Design method and aircraft for anti-shipborne fixed-wing early warning aircraft

Abstract

The present invention provides a design method for an anti-shipborne fixed-wing early warning aircraft and the aircraft, and relates to the technical field of radio frequency stealth resource management. The present invention can dynamically adjust the radar cross section (RCS) of the aircraft by deeply analyzing the relationship between sea clutter and aircraft shape parameters, so as to hide the Doppler frequency of radar signals in clutter, and significantly reduce the risk of being detected by enemy radars. In addition, the dynamic response capability of smart materials is utilized to adjust the physical properties of the aircraft surface in real time according to changes in environmental radiation, so as to optimize the control of RCS. By integrating a comprehensive adjustment model, these technologies do not act alone, but cooperate with each other to enhance the stealth capability of the aircraft in terms of radar scattering and infrared radiation. This multi-dimensional stealth strategy greatly enhances the survival potential of the aircraft in the face of multiple threats, and ensures its operational safety in complex environments.

Description

Technical Field

[0001] The present invention relates to the technical field of radio frequency stealth resource management, and in particular to a design method and an anti-shipborne fixed-wing early warning aircraft aircraft. Background Art

[0002] Carrier-based early warning aircraft, based on aircraft carriers or other ships, are mainly used for air defense early warning of ship formations, and can command and guide the combat of their own aircraft. In the confrontation between aircraft carrier battle groups of major powers, if the enemy's carrier-based early warning aircraft can be shot down, the initiative of the war will be in hand; the side that loses the protection of carrier-based early warning aircraft will have its aircraft carrier fleet become a live target of the other side; therefore, the demand for anti-carrier-based early warning aircraft is extremely urgent, and an anti-carrier-based fixed-wing early warning aircraft aircraft that can counter the technical characteristics of carrier-based early warning aircraft to weaken or even eliminate its role is urgently needed;

[0003] Although AWACS have many advantages, they also have disadvantages such as slow speed, poor maneuverability, and strong radar scattering. Affected by sea clutter, it is difficult for general AWACS radars to detect "low, slow, and small" targets through Doppler filtering measures. For example, the radar visual range of the Hawkeye AWACS at cruising altitude for large ships (RCS of the order of 10,000 m2) is about 405 km, but due to the slow movement of ships and the influence of sea clutter, the detection distance of the radar for large ships is only 360 km. At present, there are cruise missiles such as AGM-129A / B and YJ-18 that use land / sea clutter to achieve stealth, and aircraft such as high-altitude balloons and stratospheric airships that use land / sea clutter to achieve stealth. The stealth effect of aircraft under the background of sea clutter is affected by many factors, including radar type, operating frequency, beam width, pulse width, sea state level, wind speed direction, etc.

[0004] In the prior art, publication number CN110927692A discloses a method for solving the radio frequency stealth working mode of search radar in sea clutter scenarios. When radiating energy, the radio frequency stealth radar must not only meet the needs of detecting targets, but also be able to avoid being intercepted by passive receivers. In the process of performing search tasks, it is necessary to seek the best search method to counter passive receivers. In sea clutter scenarios, high-intensity surface clutter will cause an increase in the probability of false alarms. The present invention considers the impact of sea clutter on the receiver's decision in the radiation model, limits the echo intensity, and corrects the false alarm problem that other algorithms may face in sea clutter, so that the algorithm results are in line with reality;

[0005] Existing deficiencies: Although existing technologies such as CN110927692A have proposed methods for radar radio frequency stealth in sea clutter environments, these methods have not fully addressed the need to achieve aircraft stealth in complex sea conditions. How to deeply analyze the sea clutter spectrum and aircraft shape parameters, dynamically adjust the RCS, hide the Doppler frequency in the clutter, and use the dynamic response characteristics of smart materials to adjust surface properties according to environmental radiation, optimize dynamic RCS, and comprehensively adjust the model to collaboratively optimize radar scattering and infrared radiation, provide a multi-dimensional stealth strategy, and enhance the stealth of aircraft in complex environments are the directions that need to be improved at present;

[0006] The above information disclosed in this Background section is only for enhancement of understanding of the background of the present disclosure and therefore it may contain information that does not constitute the prior art that is already known to one of ordinary skill in the art. Summary of the invention

[0007] The purpose of the present invention is to provide a design method and an aircraft for anti-shipborne fixed-wing early warning aircraft to solve the problems raised in the above-mentioned background technology.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] The design method of the anti-shipborne fixed-wing early warning aircraft aircraft includes the following specific steps:

[0010] Step S1, radar stealth design, collecting sea clutter spectrum data and aircraft shape parameters to evaluate and optimize the aircraft's radar cross section RCS;

[0011] Step S2: Dynamic radar stealth technology, collecting RCS data under different radar frequency bands and response characteristics of smart materials, for dynamic adjustment of aircraft structure;

[0012] Step S3, obtaining the sea clutter spectrum data and the aircraft shape parameters in step S1, extracting the key spectrum features of the sea clutter, analyzing the relationship between the aircraft RCS and the sea clutter spectrum, and constructing a first evaluation model of the aircraft RCS and the sea clutter spectrum, which is used to evaluate and determine the optimal stealth design parameters of the aircraft shape to achieve radar stealth optimization;

[0013] Step S4, obtaining the RCS data in step S2 and the response characteristics of the smart material, analyzing the response of the smart material under different radar frequency bands, and constructing a second evaluation model of the temperature-deformation of the smart material, which is used to realize dynamic RCS control to optimize the dynamic stealth strategy;

[0014] Step S5: Obtain the first evaluation model and the second evaluation model, analyze and process them, and construct a comprehensive adjustment model. The model screens and fine-tunes the evaluation results of each evaluation model based on the control system.

[0015] Furthermore, the first evaluation model and the second evaluation model are obtained, analyzed and processed, and a comprehensive adjustment model is constructed. The model screens and fine-tunes the evaluation results of each evaluation model based on the control system, and specifically includes the following contents:

[0016] The comprehensive adjustment model is defined as CM(t), and the calculation formula is as follows:

[0017]

[0018] Where S(·) is the Sigmoid function, which is used to smooth and limit the range of CM(t) to (0,1) and is defined as

[0019] x represents k is a coefficient used to adjust the slope of the Sigmoid function. Increasing k will make the Sigmoid function steeper near x=0; Yz is a threshold parameter used to adjust the midpoint position of the Sigmoid function; d1 and d2 are weighting coefficients, which are allocated according to the importance of the two evaluation models in the overall evaluation; M max is the maximum value of the first evaluation model, which is used to normalize the output of the first evaluation model; 100 in the function is the upper limit value of the second evaluation model;

[0020] CM(t) is the comprehensive adjustment model score at time t;

[0021] M1 is the output of the first evaluation model; RCS dyn (t) is the output of the second evaluation model at time t; M max is the maximum value of the first evaluation model, used for normalization;

[0022] When CM(t) is closer to 1, it means that the comprehensive stealth performance of the aircraft at the current time point is better, that is, it shows good stealth characteristics under both static and dynamic conditions; when CM(t) is closer to 0, it means that the comprehensive stealth performance of the aircraft at the current time point is worse;

[0023] The value range (0,1) of CM(t) is divided into three main intervals, namely the low performance area (0,0.33), the medium performance area [0.33,0.67), and the high performance area [0.67,1);

[0024] Low performance area (0,0.33), the control system is in the low performance area for M1 and RCS dyn (t) Perform screening and fine-tuning, giving priority to the stealth defects with the greatest impact; if the static model M1 contribution is significantly low, automatically increase the attitude adjustment to restore at least 15% of the stealth performance; at the same time, according to M1 and RCS dyn(t) Contribution adjustment d1 and d2 to ensure fast response and effective stealth performance recovery;

[0025] Medium performance area [0.33, 0.67), in the medium performance area, the control system adopts a balanced strategy, according to M1 and RCS dyn (t) Fine-tune data weights to achieve maximum performance improvement; adjust flight parameters or material properties to reduce RCS dyn (t) Influence and improve the CM(t) value to ensure that the aircraft's stealth performance remains at an acceptable level while seeking opportunities to advance to the high performance zone;

[0026] High performance zone [0.67,1), the control system in the high performance zone is fine-tuned to maintain the excellent stealth performance of the aircraft in dynamic and static conditions, monitor small changes, adjust electronic countermeasures and flight parameters, and maintain high stealth performance with minimum RCS; optimization involves 65%-35% trade-off between M1 and RCS dyn (t) to actively respond to any signals that reduce stealth performance.

[0027] An anti-shipborne fixed-wing early warning aircraft aircraft, the aircraft is used to execute the design method of the anti-shipborne fixed-wing early warning aircraft aircraft, including: a distributed ducted electric propulsion long-range UAV, a heavy-loaded quadcopter flying aid that can be quickly assembled / disassembled, an anti-early warning aircraft missile adapted to an electric UAV, and UAV intelligent flight technology based on passive detection and system coordination.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] More sophisticated stealth performance adjustment: Through in-depth analysis of the sea clutter spectrum and aircraft shape parameters, the aircraft's RCS can be dynamically adjusted according to sea conditions so that its Doppler frequency is appropriately hidden in the clutter spectrum;

[0030] Dynamic response characteristics of smart materials: Analyze the response of smart materials in different radar frequency bands and optimize dynamic RCS control, so that the aircraft can adjust the surface material properties according to the reflection characteristics of environmental radiation when performing tasks;

[0031] Construction of a comprehensive adjustment model: The present invention not only optimizes the radar scattering and infrared radiation characteristics of the aircraft individually, but also realizes the coordinated optimization of these two characteristics through a comprehensive adjustment model, providing a multi-dimensional stealth strategy. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The present invention is a schematic diagram of the design method flow chart;

[0033] Figure 2 It is a schematic diagram of the top view structure of the present invention;

[0034] Figure 3 It is a side view structural schematic diagram of the present invention;

[0035] Figure 4 It is a rear view structural schematic diagram of the present invention;

[0036] Figure 5 It is a schematic diagram of the flight profile of the present invention. DETAILED DESCRIPTION

[0037] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

[0038] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0039] Embodiment 1:

[0040] See also Figure 1 , the present invention provides a technical solution:

[0041] The design method of the anti-shipborne fixed-wing early warning aircraft aircraft includes the following specific steps:

[0042] Step S1, radar stealth design, collecting sea clutter spectrum data and aircraft shape parameters to evaluate and optimize the aircraft's radar cross section RCS;

[0043] Step S2: Dynamic radar stealth technology, collecting RCS data under different radar frequency bands and response characteristics of smart materials, for dynamic adjustment of aircraft structure;

[0044] Step S3, obtaining the sea clutter spectrum data and the aircraft shape parameters in step S1, extracting the key spectrum features of the sea clutter, analyzing the relationship between the aircraft RCS and the sea clutter spectrum, and constructing a first evaluation model of the aircraft RCS and the sea clutter spectrum, which is used to evaluate and determine the optimal stealth design parameters of the aircraft shape to achieve radar stealth optimization;

[0045] Step S4, obtaining the RCS data in step S2 and the response characteristics of the smart material, analyzing the response of the smart material under different radar frequency bands, and constructing a second evaluation model of the temperature-deformation of the smart material, which is used to realize dynamic RCS control to optimize the dynamic stealth strategy;

[0046] Step S5: Obtain the first evaluation model and the second evaluation model, analyze and process them, and construct a comprehensive adjustment model. The model screens and fine-tunes the evaluation results of each evaluation model based on the control system.

[0047] Embodiment 2:

[0048] Further illustrating on the basis of the first embodiment, the sea clutter spectrum data includes radar wavelength, wind speed, radar operating frequency, radar pulse width, and the radar wavelength is marked as LDλ, the wind speed is marked as Fv, the radar operating frequency is marked as LDf, and the radar pulse width is marked as LDMk;

[0049] Radar wavelength LDλ means that radar waves of different wavelengths have different reflection characteristics on the sea surface; the calculation formula is as follows:

[0050]

[0051] Wherein, c is the speed of light, which in this embodiment is 3\times10^8 meters per second, and LDf is the radar operating frequency;

[0052] Wind speed Fv is a dynamic characteristic that affects the sea surface and thus the generation of sea clutter. Wind speed data is collected in real time through weather stations or anemometers;

[0053] Radar operating frequency LDf is different. Radars with different frequencies respond differently to sea clutter;

[0054] Radar pulse width LDMk affects the resolution and sensitivity of radar detection and is obtained from radar specification parameters;

[0055] The aircraft shape parameters include the length, width, height, surface roughness, electromagnetic parameters, and structural shape of the aircraft, and the length value is marked as Cd, the width value is marked as Kd, the height value is marked as Gd, the surface roughness is marked as BMc, and the electromagnetic parameter is marked as DCs;

[0056] Aircraft size (length, width, height) directly affects the aircraft's RCS;

[0057] RCS size =f(L Cd ,W Kd ,H Gd )

[0058] Where f is a function used to calculate the size-based radar cross section RCS, the specific form of which depends on the geometric model of the aircraft and radar scattering theory;

[0059] The roughness of the aircraft surface affects the reflection and scattering of radar waves. It is measured by surface analysis instruments and expressed as the average roughness Ra.

[0060] Aircraft material properties include electromagnetic parameters of materials, such as dielectric constant and magnetic permeability, which affect the absorption and reflection of radar waves;

[0061] σ=ε DCs ·μ DCs

[0062] Where σ is a function of the radar cross section, ε DCs is the dielectric constant, μ DCs is the magnetic permeability. These two parameters determine the absorption and reflection characteristics of the material to radar waves;

[0063] The aircraft structure shape includes the wing and fuselage shape, which affects the scattering mode of radar waves. The various structural shapes of the aircraft are annotated to form {G1, G2, ..., Gi, ..., n}, where Gi represents the structural shape formed by the combination of the i-th type of wing and fuselage shape, and the RCS corresponding to Gi is associated and annotated. Specifically, the following contents are included:

[0064] Define structural shape parameters: For each Gi, define a set of parameters to describe its airfoil and fuselage shape, including wingspan, wing area, fuselage length, fuselage diameter, and airfoil section shape;

[0065] Simulate and calculate RCS: Use electromagnetic simulation software such as FEKO and HFSS to simulate the electromagnetic scattering of each Gi and calculate its RCS value at a specific radar wavelength; these simulations are based on physical optics PO, geometric optics GO, physical diffraction theory PTD, or finite element method FEM;

[0066] Build a relational database: Create a database that contains a detailed description of each Gi and its corresponding RCS value; this database can be a simple table or a more complex relational database;

[0067] Mathematical expression: For each Gi, its RCS is expressed as a function RCS(Gi,LDλ,θ,φ), where LDλ is the radar wavelength, θ,φ are the radar observation angles; this function is an empirical formula or analytical expression based on simulation results;

[0068] Application: In subsequent analysis, when it is necessary to evaluate the stealth performance of a specific Gi, its RCS value is directly retrieved from the database or calculated using the RCS(Gi,LDλ,θ,φ) function;

[0069] Assuming there is a specific Gi, get its RCS through the following steps:

[0070] Determine the parameters of Gi, wingspan, wing area, fuselage length, fuselage diameter, and airfoil section shape;

[0071] Use database query or call RCS(Gi,LDλ,θ,φ) function;

[0072] Get the RCS value at a specific radar wavelength and observation angle.

[0073] Embodiment three:

[0074] Further explanation is given on the basis of the second embodiment, the sea clutter spectrum data and aircraft shape parameters in step S1 are obtained, and the key spectrum features of the sea clutter are extracted, the relationship between the aircraft RCS and the sea clutter spectrum is analyzed, and a first evaluation model of the aircraft RCS and the sea clutter spectrum is constructed. The model is used to evaluate and determine the optimal stealth design parameters of the aircraft shape to achieve radar stealth optimization; specifically, the following contents are included:

[0075] The first evaluation model is defined as M1, focusing on the relationship between the aircraft's radar cross section RCS and the sea clutter spectrum characteristics; the following function expression is used:

[0076]

[0077] Among them, LDλ is the radar wavelength calculation formula, LDf is the radar operating frequency; Fv is the wind speed, which is collected in real time by a weather station or anemometer; LDMk is the radar pulse width, which is directly obtained from the radar specification parameters;

[0078] RCS veh It is the calculation model of the aircraft RCS, which depends on the specific parameters of the aircraft and is expressed by the following formula:

[0079] RCS veh (Cd,Kd,Gd,BMc,DCs)=(Cd·Kd·Gd)·(1+η·BMc)·ζ(DCs)

[0080] Where η and ζ(DCs) are the influence coefficients of surface roughness and electromagnetic parameters on RCS, respectively;

[0081] A1, A2, A3, α, β, γ are coefficients determined empirically based on sea clutter characteristics and aircraft characteristics; the specific values ​​of these coefficients are obtained through data fitting and experimental measurement;

[0082] exp represents the natural exponential function, log represents the natural logarithmic function, and sin represents the sine function;

[0083] In practical applications, there is an upper limit M depending on the size and material properties of the aircraft. max , and then set the range of the model M1 to (0,M max ), assuming that M max is 100, and the specific value depends on the size of the aircraft and the radar characteristics; then the M1 value range is set to (0,100); the closer the M1 value is to 0, the better the stealth characteristic is, and the closer the M1 value is to 100, the worse the stealth characteristic is;

[0084] The value range of M1 (0,100) is divided into three intervals, each of which corresponds to a different level of stealth characteristics:

[0085] Excellent stealth characteristics, M1∈(0,36); medium stealth characteristics, M1∈[36,68); poor stealth characteristics, M1∈[68,100);

[0086] Excellent stealth performance range (0,36), within this range, the aircraft design reaches the high standard of stealth optimization, the RCS is significantly reduced, and the optimization rate exceeds 67%; the design focus includes fine-tuning the geometric dimensions, surface roughness and material electromagnetic properties to the optimal state; for any further design adjustments, it is necessary to strictly control their impact on the M1 value to ensure that the stealth characteristics are not significantly affected;

[0087] In this range, the RCS of the aircraft is optimized quite significantly. Specifically, the optimization effect is above 67%. A design with an M1 value of 15 shows that the detectable area of ​​the aircraft is reduced by more than 85% compared with the baseline model. This usually means that the aircraft shape parameters are adjusted to be close to the ideal stealth shape, and the interference between the sea clutter spectrum characteristics and the aircraft RCS is minimized. To achieve this level, the aircraft surface design needs to have low roughness and optimized electromagnetic characteristics.

[0088] In this range, if the calculated result of M1 is less than 10, the aircraft's shape design is considered to be close to the theoretical optimal solution, which is achieved by precisely adjusting Cd, Kd, ​​Gd and BMc, DCs to specific thresholds to optimize the RCS reflection characteristics; when the M1 value is between 10-36, the aircraft's shape design is still considered to have excellent stealth characteristics, but there is room for further optimization; when the increase in Cd corresponds to an increase in the M1 value of no more than 3%, it is considered that the negative impact on the stealth characteristics is still within an acceptable range;

[0089] In the excellent stealth range, a 1% increase in Cd corresponds to a 2% decrease in M1, while the change in Fv has a relatively weak effect on M1, with a 1% change affecting the value of M1 by only 0.5%. This shows that when optimizing the stealth characteristics of an aircraft, fine adjustment of geometric dimensions is more important than adapting to meteorological conditions. At the same time, if BMc increases by 10%, M1 increases by 6%, so it is necessary to pay attention to material selection and surface treatment technology during design.

[0090] Medium stealth characteristic interval [36,68), in this interval, the aircraft's RCS is reduced by 33% to 67%, showing stealth capability, but there is still room for improvement; design work includes shape and material optimization to further reduce RCS; the judgment criteria focus on ensuring that any design changes will not increase the M1 value to the upper limit of the interval, while improving stealth performance to near the excellent interval;

[0091] When the M1 value is between 36 and 68, the stealth characteristics of the aircraft are rated as medium, which means that the RCS is reduced by 33% to 67%. The detection range of the aircraft has been significantly reduced compared to the baseline model. In this range, the improvement of stealth characteristics mainly comes from the adjustment of shape parameters and the optimization of materials and surface treatment, and these adjustments fail to completely minimize the RCS.

[0092] In the medium stealth characteristic range, a threshold of 50 is set. If the M1 result is lower than 50 but higher than 36, it indicates that the shape design has stealth considerations, but there is still much room for improvement. The optimization of the electromagnetic parameter DCs of the material has not reached the ideal state. When the M1 result is between 50 and 68, it indicates that the selection of shape parameters or material properties needs to be re-evaluated to achieve better stealth effect.

[0093] In this range, a 1% increase in the length Cd of the aircraft will lead to a 1.5% increase in M1, indicating that geometric parameters still have a significant impact on the stealth effect; a small change in the radar wavelength LDλ, such as a 1% reduction, will lead to a decrease in M1 of nearly 0.3%, indicating that precise control of the operating frequency plays an important role in optimizing the stealth characteristics;

[0094] Poor stealth performance range [68,100), the aircraft design in this range has poor stealth performance, and the RCS reduction is less than 33%; the design focus is to identify and correct the key factors that lead to high RCS values, including shape parameters, electromagnetic properties of materials and surface roughness; design adjustments must focus on significantly improving the M1 value to move towards the medium stealth performance range;

[0095] When the value of M1 is between 68 and 100, the stealth characteristics of the aircraft are considered to be poor. In this range, the reduction of RCS is less than 33%, which indicates that the shape parameters, material selection or structural design of the aircraft design have failed to effectively reduce the reflection of radar waves. In this range, the aircraft is significantly redesigned to achieve better stealth effect.

[0096] The specific threshold of M1 is set to 80. In the range below 80 but above 68, although the aircraft is designed with stealth in mind, the effect is lower than expected, and specific design elements need to be adjusted. If the value of M1 exceeds 80, it means that the current design fails to significantly reduce RCS, and the shape and structure of the aircraft need to be redesigned from scratch.

[0097] In the range of poor stealth characteristics, if the aircraft width Kd increases by 1%, M1 will increase by 2%, and the width directly affects the lateral cross-sectional area of ​​the aircraft; the effect of changing the radar wavelength LDλ on M1 is more sensitive in this range, and a 1% reduction will lead to a 1% decrease in M1. Therefore, in the high RCS area, the choice of radar wavelength is particularly critical to improving stealth characteristics; at the same time, a 10% reduction in surface roughness BMc will cause M1 to decrease by 7%, indicating that considering surface smoothness in design is crucial to reducing RCS.

[0098] Embodiment 4:

[0099] Further illustrating on the basis of the first embodiment, the RCS data includes frequency band specific data, directional data, and dynamic change data;

[0100] Band-specific data represents RCS values ​​measured in multiple key radar bands, including but not limited to X-band, S-band, and Ku-band;

[0101] Assume that there are N key radar frequency bands, and the RCS value of each frequency band is represented as a vector: RCS freq =[RCS1,RCS2,...,RCS N ], where RCS i′ represents the radar cross section in the i′th frequency band;

[0102] Directivity data represents the RCS value of the aircraft at different angles and directions to comprehensively evaluate its stealth performance within a 360-degree range; assuming there are M different angles and directions, the RCS value in each direction is represented as a matrix:

[0103] Among them, RCS i′,j′ It represents the radar cross section in the j′th direction in the i′th frequency band;

[0104] Dynamically changing data represents the real-time RCS data when the aircraft is maneuvering or changing its attitude, so as to simulate the stealth effect in actual flight;

[0105] Dynamic RCS data is represented as the following time series function:

[0106] RCS dyn (t) = RCS freq (t) RCS dir (t)

[0107] Among them, RCS dyn (t) is the dynamic RCS value at time t, RCS freq (t) and RCS dir (t) are the frequency band-specific and directional RCS values ​​at time t, respectively;

[0108] The response characteristics of the smart material include conductivity change, temperature response, mechanical stress response, and electromagnetic response;

[0109] The conductivity change indicates the change in the conductivity of the smart material at different radar frequency bands, which directly affects the radar absorption capacity of the material;

[0110] The conductivity change is expressed as σ(fi′)=σ0+Δσ(fi′); where σ(fi′) is the conductivity at frequency fi′, σ0 is the base conductivity, and Δσ(fi′) is the conductivity change at frequency fi′;

[0111] Temperature response represents the deformation data of smart materials at different temperatures and how these deformations affect RCS;

[0112] The temperature response is expressed as the relationship between the deformation and temperature of the smart material, and the calculation formula is as follows:

[0113] ò(T)=ò0+a1·(T-T0)

[0114] Among them, ò(T) is the deformation at temperature T, ò0 is the deformation at reference temperature T0, and a1 is the linear expansion coefficient of the material;

[0115] Mechanical stress response represents the deformation characteristics of smart materials when subjected to mechanical stress, which is crucial for evaluating their applications in aircraft structures;

[0116] The mechanical stress response is expressed as Where, ò(σ′) is the deformation under stress σ′, and E1 is the elastic modulus of the material;

[0117] Electromagnetic response refers to the response of smart materials under the influence of electromagnetic fields, including their absorption and reflection characteristics of radar waves;

[0118] The electromagnetic response is expressed as the reflectivity and absorptivity of the material:

[0119]

[0120] A(fi′)=1-R(fi′)

[0121] Among them, R(fi′) is the reflectivity at frequency fi′, A(fi′) is the absorptivity at frequency fi′, Eref is the electric field strength of the reflected wave, and Einc is the electric field strength of the incident wave.

[0122] Embodiment five:

[0123] Further explanation based on the fourth embodiment, the RCS data and the response characteristics of the smart material in step S2 are obtained, the response of the smart material under different radar frequency bands is analyzed, and a second evaluation model of the temperature-deformation of the smart material is constructed. The model is used to realize dynamic RCS control to optimize the dynamic stealth strategy; specifically, the following contents are included:

[0124] The calculation formula of the second evaluation model is defined as follows:

[0125]

[0126] Among them, RCS dyn (t) is the dynamic RCS value at time t; RCS i′,j′ (t) is the radar cross section in the j′th direction at the i′th frequency band at time t; σ(fi′,T(t),σ′(t)) represents the conductivity change of the smart material under frequency fi′, temperature T(t) and stress σ′(t);

[0127] w i′j′ It represents the weight coefficient of the j′th direction in the i′th frequency band, which is used to adjust the impact of different frequency bands and directions on the total RCS;

[0128] The steps to obtain the formula are as follows:

[0129] Collect data: collect RCS data of aircraft in different radar bands fi′ and different directions j′ i′,j′ (t);

[0130] Collect the conductivity change data σ(fi′,T(t),σ′(t)) of the smart material at different frequencies fi′, temperatures T(t) and stresses σ′(t);

[0131] Construct the following conductivity change formula:

[0132]

[0133] Where σ0 is the basic conductivity, Δσ(fi′) is the conductivity change at frequency fi′; T(t) is the temperature at time t; T0 is the reference temperature; a1 is the linear expansion coefficient; σ′(t) is the stress at time t; E1 is the elastic modulus;

[0134] Construct a dynamic RCS formula, substitute the above conductivity change formula into the dynamic RCS formula, and obtain a complete evaluation model formula;

[0135] Determine the weight coefficient w i′j′ , based on experimental data or experience, determine the weight coefficient w of the impact of different frequency bands and directions on RCS i′j′ ;

[0136] The second evaluation model range is RCS dyn (t)∈[0,RCS max ], where RCS max It is an upper limit value set according to the maximum RCS value of the actual aircraft to ensure that the RCS value output by the model is within a reasonable range;

[0137] By dynamically adjusting the aircraft structure and intelligent material properties, RCS dyn (t) Maintaining a low value range to achieve an optimized dynamic stealth strategy;

[0138] Ensure that σ0, Δσ(fi′), a1, and E1 in the conductivity change formula are non-zero to avoid invalid or conflicting calculation results when the parameters are zero, and obtain the following adjusted second evaluation model formula:

[0139]

[0140] The value range of the second evaluation model formula is further limited to (0,100), and the adjusted formula is:

[0141]

[0142] When RCS dyn (t) The value is close to 0, which means that the stealth effect of the aircraft is good at that moment and it is difficult to be detected by radar;

[0143] When RCS dyn A (t) value close to 100 indicates that the stealth effect of the aircraft at that moment is poor and it is easy to be detected by radar.

[0144] Embodiment six:

[0145] Further explanation based on Example 5, the value range (0,100) of the second evaluation model is divided into several intervals, namely interval 1 (0,26), interval 2 [26,52), interval 3 [52,100);

[0146] Interval 1 (0,26), in this interval, RCS dyn (t) values ​​below 26 indicate that the aircraft has excellent stealth effect; intelligent materials and flight strategies work together efficiently to reduce the probability of being detected by radar by more than 70%; at this stage, the aircraft optimizes the stealth effect by precisely adjusting material properties and flight attitude;

[0147] When the result of the second evaluation model is between 0 and 26, the stealth effect of the aircraft is good. At this time, the output value of the model RCS dyn (t) is close to 0, indicating that the radar is difficult to detect the aircraft. The actual situation corresponding to this stage is that the aircraft is using an efficient stealth material or adopting an effective stealth strategy. In this interval, a threshold of 15 is set. When the calculation result of the model is less than 15, the stealth effect of the aircraft has reached an excellent level, its radar reflection area is small, the difficulty of radar detection increases, and the stealth performance reaches an ideal state.

[0148] For this threshold, when the model's calculation result is between 15 and 26, the stealth effect of the aircraft is good. Although its radar detection difficulty has increased compared to the excellent level, it can still be maintained at a relatively low level. Its radar reflection area is relatively small, and the radar detection difficulty is still high.

[0149] In the first interval, when RCS dyn When the value of (t) increases from 0 to 26, it means that the stealth effect of the aircraft changes from excellent to good. This is due to changes in the aircraft's attitude and flight state, or changes in parameters such as the conductivity, temperature response, mechanical stress response, and electromagnetic response of the smart material. This will increase the radar reflection area and the difficulty of radar detection. If the conductivity of the smart material increases by 10%, it will cause the RCS dyn (t) value increases by 2.6 units, thus changing the stealth effect of the aircraft from excellent to good;

[0150] Interval 2 [26,52), RCS dyn (t) When the value is between 26 and 52, the aircraft exhibits general stealth performance. In this range, although the stealth effect is reduced, it is still intended to maintain a low radar detection rate by adjusting the response of smart materials and optimizing flight dynamics; specifically, the radar detection rate is maintained within 20%;

[0151] When the result of the second evaluation model is between 26 and 52, the stealth effect of the aircraft is average, and the output value of the model RCS dyn(t) At the medium level, it means that the radar has a medium difficulty in detecting the aircraft. The actual situation corresponding to this stage is that the aircraft is using a general stealth material or adopting a general stealth strategy. In this interval, a threshold is set to 39. When the calculation result of the model is less than 39, the stealth effect of the aircraft has reached a medium level, its radar reflection area is large, and the radar detection difficulty is relatively high.

[0152] For this threshold, when the model's calculation result is between 39 and 52, the stealth effect of the aircraft is poor; although its radar detection difficulty has increased compared to the medium level, it can still be maintained at a relatively medium level, its radar reflection area is relatively large, and the radar detection difficulty is still high;

[0153] In the second interval, when RCS dyn When the value of (t) increases from 26 to 52, it means that the stealth effect of the aircraft changes from fair to poor. This is due to changes in the aircraft's attitude and flight state, or changes in the conductivity, temperature response, mechanical stress response, and electromagnetic response parameters of the smart material. This will increase the radar reflection area and the difficulty of radar detection. If the conductivity of the smart material increases by 10%, the RCS dyn (t) value increases by 2.6 units, thus changing the stealth effect of the aircraft from fair to poor;

[0154] Interval 3 [52,100), in this interval, RCS dyn (t) values ​​are as high as 52 to 100, indicating poor stealth performance. The aircraft needs to further optimize the properties of smart materials and adjust flight strategies to reduce radar detection areas and improve stealth performance to cope with high radar detection risks.

[0155] When the result of the second evaluation model is between 52 and 100, the stealth effect of the aircraft is poor. At this time, the output value of the model is RCS. dyn (t) is relatively high, indicating that the radar has a high difficulty in detecting the aircraft. The actual situation corresponding to this stage is that the aircraft is using a stealth material with poor effect or adopting a stealth strategy with poor effect. In this interval, a threshold is set to 76. When the calculation result of the model is less than 76, the stealth effect of the aircraft has reached a poor level, its radar reflection area is large, and the radar detection difficulty is relatively high.

[0156] For this threshold, when the model's calculation result is between 76 and 100, the stealth effect of the aircraft is very poor, its radar reflection area is large, and the difficulty of radar detection is relatively high;

[0157] In the third interval, when RCS dynWhen the value of (t) increases from 52 to 100, it means that the stealth effect of the aircraft changes from poor to very poor. This is due to changes in the aircraft's attitude and flight state, or changes in parameters such as the conductivity, temperature response, mechanical stress response, and electromagnetic response of the smart material. This will increase the radar reflection area and the difficulty of radar detection. If the conductivity of the smart material increases by 10%, the RCS dyn The (t) value increases by 4.8 units, causing the aircraft's stealth to change from poor to very poor.

[0158] Embodiment seven:

[0159] Further explanation is given on the basis of Example 6, the first evaluation model and the second evaluation model are obtained, and analyzed and processed to construct a comprehensive adjustment model, which screens and fine-tunes the evaluation results of each evaluation model based on the control system, and specifically includes the following contents:

[0160] The comprehensive adjustment model is defined as CM(t), and the calculation formula is as follows:

[0161]

[0162] Where S(·) is the Sigmoid function, which is used to smooth and limit the range of CM(t) to (0,1) and is defined as

[0163] x represents k is a coefficient used to adjust the slope of the Sigmoid function. Increasing k will make the Sigmoid function steeper near x=0; Yz is a threshold parameter used to adjust the midpoint position of the Sigmoid function; d1 and d2 are weighting coefficients, which are allocated according to the importance of the two evaluation models in the overall evaluation; M max is the maximum value of the first evaluation model, which is used to normalize the output of the first evaluation model; 100 in the function is the upper limit value of the second evaluation model;

[0164] CM(t) is the comprehensive adjustment model score at time t;

[0165] For d1 and d2 determine:

[0166] These two parameters are the first evaluation model M1 and the second evaluation model RCS in the model. dyn (t) weighting coefficient; the weight is determined based on the influence and importance of each model in the overall stealth performance evaluation;

[0167] In the scenario, if the main operating environment of the aircraft tends to be highly dynamic, such as frequent speed changes or turns, the importance of the second evaluation model will increase; assuming that in such a highly dynamic environment, the importance of the second evaluation model accounts for 60%, then d2 = 0.6, and accordingly, d1 is the importance of the static model, accounting for 40%, that is, d1 = 0.4;

[0168] For the determination of k:

[0169] The setting of k determines the sensitivity of the Sigmoid function, that is, the degree to which changes in the input affect the output; setting a higher k value will make the Sigmoid function steeper near x=0, which means that the model is more sensitive to small changes in the input;

[0170] In a standard operating environment, k = 10 is assumed; this value is based on the fact that the model needs to be sensitive enough to reflect significant output changes when the input changes, ensuring that the model can effectively distinguish small performance differences;

[0171] Determination of the control parameters of the Yz corresponding midpoint position:

[0172] Yz controls the center point of the Sigmoid function, that is, when x=Yz, S(x)≈0.5; this parameter is adjusted according to the expected median value of the model output;

[0173] In most operating situations, the median value of the expected comprehensive score is 0.5, and the corresponding input x is set at a medium level; therefore, according to the settings of d1 and d2, Yz is set to 1.0, which is the midpoint based on the weighted average;

[0174] M1 is the output of the first evaluation model; RCS dyn (t) is the output of the second evaluation model at time t; M max is the maximum value of the first evaluation model, used for normalization;

[0175] When CM(t) is closer to 1, it means that the comprehensive stealth performance of the aircraft at the current time point is better, that is, it shows good stealth characteristics under both static and dynamic conditions; when CM(t) is closer to 0, it means that the comprehensive stealth performance of the aircraft at the current time point is worse; by adjusting k and Yz, the sensitivity and threshold of the comprehensive evaluation model are controlled, so that fine-tuning can be performed as needed in actual applications; this design allows comprehensive consideration of the stealth performance of the aircraft under different conditions and time points, and real-time evaluation and adjustment, which has high applicability and flexibility;

[0176] The value range (0,1) of CM(t) is divided into three main intervals, namely the low performance area (0,0.33), the medium performance area [0.33,0.67), and the high performance area [0.67,1);

[0177] Low performance area (0,0.33), the control system is in the low performance area for M1 and RCS dyn (t) Perform screening and fine-tuning, giving priority to the stealth defects with the greatest impact; if the static model M1 contribution is significantly low, automatically increase the attitude adjustment to restore at least 15% of the stealth performance; at the same time, according to M1 and RCS dyn (t) Contribution adjustment d1 and d2 to ensure fast response and effective stealth performance recovery;

[0178] The quantitative description of the interval and the technical effects are as follows:

[0179] In the low performance range of CM(t), the control system will follow M1 and RCS dyn (t) Prioritize the evaluation results of the 75% and 25% proportions of CM(t) contribution; if the contribution of M1 is less than 25% and RCS dyn If the contribution of M1 (t) is higher than 75%, the control system will include flight attitude adjustment as the primary response measure; in actual operation, if the contribution of M1 causes CM(t) to drop below 0.10, it means that the static stealth performance of the aircraft has dropped by at least 30%. The system will automatically increase the priority of attitude adjustment to restore at least 15% of the static stealth performance;

[0180] When the CM(t) value is in the range of (0, 0.33), it indicates that the stealth performance of the aircraft is poor. The output at this time reflects that the radar cross-section reflectivity RCS of the aircraft under static and dynamic conditions is high, and it is easy to be detected by the radar system. In specific operation, if the CM(t) value of the aircraft is continuously lower than 0.15, the control system will automatically start the emergency stealth mode, increase the transmission frequency and intensity of the interference signal, in an attempt to reduce the probability of being detected.

[0181] In order to accurately control the response of the aircraft in different performance ranges, a specific threshold T is set in the low performance area. low =0.15; when CM(t) is greater than this threshold but still in the low performance range, the system will reduce the intensity of stealth measures and instead increase maneuverability and speed to evade existing tracking; in addition, the system will optimize flight parameters in the hope of raising CM(t) to the medium performance range in a short period of time;

[0182] In the low performance area, the adjustment of d1 and d2 is very critical. If d1 increases by 10%, that is, from 0.4 to 0.44, CM(t) will directly increase by 5%. This is because the static model M1 directly affects the bottom line value of CM(t). In addition, increasing k from 10 to 15 will make the Sigmoid function more sensitive, that is, small M1 and RCS. dyn Changes in (t) will lead to larger changes in CM(t);

[0183] Medium performance area [0.33, 0.67), in the medium performance area, the control system adopts a balanced strategy, according to M1 and RCS dyn (t) Fine-tune data weights to achieve maximum performance improvement; adjust flight parameters or material properties to reduce RCS dyn (t) Influence and improve the CM(t) value to ensure that the aircraft's stealth performance remains at an acceptable level while seeking opportunities to advance to the high performance zone;

[0184] The quantitative description of the interval and the technical effects are as follows:

[0185] When CM(t) is in the medium performance range, the control system will be based on M1 and RCS dyn (t) current value, the fine-tuning strategy is considered to be 50%-50% balanced; if RCS dyn (t)) indicates that the stealth performance is reduced to below 0.40 of CM(t) during high-speed maneuvers, and has dropped by at least 20%, the control system will adjust the flight parameters to reduce the speed and maneuverability by less than 5% to reduce the dynamic RCS impact by at least 10%; at the same time, if the adjustment of M1 can bring at least 5% improvement of CM(t) with a change of no more than 3%, the system will give priority to such fine-tuning;

[0186] When the CM(t) value is in the interval [0.33, 0.67), the stealth performance of the aircraft is acceptable. This interval is a balanced state, where the aircraft is neither too visible nor completely hidden. The main task of the control system in this interval is to maintain the current state, while fine-tuning M1 and RCS. dyn (t) attempts to further optimize performance and push the CM(t) value toward the high performance area;

[0187] In the medium performance area, set an intermediate threshold T mid = 0.5, used to evaluate whether the aircraft is tending towards high performance or returning to the low performance area; when CM(t) exceeds T mid When the system is in stealth mode, it will rely less on dynamic stealth strategies and make more use of static optimization measures to maintain or improve stealth effects, such as adjusting flight attitude and path to reduce radar cross section.

[0188] In this range, the adjustment of Yz from 1.0 to 0.8 will reduce the center point offset of CM(t), making the system more sensitive to static and dynamic models. If d2 is increased by 5%, that is, adjusted from 0.6 to 0.63, CM(t) will increase by 3%, and the contribution of the dynamic model to the overall score will increase. This weight adjustment is flexibly adjusted according to the actual flight environment.

[0189] High performance zone [0.67,1), the control system in the high performance zone is fine-tuned to maintain the excellent stealth performance of the aircraft in dynamic and static conditions, monitor small changes, adjust electronic countermeasures and flight parameters, and maintain high stealth performance with minimum RCS; optimization involves 35%-65% trade-off considerations, and M1 and RCS dyn (t) fine-tuning to proactively respond to any signals that reduce stealth performance;

[0190] The quantitative description of the interval and the technical effects are as follows:

[0191] In the high performance range of CM(t), the screening and fine-tuning of the control system will be very fine, with a high impact on M1 and RCS. dyn If the change of M1 causes the CM(t) value to drop by 3%, which is a slight decrease in static stealth performance, the control system will take measures to adjust the surface material properties to restore at least 2% of the CM(t) value. At the same time, if RCS dyn If the change in (t) exceeds 5%, the dynamic stealth characteristics will be weakened, and the system will adjust the electronic countermeasures to reduce the dynamic RCS contribution by at least 3% to bring the CM(t) value back above the threshold;

[0192] When the CM(t) value is in the interval [0.67,1), the aircraft exhibits excellent stealth performance; in this interval, the control system will focus on maintaining and slightly optimizing this state, ensuring that the low RCS value is maintained by fine-tuning the parameters of radar absorbing materials and electronic jamming equipment;

[0193] Set the high performance threshold T high =0.85, as a further optimization standard, when CM(t) exceeds this threshold, the system will enter an energy-saving mode to reduce unnecessary interference transmission and use environmental factors such as clouds to further protect the aircraft;

[0194] In this range, if k increases to 20, the sensitivity of CM(t) increases significantly, making M1 and RCS dyn A small change in (t) can also cause a significant change in CM(t). At the same time, if d1 increases by 5%, that is, from 0.4 to 0.42, CM(t) increases by 2%, which strengthens the impact of the static model on the overall score, thereby continuously optimizing the stealth effect.

[0195] Embodiment eight:

[0196] Based on the seventh embodiment, in order to verify the actual application effect, a detailed experimental design and test were carried out. First, the aircraft model suitable for the test was determined, and different flight environments were set to simulate the changing operating conditions. In the experiment, the first evaluation model M1 of the aircraft was used to evaluate its static stealth performance, and the second evaluation model RCS dyn (t) Evaluate its dynamic stealth performance; collect M1 and RCS data through a series of scheduled flight missions. dyn (t) real-time data;

[0197] Before the experiment started, M max Measurements were made to determine the maximum value of M1 as a normalized benchmark; at the same time, the initial values ​​of k and Yz were set to 10 and 1.0, respectively, and a preliminary Sigmoid function shape was set according to the invention content; according to the main operating environment of the aircraft, the initial values ​​of d1 and d2 were determined to be 0.4 and 0.6, respectively, to reflect the importance of the dynamic model in a highly dynamic operating environment;

[0198] When conducting experimental tests, the baseline value of CM(t) is first tested under standard operating conditions, and then multiple rounds of tests are performed under various simulated high-dynamic environments; in each round of testing, M1 and RCS are recorded. dyn (t) data and calculate CM(t); During the experiment, k and Yz were fine-tuned to evaluate their actual impact on the sensitivity and threshold of CM(t);

[0199] During the experiment, special attention was paid to the system response when the CM(t) value entered the low-performance zone, medium-performance zone, and high-performance zone. In the low-performance zone, the system was configured to automatically increase the frequency and amplitude of the aircraft attitude adjustment when CM(t) dropped below 0.15 to evaluate the recovery of at least 15% of the static stealth performance. In the medium-performance zone, the ability to reduce the impact of dynamic RCS by at least 10% was tested by adjusting the flight parameters. In the high-performance zone, the system was set to automatically adjust the attitude of the aircraft to a minimum of 10% when the CM(t) value dropped below 0.15. dyn Fine adjustment is performed when (t) changes to maintain the height of CM(t);

[0200] Based on the data collected in the experiment, the following data table was established to record the test results of CM(t) under different operating environments and show the performance optimization achieved by adjusting the k and Yz parameters. The experimental data table is as follows:

[0201] Table 1

[0202]

[0203]

[0204] Data Analysis:

[0205] For low performance area analysis:

[0206] In the low performance area, the initial value of CM(t) is 0.35, which is increased to 0.50 after fine-tuning, which shows that by adjusting the system parameters, especially in M1 and RCS dyn In the reconfiguration and priority adjustment of M1 contribution, CM(t) can be significantly improved; specifically, when M1 contribution is insufficient, the system significantly recovers static stealth performance by increasing the adjustment of the aircraft attitude; if M1 contribution causes CM(t) to drop below 0.10, the system will automatically increase the priority of attitude adjustment to recover at least 15% of static stealth performance;

[0207] Analysis of the mid-performance area:

[0208] In the medium performance area, CM(t) is improved from 0.50 to 0.55. This improvement is mainly achieved by dyn (t) achieves a more balanced weight distribution of 50%-50%. This strategy allows the system to achieve a more balanced weight distribution of 50%-50% between the aircraft and the aircraft. ... between the aircraft and the aircraft. dyn (t) shows that when the stealth performance is reduced to less than 0.40 of CM(t) during high-speed maneuvers, the system optimizes the performance by reducing the dynamic RCS effect by 10% and adjusting the flight parameters to reduce the speed and maneuverability by less than 5%. This fine-tuning strategy enables CM(t) to be effectively improved;

[0209] High Performance Zone Analysis:

[0210] In the high performance area, CM(t) increases from 0.85 to 0.87. This slight increase reflects that the system can still be further optimized through fine-tuning when it is close to the best performance. In this range, M1 and RCS dyn A small change in (t) was carefully weighed from 65% to 35%, indicating that even a small performance degradation would trigger the system’s response; if a change in M1 caused the CM(t) value to drop by 3%, the system would recover at least 2% of the CM(t) value by adjusting the surface material properties;

[0211] The core of the present invention is that it can screen and fine-tune the evaluation results of each evaluation model in real time and accurately based on the control system; this method allows the system to dynamically adjust weights and parameters according to actual flight conditions to optimize the stealth performance of the aircraft; effective performance recovery and optimization in the low-performance and medium-performance ranges, as well as the fine-tuning capability in the high-performance range, demonstrate the significant advantages of the present invention in improving the sensitivity and accuracy of stealth performance adjustment.

[0212] Embodiment nine:

[0213] See also Figures 2 to 5 , an anti-shipborne fixed-wing early warning aircraft aircraft, the aircraft is used to execute the design method of the anti-shipborne fixed-wing early warning aircraft aircraft, including: a distributed ducted electric propulsion long-range UAV, a heavy-loaded quadcopter flying aid that can be quickly assembled / disassembled, an anti-early warning aircraft missile adapted to an electric UAV, and a UAV intelligent flight technology based on passive detection and system coordination;

[0214] The specific design directions of the aircraft include shape layout, power form, take-off method, launch site / platform, flight profile, intelligent avoidance and autonomous attack based on passive perception, stealth measures and implementation methods;

[0215] (1) Appearance layout:

[0216] 1) High lift-to-drag ratio airfoil;

[0217] 2) Flying wing layout;

[0218] 3) Semi-enclosed missiles;

[0219] 4) Distributed ducted fans under the wings;

[0220] (2) Power form;

[0221] 1) Take-off: electric power or piston;

[0222] 2) Cruise phase: electric power;

[0223] 3) Attack stage: small solid rocket motor;

[0224] (3) Take-off method;

[0225] 1) Electric quadrotor flying aid;

[0226] 2) High-altitude parachute deployment;

[0227] (4) Launch site / platform;

[0228] 1) Land;

[0229] 2) Stratospheric airships and transport aircraft;

[0230] 3) Missile boats, destroyer / frigate ships, aircraft carriers, and prefabricated offshore platforms;

[0231] (5) Flight profile;

[0232] The anti-shipborne fixed-wing early warning aircraft changes its flight form as the flight mileage increases. The initial form is as follows:

[0233] The distributed ducted electric propulsion long-range UAV adopts a high lift-to-drag ratio airfoil and flying wing layout. It is tilted and installed at the wing tip with a very small inclination angle. Two thrust propellers ensure longitudinal static stability. The anti-AWACS missile is half-wrapped in the wing. There is a distributed ducted fan under the wing. A heavy-duty quadrotor flying aid that can be quickly installed / disassembled is installed on the UAV wing.

[0234] 1) 0-450m takeoff section:

[0235] On land, stratospheric airships, transport aircraft, missile boats, destroyer / protection ships, aircraft carriers, offshore prefabricated platforms and other sites / platforms, the heavy-duty quad-rotor flying aid can be quickly assembled / disassembled to assist takeoff. The power form is electric power or piston, and the flight altitude is 0-30m;

[0236] 2) 450m-575km cruising section:

[0237] Remove the heavy-duty quadrotor that can be quickly assembled / disassembled, and perform intelligent avoidance and autonomous attack based on passive detection and system coordination. The power form is electric power, and the flight altitude is 30m;

[0238] 3) 575km-600km attack segment:

[0239] Remove all structures of the distributed ducted electric propulsion long-range UAV except the missile, and use a small solid rocket engine as the power source, with a flight altitude of 30m-10km;

[0240] 4) 600km-625km attack segment;

[0241] The anti-AWACS missile is separated, powered by a two-stage rocket, and has a flight altitude of 10km;

[0242] (6) Intelligent avoidance and autonomous attack based on passive perception;

[0243] 1) Apply X-band passive conformal antenna: locate and attack MH-60R anti-submarine helicopter by intercepting and identifying AN / APS-147 multi-mode radar;

[0244] 2) Apply S-band passive conformal antenna: By intercepting and identifying AN / SPY-1D and AN / SPS-48E radars, it can intelligently avoid various types of ships;

[0245] 3) P-band passive conformal antenna: locate and attack Hawkeye AWACS by intercepting and identifying AN / APY-9 radar; intelligently avoid aircraft carriers and cruisers by intercepting and identifying AN / SPS-49(V) radar;

[0246] Stealth measures and implementation methods;

[0247] 1) Radar stealth: using sea clutter cover, high-strength wave-transmitting structure, wings and ducts to shield propellers, and thin-skin wave-transmitting propellers;

[0248] 2) RF stealth: cancel active radiation source, radar seeker adaptive power control, low intercept frequency (LPI) data link

[0249] The aircraft is autonomous and disposable, without active radar and uplink data link. It will not radiate electromagnetic waves during flight. When the passive radar antenna on the upper surface of the wing intercepts the enemy radar signal, the active radar seeker of the air-to-air missile starts to search for the target. After locking the target, it uses explosives to blow off the wing, and the solid rocket engine ignites to accelerate the missile to more than 3Ma to fly to the target. During the flight of the missile, as the missile-target distance R decreases, the radar seeker radiation power Pt∝1 / R^4 gradually decreases, that is, the seeker transmit power is adaptively controlled. In addition, the seeker adopts a continuous wave mode to minimize the peak power Pt.

[0250] For pulse radar, Pt·τ=Pav·T, where Pt is the peak power, τ is the pulse width, Pav is the average power, and T is the pulse repetition period. The larger the Pt, the easier it is to be intercepted by the enemy. Pav determines the effective range of the seeker to the nominal RCS target. The larger the Pav, the greater the effective range. Therefore, in theory, the use of continuous wave will have the best RF stealth performance. Here, linear frequency modulation continuous wave is used;

[0251] 3) Tactical stealth: intelligent trajectory planning based on passive perception;

[0252] 4) Infrared stealth: distributed ducted power, low-speed flight, background-fusion infrared stealth coating;

[0253] 5) Visible light stealth: spraying navy camouflage;

[0254] The aircraft adopts a (1) shape layout with a large lift-to-drag ratio to meet the requirements of long-range flight;

[0255] In order to avoid the infrared radiation characteristics of the engine and tail jet, the take-off phase adopts (2) power forms - electric power or piston, and the cruise phase adopts (2) power form - electric power;

[0256] Using (3) take-off method for vertical take-off and landing reduces energy consumption during climbing, and the reaction mechanism is more flexible. Only a small flat area is needed for take-off and landing. In war, aircraft can be deployed in a dispersed manner, which is convenient for camouflage and difficult to be discovered by the enemy, greatly improving the battlefield survival rate of aircraft;

[0257] Launching at (4) launch site / platform can make full use of the fact that it is difficult for early warning aircraft to detect "low, slow and small" targets against the background of sea clutter, and thus be protected by sea clutter;

[0258] Existing active radar-guided surface-to-air / air-to-air missiles are not designed specifically for attacking early warning aircraft. When facing early warning aircraft, they generally have problems of excessive maneuverability and relatively heavy mass, making them difficult to adapt to long-range electric drones. To solve this problem, a two-stage solid rocket booster solution is used in the attack phase of the (5) flight profile;

[0259] When the aircraft penetrates the early warning aircraft, (5) the low-altitude flight during the takeoff and cruise phases of the flight profile can place the aircraft within the main lobe clutter area, thereby improving the clutter shielding effect;

[0260] (6) Intelligent avoidance and autonomous attack based on passive perception: By attaching a multi-band large-area wing conformal passive antenna, the radar waves radiated by early warning aircraft, anti-submarine helicopters, ships and other platforms can be autonomously intercepted in flight, and the radar waves can be processed to achieve the functions of autonomous combat without system information support and coordinated combat under the command of high survivability platforms. By attaching a large-area wing conformal passive antenna, the radar waves radiated by early warning aircraft, anti-submarine helicopters, ships and other platforms can be autonomously intercepted in flight, and the corresponding information fusion, intelligent avoidance and autonomous attack algorithms are applied according to the actual combat situation. After the radar waves received by the passive conformal antenna are processed by information fusion, the intelligent avoidance algorithm and autonomous attack algorithm control the flight state of the aircraft to achieve intelligent threat avoidance technology based on passive autonomous detection and distributed UAV cluster coordinated penetration technology under the command of high survivability platforms;

[0261] (7) According to the spectral distribution characteristics of sea clutter, the RCS and flight speed of the aircraft are controlled so that its Doppler frequency is within the clutter spectrum range; according to the reflection characteristics of the sea surface to the ambient radiation under high-probability sea conditions, the emissivity of the aircraft surface material is controlled so that its infrared radiation brightness is similar to that of the ocean; through multidisciplinary integrated design optimization, the radar scattering / infrared radiation characteristics of the aircraft are integrated with the ocean background to achieve radar / infrared stealth;

[0262] The long range and slow speed characteristics require the UAV to have a larger aspect ratio and wing area, and a smaller leading edge sweep angle. The current absorbing materials do not have an absorbing effect in the P band, so it is difficult to reduce the P band RCS through appearance design and absorbing materials. In addition, the larger wing area will produce a stronger reflection of environmental radiation, forming a stronger infrared radiation brightness contrast with the ocean background. In response to this difficulty, the present invention reduces radar scattering and infrared scattering through (7) stealth measures and practical approaches.

[0263] The above formulas are all dimensionless and numerical calculations. The formula is a formula for the most recent real situation obtained by collecting a large amount of data and performing software simulation. The preset parameters in the formula are set by technicians in this field according to actual conditions.

[0264] The above embodiments may be implemented in whole or in part by software, hardware, firmware or any other combination thereof. When implemented by software, the above embodiments may be implemented in whole or in part in the form of a computer program product. Those skilled in the art may appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein may be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed by hardware or software methods depends on the specific application and design constraints of the technical solution.

[0265] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, and may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0266] The above description is only a specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application.

Claims

1. A design method for an anti-shipborne fixed-wing early warning aircraft, characterized in that: The specific steps include: Step S1, radar stealth design, collecting sea clutter spectrum data and aircraft shape parameters to evaluate and optimize the aircraft's radar cross section RCS; Step S2: Dynamic radar stealth technology, collecting RCS data under different radar frequency bands and response characteristics of smart materials, for dynamic adjustment of aircraft structure; Step S3, obtaining the sea clutter spectrum data and the aircraft shape parameters in step S1, extracting the key spectrum features of the sea clutter, analyzing the relationship between the aircraft RCS and the sea clutter spectrum, and constructing a first evaluation model of the aircraft RCS and the sea clutter spectrum, which is used to evaluate and determine the optimal stealth design parameters of the aircraft shape to achieve radar stealth optimization; Define the first evaluation model as M1; use the following function expression: Among them, LDλ is the radar wavelength calculation formula, LDf is the radar operating frequency; Fv is the wind speed, which is collected in real time by a weather station or anemometer; LDMk is the radar pulse width, which is directly obtained from the radar specification parameters; RCS veh It is the calculation model of the aircraft RCS, which depends on the specific parameters of the aircraft and is expressed by the following formula: RCS veh (Cd,Kd,Gd,BMc,DCs)=(Cd·Kd·Gd)·(1+η·BMc)·ζ(DCs) Where η and ζ(DCs) are the influence coefficients of surface roughness and electromagnetic parameters on RCS, respectively; A1, A2, A3, α, β, and γ are coefficients determined empirically based on sea clutter characteristics and aircraft characteristics; exp represents the natural exponential function, log represents the natural logarithmic function, and sin represents the sine function; Set the M1 value range to (0,100); the closer the M1 value is to 0, the better the stealth characteristic is, and the closer the M1 value is to 100, the worse the stealth characteristic is; Step S4, obtaining the RCS data in step S2 and the response characteristics of the smart material, analyzing the response of the smart material under different radar frequency bands, and constructing a second evaluation model of the temperature-deformation of the smart material, which is used to realize dynamic RCS control to optimize the dynamic stealth strategy; Step S5: Obtain the first evaluation model and the second evaluation model, analyze and process them, and construct a comprehensive adjustment model. The model screens and fine-tunes the evaluation results of each evaluation model based on the control system.

2. The design method of the anti-shipborne fixed-wing early warning aircraft according to claim 1 is characterized by: The sea clutter spectrum data includes radar wavelength, wind speed, radar operating frequency, and radar pulse width, and the radar wavelength is marked as LDλ, the wind speed is marked as Fv, the radar operating frequency is marked as LDf, and the radar pulse width is marked as LDMk; The aircraft shape parameters include the length, width, height, surface roughness, electromagnetic parameters, and structural shape of the aircraft, and the length value is marked as Cd, the width value is marked as Kd, the height value is marked as Gd, the surface roughness is marked as BMc, and the electromagnetic parameter is marked as DCs; The various structural shapes of the aircraft are annotated to form {G1, G2, ..., Gi, ..., n}, where Gi represents the structural shape formed by the combination of the i-th type of airfoil and fuselage shape, and the RCS corresponding to Gi is associated and annotated.

3. The design method of the anti-shipborne fixed-wing early warning aircraft according to claim 2 is characterized by: Acquire the sea clutter spectrum data and aircraft shape parameters in step S1, extract the key spectrum features of sea clutter, analyze the relationship between the aircraft RCS and the sea clutter spectrum, and construct a first evaluation model of the aircraft RCS and the sea clutter spectrum. The model is used to evaluate and determine the optimal stealth design parameters of the aircraft shape to achieve radar stealth optimization. Specifically, it includes the following contents: The value range of M1 (0,100) is divided into three intervals, each of which corresponds to a different level of stealth characteristics: Excellent stealth characteristics, M1∈(0,36); medium stealth characteristics, M1∈[36,68); poor stealth characteristics, M1∈[68,100); Excellent stealth performance range (0,36), within this range, the aircraft design reaches the high standard of stealth optimization, the RCS is significantly reduced, and the optimization rate exceeds 67%; the design focus includes fine-tuning the geometric dimensions, surface roughness and material electromagnetic properties to the optimal state; for any further design adjustments, it is necessary to strictly control their impact on the M1 value to ensure that the stealth characteristics are not affected; Medium stealth characteristic range [36,68), in which the aircraft's RCS is reduced by 33% to 67%, showing stealth capability, but there is still room for improvement; design work includes shape and material optimization to further reduce RCS; The judgment criteria focus on ensuring that any design changes will not increase the M1 value to the upper limit of the range, while improving the stealth performance to near the excellent range; Poor stealth performance range [68,100), the aircraft design in this range has poor stealth performance, and the RCS reduction is less than 33%; the design focus is to identify and correct the key factors that lead to high RCS values, including shape parameters, electromagnetic properties of materials and surface roughness; design adjustments must focus on significantly improving the M1 value to move towards the medium stealth performance range.

4. The design method of the anti-shipborne fixed-wing early warning aircraft according to claim 3 is characterized by: The RCS data includes frequency band specific data, directionality data, and dynamic change data; Band-specific data represents RCS values ​​measured in several key radar frequency bands; Assume there are N key radar frequency bands, and the RCS value of each frequency band is represented as a vector: RCS freq =[RCS1,RCS2,...,RCS N ], where RCS i′ represents the radar cross section in the i′th frequency band; Dynamically changing data represents the real-time RCS data when the aircraft is maneuvering or changing its attitude, so as to simulate the stealth effect in actual flight; Dynamic RCS data is represented as the following time series function: RCS dyn (t)=RCS freq (t)·RCS dir (t) Among them, RCS dyn (t) is the dynamic RCS value at time t, RCS freq (t) and RCS dir (t) are the frequency band-specific and directional RCS values ​​at time t, respectively; The response characteristics of the smart material include conductivity change, temperature response, mechanical stress response, and electromagnetic response; The conductivity change indicates the conductivity change of smart materials under different radar frequency bands; The conductivity change is expressed as σ(fi′)=σ0+Δσ(fi′); where σ(fi′) is the conductivity at frequency fi′, σ0 is the base conductivity, and Δσ(fi′) is the conductivity change at frequency fi′; Temperature response represents the deformation data of smart materials at different temperatures; The temperature response is expressed as the relationship between the deformation and temperature of the smart material, and the calculation formula is as follows: Among them, ò(T) is the deformation at temperature T, ò0 is the deformation at reference temperature T0, and a1 is the linear expansion coefficient of the material; Mechanical stress response refers to the deformation characteristics of smart materials when subjected to mechanical stress; Electromagnetic response refers to the response of smart materials under the action of electromagnetic fields, which is specifically expressed as the reflectivity and absorptivity of the material: A(fi′)=1-R(fi′) Wherein, R(fi′) is the reflectivity at frequency fi′, A(fi′) is the absorptivity at frequency fi′, Eref is the electric field strength of the reflected wave, and Einc is the electric field strength of the incident wave.

5. The design method of the anti-shipborne fixed-wing early warning aircraft according to claim 4 is characterized by: The RCS data and the response characteristics of the smart material in step S2 are obtained, the response of the smart material under different radar frequency bands is analyzed, and a second evaluation model of the temperature-deformation of the smart material is constructed, which is used to realize dynamic RCS control to optimize the dynamic stealth strategy; specifically, the following contents are included: The calculation formula of the second evaluation model is defined as follows: Among them, RCS dyn (t) is the dynamic RCS value at time t; RCS i′,j′ (t) is the radar cross section in the j′th direction at the i′th frequency band at time t; σ(fi′,T(t),σ′(t)) represents the conductivity change of the smart material under frequency fi′, temperature T(t) and stress σ′(t); w i′j′ It represents the weight coefficient of the j′th direction in the i′th frequency band, which is used to adjust the impact of different frequency bands and directions on the total RCS; The second evaluation model range is RCS dyn (t)∈[0,RCS max ], where RCS max It is an upper limit value set according to the maximum RCS value of the actual aircraft to ensure that the RCS value output by the model is within a reasonable range; By dynamically adjusting the aircraft structure and intelligent material properties, RCS dyn (t) Maintaining a low value range to achieve an optimized dynamic stealth strategy; Ensure that σ0, Δσ(fi′), a1, and E1 in the conductivity change formula are non-zero to avoid invalid or conflicting calculation results when the parameters are zero, and obtain the following adjusted second evaluation model formula: The value range of the second evaluation model formula is further limited to (0,100), and the adjusted formula is: When RCS dyn (t) The value is close to 0, which means that the stealth effect of the aircraft is good at that moment and it is difficult to be detected by radar; When RCS dyn A (t) value close to 100 indicates that the stealth effect of the aircraft at that moment is poor and it is easy to be detected by radar.

6. The design method of the anti-shipborne fixed-wing early warning aircraft according to claim 5 is characterized by: The value range (0,100) of the second evaluation model is divided into several intervals, namely interval 1 (0,26), interval 2 [26,52), and interval 3 [52,100); Interval 1 (0,26), in this interval, RCS dyn (t) values ​​below 26 indicate that the aircraft has excellent stealth effect; intelligent materials and flight strategies work together efficiently to reduce the probability of being detected by radar by more than 70%; at this stage, the aircraft optimizes the stealth effect by precisely adjusting material properties and flight attitude; Interval 2 [26,52), RCS dyn (t) When the value is between 26 and 52, the aircraft exhibits general stealth performance. In this range, although the stealth effect is reduced, it is still intended to maintain a low radar detection rate by adjusting the smart material response and optimizing the flight dynamics; Range 3 [52,100), in this range, the stealth effect is poor; the aircraft needs to further optimize the characteristics of smart materials and adjust the flight strategy to reduce the radar detection area and try to improve the stealth performance to cope with the high radar detection risk.

7. The design method of the anti-shipborne fixed-wing early warning aircraft according to claim 6 is characterized by: The first evaluation model and the second evaluation model are obtained, analyzed and processed, and a comprehensive adjustment model is constructed. The model screens and fine-tunes the evaluation results of each evaluation model based on the control system, and specifically includes the following contents: The comprehensive adjustment model is defined as CM(t), and the calculation formula is as follows: Where S(·) is the Sigmoid function, which is used to smooth and limit the range of CM(t) to (0,1) and is defined as x represents k is a coefficient used to adjust the slope of the Sigmoid function. Increasing k will make the Sigmoid function steeper near x=0; Yz is a threshold parameter used to adjust the midpoint position of the Sigmoid function; d1 and d2 are weighting coefficients, which are allocated according to the importance of the two evaluation models in the overall evaluation; M max is the maximum value of the first evaluation model, which is used to normalize the output of the first evaluation model; 100 in the function is the upper limit value of the second evaluation model; CM(t) is the comprehensive adjustment model score at time t; M1 is the output of the first evaluation model; RCS dyn (t) is the output of the second evaluation model at time t; When CM(t) is closer to 1, it means that the comprehensive stealth performance of the aircraft at the current time point is better, that is, it shows good stealth characteristics under both static and dynamic conditions; when CM(t) is closer to 0, it means that the comprehensive stealth performance of the aircraft at the current time point is worse; The value range (0,1) of CM(t) is divided into three main intervals, namely the low performance area (0,0.33), the medium performance area [0.33,0.67), and the high performance area [0.67,1); Low performance area (0,0.33), the control system is in the low performance area for M1 and RCS dyn (t) Perform screening and fine-tuning, giving priority to the stealth defects with the greatest impact; if the static model M1 contribution is significantly low, automatically increase the attitude adjustment to restore at least 15% of the stealth performance; at the same time, according to M1 and RCS dyn (t) Contribution adjustment d1 and d2 to ensure fast response and effective stealth performance recovery; Medium performance area [0.33, 0.67), in the medium performance area, the control system adopts a balanced strategy, according to M1 and RCS dyn (t) Fine-tune data weights to achieve maximum performance improvement; adjust flight parameters or material properties to reduce RCS dyn (t) affects and improves the CM(t) value; High performance zone [0.67,1), the control system in the high performance zone is fine-tuned to maintain the excellent stealth performance of the aircraft in dynamic and static conditions, monitor small changes within 5%, adjust 10% of the electronic countermeasures and flight parameters, and maintain high stealth performance with minimum RCS; optimization involves 35%-65%, and the 5% trade-off between M1 and RCS is considered dyn (t) fine-tuning.

8. An anti-shipborne fixed-wing early warning aircraft aircraft, characterized in that: The aircraft is used to execute the design method of the anti-shipborne fixed-wing early warning aircraft aircraft described in any one of claims 1-7, including: a distributed ducted electric propulsion long-range UAV, a heavy-loaded quadcopter that can be quickly assembled / disassembled, an anti-earthquake warning aircraft missile adapted for electric UAVs, and UAV intelligent flight technology based on passive detection and system collaboration.

Images