A laser remote sensing type road surface state measuring system and measuring method

Abstract

The application discloses a laser remote sensing type road surface state measuring system and a measuring method, the measuring system comprises an optical measuring module, the optical measuring module is used for emitting measuring light of a specific wavelength to irradiate a road surface target object and can receive reflected light reflected by the road surface target object; a weak signal detection module, the weak signal detection module is used for signal processing of an electric signal converted by the received reflected light reflected by the road surface target object; and a digital signal processing module, the digital signal processing module is used for processing of the electric signal after signal processing. The application obtains a road surface spectrum signal through the optical measuring module, and through signal processing of the weak signal detection module and the digital signal processing module, road surface states are recognized, and snow, ice or water film thickness of the road surface is measured.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of traffic meteorological monitoring, in particular to a laser remote sensing type road surface state measuring system and measuring method. BACKGROUND

[0002] With the rapid development of transportation industry, the influence of weather conditions on transportation is more and more extensive, and the adverse weather conditions bring huge losses to transportation, and even threaten people's life and property safety. Meteorology is one of the important factors affecting road traffic safety. According to the statistical research on the accident data in China, a large number of road traffic accidents are directly or indirectly related to meteorological conditions. In the large-scale ice and snow weather that often occurs in China, the injury and death rate of highway traffic accidents increases, and the accident rate is ten times that of normal conditions. Among them, the meteorological conditions such as snow, water, ice, frost and high temperature change the physical properties of the road surface, which leads to a significant decrease in the friction coefficient, thereby endangering the safety of driving. Its direct influence mainly manifests in changing the physical properties of the road surface, the observation of the line of sight, the safety of the vehicle itself, etc., thereby causing traffic accidents. According to statistics, the probability of traffic accidents in the ice and snow road surface, water road surface and normal dry road surface is 4.2:1.6:1, and this phenomenon is even more serious in cold regions. Therefore, timely and accurate road surface state information has become a key component of decision support for traffic control departments.

[0003] The deficiency of the prior art is that a large number of currently used embedded road surface state sensors damage the road surface during installation, the service life depends on the ground subsidence caused by traffic flow and the road maintenance cycle, the actual use cost is high, and it is difficult to be popularized on a large scale. Moreover, the embedded type is generally installed on the road shoulder and the road surface, and the installation process and the later maintenance are very difficult and the cost is high. In addition, the embedded detection method can only detect a small area (a single point), and is more suitable for use in places where icing is more likely to occur. If a larger area needs to be detected and the damage to the road surface and the influence on traffic during installation and equipment maintenance are to be avoided, a non-contact remote sensing type road surface state measuring sensor needs to be used. SUMMARY

[0004] The purpose of the present application is to overcome the deficiencies of the prior art, and to achieve the above purpose by using a laser remote sensing type road surface state measuring system and measuring method to solve the problems raised in the background art.

[0005] A laser remote sensing type road surface state measuring system, the measuring system comprises:

[0006] An optical measurement module for emitting a measurement laser of a specific wavelength to irradiate a road surface target object, and capable of receiving reflected light reflected by the road surface target object and converting the reflected light into an electrical signal through photoelectric conversion;

[0007] Weak signal detection module, the weak signal detection module is used for signal processing to the electric signal that is photoelectrically converted in optical measurement module;

[0008] Digital signal processing module, the digital signal processing module is used for analog-digital conversion processing and algorithm inversion to the electric signal after signal processing.

[0009] As a further technical scheme of the application: the optical measurement module includes several laser modules and detector modules, and the several laser modules and detector modules form an integrated structure.

[0010] As a further technical scheme of the application: the light source wavelength of the several laser modules is 1310nm, 1440nm, and 1550nm wavelength, and the laser module is composed of a laser diode and an optical lens.

[0011] As a further technical scheme of the application: the detector module uses an indium gallium arsenide photodetector, and the front end of the detector module is provided with a filter and a convex lens.

[0012] As a further technical scheme of the application: the weak signal detection module includes a preamplifier, a phase-sensitive detector connected to the preamplifier, a low-pass filter connected to the phase-sensitive detector, and a pulse generator.

[0013] As a further technical scheme of the application: the digital signal processing module includes a DSP module and an AD conversion module.

[0014] Another aspect of the technical scheme: a measurement method of a laser remote sensing type road surface state measurement system, the measurement method applies a laser remote sensing type road surface state measurement system according to any one of the above, and the measurement method steps are:

[0015] The several laser modules emit the emitted light after the light source modulation of the pulse generator collimated by the lens to irradiate the target object;

[0016] Then the light reflection signal reflected by the target object is detected by the detector module to be photoelectrically converted into an electric signal;

[0017] The electric signal after photoelectric conversion is signal-processed by the weak signal detection module;

[0018] According to the signal after signal processing, the digital signal processing module is input, analog-digital conversion processing and algorithm inversion are carried out, wherein the algorithm inversion includes road surface state type judgment and target object thickness data calculation according to the road surface state type.

[0019] As a further technical scheme of the present application: the specific steps of signal processing of the photoelectric converted electrical signal through the weak signal detection module include:

[0020] Firstly, the probe module converts the detected optical signal into an electrical signal, and then the signal is amplified through a preamplifier, and phase-sensitive detection is performed by using a pulse generator and a phase-sensitive detector to complete demodulation of the measurement signal of the reflected light;

[0021] The demodulated signal is filtered through a low-pass filter and input into a digital signal processing module.

[0022] As a further technical scheme of the present application: the specific steps of signal processing according to the signal input into the digital signal processing module, analog-digital conversion processing and algorithm inversion, wherein the algorithm inversion includes performing road surface state type judgment and calculating thickness data of the target object according to the road surface state type include:

[0023] In the dry state, the measurement signal is converted by the AD conversion module, and three waveband reflection signals I 1310nm , I 1440nm and I 1550nm are extracted and normalized to obtain signals I r(1310nm) , I r(1440nm) and I r(1550nm) .

[0024] I r(1310nm) , I r(1440nm) and I r(1550nm) are input into a DSP module for calculation to obtain ln(I r(1310nm) / I r(1440nm) ), ln(I r(1440nm) / I r(1550nm) ) and ln(I r(1310nm) / I r(1550nm) ).

[0025] When ln(I r(1310nm) / I r(1440nm) ), ln(I r(1440nm) / I r(1550nm) ) and ln(I r(1310nm) / I r(1550nm) ) are all greater than 0.9, it is judged that the current reflection signal is strong and the reflection is not sensitive to the light frequency, and the road surface state type is determined to be the dry state.

[0026] When I 1310nm >0.9 and I 1550nm <0.2, according to the absorption intensity characteristics of snow to different wavelengths of laser, it is judged that the road surface state type is the snow state, and the snow thickness calculation formula: D snow =K snow *I 1310nm +B is used.snow Calculate the snow film thickness, wherein K snow and B snow are obtained from calibration experiments;

[0027] When ln(I r(1440nm) / I r(1550nm) )>0, the road surface state type is determined to be ice state, and the ice film thickness is calculated by the ice thickness calculation formula: D ice =K ice ln(I r(1440nm) / I r(1550nm) )+B ice , wherein K ice , B ice are obtained from calibration experiments;

[0028] When ln(I r(1440nm) / I r(1550nm) )<0, the road surface state type is determined to be water state, and the water film thickness is calculated by the water thickness calculation formula: D water =K water ln(I r(1440nm) / I r(1550nm) )+B water , wherein K water , B water are obtained from calibration experiments.

[0029] Compared with the prior art, the present application has the following technical effects:

[0030] (1) The present application adopts a non-contact remote sensing infrared optical measurement system to measure the reflected spectrum of the measured road surface, and through a related algorithm, not only can various road surface states such as dry, snow, water, and ice be accurately identified, but also the water film and ice film thickness can be quantitatively measured, providing necessary parameters for friction inversion;

[0031] (2) In the optical measurement system of the present application, the optical measurement module adopts high-speed pulse modulation, and the band-pass filter circuit in the signal conditioning circuit can effectively filter out direct current noise signals and signals of different modulation light frequencies; at the same time, a filter is installed in front of the detector module, avoiding the influence of various stray light or sunlight reflection in the environment on the measurement, and improving the stability of the system;

[0032] (3) The optical measurement module of the present application adopts an active remote sensing measurement method, is installed on a stand beside the measured road, and performs remote measurement, without affecting the normal state of the vehicle operation and the road, has strong practicability, and is suitable for fixed-point or mobile measurement of the surface state of highways, airport runways, etc.;

[0033] (4) The present application realizes non-contact accurate measurement of the road surface state, and has the advantages of fast response speed, high recognition rate, and high precision. Attached Figure Description

[0034] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings:

[0035] Figure 1 This is a schematic diagram of the structure of a laser remote sensing road condition measurement system according to an embodiment of this application;

[0036] Figure 2 Near-infrared absorption spectra of ice and water from embodiments disclosed in this application;

[0037] Figure 3 The reflectance spectrum of snow is shown in the embodiment disclosed in this application.

[0038] Figure 4 This is a schematic diagram illustrating the principle of ice and water thickness measurement according to an embodiment disclosed in this application. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] Please refer to Figure 1 In this embodiment of the invention, a laser remote sensing road condition measurement system is provided, the measurement system including an optical measurement module, a weak signal detection module, and a digital signal processing module;

[0041] An optical measurement module is used to emit measurement lasers of different specific wavelengths to illuminate road surface targets and to receive reflected light from the road surface targets. In a specific embodiment, the optical measurement module includes three laser modules and one detector module, which are combined and installed to form an integrated measurement structure. Lenses are provided in the three laser modules and the detector module, and the optical axes of the lenses are parallel.

[0042] Furthermore, the light source wavelengths of the three laser modules are set to 1310nm, 1440nm, and 1550nm, and each laser module consists of a laser diode and an optical lens.

[0043] Specifically, the detector module uses an indium gallium arsenide photodetector, and a filter and a convex lens are installed at the front end of the detector module. In a specific implementation, the detector module consists of a lens, an optical signal detector, and a filter. The filter installed in front of the optical signal detector focuses the light onto the surface of the optical signal detector after passing through the convex lens at the receiving end. The purpose of installing the filter in front of the optical signal detector is to filter out stray light that is not in the wavelength range of the light source.

[0044] A weak signal detection module is included, which processes the electrical signal converted from the reflected light from road surface targets. In this embodiment, the weak signal detection module includes a preamplifier, a phase-sensitive detector connected to the preamplifier, a low-pass filter connected to the phase-sensitive detector, and a pulse generator. The pulse generator is connected to the laser modules and generates pulses to control all three laser modules. The emitted laser pulses have a frequency of 4kHz and are also connected to the phase-sensitive detector for weak signal detection.

[0045] The reflected light under three different bands is photoelectrically converted by the detector module and then amplified by the weak signal detection module. First, it is preamplified and filtered by the preamplifier. Then, the signal generated by the phase-sensitive detector and pulse generator is phase-sensitively detected. After being filtered by the low-pass filter, it is input into the digital signal processing module.

[0046] The digital signal processing module includes a DSP module for modulating the light source and an AD conversion module.

[0047] In this embodiment, the specific process is as follows: the digital signal processing module can control the pulse generator to generate a 4k square wave signal as a modulation signal to modulate the light source, overcoming the influence of stray light from the outside during the measurement process; the signal after being filtered by the low-pass filter is obtained, and analog-to-digital conversion is performed under the control of the DSP module, and AD conversion is performed by the AD conversion module. Through the corresponding algorithm processing of the DSP module, the digitized reflected light intensity is obtained. The light intensity signal is processed by the corresponding inversion algorithm model in the system software to obtain the final measurement results of the road surface state and the thickness of the ice water film, and then output.

[0048] Another technical solution: A measurement method for a laser remote sensing road condition measurement system, wherein the measurement method uses the aforementioned measurement system, and the specific steps of the measurement method are as follows:

[0049] First, the laser light, modulated by the pulse generator light source, is emitted through three pre-set laser modules. Simultaneously, the light is collimated by a lens and then illuminates the target object on the ground. The target object is usually ground water, snow, or ice.

[0050] Then, the detector module, which is set together with the three laser modules, detects and receives the light reflection signals reflected by targets such as ground water, snow, and ice, and converts the light reflection signals into electrical signals through photoelectric conversion.

[0051] The electrical signal after photoelectric conversion is then processed by a weak signal detection module. The specific steps include:

[0052] First, the detector module converts the detected optical signal into an electrical signal, which is then amplified by a preamplifier. A pulse generator and a phase-sensitive detector are then used for phase-sensitive detection to demodulate the reflected light measurement signal. The demodulated signal is then filtered by a low-pass filter and input into the digital signal processing module.

[0053] The processed signal is input into the digital signal processing module for analog-to-digital conversion and algorithm inversion. Algorithm inversion includes determining the road surface condition type and calculating the target object's thickness based on that type. Specific steps include:

[0054] In a specific implementation, under dry conditions, the measured signal is converted by the AD conversion module, and the reflected signals I of three bands are extracted. 1310nm I 1440nm and I 1550nm Then, normalization is performed to obtain signal I. r(1310nm) I r(1440nm) and I r(1550nm) ;

[0055] The normalization process specifically involves measuring the dry road surface, taking the average value, and obtaining I. 1310nm(干燥) I 1440nm(干燥) and I 1550nm(干燥) The data is then stored in the DPS module for subsequent measurement of the signal I. r(1310nm) I r(1440nm) and I r(1550nm) Through the formula: and Perform normalization processing;

[0056] I r(1310nm) I r(1440nm) and I r(1550nm) The input is processed by the DSP module to obtain ln(I) r(1310nm) / I r(1440nm) ), ln(I r(1440nm) / I r(1550nm) ) and ln(I r(1310nm) / I r(1550nm) );

[0057] When ln(I r(1310nm) / I r(1440nm) ), ln(Ir(1440nm) / I r(1550nm) ) and ln(I r(1310nm) / I r(1550nm) ) are greater than 0.9, then the current reflection signal is strong, and the reflection is not sensitive to the light frequency, and the road surface state type is determined to be dry state;

[0058] When I 1310nm >0.9 and I 1550nm <0.2, according to the absorption intensity characteristics of snow to different wavelengths of laser, the road surface state type is determined to be snow state, and the snow thickness is calculated by the snow thickness calculation formula: D snow =K snow *I 1310nm +B snow , wherein K snow and B snow are obtained from the calibration experiment;

[0059] When ln(I r(1440nm) / I r(1550nm) )>0, the road surface state type is determined to be ice state, and the ice thickness is calculated by the ice thickness calculation formula: D ice =K ice ln(I r(1440nm) / I r(1550nm) )+B ice , wherein K ice , B ice are obtained from the calibration experiment;

[0060] When ln(I r(1440nm) / I r(1550nm) )<0, the road surface state type is determined to be water state, and the water thickness is calculated by the water thickness calculation formula: D water =K water ln(I r(1440nm) / I r(1550nm) )+B water , wherein K water , B water are obtained from the calibration experiment.

[0061] Working principle:

[0062] First, in the case of snow on the road, when the snow accumulation reaches a certain thickness, the light is difficult to penetrate the snow layer, and the snow identification is carried out by measuring the reflection spectrum of the snow, and the snow depth measurement technology research is carried out. As shown in FIG. 1, it is a reflection spectrum diagram of the snow layer. Figure 3

[0063] ​According to the spectral reflectivity data of snow, it can be obtained that the reflectivity of snow is at a very high level of about 95% in the visible light band, and after entering the near infrared band, its reflectivity coefficient rapidly decreases and drops to a very low level of about 2% near 1.5 um, that is, the absorption ability increases with the increase of wavelength in the near infrared band, and reaches the extreme value of the absorption coefficient at 1.5 um. Therefore, under the condition of snow, the reflectivity R snow near 1.3 um is set to 90%. At the same time, on the spectrum near 1.3 um, snow has a strong reflection efficiency, reaching about 45%, and the reflected light intensity has a certain correlation with the thickness:

[0064] D snow = K snow *I 1310nm +B snow

[0065] D snow is the thickness of snow, I 1310nm is the reflected intensity of 1.3 um band light, K snow , B snow are the slope and intercept of the formula, which can be determined by calibration experiment.

[0066] The formula is used for measuring the thickness of snow.

[0067] Secondly, in the case of road surface water and ice accumulation, such as Figure 2 The absorption spectrum of ice and water in the 0.95-2.0 um band can be obtained. From the visible light band to 1.3 um, the absorption ability of ice and water to light is very weak, but water and ice have an absorption peak near 1.44 um and 1.55 um respectively, and the width of the two absorption peaks is relatively narrow, about 0.3 um, and the peak values are obviously different. Narrowband monochromatic light near 1.44 um and 1.55 um can be used to identify and measure ice and water.

[0068] As shown in Figure 4 , the diagram is a schematic diagram of ice and water thickness measurement. In the diagram, the incident light intensity I0, the reflected light intensity I r , the absorption coefficient of ice or water α, x is the travel of light in the medium, h is the thickness of the film, k s represents the reflectivity of ice or water surface, and p b represents the reflectivity of the road surface, then the measured reflected light intensity I r(x,λ1) of the first band is:

[0069] I r(x,λ1) = I 0λ1 k s p b exp(-α λ1 2x);

[0070] In this embodiment, three wave bands are used to measure the light source, and the reflected light intensity of the other two wave bands is I r(x,λ2) and I r(x,λ3) , we can get:

[0071]

[0072] where h=x*cos θ, and after simplification we get:

[0073]

[0074] This formula is used to measure the thickness of water and ice.

[0075] Although embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, replacements and changes can be made to these embodiments without departing from the principles and spirit of the present application, the scope of the present application is defined by the appended claims and their equivalents, and all should be included in the protection scope of the present application.

Claims

1. A laser remote sensing road surface condition measurement system, characterized by, The measurement system comprises: An optical measurement module for emitting measurement laser of specific wavelength to irradiate the road target object and capable of receiving reflected light reflected by the road target object and photoelectrically converting the reflected light into electrical signal; The optical measurement module comprises a plurality of laser modules and detector modules, and the plurality of laser modules and detector modules form an integrated structure; The light source wavelength of the plurality of laser modules is 1310nm, 1440nm and 1550nm, and each laser module is composed of laser diode and optical lens; The detector module adopts indium gallium arsenide photodetector, and a filter and a convex lens are arranged at the front end of the detector module; A weak signal detection module for signal processing of the electrical signal photoelectrically converted by the optical measurement module; A digital signal processing module for analog-digital conversion processing and algorithm inversion of the electrical signal after signal processing; According to the signal after signal processing, the digital signal processing module is inputted for analog-digital conversion processing and algorithm inversion, wherein the algorithm inversion comprises road state type judgment and specific steps of calculating thickness data of the target object according to the road state type, which comprises: In the dry state, the measurement signal is converted by the AD conversion module to extract three waveband reflection signals , and , and normalized to obtain signals , and ; , and inputting the DSP module to calculate to obtain , and ; When , and are all greater than 0.9, it is judged that the current reflection signal is strong, and the reflection is not sensitive to the light frequency, and the road surface state type is determined as dry state. When the road surface state type is determined to be snow state according to the absorption intensity characteristics of snow to different wavelengths of laser, the snow film thickness is calculated by the snow thickness calculation formula: wherein and are obtained from the calibration experiment; When the road surface state type is determined as ice state, the ice film thickness is calculated by the ice thickness calculation formula: wherein , is obtained from the calibration experiment; When the road surface state type is determined as water state, the water film thickness is calculated by the water film thickness calculation formula: The water film thickness is calculated, wherein , is obtained from the calibration experiment.

2. The laser remote sensing road surface condition measuring system according to claim 1, characterized in that, The weak signal detection module comprises a preamplifier, a phase-sensitive detector connected to the preamplifier, a low-pass filter connected to the phase-sensitive detector, and a pulse generator; The digital signal processing module comprises a DSP module and an AD conversion module.

3. A measurement method of a laser remote sensing type road surface state measurement system, characterized by, The measurement method applies the laser remote sensing type road state measurement system according to any one of claims 1 to 2, and the measurement method comprises the following steps: The plurality of laser modules emit the emitted light after pulse generator light source modulation, collimate the emitted light through the lens, and irradiate the target object; The detector module detects the light reflection signal reflected by the target object, photoelectrically converts the light reflection signal into electrical signal, and outputs the electrical signal; The electrical signal after photoelectric conversion is inputted into the weak signal detection module for signal processing; According to the signal after signal processing, the digital signal processing module is inputted for analog-digital conversion processing and algorithm inversion, wherein the algorithm inversion comprises road state type judgment and specific steps of calculating thickness data of the target object according to the road state type, which comprises: The weak signal detection module comprises a preamplifier, a phase-sensitive detector connected to the preamplifier, a low-pass filter connected to the phase-sensitive detector, and a pulse generator; The digital signal processing module comprises a DSP module and an AD conversion module. The measurement method applies the laser remote sensing type road state measurement system according to any one of claims 1 to 2, and the measurement method comprises the following steps: The plurality of laser modules emit the emitted light after pulse generator light source modulation, collimate the emitted light through the lens, and irradiate the target object; The detector module detects the light reflection signal reflected by the target object, photoelectrically converts the light reflection signal into electrical signal, and outputs the electrical signal; The electrical signal after photoelectric conversion is inputted into the weak signal detection module for signal processing; According to the signal after signal processing, the digital signal processing module is inputted for analog-digital conversion processing and algorithm inversion, wherein the algorithm inversion comprises road state type judgment and specific steps of calculating thickness data of the target object according to the road state type, which comprises: The weak signal detection module comprises a preamplifier, a phase-sensitive detector connected to the preamplifier, a low-pass filter connected to the phase-sensitive detector, and a pulse generator; The digital signal processing module comprises a DSP module and an AD conversion module. The measurement method applies the laser remote sensing type road state measurement system according to any one of claims 1 to 2, and the measurement method comprises the following steps: The plurality of laser modules emit the emitted light after pulse generator light source modulation, collimate the emitted light through the lens, and irradiate the target object; The detector module detects the light reflection signal reflected by the target object, photoelectrically converts the light reflection signal into electrical signal, and outputs the electrical signal; The electrical signal after photoelectric conversion is inputted into the weak signal detection module for signal processing; According to the signal after signal processing, the digital signal processing module is inputted for analog-digital conversion processing and algorithm inversion, wherein the algorithm inversion comprises road state type judgment and specific steps of calculating thickness data of the target object according to the road state type, which comprises: The weak signal detection module comprises a preamplifier, a phase-sensitive detector connected to the preamplifier, a low-pass filter connected to the phase-sensitive detector, and a pulse generator; The digital signal processing module comprises a DSP module and an AD conversion module.

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