Optimization design method of high-gain thermal electromagnetic wave-transparent structure

Abstract

The invention relates to the technical field of radar antennas, and discloses a high-gain thermal electromagnetic wave-transparent structure optimization design method, which comprises the following steps: performing parametric modeling on a thermal electromagnetic wave-transparent structure and a radar antenna structure, and extracting design variables to be optimized in geometric parameters; according to the design variables, the material attributes and the service conditions, a parameterized model is reconstructed; based on a sequential coupling simulation method, firstly performing thermal simulation, then performing electromagnetic simulation, and performing thermal electromagnetic coupling analysis on the design domain of the electromagnetic wave-transparent structure; calculating the actual far-field radiation gain of the radar antenna; establishing an optimization model, and updating iterative design variables by using a Gaussian regression model and a genetic algorithm; the optimal value of the design variable is obtained, and the optimal electromagnetic wave-transparent structure is obtained. The far-field radiation average gain in the positive direction of the radar antenna is improved, the design period of the thermal electromagnetic wave-transparent structure is shortened, the repeated trial and error cost is reduced, the self-adaptive cruise capability of an automobile is improved, the product research and development cost is reduced, and the development period is shortened.

Description

Technical Field

[0001] The present invention relates to the technical field of radar antennas, and in particular to an optimization design method for a high-gain thermal electromagnetic wave-transmitting structure. Background Art

[0002] The forward radar in the car's adaptive cruise control system needs to be installed in the middle of the vehicle due to the requirement to detect obstacles directly in front of the vehicle. Integrating a forward millimeter-wave radar in the car logo is the mainstream solution in the industry. The electromagnetic wave transmission performance of the millimeter-wave radar logo is affected by many factors, and temperature and external metal shielding are the two main unfavorable factors. On the one hand, in order to resist the cold climate, heating elements are integrated inside or on the surface of the car logo, and the temperature field generated by heating will affect the propagation of electromagnetic waves; on the other hand, the electroplated metal layer on the surface of the car logo and the metal wire in the heating element have the characteristics of absorbing electromagnetic waves, causing the millimeter waves emitted by the radar to be severely attenuated. Designing a thermal electromagnetic wave-transmitting structure that can meet both heating performance and high electromagnetic gain requirements for use in automotive forward radars can improve the vehicle's adaptive cruise capability.

[0003] In actual engineering, the existing design methods of thermal electromagnetic wave-transmitting structures are mainly based on engineering experience. Structural design and simulation evaluation are carried out by considering heating performance or electromagnetic performance alone. The thermal electromagnetic wave-transmitting structures that meet the requirements are obtained through continuous iterative optimization. The design cycle is long and the cost is high. Summary of the invention

[0004] In view of the above-mentioned problems in the prior art, the technical problem to be solved by the present invention is how to design an automatic optimization design method for a thermal electromagnetic wave-transmitting structure, which can quickly realize the optimization design of a high-gain thermal electromagnetic wave-transmitting structure, so as to solve the problem of high trial-and-error cost and low product development efficiency caused by designing a thermal electromagnetic wave-transmitting structure through engineering experience in the prior art.

[0005] To achieve the above object, the present invention provides a method for optimizing the design of a high-gain thermal electromagnetic wave-transmitting structure, comprising the following steps:

[0006] Step 1: parametrically modeling the thermal electromagnetic wave-transmitting structure and the radar antenna structure, and extracting the design variables to be optimized in the geometric parameters, wherein the design variables include the thickness of the wave-transmitting cover structure, the size of the metal wire, and the antenna distance;

[0007] Step 2: Setting the material properties of the thermal electromagnetic wave-transmitting structure and the radar antenna structure;

[0008] Step 3: Setting the service conditions of the thermal electromagnetic wave-transmitting structure and the radar antenna structure;

[0009] Step 4: Reconstruct the parameterized model according to the design variables, material properties and service conditions, and divide the thermal electromagnetic wave-transmitting structure and radar antenna structure unit grids;

[0010] Step 5: Based on the sequential coupling simulation method, a thermal-electromagnetic coupling analysis is performed on the design domain of the electromagnetic wave-transmitting structure. First, a thermal analysis is performed. For the case of coupling between heat transfer and electromagnetics, the Joule heat generated by the current also needs to be considered.

[0011] Step 6: Based on step 5, obtain the temperature-related material dielectric constant based on the temperature field obtained by thermal analysis, and carry out electromagnetic simulation;

[0012] Step 7: Calculate the actual far-field radiation gain of the radar antenna;

[0013] Step 8: Establish an optimization model, and use Gaussian regression model and genetic algorithm to update iterative design variables for optimization parameters;

[0014] Step 9: Determine whether the convergence condition is met: if the change value of the design variable before and after the update iteration is less than the given design variable change threshold and the constraint condition is met, if the convergence condition is not met, the design variable is not the optimal value, and go to step 4; otherwise, the design variable is the optimal value, and go to step 10;

[0015] Step 10: Obtain the optimal electromagnetic wave-transmitting structure, output the electromagnetic wave-transmitting structure, and generate an optimized design of a vehicle logo with a thermal electromagnetic wave-transmitting structure that takes transmission gain into consideration.

[0016] In a preferred embodiment of the present invention, the thermal electromagnetic wave-transmitting structure is located in the positive radiation direction of the radar antenna, and metal wires are distributed inside the thermal electromagnetic wave-transmitting structure.

[0017] In a preferred embodiment of the present invention, the material properties include electrical conductivity, permittivity, magnetic permeability, specific heat capacity, density, and heat transfer coefficient of the material.

[0018] In a preferred embodiment of the present invention, the metal wire material is copper, the vehicle logo of the thermal electromagnetic wave-transmitting structure is made of PC and AES, and the radar antenna material is made of copper and ceramic-filled PTFE composite material.

[0019] In a preferred embodiment of the present invention, the service conditions include the service conditions of the radar antenna structure and the service conditions of the thermal electromagnetic wave-transmitting structure. The service conditions of the radar antenna structure specify the excitation port, excitation frequency and ideal conductor surface of the antenna; the service conditions of the thermal electromagnetic wave-transmitting structure specify the heat exchange conditions with the outside world and the heating voltage of the internal heating element.

[0020] In a preferred embodiment of the present invention, the control equation of the thermal analysis in step 5 is:

[0021]

[0022] Where ρ is density, c is specific heat capacity, k is thermal conductivity, T is temperature, T0 is initial temperature, Q is body heat source power density, and h is convection heat transfer coefficient.

[0023] In a preferred embodiment of the present invention, in the electromagnetic simulation in step 6, the propagation equation of electromagnetic waves in space satisfies the wave equation:

[0024]

[0025] Where μ(T) is the magnetic permeability of the medium, ε(T) is the permittivity of the medium, T is the medium temperature, and E is the electric field strength.

[0026] In a preferred embodiment of the present invention, the actual far-field radiation gain of the radar antenna is calculated in step 7 according to the following formula:

[0027]

[0028] in, is the radiated power density, P rad is the total radiated power of the radar antenna, is the directivity of the radar antenna, P in is the total input power to the radar antenna, η is the radar antenna efficiency, is the actual far-field radiation gain of the radar antenna, and φ, θ, and r are the azimuth, elevation, and distance in the spherical coordinate system, respectively.

[0029] In a preferred embodiment of the present invention, the optimization model in step 8 is:

[0030]

[0031] Among them, T1 is the lower limit of temperature constraint, T2 is the upper limit of temperature constraint, x e is the model geometric parameter, and the subscripts e1 and e2 represent the lower and upper bounds of the parameter.

[0032] In a preferred embodiment of the present invention, the design variable change threshold is 0.01.

[0033] Technical effects of the present invention:

[0034] The high-gain thermal electromagnetic wave-transmitting structure optimization design method provided by the present invention can automatically iterate and optimize to obtain a high-gain thermal electromagnetic wave-transmitting structure under the premise of ensuring the specified heating performance, thereby improving the average gain of far-field radiation in the positive direction of the radar antenna, shortening the design cycle of the thermal electromagnetic wave-transmitting structure, and reducing the cost of repeated trial and error. This method is applied to the design of automotive millimeter-wave radar logos, which can improve the automotive adaptive cruise capability, reduce product R&D costs, and shorten the development cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a flow chart of a method for optimizing a high-gain thermal electromagnetic wave-transmitting structure according to an embodiment of the present invention;

[0036] Figure 2 Schematic diagram of the transmission problem of the thermal electromagnetic wave-transmitting structure radar antenna according to an embodiment of the present invention;

[0037] Figure 3 is a schematic diagram of metal wire path planning in parametric modeling in an embodiment of the present invention;

[0038] Figure 4 is a schematic diagram comparing the initial design and the optimized design of an embodiment of the present invention; DETAILED DESCRIPTION

[0039] The following describes several preferred embodiments of the present invention with reference to the drawings in the specification, so that the technical content is clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the protection scope of the present invention is not limited to the embodiments mentioned in the text.

[0040] In the drawings, components with the same structure are indicated by the same numerical reference numerals, and components with similar structures or functions are indicated by similar numerical reference numerals. The size and thickness of each component shown in the drawings are arbitrarily shown, and the present invention does not limit the size and thickness of each component. In order to make the illustration clearer, the thickness of the components is appropriately exaggerated in some places in the drawings.

[0041] refer to Figure 1 to Figure 4 An embodiment of the present invention discloses a high-gain thermal electromagnetic wave-transmitting structure optimization design method, proposes a structural performance simulation method under thermal electromagnetic coupling conditions, and realizes efficient prediction of heating performance and electromagnetic performance; establishes a structural parameter optimization model, and iteratively optimizes the structural parameters through Gaussian regression model and genetic algorithm to obtain the optimal structural characteristic parameters. Specifically, it includes the following steps:

[0042] Step 1: Parametrically model the thermal electromagnetic wave-transmitting structure and the radar antenna structure, and extract the design variables to be optimized in the geometric parameters x = (x1, x2, ..., x n ), wherein the design variables include the thickness of the wave-transparent cover structure, the size of the metal wire, and the antenna distance.

[0043] like Figure 2As shown, in a preferred embodiment of the present invention, an analysis is carried out on the antenna transmission problem of a given thermal electromagnetic wave-transmitting structure. The thermal electromagnetic wave-transmitting structure is located in the positive radiation direction of the radar antenna, and metal wires are distributed inside the thermal electromagnetic wave-transmitting structure. The car logo and the outside air exchange heat by natural convection. Preferably, the metal wire geometry is simplified to a square cross-section with a side length of 0.07 mm, and the distance between the radar antenna and the car logo is 30 mm. The spacing of the metal wires is used as the design variable x in this example. In other embodiments, the design variable may also be the thickness of the wave-transmitting cover structure and / or the antenna distance.

[0044] Step 2: Set the material properties of the thermal electromagnetic wave-transmitting structure and the radar antenna structure. The material properties include parameters such as the material's electrical conductivity, permittivity, magnetic permeability, specific heat capacity, density, and heat transfer coefficient. In a preferred embodiment, the metal wire material is copper, the vehicle logo of the thermal electromagnetic wave-transmitting structure is made of PC and AES, and the radar antenna material is made of copper and ceramic-filled PTFE composite material.

[0045] Step 3: Set the service conditions of the thermal electromagnetic wave-transmitting structure and the radar antenna structure; the service conditions include the service conditions of the radar antenna structure and the service conditions of the thermal electromagnetic wave-transmitting structure. The service conditions of the radar antenna structure specify the excitation port, excitation frequency and ideal electrical conductor surface of the antenna. The service conditions of the thermal electromagnetic wave-transmitting structure specify the heat exchange conditions with the outside world and the heating voltage of the internal heating element. In a preferred embodiment, the heat exchange conditions between the thermal electromagnetic wave-transmitting structure and the outside world are natural convection heat exchange, the outside temperature is 0°C, and the heating voltage of the internal heating element is 10V.

[0046] Step 4: Reconstruct the parameterized model according to the design variables, material properties and service conditions, and divide the thermal electromagnetic wave-transmitting structure and radar antenna structure unit grids; Figure 3 As shown, in a preferred embodiment of the present invention, a new wire path is planned using a path planning algorithm for the spacing parameter x of the wire, and a parameterized model is reconstructed and a structural grid is divided.

[0047] Step 5: Based on the sequential coupling simulation method, a thermal-electromagnetic coupling analysis is performed on the design domain of the thermal-electromagnetic wave-transmitting structure. First, a thermal analysis is performed. For the case of coupling between heat transfer and electromagnetics, the Joule heat generated by the current also needs to be considered.

[0048] In a preferred embodiment of the present invention, the control equation of the thermal analysis is:

[0049]

[0050] Where ρ is density, c is specific heat capacity, k is thermal conductivity, T is temperature, T0 is initial temperature, Q is body heat source power density, and h is convection heat transfer coefficient.

[0051] In the case of coupling between heat transfer and electromagnetics, it is also necessary to consider the Joule heat generated by the current. Combined with Maxwell's equations, the calculation formula for Joule heat is as follows:

[0052]

[0053] where q j is the Joule heat power density generated by the current, φ is the electric potential in space, and σ is the conductivity of the material.

[0054] Step 6: Based on step 5, obtain the temperature-related material dielectric constant based on the temperature field obtained by thermal analysis and carry out electromagnetic simulation.

[0055] In a preferred embodiment of the present invention, the propagation of electromagnetic waves in space satisfies the wave equation:

[0056]

[0057] Where μ(T) is the magnetic permeability of the medium, ε(T) is the permittivity of the medium, T is the medium temperature, and E is the electric field strength.

[0058] Electromagnetic field simulation uses the finite element-boundary integral hybrid algorithm (FE-BI algorithm) instead of the finite element method. Among them, the finite element simulation is used to solve the structure inside, and the integral equation is used to solve the structure boundary:

[0059]

[0060] Step 7: Calculate the actual far-field radiation gain of the radar antenna.

[0061] In a preferred embodiment of the present invention, the actual far-field radiation gain of the radar antenna is calculated according to the following formula:

[0062]

[0063] in is the radiated power density, P rad is the total radiated power of the radar antenna, is the directivity of the radar antenna, P in is the total input power to the radar antenna, η is the radar antenna efficiency, is the actual far-field radiation gain of the radar antenna, and φ, θ, and r are the azimuth, elevation, and distance in the spherical coordinate system, respectively.

[0064] Step 8: Establish an optimization model, and use a Gaussian regression model and a genetic algorithm to iteratively update the design variables for the optimization parameters; in a preferred embodiment of the present invention, the optimization model is as follows:

[0065]

[0066] Among them, T1 is the lower limit of temperature constraint, T2 is the upper limit of temperature constraint, x e is the model geometric parameter, and the subscripts e1 and e2 represent the lower and upper bounds of the parameter.

[0067] The optimization target is the far-field radiation gain in front of the radar antenna, and the constraints are the upper and lower limits of the vehicle logo heating temperature of the thermal electromagnetic wave-transmitting structure and the design variable value constraints. In this embodiment, the upper and lower limits of the vehicle logo heating temperature of the thermal electromagnetic wave-transmitting structure are 330K and 340K respectively.

[0068] Step 9: Determine whether the convergence condition is met: if the change value of the design variable before and after the update iteration is less than the given threshold and the constraint condition is met, if the convergence condition is not met, the design variable is not the optimal value, and go to step 4; otherwise, the design variable is the optimal value, and go to step 10. In a preferred embodiment of the present invention, the design variable change threshold is 0.01.

[0069] Step 10: Get the optimal structure and output the structure to generate the optimal design of the car logo with thermal electromagnetic wave-transmitting structure considering transmission gain. Figure 4 As shown, in a preferred embodiment of the present invention, it has been verified that the transmission gain of the optimized millimeter-wave radar is increased from 12.5dBi to 15.8dBi, and the surface temperature is 338K when powered on for heating, which meets the defrosting requirements.

[0070] The method for optimizing the design of a thermal electromagnetic wave-transmitting structure taking into account the thermal electromagnetic performance provided by the present invention can automatically iterate and optimize to obtain a high-gain thermal electromagnetic wave-transmitting structure under the premise of ensuring the specified heating performance, thereby improving the average gain of far-field radiation in the positive direction of the radar antenna, shortening the design cycle of the thermal electromagnetic wave-transmitting structure, and reducing the cost of repeated trial and error. The method for optimizing the design of a high-gain thermal electromagnetic wave-transmitting structure is applied to the design of automotive millimeter-wave radar logos, which can improve the automotive adaptive cruise capability, reduce product research and development costs, and shorten the development cycle.

[0071] The preferred specific embodiments of the present invention are described in detail above. It should be understood that ordinary technicians in the field can make many modifications and changes based on the concept of the present invention without creative work. Therefore, all technical solutions that can be obtained by technicians in the technical field based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A high-gain thermal electromagnetic wave-transmitting structure optimization design method, characterized in that: The steps include: Step 1: parametrically modeling the thermal electromagnetic wave-transmitting structure and the radar antenna structure, and extracting the design variables to be optimized in the geometric parameters, wherein the design variables include the thickness of the wave-transmitting cover structure, the size of the metal wire, and the antenna distance; Step 2: Setting the material properties of the thermal electromagnetic wave-transmitting structure and the radar antenna structure; Step 3: Setting the service conditions of the thermal electromagnetic wave-transmitting structure and the radar antenna structure; Step 4: Reconstruct the parameterized model according to the design variables, material properties and service conditions, and divide the thermal electromagnetic wave-transmitting structure and radar antenna structure unit grids; Step 5: Based on the sequential coupling simulation method, a thermal-electromagnetic coupling analysis is performed on the design domain of the electromagnetic wave-transmitting structure. First, a thermal analysis is performed. For the case of coupling between heat transfer and electromagnetics, the Joule heat generated by the current also needs to be considered. Step 6: Based on step 5, obtain the temperature-related material dielectric constant based on the temperature field obtained by thermal analysis, and carry out electromagnetic simulation; Step 7: Calculate the actual far-field radiation gain of the radar antenna; Step 8: Establish an optimization model, and use Gaussian regression model and genetic algorithm to update iterative design variables for optimization parameters; Step 9: Determine whether the convergence condition is met: the change value of the design variable before and after the update iteration is less than the given design variable change threshold and the constraint condition is met. If the convergence condition is not met, the design variable is not the optimal value, and go to step 4; Otherwise, the design variable is the optimal value, and go to step 10; Step 10: Obtain the optimal electromagnetic wave-transmitting structure, output the electromagnetic wave-transmitting structure, and generate an optimized design of a vehicle logo with a thermal electromagnetic wave-transmitting structure that takes transmission gain into consideration.

2. The high-gain thermal electromagnetic wave-transmitting structure optimization design method according to claim 1, characterized in that: The thermal electromagnetic wave-transmitting structure is located in the positive radiation direction of the radar antenna, and metal wires are distributed inside the thermal electromagnetic wave-transmitting structure.

3. The high-gain thermal electromagnetic wave-transmitting structure optimization design method according to claim 1, characterized in that: The material properties include the material's electrical conductivity, permittivity, magnetic permeability, specific heat capacity, density, and heat transfer coefficient.

4. The high-gain thermal electromagnetic wave-transmitting structure optimization design method according to claim 1, characterized in that: The metal wire material is copper, the vehicle logo of the thermal electromagnetic wave-transmitting structure is made of PC and AES, and the radar antenna material is made of copper and ceramic-filled PTFE composite material.

5. The high-gain thermal electromagnetic wave-transmitting structure optimization design method according to claim 1, characterized in that: The service conditions include the service conditions of the radar antenna structure and the service conditions of the thermal electromagnetic wave-transmitting structure. The service conditions of the radar antenna structure specify the excitation port, excitation frequency and ideal conductor surface of the antenna; the service conditions of the thermal electromagnetic wave-transmitting structure specify the heat exchange conditions with the outside world and the heating voltage of the internal heating element.

6. The high-gain thermal electromagnetic wave-transmitting structure optimization design method according to claim 5, characterized in that: The governing equation for the thermal analysis described in step 5 is: Where ρ is density, c is specific heat capacity, k is thermal conductivity, T is temperature, T0 is initial temperature, Q is body heat source power density, q c is the heat flux density and h is the convective heat transfer coefficient.

7. The high-gain thermal electromagnetic wave-transmitting structure optimization design method according to claim 6, characterized in that: In the electromagnetic simulation described in step 6, the propagation equation of electromagnetic waves in space satisfies the wave equation: Among them, μ(T) is the magnetic permeability of the medium, ε(T) is the permittivity of the medium, T is the medium temperature, E is the electric field strength, and H is the magnetic field strength.

8. The high-gain thermal electromagnetic wave-transmitting structure optimization design method according to claim 7, characterized in that: The actual far-field radiation gain of the radar antenna is calculated as described in step 7, and is calculated as follows: in, is the radiated power density, P rad is the total radiated power of the radar antenna, is the directivity of the radar antenna, P in is the total input power to the radar antenna, η is the radar antenna efficiency, is the actual far-field radiation gain of the radar antenna, and φ, θ, and r are the azimuth, elevation, and distance in the spherical coordinate system, respectively.

9. The high-gain thermal electromagnetic wave-transmitting structure optimization design method according to claim 8, characterized in that: The optimization model described in step 8 is: stT<T2 T>T1 x e ∈[x e1 ,x e2 ],e=1,2,...,n Among them, T1 is the lower limit of temperature constraint, T2 is the upper limit of temperature constraint, x e is the model geometric parameter, and the subscripts e1 and e2 represent the lower and upper bounds of the parameter.

10. The high-gain thermal electromagnetic wave-transmitting structure optimization design method according to claim 1, characterized in that: The design variable change threshold is 0.01.

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