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

Abstract

The present application relates to the field of radar speed measurement technology, and specifically to a vehicle-mounted speed measurement method and device for a portable mobile warning screen. The method comprises: performing modal decomposition on the reflected wave signal of each moving vehicle, determining the first frequency eigenvalue by analyzing the amplitude distribution at all frequencies in the spectrum diagram of each modal component and the proportion of the maximum amplitude; determining the reflected wave eigenvalue by analyzing the difference in the main frequency between each modal component and the microwave radio frequency signal, and combining the first frequency eigenvalue to obtain the reconstructed reflected wave signal of each moving vehicle, and combining the microwave radio frequency signal of each moving vehicle to measure the vehicle-mounted speed of each moving vehicle. The present application filters out the clutter components in the reflected wave signal, thereby improving the accuracy of microwave radar speed measurement.

Description

Technical Field

[0001] The present application relates to the field of radar speed measurement technology, and in particular to a vehicle-mounted speed measurement method and device applied to a vehicle-mounted portable mobile warning screen. Background Art

[0002] The on-board portable mobile warning screen with on-board speed measurement function is a traffic management device that integrates speed measurement and warning functions. It can be quickly deployed to sections of road that require temporary traffic control due to traffic accidents, road construction, etc. By using microwave radar to measure the 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, microwave radar may experience errors in its speed measurement results due to the influence of the external environment and itself. To improve the accuracy of microwave radar speed measurement, 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 kept relatively stable, thereby reducing the measurement error caused by the angle of the radar microwave antenna lobe. However, this method ignores the clutter components introduced in the reflected wave signal received by the radar, causing the clutter components to be amplified in the digital gain automatic adjustment link, thereby reducing the accuracy of microwave radar speed measurement. Summary of the Invention

[0004] In order to solve the above technical problems, the purpose of this application is to provide a vehicle-mounted speed measurement method and device applied to a vehicle-mounted portable mobile warning screen. The technical solutions adopted are as follows:

[0005] In a first aspect, an embodiment of the present application provides a vehicle-mounted speed measurement method applied to a vehicle-mounted portable mobile warning screen, the method comprising the following steps:

[0006] Acquire the microwave radio frequency signals transmitted by the microwave radar speed meter to each vehicle traveling on the road and the reflected wave signals received from each vehicle traveling on the road;

[0007] Performing modal decomposition on the reflected wave signals of each moving vehicle, determining the frequency eigenvalue of each modal component by analyzing the amplitude distribution at all frequencies in the spectrum of each modal component; determining the amplitude ratio of each modal component by analyzing the proportion of the maximum amplitude in the spectrum of each modal component, and determining the first frequency eigenvalue of each modal component in combination with the frequency eigenvalue;

[0008] By analyzing the difference in main frequency 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 filter out the characteristic component from all modal components of the reflected wave signal to obtain a reconstructed reflected wave signal of each moving vehicle;

[0009] The vehicle speed of each moving vehicle is measured based on the microwave radio frequency signal and the reconstructed reflected wave signal of each moving vehicle.

[0010] Preferably, the method for determining the frequency characteristic value of each modal component is:

[0011] The number of frequencies with amplitudes greater than 0 in the spectrum of each modal component is counted and recorded as the number of positive amplitude frequencies. The number of positive amplitude frequencies of all modal components is normalized and the normalized value of the number of positive amplitude frequencies of each modal component is used as the frequency characteristic value of each modal component.

[0012] Preferably, the amplitude ratio of each modal component is a result of taking a normalized value of the proportion of the maximum amplitude in the frequency spectrum of each modal component in the cumulative sum of all amplitudes.

[0013] Preferably, the first frequency eigenvalue of each modal component is a ratio of the amplitude ratio of each modal component to the frequency eigenvalue.

[0014] Preferably, the frequency difference of each modal component is the absolute value of the main frequency difference between each modal component and the microwave radio frequency signal.

[0015] Preferably, the expression of the second frequency eigenvalue of each modal component is: 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 a natural constant as the base.

[0016] Preferably, the reflected wave characteristic value of each modal component is the result of dividing the normalized value of the first frequency characteristic value of each modal component by the normalized value of the second frequency characteristic value.

[0017] Preferably, the step of filtering out characteristic components from all modal components of the reflected wave signal to obtain the reconstructed reflected wave signal of each moving vehicle includes:

[0018] The reflected wave eigenvalues of all modal components in the reflected wave signal are used as the input of the threshold segmentation algorithm, and the segmentation threshold is output. All modal components with reflected wave eigenvalues greater than the segmentation threshold are recorded as characteristic components. All characteristic components are reconstructed to obtain the reconstructed reflected wave signal.

[0019] Preferably, the measuring of the vehicle speed of each traveling vehicle includes:

[0020] The microwave radio frequency signal of each moving vehicle and the reconstructed reflected wave signal are mixed to obtain a mixed signal, the mixed signal is filtered, the Doppler signal is extracted from the filtered mixed signal, and the speed of each moving vehicle is calculated using the Doppler signal.

[0021] In the second aspect, an embodiment of the present application also provides a vehicle-mounted speed measuring device applied to a vehicle-mounted portable mobile warning screen, comprising 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-mentioned vehicle-mounted speed measurement methods applied to a vehicle-mounted portable mobile warning screen.

[0022] This application has at least the following beneficial effects:

[0023] The present application constructs a first frequency eigenvalue by performing modal decomposition on the reflected wave signals of each moving vehicle and analyzing the amplitude distribution and the proportion of the maximum amplitude at all frequencies in the spectrum diagram of each modal component. This can effectively distinguish the various echoes and cloud and rain clutter components in the reflected wave signals received by the microwave radar speed meter caused by vehicles approaching or moving away from the radar coverage area, and thus can effectively filter out the cloud and rain clutter components in the reflected wave signals. Furthermore, the present application constructs a second frequency eigenvalue of each modal component by analyzing the difference in the main frequency between each modal component and the microwave radio frequency signal, and determines the second frequency eigenvalue of each modal component in combination with the first frequency eigenvalue. The reflected wave characteristic value is used to screen out characteristic components from all modal components of the reflected wave signal to obtain a reconstructed reflected wave signal of each moving vehicle, which can effectively filter out signal components corresponding to clutter components such as ground clutter and cloud and rain clutter in the reflected wave signal. The present application automatically gains the Doppler signal generated by the reconstructed reflected wave signal. While ensuring the relative stability of the amplitude of the Doppler signal generated by the microwave radar speed meter, it avoids the situation where the signal components corresponding to clutter components such as ground clutter and cloud and rain clutter in the Doppler signal are also amplified by automatic digital gain adjustment, thereby improving the accuracy of the microwave radar speed measurement results. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions and advantages of the embodiments of the present application or the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0025] Figure 1A flowchart of the steps of a vehicle-mounted speed measurement method applied to a vehicle-mounted portable mobile warning screen provided in one embodiment of the present application;

[0026] Figure 2 A schematic diagram of the reflected wave feature value extraction process provided in one embodiment of the present application. DETAILED DESCRIPTION

[0027] In order to further illustrate the technical means and effects adopted by this application to achieve the predetermined invention purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, describes in detail the vehicle-mounted speed measurement method and device for a portable mobile warning screen in accordance with this application, its specific implementation, structure, features and effects. In the following description, different "one embodiment" or "another embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics of one or more embodiments may be combined in any suitable form.

[0028] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0029] The specific scheme of the vehicle-mounted speed measurement method and device applied to the vehicle-mounted portable mobile warning screen provided by the present application is described in detail below with reference to the accompanying drawings.

[0030] See also Figure 1 , which shows a flowchart of a vehicle-mounted speed measurement method applied to a vehicle-mounted portable mobile warning screen provided by an embodiment of the present application, the method comprising the following steps:

[0031] Step S1: Acquire the microwave radio frequency signal emitted by the microwave radar speed meter to each vehicle traveling on the road and the reflected wave signal received from each vehicle traveling on the road.

[0032] The on-board portable mobile warning screen with on-board speed measurement function is a traffic management device that integrates speed measurement and warning functions. It can be quickly deployed to sections of road that require temporary traffic control due to traffic accidents, road construction, etc. By using microwave radar to measure the 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.

[0033] Therefore, in this embodiment, the speed of the traveling vehicle is measured by acquiring the microwave radio frequency signal emitted by the microwave radar speed meter to each traveling vehicle on the road, and the reflected wave signal received by the microwave radar speed meter from each traveling vehicle.

[0034] Step S2: Perform modal decomposition on the reflected wave signal of each moving vehicle, and determine the frequency eigenvalue of each modal component by analyzing the amplitude distribution at all frequencies in the spectrum diagram of each modal component; determine the amplitude ratio of each modal component by analyzing the proportion of the maximum amplitude in the spectrum diagram of each modal component, and determine the first frequency eigenvalue of each modal component in combination with the frequency eigenvalue.

[0035] Generally speaking, existing microwave radar speed guns usually use the Doppler principle to measure speed. Microwave radar speed guns emit electromagnetic waves of a fixed frequency. When the electromagnetic waves hit an object, they are reflected back and received by the microwave radar speed gun. The frequency of the reflected electromagnetic waves will change due to the relative motion between the object and the microwave radar speed gun, and the magnitude of the change will be proportional to the object's speed. The reflected wave signal received by the microwave radar speed gun will usually introduce clutter components such as ground clutter, cloud clutter, and rain clutter into the reflected wave signal 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 link of the microwave radar speed gun, thereby affecting the subsequent measurement of the target object's speed. Therefore, to avoid this situation, the following processing is performed.

[0036] Because radar speed measurement time can reach tens of milliseconds, it can be assumed that the vehicle's speed is relatively constant during the process of the microwave radar speed gun transmitting and receiving signals. Therefore, when the vehicle approaches the radar coverage area of the microwave radar speed gun, the echoes formed by the vehicle's reflections will have similar frequencies due to the vehicle's relatively constant speed. Furthermore, the echoes formed when the vehicle moves away from the radar coverage area will also have similar frequencies. In other words, the corresponding signal components of the reflected wave signals received by the microwave radar speed gun for the echoes formed by the vehicle approaching and moving away from the radar coverage area will have a relatively simple frequency distribution. However, the cloud and rain clutter components mixed in the reflected wave signals will have a complex frequency distribution due to the different sizes and motion states of raindrops or solid particles in rain and fog. In other words, the meteorological clutter components generally do not have a relatively simple frequency distribution.

[0037] Based on the above analysis, the reflected wave signals of each moving vehicle are modally decomposed. The frequency eigenvalues of each modal component are determined by analyzing the amplitude distribution at all frequencies in the spectrum of each modal component. The amplitude ratio of each modal component is determined by analyzing the proportion of the maximum amplitude in the spectrum of each modal component. Combined with the frequency eigenvalues, the first frequency eigenvalue of each modal component is determined. The specific process is as follows:

[0038] (1) In this embodiment, first, the reflected wave signal of each moving vehicle is subjected to modal decomposition, specifically:

[0039] This embodiment uses the reflected wave signal as the input of the modal decomposition algorithm and outputs all modal components.

[0040] 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 actual application, as other implementation methods, implementers may also adopt other modal decomposition algorithms such as the empirical mode decomposition (EMD) algorithm based on specific circumstances. This embodiment does not impose any special restrictions on the selection of the modal decomposition algorithm.

[0041] 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 described in detail.

[0042] (2) Furthermore, this embodiment determines the frequency characteristic value of each modal component by analyzing the amplitude distribution at all frequencies in the spectrum diagram of each modal component, specifically:

[0043] Obtain the frequency spectrum of each modal component in the reflected wave signal, count the number of frequencies with amplitudes greater than 0 in the frequency spectrum of each modal component, record them 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.

[0044] It should be noted that there are many commonly used normalization methods. In this embodiment, the z-score normalization method is used to normalize the data. In actual application, as other implementation methods, the implementer may also adopt other normalization methods such as the maximum and minimum value normalization method based on the specific situation. Regarding the selection of the normalization method, this embodiment does not impose any special restrictions.

[0045] Among them, the z-score normalization method is a well-known technology, and the process of normalizing the data is not described in detail.

[0046] It should be noted that, in this embodiment, all the contents involving normalization processing adopt the z-score normalization method.

[0047] (3) Furthermore, this embodiment determines the amplitude ratio of each modal component by analyzing the proportion of the maximum amplitude in the spectrum diagram of each modal component, specifically:

[0048] The normalized value of the proportion of the maximum amplitude in the spectrum of each modal component in the accumulated sum of all amplitudes is taken as the amplitude ratio of each modal component.

[0049] (4) Furthermore, this embodiment determines the first frequency eigenvalue of each modal component based on the amplitude ratio and frequency eigenvalue of each modal component, specifically:

[0050] 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.

[0051] According to 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 the modal component is more concentrated, and the frequency eigenvalue is smaller, it means that the modal component contains fewer frequencies with positive amplitudes, and the frequency distribution is more single and concentrated, and the corresponding first frequency eigenvalue is larger, indicating that the modal signal is more likely to have a relatively single frequency distribution; conversely, if the amplitude ratio is smaller, it means that the energy of the modal component is more dispersed, and the frequency eigenvalue is larger, indicating that the modal component contains more frequencies with positive amplitudes, then the first frequency eigenvalue will be smaller, indicating that the modal component is more likely to correspond to clutter, such as cloud and rain clutter. Clouds and rain contain a large number of tiny particles with different speeds, which interfere with the reflected wave signal and cause a wide spectrum.

[0052] Thus, this embodiment separates the radar reflected wave signal through modal decomposition and analyzes the spectral characteristics of each component. By calculating the first frequency eigenvalue reflecting the energy concentration and frequency distribution width, it can effectively distinguish between vehicle target signals with a single frequency distribution and clutter such as clouds and rain with complex frequency distributions, thereby improving the accuracy of radar speed measurement.

[0053] Step S3: By analyzing the difference in main frequency 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 filter out the characteristic components from all modal components of the reflected wave signal to obtain the reconstructed reflected wave signal of each moving vehicle.

[0054] The ground clutter component in the reflected wave signal received by a microwave radar speed gun is typically formed by the backscattering of electromagnetic waves emitted by the radar by the road surface or stationary objects. Because the ground objects within the radar coverage area are relatively stationary with the microwave radar speed gun, no Doppler effect occurs. As a result, 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 speed gun, and the signal component also has a relatively single frequency distribution.

[0055] Based on the above analysis, this embodiment determines the frequency difference of each modal component by analyzing the difference in the main frequency between each modal component and the microwave radio frequency signal, thereby determining 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 filter out the characteristic component from all modal components of the reflected wave signal, thereby obtaining a reconstructed reflected wave signal of each moving vehicle. The specific process is as follows:

[0056] (1) In this embodiment, the frequency difference of each modal component is determined by analyzing the difference in the main frequency between each modal component and the microwave radio frequency signal, so as to determine the second frequency eigenvalue of each modal component. Specifically, as an implementation method, in this embodiment, the absolute value of the main frequency difference between each modal component and the microwave radio frequency signal is used as the frequency difference of each modal component;

[0057] Furthermore, 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 The expression is: Where, represents the frequency difference of modal component i; exp( ) represents the exponential function with a natural constant as the base.

[0058] The second frequency eigenvalue of each modal component indicates that the greater the difference in main frequency between the modal component and the microwave RF signal, the greater the Doppler effect. This large frequency difference generally indicates that the signal component corresponds to a high-speed moving object. Therefore, the smaller the corresponding second frequency eigenvalue, the less likely the modal component is stationary or low-speed ground clutter. Conversely, a smaller frequency difference and a larger corresponding second frequency eigenvalue indicate a greater likelihood that the modal component is stationary or low-speed ground clutter.

[0059] (2) Furthermore, 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:

[0060] As an implementation method, 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. This is used to assess the possibility that the signal component corresponding to the modal component in the reflected wave signal is a clutter component such as ground clutter or cloud and rain clutter in the reflected wave signal.

[0061] According to the reflected wave eigenvalues of each modal component, it can be understood that if the first frequency eigenvalue of the current modal component is smaller, it means that the current modal component is more likely to correspond to cloud and rain clutter, and if the second frequency eigenvalue is larger, it means that the current modal component is more likely to correspond to ground clutter. Therefore, the smaller the corresponding final reflected wave eigenvalue is, the less likely the current component is a reflected wave signal from a moving vehicle and the more likely it is to be clutter. Conversely, if the first frequency eigenvalue of the current modal component is larger, it means that the current modal component is more likely to correspond to a reflected wave signal from a moving vehicle and the less likely it is to be cloud and rain clutter, and if the second frequency eigenvalue is smaller, it means that the current modal component is less likely to correspond to ground clutter. Therefore, the smaller the corresponding final reflected wave eigenvalue is, the more likely the current component is a reflected wave signal from a moving vehicle and the less likely it is to be clutter.

[0062] Preferably, the schematic diagram of the reflected wave feature value extraction process provided in this embodiment is as follows: Figure 2 shown.

[0063] (3) Furthermore, this embodiment uses the reflected wave characteristic values of each modal component to filter out characteristic components from all modal components of the reflected wave signal to obtain the reconstructed reflected wave signal of each moving vehicle, specifically:

[0064] In this embodiment, the reflected wave eigenvalues of all modal components in the reflected wave signal are used as input to a threshold segmentation algorithm, which outputs a segmentation threshold. All modal components with reflected wave eigenvalues greater than the segmentation threshold are recorded as characteristic components. All characteristic components are reconstructed to obtain a reconstructed reflected wave signal, which is used to represent the signal after clutter components such as ground clutter and cloud and rain clutter in the reflected wave signal are filtered out.

[0065] 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 reflected wave characteristic values. In actual application, as other implementation methods, implementers can also adopt other threshold segmentation algorithms based on specific circumstances. Regarding the selection of threshold segmentation algorithms, this embodiment does not impose any special restrictions.

[0066] Among them, signal reconstruction and maximum inter-class variance algorithm are both well-known technologies, and their specific principles are not described in detail here.

[0067] At this point, this embodiment determines the second frequency eigenvalue by analyzing the difference between each modal component and the main frequency of the transmitted signal, and calculates the reflected wave eigenvalue in combination with the first frequency eigenvalue. This reflected wave eigenvalue is used to assess the likelihood that each modal component belongs to a vehicle target signal or ground object, cloud, or rain clutter. The threshold segmentation algorithm is used to filter out the characteristic components and reconstruct the reflected wave signal, effectively filtering out clutter interference and improving the accuracy and reliability of radar speed measurement.

[0068] Step S4: Based on the microwave radio frequency signal and the reconstructed reflected wave signal of each moving vehicle, the vehicle speed of each moving vehicle is measured.

[0069] The microwave radio frequency signal of each moving vehicle and the reconstructed reflected wave signal are mixed to obtain a mixed signal. The mixed signal is filtered using a low-pass filter to filter out the local oscillator signal therein. The Doppler signal is then extracted from the filtered mixed signal and amplified. During the amplification process, an automatic gain control algorithm is used to adjust the amplitude of the Doppler signal to within a preset range. The upper and lower limits of the preset range can be determined based on the operating voltage of the radar in the microwave radar speed meter. In this embodiment, when the operating voltage is 2-3.2V, the upper and lower limits of the preset range can be set to 20,000 and 30,000, respectively, in units of 0.1mV. Furthermore, the speed of each moving vehicle is calculated using the Doppler signal.

[0070] Among them, the signal mixing, filtering the signal using a low-pass filter, amplifying the signal, extracting the Doppler signal, the automatic gain control algorithm, and calculating the vehicle speed using the Doppler signal are all well-known technologies, and their respective principles and specific processes will not be repeated here.

[0071] Based on the same inventive concept as the above method, an embodiment of the present application also provides a vehicle-mounted speed measuring 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-mentioned vehicle-mounted speed measurement methods applied to a vehicle-mounted portable mobile warning screen.

[0072] It should be noted that the order in which the embodiments of the present application are presented is for illustrative purposes only and does not necessarily represent the superiority or inferiority of the embodiments. Furthermore, the foregoing descriptions of specific embodiments of this specification are provided. Furthermore, the processes depicted in the accompanying drawings do not necessarily require the specific order or sequential sequence shown to achieve the desired results. In certain embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0073] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments.

[0074] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A vehicle-mounted speed measurement method applied to a vehicle-mounted portable mobile warning screen, characterized in that: The method comprises the following steps: Acquire the microwave radio frequency signals transmitted by the microwave radar speed meter to each vehicle traveling on the road and the reflected wave signals received from each vehicle traveling on the road; Performing modal decomposition on the reflected wave signals of each moving vehicle, determining the frequency eigenvalue of each modal component by analyzing the amplitude distribution at all frequencies in the spectrum of each modal component; determining the amplitude ratio of each modal component by analyzing the proportion of the maximum amplitude in the spectrum of each modal component, and determining the first frequency eigenvalue of each modal component in combination with the frequency eigenvalue; By analyzing the difference in main frequency 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, the reflected wave eigenvalue of all modal components in the reflected wave signal is used as input of a threshold segmentation algorithm, a segmentation threshold is output, all modal components with reflected wave eigenvalues greater than the segmentation threshold are recorded as characteristic components, all characteristic components are reconstructed to obtain a reconstructed reflected wave signal; The vehicle speed of each moving vehicle is measured based on the microwave radio frequency signal and the reconstructed reflected wave signal of each moving vehicle.

2. The vehicle-mounted speed measurement method applied to a vehicle-mounted portable mobile warning screen according to claim 1, characterized in that: The method for determining the frequency characteristic value of each modal component is: The number of frequencies with amplitudes greater than 0 in the spectrum of each modal component is counted and recorded as the number of positive amplitude frequencies. The number of positive amplitude frequencies of all modal components is normalized and the normalized value of the number of positive amplitude frequencies of each modal component is used as the frequency characteristic value of each modal component.

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

4. The vehicle-mounted speed measurement method applied to a vehicle-mounted portable mobile warning screen according to claim 1, characterized in that: The first frequency eigenvalue of each modal component is a ratio of the amplitude ratio of each modal component to the frequency eigenvalue.

5. The vehicle-mounted speed measurement method applied to a vehicle-mounted portable mobile warning screen according to claim 1, characterized in that: The frequency difference of each modal component is the absolute value of the main frequency difference between each modal component and the microwave radio frequency signal.

6. The vehicle-mounted speed measurement method applied to a vehicle-mounted portable mobile warning screen according to claim 1, characterized in that: The expression of the second frequency eigenvalue of each modal component is: 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 a natural constant as the base.

7. The vehicle-mounted speed measurement method applied to a vehicle-mounted portable mobile warning screen according to 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-mounted speed measurement method applied to a vehicle-mounted portable mobile warning screen according to claim 1, characterized in that: The measuring of the vehicle speed of each traveling vehicle includes: The microwave radio frequency signal of each moving vehicle and the reconstructed reflected wave signal are mixed to obtain a mixed signal, the mixed signal is filtered, the Doppler signal is extracted from the filtered mixed signal, and the speed of each moving vehicle is calculated using the Doppler signal.

9. A vehicle-mounted speed measuring device applied to a vehicle-mounted 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, the steps of the vehicle-mounted speed measurement method applied to a vehicle-mounted portable mobile warning screen are implemented as described in any one of claims 1-8.

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