JP2000047727A - Vehicle position detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a vehicle position detecting device to detect the position of its own vehicle about a lane section marker at a high S/N ratio by detecting the position of the vehicle with respect to the lane section marker from the detection result of a marker detection means. SOLUTION: A transmitting means sends a radio wave toward the road surface around the vehicle and a receiving means receives its reflected wave separately as a vertical and a horizontal polarized wave. A marker reflected wave extracting means extracts the reflected wave from the lane section marker laid on the road surface according to the result of a comparison between the vertical and horizontal polarized components of the reflected wave and a marker detecting means detects the lane section marker according to the extracted reflected wave from the lane section marker. Then the position of the vehicle about the lane section marker is detected from the detection result. Of this device, a signal processing circuit 31 detects the position of the lane section marker according to beat signal data from a subtracting process circuit 30 and also detects the position of a body other than the lane section marker according to beat signal data from an FFT processing circuit 28.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle position detecting device for detecting the position of a vehicle with respect to a lane marker laid on a road surface, a lane marker easily detected by the vehicle position detecting device, and these vehicles. The present invention relates to a vehicle position detection system including a position detection device and a lane marking.

[0002]

2. Description of the Related Art As a technique for detecting a position of a vehicle on a road, there is a technique described in "Vehicle steering control apparatus" in Japanese Utility Model Laid-Open Publication No. 1-109910. In this conventional technique, a light reflecting tape is laid on a road surface, and the light is projected toward a lower side of a vehicle, thereby detecting a relative position of the own vehicle with respect to the light reflecting tape based on the reflected light intensity.

[0003]

However, according to this prior art, since the position of the light reflecting tape is detected using light, the light projected from the own vehicle due to disturbance light during rainfall or snowfall. There is a possibility that reflected light cannot be detected. Also,
Because of the so-called direct type detection in which light is projected downward from the vehicle, it is difficult to obtain position prediction information, that is, preview information, associated with traveling.

[0004]

SUMMARY OF THE INVENTION The vehicle position detecting device of the present invention has been made to solve such a problem, and includes a transmitting means for transmitting a radio wave toward a road surface around a vehicle, and a transmitting device for transmitting a radio wave from the road surface. A receiving means for separating the reflected wave into a vertically polarized wave and a horizontally polarized wave, and comparing the vertically polarized wave component and the horizontally polarized wave component of the reflected wave with the lane markings laid on the road surface based on the comparison result Marker reflected wave extracting means for extracting a reflected wave from the vehicle, and sign detecting means for detecting a lane marking based on the extracted reflected wave from the lane marking, and detecting the lane marking based on the detection result of the sign detecting means. The position of the vehicle with respect to the sign is detected.

[0005] Of the radio waves transmitted from the transmitting means, most of the horizontally polarized waves are reflected on the surface of the lane marking substantially parallel to the road surface, and travel further forward. The vertically polarized waves are partially refracted on the surface of the lane marking and enter the lane marking, and are scattered at the boundary between the lane marking and the road surface. Part of the scattered wave goes back on the incident path and reaches the receiving means as a reflected wave.

[0006] On the other hand, the transmitted wave is also reflected on various objects existing on the road surface, and the reflected wave also reaches the receiving means. However, since the reflection in this case is reflected on a surface substantially perpendicular to the road surface, the reflected wave usually includes both the horizontal polarization and the vertical polarization.

Therefore, by comparing the intensity of the vertical polarization and the intensity of the horizontal polarization in the sign reflected wave extracting means, it is possible to discriminate between the reflected wave from the lane marking and the reflected wave from other objects.

The sign detecting means detects the position of the lane marking based on the reflected wave extracted by the sign reflected wave extracting means, and thereby detects the position of the vehicle relative to the lane marking.

As a lane marking, for example, there is a white line, but it is desirable that the surface is a dielectric layer and its relative permittivity is 10 or more.

It is desirable that a conductor for radio wave reflection is provided below the surface of the dielectric layer of the lane marking.

[0011]

FIG. 1 is a block diagram showing a configuration of a vehicle position detecting device according to an embodiment of the present invention. This device utilizes a transmission / reception function of a radar device, and is obtained by adding some means necessary for vehicle position detection to the radar device. As a radar device, F
An M-CW radar device is used. The vehicle position detecting device is provided at a front end of the vehicle, and uses a predetermined range of a road surface in front of the vehicle as a detection range.

The transmitting unit 11 is a voltage controlled oscillator (VCO)
The modulator 13 adjusts a control voltage applied to the VCO 12 to generate a triangular wave modulation signal. For example, the center frequency f0 is 76.5 GHz, the frequency modulation width ΔF is 100 MHz, and the FM modulation frequency fm is 700H.
Generate a triangular wave modulation signal as z. This signal is radiated from the transmitting antenna 14 toward the front of the vehicle, for example, toward a front road surface in a range of several meters to several tens of meters.

The receiving section 21 includes a receiving antenna 22 for receiving a vertically polarized wave component, a receiving antenna 23 for receiving a horizontally polarized wave component, mixers 24 and 25, and an amplifier 2
6, 27.

The signal of the vertical polarization component received by the receiving antenna 22 is mixed with a part of the transmission signal from the directional coupler 15 provided in the transmission unit 11 in the mixer 24, and a beat signal is extracted. This beat signal is amplified by the amplifier 26 and sent to the FFT processing circuit 28.

Similarly, the signal of the horizontal polarization component received by the receiving antenna 23 is mixed in the mixer 25 with a part of the transmission signal from the directional coupler 16 provided in the transmission section 11 to extract a beat signal. Is done. This beat signal is amplified by the amplifier 27 and sent to the FFT processing circuit 29.

The FFT processing circuits 28 and 29 include the amplifier 2
A / D-converts the beat signal from 6, 27 and FFT
By performing (Fast Fourier Transform) processing, the frequency analysis of beat signals in vertical polarization and horizontal polarization, respectively, is performed.

The subtraction processing circuit 30 includes an FFT processing circuit 28
The FFT processing circuit 29 subtracts the horizontally-polarized beat signal frequency-converted from the vertically-polarized beat signal frequency-converted in step (1).

The signal processing circuit 31 performs position detection processing of the lane marking based on the beat signal data from the subtraction processing circuit 30, and performs an object other than the lane marking based on the beat signal data from the FFT processing circuit 28. Is performed.

Since the detection processing of the object (including the lane marking) in the present apparatus is based on the detection principle of the FM-CW radar, the principle of the FM-CW radar will be briefly described here.

As described above, the center frequency of the transmission signal is represented by f
0, the frequency modulation width is ΔF, the FM modulation frequency is fm,
Further, the beat frequency when the relative velocity of the target is zero (the beat frequency in a narrow sense) is fr, the Doppler frequency based on the relative velocity is fd, the beat frequency in the section where the frequency increases (up section) is fb1, and the frequency decreases. Assuming that the beat frequency in the section (down section) is fb2, fb1 = fr-fd (1) fb2 = fr + fd (2) holds.

Therefore, if the beat frequencies fb1 and fb2 in the up and down sections of the modulation cycle are measured separately, fr and fd can be obtained from the following equations (3) and (4).

Fr = (fb1 + fb2) / 2 (3) fd = (fb2-fb1) / 2 (4) If fr and fd are obtained, the distance R and the velocity V of the target are calculated by the following (5) (6) ) Formula.

R = (C / (4 · ΔF · fm)) · fr (5) V = (C / (2 · f0)) · fd (6) where C is the speed of light.

The operations of the equations (1) to (6) are separately performed in the signal processing circuit 31 based on the beat signal from the FFT processing circuit 28 or the subtraction processing circuit 30, respectively.

In the signal processing circuit 31, the subtraction processing circuit 30
By the target detection processing based on the beat signal from
The position of the lane markings laid on the road surface is detected.
Further, the position detection of various objects on the road is performed by the target detection processing based on the beat signal from the FFT processing circuit 28.

The use of the beat signal generated by the subtraction processing circuit 30 enables the position of the lane marker to be detected separately from other objects because the polarization component of the reflected wave from the lane marker and the other components on the road are detected. Based on the difference from the polarization component of the reflected wave from the object.

While the reflected wave from a general object on the road includes both vertically polarized and horizontally polarized waves, the reflected wave from the lane markings laid on the road surface is almost horizontally polarized. Not included.

When the transmitted wave hits the surface of a lane marking, for example, a white line, the horizontal polarization component is almost reflected. Since the surface of the white line is parallel to the road surface, the reflected wave goes to the opposite side of the present device and does not return to the present device. on the other hand,
Part of the vertically polarized wave component is refracted on the surface of the white line and is transmitted inside. This is because the white line is made of a dielectric material, and the transmitted refracted wave is scattered at the boundary between the road surface and the white line. Part of the scattered light follows the incident path in the opposite direction, refracts on the surface of the white line, and reaches the receiving unit of the present apparatus.

FIG. 2 is a graph showing the transmittance at the lane marking for vertical polarization and horizontal polarization, respectively. This graph shows the transmittance at an arbitrary distance when the relative permittivity of the lane marking is set to 100 and the arrangement height of the device is set to 60 cm. There is a relationship of L (m) = 0.6 tan (90 ° −θ) between the distance L and the incident angle θ.
That is, the incident angle increases as the distance increases. The greater the angle of incidence, the higher the reflectance and therefore the lower the transmittance. FIG. 2 illustrates this well.

In the figure, a characteristic 35 indicates the transmittance of vertically polarized waves, and a characteristic 36 indicates the transmittance of horizontally polarized waves.
As can be seen from this graph, the transmittance of vertically polarized waves is sufficiently larger than the transmittance of horizontally polarized waves.

Therefore, when a linearly polarized wave 40 inclined at 45 degrees to the horizontal as shown in FIG. 3, that is, a polarized wave having the same horizontal polarization intensity Ex and the same vertical polarization intensity Ey as the transmission wave, a white line As shown in FIG. 4, the reflected wave becomes a linearly polarized wave 41 whose vertical polarization intensity Ery is sufficiently larger than the horizontal polarization intensity Erx.

Since a reflected wave from a general object on the road other than the lane marking is a reflection on a substantially vertical surface of the object, the vertically polarized wave and the horizontally polarized wave are reflected at substantially the same reflectance. Therefore, the reflected wave from such a general object includes both vertically polarized waves and horizontally polarized waves.

In the present device, the lane marking is selectively detected by utilizing such a difference in the polarization component ratio of the received wave. This selection processing is executed by the subtraction processing circuit 30.

FIGS. 5A to 5C show the subtraction processing circuit 30.
5 is a graph for explaining the processing in FIG. FIG. 3A shows an example of a frequency-converted beat signal for a vertical polarization obtained in a certain time zone, and FIG. 6B shows a frequency-converted beat signal for a horizontal polarization received in the same time zone. (C) shows the result of subtracting the horizontally polarized beat signal shown in (b) from the vertically polarized beat signal shown in (a). In each figure, the horizontal axis indicates frequency, and the vertical axis indicates reception intensity.

In FIG. 5A, two peaks 43,
Although 44 appears, it is assumed here that the peak 43 is based on the reflected wave from the white line which is the lane marking, and the peak 44 is based on the reflected wave from the preceding vehicle. As described above, the vertical polarization component of the received wave includes lane markings and reflections from other objects (mainly, preceding vehicles).

However, the reflected wave from the lane marking does not include a horizontal polarization component for the reason described above. Therefore, as shown in FIG. 5B, the horizontal polarized wave when the vertical polarized wave as shown in FIG. 5A is received hardly includes the reflected wave from the lane marking. That is, only the beat signal 45 based on the reflected wave from the preceding vehicle appears.

Therefore, the waveform shown in FIG.
Is reduced, a reflected wave 46 consisting of only vertically polarized waves can be extracted as shown in FIG. This reflected wave 46
Is nothing but reflected waves from lane markings.

The signal processing circuit 31 detects the position and the relative speed of the lane marking based on the beat frequency shown in FIG. The detection of the position of the lane marking is nothing less than the detection of the position of the own vehicle with respect to the lane marking.

Next, a description will be given of desirable lane division markers.

As described above, the transmitted wave is refracted at the lane marking surface and scattered and reflected at the boundary with the road surface. A part of the scattered light is received by traveling back through the incident path. Therefore,
As shown in FIG. 6, the lane markings have a two-layer structure including a dielectric layer 61 and a conductor layer 62, and the conductor layer 62 is disposed at the boundary between the dielectric layer 61 and the road 63. With this configuration, the transmission wave refracted and transmitted on the surface of the dielectric layer 61 is reflected by the conductor layer 62 having a high reflectance. Therefore,
The reflected wave intensity is increased as compared with the case where the lane marking is constituted only by the dielectric layer. The surface of the conductor layer 62 on the side of the dielectric layer 61 is desirably roughened so as to scatter radio waves.

It is preferable that the relative dielectric constant of the dielectric layer of the lane marking is large because the reflection intensity increases. FIG. 7 is a diagram showing a state of refraction of a radio wave on the dielectric layer surface 71. Now, consider the case where the incident angle θ is 80 degrees. The incident angle θ of 80 degrees is an incident angle at a position of 3.4 m in front when the apparatus is installed at a height of 60 cm from the road surface. The incident angle θ increases if the distance is further forward, and the incident angle θ decreases if the distance is closer. When the position information of the lane marking is used as preview information, position information farther than 3.4 m is considered effective.

When the incident angle θ was 80 degrees, the refraction angle α at which the difference from the asphalt road surface caused a difference of 10 dB was 18 degrees from the test results. If the refraction angle α is smaller than 18 degrees, the reflection intensity is further increased, which is desirable.

The sine value of the refraction angle relative to the sine value of the incident angle, that is, the refractive index n, matches the square root of the relative permittivity εr, and is expressed as follows.

[0044]

(Equation 1) By substituting θ = 80 degrees and α = 18 degrees into the above equation (7),
The relative permittivity εr is approximately 10.15. Therefore,
It is desirable that the relative permittivity εr of the dielectric of the lane marking is 10 or more.

FIG. 8 is a sectional view showing another preferred embodiment of the lane marking. In the lane marking shown in FIG.
Although the conductor layer 62 is used to increase the reflectance, a conductor powder 81 is used instead of the conductor layer 62 in this embodiment. That is, the dielectric layer 82 mixed with the conductor powder 81 is used as the lane marking. With this configuration, the incident wave 83 refracted on the surface of the dielectric layer 82 is scattered by the conductor powder 81, and a part of the incident wave 83 returns to the incident path. With this configuration, it is possible to easily lay a lane marking having excellent reflection characteristics.

Desirable lane markings as described above are:
Instead of making itself a white line, as shown in FIG.
It may be scattered on the normal white line 91 at an appropriate interval. In the figure, reference numeral 92 indicates a laid portion of a desired lane marking.

In the vehicle position detecting device shown in FIG. 1, a linearly polarized wave inclined at 45 degrees is used as a transmission wave. However, if it includes a horizontally polarized wave and a vertically polarized wave, for example, a circularly polarized wave is used. May be something.

Further, this vehicle position detecting device is an FM-CW
Although the position of the lane marking is detected by utilizing the principle of radar, another radar method may be used as the detection method.

As a material for the conductor layer or the conductor powder used for the desired lane marking, aluminum is desirable.

[0050]

As described above, according to the vehicle position detecting device of the present invention, lane markings such as white lines which are relatively far away can be detected separately from other objects. That is, the position of the host vehicle with respect to the relatively far lane marking can be clearly detected. In addition, since radio waves having a wavelength shorter than that of light are used, there is no problem in the conventional device that reflected light of light projected from the own vehicle due to disturbance light during flooding cannot be detected.

Further, according to the lane markings of the present invention, the intensity of radio waves radiated from the vehicle position detecting device of the present invention, reflected by the lane markings and returned can be increased.

Therefore, according to the vehicle position detecting system in which the vehicle equipped with the vehicle position detecting device of the present invention travels on the road on which the lane marking of the present invention is laid, a high S / N is achieved.
Can detect the position of the own vehicle with respect to the lane marking.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a vehicle position detecting device according to an embodiment of the present invention.

FIG. 2 is a graph showing transmittances of vertical polarization and horizontal polarization in lane markings.

FIG. 3 is a diagram illustrating a polarization component of a transmission wave.

FIG. 4 is a diagram illustrating a polarization component of a received wave.

5 is a graph showing a state before and after a beat signal processed by a subtraction processing circuit 30. FIG.

FIG. 6 is a sectional view showing a lane marking according to an embodiment of the present invention.

FIG. 7 is a diagram showing refraction of radio waves on the surface of a lane marking, which is one embodiment of the present invention.

FIG. 8 is a sectional view showing a lane marking according to an embodiment of the present invention.

FIG. 9 is a plan view showing a lane marking according to an embodiment of the present invention.

[Explanation of symbols]

11 deep layer, 12 VCO, 13 modulator, 14 transmitting antenna, 15, 16 directional coupler, 21 receiving unit, 22 receiving antenna for vertical polarization, 23 receiving antenna for horizontal polarization , 24, 25 ... mixer, 28, 29 ... FF
T processing circuit, 30: subtraction processing circuit, 31: signal processing circuit, 61: dielectric layer, 62: conductor layer, 81: conductor powder.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yoshihide Kamisato 1-2-28 Goshodori, Hyogo-ku, Kobe-shi, Hyogo F-term in Fujitsu Ten Limited (Reference) 5H301 AA01 AA10 BB20 CC02 CC06 EE12 FF21 FF26 GG07 MM07 5J070 AB19 AC01 AD02 AD03 AD17 AE07 AF03 AH25 AH31 AH35 AK22 BA01

Claims (8)

[Claims] A transmitting means for transmitting a radio wave toward a road surface around a vehicle, a receiving means for separating a reflected wave of the radio wave from the road surface into a vertically polarized wave and a horizontally polarized wave, and receiving the reflected wave; Sign reflected wave extracting means for comparing the vertically polarized wave component and the horizontally polarized wave component and extracting a reflected wave from a lane marking laid on the road surface based on the comparison result; and the extracted lane marking A sign detecting means for detecting the lane marking based on a reflected wave from the sign, and detecting a position of the vehicle with respect to the lane marking from a detection result of the sign detecting means. apparatus. 2. The vehicle position detecting device according to claim 1, wherein the transmission signal is a radio wave including a vertical polarization component and a horizontal polarization component. 3. The transmission signal, wherein a vertical polarization component and a horizontal polarization component have substantially equal intensities, and the beacon reflected wave extraction means determines a difference between a vertical polarization component and a horizontal polarization component of the reflected wave. The vehicle position detecting device according to claim 2, wherein a reflected wave from the lane marking is extracted based on the difference. 4. A lane marking which is laid on a road surface for lane identification, wherein a dielectric layer having a relative permittivity of 10 or more is formed on the surface. 5. The lane marking according to claim 4, further comprising a conductor that reflects a radio wave incident on the dielectric layer. 6. The lane marking according to claim 5, wherein the conductor is a conductor layer provided below the dielectric layer. 7. The lane marking according to claim 5, wherein the conductor is a conductor particle or a conductor powder provided in the dielectric layer. 8. The vehicle position detecting device according to claim 1, which is laid on a road surface on which a vehicle on which the vehicle position detecting device is mounted travels. Vehicle position detection system provided with a traffic lane marking.