Laser dynamic speed measurement system and laser dynamic speed measurement method for highway vehicles in rainy and foggy weather

Abstract

The application provides a laser dynamic speed measurement system and a laser dynamic speed measurement method for vehicles on a highway in rainy and foggy weather. The method comprises the following steps: collecting echo signals of a laser beam reflected by vehicles; performing polarization diversity detection on the echo signals to separate polarization components and obtain speed signals and displacement signals of the vehicles; determining multiple frequency shifts of the laser based on the speed signals, determining instantaneous speeds of the vehicles according to all the frequency shifts and the wavelength of the speed signals; performing stripping compensation on a time-varying phase of the displacement signals according to all the instantaneous speeds, and obtaining displacement reconstruction signals; performing equal optical frequency interval resampling on the displacement reconstruction signals through a preset beat frequency signal, and then determining observation distances of the vehicles according to the resampling results; correcting speed deviations according to all the time differences and all the observation distances, and obtaining dynamic speeds of the vehicles on the highway in rainy and foggy weather. The method can realize high-precision dynamic speed measurement of multiple vehicles on a highway under the interference of rainy and foggy weather.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of speed measurement, and more particularly, to a laser dynamic speed measurement system and a method for measuring the speed of vehicles on a highway in rainy and foggy weather. BACKGROUND

[0002] The laser dynamic speed measurement technology is widely used in the field of speed monitoring of vehicles on highways, but its measurement performance is easily affected by environmental factors. Extreme conditions such as rainy and foggy weather, highway construction zones, and sand-dust environments can significantly interfere with the propagation of laser.

[0003] In the prior art, the laser speed measurement method usually uses a single laser source and a conventional optical system to achieve speed measurement by receiving the laser signal reflected by the vehicle. However, in rainy and foggy weather, the rain and fog scattering noise will mix into the echo signal, the Mie scattering broadening effect of the laser will cause frequency shift distortion, the refraction error will also affect the distance measurement accuracy, and the unstable difference in the repetition frequency of the two optical combs will also introduce additional errors, which will cause the speed measurement accuracy of the traditional method to decrease sharply, and even a near-distance measurement blind area will appear. Therefore, how to achieve high-precision dynamic speed measurement of multiple vehicles on a highway under the interference of rainy and foggy weather has become a difficult problem in the industry. SUMMARY

[0004] The present application provides a laser dynamic speed measurement system and a method for measuring the speed of vehicles on a highway in rainy and foggy weather, which can achieve high-precision dynamic speed measurement of multiple vehicles on a highway under the interference of rainy and foggy weather.

[0005] In a first aspect, the present application provides a method for measuring the speed of vehicles on a highway in rainy and foggy weather, wherein a probe light source is generated by a double laser in advance to irradiate vehicles moving on the highway. The method comprises the following steps:

[0006] Collecting the echo signal containing rain and fog scattering noise in the laser beam reflected by the vehicle;

[0007] Performing polarization diversity detection on the echo signal to separate the polarization components of the rain and fog scattering light and the vehicle reflected light, and obtaining the speed signal and the displacement signal of the vehicle;

[0008] Determining a plurality of frequency shifts caused by the broadening effect of Mie scattering of laser due to rain and fog based on the speed signal, and determining the instantaneous speed of each vehicle on the wet road surface according to all the frequency shifts and the wavelength of the speed signal;

[0009] Compensating and suppressing the rain and fog noise in the displacement signal caused by the movement of the vehicle according to the instantaneous speed of each vehicle, and generating a displacement reconstruction signal;

[0010] The displacement reconstruction signal is resampled at equal optical frequency intervals by a preset beat signal, and then the observation distance of each vehicle under rain and fog refraction error is determined according to the resampled displacement reconstruction signal.

[0011] The time difference of each vehicle passing through the baseline distance is obtained, the speed deviation caused by rain and fog refraction is corrected according to all time differences and all observation distances, and then the dynamic speed of each vehicle on the highway in rain and fog weather is obtained.

[0012] In some embodiments, the polarization diversity detection of the echo signal separates the polarization components of the rain and fog scattering light and the vehicle reflection light to obtain the speed signal and the displacement signal of the vehicle, specifically comprising:

[0013] The echo signal is separated into a high-speed straight-through channel and a different polarization state of a forward channel and received by a detector;

[0014] A plurality of polarization intensities in each forward channel are determined;

[0015] The polarization intensity ratio of the rain and fog scattering light and the vehicle reflection light is determined according to all polarization light intensities;

[0016] The displacement signal of the vehicle is determined by all polarization intensity ratios;

[0017] The speed signal of the vehicle is determined according to the signal of the high-speed straight-through channel received by the detector.

[0018] In some embodiments, the plurality of frequency shifts caused by the broadening effect of laser Mie scattering of rain and fog based on the speed signal specifically comprises:

[0019] The frequency spectrum distribution of the speed signal is determined;

[0020] Centroid tracking is performed on all frequency spectrum distributions to obtain the plurality of frequency shifts caused by the broadening effect of laser Mie scattering of rain and fog.

[0021] In some embodiments, the instantaneous speed of each vehicle on a wet and slippery highway surface is determined according to all frequency shifts and the wavelength of the speed signal, specifically comprising:

[0022] The wavelength of the speed signal is obtained;

[0023] A frequency shift is selected as a selected frequency shift;

[0024] The instantaneous speed of the vehicle corresponding to the selected frequency shift is determined according to the selected frequency shift and the wavelength of the speed signal;

[0025] The instantaneous speed of the vehicle corresponding to the remaining frequency shift is continuously determined.

[0026] In some embodiments, the demodulating and suppressing rain and fog noise from the displacement signal according to the instantaneous speed of each vehicle to generate a displacement reconstruction signal specifically comprises:

[0027] determining a plurality of Doppler phase offsets of the displacement signal according to all the instantaneous speeds;

[0028] determining a plurality of time-varying phases of the displacement signal when each vehicle displaces;

[0029] demodulating the phase-varying component of each vehicle motion from the displacement signal through all the time-varying phases and all the Doppler phase offsets to obtain a plurality of residual phases of the displacement signal containing only rain and fog noise;

[0030] suppressing rain and fog noise from all the residual phases of the displacement signal containing only rain and fog noise to generate a displacement reconstruction signal.

[0031] In some embodiments, the equal optical frequency interval resampling of the displacement reconstruction signal through a preset beat signal specifically comprises:

[0032] obtaining a preset beat signal;

[0033] regarding all the time instants when all the voltage zero-crossing points of the beat signal and the change of laser frequency are the same as sampling clocks;

[0034] converting the displacement reconstruction signal to uniform optical frequency according to all the sampling clocks to obtain a resampled displacement reconstruction signal.

[0035] In some embodiments, determining the observed distance of each vehicle under the rain and fog refraction error according to the resampled displacement reconstruction signal specifically comprises:

[0036] determining a plurality of main peak frequencies of the resampled displacement reconstruction signal;

[0037] determining the observed distance of each vehicle under the rain and fog refraction error according to all the main peak frequencies.

[0038] In some embodiments, correcting the speed deviation caused by rain and fog refraction according to all the time differences and all the observed distances to obtain the dynamic speed of each vehicle on the highway in rain and fog weather specifically comprises:

[0039] determining the air refractive index in rain and fog weather;

[0040] correcting all the observed distances according to the air refractive index;

[0041] determining the dynamic speed of each vehicle on the highway in rain and fog weather according to the corrected all the observed distances and all the time differences.

[0042] In some embodiments, the echo signal containing rain and fog scattering noise in the laser beam reflected by the vehicle is collected by a Cassegrain telescope.

[0043] In a second aspect, the application provides a laser dynamic speed measurement system, comprising:

[0044] a collecting module configured to collect an echo signal containing rain and fog scattering noise in a laser beam reflected by a vehicle;

[0045] a processing module configured to perform polarization diversity detection on the echo signal to separate the polarization components of the rain and fog scattering light and the vehicle reflected light, and obtain a speed signal and a displacement signal of the vehicle;

[0046] The processing module is further configured to determine a plurality of frequency shifts caused by the broadening effect of the Mie scattering of the laser by rain and fog based on the speed signal, and determine the instantaneous speed of each vehicle on a wet and slippery highway surface according to all the frequency shifts and the wavelength of the speed signal.

[0047] The processing module is further configured to compensate and suppress rain and fog noise in the displacement signal caused by the movement of the vehicle according to the instantaneous speed of each vehicle, and generate a displacement reconstruction signal.

[0048] The processing module is further configured to perform equal optical frequency interval resampling on the displacement reconstruction signal by a preset beat frequency signal, and further determine the observation distance of each vehicle under the rain and fog refraction error according to the resampled displacement reconstruction signal.

[0049] The execution module is configured to obtain the time difference of each vehicle passing through the baseline distance, correct the speed deviation caused by rain and fog refraction according to all the time differences and all the observation distances, and further obtain the dynamic speed of each vehicle on the highway in rain and fog weather.

[0050] The technical scheme provided by the embodiments of the application has the following beneficial effects:

[0051] The laser dynamic speed measurement system and the laser dynamic speed measurement method for vehicles on a highway in rainy and foggy weather provided by the application first collect echo signals containing rain and fog scattering noise in a laser beam reflected by a vehicle; perform polarization diversity detection on the echo signals to separate the polarization components of rain and fog scattering light and vehicle reflected light, and obtain a speed signal and a displacement signal of the vehicle; determine a plurality of frequency shifts caused by the broadening effect of Mie scattering of laser due to rain and fog based on the speed signal, determine the instantaneous speed of each vehicle on a wet and slippery highway surface according to all frequency shifts and the wavelength of the speed signal; compensate and suppress rain and fog noise in the time-varying phase caused by vehicle movement in the displacement signal according to the instantaneous speed of each vehicle, and generate a displacement reconstruction signal; perform equal optical frequency interval resampling on the displacement reconstruction signal through a preset beat frequency signal, and then determine the observation distance of each vehicle under rain and fog refraction error according to the resampled displacement reconstruction signal; obtain the time difference of each vehicle passing through the baseline distance, correct the speed deviation caused by rain and fog refraction according to all time differences and all observation distances, and then obtain the dynamic speed of each vehicle on the highway in rainy and foggy weather.

[0052] As can be seen, in the process of the laser dynamic speed measurement method for vehicles on a highway in rainy and foggy weather, first, the echo signals containing rain and fog scattering noise in the laser beam reflected by the vehicle are collected; the polarization diversity detection is performed on the echo signals to separate the polarization components of the rain and fog scattering light and the vehicle reflected light, and the speed signal and the displacement signal of the vehicle are obtained; the plurality of frequency shifts caused by the broadening effect of Mie scattering of laser due to rain and fog are determined based on the speed signal, and the instantaneous speed of each vehicle on the wet and slippery highway surface is determined according to all frequency shifts and the wavelength of the speed signal; the time-varying phase caused by vehicle movement in the displacement signal is compensated and suppressed according to the instantaneous speed of each vehicle, and the displacement reconstruction signal is generated. The displacement reconstruction signal is a signal reconstructed after the interference of the displacement signal of each vehicle is removed. The displacement reconstruction signal is a digital signal, which is convenient for subsequent determination of the observation distance of each vehicle. Secondly, the equal optical frequency interval resampling is performed on the displacement reconstruction signal through the preset beat frequency signal, and then the observation distance of each vehicle under rain and fog refraction error is determined according to the resampled displacement reconstruction signal. The sampling clock refers to the time mark and trigger signal of the control signal for sampling. The traditional time domain sampling will cause uneven sampling interval in the optical frequency domain due to the nonlinearity of laser frequency modulation. The zero-crossing mark with completely equal laser frequency variation is the moment of uniform optical frequency domain. The resampling of the displacement reconstruction signal triggered by the mark can ensure that the sampling point interval of the displacement reconstruction signal in the optical frequency domain is strictly equal. The time difference of each vehicle passing through the baseline distance is obtained, the speed deviation caused by rain and fog refraction is corrected according to all time differences and all observation distances, and then the dynamic speed of each vehicle on the highway in rainy and foggy weather is obtained. The above scheme can realize high-precision dynamic speed measurement of multiple vehicles on the highway under the interference of rainy and foggy weather. BRIEF DESCRIPTION OF DRAWINGS

[0053] Figure 1 is an example flow chart of a rain and fog weather highway vehicle laser dynamic speed measurement method according to some embodiments of the present application;

[0054] Figure 2 is an example flow chart of determining displacement reconstruction signals according to some embodiments of the present application;

[0055] Figure 3 is an engineering schematic diagram of obtaining a time difference of a vehicle passing a baseline distance according to some embodiments of the present application;

[0056] Figure 4 is a structural schematic diagram of a laser dynamic speed measurement system according to some embodiments of the present application;

[0057] Figure 5 is a structural schematic diagram of a computer device for implementing a rain and fog weather highway vehicle laser dynamic speed measurement method according to some embodiments of the present application. DETAILED DESCRIPTION

[0058] In order to better understand the above technical solutions, the above technical solutions will be described in detail below in combination with the drawings in the specification and specific embodiments.

[0059] Reference Figure 1 The figure is an example flow chart of a rain and fog weather highway vehicle laser dynamic speed measurement method according to some embodiments of the present application, which mainly includes the following steps:

[0060] In step 101, the echo signal containing rain and fog scattering noise in the laser beam reflected by the vehicle is collected.

[0061] In specific implementation, two laser generators are used to generate two laser light sources with different wavelengths, the long-wave laser is split into an irradiation light and a local reference light through a fiber coupler, and the irradiation light and the short-wave laser are emitted to the highway surface through a collimator, the irradiation light covers the vehicle and the rain and fog area at the same time, the echo signal fragments reflected by each vehicle are received through a Cassegrain telescope, and the set of all collected echoes is used as the collected mixed echo signal without processing; wherein the echo signal refers to the signal of the received laser reflected by the vehicle, and the echo signal contains rain and fog noise and echo signal fragments of each vehicle.

[0062] In step 102, the echo signal is subjected to polarization diversity detection to separate the polarization components of the rain and fog scattering light and the vehicle reflection light, to obtain the speed signal and the displacement signal of the vehicle.

[0063] In some embodiments, the steps of performing polarization diversity detection to separate the polarization components of the rain and fog scattering light and the vehicle reflection light from the echo signal, obtaining the speed signal and the displacement signal of the vehicle can be implemented as follows:

[0064] Separating the echo signal into a high-speed straight-through channel and different polarization state of the transmission channel and receiving by the detector;

[0065] Determining the polarization intensity in each transmission channel;

[0066] Determining the polarization intensity ratio of the rain and fog scattering light and the vehicle reflection light according to all the polarization light intensities;

[0067] Determining the displacement signal of the vehicle by all the polarization intensity ratios;

[0068] Determining the speed signal of the vehicle according to the signal of the high-speed straight-through channel received by the detector.

[0069] In a specific implementation, the step of separating the echo signal into a high-speed straight-through channel and different polarization state of the transmission channel and receiving by the detector can be implemented as follows: using a polarization beam splitter in the prior art to divide each vehicle short wave echo signal segment in the collected echo signal into two transmission channels of vertical polarization (i.e., S transmission channel) and parallel polarization (i.e., P transmission channel), to obtain vertical polarization light and parallel polarization light, and to allocate each vehicle long wave echo signal segment in the collected echo signal to the high-speed straight-through channel, and then receiving the vertical polarization light and the parallel polarization light by an avalanche photodetector and converting the vertical polarization light and the parallel polarization light from optical signals to electrical signals, and converting the echo signal in the high-speed straight-through channel into an electrical signal by a photodetector, wherein the long wave echo signal segment is allocated to the high-speed straight-through channel to avoid any interference of polarization elements, which can protect the Doppler phase dynamic range of the long wave echo signal and thus control the phase distortion rate of the long wave echo signal; in other embodiments, other methods can also be used, which are not limited here.

[0070] In a specific implementation, the multiple polarization intensities in each of the positive channels can be determined by the following method: first, the high-frequency noise is suppressed and the gain is amplified (the signal amplitude is unified) for the electrical signals of the echo signals of the short wave in the S positive channel and the P positive channel by using a high-speed signal conditioning circuit; second, the electrical signals in the S positive channel and the P positive channel after processing are quantized into digital signals by using an analog-to-digital converter; then, the electrical signals in the S positive channel and the P positive channel are sorted according to the collection time respectively, to obtain a vertical channel intensity sequence and a parallel channel intensity sequence; the vertical channel intensity sequence is a sequence describing the intensity of the polarized light in the vertical incidence plane changing with time, including a vertical channel intensity sub-sequence of each vehicle and a vertical polarized light intensity at each sampling time point, and one sampling time point corresponds to one vertical polarized light intensity; the parallel channel intensity sequence is a sequence describing the intensity of the polarized light in the parallel incidence plane changing with time, including a horizontal channel intensity sub-sequence of each vehicle and a parallel polarized light intensity at each sampling time point, and one sampling time point corresponds to one parallel polarized light intensity; finally, all the vertical polarized light intensities and the parallel polarized light intensities are taken as the polarization intensities of the corresponding positive channels; the polarization intensity refers to the intensity of the energy carried by the light signals in the vertical and parallel polarization states, and is used to reflect the energy size of the two polarization components in the echo signal; in other embodiments, other methods can also be used for implementation, which are not limited here.

[0071] In a specific implementation, the polarization intensity ratio of the rain and fog scattering light and the vehicle reflection light can be determined according to all the polarization light intensities by the following method: first, the ratio of the vertical polarized light intensity to the parallel polarized light intensity at each sampling time point is calculated by using a real-time calculation module in the embedded processing technology in combination with all the polarization light intensities and the sampling time points; all the ratios greater than a lower threshold and less than an upper threshold are marked as the polarization intensity ratio of the rain and fog scattering light, and all the ratios less than or equal to the lower threshold or greater than or equal to the upper threshold are marked as the polarization intensity ratio of the vehicle reflection light; the upper threshold and the lower threshold refer to the values of the polarization intensity ratio for distinguishing the rain and fog scattering light and the vehicle reflection light, which can be set according to the actual measurement, and in this application, the upper threshold is set to 1.1 and the lower threshold is set to 0.9; in other embodiments, other methods can also be used for implementation, which are not limited here.

[0072] It should be noted that the polarization intensity ratio in the present application refers to the ratio of the intensity of the vertical polarized light and the intensity of the parallel polarized light, which is used to distinguish whether the signal at the current sampling time is rain and fog scattering noise or vehicle reflection signal; wherein the scattering of water droplets and water vapor particles in rain and fog to laser light is Mie scattering, and the scattering process of Mie scattering has randomness, thereby causing the energy distribution of the vertical polarization and the parallel polarization in the scattered light to tend to be uniform, therefore, the polarization intensity ratio of the rain and fog scattering light fluctuates around 1 with a small amplitude, and the reflection of the vehicle surface (such as the metal body and glass) to the laser light is directional reflection, according to the reflection law of light, the polarization state of the reflected light will retain significant directionality, thereby causing the intensity of the parallel polarized light and the intensity of the vertical polarized light to be too different, therefore, the polarization intensity ratio of the vehicle reflection light will deviate from 1 significantly.

[0073] In a specific implementation, the displacement signal of the vehicle determined by all polarization intensity ratios can be implemented in the following manner, that is, a differential filtering algorithm is used to suppress rain and fog noise of the signal segment at the sampling time corresponding to all polarization intensity ratios marked as vehicle reflection light in the echo signal of the short wave, and then a differential gain is generated for all polarization intensity ratios marked as vehicle reflection light, and a dynamic differential operation is performed on all signal segments of the vehicle reflection light after noise suppression, thereby outputting the displacement signal of the vehicle; the speed signal of the vehicle determined according to the signal of the high-speed straight-through channel received by the detector can be implemented in the following manner, that is, the signal of the high-speed straight-through channel received by the detector is quadrature demodulated to generate a quadrature local oscillator, thereby low-pass filtering the quadrature local oscillator, and performing Doppler frequency shift calculation on the instantaneous phase of the filtered signal, thereby obtaining the speed signal of the vehicle in the echo signal of the short wave; in other embodiments, other methods can also be used for implementation, which are not limited here.

[0074] It should be noted that the displacement signal in the present application is an electrical signal reflecting the position of each vehicle changing with time, the displacement signal is in the form of a digital sequence and includes a sub-displacement signal of each vehicle, and the speed signal is an electrical signal reflecting the instantaneous motion rate and direction of the vehicle, the speed signal is in the form of a digital sequence and includes a sub-speed signal of each vehicle; the displacement signal is used to reflect the motion (including direction and displacement) of each vehicle in rain and fog weather, and the speed signal is used to reflect the speed change of each vehicle on the wet and slippery road surface in rain and fog weather, so as to facilitate subsequent determination of the instantaneous speed of each vehicle.

[0075] In step 103, a plurality of frequency shifts generated by the broadening effect of Mie scattering of laser light due to rain and fog are determined based on the speed signal, and the instantaneous speed of each vehicle on the wet and slippery high-speed road surface is determined according to all frequency shifts and the wavelength of the speed signal.

[0076] In some embodiments, the plurality of frequency shifts generated by the broadening effect of Mie scattering of laser light due to rain and fog can be implemented in the following steps based on the speed signal:

[0077] determining a plurality of spectral distributions of the velocity signal;

[0078] performing centroid tracking on all the spectral distributions to obtain a plurality of frequency shifts caused by the broadening effect of the Mie scattering of laser by rain and fog.

[0079] In specific implementation, the determination of the plurality of spectral distributions of the velocity signal can be implemented by performing spectral distribution analysis on each sub-velocity signal corresponding to each vehicle in the velocity signal through fast Fourier transform, to obtain the spectral distribution corresponding to each vehicle, wherein the spectral distribution refers to the signal distribution after the conversion of the velocity signal in time domain to frequency domain, and the spectral distribution takes frequency as the horizontal axis and amplitude as the vertical axis, and is used to show the energy distribution of the sub-velocity signal of each vehicle at different frequencies; wherein the spectral distribution of each vehicle presents the characteristics of fuzzy main peak value and increased bandwidth due to the broadening effect of the Mie scattering of laser by rain and fog; in other embodiments, other methods can also be used for implementation, which are not limited here.

[0080] In specific implementation, the centroid tracking on the spectral distribution to obtain the plurality of frequency shifts caused by the broadening effect of the Mie scattering of laser by rain and fog can be implemented by selecting a spectral distribution as a selected spectral distribution, taking the range composed of all the spectral distributions greater than or equal to 0.5 times the maximum amplitude in the selected spectral distribution as the main range of the selected spectral distribution, taking the amplitude of each frequency point as the weight in the main range, and then performing weighted average centroid calculation on all the frequency points in the main range of the selected spectral distribution to obtain the weighted average frequency of the selected spectral distribution, taking the obtained weighted average frequency as the frequency shift caused by the broadening effect of the Mie scattering of laser by rain and fog, and continuing to determine the frequency shift of the remaining spectral distribution; in other embodiments, other methods can also be used for implementation, which are not limited here.

[0081] It should be noted that the frequency shift in the present application refers to the effective Doppler frequency shift caused by the vehicle movement under the interference of the Mie scattering of laser by rain and fog; the broadening effect of the Mie scattering of laser by rain and fog is essentially that the real Doppler frequency shift is surrounded by scattering noise to form a wideband energy distribution, and the weighted average centroid frequency accurately captures the real frequency shift component that dominates in the distribution by anchoring the energy center of mass in the main lobe, i.e. the energy in the main range mainly comes from the vehicle reflection signal, and the remaining energy mainly comes from the scattering noise; the weighted average centroid algorithm is essentially to calculate the “energy center of mass” in the spectral range, and the result points to the core frequency with the most concentrated energy, so the weighted average centroid frequency can be taken as the effective frequency shift under the broadening effect of rain and fog.

[0082] In some embodiments, the determination of the instantaneous speed of each vehicle on the wet and slippery highway according to all the frequency shifts and the wavelength of the velocity signal can be implemented by the following steps:

[0083] obtaining the wavelength of the velocity signal;

[0084] selecting one frequency shift as a selected frequency shift;

[0085] determining an instantaneous speed of the vehicle corresponding to the selected frequency shift according to the selected frequency shift and a wavelength of the speed signal;

[0086] continuing to determine the instantaneous speed of the vehicle corresponding to the remaining frequency shifts.

[0087] In a specific implementation, the wavelength of the speed signal can be obtained by calling a wavelength parameter of a long wave from the dual laser, and using the wavelength parameter as the wavelength of the speed signal. In other embodiments, other methods can also be used, which are not limited here.

[0088] In a specific implementation, the instantaneous speed of the vehicle corresponding to the selected frequency shift can be determined according to the selected frequency shift and the wavelength of the speed signal by bringing the selected frequency shift and the wavelength of the speed signal into a Doppler effect formula to calculate the instantaneous speed of the vehicle corresponding to the selected frequency shift. In other embodiments, other methods can also be used, which are not limited here.

[0089] It should be noted that the instantaneous speed in the present application refers to the speed and direction of each vehicle at a certain sampling time on a wet and slippery highway. When there is relative motion between the laser and the vehicle, the frequency of the reflected echo will be shifted (i.e., frequency shift), and the frequency shift size is directly related to the relative speed, and the wavelength of the laser signal is directly related to the laser speed, so the instantaneous speed of each vehicle can be obtained by the wavelength of the laser signal and the frequency shift.

[0090] In step 104, the time-varying phase caused by vehicle motion in the displacement signal is compensated and rain and fog noise is suppressed according to the instantaneous speed of each vehicle to generate a displacement reconstruction signal.

[0091] In some embodiments, as shown in FIG. 10, which is an exemplary flow chart for determining the displacement reconstruction signal in some embodiments of the present application, the time-varying phase caused by vehicle motion in the displacement signal can be compensated and rain and fog noise can be suppressed according to the instantaneous speed of each vehicle to generate a displacement reconstruction signal by using the following steps: Figure 2 First, in step 1041, a plurality of Doppler phase shifts of the displacement signal are determined according to all the instantaneous speeds.

[0092] Second, in step 1042, a plurality of time-varying phases of the displacement signal at the displacement of each vehicle are determined.

[0093]

[0094] ​Further, in step 1043, the phase change components of vehicle motion under rain and fog scattering noise are stripped from the displacement signals by all time-varying phases and all Doppler phase offsets, to obtain a plurality of residual phases of the displacement signals containing only rain and fog noise.

[0095] Finally, in step 1044, rain and fog noise suppression is performed on all residual phases of the displacement signals containing only rain and fog noise, to generate a displacement reconstruction signal.

[0096] In a specific implementation, the plurality of Doppler phase offsets of the displacement signals according to all instantaneous speeds can be determined in the following manner: a vehicle is selected as a selected vehicle, the Doppler phase offset of the sub-displacement signal of the selected vehicle is calculated by combining the instantaneous speed of the selected vehicle and the sub-displacement signal of the selected vehicle in the displacement signal according to a phase-velocity correlation method (such as a linear phase conversion model), and the Doppler phase offsets of the sub-displacement signals of the remaining vehicles are determined successively; wherein the Doppler phase offset refers to the phase change amount of the displacement signal (laser) directly related to the vehicle motion due to the motion of the vehicle relative to the laser emission source; in other embodiments, other methods can also be used for implementation, which are not limited here.

[0097] In a specific implementation, the plurality of time-varying phases of the displacement signals when determining the displacement of each vehicle can be determined in the following manner: the plurality of time-varying phases of each sub-displacement signal in the displacement signal are analyzed by Hilbert transform; wherein the time-varying phase is a characteristic describing the change of the phase of each sub-displacement signal with time, and is used to reflect the dynamic information of the displacement change with time; one sub-displacement signal corresponds to a plurality of time-varying phases; in other embodiments, other methods can also be used for implementation, which are not limited here.

[0098] In a specific implementation, the plurality of residual phases of the displacement signals containing only rain and fog noise can be obtained by stripping the phase change components of vehicle motion under rain and fog scattering noise from the displacement signals by all time-varying phases and all Doppler phase offsets in the following manner: the Doppler phase offset of the selected vehicle is subtracted from all time-varying phases corresponding to the selected vehicle, so as to remove the phase change components of the sub-displacement signal of the selected vehicle under rain and fog scattering noise, to obtain a plurality of residual phases of the sub-displacement signal of the selected vehicle; the plurality of residual phases of the sub-displacement signals of the remaining vehicles are determined successively; wherein the residual phase refers to the phase fluctuation caused only by rain and fog scattering noise and other non-motion interference factors after stripping the phase change caused by vehicle motion, and is an independent phase component for each vehicle sub-displacement signal; in other embodiments, other methods can also be used for implementation, which are not limited here.

[0099] In a specific implementation, the rain and fog noise suppression on all residual phases of the displacement signal containing only rain and fog noise to generate the displacement reconstruction signal can be implemented in the following manner: the rain and fog noise is suppressed on all residual phases of the displacement signal by using a wavelet threshold denoising algorithm, and then all residual phases are converted to displacement amounts by using a phase-distance conversion formula, and finally the displacement reconstruction signal of each vehicle is obtained; in other embodiments, other methods can also be used for implementation, which are not limited here.

[0100] It should be noted that the displacement reconstruction signal in the present application is a signal reconstructed after the interference of the sub-displacement signal of each vehicle is removed. The displacement reconstruction signal is a digital signal, includes a displacement reconstruction signal segment of each vehicle, and is used to reflect the signal of the real position of each vehicle changing with time, facilitating the subsequent determination of the observation distance of each vehicle.

[0101] In step 105, the displacement reconstruction signal is resampled at equal optical frequency intervals by using a preset beat frequency signal, and then the observation distance of each vehicle under the rain and fog refraction error is determined according to the resampled displacement reconstruction signal.

[0102] In some embodiments, the resampling of the displacement reconstruction signal at equal optical frequency intervals by using a preset beat frequency signal can be implemented in the following steps:

[0103] obtaining a preset beat frequency signal;

[0104] all voltage zero points in the beat frequency signal and time points at which the laser frequency changes by the same amount are used as sampling clocks;

[0105] the displacement reconstruction signal is non-uniformly sampled to uniform optical frequency conversion according to all sampling clocks, and the resampled displacement reconstruction signal is obtained.

[0106] In a specific implementation, the preset beat frequency signal can be obtained in the following manner: a 50m constant-temperature single-mode optical fiber delay line is used to construct a reference light path of laser, a short-wavelength laser generated by a double laser is split into two beams by a beam splitter, one of the beams is directly transmitted along the original path without any delay element (i.e., a straight-through laser signal), and the other beam is input into the optical fiber, so that the laser signal with a fixed delay through the optical fiber and the straight-through laser signal are mixed in a balanced photodetector to generate a beat frequency signal determined only by the length of the optical fiber; wherein neither of the two split beams is used to irradiate vehicles, and the beat frequency signal refers to a local reference light with the same source but a fixed optical path difference, and an electrical signal generated by the difference frequency after the light mixing in the balanced photodetector; in other embodiments, other methods can also be used for implementation, which are not limited here.

[0107] In a specific implementation, all the voltage zero-crossing points in the beat frequency signal and the time points at which the laser frequency changes by the same amount can be realized by the following method: the beat frequency signal is input into a high-speed voltage comparator, and all the zero-crossing points at which the voltage of the beat frequency signal changes from positive to negative or from negative to positive (i.e., the moment when the zero point is crossed) are marked. Then, the time interval between two adjacent pulse signals is recorded by a counter, and the actual change amount of the laser frequency in each time interval is calculated in combination with the fixed change amount of the laser frequency per second in the laser frequency modulation. Finally, the adjacent zero-crossing points at which the change amount of the laser frequency is completely equal (i.e., the equal optical frequency) are selected, and these zero-crossing points are used as the sampling clock. The sampling clock refers to the time marker and trigger signal for sampling the control signal. In other embodiments, other methods can also be used to realize this, which are not limited here.

[0108] It should be noted that the traditional time domain sampling (fixed time interval) will cause the non-uniform sampling interval in the optical frequency domain due to the nonlinearity of the laser frequency modulation. The zero-crossing points at which the change amount of the laser frequency is completely equal mark the time points at which the optical frequency domain is uniform. Triggering the resampling of the displacement reconstruction signal at these time points can ensure that the sampling point interval of the displacement reconstruction signal in the optical frequency domain is strictly equal, thereby laying a foundation for subsequent elimination of the frequency modulation error and accurate calculation of the observation distance.

[0109] In a specific implementation, the conversion of the non-uniform sampling of the displacement reconstruction signal to the uniform optical frequency according to all the sampling clocks can be realized by the following method: the digital-to-analog converter is controlled by all the sampling clocks of the beat frequency signal to sample the displacement reconstruction signal at each sampling clock in real time, thereby generating a discrete resampled sequence that is uniformly distributed in the optical frequency domain, and obtaining the resampled displacement reconstruction signal. In other embodiments, other methods can also be used to realize this, which are not limited here.

[0110] It should be noted that the reference light path is constructed by a fixed optical fiber delay line (50 m). When the laser is frequency-modulated, the time at which the optical signal passing through the delay line and the straight-through optical signal reaches the detector is different, resulting in a difference in the frequency of the mixed frequency of the delay line optical signal and the straight-through optical signal on the detector at the same time, i.e., a beat frequency is generated. This beat frequency directly reflects the laser frequency modulation rate, and the physical optical path difference of the reference light path (the optical path difference value between the straight-through light path and the delay light path in the reference light path) linearly converts the laser frequency modulation rate into a stable beat frequency signal. Therefore, when the beat frequency signal crosses zero, it indicates that the laser frequency has changed by a fixed optical frequency interval. At this time, triggering the resampling of the displacement reconstruction signal can convert the non-uniform displacement signal of the displacement reconstruction signal in the time domain into a discrete signal uniformly distributed in the optical frequency domain, thereby avoiding the sampling distortion of the moving target.

[0111] In some embodiments, the observation distance of each vehicle under the rain and fog refraction error can be determined according to the resampled displacement reconstruction signal by the following steps:

[0112] determining a plurality of dominant peak frequencies of the resampled displacement reconstruction signal;

[0113] determining the observation distance of each vehicle under rain and fog refraction error according to all the dominant peak frequencies.

[0114] In a specific implementation, the determining of the plurality of dominant peak frequencies of the resampled displacement reconstruction signal can be implemented in the following manner: a Blackman window is applied to the resampled displacement reconstruction signal through fast Fourier transform to enhance sidelobe suppression, a multi-target spectrum overlap scenario is adapted, a mixed spectrum is obtained, and then a plurality of dominant peaks of the mixed spectrum are identified through an adaptive threshold and peak-valley detection method to obtain the plurality of dominant peak frequencies; wherein the dominant peaks are discretely distributed on the spectrum due to the distance difference of the vehicles (different distances correspond to different beat frequencies), and one vehicle corresponds to one dominant peak frequency; in other embodiments, other methods can also be used for implementation, which are not limited here.

[0115] In a specific implementation, the determining of the observation distance of each vehicle under rain and fog refraction error according to all the dominant peak frequencies can be implemented in the following manner: a dominant peak frequency is selected as a selected dominant peak frequency, the selected dominant peak frequency is brought into a frequency-distance mapping formula based on frequency-modulated continuous wave, the observation distance of the vehicle corresponding to the selected dominant peak frequency is calculated, and the observation distances of the vehicles corresponding to the remaining dominant peak frequencies are determined; in other embodiments, other methods can also be used for implementation, which are not limited here.

[0116] It should be noted that the resampled displacement reconstruction signal is a mixed signal, but the sub-displacement signals of multiple vehicles have formed distance discreteness through space-time resolution in the original echo signal (i.e., different vehicle distances correspond to different beat frequencies), so after resampling in the optical frequency domain, this discreteness is manifested as a plurality of distinguishable dominant peaks in the mixed spectrum; secondly, since the resampling ensures the uniformity of the displacement reconstruction signal in the optical frequency domain, and the displacement reconstruction in the foregoing has suppressed rain and fog noise, the value calculated by the frequency-distance mapping formula directly corresponds to the observation distance of the vehicle, and thirdly, the discreteness of the dominant peak frequencies is matched with the vehicle order in the previous space-time resolution, for example, the first dominant peak in the spectrum corresponds to the first vehicle in the time window; the observation distance refers to the actual spatial distance between the vehicle and the detection laser system, which is used to quantify the displacement of the vehicle in rain and fog weather, so as to facilitate the subsequent determination of the dynamic speed of the vehicle.

[0117] In step 106, the time difference of each vehicle passing through the baseline distance is obtained, the speed deviation caused by rain and fog refraction is corrected according to all the time differences and all the observation distances, and then the dynamic speed of each vehicle on the highway in rain and fog weather is obtained.

[0118] In practice, the time difference between each vehicle's distance from the baseline can be obtained as follows: Two laser detection sections with a known distance are set up along the vehicle's direction of travel in the highway monitoring area. The distance between these two laser detection sections is the baseline distance. Timing is triggered using the real-time signal from the channel containing the long-wavelength laser in the dual-laser system. (See reference...) Figure 3 As shown in the figure, this figure is an engineering schematic diagram of obtaining the time difference of the vehicle passing the baseline distance in some embodiments of this application. When the front end of the vehicle passes the first section, the Doppler frequency shift signal of the echo of the long-wave laser increases sharply, triggering the timing module to record the moment (first moment). When the front end of the same vehicle passes the second section, the above channel detects the frequency shift signal jump again and records the moment (second moment). The difference between the second moment and the first moment is used as the time difference of the vehicle passing the baseline distance. The baseline distance is the distance between two laser detection sections with known spacing.

[0119] In some embodiments, the speed deviation caused by rain and fog refraction is corrected based on all time differences and all observation distances to obtain the dynamic speed of each vehicle on a highway in rainy or foggy weather. This can be achieved by the following steps:

[0120] Determine the air refractive index under rainy and foggy weather conditions;

[0121] All observation distances are corrected based on the air refractive index.

[0122] The dynamic speeds of each vehicle on the highway in rainy or foggy weather were determined based on all corrected observation distances and time differences.

[0123] In practice, the air refractive index under rainy and foggy weather can be determined in the following way: the air refractive index under rainy and foggy weather can be obtained by using real-time meteorological sensors and combining them with existing atmospheric optical parameter calculation formulas.

[0124] In specific implementation, the correction of all observation distances based on the air refractive index can be achieved in the following way: all observation distances and air refractive indices are used as known operands and substituted into the rain and fog correction formula to obtain multiple true observation distances after eliminating rain and fog refraction errors; the determination of the dynamic speed of each vehicle on the highway in rainy and foggy weather based on all corrected observation distances and all time differences can be achieved in the following way: all corrected observation distances and all time differences are used as known operands and substituted into the dynamic speed calculation formula to obtain the dynamic speed of each vehicle on the highway in rainy and foggy weather; other methods can also be used in other embodiments, which are not limited here.

[0125] It should be noted that for any vehicle, the real observation distance of the vehicle at two time points when the vehicle passes through the baseline is selected, so as to obtain the dynamic speed of the vehicle through the above two observation distances and the time difference of the two time points; secondly, the rain and fog correction formula refers to a formula for correcting the light refraction effect of rain and fog weather, and the formula is based on the optical path equivalence principle, that is, the product of the propagation distance of light in the medium and the refractive index is equal to the observation optical path to establish the correction formula.

[0126] In addition, another aspect of the present application, in some embodiments, the present application provides a laser dynamic speed measurement system, referring to Figure 4 The figure is a structural schematic diagram of a laser dynamic speed measurement system according to some embodiments of the present application, which includes a collection module 401, a processing module 402 and an execution module 403, which are described as follows:

[0127] The collection module 401 is mainly used for collecting the echo signal containing rain and fog scattering noise in the reflected laser beam of the vehicle in the present application;

[0128] The processing module 402 is used for detecting and separating the polarization components of rain and fog scattering light and vehicle reflected light by polarization diversity of the echo signal in the present application, so as to obtain the speed signal and displacement signal of the vehicle;

[0129] It should be noted that the processing module 402 is also used for determining the multiple frequency shifts caused by the broadening effect of rain and fog Mie scattering of laser based on the speed signal, and determining the instantaneous speed of each vehicle on the wet and slippery highway according to all frequency shifts and the wavelength of the speed signal;

[0130] In addition, it should be noted that the processing module 402 is also used for stripping and compensating the time-varying phase caused by vehicle movement in the displacement signal according to the instantaneous speed of each vehicle and suppressing rain and fog noise, and generating a displacement reconstruction signal;

[0131] In addition, it should be noted that the processing module 402 is also used for equalizing the optical frequency interval of the displacement reconstruction signal by the preset beat frequency signal, and then determining the observation distance of each vehicle under the rain and fog refraction error according to the resampled displacement reconstruction signal;

[0132] The execution module 403 is mainly used for obtaining the time difference of each vehicle passing through the baseline distance, correcting the speed deviation caused by rain and fog refraction according to all time differences and all observation distances, and then obtaining the dynamic speed of each vehicle on the highway in rain and fog weather.

[0133] In addition, the present application further provides a computer device, comprising a memory and a processor, the memory stores codes, and the processor is configured to acquire the codes and execute the rain and fog weather highway vehicle laser dynamic speed measurement method.

[0134] In some embodiments, with reference to Figure 5 The figure is a structural schematic diagram of a computer device for implementing the rain and fog weather highway vehicle laser dynamic speed measurement method according to some embodiments of the present application. The rain and fog weather highway vehicle laser dynamic speed measurement method in the above embodiments can be implemented by the computer device shown in the figure, which comprises at least one processor 501, a communication bus 502, a memory 503 and at least one communication interface 504. Figure 5 The processor 501 can be a general central processing unit (CPU) or an application-specific integrated circuit (ASIC).

[0135] The processor 501 can be a general central processing unit (CPU) or an application-specific integrated circuit (ASIC).

[0136] The communication bus 502 can be used to transmit information between the above components.

[0137] The memory 503 can be a read-only memory (ROM) or other types of static storage devices that can store static information and instructions, a random access memory (RAM) or other types of dynamic storage devices that can store information and instructions, an electrically erasable programmable read-only memory (EEPROM), a compact disc read-only memory (CD-ROM) or other optical disk storage, an optical disk storage (including a compact disk, a laser disk, an optical disk, a digital versatile disk, a blue-ray disk, etc.), a magnetic disk or other magnetic storage device, or any other medium that can be used to carry or store desired program codes in the form of instructions or data structures and can be accessed by a computer, but is not limited to this. The memory 503 can exist independently and be connected to the processor 501 through the communication bus 502. The memory 503 can also be integrated with the processor 501.

[0138] The memory 503 is configured to store program codes for implementing the solutions of the present application, and the processor 501 is configured to execute the program codes stored in the memory 503. The program codes can include one or more software modules. The methods used in the above-described embodiments can be implemented by the processor 501 and one or more software modules in the program codes in the memory 503.

[0139] The communication interface 504 is configured to communicate with other devices or communication networks, such as an Ethernet, a radio access network (RAN), a wireless local area network (WLAN), etc., using any transceiver-like device.

[0140] In specific implementations, as an example, the computer device can include multiple processors, each of which can be a single-CPU processor or a multi-CPU processor. The processor herein can refer to one or more devices, circuits, and / or processing cores for processing data (e.g., computer program instructions).

[0141] The computer device described above can be a general-purpose computer device or a special-purpose computer device. In specific implementations, the computer device can be a desktop computer, a laptop computer, a network server, a personal digital assistant (PDA), a mobile phone, a tablet computer, a wireless terminal device, a communication device, or an embedded device. The embodiments of the present application do not limit the type of the computer device.

[0142] In addition, the present application also provides a computer-readable storage medium, which stores a computer program. The computer program is executed by a processor to implement the rain and fog weather highway vehicle laser dynamic speed measurement method described above.

[0143] Although the preferred embodiments of the present application have been described, those skilled in the art who are informed of the basic inventive concept can make additional changes and modifications to the embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0144] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalent technologies, the present application also intends to include these modifications and variations.

Claims

1. A method of laser dynamic speed measurement of a highway vehicle in rain and fog weather, wherein, The method for detecting the moving vehicles on the highway by the dual laser generated probe light source in advance, characterized in that the method comprises the following steps: Collecting the echo signal of the laser beam reflected by the vehicle containing the rain and fog scattering noise; Polarization diversity detection of the echo signal separates the polarization components of the rain and fog scattering light and the vehicle reflected light, and obtains the speed signal and the displacement signal of the vehicle; Determining the multiple frequency shifts caused by the broadening effect of the rain and fog Mie scattering of the laser based on the speed signal, and determining the instantaneous speed of each vehicle on the wet and slippery highway surface according to all the frequency shifts and the wavelength of the speed signal; According to the instantaneous speed of each vehicle, the time-varying phase caused by the vehicle movement in the displacement signal is compensated and the rain and fog noise is suppressed, and the displacement reconstruction signal is generated; Through the preset beat frequency signal, the displacement reconstruction signal is resampled at equal optical frequency intervals, and then the observation distance of each vehicle under the rain and fog refraction error is determined according to the resampled displacement reconstruction signal; Obtaining the time difference of each vehicle passing through the baseline distance, correcting the speed deviation caused by the rain and fog refraction according to all the time differences and all the observation distances, and then obtaining the dynamic speed of each vehicle on the highway in the rain and fog weather.

2. The method of claim 1, wherein, The polarization diversity detection of the echo signal separates the polarization components of the rain and fog scattering light and the vehicle reflected light, and obtains the speed signal and the displacement signal of the vehicle, specifically comprising: Separating the echo signal into a high-speed straight-through channel and different polarization state transmission channels and receiving by a detector; Determining the multiple polarization intensities in each transmission channel; Determining the polarization intensity ratio of the rain and fog scattering light and the vehicle reflected light according to all the polarization intensities; Determining the displacement signal of the vehicle through all the polarization intensity ratios; Determining the speed signal of the vehicle according to the signal of the high-speed straight-through channel received by the detector.

3. The method of claim 1, wherein, Determining the multiple frequency shifts caused by the broadening effect of the rain and fog Mie scattering of the laser based on the speed signal, specifically comprising: Determining the multiple spectral distributions of the speed signal; Centroid tracking is performed on all the spectral distributions to obtain the multiple frequency shifts caused by the broadening effect of the rain and fog Mie scattering of the laser.

4. The method of claim 1, wherein, Determining the instantaneous speed of each vehicle on the wet and slippery highway surface according to all the frequency shifts and the wavelength of the speed signal, specifically comprising: Obtaining the wavelength of the speed signal; Selecting one frequency shift as a selected frequency shift; Determining the instantaneous speed of the vehicle corresponding to the selected frequency shift according to the selected frequency shift and the wavelength of the speed signal; Continue to determine the instantaneous speed of the vehicle corresponding to the remaining frequency shifts.

5. The method of claim 1, wherein, According to the instantaneous speed of each vehicle, the time-varying phase caused by the vehicle movement in the displacement signal is compensated and the rain and fog noise is suppressed, and the displacement reconstruction signal is generated, specifically comprising: Determining the multiple Doppler phase offsets of the displacement signal according to all the instantaneous speeds; Determining the multiple time-varying phases of the displacement signal when each vehicle moves; Removing the phase change component of the vehicle movement from the displacement signal through all the time-varying phases and all the Doppler phase offsets to obtain the multiple residual phases of the displacement signal containing only rain and fog noise; Rain and fog noise suppression is performed on all the residual phases of the displacement signal containing only rain and fog noise to generate the displacement reconstruction signal.

6. The method of claim 1, wherein, The equal optical frequency interval resampling of the displacement reconstruction signal by the preset beat frequency signal specifically comprises: obtaining a preset beat frequency signal; all voltage zero-crossing points in the beat frequency signal are taken as sampling clocks, and the laser frequency changes by the same amount; according to all the sampling clocks, the displacement reconstruction signal is non-uniformly sampled to uniform optical frequency conversion to obtain a resampled displacement reconstruction signal.

7. The method of claim 1, wherein, According to the resampled displacement reconstruction signal, the observation distance of each vehicle under the rain and fog refraction error specifically comprises: determining the main peak frequency of the resampled displacement reconstruction signal; according to all the main peak frequencies, the observation distance of each vehicle under the rain and fog refraction error is determined.

8. The method of claim 1, wherein, According to all the time differences and all the observation distances, the speed deviation caused by rain and fog refraction is corrected, and then the dynamic speed of each vehicle on the highway in rain and fog weather is obtained specifically comprises: determining the air refractive index under rain and fog weather; according to the air refractive index, all the observation distances are corrected; according to the corrected all observation distances and all time differences, the dynamic speed of each vehicle on the highway in rain and fog weather is determined.

9. The method of claim 1, wherein, The Cassegrain telescope is used to collect the echo signal containing rain and fog scattering noise in the laser beam reflected by the vehicle.

10. A laser dynamic speed measurement system characterized by, It comprises: a collection module for collecting echo signals containing rain and fog scattering noise in the laser beam reflected by the vehicle; a processing module for detecting and separating the polarization components of rain and fog scattering light and vehicle reflected light by polarization diversity detection on the echo signal to obtain the speed signal and displacement signal of the vehicle; the processing module is also used for determining a plurality of frequency shifts caused by the broadening effect of rain and fog Mie scattering of laser based on the speed signal, and determining the instantaneous speed of each vehicle on the wet and slippery highway surface according to all the frequency shifts and the wavelength of the speed signal; the processing module is also used for stripping and compensating the time-varying phase caused by vehicle movement in the displacement signal according to the instantaneous speed of each vehicle and suppressing rain and fog noise to generate a displacement reconstruction signal; the processing module is also used for resampling the displacement reconstruction signal by a preset beat frequency signal, and then determining the observation distance of each vehicle under the rain and fog refraction error according to the resampled displacement reconstruction signal; an execution module for obtaining the time difference of each vehicle passing through the baseline distance, correcting the speed deviation caused by rain and fog refraction according to all the time differences and all the observation distances, and then obtaining the dynamic speed of each vehicle on the highway in rain and fog weather.

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