A method for optimizing the design of high-gain thermo-electromagnetic wave-transmitting structures

Abstract

The present invention relates to the field of radar antenna technology and discloses a method for optimizing the design of a high-gain thermoelectromagnetic wave-transmitting structure. The method includes parametric modeling of the thermoelectromagnetic wave-transmitting structure and the radar antenna structure to extract the design variables to be optimized from the geometric parameters. The parametric model is reconstructed based on the design variables, material properties, and service conditions. Based on a sequential coupling simulation method, thermal simulation is first performed, followed by electromagnetic simulation, to perform thermoelectromagnetic coupling analysis on the design domain of the electromagnetic wave-transmitting structure. The actual far-field radiation gain of the radar antenna is calculated. An optimization model is established, and the design variables are iteratively updated using a Gaussian regression model and a genetic algorithm. The optimal values ​​of the design variables are obtained to obtain the optimal electromagnetic wave-transmitting structure. The present invention improves the average far-field radiation gain of the radar antenna in the forward direction, shortens the design cycle of the thermoelectromagnetic wave-transmitting structure, reduces the cost of trial and error, enhances the adaptive cruise control capability of vehicles, reduces product R&D costs, and shortens the development cycle.

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-facing radar in a car's adaptive cruise control system must be installed in the center of the vehicle to detect obstacles directly in front of it. Integrating a forward-facing millimeter-wave radar into the car logo is the industry's mainstream solution. The electromagnetic wave transmission performance of millimeter-wave radar logos is affected by multiple factors, with temperature and external metal obstruction being the two main detrimental factors. On the one hand, to withstand cold weather, heating elements are integrated inside or on the surface of the logo. The temperature field generated by heating affects electromagnetic wave propagation. On the other hand, the electroplated metal layer on the logo's surface and the metal wire in the heating element have the characteristic of absorbing electromagnetic waves, causing significant attenuation of the millimeter waves emitted by the radar. Designing a thermo-electromagnetic wave-transmitting structure that meets both heating performance and high electromagnetic gain requirements for use in automotive forward radars can enhance 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, and structural design and simulation evaluation are carried out by considering heating performance or electromagnetic performance separately. 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 thermoelectromagnetic wave-transmitting structures, which can quickly achieve the optimization design of high-gain thermoelectromagnetic wave-transmitting structures, so as to solve the problems of high trial-and-error costs and low product development efficiency caused by designing thermoelectromagnetic wave-transmitting structures based on engineering experience in the prior art.

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

[0006] Step 1: Parametrically model the thermal electromagnetic wave-transmitting structure and radar antenna structure, and extract the design variables to be optimized from the geometric parameters, including 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 based on 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 heat transfer and electromagnetic coupling, Joule heating generated by 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 perform 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 the iterative design variables for the 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 the vehicle logo with a thermal electromagnetic wave-transmitting structure considering transmission gain.

[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 thermo-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 governing 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 convective 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 range 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 bound of temperature constraint, T2 is the upper bound 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 thermo-electromagnetic wave-transmitting structure optimization design method provided by this invention can automatically iteratively optimize and obtain a high-gain thermo-electromagnetic wave-transmitting structure while ensuring specified heating performance. This method improves the average far-field radiation gain in the forward direction of the radar antenna, shortens the thermo-electromagnetic wave-transmitting structure design cycle, and reduces the cost of trial and error. This method, applied to the design of automotive millimeter-wave radar logos, can improve the vehicle's adaptive cruise control capabilities, reduce product R&D costs, and shorten the development cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a flow chart of a method for optimizing the design of 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 radar antenna with a thermal electromagnetic wave-transmitting structure according to an embodiment of the present invention;

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

[0038] Figure 4 1 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 accompanying drawings to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the scope of protection of the present invention is not limited to the embodiments mentioned herein.

[0040] In the drawings, components with identical structures are denoted by the same reference numerals, and components with similar structures or functions are denoted by similar reference numerals. The size and thickness of each component shown in the drawings are arbitrary and are not limited by the present invention. For clarity, the thickness of components in some places in the drawings is appropriately exaggerated.

[0041] refer to Figures 1 to 4 One embodiment of the present invention discloses a method for optimizing the design of a high-gain thermo-electromagnetic wave-transmitting structure. It proposes a method for simulating structural performance under thermo-electromagnetic coupling conditions, enabling efficient prediction of both heating and electromagnetic performance. A structural parameter optimization model is established, and structural parameters are iteratively optimized using a Gaussian regression model and a genetic algorithm to obtain optimal structural characteristic parameters. Specifically, the method 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 from the geometric parameters x = (x1, x2, ..., x n ), 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 conducted 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. Metal wires are distributed within the thermal electromagnetic wave-transmitting structure, and the vehicle logo and the outside air exchange heat through 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 vehicle 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 can 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 radar antenna structure. These material properties include parameters such as electrical conductivity, permittivity, magnetic permeability, specific heat capacity, density, and heat transfer coefficient. In a preferred embodiment, the metal wire is copper, the vehicle logo of the thermal electromagnetic wave-transmitting structure is made of PC and AES, and the radar antenna is made of a 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. These service conditions include those for the radar antenna structure and the thermal electromagnetic wave-transmitting structure. The radar antenna structure specifies the antenna's excitation port, excitation frequency, and ideal conductor surface. The thermal electromagnetic wave-transmitting structure specifies the heat exchange conditions with the environment 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 environment are natural convection, the external 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 wires, 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 heating generated by the current also needs to be considered.

[0048] In a preferred embodiment of the present invention, the governing 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 convective heat transfer coefficient.

[0051] In the case of coupling between heat transfer and electromagnetics, it is also necessary to consider the Joule heating generated by the current. Combined with Maxwell's equations, the calculation formula for Joule heating 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 electrical 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 perform 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. Finite element simulation is used to solve the structure inside, and integral equations are used to solve the structure boundaries:

[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 range 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 bound of temperature constraint, T2 is the upper bound 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 objective is the far-field radiation gain directly in front of the radar antenna, and the constraints are the upper and lower limits of the vehicle logo's heating temperature for the thermo-electromagnetic wave-transmitting structure and the design variable values. In this embodiment, the upper and lower limits of the vehicle logo's heating temperature for the thermo-electromagnetic wave-transmitting structure are 330K and 340K, respectively.

[0068] Step 9: Determine whether convergence conditions are met: If the change in the design variable before and after the update iteration is less than a given threshold and the constraint conditions are met, if the convergence conditions are not met, the design variable is not optimal, and the process goes to Step 4; otherwise, the design variable is optimal, and the process goes 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 the thermal electromagnetic wave-transmitting structure considering the transmission gain. Figure 4 As shown, in a preferred embodiment of the present invention, it has been verified that the optimized design of the millimeter-wave radar transmission gain 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 proposed method for optimizing the design of thermoelectromagnetic wave-transmitting structures, taking thermoelectromagnetic performance into account, can automatically iteratively optimize and obtain a high-gain thermoelectromagnetic wave-transmitting structure while ensuring specified heating performance. This method improves the average far-field radiation gain in the forward direction of the radar antenna, shortens the design cycle, and reduces the cost of trial and error. This high-gain thermoelectromagnetic wave-transmitting structure optimization method, when applied to the design of automotive millimeter-wave radar logos, can enhance the vehicle's adaptive cruise control capabilities, reduce product R&D costs, and shorten the development cycle.

[0071] The preferred embodiments of the present invention have been described in detail above. It should be understood that numerous modifications and variations based on the concepts of the present invention are possible without inventive effort by those skilled in the art. Therefore, any technical solution that can be derived by one skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A high-gain thermo-electromagnetic wave-transmitting structure optimization design method, characterized in that: The steps include: Step 1: Parametrically model the thermal electromagnetic wave-transmitting structure and radar antenna structure, and extract the design variables to be optimized from the geometric parameters, including 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 based on 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 heat transfer and electromagnetic coupling, Joule heating generated by 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 perform 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 the iterative design variables for the 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 the vehicle logo with a thermal electromagnetic wave-transmitting structure considering transmission gain.

2. The high-gain thermo-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 thermo-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 thermo-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 thermo-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 thermo-electromagnetic wave-transmitting structure optimization design method according to claim 5, characterized in that: The governing equation for the thermal analysis 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 the power density of the body heat source, q c is the heat flux density, and h is the convective heat transfer coefficient.

7. The high-gain thermo-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: Where 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 thermo-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, using the following formula: 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 range in the spherical coordinate system, respectively.

9. The high-gain thermo-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 bound of temperature constraint, T2 is the upper bound 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 thermo-electromagnetic wave-transmitting structure optimization design method according to claim 1, characterized in that: The design variable change threshold is set to 0.01.

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