JP4429932B2 - Surface condition discriminator - Google Patents

Description

  The present invention relates to a surface state determination device.

 Discriminating the road surface condition is extremely important for ensuring traffic safety. Especially in the winter season, drivers can pre-install studless tires by detecting road freezing and snow accumulation at an early stage to take measures such as road heating, snow removal, or spraying anti-freezing materials, and providing road information. It is possible to take measures such as changing tires or attaching chains to the vehicle, which leads to a reduction in the probability of occurrence of traffic accidents.

For example, the following Patent Documents 1 to 3 disclose a technique for determining a road surface state. The technology of Patent Document 1 below determines road surface conditions (dry, frozen, wet, snow, etc.) based on fuzzy inference using information on distance, reflection intensity, scan plane coordinates, and road surface temperature detected by a laser radar. Is. Moreover, the technique of patent document 2 discriminate | determines a road surface state based on the measurement signal from the road surface shape sensor which detects the undulation of a road surface, an air temperature sensor, a dew point sensor, and a road surface temperature sensor. Moreover, the technique of patent document 3 acquires road surface state image data by irradiating a road surface with a laser beam and receiving the reflected light of the said laser beam, and discriminate | determines a road surface state based on the said road surface state image data. It is.
JP 2002-260151 A JP 2002-197585 A JP 2002-39861 A

  However, in order to determine the road surface state in the above-described prior art, in Patent Document 1, various measurements such as a road surface temperature sensor, in Patent Document 2 an air temperature sensor, a dew point sensor and a road surface temperature sensor, and in Patent Document 3 an image capturing camera, etc. There is a problem that a device is necessary and the cost increases.

 This invention is made | formed in view of such a situation, and it aims at discriminating a road surface state at low cost, without using an extra measuring device.

 In order to solve the above-mentioned problem, in the present invention, as a first solving means related to the surface state discriminating apparatus, a transmitting means for radiating a frequency modulation signal frequency-modulated with a predetermined modulation signal to a device under test as a transmission wave; Receiving means for receiving the reflected wave reflected by the device under test as the received signal, the beat signal voltage of the beat signal obtained by mixing the frequency modulation signal and the received signal, and the device under test A means is provided that includes a discrimination operation means for discriminating the surface state of the object to be measured based on the correlation with the radio wave reflectance of the surface.

 Further, as a second solving means related to the surface state discriminating apparatus, in the first solving means, the discrimination calculating means calculates a distance to the object to be measured based on a beat frequency of the beat signal. Is adopted.

 Further, as a third solving means relating to the surface state discriminating apparatus, in the first or second solving means, the object to be measured is a road surface.

 According to the present invention, the surface state of the device under test is determined based on the correlation between the beat signal voltage of the beat signal obtained by mixing the frequency modulation signal and the received signal and the radio wave reflectance of the surface of the device under test. Since the determination is made, the surface state of the object to be measured can be determined only by detecting the beat signal voltage. Therefore, when the object to be measured is a road surface, it is possible to reduce the cost without requiring an extra sensor such as a road surface temperature sensor or an atmospheric temperature sensor for determining the road surface state as in the prior art. In addition, since road surface state determination is performed using radio waves, accurate state determination can be performed even in bad weather regardless of the weather. Furthermore, since the distance to the road surface is calculated based on the beat frequency of the beat signal, it is possible to measure the amount of snow accumulation from the change in the distance.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram illustrating a configuration of a surface state determination apparatus according to the present embodiment. In addition, this embodiment is related with the surface state discrimination apparatus which discriminate | determines a road surface state.

In FIG. 1, reference numeral 1 denotes a modulation signal generator, and 2 denotes a VCO (Voltage Controled).
Oscilator), 3 is a branching device, 4 is a transmitting antenna, 5 is a mixer, 6 is a receiving antenna, 7 is an amplifier, 8 is a BPF (Band Pass Filter), 9 is an A / D converter, and 10 is a beat signal voltage detector. , 11 is an FFT (First Fourier Transform), 12 is a discrimination calculation unit, 13 is a storage unit, 14 is an output unit, and R is a road surface.

  The modulation signal generator 1 generates a sawtooth wave signal a1 having a predetermined period Tm (frequency fm = 1 / Tm) and outputs it to the VCO 2. The VCO 2 is a voltage-controlled oscillator whose oscillation frequency is controlled using a sawtooth wave signal as a control signal, that is, a frequency modulator using a sawtooth wave signal as a modulation signal, and outputs the frequency modulation signal a2 to the branching device 3. . The branching device 3 branches and outputs the frequency modulation signal a2 to the transmission antenna 4 and the mixer 5. The transmission antenna 4 radiates the frequency modulation signal a2 to the road surface R as a transmission wave S. The receiving antenna 6 receives the reflected wave T obtained by reflecting the transmission wave S by the road surface R, and outputs it to the mixer 5 as a received signal b1.

 The mixer 5 mixes (multiplies) the frequency modulation signal a2 and the reception signal b1, generates a beat signal c1 resulting from the phase difference between the frequency modulation signal a2 and the reception signal b1, and outputs the beat signal c1 to the amplifier 7. The amplifier 7 amplifies the beat signal c1 and outputs it to the BPF 8 as a beat signal c2. The BPF 8 limits the band of the beat signal c2 and outputs it to the A / D converter 9 as the beat signal c3. The A / D converter 9 performs A / D conversion on the beat signal c3 band-limited by the BPF 8, and outputs the beat signal data d1 which is digital data to the beat signal voltage detection unit 10 and the FFT 11.

 The beat signal voltage detection unit 10 detects the beat signal voltage Vb from the beat signal data d1 and outputs it to the discrimination calculation unit 12. As will be described in detail later, this beat signal voltage Vb changes according to the radio wave reflectivity of the road surface R, and the radio wave reflectivity is specific to each state of the road surface R (dry, wet, frozen, snow cover). Have a value.

 The FFT 11 performs fast Fourier transform on the beat signal data d1 and outputs the frequency spectrum of the beat signal data d1 obtained thereby to the discrimination calculation unit 12.

 The discrimination calculation unit 12 discriminates the state of the road surface R based on the correlation between the radio wave reflectance specific to the state of the road surface R and the beat signal voltage Vb. The storage unit 13 stores in advance the correlation between the radio wave reflectance specific to each state of the road surface R (dry, wet, frozen, and snow) and the beat signal voltage Vb, and the discrimination calculation unit 12 detects the beat signal voltage. When the beat signal voltage Vb is acquired from the unit 10, based on the correlation between the beat signal voltage Vb and the radio wave reflectance specific to each state (dry, wet, frozen, snow cover) of the road surface R stored in the storage unit 13. The state of the road surface R is determined, and the determination result is output to the output unit 14.

 Further, the discrimination calculation unit 12 obtains the beat frequency fb of the beat signal c3 from the frequency spectrum of the beat signal data d1 obtained from the FFT 11, calculates the distance to the road surface R based on the beat frequency fb, and reaches the road surface R. Is output to the output unit 14 as the amount of snow.

 The output unit 14 outputs the determination result of the state of the road surface R and the amount of snow accumulation to the traffic-related organization as road information if there is snow.

 In addition, said surface state discrimination | determination apparatus mentioned above is attached to the upper part of the pole etc. which are installed in the roadside zone of a road.

 Next, the operation of the surface state discriminating apparatus configured as described above will be described.

 First, the frequency modulation signal a2 generated by the VCO 2 is radiated to the road surface R as a transmission wave S through the branching device 3 and the transmission antenna 4. The frequency modulation signal a2 is generated by frequency-modulating the sawtooth wave signal a1 output from the modulation signal generator 1 as a modulation signal, and as shown in FIG. 2A, the frequency modulation width ΔF and This is a sawtooth signal having a period Tm.

   Then, such a frequency modulation signal a2 is radiated to the road surface R as the transmission wave S, and the reflected wave T is captured by the reception antenna 6 and output to the mixer 5 as the reception signal b1. As shown in FIG. 2A, the received signal b1 is delayed by a time Δt with respect to the frequency modulation signal a2. This delay time Δt is obtained by adding the propagation time until the frequency modulation signal a2 is radiated from the transmission antenna 4 and reaches the road surface R and the propagation time until the reflected wave T reaches the reception antenna 6 from the road surface R. It's time.

   When the frequency modulation signal a2 having the delay time Δt (phase difference) and the reception signal b1 are mixed by the mixer 5 as shown in FIG. 2A, the beat signal having the amplitude characteristic as shown in FIG. c1 is generated. In FIG. 2B, the amplitude Vb is the beat signal voltage Vb. Such a beat signal c1 is input to the A / D converter 9 via the amplifier 7 and the BPF 8, is A / D converted, and is output to the beat signal voltage detector 10 as beat signal data d1. The beat signal voltage detector 10 detects the beat signal voltage Vb based on the beat signal data d1.

 Here, the following relational expression (1) is established between the beat signal voltage Vb and the received power Pr.

 Further, the received power Pr is given by the following equation (2) as a radar equation as well known, assuming that the wavelength λ, the antenna gain G, the transmission power Pt, the effective reflection area σ, the radio wave reflectance K, and the distance L to the road surface R. It is done.

 In the above equation (2), the radio wave reflectivity K varies depending on the state of the road surface R. For example, the road surface R has a unique radio wave reflectance K in each of dry, wet, frozen, and snowy states. This is because the dielectric constant changes depending on the state of the road surface R. It can also be seen from the above equations (1) and (2) that when the radio wave reflectance K changes, the beat signal voltage Vb also changes. Therefore, if the correlation between the radio wave reflectance K and the beat signal voltage Vb as described above is obtained in advance, the state of the road surface R can be determined by detecting the beat signal voltage Vb.

As an example, Table 1 shows the relationship between the radio wave reflectance K, the received power Pr, and the beat signal voltage Vb when the road surface R is wet, snowy (snow accumulation: about 15 cm), and dry. Here, in the above equation (2), wavelength λ = 12.4 · 10 ⁻³ m, antenna gain G = 19 dB, transmission power Pt = 5 mW, effective reflection area σ = 4.5 · 10 ⁵ m ² , road surface R Distance L to 10 m.

As shown in Table 1, it can be seen that the radio wave reflectance K changes depending on the state of the road surface R, and the beat signal voltage Vb also changes accordingly. Thus, each state of the road surface R (dry,
The radio wave reflectance K in wet, frozen, and snowy areas) is investigated, and the beat signal voltage Vb corresponding to the radio wave reflectance K in each state of the road surface R is calculated based on the above formulas (1) and (2). The radio wave reflectivity K in each state of R and the beat signal voltage Vb corresponding thereto are stored in the storage unit 13.

 When obtaining the beat signal voltage Vb from the beat signal voltage detection unit 10, the discrimination calculation unit 12 reads the state of the road surface R having the radio wave reflectance K corresponding to the beat signal voltage Vb from the storage unit 13, and the state of the road surface R Is determined. At this time, considering that an error occurs in the beat signal voltage Vb, if the beat signal voltage Vb is a value within a certain error, it is determined that the road surface R is in a state corresponding to the beat signal voltage Vb. To.

On the other hand, when the beat signal data d1 is input to the FFT 11, a frequency spectrum as shown in FIG. 2C is obtained by fast Fourier transform. The frequency with the highest spectrum intensity is the beat frequency fb. Here, the propagation speed of the transmission wave S (and the reflected wave T) is c, the distance between the transmission antenna 4 (and the reception antenna 6) and the road surface R is L, and the transmission wave S is reflected on the road surface R until it is received. If the delay time Δt, the frequency modulation width ΔF, and the frequency of the modulation signal are Fm (= 1 / Tm), the beat frequency fb is given based on the following equation. That is, since the beat frequency fb is proportional to the distance L to the road surface R, the distance L to the road surface R can be calculated by detecting the beat frequency fb.
Δt = 2L / c (3)
fb = (ΔF / Tm) · Δt
= (2L ・ △ F ・ Fm) / c (4)

 The amount of snow accumulation can be measured by obtaining the change in the distance L from the equation (4) to the road surface R. However, the change in the distance L as described above is not only caused by snow accumulation, but may be caused by, for example, a fallen object from a vehicle, a fallen tree, or a carcass of an animal. Therefore, first, the determination calculation unit 12 determines the state of the road surface R based on the beat signal voltage Vb, and detects the beat frequency fb from the frequency spectrum only when it is determined that the state of the road surface R is snowy. The distance L to the road surface R is calculated from the equation (4), and the change in the distance L is output to the output unit 14 as the amount of snow.

As described above, according to the surface state determination apparatus, the state of the road surface R is determined based on the correlation between the beat signal voltage Vb and the radio wave reflectance K inherent in the state of the road surface R. An extra sensor such as a road surface temperature sensor or an atmospheric temperature sensor is not required, and the cost can be reduced. In addition, since the state of the road surface R is determined using radio waves, accurate state determination can be performed even in bad weather regardless of the weather. Furthermore, the amount of snow can be measured by calculating the distance from the beat frequency fb to the road surface R.

 In the above embodiment, the case of determining the state of the road surface R has been described. However, the object to be measured is not limited to this, and the correlation between the radio wave reflectance K inherent to the surface of the object to be measured and the beat signal voltage Vb is known. Any surface condition of the object to be measured can be determined. Further, not only the surface state but also what kind of substance the object to be measured can be determined.

It is a block block diagram of the surface state determination apparatus which concerns on one Embodiment of this invention. It is explanatory drawing which shows the surface state discrimination principle of one Embodiment of this invention.

Explanation of symbols

 DESCRIPTION OF SYMBOLS 1 ... Modulation signal generation part, 2 ... VCO, 3 ... Branch device, 4 ... Transmission antenna, 5 ... Mixer, 6 ... Reception antenna, 7 ... Amplifier, 8 ... BPF, 9 ... A / D converter, 10 ... Beat signal Voltage detection unit, 11 ... FFT, 12 ... discrimination calculation unit, 13 ... storage unit, 14 ... output unit, R ... road surface

Claims (3)

Transmitting means for radiating a frequency-modulated signal frequency-modulated with a predetermined modulation signal to a device under test as a transmission wave;
Receiving means for receiving, as a received signal, a reflected wave reflected by the object to be measured by the transmitted wave;
A storage unit for storing a correlation between a beat signal voltage of a beat signal obtained by mixing the frequency modulation signal and the reception signal and a radio wave reflectance of the surface of the object to be measured;
Based on the correlation stored in the storage unit and the beat signal voltage of the beat signal obtained by mixing the received signal obtained from the receiving means with the frequency modulation signal, the obtained from the receiving means. The radio wave reflectivity of the surface of the object to be measured corresponding to the received signal is specified, and the surface state of the object to be measured is determined as dry, wet, frozen, or snow based on the radio wave reflectivity of the surface of the object to be measured A surface state discriminating apparatus comprising: a discriminating operation means for discriminating.   2. The surface state determination device according to claim 1, wherein the determination calculation means calculates a distance to the object to be measured based on a beat frequency of the beat signal.   3. The surface state discriminating apparatus according to claim 1, wherein the object to be measured is a road surface.

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