Dual-wavelength non-contact pavement condition detection device

Abstract

The utility model discloses a dual-wavelength non-contact road surface condition detection device, and particularly relates to the technical field of road surface detection, the dual-wavelength non-contact road surface condition detection device comprises an optical measurement system and an electronic control system, the optical measurement system is composed of a transmitting end capable of transmitting infrared light to irradiate a road surface and a receiving end capable of receiving reflected light; the electronic control system comprises an emission driving circuit for driving the laser, a receiving and processing circuit for converting voltage, an MCU control circuit for analyzing data, and a peripheral interface circuit interacting with the outside. According to the utility model, the reflectivity of near-infrared light with different wavelengths is different, so that accumulated snow and accumulated water on a road surface are measured, the influence of sunlight irradiation on a detection result can be reduced when the device is used, and meanwhile, the influence of external temperature on the detection result can be reduced, so that the influence of the outside on the device is reduced, and the detection accuracy is improved. The device is more stable in use, and the accuracy of a detection result is also improved.

Description

Technical Field

[0001] The utility model relates to the technical field of road surface detection, in particular to a dual-wavelength non-contact road surface condition detection device. Background Art

[0002] As the mileage of vehicles on roads increases, the issue of road driving safety becomes increasingly prominent. Relevant studies have shown that there is a certain correlation between the road friction coefficient and the accident rate, and the change in the road friction coefficient is mainly affected by the road conditions, that is, water accumulation, ice accumulation, and snow accumulation on the road.

[0003] Common road condition detection methods are divided into contact and non-contact. The traditional contact road condition method uses traditional mechanical methods to obtain road surface parameters. The accuracy and life of contact sensors are affected by road driving, road materials, weather conditions, etc., and such sensors have high maintenance costs and installation requirements, and cannot provide real-time measurements.

[0004] Recently, some non-contact measurement methods are often affected by sunlight. The fundamental reason is that the near-infrared light band contained in sunlight will interfere with the measurement. In addition, infrared lasers are semiconductor devices and will inevitably be affected by external temperature changes. To address this problem.

[0005] The utility model can reduce the influence of sunlight on the detection results when the device is used, and at the same time, can also reduce the influence of external temperature on the detection results, so that the device is less affected by the outside world when detecting the road, and improves the accuracy of the device in detecting the road condition. Utility Model Content

[0006] The main purpose of the utility model is to provide a dual-wavelength non-contact road condition detection device, which can effectively solve the problem that the device is easily affected by the outside world during use, resulting in inaccurate detection.

[0007] In order to achieve the above purpose, the technical solution adopted by the utility model is:

[0008] A dual-wavelength non-contact road condition detection device, comprising an optical measurement system and an electronic control system;

[0009] The optical measurement system consists of a transmitter that can emit infrared light to illuminate the road surface and a receiver that receives the reflected light.

[0010] The electronic control system includes: an emission drive circuit for driving the laser, a receiving and processing circuit for converting voltage, an MCU control circuit for analyzing data, and a peripheral interface circuit for interacting with the outside world.

[0011] Preferably, the transmitting end includes a laser transmitter, an optical switch, and a fiber collimating lens;

[0012] The receiving end includes an InGaAs photodetector, a filter, and a plano-convex lens.

[0013] Preferably, the receiving processing circuit further includes a photodiode and a high-pass filter connected by a wire;

[0014] The emission driving circuit includes a driving transistor N4 and a laser diode.

[0015] Preferably, the laser emitter can emit near-infrared light with a wavelength of 1310nm or 1550nm.

[0016] Preferably, the output current of the photodiode is converted into an AC voltage signal with a certain DC bias after the first stage amplification, and the DC bias of the signal will increase with the increase of sunlight exposure. The first stage amplification of the circuit is AC coupled with the second stage amplification through a high-pass filter, and has a DC bias voltage Vref in the second stage.

[0017] Preferably, the first-stage amplifier constitutes a subtractor for comparing outputs, the second-stage amplifier is used to drive transistor N4, the laser diode LD end (pins 1 and 2) is connected between the collector of N4 and the power supply, and the PD end (pins 3 and 4) is grounded and connected to the negative input end of the first-stage subtractor after resistor voltage division.

[0018] Compared with the prior art, the utility model has the following beneficial effects:

[0019] The utility model adopts the design of receiving and processing circuit and transmitting driving circuit, and utilizes the different reflectivity of near-infrared light of different wavelengths to measure snow and water on the road surface, so that the device can reduce the influence of sunlight on the detection results when in use. At the same time, it can also reduce the influence of external temperature on the detection results, so that the device is less affected by the outside world, making the device more stable when in use and improving the accuracy of the detection results. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is the characteristic spectrum of near infrared light in the 1100-1700nm band;

[0021] Figure 2 This is the schematic diagram of the optical measurement system;

[0022] Figure 3 It is the circuit principle diagram of the utility model;

[0023] Figure 4 The receiving and processing circuit of the utility model;

[0024] Figure 5 This is the emission drive circuit of the utility model. DETAILED DESCRIPTION

[0025] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below in conjunction with specific implementation methods.

[0026] Embodiment 1

[0027] like Figure 1 - Figure 5 As shown, a dual-wavelength non-contact road condition detection device includes two major parts: an optical measurement system and an electronic control system. The optical measurement system consists of a transmitting end and a receiving end. The transmitting end consists of a laser transmitter, an optical switch, and a fiber optic collimating lens. The transmitting end is responsible for emitting two wavelengths of near-infrared light to illuminate the road surface; the receiving end consists of an indium gallium arsenide photodetector, a filter, and a plano-convex lens. The receiving end is responsible for converging the reflected light on the detector window and converting it into corresponding photocurrent.

[0028] Among them, the electronic drive system mainly includes the transmitting drive circuit, the receiving processing circuit, the MCU control circuit, and the peripheral interface circuit.

[0029] Specifically, 1. Transmitter drive circuit: responsible for driving the laser output. In order to transmit to a longer distance and facilitate filtering when receiving, the laser output is driven by a square wave of a certain frequency;

[0030] 2. Receiving and processing circuit: responsible for converting the current converted by the InGaAs photodetector into a voltage value that can be processed by the MCU (specifically, the photoelectric amplifier circuit converts the photocurrent value into a voltage value, and then the AC amplifier circuit filters out the DC voltage, and amplifies the AC voltage by a certain multiple, and then sends it to the AC chopper with the same frequency as the transmission after filtering, filters out other frequencies except the transmission frequency, and converts the AC voltage into DC voltage, and finally sends it to the MCU for analysis and processing);

[0031] 3. MCU control circuit: responsible for the control, data analysis and output of the entire electronic control system;

[0032] 4. Peripheral interface circuit: responsible for interaction with the outside world.

[0033] In addition, infrared spectroscopy is often used to detect different substances. Figure 1 The figure shows the reflectivity of different road surface conditions under the near-infrared band. Since the reflectivity of water, ice and snow to infrared light of different bands varies greatly, the characteristic wavelengths of several infrared bands can be selected as the basis for distinguishing the road surface conditions. For cost considerations, the utility model uses the two most commonly used near-infrared bands of 1310nm and 1550nm in engineering.

[0034] like Figure 2As shown, the transmitting end emits two bands of near-infrared light at a certain angle to illuminate the road surface, and the receiving end receives the two returned optical signals, and processes them through circuits to obtain corresponding measurement values. Dry signals of the two optical signals are obtained on the dry road surface in advance, and the measured signals are processed according to the dry signals during actual measurement. Finally, the corresponding covering type is obtained according to the characteristics of different road coverings, and the corresponding covering thickness is obtained according to the thickness calculation formula.

[0035] Embodiment 2

[0036] This embodiment further improves the receiving processing circuit and the transmitting driving circuit on the basis of the first embodiment, so that the device can reduce the influence of sunlight on the detection result when in use, and at the same time, can also reduce the influence of external temperature on the detection result.

[0037] To reduce the impact of sunlight on the measured values ​​when the device is in use, such as Figure 4 The figure shows the receiving processing circuit diagram. The output current of the photodiode is converted into an AC voltage signal with a certain DC bias after the first stage amplification, and the DC bias of the signal will increase with the increase of sunlight. The first stage amplification of the circuit realizes AC coupling with the second stage amplification through a high-pass filter, and the second stage has a DC bias voltage Vref. After the AC signal with the bias voltage in the previous stage passes through the high-pass filter, the original DC bias voltage is isolated by the capacitor and is re-inserted into a DC bias voltage with an amplitude of Vref.

[0038] To reduce the impact of external temperature on semiconductor devices during device use, such as Figure 5 The diagram shows the emission drive circuit. The first-stage amplifier forms a subtractor for comparing outputs. The second-stage amplifier is used to drive transistor N4. The laser diode LD end (pins 1 and 2) is connected between the collector of N4 and the power supply. The PD end (pins 3 and 4) is grounded and connected to the negative input end of the first-stage subtractor after voltage division by resistors. When F is at a high level, N1 is cut off. The power supply voltage is divided by resistors and then drives transistor N4 to conduct after passing through the first-stage subtractor and the second-stage amplifier. Resistor R45 is used to limit the current so that the laser tube works under appropriate conditions. The conduction current reaches the threshold current of the laser diode, and the laser diode emits light. When the temperature rises, the threshold current of the laser diode decreases, resulting in an increase in the current at the PD end. The voltage at the negative input end of the first-stage subtractor increases, thereby causing the output end voltage to decrease. After the second-stage amplifier, the emitter potential of N4 decreases, thereby reducing the current in the loop where the LD end is located and the current at the PD end. When the temperature decreases, the process is the opposite. The current in the loop where the LD end is located can also be adjusted, and ultimately the current at the PD end remains unchanged and the optical power of the laser diode remains unchanged.

[0039] Embodiment 3

[0040] Combining Embodiment 1 and Embodiment 2, a calculation software is required to calculate the thickness of the road surface covering when the device is in use.

[0041] The processing logic of the software part of the device is as follows: The system transmitter can emit near-infrared light of two wavelengths, 1310 nm and 1550 nm. These two lights are reflected after irradiating the road surface and finally received by the receiver. Let the values when the road surface is dry be Dry1310 and Dry1550, and store these values in the MCU. Let the real-time measured values of the two wavelengths of infrared light be C1310 and C1550. Process the two measured values uniformly to obtain B1310 = C1310 / Dry1310 and B1550 = C1550 / Dry1550.

[0042] 1. When the road surface is in a dry state, since the dry road surface reflects the light of the two wavelengths strongly, when 0.8 < B1310 < 1.2 and 0.8 < B1550 < 1.2, it can be judged that the road surface condition is dry;

[0043] 2. When the road surface is covered with snow, since snow reflects the light of the 1310 nm band extremely strongly and reflects less light of the 1550 nm band, when 1.2 < B1310 and B1550 < 0.3, it can be considered that the road surface is covered with snow;

[0044] 3. When the road surface is in a state of icing or waterlogging, the reflection of the light of the two bands will decrease. Therefore, when B1310 < 0.8 and B1550 < 0.8, the road surface is waterlogged or iced.

[0045] In addition, since there is no obvious difference in the light absorption rates of water and ice for the 1310 nm and 1550 nm bands, it is difficult to distinguish only by measuring the magnitude of the reflected light value. It is necessary to combine the temperature change situation to judge the current state of waterlogging or icing on the road surface. After determining the type of road surface covering, the corresponding thickness can be calculated.

[0046] According to the Lambert-Beer law: A = ln(1 / T) = KLc, where A is the absorbance, T is the transmittance (transparency), which is the ratio of the intensity of the outgoing light (I) to the intensity of the incident light (I0). K is the absorption coefficient, which is related to the properties of the absorbing substance and the wavelength λ of the incident light, c is the concentration of the absorbing substance, and L is the thickness of the absorption layer. The absorbing substance is various forms of water. Therefore, it can be considered that the concentration c = 1. Therefore, L = (1 / K) * ln(1 / T). Since the reflection of the 1550 nm band of light is small and insensitive to thickness changes when the covering is snow, the value of 1310 nm is generally selected as the thickness judgment basis, and the value of 1550 nm is only used for state judgment;

[0047] The calculation formula for the thickness of the road covering is L=K1*ln(1 / B1310)+b. The specific value of each covering needs to be determined through actual measurement, and L is the thickness of the covering.

[0048] The above shows and describes the basic principle and main features of the utility model and the advantages of the utility model. Those skilled in the art should understand that the utility model is not limited by the above embodiments. The above embodiments and descriptions are only for explaining the principle of the utility model. Without departing from the spirit and scope of the utility model, the utility model may have various changes and improvements, which fall within the scope of the utility model to be protected. The scope of protection claimed by the utility model is defined by the attached claims and their equivalents.

Claims

1. A dual-wavelength non-contact road condition detection device, characterized in that: Including optical measurement system and electronic control system; The optical measurement system consists of a transmitter that can emit infrared light to illuminate the road surface and a receiver that receives the reflected light. The electronic control system includes: an emission drive circuit for driving the laser, a receiving and processing circuit for converting voltage, an MCU control circuit for analyzing data, and a peripheral interface circuit for interacting with the outside world.

2. A dual-wavelength non-contact road condition detection device according to claim 1, characterized in that: The transmitting end includes a laser transmitter, an optical switch, and a fiber collimating lens; The receiving end includes an InGaAs photodetector, a filter, and a plano-convex lens.

3. A dual-wavelength non-contact road condition detection device according to claim 1, characterized in that: The receiving processing circuit also includes a photodiode and a high-pass filter connected by wires; The emission driving circuit includes a driving transistor N4 and a laser diode.

4. A dual-wavelength non-contact road condition detection device according to claim 2, characterized in that: The laser transmitter can emit near-infrared light with wavelengths of 1310nm and 1550nm.

5. A dual-wavelength non-contact road condition detection device according to claim 3, characterized in that: The output current of the photodiode is converted into an AC voltage signal with a certain DC bias after the first stage amplification, and the DC bias of the signal will increase with the increase of sunlight exposure. The first stage amplification of the circuit is AC coupled with the second stage amplification through a high-pass filter, and there is a DC bias voltage Vref in the second stage.

6. A dual-wavelength non-contact road condition detection device according to claim 5, characterized in that: The first stage amplifier constitutes a subtractor for comparing outputs, the second stage amplifier is used to drive transistor N4, the laser diode LD terminal is connected between the collector of N4 and the power supply, and the PD terminal is grounded and connected to the negative input terminal of the first stage subtractor after resistor voltage division.

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