Vehicle-mounted speed measurement method and device applied to vehicle-mounted portable mobile warning screen

Abstract

The invention relates to the technical field of radar speed measurement, in particular to a vehicle-mounted speed measurement method and device applied to a vehicle-mounted portable mobile warning screen, and the method comprises the steps: carrying out the modal decomposition of a reflected wave signal of each driving vehicle, and analyzing the amplitude distribution at all frequencies in a spectrogram of each modal component and the proportion of the maximum amplitude, thereby obtaining a vehicle-mounted speed measurement result; determining a first frequency characteristic value; and determining a reflected wave characteristic value by analyzing the difference of the main frequency between each modal component and the microwave radio frequency signal and combining the first characteristic value of the frequency so as to obtain a reconstructed reflected wave signal of each running vehicle, and measuring the vehicle-mounted speed of each running vehicle by combining the microwave radio frequency signal of each running vehicle. According to the invention, clutter components in the reflected wave signals are filtered out, and the speed measurement precision of the microwave radar is improved.

Description

Technical Field

[0001] This application relates to the technical field of radar speed measurement, and particularly to a vehicle speed measurement method and device applied to a vehicle-mounted portable mobile warning screen. Background Art

[0002] A vehicle-mounted portable mobile warning screen with a vehicle speed measurement function is a traffic management device that integrates speed measurement and warning functions. It can be quickly deployed to sections where temporary traffic control is required due to traffic accidents, road construction, etc. By using a microwave radar to measure the driving speed of passing vehicles, when a vehicle is speeding, the warning screen will remind the driver to slow down to avoid traffic congestion and accidents.

[0003] During the actual speed measurement process of a microwave radar, its speed measurement result will be affected by the external environment and itself, resulting in errors. To improve the accuracy of microwave radar speed measurement, an automatic gain control technology is usually used to gain the signal received by the microwave radar. By adding a digital gain automatic adjustment link in the signal processing process of radar speed measurement, the amplitude of the Doppler signal generated by the radar is ensured to be relatively stable, so as to reduce the measurement error caused by the lobe angle of the radar microwave antenna. However, this method ignores the clutter components introduced in the reflected wave signal received by the radar, making the clutter components amplified in the digital gain automatic adjustment link, and reducing the accuracy of microwave radar speed measurement. Summary of the Invention

[0004] To solve the above technical problems, the purpose of this application is to provide a vehicle speed measurement method and device applied to a vehicle-mounted portable mobile warning screen, and the specific technical solutions adopted are as follows: In the first aspect, an embodiment of this application provides a vehicle speed measurement method applied to a vehicle-mounted portable mobile warning screen, and this method includes the following steps: Obtain the microwave radio frequency signals emitted by a microwave radar speedometer to each vehicle driving on the road and the reflected wave signals received from each vehicle driving; Perform modal decomposition on the reflected wave signals of each vehicle driving. By analyzing the amplitude distribution at all frequencies in the spectrogram of each modal component, the frequency characteristic value of each modal component is determined; by analyzing the proportion of the maximum amplitude in the spectrogram of each modal component, the amplitude ratio of each modal component is determined, and in combination with the frequency characteristic value, the first frequency characteristic value of each modal component is determined; By analyzing the difference in the main frequencies between each modal component and the microwave radio frequency signal, the frequency difference of each modal component is determined to determine the second frequency characteristic value of each modal component; based on the first frequency characteristic value and the second frequency characteristic value, the reflected wave characteristic value of each modal component is determined to screen out the characteristic components from all modal components of the reflected wave signal, and the reconstructed reflected wave signals of each vehicle driving are obtained; Measure the vehicle speeds of each moving vehicle based on the microwave radio frequency signals and the reconstructed reflected wave signals of each moving vehicle.

[0005] Preferably, the method for determining the frequency eigenvalue of each modal component is as follows: Count the number of frequencies with amplitudes greater than 0 in the spectrogram of each modal component, which is denoted as the number of positive amplitude frequencies. Normalize the number of positive amplitude frequencies of all modal components, and use the normalized value of the number of positive amplitude frequencies of each modal component as the frequency eigenvalue of each modal component.

[0006] Preferably, the amplitude ratio of each modal component is the result of taking the normalized value of the ratio of the maximum amplitude in the spectrogram of each modal component to the sum of all amplitudes.

[0007] Preferably, the first frequency eigenvalue of each modal component is the ratio of the amplitude ratio of each modal component to the frequency eigenvalue.

[0008] Preferably, the frequency difference of each modal component is the absolute value of the difference between the main frequencies of each modal component and the microwave radio frequency signal.

[0009] Preferably, the expression for the second frequency eigenvalue of each modal component is: ; where represents the second frequency eigenvalue of modal component i; represents the frequency difference of modal component i; exp( ) represents the exponential function with the natural constant as the base.

[0010] Preferably, the reflected wave eigenvalue of each modal component is the result of dividing the normalized value of the first frequency eigenvalue of each modal component by the normalized value of the second frequency eigenvalue.

[0011] Preferably, the process of screening out the characteristic components from all modal components of the reflected wave signal to obtain the reconstructed reflected wave signal of each moving vehicle includes: Use the reflected wave eigenvalues of all modal components in the reflected wave signal as the input of the threshold segmentation algorithm, output the segmentation threshold, mark all modal components with reflected wave eigenvalues greater than the segmentation threshold as characteristic components, and reconstruct all characteristic components to obtain the reconstructed reflected wave signal.

[0012] Preferably, the measurement of the vehicle speed of each moving vehicle includes: Mix the microwave radio frequency signal and the reconstructed reflected wave signal of each moving vehicle to obtain a mixed signal, perform filtering processing on the mixed signal, extract the Doppler signal from the filtered mixed signal, and calculate the speed of each moving vehicle using the Doppler signal.

[0013] In a second aspect, an embodiment of the present application further provides a vehicle speed measurement device for an in-vehicle portable mobile warning screen, including a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, the steps of the vehicle speed measurement method for an in-vehicle portable mobile warning screen described in any one of the above are implemented.

[0014] The present application has at least the following beneficial effects: By performing modal decomposition on the reflected wave signals of each moving vehicle, analyzing the amplitude distribution at all frequencies in the spectrogram of each modal component and the proportion of the maximum amplitude, the present application constructs a first eigenvalue of frequency, which can effectively distinguish each echo formed by the vehicle approaching or leaving the radar coverage area and clutter components such as cloud and rain clutter in the reflected wave signals received by the microwave radar speedometer, and thus can effectively filter out the cloud and rain clutter components in the reflected wave signals; further, by analyzing the difference in the main frequencies between each modal component and the microwave radio frequency signal, the present application constructs a second eigenvalue of frequency for each modal component, and combines the first eigenvalue of frequency to determine the reflected wave eigenvalue, so as to screen out the characteristic components from all modal components of the reflected wave signal and obtain the reconstructed reflected wave signals of each moving vehicle, which can effectively filter out the signal components corresponding to clutter components such as ground clutter and cloud and rain clutter in the reflected wave signals; by automatically gaining the Doppler signals generated from the reconstructed reflected wave signals, the present application can ensure that the amplitude in the Doppler signals generated by the microwave radar speedometer is relatively stable, and at the same time avoid the situation where the signal components corresponding to clutter components such as ground clutter and cloud and rain clutter in the Doppler signals are also amplified by digital gain automatic adjustment, thereby improving the accuracy of the microwave radar speed measurement results. Description of the Drawings

[0015] To more clearly illustrate the technical solutions and advantages in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0016] Figure 1 It is a flowchart of the steps of a vehicle speed measurement method for an in-vehicle portable mobile warning screen provided by an embodiment of the present application; Figure 2 It is a schematic diagram of the process of extracting the reflected wave eigenvalue provided by an embodiment of the present application. Detailed Embodiments

[0017] To further elaborate on the technical means and effects adopted by this application to achieve the intended invention purpose, the following will, in conjunction with the accompanying drawings and preferred embodiments, detail the specific implementation manners, structures, features, and effects of the vehicle speed measurement method and device applied to the in-vehicle portable mobile warning screen proposed according to this application. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. In addition, the specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs.

[0019] The following will specifically describe the specific solutions of the vehicle speed measurement method and device applied to the in-vehicle portable mobile warning screen provided by this application in conjunction with the accompanying drawings.

[0020] Please refer to Figure 1 , which shows the step flow chart of the vehicle speed measurement method applied to the in-vehicle portable mobile warning screen provided by one embodiment of this application. The method includes the following steps: Step S1: Obtain the microwave radio frequency signals transmitted by the microwave radar speedometer to each moving vehicle on the road and the reflected wave signals received from each moving vehicle.

[0021] The in-vehicle portable mobile warning screen with vehicle speed measurement function is a traffic management device integrating speed measurement and warning functions. It can be quickly deployed to sections that require temporary traffic control due to traffic accidents, road construction, etc. By using a microwave radar to measure the driving speed of passing vehicles, when a vehicle is speeding, the warning screen will remind the driver to slow down to avoid traffic congestion and accidents.

[0022] Therefore, in this embodiment, by obtaining the microwave radio frequency signals transmitted by the microwave radar speedometer to each moving vehicle on the road and the reflected wave signals received by the microwave radar speedometer from each moving vehicle, the vehicle speed of the moving vehicle is measured.

[0023] Step S2: Perform modal decomposition on the reflected wave signals of each moving vehicle. By analyzing the amplitude distribution at all frequencies in the spectrogram of each modal component, the frequency characteristic values of each modal component are determined; by analyzing the proportion of the maximum amplitude in the spectrogram of each modal component, the amplitude ratio of each modal component is determined, and in combination with the frequency characteristic values, the first frequency characteristic value of each modal component is determined.

[0024] Generally, existing microwave radar speed detectors usually measure speed using the Doppler principle. The microwave radar speed detector emits electromagnetic waves with a fixed frequency. When the electromagnetic waves hit an object, they are reflected back and received by the microwave radar speed detector. The frequency of the reflected electromagnetic waves will change due to the relative motion between the object and the microwave radar speed detector, and the magnitude of this change is proportional to the speed of the object. The reflected wave signal received by the microwave radar speed detector usually has clutter components such as ground clutter and cloud and rain clutter introduced due to factors such as ground objects and weather in the radar coverage area. The clutter components in the reflected wave signal will be amplified in the digital gain automatic adjustment section of the microwave radar speed detector, thereby affecting the subsequent measurement of the target object's speed. Therefore, to avoid this situation, the following processing is carried out.

[0025] Since the radar speed measurement time can reach dozens of milliseconds, it can be considered that the driving speed of the vehicle is relatively constant during the process of the microwave radar speed detector emitting and receiving signals. Then, during the process of the vehicle approaching the radar coverage area of the microwave radar speed detector, each echo formed by the reflection of the vehicle will have a similar frequency due to the relatively constant vehicle speed. And the echoes formed during the process of the vehicle moving away from the radar coverage area will also have a similar frequency, that is, the signal components corresponding to each echo formed by the vehicle approaching and moving away from the radar coverage area in the reflected wave signal received by the microwave radar speed detector will all have a relatively single frequency distribution. The cloud and rain clutter components mixed in the reflected wave signal will have a complex frequency distribution due to the different sizes and motion states of the raindrops or solid particles in rain and fog, that is, the meteorological clutter components usually do not have a relatively single frequency distribution.

[0026] Based on the above analysis, perform modal decomposition on the reflected wave signals of each moving vehicle. By analyzing the amplitude distribution at all frequencies in the spectrogram of each modal component, determine the frequency eigenvalue of each modal component; by analyzing the proportion of the maximum amplitude in the spectrogram of each modal component, determine the amplitude ratio of each modal component, and combine the frequency eigenvalue to determine the first frequency eigenvalue of each modal component. The specific process is as follows: (1) In this embodiment, first, perform modal decomposition on the reflected wave signals of each moving vehicle. Specifically: In this embodiment, the reflected wave signal is used as the input of the modal decomposition algorithm, and all modal components are output.

[0027] It should be noted that there are many commonly used modal decomposition algorithms. In this embodiment, the Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (CEEMDAN) algorithm is used to perform modal decomposition on the reflected wave signal. In the actual application process, as other implementation manners, the implementer can also use other modal decomposition algorithms such as the Empirical Mode Decomposition (EMD) algorithm according to the specific situation. Regarding the selection of the modal decomposition algorithm, no special restrictions are made in this embodiment.

[0028] Among them, the Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (CEEMDAN) algorithm is a well-known technology, and the specific process of performing modal decomposition on the reflected wave signal will not be elaborated here.

[0029] (2) Further, in this embodiment, by analyzing the amplitude distribution at all frequencies in the spectrogram of each modal component, the frequency characteristic value of each modal component is determined. Specifically: Obtain the spectrogram of each modal component in the reflected wave signal, count the number of frequencies with amplitudes greater than 0 in the spectrogram of each modal component, which is recorded as the number of positive amplitude frequencies. Normalize the number of positive amplitude frequencies of all modal components, and use the normalized value of the number of positive amplitude frequencies of each modal component as the frequency characteristic value of each modal component.

[0030] It should be noted that there are many commonly used normalization methods. In this embodiment, the z-score standardization method is used to normalize the data. In the actual application process, as other implementation manners, the implementer can also use other normalization methods such as the maximum-minimum normalization method according to the specific situation. Regarding the selection of the normalization method, no special restrictions are made in this embodiment.

[0031] Among them, the z-score standardization method is a well-known technology, and the process of normalizing the data will not be elaborated here.

[0032] Supplementary note: In this embodiment, all contents related to normalization processing adopt the z-score standardization method.

[0033] (3) Further, in this embodiment, by analyzing the proportion of the maximum amplitude in the spectrogram of each modal component, the amplitude ratio of each modal component is determined. Specifically: Take the result of normalizing the proportion of the maximum amplitude in the sum of all amplitudes in the spectrogram of each modal component as the amplitude ratio of each modal component.

[0034] (4) Further, in this embodiment, based on the amplitude ratio and frequency characteristic value of each modal component, the first frequency characteristic value of each modal component is determined. Specifically: The ratio of the amplitude ratio of each modal component to the frequency eigenvalue is used as the first frequency eigenvalue of each modal component to evaluate whether the signal component corresponding to the modal component in the reflected wave signal has a relatively single frequency distribution.

[0035] From the first frequency eigenvalue of each modal component, it can be understood that if the amplitude ratio of the current modal component is larger, it means that the energy of this modal component is more concentrated. The smaller the frequency eigenvalue, it indicates that the frequency with a positive amplitude included in this modal component is less, and the frequency distribution is more single and concentrated. The corresponding first frequency eigenvalue is larger, indicating that the possibility of this modal signal having a relatively single frequency distribution is greater; on the contrary, if the amplitude ratio is smaller, it means that the energy of this modal component is more dispersed, and the frequency eigenvalue is large, indicating that the frequency with a positive amplitude included in this modal component is more, then the first frequency eigenvalue will be relatively small, indicating that this modal component is more likely to correspond to clutter, such as rain and cloud clutter. There are a large number of tiny particles with different speeds in rain and clouds, which interfere with the reflected wave signal and result in a broad spectrum.

[0036] So far, in this embodiment, the radar reflected wave signal is separated by modal decomposition, and the spectral characteristics of each component are analyzed. By calculating the first frequency eigenvalue reflecting the energy concentration degree and the frequency distribution width, it can effectively distinguish the vehicle target signal with a single frequency distribution from the clutter such as rain and clouds with a complex frequency distribution, thereby improving the accuracy of radar speed measurement.

[0037] Step S3: Determine the frequency difference of each modal component by analyzing the difference in the main frequencies between each modal component and the microwave radio frequency signal, so as to determine the second frequency eigenvalue of each modal component; based on the first frequency eigenvalue and the second frequency eigenvalue, determine the reflected wave eigenvalue of each modal component, so as to screen out the characteristic components from all modal components of the reflected wave signal, and obtain the reconstructed reflected wave signal of each moving vehicle.

[0038] The ground clutter component in the reflected wave signal received by the microwave radar speedometer is usually formed by the backward scattering of the electromagnetic wave emitted by the radar by the road surface or stationary objects. Since the ground objects in the radar coverage area are relatively stationary with respect to the microwave radar speedometer and the Doppler effect does not occur, each echo in the ground clutter component has a frequency close to that of the electromagnetic wave emitted by the radar, that is, the signal component corresponding to the ground clutter component in the reflected wave signal has a frequency close to that of the microwave radio frequency signal emitted by the microwave radar speedometer, then the signal component will also have a relatively single frequency distribution.

[0039] Based on the above analysis, in this embodiment, by analyzing the difference in the main frequencies between each modal component and the microwave radio frequency signal, the frequency difference of each modal component is determined to determine the second frequency eigenvalue of each modal component; based on the first frequency eigenvalue and the second frequency eigenvalue, the reflected wave eigenvalue of each modal component is determined to screen out the characteristic components from all the modal components of the reflected wave signal, and the reconstructed reflected wave signal of each moving vehicle is obtained. The specific process is as follows: (1) In this embodiment, by analyzing the difference in the main frequencies between each modal component and the microwave radio frequency signal, the frequency difference of each modal component is determined to determine the second frequency eigenvalue of each modal component. Specifically, as an implementation manner, in this embodiment, the absolute value of the difference in the main frequencies between each modal component and the microwave radio frequency signal is used as the frequency difference of each modal component; Further, based on the frequency difference of each modal component, the second frequency eigenvalue of each modal component is determined. In this embodiment, the second frequency eigenvalue of modal component i is expressed as: ; where represents the frequency difference of modal component i; exp( ) represents the exponential function with the natural constant as the base.

[0040] It can be understood from the second frequency eigenvalue of each modal component that the greater the difference in the main frequencies between the modal component and the microwave radio frequency signal, based on the Doppler effect, a large frequency difference usually means that the signal component corresponds to a fast-moving object. Therefore, the smaller the corresponding second frequency eigenvalue, the smaller the possibility that the modal component is stationary or low-speed ground clutter; on the contrary, if the frequency difference is small and the corresponding second frequency eigenvalue is large, it means that the modal component is more likely to be stationary or low-speed ground clutter.

[0041] (2) Further, in this embodiment, based on the first frequency eigenvalue and the second frequency eigenvalue of each modal component, the reflected wave eigenvalue of each modal component is determined. Specifically: As an implementation manner, in this embodiment, the result of dividing the normalized value of the first frequency eigenvalue of each modal component by the normalized value of the second frequency eigenvalue is used as the reflected wave eigenvalue of each modal component, which is used to evaluate the possibility that the signal component corresponding to the modal component in the reflected wave signal is clutter components such as ground clutter and cloud and rain clutter in the reflected wave signal.

[0042] It can be understood from the reflection wave eigenvalue of each modal component that if the first eigenvalue of the frequency of the current modal component is smaller, it indicates that the current modal component is more likely to correspond to cloud and rain clutter, and if the second eigenvalue of the frequency is larger, it indicates that the current modal component is more likely to correspond to ground clutter. Therefore, the smaller the corresponding final reflection wave eigenvalue, the smaller the possibility that the current component is the reflection wave signal during vehicle driving and the greater the possibility of clutter; conversely, if the first eigenvalue of the frequency of the current modal component is larger, it indicates that the current modal component is more likely to correspond to the reflection wave signal of the vehicle and less likely to be cloud and rain clutter, and if the second eigenvalue of the frequency is smaller, it indicates that the current modal component is less likely to correspond to ground clutter. Therefore, the smaller the corresponding final reflection wave eigenvalue, the greater the possibility that the current component is the reflection wave signal during vehicle driving and the smaller the possibility of clutter.

[0043] Preferably, the schematic diagram of the reflection wave eigenvalue extraction process provided in this embodiment is as Figure 2 shown.

[0044] (3) Further, based on the reflection wave eigenvalues of each modal component in this embodiment, to screen out the characteristic components from all modal components of the reflection wave signal and obtain the reconstructed reflection wave signal of each moving vehicle, specifically: In this embodiment, the reflection wave eigenvalues of all modal components in the reflection wave signal are used as the input of the threshold segmentation algorithm, and the segmentation threshold is output. All modal components with reflection wave eigenvalues greater than the segmentation threshold are denoted as characteristic components, and all characteristic components are reconstructed to obtain the reconstructed reflection wave signal, which is used to represent the signal after filtering out clutter components such as ground clutter and cloud and rain clutter in the reflection wave signal.

[0045] It should be noted that there are many commonly used threshold segmentation algorithms. In this embodiment, the maximum inter-class variance algorithm is used to divide the reflection wave eigenvalues. In the actual application process, as other implementation manners, the implementer can also use other threshold segmentation algorithms according to the specific situation. Regarding the selection of the threshold segmentation algorithm, this embodiment does not make special restrictions.

[0046] Among them, both signal reconstruction and the maximum inter-class variance algorithm are well-known technologies, and their specific principles will not be elaborated here.

[0047] So far, in this embodiment, by analyzing the difference between each modal component and the main frequency of the transmitted signal, the second eigenvalue of the frequency is determined, and the reflection wave eigenvalue is calculated in combination with the first eigenvalue of the frequency. This reflection wave eigenvalue is used to evaluate the possibility that each modal component belongs to the vehicle target signal or ground, cloud and rain clutter. The characteristic components are screened out through the threshold segmentation algorithm and the reflection wave signal is reconstructed, effectively filtering out clutter interference and improving the accuracy and reliability of radar speed measurement.

[0048] Step S4: Measure the vehicle speeds of the running vehicles based on the microwave radio frequency signals and the reconstructed reflected wave signals of the running vehicles.

[0049] Mix the microwave radio frequency signals and the reconstructed reflected wave signals of the running vehicles to obtain a mixed signal. Use a low-pass filter to filter the mixed signal to filter out the local oscillator signal therein. Then extract the Doppler signal from the filtered mixed signal, and perform signal amplification processing on the obtained Doppler signal. During the amplification process, use an automatic gain control algorithm to adjust the amplitude in the Doppler signal to a preset range. The upper and lower limits of the preset range can be determined according to the operating voltage of the radar in the microwave radar speedometer. In this embodiment, when the operating voltage is 2 - 3.2V, the upper and lower limits of the preset range can be set to 20000 and 30000 respectively, with the unit of 0.1mv. Further, calculate the speeds of the running vehicles using the Doppler signal.

[0050] Among them, the processes of signal mixing, filtering the signal using a low-pass filter, signal amplification processing, extraction of the Doppler signal, the automatic gain control algorithm, and calculating the vehicle running speed using the Doppler signal are all well-known technologies, and their respective principles and processes will not be elaborated herein.

[0051] Based on the same inventive concept as the above method, the embodiment of the present application also provides a vehicle speed measurement device applied to a vehicle-mounted portable mobile warning screen, including a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, it implements the steps of any one of the above vehicle speed measurement methods applied to the vehicle-mounted portable mobile warning screen.

[0052] It should be noted that: the above sequence of the embodiments of the present application is only for description and does not represent the superiority or inferiority of the embodiments. And the above specific embodiments of this specification have been described. In addition, the processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0053] Each embodiment in this specification is described in a progressive manner. The same or similar parts among the embodiments can be referred to each other, and the key points of each embodiment are the differences from other embodiments.

[0054] The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the principle of the present application shall be included in the protection scope of the present application.

Claims

1. A vehicle speed measurement method applied to an in-vehicle portable mobile warning screen, characterized in that, The method includes the following steps: Obtain the microwave radio frequency signals transmitted by the microwave radar speedometer to each moving vehicle on the road and the reflected wave signals received from each moving vehicle; Perform modal decomposition on the reflected wave signals of each moving vehicle. By analyzing the amplitude distribution at all frequencies in the spectrogram of each modal component, determine the frequency eigenvalue of each modal component; by analyzing the proportion of the maximum amplitude in the spectrogram of each modal component, determine the amplitude ratio of each modal component, and combine the frequency eigenvalue to determine the first frequency eigenvalue of each modal component; By analyzing the difference in the main frequencies between each modal component and the microwave radio frequency signal, determine the frequency difference of each modal component to determine the second frequency eigenvalue of each modal component; based on the first frequency eigenvalue and the second frequency eigenvalue, determine the reflected wave eigenvalue of each modal component to screen out the characteristic components from all modal components of the reflected wave signal and obtain the reconstructed reflected wave signal of each moving vehicle; Based on the microwave radio frequency signal and the reconstructed reflected wave signal of each moving vehicle, measure the vehicle speed of each moving vehicle.

2. The vehicle speed measurement method applied to the vehicle-mounted portable mobile warning screen according to claim 1, characterized in that, The method for determining the frequency eigenvalue of each modal component is: Count the number of frequencies with amplitudes greater than 0 in the spectrogram of each modal component, denoted as the number of positive amplitude frequencies. Normalize the number of positive amplitude frequencies of all modal components, and use the normalized value of the number of positive amplitude frequencies of each modal component as the frequency eigenvalue of each modal component.

3. The vehicle speed measurement method applied to the in-vehicle portable mobile warning screen according to claim 1, characterized in that, The amplitude ratio of each modal component is the result of taking the normalized value of the proportion of the maximum amplitude in the sum of all amplitudes in the spectrogram of each modal component.

4. The vehicle speed measurement method for an in-vehicle portable mobile warning screen as claimed in claim 1, characterized in that, The first frequency eigenvalue of each modal component is the ratio of the amplitude ratio of each modal component to the frequency eigenvalue.

5. The vehicle speed measurement method for an in-vehicle portable mobile warning screen according to claim 1, wherein The frequency difference of each modal component is the absolute value of the difference between the main frequencies of each modal component and the microwave radio frequency signal.

6. The vehicle speed measurement method for an in-vehicle portable mobile warning screen as claimed in claim 1, characterized in that, The expression for the second eigenvalue of the frequency of each modal component is as follows: ; where represents the second eigenvalue of the frequency of modal component i; represents the frequency difference of modal component i; exp( ) represents the exponential function with the natural constant as the base.

7. The vehicle speed measurement method for an in-vehicle portable mobile warning screen as described in claim 1, characterized in that, The reflected wave eigenvalue of each modal component is the result of dividing the normalized value of the first frequency eigenvalue of each modal component by the normalized value of the second frequency eigenvalue.

8. The vehicle speed measurement method for an in-vehicle portable mobile warning screen as claimed in claim 1, wherein, The screening out of the characteristic components from all modal components of the reflected wave signal to obtain the reconstructed reflected wave signal of each moving vehicle includes: Take the reflected wave eigenvalues of all modal components in the reflected wave signal as the input of the threshold segmentation algorithm, output the segmentation threshold, and mark all modal components with reflected wave eigenvalues greater than the segmentation threshold as characteristic components, and reconstruct all characteristic components to obtain the reconstructed reflected wave signal.

9. The vehicle speed measurement method for an in-vehicle portable mobile warning screen according to claim 1, characterized in that, The measurement of the vehicle speed of each moving vehicle includes: Mix the microwave radio frequency signal and the reconstructed reflected wave signal of each moving vehicle to obtain a mixed signal, perform filtering on the mixed signal, extract the Doppler signal from the filtered mixed signal, and calculate the speed of each moving vehicle using the Doppler signal.

10. An in-vehicle speed measurement device applied to an in-vehicle portable mobile warning screen, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the vehicle speed measurement method for the in-vehicle portable mobile warning screen described in any one of claims 1-9.

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