Design method of high-wave-transparent electrothermal film based on multi-target genetic algorithm

Abstract

The invention relates to the technical field of frequency selective surfaces and thermal management, in particular to a design method of a high-wave-transparent electrothermal film based on a multi-target genetic algorithm. Obtaining design parameters of the high-permeability electrothermal film; comprising the area, material parameters and thermal diffusion coefficients of a design region; establishing a plurality of rectangular grids to generate a power-on path to obtain a frequency selective surface population; acquiring heat conduction performance and wave-transparent performance of the surface population; performing non-dominated sorting on the frequency selective surface population to obtain a plurality of non-dominated layers; calculating the crowding degree of each individual in each non-dominated layer, and generating a parent population by adopting a genetic algorithm according to the crowding degree; performing crossover and mutation operation according to the parent population to generate a filial population; and combining the parent population and the child population, repeating the steps until a set number of iterations is reached, and generating a group of Pareto optimal solutions. According to the method, the problem of obtaining the parameter equalization optimization result during multi-objective optimization can be solved, and the design efficiency and quality are effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of frequency selective surfaces and thermal management, and in particular to a design method for a high-wave-transmitting electric heating film based on a multi-objective genetic algorithm. Background Art

[0002] Frequency selective surfaces, as artificial structures that can filter electromagnetic waves of specific frequencies, are widely used in communications, radar, satellites and other fields. In some special cases, such as in cold regions, the surface of aircraft radomes is susceptible to icing and other problems, resulting in a decrease in electromagnetic performance. In addition, icing can also cause changes in the aircraft's aerodynamic shape and affect flight performance. Therefore, it is necessary to design a frequency selective surface with heating function to meet the requirements of anti-icing / de-icing function and wave transmission.

[0003] Currently, the design of heatable frequency selective surfaces faces many challenges. On the one hand, traditional design methods mostly optimize a single objective (such as electromagnetic performance or heating performance), making it difficult to achieve collaborative optimization of multiple objectives. On the other hand, during the optimization process, due to the large number of parameters and their mutual coupling, relying on experience or simple trial and error methods is extremely inefficient and cannot meet actual engineering needs. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention provides a design method for a high-wave-transmittance electrothermal film based on a multi-objective genetic algorithm. This method obtains the design parameters of the high-wave-transmittance electrothermal film, including the area of ​​the design region, material parameters, and thermal diffusivity; establishes multiple rectangular grids to generate energized paths to obtain a frequency-selective surface population; obtains the thermal conductivity and wave-transmittance properties of the surface population; performs non-dominated sorting on the frequency-selective surface population to obtain multiple non-dominated layers; calculates the crowding degree of each individual in each non-dominated layer, and uses a genetic algorithm to generate a parent population based on the crowding degree; performs crossover and mutation operations on the parent population to generate a child population; merges the parent and child populations, and repeats the above steps until a set number of iterations is reached, generating a set of Pareto optimal solutions. This method can solve the problem of obtaining parameter-balanced optimization results during multi-objective optimization, effectively improving design efficiency and quality.

[0005] The present invention adopts the following technical solution, a design method of a high-wave-transmittance electric heating film based on a multi-objective genetic algorithm, comprising: Obtaining design parameters of the high-transmittance electric heating film; the design parameters include the area of ​​the design area, material parameters, and thermal diffusion coefficient; Establishing a plurality of rectangular grids in the design region according to the area of ​​the design region, and obtaining a frequency selective surface population by randomly generating energized paths in the grids; Obtaining the thermal conductivity and wave transmission properties of the surface population according to the material parameters and the thermal diffusion coefficient; performing non-dominated sorting on the frequency selective surface population according to the thermal conductivity and wave transmission performance to obtain a plurality of non-dominated layers; Calculating the crowding degree of each individual in each non-dominated layer, and generating a parent population using a genetic algorithm according to the crowding degree; Perform crossover and mutation operations on the parent population to generate a child population; merge the parent population and the child population, and repeat the above steps until the set number of iterations is reached to generate a set of Pareto optimal solutions.

[0006] Furthermore, the frequency selective surface population is obtained by randomly generating energized paths on the grid, specifically: Establishing a rectangular grid in the design area, selecting any point on the left side of the rectangular grid as a starting point, and randomly generating a path to any point on the right side of the grid to obtain a first energized path; Mirroring the current path along the horizontal symmetry axis where the bottom edge of the rectangular grid is located to obtain a second current path; Connecting the first energized path and the second energized path to obtain an initial surface population of a rectangular grid; The frequency selection surface population of the design area is obtained by permuting and combining the initial surface populations corresponding to the multiple grids in the design area.

[0007] Furthermore, the expression for obtaining the thermal conductivity of the surface population is: in, Indicates the The space coordinates of the iteration The temperature at Indicates the At the iteration time, the spatial coordinate The temperature at is the thermal diffusivity, represents the time step, and are the spatial steps in the x and y directions, represents the number of iteration steps, Indicates the At the iteration time, the spatial coordinate The temperature at Indicates the At the iteration time, the spatial coordinate The temperature at Indicates the At the iteration time, the spatial coordinate The temperature at Indicates the At the iteration time, the spatial coordinate The temperature at which the

[0008] Furthermore, the method for obtaining the wave transmission performance is: Calculate the wave transmission performance using electromagnetic simulation software , expressed as: in, is the transmission coefficient, Indicates taking the absolute value.

[0009] Furthermore, the frequency selective surface population is subjected to non-dominated sorting, specifically: Establishing an objective function based on the thermal conductivity and wave transmission performance of the frequency-selective surface population; The objective function value corresponding to each individual in the frequency selection surface population is non-dominated sorted.

[0010] Furthermore, the individual crowding degree of each non-dominated layer in the frequency selection surface population is calculated, including: Sort the individuals in each non-dominated layer in the surface population according to their objective function, and set the crowding degree of the first and last individuals in each non-dominated layer after sorting to infinity; Calculate the objective function difference between each individual and its adjacent individuals, and add up all the objective function differences corresponding to each individual to obtain the crowding degree of the individual.

[0011] Furthermore, a genetic algorithm is used to generate a parent population according to the individual crowding degree, specifically: A tournament selection strategy is adopted to randomly select a set number of individuals from the frequency selection surface population, and the parent population is formed according to the individuals in the non-dominated layer whose sequence numbers are less than a first threshold and whose crowding degree is greater than a second threshold.

[0012] The beneficial effects of the present invention are as follows: the present invention takes into account both electric heating and frequency selection functions to evaluate the performance of population generation, and further optimizes the two performances through multiple rounds of calculation, sorting, genetic operations and other steps. The final Pareto optimal solution covers a variety of thermal uniformity and wave transmission performance balance solutions. When meeting certain transmittance requirements, it can greatly improve the heat conduction efficiency and can be applied to aircraft radar covers, which can not only ensure signal transmission, but also effectively heat to prevent frost from affecting equipment operation; the present invention adopts random generation of power-on paths and genetic algorithm optimization when generating populations. Compared with traditional trial and error methods and simple optimization algorithms, the design efficiency is significantly improved, and the randomly generated power-on paths can effectively enrich the diversity of the initial population. The genetic algorithm is Non-dominated sorting and congestion are used to calculate and guide selection, crossover, and mutation operations, efficiently exploring the design space. The optimal solution can be obtained after a limited number of iterations, which greatly shortens the design cycle, reduces the number of experiments and simulations, and reduces R&D costs. At the same time, the design method of the present invention is highly flexible, and parameters and iteration times can be adjusted according to different needs to obtain design schemes with different focuses. In communication base stations in cold areas, emphasis can be placed on thermal conductivity to ensure normal operation of equipment at low temperatures. In precision communication equipment with extremely high requirements for signal transmission quality, wave transmission performance can be prioritized, which makes high-wave-transmitting electric heating films widely used in aerospace, communications, electronic equipment and other fields to meet the diverse needs of material performance in different scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0014] Figure 1 This is a flow chart of a method for designing a high-wave-transmittance electric heating film based on a multi-objective genetic algorithm according to an embodiment of the present invention; Figure 2 A schematic diagram of generating an initial surface population of a rectangular grid according to an embodiment of the present invention; Figure 3 A schematic diagram of generating a frequency selective surface population in a design region according to an embodiment of the present invention; Figure 4 Schematic diagram of a group of Pareto optimal solutions according to an embodiment of the present invention. DETAILED DESCRIPTION

[0015] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0016] A flowchart of a design method of a high-transparency electrothermal film based on a multi-objective genetic algorithm according to an embodiment of the present application is shown in FIG. 1, which includes the following steps. Figure 1 Obtaining design parameters of the high-transparency electrothermal film, wherein the design parameters include an area of a design region, material parameters, and a thermal diffusivity. The high-transparency electrothermal film is a special electrothermal film that not only has the function of converting electrical energy into heat energy like ordinary electrothermal films, but also has good wave-transmitting performance, that is, it can allow specific frequency electromagnetic waves to pass through relatively smoothly, reducing reflection and absorption of electromagnetic waves. This characteristic makes it applicable in some scenarios that require electromagnetic wave propagation, such as devices or environments that need to be heated without affecting electromagnetic signal transmission.

[0017] In the embodiment of the present application, the area of the design region refers to the size of the high-transparency electrothermal film region on the plane. The area size will affect the heating power and coverage range of the electrothermal film. The larger the area, the greater the total heating power under the same power density, and the wider the space range that can be heated.

[0018] The material parameters include the physical and chemical property parameters of various materials that constitute the high-transparency electrothermal film, such as the resistivity of the material, which determines the heating efficiency of the electrothermal film when powered on. The higher the resistivity, the more heat generated under the same voltage. The dielectric constant of the material also has an important influence on its wave-transmitting performance. A suitable dielectric constant can ensure good electromagnetic wave transmission rate. In addition, parameters such as the thermal stability and mechanical strength of the material will also affect the service life and performance of the electrothermal film.

[0019] The thermal diffusivity is an important thermal property parameter of the material, which reflects the ability of the material to tend to be uniform in internal temperature during heating or cooling. The greater the thermal diffusivity, the faster the heat propagates in the material, and the easier the temperature distribution tends to be uniform. For the high-transparency electrothermal film, the thermal diffusivity affects its heating uniformity and response speed. A larger thermal diffusivity can make the electrothermal film reach a uniform temperature distribution faster, improving the heating efficiency and effect.

[0020] Establishing multiple rectangular grids according to the area of the design region, and obtaining a frequency selective surface population by randomly generating power-on paths in the grids. ​In an embodiment of the present invention, a rectangular grid is established in a design area. An arbitrary point on the left side of the rectangular grid is selected as a starting point, and a path is randomly generated to an arbitrary point on the right side of the grid to obtain a first energized path. The energized path is mirrored along the horizontal symmetry axis of the bottom edge of the rectangular grid to obtain a second energized path. The first energized path and the second energized path are connected to obtain an initial surface population of the rectangular grid. Specifically, a rectangular grid is established in the design area, and any point on the left side of the rectangular grid is selected as the starting point. A path is randomly generated to any point on the right side of the grid to obtain the first power-on path, which is specifically: In an embodiment of the present invention, an equally spaced rectangular grid coordinate system is established in the design area, and any point on the left boundary of the rectangular grid is selected as the initial starting point. An ant colony optimization algorithm is optionally used to randomly generate a channel path until it reaches any point on the right boundary of the grid, thereby obtaining a first power-on path. The specific process of randomly generating a channel path through the ant colony optimization algorithm can refer to the content disclosed in the prior art. At the same time, the minimum line width constraint and adjacent path spacing restriction conditions must be met during the path generation process to ensure electrical reliability.

[0021] Mirror the power path along the horizontal symmetry axis where the bottom edge of the rectangular grid is located to obtain the second power path, which is: The energized path is mirrored along the horizontal symmetry axis where the bottom edge of the rectangular grid is located, and the sharp corner defects generated by the replication are eliminated through a path smoothing algorithm, and finally a second energized path that is symmetrically distributed with the original path is obtained; the path smoothing algorithm is an algorithm used to process path data, and its purpose is to make the path smoother and more natural. Optional existing motion path planning algorithms, graphics drawing algorithms, etc. in the embodiments of the present invention can be used in the present invention. The originally generated path may be discontinuous or have sudden changes. The path smoothing algorithm can adjust and optimize the points on the path through mathematical methods to make the changes in the path more gentle and symmetrical. At the same time, the impedance continuity needs to be maintained during the replication process, and the electromagnetic compatibility characteristics must be verified.

[0022] The first energized path and the second energized path are connected to obtain the initial surface population of the rectangular grid, specifically: In an embodiment of the present invention, an adaptive connection algorithm is used to connect the upstream port of the first power path with the downstream port of the second power path in three dimensions. The transition curvature of the connection is optimized by a genetic algorithm to form a closed ring topology. This results in an initial surface population of rectangular grids containing multiple path combination schemes. This population will serve as the basic solution set for subsequent iterative optimization and is used for Pareto front screening of surface wiring schemes.

[0023] In a specific embodiment of the present invention, the frequency-selective surface population of the design area is obtained by permuting and combining the initial surface populations corresponding to the multiple grids in the design area. First, the design area is divided into multiple rectangular grids according to the area. In each rectangular grid, a power path is randomly generated with any position on the left as the starting point and extending to any position on the right as the end point, thus obtaining the first power path of the present invention. Subsequently, this path is symmetrically replicated along the bottom edge of the rectangle to obtain a second power path. The two paths are connected to each other to obtain a set of initial surface populations of rectangular grids, such as Figure 2 As shown, the initial surface populations of these rectangular grids are arranged and combined in an orderly manner to form a complete area, that is, the frequency selective surface population of the design area is obtained, as shown in Figure 3 shown.

[0024] Obtain the thermal conductivity and wave transmission properties of the frequency selective surface population based on material parameters and thermal diffusivity; In the embodiment of the present invention, the thermal conductivity and wave transmission performance of the frequency selective surface population are calculated based on the thermal diffusivity and the conductivity parameter in the material parameters, which can be expressed as: in, Indicates the The space coordinates of the iteration The temperature at Indicates the At the iteration time, the spatial coordinate The temperature at is the thermal diffusivity, represents the time step, and are the spatial steps in the x and y directions respectively, represents the number of iteration steps, Indicates the At the iteration time, the spatial coordinate The temperature at Indicates the At the iteration time, the spatial coordinate The temperature at Indicates the At the iteration time, the spatial coordinate The temperature at Indicates the At the iteration time, the spatial coordinate The temperature at which the

[0025] Furthermore, the method for obtaining the wave transmission performance is: Calculate the wave transmission performance using electromagnetic simulation software , expressed as: in, is the transmission coefficient, Indicates taking the absolute value.

[0026] The frequency selective surface population is non-dominated and sorted according to its thermal conductivity and wave transmission performance to obtain multiple non-dominated layers. In the embodiment of the present invention, the non-dominated sorting process is as follows: for two individuals A and B in a frequency selective surface population, if individual A is not inferior to individual B in both thermal conductivity and wave transmission performance, and is superior to individual B in at least one of the objectives, then individual A is said to dominate individual B. Conversely, if individual A and individual B do not dominate each other, that is, individual A is superior to individual B in one objective, while individual B is superior to individual A in another objective, then individuals A and B are said to be non-dominated. After all individuals in the population are compared, the individuals not marked as dominated constitute a first non-dominated layer. These individuals are relatively good at both thermal conductivity and wave transmission performance, and no other individuals can simultaneously outperform them in both objectives. Individuals in the first non-dominated layer are removed from the population, and the steps are repeated for the remaining population to find a second non-dominated layer. This process is repeated until all individuals are assigned to a non-dominated layer, thereby obtaining multiple non-dominated layers.

[0027] Calculating the crowding degree of each individual in each non-dominated layer, and generating a parent population using a genetic algorithm according to the crowding degree; In an embodiment of the present invention, after performing non-dominated sorting on the frequency selective surface population, when the number of populations in the same non-dominated layer exceeds the required number, the crowding weight of each population is calculated based on the crowding degree of all individuals contained in the population. The population with the largest crowding weight is selected, that is, the parent individual is selected to generate the parent population, thereby improving diversity. At the same time, for populations with a large number of connecting nodes between rectangular grids, the selection weight of the number of connected nodes is further calculated. The more connected nodes there are, the higher the selection weight.

[0028] In the embodiment of the present invention, the crowding degree of each individual in each non-dominated layer refers to: for each individual in each non-dominated layer, the sum of the distances between the individual and the adjacent individuals in the two target dimensions of thermal conductivity and wave transmission performance is calculated as the crowding degree of each individual. The crowding degree of a population is equal to the sum of the crowding degrees of all individuals in the population divided by the number of individuals in the population, that is, the mean crowding degree of all individuals in the population. The greater the crowding degree, the more dispersed the distribution of the population in the target space, the higher the diversity, and the higher the selection weight is given to it. Let the crowding degree of the population be , the maximum congestion is , then the congestion weight The calculation method is expressed as: .

[0029] In the embodiment of the present invention, a higher selection weight is given to the population with a large number of connected nodes between rectangular grids. Specifically, the weight coefficient is determined according to the difference between the number of connected nodes and the average number of connected nodes. For example, if the average number of connected nodes is , for the number of connected nodes The population, the weight coefficient of the number of connected nodes , where k is a constant greater than 1, which is used to amplify the effect of the number of connected nodes on the weight.

[0030] In the embodiment of the present invention, the selection weight of the number of connected nodes and the congestion weight are comprehensively considered to obtain the comprehensive weight of each population And all populations in the same non-dominated layer are divided according to the comprehensive weight Sort from large to small, and select from the sorted population in sequence until the number of selected populations reaches the set screening number or ratio.

[0031] Perform crossover and mutation operations on the parent population to generate a child population; merge the parent population and the child population, and repeat the above steps until the set number of iterations is reached to generate a set of Pareto optimal solutions.

[0032] In another specific embodiment of the present invention, when the area of ​​the design area is divided into multiple rectangular grids, the length of the rectangular grid can be set to 100, the height to 50, the path width to 10, and the number of path nodes to 30. On this basis, 80 populations are randomly generated, and the thermal conductivity and wave transmission performance of all populations are calculated; wherein, the wave transmission performance can be calculated by calling the electromagnetic simulation software through the Matlab program, and the path pattern is generated according to the randomly generated population coordinates, and the generated path pattern is symmetrically arranged in an array form, and the dielectric constant of the path pattern material is set to 8, the conductivity is 120S / m, and the material thickness is 0.01mm. The transmission coefficient of the population at the operating frequency of 2-18GHz is calculated, so as to characterize the wave transmission performance; when calculating the thermal conductivity performance, the thermal conductivity pattern is calculated by the finite difference method. The program is discretized and solved, the temperature at the path is set to 80℃, and the temperature of the remaining area is set to -20℃. The temperature change in the rectangular grid after a certain period of time is approximately simulated by numerical calculation, and the thermal conductivity performance is finally judged according to the lowest temperature in the area. After the calculation is completed, the population is non-dominated sorted and the crowding distance is calculated according to the calculation results of the wave transmission performance. According to the results of the sorting and crowding distance, 40 parent populations are selected, and then crossover and mutation operations are performed to generate 20 child populations. In the present invention, the crossover probability is set to 0.9 and the mutation probability is set to 0.15; the child population is merged with the parent population, and the wave transmission performance and thermal conductivity performance of the new population are recalculated to start the next cycle. This cycle is repeated until the number of cycles reaches 100. After the above process, the following will be generated. Figure 4 A series of Pareto optimal solutions are shown. These optimal solutions provide abundant choices for practical applications. The most suitable solution can be flexibly selected according to different usage environments to meet actual needs, thereby realizing the design of high-transmittance electric heating film.

[0033] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A design method for high-wave-transmittance electric heating film based on a multi-objective genetic algorithm, characterized in that: include: Obtaining design parameters of the high-transmittance electric heating film; the design parameters include the area of ​​the design area, material parameters, and thermal diffusion coefficient; Establishing a plurality of rectangular grids in the design region according to the area of ​​the design region, and obtaining a frequency selective surface population by randomly generating energized paths in the grids; Obtaining the thermal conductivity and wave transmission performance of the frequency selective surface population according to the material parameters and the thermal diffusion coefficient; performing non-dominated sorting on the frequency selective surface population according to the thermal conductivity and wave transmission performance to obtain a plurality of non-dominated layers; Calculating the crowding degree of each individual in each non-dominated layer, and generating a parent population using a genetic algorithm according to the crowding degree; Perform crossover and mutation operations on the parent population to generate a child population; merge the parent population and the child population, and repeat the above steps until the set number of iterations is reached to generate a set of Pareto optimal solutions.

2. The method for designing a high-wave-transmittance electric heating film based on a multi-objective genetic algorithm according to claim 1, characterized in that: The frequency selective surface population is obtained by randomly generating energized paths on the grid, specifically: Establishing a rectangular grid in the design area, selecting any point on the left side of the rectangular grid as a starting point, and randomly generating a path to any point on the right side of the grid to obtain a first energized path; Mirroring the current path along the horizontal symmetry axis where the bottom edge of the rectangular grid is located to obtain a second current path; Connecting the first energized path and the second energized path to obtain an initial surface population of a rectangular grid; The frequency selection surface population of the design area is obtained by permuting and combining the initial surface populations corresponding to the multiple grids in the design area.

3. The method for designing a high-wave-transmittance electric heating film based on a multi-objective genetic algorithm according to claim 1, characterized in that: The expression for obtaining the thermal conductivity of the frequency selective surface population is: in, Indicates the The space coordinates of the iteration The temperature at Indicates the At the iteration time, the spatial coordinate The temperature at is the thermal diffusivity, represents the time step, and are the spatial steps in the x and y directions respectively, represents the number of iteration steps, Indicates the At the iteration time, the spatial coordinate The temperature at Indicates the At the iteration time, the spatial coordinate The temperature at Indicates the At the iteration time, the spatial coordinate The temperature at Indicates the At the iteration time, the spatial coordinate The temperature at which the 4. The method for designing a high-wave-transmittance electric heating film based on a multi-objective genetic algorithm according to claim 1, characterized in that: The method for obtaining the wave transmission performance is: Calculate the wave transmission performance using electromagnetic simulation software , expressed as: in, is the transmission coefficient, Indicates taking the absolute value.

5. The method for designing a high-wave-transmittance electric heating film based on a multi-objective genetic algorithm according to claim 1, characterized in that: The frequency selective surface population is non-dominated sorted, specifically: Establishing an objective function based on the thermal conductivity and wave transmission performance of the frequency-selective surface population; The objective function value corresponding to each individual in the frequency selection surface population is non-dominated sorted.

6. The method for designing a high-wave-transmittance electric heating film based on a multi-objective genetic algorithm according to claim 5, characterized in that: Calculate the individual crowding degree of each non-dominated layer in the frequency selection surface population, including: Sort the individuals in each non-dominated layer in the surface population according to their objective function, and set the crowding degree of the first and last individuals in each non-dominated layer after sorting to infinity; Calculate the objective function difference between each individual and its adjacent individuals, and add up all the objective function differences corresponding to each individual to obtain the crowding degree of each individual.

7. The method for designing a high-wave-transmittance electric heating film based on a multi-objective genetic algorithm according to claim 1, characterized in that: Generate the parent population using a genetic algorithm based on the individual crowding degree, specifically: A tournament selection strategy is adopted to randomly select a set number of individuals from the frequency selection surface population, and the parent population is formed according to the individuals in the non-dominated layer whose sequence numbers are less than a first threshold and whose crowding degree is greater than a second threshold.

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