wave-transmitting material is a polyimide film, a polyester resin film or a polyester film.

4. The method for designing a large curvature wide-band radar infrared compatible stealth device according to claim 1, characterized in that: Step S2 includes the following sub-steps: using the above-mentioned absorbing material, low emissivity material and wave-transmitting material to design a unit structure The bottom layer as the first layer is a metal bottom layer with a thickness greater than 0.017 mm, simulating the surface of the component in actual application; The second layer is an absorbing material layer. The unit structure on the second layer is a regular polygon with a side length of n≥4. The side length of the regular polygon is 1≤P0≤20, and the thickness is 1≤T0≤5. The function of the second layer is to couple with the third and fourth layers to jointly absorb radar waves. The third layer is a wave-transmitting bearing layer. The shape and side length of the unit structure of this layer are the same as those of the second layer, and the thickness is 0.01≤T1≤0.

1. The function of this layer is to bear the top layer and connect with the second layer. The top layer is an infrared low emissivity layer. The unit structure of this layer is a regular polygon with a side length of n≥4, a side length of K*P0, 0.5<K<1, and a thickness of 0.017≤T2≤0.

05. The function of this layer is to serve as a low emissivity layer to achieve infrared stealth, and at the same time couple with the second and third layers to achieve radar absorption.

5. The method for designing a large curvature wide-band radar infrared compatible stealth device according to claim 1, characterized in that: In step S3, the sub-steps are included: assigning different material properties to each layer of material respectively, optimizing the optimal size of each layer by using an optimization algorithm, and obtaining an optimized radar infrared stealth compatible structure; specifically, by initializing the target parameters of each layer, calculating and evaluating the fitness values ​​of different parameters in each layer, then selecting different parameters of each layer as basis vectors, performing differential mutation recombination, and then performing mutation and crossover operations on the test individuals of each layer, performing fitness evaluation, and obtaining a new generation of populations. By comparing with the termination conditions initially set, if the conditions are met, the optimization can be terminated, and if not, it will be iterated again.

6. The method for designing a large curvature wide-band radar infrared compatible stealth device according to claim 1, characterized in that: Step S4 includes the following sub-steps: selecting a typical aircraft wing leading edge or fuselage surface curved surface as an application object according to the optimized radar infrared stealth compatible structure mechanism, coupling the optimized radar infrared stealth compatible structure with the curved surface application object, and structurally ensuring that the radar infrared stealth compatible structure is tightly connected with the curved surface.

7. The method for designing a large curvature wide-band radar infrared compatible stealth device according to claim 1, characterized in that: Step S5 includes the following sub-steps: performing tight meshing, electromagnetic simulation and infrared calculation on the surface application object and the optimized radar infrared stealth compatible structure described in step S4, respectively obtaining radar scattering characteristics and infrared characteristics of the surface at different azimuth angles, elevation angles and polarization angles after the optimized radar infrared stealth compatible structure is applied to the surface, and comparing them with the radar scattering characteristics and infrared of the surface to which only the coating is applied and without the radar infrared compatible stealth structure.

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