JP2015059822A - Radar device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radar device which allows a moving vehicle to detect an object through an obstacle.SOLUTION: A radar device 100 detects an object through an obstacle by use of a UWB radar. In other places than a place where an object is likely to exist in a blind corner, the radar device transmits a radar wave having a polarization angle different from that of an incoming vehicle. In the above place, the radar device transmits a radar wave having TM polarization.

Description

  The present invention relates to a radar apparatus that detects an object through an obstacle by a UWB radar.

  There is known a radar device that detects an object to be detected over an obstacle such as a wall by radio waves. In such a radar apparatus, a transmission radio wave transmitted through an obstacle such as a wall is transmitted from the transmission apparatus, and a reception apparatus receives the radio wave transmitted through the obstacle and reflected from the detection target. As one of transmitted radio waves that easily pass through an obstacle, for example, there is an UWB (Ultra Wideband) band radio wave.

  However, even for radio waves with good transparency, since the transparency is lowered depending on the material and thickness of the obstacle, a technique for improving the transparency has been conventionally devised (see, for example, Patent Document 1). Patent Literature 1 discloses a broadband radar device that sets at least one of a condition for transmitting a transmission signal and a condition for a reception unit to receive a reception signal based on a reception signal reflected from a detection target.

  In addition, a technique for changing the polarization direction of an antenna has been devised (see, for example, Patent Document 2). In Patent Document 2, an antenna bias is detected in an underground survey method in which an electromagnetic wave is transmitted to the outside of a buried pipe and the reflected wave is received to detect a survey target such as a cavity or a buried object around the pipe. An underground survey method for changing the wave direction and acquiring a received wave with a good S / N ratio is disclosed.

JP 2011-242224 A JP 2002-257842 A

  By the way, there is an attempt to mount a wall transmission type radar using a UWB band radio wave on a vehicle. By mounting a wall-transmitting radar on-board, the radar device can detect an object for detecting a blind spot at a wall, for example, at an intersection with poor visibility due to the presence of a wall.

  Even when mounted on a vehicle, it is preferable that the radar has good transparency. However, as in the technique described in Patent Document 1, in the method of setting the condition for transmitting the transmission signal based on the reception signal and the condition for the reception unit to receive the reception signal, while setting an appropriate condition A moving vehicle passes through a place where a detection object is detected. The same applies to the technique described in Patent Document 2. While the received wave having a good S / N ratio is selected by changing the polarization direction of the antenna, the vehicle determines the place where the detection target is detected. Will pass.

  Therefore, the conventional method has a problem that the detection of the detection target may not be in time.

  In view of the above problems, an object of the present invention is to provide a radar device in which a moving vehicle can detect a detection target through an obstacle.

  The present invention is a radar device that detects an object by passing an obstacle through a UWB radar, and has a polarization angle different from the polarization angle of the radar of the oncoming vehicle except in a place where an object may exist in the blind spot. A radar is transmitted, and a TM polarized radar is transmitted at the location.

  It is possible to provide a radar device that allows a moving vehicle to detect a detection target through an obstacle.

It is an example of the schematic perspective view of the vehicle by which a radar apparatus is mounted. It is an example of the block diagram of a radar apparatus. It is an example of the figure explaining the polarization angle of a radar. It is an example of a graph in which the transmittance of radio waves of TM polarization and 45 degree polarization is dotted with respect to the incident angle α. It is an example of the flowchart figure explaining the operation | movement procedure at the time of a radar apparatus switching the polarization angle of a radar.

 Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

[Outline of radar apparatus of this embodiment]
Conventionally, radar transmitted by an on-vehicle radar device is polarized at a certain polarization angle, but TM polarization (90-degree polarization) is known as a polarization angle that easily transmits obstacles such as walls. It has been. Therefore, the radar apparatus of the present embodiment switches the radar polarization angle as follows.
A. The radar device detects that an obstacle such as a wall (mainly an intersection) is approached from its own vehicle position and road map DB, and changes the radar polarization angle to TM polarization.
B. When passing through a place where there is an obstacle such as a wall, the radar device returns the polarization angle of the radar to the polarization angle before the change.

  This makes it possible to improve radar permeability when approaching a place where an obstacle such as a wall (an example of an object in the scope of claims) is present, and a detection target that may exist in a blind spot Is easier to detect.

  In addition, it is not limited to places where obstacles such as walls exist, and it is conceivable that the radar device always transmits TM-polarized radar. However, if TM-polarized radar is always transmitted, the reflected wave and the oncoming vehicle This is difficult because there is a risk of interference with the transmission wave of the radar.

  Therefore, the radar apparatus of this embodiment improves the transparency of the radar only in a place where it is desired to transmit the radar without interfering with the radar transmitted by the oncoming vehicle except in a place where an obstacle such as a wall exists. It is possible to detect an object to be detected.

[Configuration example]
FIG. 1 shows an example of a schematic perspective view of a vehicle equipped with a radar device. The vehicle has the radar device 100 mounted on, for example, the inside of the grill or the front bumper. The radar apparatus 100 transmits a radar having a certain polarization angle. For example, the polarization angle can be changed by rotating the main body of the radar apparatus 100 with a motor or the like. The direction of rotation is in a plane parallel to the front of the vehicle (in the xy plane of the figure).

  FIG. 2 shows an example of a block diagram of the radar apparatus. The radar apparatus 100 includes a transmission antenna 11, a plurality of reception antennas 12a and 12b, a transmission unit 13, a plurality of reception units 14a and 14b, an AD conversion unit 15, a processing unit 17, and a control unit 16.

  The transmission unit 13 generates, for example, a wideband impulse signal as a transmission signal, amplifies it, and transmits it from the transmission antenna 11. As a result, the transmission signal is sent out into the air as a predetermined deflection wave.

  The receiving antennas 12a and 12b receive a reflected wave that has passed through a shielding object such as a wall and reflected by a detection object as a reception signal. The receiving units 14a and 14b amplify and downconvert the received signals received by the receiving antennas 12a and 12b. It is preferable that there are at least two receiving antennas 12a and 12b in order to detect the direction of the object to be detected. However, when the radar apparatus 100 scans the front of the vehicle while changing the transmission direction of the transmission signal, the receiving antennas 12a and 12b are used. May be one.

  The AD converter 15 performs A / D conversion on the down-converted received signal. The processing unit 17 detects the distance to the detection target and the direction of the detection target from the A / D converted reception signal. Alternatively, Σ / Δ may be converted into a direction using a phase comparison monopulse method. Specifically, the processing unit 17 detects the distance from the time from when the transmission unit 13 transmits a transmission signal until the reception units 14a and 14b receive the reception signal to the detection target. Further, the azimuth of the detection object is detected based on the distance between the reception antenna 12a and the reception antenna 12b and the time difference at which the plurality of reception antennas 12a and 12b receive the reception signals.

  The laser device 100 is mounted on the vehicle so as to be rotatable at least 45 degrees by the motor 200. The rotatable angle varies depending on the polarization angle of a radar traveling outside a specific location described later (hereinafter simply referred to as “polarization angle of a normal radar”). The angle of 45 degrees is when the polarization angle of the normal radar is 45 degrees.

  The detection object detected by the radar device 100 is, for example, another vehicle, a motorcycle, a bicycle, a tricycle, a one- or two-seater small electric vehicle, or a movement support vehicle such as Segway (registered trademark). For pedestrians, it is difficult to reflect the radar, but if the radar can be reflected, it is included in the detection target. In many cases, the detection target is a moving object.

  The radar device 100 is connected to the navigation device 300. The navigation device 300 has road map data or can download road map data from a server (not shown) via a mobile phone network or a wireless LAN network. The navigation device 300 detects the position (latitude, longitude, altitude) of the host vehicle using, for example, a GNSS (Global Navigation Satellite System).

  At least intersections are registered in the road map data. It is preferable that information indicating whether the line of sight is bad due to an obstacle such as a wall at the intersection is added. Also, in the road map data, general road shapes such as a T-shaped road and a parking lot that may have a poor view are registered in addition to the intersection. Hereinafter, an intersection with a blind spot or an intersection with a blind spot may be referred to as a “specific place”.

  The navigation device 300 notifies the processing unit 17 of the radar device 100 when the position of the vehicle approaches a specific place. Alternatively, the radar apparatus 100 may periodically inquire the navigation apparatus 300 whether the position of the vehicle is in front of a specific place.

  Further, in the present embodiment, since it is only necessary to know whether or not the position of the vehicle is in front of the specific place, the roadside device in the specific place and the own vehicle communicate (road-to-vehicle communication), and the own vehicle is in front of the specific place. You may receive the information that it is driving. For example, it can be received by a VICS (Vehicle Information and Communication System) (registered trademark) optical beacon or radio wave beacon. Further, for example, information indicating that there is a blind spot may be received by communicating with a roadside device of a specific facility such as a gas station or a parking lot.

  The processing unit 17 includes a microcomputer having a CPU, a RAM, a ROM, an input / output interface, and the like. The ROM stores an embedded program, and the CPU executes this program to control the polarization angle of the radar. Specifically, the processing unit 17 includes a specific location detection unit 21 and a motor control unit 22 that are realized by a CPU executing a program and cooperating with hardware resources of the radar device 100.

  The specific location detection unit 21 detects that the host vehicle is traveling in front of the specific location by communicating with the navigation device 300 or using the result of road-to-vehicle communication. When the host vehicle is traveling in front of a specific place, the motor control unit 22 controls the motor 200 so that the polarization angle of the radar transmitted by the radar apparatus 100 becomes TM polarized wave, thereby controlling the radar apparatus 100. Rotate.

[Radar polarization angle]
FIG. 3 is an example for explaining the polarization angle of the radar. An incident angle α and a polarization angle β are known as parameters when radio waves are incident on an obstacle such as a wall.
The incident angle α is an angle formed by the normal n to the wall surface and the traveling direction of the radio wave.
The polarization angle β is an angle formed by the vibration plane (polarization plane) when radio waves propagate while oscillating perpendicularly to the traveling direction and the vertical direction of the wall.

  The incident angle α can vary depending on the relative position between the vehicle on which the radar device 100 is mounted and an obstacle such as a wall. For example, when the vehicle is moving straight on the wall in front of the vehicle, the incident angle α is zero degrees. However, if the angle between the wall and the vehicle is changed by a steering operation, the incident angle α is not zero.

  On the other hand, the polarization angle β is determined at the time of designing the radar apparatus 100 so that the radar is transmitted to an obstacle such as a wall with a constant polarization plane. In other words, the radar polarization angle β can be changed depending on the design. However, conventionally, the radar polarization angle β transmitted by the radar apparatus 100 after being mounted on a vehicle has not been changed.

  Although the radar polarization angle β can be arbitrarily set, conventionally, the polarization angle β of the radar device 100 mounted on the vehicle is generally designed to be 45 degrees. This is because it is considered that the radar device 100 of the oncoming vehicle approaching from the oncoming lane transmits the radar. For example, when the polarization angle β is set to zero degree, the reflected wave transmitted from the radar device 100 of the host vehicle and reflected by the object to be detected matches the polarization plane of the transmission wave transmitted from the radar device 100 of the oncoming vehicle. There is a risk that the radar device 100 of the host vehicle receives the transmission wave of the oncoming vehicle as a reflected wave (there is a risk of interference). The same thing occurs when the polarization angle transmitted by the radar apparatus 100 is 90 degrees, 180, or 270 degrees.

  On the other hand, for example, when the polarization angle β is 45 degrees, the reflected wave transmitted from the radar device 100 of the own vehicle and reflected by the detection target has a polarization angle of 45 degrees when viewed from the own vehicle. The polarization angle of the transmission wave transmitted by the vehicle radar device 100 is 315 degrees when viewed from the host vehicle. That is, since the planes of polarization are orthogonal, it is possible to reduce the possibility that the radar device 100 of the host vehicle receives the transmission wave of the oncoming vehicle as a reflected wave. Therefore, preferable polarization angle β for avoiding interference includes 135 degrees, 225 degrees, or 315 degrees in addition to 45 degrees.

  On the other hand, the radio wave transmission characteristics of a transmissive radar that transmits obstacles such as walls are experimentally the best if the polarization angle β is 90 degrees, regardless of the material and thickness of the obstacle. It has become clear. This radio wave having a polarization angle β = 90 degrees may be referred to as the TM polarization described above.

  FIG. 4 is an example of a graph in which the transmittance of radio waves of TM polarization and 45 degree polarization is dotted with respect to the incident angle α. The obstacle is concrete and the thickness is 20 [mm].

  When the incident angle is about 20 degrees or less, the transmittances of the TM polarization and 45 degree polarization are both about 0.45 (about 45%). However, the transmittance of 45-degree polarized radio waves gradually decreases as the incident angle α increases when the incident angle α is approximately 20 degrees or more. On the other hand, the transmittance of TM polarization tends to rise until the incident angle α reaches about 70 degrees. That is, it can be seen that TM polarized light has a property of transmitting an obstacle such as a wall unless the incident angle is extremely large.

  Therefore, TM polarization may be used to improve the transmittance, but TM polarization (polarization angle = 90 degrees) may be used because it may interfere with the radar of the oncoming vehicle as described above. There wasn't.

  Therefore, the radar device 100 according to this embodiment suppresses interference by transmitting a radar having a polarization angle of 45 degrees when traveling in a place other than a specific place, and transmits an obstacle such as a wall to be detected. A TM polarized radar is transmitted at a specific location where an object should be detected. Thereby, it is possible to suppress interference and easily detect the detection target through the obstacle.

[Operation procedure]
FIG. 5 is an example of a flowchart for explaining an operation procedure when the radar apparatus 100 switches the polarization angle of the radar. The process of the flowchart in FIG. 5 is repeatedly executed periodically while the radar apparatus 100 is operating.

  The specific location detection unit 21 inquires of the navigation device 300 and acquires the current vehicle position (S10).

  The specific location detection unit 21 determines whether or not the current vehicle position is near the specific location (S20). Since the specific place is mainly an intersection, it is determined whether or not the intersection is approaching. In addition, when the road map data does not include information on whether or not the intersection is inferior, it may be determined whether or not the intersection is approached.

  If the current vehicle position is not near the specific location (No in S20), the processing unit 17 performs the object detection signal processing while maintaining the polarization angle of the normal radar (S30). The object detection signal processing is processing for transmitting a radar, receiving reflection, and calculating a distance and direction from the detection object.

  When the current vehicle position is near a specific location (Yes in S20), the motor control unit 22 controls the motor 200 to rotate the radar device 100 by 45 degrees, thereby setting the radar polarization angle β to 90 degrees. (S40). The reason why the rotation angle is 45 degrees is that the polarization angle of the normal radar is 45 degrees, and if the rotation angle is further rotated by 45 degrees, the TM polarization is obtained.

  Next, the processing unit 17 performs object detection signal processing with a radar having a polarization angle of 45 degrees (S50). That is, the distance and azimuth from the detection target are calculated by transmitting and receiving TM polarized radar.

  Next, the specific location detection unit 21 inquires of the navigation device 300 and acquires the current vehicle position (S60).

  The specific location detection unit 21 determines whether or not the specific location has passed based on the current vehicle position (S70).

  Until it passes through the specific place (No in S70), the processing unit 17 has processed the object detection signal in Step S50, acquired the current vehicle position in Step S60, and passed through the specific place in Step S70. Repeat the determination.

  When the vehicle passes through a specific location (Yes in S70), the motor control unit 22 controls the motor 200 to rotate the radar device 100 by 45 degrees in the direction opposite to that in step S40. (S80).

  Thereafter, the process proceeds to step S30, and the processing unit 17 performs object detection signal processing. Thereafter, the processes of steps S10 to S70 are repeatedly executed.

  As described above, the radar apparatus 100 according to the present embodiment detects a detection target with a TM polarized wave that easily transmits an obstacle such as a wall at a specific location, and has a polarization angle that is difficult to interfere with other locations. Since the radar is transmitted, it is possible to detect the object to be detected through the obstacle by improving the transparency only in a place where the transparency is required without crossing with other vehicles when traveling outside the specific place.

[Change direction of radar polarization angle]
In the present embodiment, it has been described that the entire radar apparatus 100 is rotated by the motor 200. However, the polarization angle of the radar can be changed by the following method.
(i) Rotate the transmitting antenna 11 and the receiving antennas 12a and 12b
(ii) Two types of antenna patterns for normal and TM polarization are retained and switched.
(iii) Change the polarization angle by devising a method for feeding power to the antenna. For example, when two antennas whose antenna patterns are inclined at 45 degrees and 135 degrees are arranged, if a power is supplied only to the antenna of 45 degrees in a normal state and two antennas are supplied near a specific place, TM polarization can be created only near

  Further, in the present embodiment, the radar device 100 is mounted in front of the vehicle, but the radar device 100 may be mounted in places other than the front such as the rear side of the vehicle. In addition to the UWB radar, the radar wavelength may be other than UWB as long as it is a radar that can be mounted on a vehicle and has a wavelength capable of detecting an object to be detected through an obstacle.

100 Radar device 200 Motor 300 Navigation device

Claims (1)

A radar device that detects an object through an obstacle by UWB radar,
Transmit a radar with a polarization angle different from the polarization angle of the radar of the oncoming vehicle except where there is a possibility that an object exists in the blind spot, and transmit a TM polarized radar at the location,
Radar device characterized by that.

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