JPH10104362A - Radio wave reflector detection sensor - Google Patents

Abstract

(57) [Summary] [Problem] To prevent a malfunction at the time of detecting a radio wave reflector and reliably detect the radio wave reflector. SOLUTION: A radar sensor 16 detects a position according to a reflection intensity of a radio wave from a lane marker 11 which is a radio wave reflector laid on a road surface 12. Radio waves are radiated by the antenna 13 having the fan beam directivity 14 so that the longitudinal direction of the antenna beam irradiation area 15 matches the width of the band-shaped lane marker 11 and the reflected radio waves are received. I do. The S / C ratio, which is the reception level ratio with respect to the reflected wave from the road surface 12, can be improved, and the lane marker 11 can be reliably detected. If an antenna having a fan beam directional characteristic having an antenna beam irradiation area orthogonal to the longitudinal direction of the antenna beam irradiation area 15 is used in combination, identification can be performed more effectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensor for detecting a radio wave reflector which detects a vehicle position using a radio wave with respect to a radio wave reflector provided on a road.

[0002]

2. Description of the Related Art Conventionally, there has been known a technique for detecting a relative position of a vehicle with respect to a runway in order to automatically drive the vehicle.

FIG. 9 shows the concept of detecting the relative position of a vehicle by the Japanese Utility Model Laid-Open No. 1-109910. As shown in FIG. 9A, a light reflecting tape 1 is laid on a road surface 2 as a lane marker, and a set of two optical sensors 4,
5 to detect. The distance between the optical sensors 4 and 5 is the width included in the width of the light reflecting tape 1, and the amount of lateral shift is measured from the reception level ratio between the two optical sensors. Light emitted from the two optical sensors 4 and 5 is, as shown in FIG.
Irradiation is performed at intervals in the width direction of the light reflection tape 1 to form two irradiation areas 6 and 7. If the light reflection tape 1 and the road surface 2 are irradiated at the same ratio in the two irradiation areas, the reflection intensities should be equal. When it shifts to one side, the reflection intensity from the shifted irradiation area decreases,
The other reflection intensity increases.

As described above, in Japanese Utility Model Laid-Open No. 1-109910, a light reflecting tape is laid on a track, and a pair of optical sensors are provided on a vehicle at intervals equal to or less than the width of the reflecting tape, and a vehicle attitude is set. Techniques for detecting are disclosed. In addition, by photographing the road surface with an in-vehicle camera and extracting white lines in the screen,
A technique for detecting a relative position of a vehicle with respect to a white line is also known.

[0005]

However, when a light reflecting tape is used, sufficient light reflection may not be obtained due to contamination of the tape. Also, aside from indoors, actual roads are affected by rain, snow, etc. In the case of rainy weather, light is well reflected not only by light reflecting tapes but also by puddles, so the vehicle position cannot be detected with high accuracy. There was a problem. Similarly, when an in-vehicle camera is used, the vehicle is easily affected by the weather, and there is a problem that the contrast between the white line and other portions of the road surface is not sufficient in rainy weather or the like, and the white line cannot be accurately extracted.

[0006] Therefore, there is a concept of detecting a vehicle position by a radar sensor system using radio waves having a wavelength of a millimeter wave or more. That is, a radio wave reflector is provided as a lane marker at a predetermined position on the road surface, for example, at the center of the road surface, a radio transceiver is provided on the vehicle, and the presence or absence of the radio wave reflector is detected from the reflection intensity of the transmitted radio wave to detect the vehicle position. It is a way of thinking.

However, radio waves are also reflected from the road surface, and if an iron plate or the like is arranged on the road surface at a sea bridge or the like, an object different from the radio wave reflector may be erroneously detected.

An object of the present invention is to provide a sensor for detecting a radio wave reflector capable of reliably detecting the radio wave reflector and preventing malfunction due to other unnecessary reflectors on the road.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a sensor for detecting a band-shaped radio wave reflector which is installed on a road surface and reflects a radio wave to guide a traveling route of a vehicle. A radio wave reflector detection sensor comprising a detection antenna having a directional characteristic capable of irradiating radio waves in a fan beam shape adapted to the shape. According to the present invention, the detection antenna that receives the radio wave reflected from the band-shaped radio wave reflector has a directional characteristic capable of irradiating the radio wave in the form of a fan beam, which is adapted to the shape of the radio wave reflector. The S / C ratio, which is the reception level ratio between the radio wave reflected by the body and the radio wave reflected by the road surface, can be improved. Can be easily distinguished.

The present invention also provides a comparative antenna having a fan beam-like directional characteristic in which the longitudinal direction is orthogonal to the longitudinal direction of the fan beam of the detecting antenna, and a radio wave received by the detecting antenna and the comparative antenna. And identification means for identifying the reflected wave from the radio wave reflector received by the detection antenna by comparing the reception levels. According to the present invention, the fan-shaped directivity of the detection antenna is adapted to the shape of the radio wave reflector, and at the same time, the fan-shaped directivity is such that the longitudinal direction is perpendicular to the longitudinal direction. A comparison antenna is provided. By comparing the reception levels of the two antennas, the identification means can identify the reflected wave from the radio wave reflector from the iron plate or the like of the overpass, and reduce malfunction. That is, most of the radio waves received by the detection antenna are radio waves reflected by the radio wave reflector, and most of the radio waves received by the comparison antenna are radio waves reflected by the road surface. When the road surface approaches a seam of an overpass, there is an iron plate extending in the width direction of the road surface, and reflects radio waves more than radio wave reflectors. Such a reflected radio wave from an iron plate or the like is received more by the comparison antenna, so that the reception level of the comparison antenna is higher than that of the detection antenna. Therefore 2
By comparing the reception levels of the two antennas, an unnecessary reflector such as an overpass joint and a radio wave reflector can be easily identified.

[0011] In the present invention, the discriminating means may detect a change in the reception level of the detection antenna and the reception level of the comparison antenna.
It is characterized in that regularity is extracted and it is determined whether or not a reflected wave from a radio wave reflector is being received. According to the present invention, the detection antenna mainly receives radio waves reflected from the radio wave reflector, and the comparison antenna receives radio waves from a certain range in the width direction of the road surface including the radio wave reflector. If the radio wave reflectors are arranged at regular intervals in the traveling direction of the vehicle, the signal level received by the detection antenna becomes lower at the interval between the radio wave reflectors, It shows a regular change that becomes the largest when the fan beam completely covers the radio wave reflector. Further, the level of the signal received by the comparison antenna also shows a regular change such that it becomes lower in the gap where no radio wave reflector exists. Therefore, it is possible to extract the regularity from the change in the reception level of both antennas and determine whether or not the reflected wave from the radio wave reflector is being received, and avoid erroneous detection of the radio wave reflector. Can be.

Further, the direction of the fan beam of the detection antenna and the comparison antenna of the present invention is directed obliquely forward at the same angle with respect to the traveling direction of the vehicle, and is received by the detection antenna and the comparison antenna. The apparatus further comprises a diversity type ground speed sensor for detecting a frequency shift due to the Doppler effect by switching a signal to be performed according to a signal level and detecting a ground speed of the vehicle. According to the present invention, since the detection antenna and the comparison antenna are directed obliquely forward with respect to the traveling direction of the vehicle, the radio wave reflector can be detected in front of the vehicle. The radio wave received by each antenna includes a frequency shift due to the Doppler effect on the traveling speed of the vehicle, and the ground speed of the vehicle can be detected from the frequency shift amount. The diversity ground speed sensor compares the signal levels received by the detection antenna and the comparison antenna, and switches the antenna that detects the ground speed based on the Doppler effect according to the signal level, so that the ground speed can be detected with high sensitivity. Can be.

The direction of the fan beam of the detection antenna and the comparison antenna of the present invention is directed obliquely forward and laterally with respect to the traveling direction of the vehicle, and is received by the antenna directed obliquely forward. A ground travel speed sensor that measures the absolute traveling direction based on the frequency shift of the signal, and a ground lateral direction that measures the absolute transverse speed based on the frequency shift of the signal received by the antenna that is directed sideways And a speed sensor. According to the present invention, one of the detection antenna and the comparison antenna is directed obliquely forward in the traveling direction of the vehicle, and the other is directed in the lateral direction of the vehicle. An antenna directed obliquely forward receives a radio wave whose frequency is shifted based on the Doppler effect in accordance with the traveling speed of the vehicle. The ground traveling speed sensor measures the traveling direction absolute speed based on the frequency shift of the received signal. Laterally oriented antennas include a frequency shift based on the Doppler effect on the absolute lateral speed of the vehicle. The ground lateral speed sensor measures a lateral absolute speed based on the frequency shift.
Since the absolute speed in the lateral direction and the absolute speed in the traveling direction can be measured with the two antennas, the state of motion of the vehicle with respect to the road surface can be accurately grasped, and the guidance of the vehicle can be effectively performed.

[0014]

FIG. 1 shows a schematic configuration of an embodiment of the present invention. Lane marker 1 which is a radio wave reflector
1 is made of a strip-shaped material that reflects radio waves, and is laid on the road surface 12 at regular intervals along the guide direction of the vehicle. The length of the lane marker 11 is, for example, 10
It is about 0 cm, the width is about 30 cm, and the thickness is 2
mm. On the lane marker 11, radio waves are radiated from the marker detection antenna 13 with a fan beam-like directivity 14 adapted to the shape of the lane marker 11, and radio waves reflected on the antenna beam irradiation area 15 on the lane marker 11 are used for marker detection. The signal is received by the antenna 13.
The shape of the antenna beam irradiation area 15 is an ellipse or an ellipse suitable for a rectangular lane marker. A radar sensor 16 is connected to the marker detecting antenna 13 to determine whether the antenna beam irradiation area 15 exists on the lane marker 11 or exists at a position shifted from the lane marker 11 based on a change in the level of a received radio wave. Then, the position of the vehicle is detected.

FIG. 2 shows an example of a schematic electrical configuration inside the radar sensor 16. A transmission oscillator 20 generates a high-frequency electric signal of a millimeter-wave band or higher, and a circulator 21
The high-frequency power is supplied to the marker detection antenna 13 via the. The reflected wave of the radio wave radiated on the lane marker 11 from the marker detecting antenna 13 in accordance with the fan beam-shaped directional characteristic 14 of FIG.
3 is received. An electric signal corresponding to the radio wave received by the marker detection antenna 13 is transmitted to a directional coupler 23 to which a high-frequency signal oscillated by a local oscillator 22 is given.
It is guided through the circulator 21 and mixed by the mixer 24. From the output of the mixer 24, the frequency component of the difference between the received signal and the high-frequency signal from the local oscillator is selected, and the detector 25 detects the received level. Since the antenna beam irradiation area 15 in FIG. 1 is substantially rectangular and conforms to the shape of the lane marker 11, the reception level of the reflected wave from the lane marker 11 and the reception level of the reflected wave from the road surface 12 are different. The S / C ratio, which is the ratio, can be improved.

FIG. 3 shows a schematic configuration of another embodiment of the present invention. In the present embodiment, the lane marker 11 is transmitted from the marker detecting antenna 13 by the radar sensor 16.
In addition to transmitting and receiving radio waves having the fan beam-like directivity 14 adapted to the shape of the antenna, the radar sensor 16 transmits the antenna beam irradiation area via the fan beam-like directivity 28 of the marker comparison antenna 27. 2
9 is formed. The antenna beam irradiation area 29 is an ellipse or an ellipse similarly to the antenna beam irradiation area 15 from the marker detection antenna 13, and has a longitudinal direction orthogonal to the longitudinal direction. As a result, in the marker detection antenna 13, the antenna beam irradiation area 15 conforms to the shape of the lane marker 11 and almost receives the reflected radio wave from the lane marker 11, whereas the marker comparison antenna 27 has the lane marker The reflected radio waves from the road surface 12 are mostly received, and the reflected radio waves from the road surface 12 are mostly received. Since the intensity of the reflected radio wave from the lane marker 11 is greater than that of the road surface 12, when the marker detecting antenna 13 irradiates the lane marker 11, as shown in FIG. The level Pr1 is higher than the reception level Pr2 of the marker comparison antenna 27. That is, there is a relationship of the following first formula.

Pr1 / Pr2 >> 1 (1) FIG. 3B shows a case where an overpass seam 30 exists on the road surface 12. The overpass seam 30 is made of a material that reflects radio waves more easily than the lane marker 11, such as an iron plate extending in the horizontal direction perpendicular to the lane marker 11. Since the longitudinal direction of the antenna beam irradiation area 29 based on the fan beam-like directivity 28 of the marker comparison antenna 27 coincides with such a laterally extending reflector, the reflected radio signal level increases. Antenna beam irradiation area 15 based on fan beam-like directivity 14 of marker detecting antenna 13
Although it also includes the overpass 30, the area is smaller than the antenna beam irradiation area 29, and the increase in the reflection intensity is small. As a result, the relationship of the intensity ratio as shown in the following second equation is obtained.

Pr1 / Pr2 << 1 (2) The configuration of the radar sensor 26 connected to the marker comparison antenna 27 is basically the same as that of the radar sensor 16 connected to the marker detection antenna 13.

FIG. 4 shows another embodiment of the present invention. In the embodiment shown in FIG. 3, the marker detecting antenna 13 detects the lane marker 11 from the regularity of the change of the reception level of the two antennas. Here is an idea of determining whether or not there is. A plurality of lane markers 11 are periodically laid on the road surface 12 at intervals of, for example, 50 cm along the traveling direction of the vehicle.

When the antenna beam irradiation area 15 from the marker detecting antenna 13 shown in FIG. 3 matches the lane marker 11, the radar sensor 16 detects the area as shown in FIG. Receiving level becomes maximum. When the antenna beam irradiation area 15 includes an interval between the lane markers 11, the reception level of the radar sensor 16 decreases. Even when the marker detection antenna 13 irradiates an intermediate position between the two lane markers 11, the antenna beam irradiation area 15
If the length in the longitudinal direction is longer than the length of the interval between the lane markers 11, the reception level is reduced but a certain reception level is obtained as shown in FIG. The reception level received by the marker comparison antenna 27 in which the longitudinal direction of the antenna beam irradiation area 29 is orthogonal to the longitudinal direction of the antenna beam irradiation area 15 is constant within a range where the antenna beam irradiation area 29 includes the lane marker 11. Yes, it decreases when approaching the space between the lane markers 11.

As long as the vehicle is traveling at a constant speed and in a constant direction, a periodic regularity of the reception level as shown in FIG. 4B appears. It can be determined whether or not a state is detected.

FIGS. 5 and 6 show a still further embodiment of the present invention, in which the fan beams from the two antennas are directed obliquely forward at the same angle to each other, so that the two antennas can be connected to a diversity ground. 1 shows a configuration that constitutes a speed sensor and also serves as a highly sensitive ground speed sensor.
FIG. 5 shows that the fan beam-like directivity 14 from the marker detection antenna 13 and the fan beam-like directivity 28 from the marker comparison antenna 27 are inclined obliquely forward by an angle θ with respect to the traveling direction of the vehicle. Shows the state of irradiation. FIG. 6 shows a schematic electrical configuration for switching signals received by the marker detection antenna 13 and the marker comparison antenna 27 to measure the ground speed by the diversity method.

As shown in FIG. 5, the radio waves received by the marker detecting antenna 13 and the marker comparing antenna 27 are reflected waves obliquely forward from the traveling direction of the vehicle. Including transfer. As shown in FIG. 6, an electric wave based on a radio wave received by the marker detection antenna 13 is different from a radio wave transmitted based on a high-frequency output given to the marker detection antenna 13 from the transmission oscillator 20 via the circulator 21. When the signal passes through the circulator 21, the leakage of the high-frequency signal from the transmission oscillator 20 is added to the signal and sent to the mixer 24. The difference frequency component is detected by the detector 25 as a frequency shift due to the Doppler effect. The marker comparison antenna 27 includes
A high-frequency signal generated by the transmission oscillator 20 is supplied from the directional coupler 33 via the circulator 31. The electric signal corresponding to the radio wave received by the marker comparison antenna 27 is also mixed with the high-frequency signal leaked by the circulator 31 by the mixer 34, and the frequency shift is detected by the detector 35.

The output levels of the detector 25 and the detector 35 are compared by a level comparing means 37, and the higher level is selected. The ground speed detecting means 38 detects the ground speed based on the Doppler effect. Level comparison means 3
7 and the ground speed detecting means 38 constitute a diversity type ground speed sensor 39, and can realize a diversity type high sensitivity ground speed sensor using two antennas.

FIGS. 7 and 8 show a still further embodiment of the present invention, in which the direction of the two fan beams is directed obliquely forward and obliquely laterally, and the traveling direction absolute speed and the lateral direction are obtained with two antennas. 3 shows a configuration for measuring the absolute speed. FIG. 7 shows that the marker detecting antenna 13 directs the fan beam-shaped directional characteristic 14 in the lateral direction Vy with respect to the traveling direction Vx of the vehicle, and the marker comparison antenna 27 directs the fan beam-shaped directional characteristic 28 in the traveling direction Vx of the vehicle. In this case, the light is directed obliquely downward. The reflected wave received by the marker detecting antenna 13 does not include a frequency shift due to the movement of the vehicle in the traveling direction, but includes only a frequency shift due to the lateral movement of the vehicle. The reflected wave received by the marker comparison antenna 27 includes only the frequency shift due to the movement in the traveling direction of the vehicle, and does not include the frequency shift due to the lateral movement.

FIG. 8 shows a schematic electrical configuration for measuring the absolute ground speed in the traveling direction and the lateral direction. This configuration is similar to the configuration of FIG. 6, and the corresponding portions are denoted by the same reference characters and description thereof will be omitted. In the case of the present embodiment, an absolute ground traveling speed is detected by the ground traveling speed sensor 41 from the frequency shift of the signal received by the marker comparison antenna 27. From the frequency shift of the signal received by the marker detecting antenna 13,
Detects absolute lateral ground speed. If the arrangement of the antennas shown in FIG. 7 is changed, it is also possible to detect the ground traveling speed by the marker detecting antenna 13 and detect the lateral ground speed by the marker comparing antenna 27.

According to the present embodiment, the moving state of the vehicle can be reliably detected separately in the traveling direction and in the lateral direction perpendicular to the traveling direction, and the movement state of the vehicle can be accurately grasped. Guide guidance can be provided. Further, since the ground traveling speed can be absolutely detected, efficient control by an antilock brake system (ABS) and calculation of an accurate traveling distance by integrating the speed can be performed.

[0028]

As described above, according to the present invention, since the radio wave reflector is arranged in a belt shape on the road surface, the directivity of the detection antenna is set to a fan beam shape adapted to the shape of the radio wave reflector. The S / C ratio, which is the reception level ratio between the reflected wave from the radio wave reflector and the reflected wave from the road surface, can be improved by efficiently irradiating the radio wave onto the radio wave reflector.

Further, according to the present invention, the antenna for comparison has a fan beam-like directivity and is arranged so that its longitudinal direction is orthogonal to the longitudinal direction of the fan beam-like directivity of the detection antenna. Even if there is an iron plate or the like at the sea bridge extending in the width direction on the road surface, it can be easily distinguished from the reflection from the radio wave reflector.

Further, according to the present invention, the reception levels of the detection antenna and the comparison antenna are compared, and the reflection from the radio wave reflector arranged in a belt shape due to regularity and the reflection from the interval between the radio wave reflectors are compared. Reflection can be easily distinguished, and vehicle position detection based on reflection from the radio wave reflector can be accurately performed.

According to the present invention, the traveling speed of the vehicle is measured based on the Doppler effect by directing the two antennas of the detection antenna and the comparison antenna obliquely forward in the traveling direction of the vehicle at a common angle. In this case, highly sensitive detection can be performed by the diversity method.

According to the present invention, since the directions of the fan beam directivity characteristics of the two antennas are divided into the traveling direction of the vehicle and the lateral direction of the vehicle, it is possible to measure the absolute velocity in the lateral direction and the absolute velocity in the traveling direction. Thus, it is possible to accurately grasp the motion state of the vehicle and perform effective guidance.

[Brief description of the drawings]

FIG. 1 is a simplified perspective view showing a schematic configuration of an embodiment of the present invention.

FIG. 2 is a block diagram showing a schematic electrical configuration of the radar sensor 16 of FIG.

FIG. 3 is a simplified perspective view showing a schematic configuration of another embodiment of the present invention.

FIG. 4 is a simplified perspective view and a graph showing a schematic configuration of still another embodiment of the present invention.

FIG. 5 is a simplified perspective view showing a configuration of still another embodiment of the present invention.

FIG. 6 is a block diagram illustrating a schematic electrical configuration for detecting a ground speed in the embodiment of FIG. 5;

FIG. 7 is a simplified plan view showing a schematic configuration of still another embodiment of the present invention.

8 is a block diagram showing a schematic electrical configuration for detecting a ground traveling speed and a ground lateral speed in the embodiment of FIG. 7;

FIG. 9 is a simplified front view and a plan view showing the concept of the prior art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Lane marker 12 Road surface 13 Marker detecting antenna 14, 28 Fan beam directivity 15, 29 Antenna beam irradiation area 16, 26 Radar sensor 20 Transmitting oscillator 22 Local oscillator 24, 34 Mixer 25, 35 Detector 27 Marker comparing antenna 30 Overpass 37 Sea level comparison means 38 Ground speed detection means 39 Diversity ground speed sensor 41 Ground speed sensor 42 Ground speed sensor

Claims (5)

[Claims] 1. A sensor for detecting a band-shaped radio wave reflector which is installed on a road surface and reflects a radio wave to guide a traveling route of a vehicle, wherein a fan beam shape adapted to the shape of the radio wave reflector is provided. A sensor for detecting a radio wave reflector, comprising: a detection antenna having a directional characteristic capable of irradiating a radio wave to the radio wave reflector. 2. A comparison antenna having a fan beam-like directivity whose longitudinal direction is orthogonal to the longitudinal direction of the fan beam of the detection antenna, and a radio wave is received by the detection antenna and the comparison antenna. 2. A sensor for detecting a radio wave reflector according to claim 1, further comprising: identification means for identifying a reflected wave from the radio wave reflector received by the detection antenna by comparing. 3. The identification means extracts regularity from changes in reception levels of a detection antenna and a comparison antenna, and determines whether or not a reflected wave from a radio wave reflector is being received. The sensor for detecting a radio wave reflector according to claim 2. 4. The detection antenna and the comparison antenna are directed obliquely forward at the same angle with respect to the traveling direction of the vehicle, and are received by the detection antenna and the comparison antenna. 4. The radio wave reflector detecting sensor according to claim 2, further comprising a diversity type ground speed sensor for detecting a frequency shift due to a Doppler effect by switching a signal in accordance with a signal level and detecting a ground speed of the vehicle. . 5. The fan-shaped directing directions of the detection antenna and the comparison antenna are directed obliquely forward and laterally with respect to the traveling direction of the vehicle. Ground travel speed sensor that measures absolute traveling direction based on frequency shift, and ground lateral speed sensor that measures absolute transverse speed based on frequency shift of a signal received by a horizontally oriented antenna 4. The method according to claim 2, wherein
A sensor for detecting a radio wave reflector according to the above.