Dynamic broadband echo modeling and calculating method for chaff cloud cluster
By employing a hybrid deterministic and statistical method and BVH tree technology, the problem of low efficiency in broadband echo simulation of chaff clouds was solved, achieving efficient and accurate dynamic broadband echo calculation of chaff clouds and meeting real-time simulation requirements.
Patent Information
- Application Number
- CN202511673024.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-14
- Publication Date
- 2026-02-27
AI Technical Summary
Existing technologies have low computational efficiency in broadband echo simulation of foil clouds, cannot meet real-time requirements, and lack consideration for complex real-world environments, resulting in inaccurate calculation results.
A hybrid deterministic and statistical method was adopted, combining the dynamic BVH tree of the chaff cloud and the incident direction of electromagnetic waves, to calculate the length ratio of the chaff filaments irradiated by electromagnetic waves. Coherent accumulation was then performed using radar pulse parameters to generate two-dimensional broadband echo data of the chaff cloud.
It achieves efficient and accurate calculation of dynamic broadband echo of foil clouds, meets the requirements of real-time simulation, and improves simulation efficiency and accuracy.
Smart Images
Figure CN121582291A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the field of target and environmental interference characteristics simulation, and particularly relates to a method for modeling and calculating dynamic wideband echoes of a chaff cloud. BACKGROUND
[0002] A chaff cloud is composed of a large number of chaff filaments, and interferes with radar detection by forming a large-area electromagnetic scatterer, thereby forming an electronic warfare interference means. The movement of the chaff cloud is a random dynamic diffusion process related to the projection direction, initial speed, wind speed, etc., and contains hundreds of thousands or even millions of chaff filaments, each of which changes position during the diffusion process. For a high-dynamic random chaff cloud, how to quickly and accurately calculate the wideband echo has become a research hotspot, and domestic and foreign experts and scholars have carried out a large amount of research, forming two simulation methods of Monte Carlo method and moment method, and promoting the development of electromagnetic scattering characteristics of chaff clouds.
[0003] However, how to improve the efficiency of the simulation of the wideband echo of the chaff cloud and promote the application of the chaff cloud in related fields is still a real challenge faced by experts and scholars today. At present, the common method is to optimize the existing Monte Carlo method or moment method, and develop a faster algorithm; another method is to use GPU hardware acceleration and distributed parallel computing acceleration. The above two methods have disadvantages, the first method cannot make the calculation efficiency decrease exponentially, and the second method is difficult to build a large parallel computing system. In the electromagnetic scattering modeling of the chaff cloud, whether the parallel strategy or the algorithm optimization is used to accelerate the scattering solution, the simulation efficiency is still slow and cannot meet the real-time requirements.
[0004] In addition, the movement modeling of the chaff cloud is usually based on the statistical movement law and does not consider the influence of the actual complex environment, for example, the average RCS (radar cross section) of the chaff is calculated, the scattering characteristics of individual chaff are lacking; or the RCS of the chaff cloud at the fixed position after the diffusion of the chaff is calculated, the individual differences of different chaff scattering and the scattering characteristics in the movement process of the chaff are lacking.
[0005] Therefore, there is an urgent need for a method that mixes deterministic and statistical methods to efficiently and accurately calculate the movement process and wideband echo of the chaff cloud.
[0006] The statements herein only provide background technology related to the present application, and do not necessarily constitute the prior art. SUMMARY
[0007] The purpose of the present application is to provide a method for modeling and calculating dynamic wideband echoes of a chaff cloud, so as to overcome the problems of long time consumption, inaccurate precision and inability to meet real-time simulation requirements in the prior art.
[0008] In order to achieve the above object, the present application provides a foil cloud dynamic broadband echo modeling and calculating method, comprising: S1, establishing a test data corrected foil cloud motion model; S2, calculating the motion state of the foil filament in the foil cloud, constructing a foil cloud dynamic BVH tree, and combining the electromagnetic wave incidence direction to calculate the length proportion of the part of the foil filament in the foil cloud irradiated by the electromagnetic wave as the echo amplitude proportion of the foil filament; S3, calculating the echo amplitude of the foil filament, and calculating the broadband echo of a pulse of the foil cloud; S4, calculating the two-dimensional echo data of the foil cloud.
[0009] Optionally, the step S1 comprises: S1.1, determining a foil motion equation; S1.2, extracting the foil cloud contour and its density data according to the foil cloud diffusion image shot by a high-speed camera; S1.3, correcting the foil motion equation according to the real contour and density data of the foil cloud at different times to obtain a foil cloud motion model.
[0010] Optionally, the foil motion equation comprises a fast diffusion motion equation and a stable diffusion motion equation; The fast diffusion motion equation is: ; The stable diffusion motion equation is: ; In the formula, and respectively represent the acceleration of the foil filament in the horizontal and vertical directions at a certain time; is the tangential force, is the normal force; is the inclination angle of the foil filament with the vertical direction; is the average equivalent mass corresponding to the collision force between any two foil filaments, N is the number of adhesion, is the length of a single foil filament, is the cross-sectional radius of a single foil filament, is the acceleration of gravity, represents the difference between the foil filament density and the air density where the current foil filament is located.
[0011] Optionally, the step S1.3 is specifically: According to the foil strip motion equation of the single foil strip determined in the step S1.1, the motion of the plurality of foil strips is simulated by a computer to obtain a macroscopic diffusion prediction of the entire foil cloud, and the prediction result is compared with the profile and density data shot by the high-speed camera. If there is a difference, the parameters in the foil strip motion equation are returned to be corrected until the prediction result matches the real macroscopic data. The corrected foil strip motion equation is the final foil cloud motion model.
[0012] Optionally, the step S2 includes: S2.1, at the calculation frame time, using the corrected foil cloud motion model, the motion state of each foil strip at the current time in the foil cloud is calculated, and the motion state at least includes the position and attitude of each foil strip in the three-dimensional space; S2.2, a dynamic BVH tree of the foil cloud is constructed, based on the BVH tree generated at the previous time step, and combined with the motion state of each foil strip at the current time calculated in the step S2.1, a bottom-up updating strategy is adopted to generate the dynamic BVH tree corresponding to the current time; S2.3, for each foil strip contained in the dynamic BVH tree, combined with the direction of the incident electromagnetic wave, the proportion of the irradiated part of the foil strip to the total length of the foil strip is calculated as the echo amplitude ratio of the foil strip based on the principle of dichotomy; The echo amplitude ratio is used to describe the ratio of the actual value of the echo amplitude to the ideal value of the echo amplitude.
[0013] Optionally, the step S2.3 includes: S2.3.1, whether the two ends and the midpoint of the foil strip are irradiated is calculated. If both are irradiated, it is considered that the foil strip is completely irradiated, and the echo amplitude ratio is 1. If both are blocked, it indicates that the foil strip is completely blocked, and the echo amplitude ratio is 0; S2.3.2, if one or two of the three points of the two ends and the midpoint of the foil strip are irradiated, it indicates that the foil strip is in a partially irradiated state. Then, the midpoint between the irradiated point and the adjacent blocked point is detected repeatedly, and the search interval is halved step by step according to whether the midpoint is irradiated or not until the irradiation boundary is accurately located. Finally, the length of the irradiated part of the foil strip is recorded. S2.3.3, the ratio of the length of the irradiated part to the total length of the foil strip is calculated to determine the final echo amplitude ratio of the foil strip.
[0014] Optionally, the step S3 includes: S3.1, using a statistical method, the broadband echo of the completely illuminated foil strip under different electromagnetic wave incident angles is pre-sampled according to a specific sampling frequency, and is continuously stored with the electromagnetic wave incident angle as an index, so as to facilitate subsequent retrieval of echo data according to the index; The echo data at least includes echo amplitude data and echo phase data; Wherein, the echo amplitude of the foil strip being fully illuminated is the ideal value of the echo amplitude of the foil strip being partially illuminated at the same electromagnetic wave incidence angle; S3.2, for each foil strip in the dynamic BVH tree, according to the incidence angle of the electromagnetic wave, indexing the known foil strip echo data, obtaining the ideal value of the echo amplitude of the foil strip by interpolation method, and calculating the actual value of the echo amplitude of the foil strip contributing to the total echo; S3.3, combining the transmission parameters and receiving parameters of the radar pulse, correcting the echo width and storage time, coherently accumulating the contributions of all foil strips, and finally synthesizing the total echo data of the complete foil cloud group in a pulse period.
[0015] Optionally, in step S3.1, the scattering intensity of the foil strip being fully illuminated at the center frequency point is taken as the echo amplitude of the foil strip.
[0016] Optionally, the step S3.2 is specifically: Suppose the current electromagnetic wave incidence angle is theta, and the two adjacent nearest integers are thetaN1 and thetaN2, and the wideband echoes corresponding to thetaN1 and thetaN2 are echo1 and echo2 respectively, then the wideband echo at the current angle theta is represented as: echo = (theta-thetaN1) × echo1 + (thetaN2-theta) × echo2; Combined with the echo amplitude ratio calculated in step S2, the actual value of the echo amplitude of the foil strip is calculated, and the actual value of the echo amplitude = echo amplitude ratio × ideal value of the echo amplitude.
[0017] Optionally, the step S4 includes: S4.1, considering the influence of antenna motion on echo phase to correct echo phase data, calculating the antenna position at different transmission pulse moments; S4.2, in a frame coherent processing time, the echo amplitude is approximately treated as invariant, and the echo phase is accurately calculated; According to the antenna position and the foil strip position, the electromagnetic wave propagation path is calculated, so as to obtain accurate phase information; S4.3, a frame coherent processing time contains several pulse signals, and the amplitude and phase information of the wideband echo in each pulse period are obtained in turn to form the two-dimensional echo data of the foil cloud group.
[0018] Compared with the prior art, the present application combines the determination method and the statistical method, initiatively uses the BVH tree in the graphics to efficiently judge the shielding condition in the complex cloud cluster, and combines the pre-calculated statistical echo data and the accurate Doppler phase calculation, so that the two-dimensional wideband echo data capable of reflecting the foil cloud cluster dynamics and the Doppler characteristics can be generated with extremely high calculation efficiency, the advantages of the determination method and the statistical method are fully utilized, and the wideband echo of the foil cloud cluster is quickly and accurately obtained. BRIEF DESCRIPTION OF DRAWINGS
[0019] Figure 1 The present application is a step flow chart for the implementation of the present application; Figure 2 The present application is a foil stress analysis diagram; Figure 3 The present application is a foil cloud cluster profile and density representation; Figure 4 The present application is an echo data format schematic diagram. DETAILED DESCRIPTION
[0020] The foil cloud cluster dynamic wideband echo modeling and calculation method proposed in the present application will be further described in detail below in combination with the drawings and specific embodiments. According to the following description, the advantages and features of the present application will be more apparent. It should be noted that the drawings are very simplified and all use non-precise proportions, only for the purpose of facilitating and clarifying the description of the embodiments of the present application. In order to make the purpose, features and advantages of the present application more apparent and easy to understand, please refer to the drawings. It should be noted that the structures, proportions, sizes, etc. shown in the drawings attached to the present specification are only used to cooperate with the content disclosed in the specification, so that those skilled in the art can understand and read, and are not used to limit the implementation of the present application, so they do not have technical significance. Any modification of structure, change of proportion relationship or adjustment of size, which does not affect the effect and purpose that can be achieved by the present application, should still fall within the scope of the technical content disclosed by the present application.
[0021] Echo refers to the part of the wave emitted by the transmitting source, which is reflected or scattered back and detected by the receiving device after encountering an object in the propagation path. In the present application, echo refers to the part of the electromagnetic wave emitted by the radar antenna, which is scattered back and detected by the receiving device after encountering the foil cloud cluster in the propagation path. The radar antenna in modern radar systems usually transmits a wideband electromagnetic wave signal, and the part of the wideband electromagnetic wave signal that is reflected back after encountering the target and still maintains or carries the original frequency range information is called wideband echo. The most important and most widely used form of wideband echo is wideband pulse echo.
[0022] As shown in Figure 1 The present application provides a foil cloud cluster dynamic wideband echo modeling and calculation method, which comprises the following steps: S1, establish a test data correction foil cloud movement model, specifically comprising the following steps: S1.1, the diffusion process of the foil cloud is divided into a rapid diffusion stage and a stable diffusion stage, Figure 2 is a force analysis diagram of the foil wire, according to Figure 2 the force analysis diagram, the foil movement equation is determined, the foil movement equation includes a rapid diffusion movement equation and a stable diffusion movement equation; In the rapid diffusion stage, since multiple foil wires have not yet completely dispersed, there are multiple adhesion bodies composed of multiple foil wires adhering together; an adhesion body acts as a whole in the air and is forced to move, and in this adhesion body, one of the foil wires collides with other foil wires during the movement process, such collision is random and short, and in the movement process, the collision force is equivalent to the mass of the foil wire. The rapid diffusion movement equation of the foil is: ; In the formula, and respectively represent the acceleration of the foil wire in the horizontal and vertical directions at a certain time; is the tangential force, is the normal force; is the inclination angle of the foil wire with the vertical direction; is the average equivalent mass corresponding to the collision force between any two foil wires, N is the adhesion number, that is, the number of foil wires contained in an adhesion body, is the equivalent mass corresponding to the collision force of a single foil wire with all other foil wires, Therefore is the horizontal component of the interaction force between a single foil wire and all other foil wires, is the vertical component of the interaction force between a single foil wire and all other foil wires; is the length of a single foil wire, is the cross-sectional radius of a single foil wire, is the acceleration of gravity, represents the difference between the density of the foil wire and the current air density in which the foil wire is located.
[0023] With the passage of time and air disturbance, the adhesion body will eventually completely disintegrate, and each foil wire becomes an independent movement unit, at which time it enters the stable diffusion stage, so the number factor N is no longer included in the stable diffusion movement equation; the stable diffusion movement equation is: .
[0024] S1.2, according to the diffusion image of the foil cloud taken by the high-speed camera, extract the contour and density data of the foil cloud.
[0025] The foil cloud cluster profile refers to the external boundary occupied by the entire foil cloud cluster in space at a certain moment, which is specifically represented by a series of discrete three-dimensional points, and the direction between adjacent two points has directionality, and the left side of the direction is the foil cloud cluster diffusion area, as shown in the following figure: Figure 3 The foil cloud cluster density refers to the number distribution of foil filaments in different regions inside the entire foil cloud cluster, which is specifically discretized by a cubic grid in the foil cloud cluster diffusion area, and the foil density data in the cubic grid is stored, that is, how many randomly moving foil filaments are stored in each cubic grid unit.
[0026] S1.3, according to the real profile and density data of the foil cloud cluster at different moments, correcting the foil motion equation to obtain a foil cloud cluster motion model.
[0027] Specifically, according to the foil motion equation (micro motion equation) of a single foil filament determined in step S1.1, the motion of thousands of foil filaments is simulated by computer to obtain the macro diffusion prediction of the entire foil cloud cluster, and the prediction result is compared with the real macro data (profile and density data) shot by the high-speed camera. If there is a difference, return to correct the parameters in the foil motion equation until the prediction result matches the real macro data; the corrected foil motion equation is the final foil cloud cluster motion model.
[0028] The foil cloud cluster motion model is no longer an ideal motion equation established according to the force condition, but a motion equation corrected according to the profile and density of the foil cloud cluster in the actual environment, which is closer to the actual environment.
[0029] S2, calculate the length proportion of the part of the foil filament irradiated by the electromagnetic wave in the foil cloud cluster as the echo amplitude proportion of the foil filament, specifically including the following steps: S2.1, at the calculation frame moment, using the corrected foil cloud cluster motion model, calculate the motion state of each foil filament at the current moment in the foil cloud cluster, the motion state at least includes the position and attitude of each foil filament in three-dimensional space; the calculation frame moment refers to a discrete, pre-set time point in computer simulation for updating and recording the motion state of the foil filament, the actual diffusion process of the foil cloud cluster is continuous, while in computer simulation, the continuous time axis is discretized into a plurality of time points.
[0030] S2.2, construct a dynamic BVH tree (Bounding Volume Hierarchy) of the foil cloud cluster, specifically, based on the BVH tree generated at the previous time step, and combined with the motion state of each foil filament at the current moment calculated in step S2.1, a bottom-up updating strategy is adopted to generate a dynamic BVH tree corresponding to the current moment; The BVH tree, full name bounding volume hierarchy or hierarchical bounding volume, is a tree data structure for efficient management and query of a large set of geometric objects in three-dimensional space; Each node in the BVH tree is composed of the bounding box of the foil filament corresponding to the node, and the calculation of the foil filament can be approximated as the calculation of the bounding box.
[0031] S2.3、For each foil filament contained in the dynamic BVH tree generated in step S2.2, in combination with the direction of the incident electromagnetic wave, the proportion of the illuminated part of the foil filament to the total length of the foil filament is calculated as the echo amplitude ratio of the foil filament by bisection, the echo amplitude ratio is a unitless ratio factor (correction factor), usually between 0 and 1, used to describe the ratio of the actual value of the echo amplitude to the ideal value of the echo amplitude; Specifically comprising the following steps: S2.3.1、Firstly, calculate whether the two ends and the midpoint of the foil filament are illuminated, if both are illuminated, it is considered that the foil filament is completely illuminated, and the echo amplitude ratio is 1; if both are blocked, it indicates that the foil filament is completely blocked, and the echo amplitude ratio is 0; S2.3.2、If one or two of the three points of the two ends and the midpoint of the foil filament are illuminated, it indicates that the foil filament is partially illuminated, then by repeatedly detecting the midpoint between the illuminated point and the adjacent blocked point, and according to the state (whether illuminated) of the midpoint, the search interval is gradually halved, until the illumination boundary is accurately located, and finally the length of the illuminated part of the foil filament is recorded.
[0032] S2.3.3、Calculate the ratio of the length of the illuminated part to the total length of the foil filament to determine the final echo amplitude ratio of the foil filament.
[0033] In the present application, the foil filament illuminated by the electromagnetic wave is no longer only judged whether it is illuminated, but the proportion of the length of the illuminated part to the total length is accurately calculated, and the proportion is used for subsequent calculation of the real value of the echo amplitude.
[0034] S3、Calculate the broadband echo of a pulse of the foil cloud cluster, specifically comprising the following steps: S3.1、Using a statistical method, pre-sample the broadband echo of the completely illuminated foil filament under different electromagnetic wave incident angles according to a specific sampling frequency, and store the broadband echo continuously indexed by the electromagnetic wave incident angle, so as to facilitate subsequent retrieval of the echo data according to the index; the echo data refers to the complete waveform, at least including echo amplitude data and echo phase data; Wherein, the scattering intensity of the completely illuminated foil filament at the center frequency point is taken as the echo amplitude of the foil filament, and the echo amplitude is also the ideal value of the echo amplitude of the partially illuminated foil filament under the same electromagnetic wave incident angle.
[0035] S3.2, for each foil filament in the dynamic BVH tree, according to the incident angle of the electromagnetic wave, index the known foil filament echo data, obtain the ideal value of the echo amplitude of the foil filament by the method of interpolation, and then calculate the actual value of the echo amplitude of the foil filament contribution to the total echo.
[0036] Specifically, assuming that the current incident angle of the electromagnetic wave is theta, and the two nearest integers adjacent to it are thetaN1 and thetaN2, and the wideband echoes corresponding to thetaN1 and thetaN2 are echo1 and echo2 respectively, then the wideband echo at the current angle theta is represented as: echo = (theta - thetaN1) x echo1 + (thetaN2 - theta) x echo2 Combined with the echo amplitude ratio calculated in step S2.3, the actual value of the echo amplitude of the foil filament is calculated, actual value of echo amplitude = echo amplitude ratio x ideal value of echo amplitude.
[0037] S3.3, combined with the transmission parameters and reception parameters of the radar pulse, correct the echo width and storage time, and coherently accumulate the contributions of all foil filaments to finally synthesize the total echo data of the complete foil cloud cluster in a pulse period.
[0038] S4, calculate the two-dimensional echo data of the foil cloud cluster, specifically including the following steps: S4.1, consider the influence of the antenna and the foil cloud cluster motion on the echo phase to correct the echo phase data. In a frame coherent processing time, both the antenna and the foil cloud cluster are in motion, but the motion of the foil cloud cluster itself is relatively slow, and the echo phase change caused by it can be ignored; while the motion of the antenna is the dominant factor leading to significant changes in the echo phase, and cannot be ignored, so only the antenna position at different transmission pulse moments is calculated.
[0039] S4.2, in a frame coherent processing time, the echo amplitude is approximately constant, while the echo phase will change greatly, therefore, the echo phase of the foil cloud cluster needs to be accurately calculated.
[0040] The method of accurately calculating the echo phase is to calculate the electromagnetic wave propagation path according to the antenna position and the foil filament position, so as to obtain accurate phase information.
[0041] S4.3, a frame coherent processing time contains several pulse signals, and the amplitude and phase information of the wideband echo in each pulse period are obtained in turn to form the two-dimensional echo data of the foil cloud cluster, and the data format is as shown in Figure 4 Specifically, in one frame coherent processing time, the radar antenna continuously transmits several pulses, and each received wideband echo is digitized and collected one by one, and the amplitude and phase information of each wideband echo is recorded to form a data matrix. The data matrix containing the dynamic change information of the wideband echo is the foil cloud cluster two-dimensional echo data, which is the basic data for a series of subsequent key signal processing algorithms.
[0042] In summary, the hybrid determination and statistical method of the patent uses the BVH tree in graphics to efficiently determine the occlusion in the complex cloud cluster, and combines the pre-calculated statistical echo data and the accurate Doppler phase calculation to generate two-dimensional wideband echo data that can reflect the dynamic and Doppler characteristics of the foil cloud cluster with extremely high calculation efficiency.
[0043] It should be noted that in this document, the terms "comprise", "contain" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such a process, method, article or equipment. Without more limitations, the element defined by the statement "comprises a" does not exclude the presence of another identical element in the process, method, article or equipment that includes the element.
[0044] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "height", "thickness", "upper", "lower", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential" and the like is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.
[0045] In the description of the present application, unless otherwise specified and limited, the terms "mounting", "connection", "connection", "fixing" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integral; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.
[0046] In the present application, unless specifically stated and limited otherwise, the "on" or "under" of a first feature to a second feature can include that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, the "on", "above" and "on top of" of a first feature to a second feature includes that the first feature is directly above and obliquely above the second feature, or only means that the first feature is horizontally higher than the second feature. The "under", "below" and "underneath" of a first feature to a second feature includes that the first feature is directly below and obliquely below the second feature, or only means that the first feature is horizontally lower than the second feature.
[0047] Although the present application has been described in detail by the foregoing preferred embodiments, it should be recognized that the foregoing description is by way of example only and that various modifications and substitutions can be made by those skilled in the art without departing from the scope of the present application. Accordingly, the scope of the present application should be limited only by the appended claims.
Claims
1. A method for modeling and calculating dynamic broadband echoes of foil clouds, characterized in that, include: S1. Establish a motion model for the foil cloud clusters based on the corrected test data; S2. Calculate the motion state of the foil filaments in the foil cloud, construct the dynamic BVH tree of the foil cloud, and combine the electromagnetic wave incident direction to calculate the length ratio of the part of the foil filaments in the foil cloud that is irradiated by the electromagnetic wave, as the echo amplitude ratio of the foil filaments. S3. Calculate the echo amplitude of the foil strands and calculate the broadband echo of one pulse of the foil cloud; S4. Calculate the two-dimensional echo data of the foil cloud.
2. The method for dynamic broadband echo modeling and calculation of foil clouds as described in claim 1, characterized in that, Step S1 includes: S1.1 Determine the equation of motion for the foil strip; S1.2 Extract the outline and density data of the chaff cloud based on the diffusion image of the chaff cloud captured by the high-speed camera; S1.
3. Based on the actual contour and density data of the foil cloud at different times, revise the foil motion equation to obtain the foil cloud motion model.
3. The method for dynamic broadband echo modeling and calculation of foil cloud as described in claim 2, characterized in that, The equations of motion for the foil strip include the equations of rapid diffusion and the equations of steady diffusion. The equation for rapid diffusion is: ； The equation for steady-state diffusion is: ； In the formula, and These represent the accelerations of the foil filaments at a certain moment in the horizontal and vertical directions, respectively. For tangential force, Normal force; The angle between the foil wire and the vertical direction; Let be the average equivalent mass corresponding to the collision force between any two foil filaments. N This refers to the amount of adhesion. The length of a single foil strand. The cross-sectional radius of a single foil filament. It is the acceleration due to gravity. This represents the difference between the foil filament density and the air density where the foil filament is located.
4. The method for dynamic broadband echo modeling and calculation of foil clouds as described in claim 2, characterized in that, Step S1.3 specifically includes: Based on the foil motion equation of a single foil filament determined in step S1.1, the movement of multiple foil filaments is simulated by computer to obtain the macroscopic diffusion prediction of the entire foil cloud. The prediction result is compared with the contour and density data captured by a high-speed camera. If there is a difference, the parameters in the foil motion equation are corrected until the prediction result matches the actual macroscopic data. The corrected foil motion equation is the final foil cloud motion model.
5. The method for dynamic broadband echo modeling and calculation of foil clouds as described in claim 1, characterized in that, Step S2 includes: S2.1 At the time of calculation frame, the modified foil cloud motion model is used to calculate the motion state of each foil filament in the foil cloud at the current time. The motion state includes at least the position and orientation of each foil filament in three-dimensional space. S2.2 Construct a dynamic BVH tree for the foil cloud. Based on the BVH tree generated in the previous time step and combined with the motion state of each foil filament at the current moment calculated in step S2.1, a bottom-up update strategy is adopted to generate a dynamic BVH tree corresponding to the current moment. S2.3 For each foil filament contained in the dynamic BVH tree, based on the electromagnetic wave incident direction and the principle of bisection, calculate the proportion of the irradiated part of the foil filament to the total length of the foil filament, and use it as the foil filament echo amplitude proportion. The echo amplitude ratio is used to describe the ratio of the actual echo amplitude to the ideal echo amplitude.
6. The method for dynamic broadband echo modeling and calculation of foil clouds as described in claim 5, characterized in that, Step S2.3 includes: S2.3.1 Calculate whether the two ends and the midpoint of the foil strip are illuminated. If they are all illuminated, the foil strip is considered to be fully illuminated, and its echo amplitude ratio is 1. If they are all blocked, the foil strip is completely blocked, and its echo amplitude ratio is 0. S2.3.2 If one or two of the three points—the two ends and the midpoint of the foil strand—are illuminated, it indicates that the foil strand is partially illuminated. Then, by repeatedly detecting the midpoint between an illuminated point and an adjacent blocked point, and by gradually halving the search interval based on whether the midpoint is illuminated, the illumination boundary is precisely located, and finally the length of the illuminated part of the foil strand is recorded. S2.3.3 Calculate the ratio of the length of the irradiated part to the total length of the foil strand, and determine it as the final echo amplitude ratio of the foil strand.
7. The method for dynamic broadband echo modeling and calculation of foil clouds as described in claim 1, characterized in that, Step S3 includes: S3.1 Using a statistical method, broadband echoes of fully illuminated foil filaments under different electromagnetic wave incident angles are presampled at a specific sampling frequency, and stored continuously with the electromagnetic wave incident angle as an index, so as to facilitate subsequent retrieval of echo data based on the index. The echo data includes at least echo amplitude data and echo phase data; Among them, the echo amplitude of the fully illuminated foil filament is the ideal value of the echo amplitude of the partially illuminated foil filament under the same electromagnetic wave incident angle; S3.2 For each foil filament in the dynamic BVH tree, based on the incident angle of the electromagnetic wave, the known foil filament echo data is indexed, and the ideal value of the echo amplitude of the foil filament is obtained by interpolation. Then, the actual value of the echo amplitude contributed by the foil filament to the total echo is calculated. S3.
3. Combining the transmission and reception parameters of the radar pulse, the echo width and storage time are corrected, and the contributions of all chaff filaments are coherently accumulated to finally synthesize the total echo data of the complete chaff cloud within one pulse cycle.
8. The method for dynamic broadband echo modeling and calculation of foil clouds as described in claim 7, characterized in that, In step S3.1, the scattering intensity of the fully illuminated foil filament at the center frequency is taken as the echo amplitude of the foil filament.
9. The method for dynamic broadband echo modeling and calculation of foil clouds as described in claim 7, characterized in that, Step S3.2 specifically includes: Assuming the current incident angle of the electromagnetic wave is theta, and the two nearest integers to it are thetaN1 and thetaN2, and the broadband echoes corresponding to thetaN1 and thetaN2 are echo1 and echo2 respectively, then the broadband echo echo at the current angle theta is represented as: echo = (theta - thetaN1) × echo1 + (thetaN2 - theta) × echo2; Based on the echo amplitude ratio calculated in step S2, the actual value of the echo amplitude of the foil strip is calculated. The actual value of the echo amplitude = echo amplitude ratio × ideal value of the echo amplitude.
10. The method for dynamic broadband echo modeling and calculation of foil clouds as described in claim 1, characterized in that, Step S4 includes: S4.
1. Consider the influence of antenna movement on echo phase to correct the echo phase data, and calculate the antenna position at different transmit pulse times; S4.2 Within one frame of coherent processing time, the echo amplitude is treated to remain approximately constant, while the echo phase is calculated precisely. The electromagnetic wave propagation path is calculated based on the antenna position and the foil wire position, thereby obtaining accurate phase information; S4.
3. A frame of coherent processing contains several pulse signals. The amplitude and phase information of the broadband echo in each pulse period are obtained in sequence to form two-dimensional echo data of the foil cloud.