JPH06273512A - On-vehicle radar - Google Patents

Abstract

PURPOSE:To provide an on-vehicle radar which can detect presence of a vehicle positively even when a narrow obstacle is present in the front. CONSTITUTION:Continuous wave transmitted from a continuous wave transmitter 11 and radiated from an antenna 12 is reflected on a forward obstacle and received by the antenna. The reflected wave is subjected to frequency conversion by a mixer 13 using a reference wave transmitted from a reference wave transmitter 14 and then analyzed by a frequency analyzing means 15 thus extracting information relevant to the distance between vehicles, the relative speed, the moving direction of obstacle, etc. The information is presented on a display means 16. A control means 17 controls a driving means 18 for scanning the antenna in the direction to the right and left as well as the frequency analyzing means. Since the antenna is scanned in the direction the right and left, even an obstacle present at the dead angle of antenna can be detected positively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an on-vehicle radar mounted on a vehicle for preventing a rear-end collision, and more particularly to an on-vehicle radar capable of reliably detecting even a small vehicle such as a motorcycle.

[0002]

2. Description of the Related Art In recent years, an increasing number of vehicles are equipped with optical, radio wave, or ultrasonic radars to prevent rear-end collisions between vehicles. Such a radar radiates a so-called pencil beam of about 2 ° from a transmitter installed in the front of the vehicle body, receives a reflected wave from a vehicle in front of it, and receives it with a receiver also installed in the front of the vehicle. And the information such as the distance to the vehicle ahead, the speed or the traveling direction is calculated from the phase difference between the received wave and the received wave.

The shape of the pencil beam is usually about 100 m ahead, and the beam is often set to about 2 ° so that a vehicle existing within a range of 3.5 m which is a typical lane width can be detected.

[0004]

If the vehicle running ahead has a width of more than half the lane width and a high reflection level like a four-wheeled vehicle, the inter-vehicle distance becomes 100 m or less. It is possible to detect obstacles ahead even if the beam width emitted from the transmitter becomes narrow. FIG. 3 is an explanatory view of a detection range of a conventional vehicle-mounted radar, and it is possible to detect an obstacle in a shaded area.

However, the vehicle running ahead is a vehicle having a small width and a small reflection level like a motorcycle, and when approaching within 100 m, the vehicle is hatched in FIG. It becomes impossible to detect the vehicle by entering the blind spot of the beam indicated by the section. The present invention has been made in view of the above problems, and is an on-vehicle radar capable of reliably detecting the presence of a vehicle even when the width of an obstacle ahead is small and the reflection level is small. The purpose is to provide.

[0006]

A vehicle-mounted radar according to a first aspect of the present invention receives a transmitter emitting a pencil-shaped transmission beam and a reflection beam emitted from a transmitter reflected by an obstacle ahead. A receiver, an analysis means for analyzing information on an obstacle ahead of the transmitter based on a transmission beam transmitted from the transmitter and a reflected beam received by the receiver, and at least one of the transmitter and the receiver is left and right predetermined. Scanning means for scanning within the range.

In the on-vehicle radar according to the second aspect of the present invention, the scanning means scans at least one of the transmitter and the receiver within a predetermined left and right range, and the forward monitoring for fixing the transmitter and the receiver to the front. The period is repeated at regular time intervals. The on-vehicle radar according to the third invention is analyzed by the analyzing means whether the reflected beam intensity received by the receiver is less than or equal to a threshold value determined as a function of the inter-vehicle distance analyzed by the analyzing means. Further comprises a judging means for judging whether or not the relative speed with respect to the obstacle ahead is in the decreasing process, and the judging means judges that the reflected beam intensity is below the threshold value and the relative speed is in the decreasing process. When it is determined that there is a scan, the scanning by the scanning means is started.

[0008]

In the vehicle-mounted radar according to the first invention,
The blind spot of the radar beam is eliminated by scanning at least one of the transmitter and the receiver left and right. In the vehicle-mounted radar according to the second aspect of the invention, scanning and forward monitoring are repeated at regular time intervals.

In the vehicle-mounted radar according to the third aspect of the invention, an obstacle having a small reflection level due to its narrow width is detected during forward monitoring, and it is determined that the obstacle tends to approach. Scanning is started when

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of an embodiment of an on-vehicle radar according to the present invention, showing a case where a continuous wave radar is applied. The continuous wave emitted from the continuous wave oscillator 11 is radiated forward from the antenna 12 in the form of a pencil beam. The beam angle is about 2 ° and spreads 100 m ahead to a width of 3.5 m which is a general lane width.

The reflected wave reflected by the obstacle existing in the beam is received by the antenna 12, mixed by the mixer 13 with the reference wave transmitted by the reference wave transmitter 14, and converted in frequency. The frequency-converted intermediate frequency is guided to the frequency analysis means 15, and information such as the inter-vehicle distance, the relative speed, and the traveling direction of the obstacle is extracted. These pieces of information are displayed on the display means 16 which is, for example, a CRT display.

The control unit 17 which is, for example, a microcomputer system controls the frequency analysis unit 15 and drives the antenna 12 to swing left and right.
Also controls. FIG. 2 is an operation timing chart of the driving means 18, in which a forward monitoring period in which the antenna 12 is fixed straight ahead and a beam is emitted and a scanning period in which the driving means swings the antenna 12 left and right are alternately repeated. Be done.

That is, by scanning the antenna 12 left and right, even if there is an obstacle in the blind spot generated when the antenna 12 is fixed straight ahead, the obstacle can be reliably detected. Furthermore, frequency analysis means 15
The inter-vehicle distance data and the reflected wave intensity data extracted by the above are input to the control unit, the reflection intensity below the predetermined threshold is detected at the predetermined inter-vehicle distance, and the inter-vehicle distance data tends to decrease. It is also possible to start the scanning of.

That is, while there is no obstacle in the blind spot, the forward direction is monitored straightly, and when there is a possibility that there is an obstacle in the blind spot, the antenna 12 is scanned to surely detect the obstacle. In the above embodiment, the antenna is mechanically scanned by the servo motor, but
It is also possible to scan the beam electronically.

Although it is well known that the antenna changes its direction by linking with the steering device of the vehicle, the scanning of the antenna for eliminating the blind spot according to the present invention is superposed on the change of the antenna direction by the steering device. It is clear that it is okay.

[0016]

According to the on-vehicle radar of the first aspect of the present invention, it is possible to reliably detect an obstacle at the blind spot of the beam by scanning the beam left and right. According to the on-vehicle radar according to the second aspect of the present invention, it is possible to reliably monitor the front and blind spots by repeating the front monitoring and scanning at regular time intervals.

According to the on-vehicle radar of the third aspect of the present invention, the blind spot monitoring is started when an obstacle of a predetermined size is detected during the forward monitoring, and the blind spot can be monitored without reducing the forward monitoring power. Can be monitored.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of a vehicle-mounted radar according to the present invention.

FIG. 2 is an operation timing chart of a driving unit.

FIG. 3 is an explanatory diagram of a detection range of a conventional vehicle-mounted radar.

[Explanation of symbols]

 11 ... Continuous wave oscillator 12 ... Antenna 13 ... Mixer 14 ... Fundamental wave oscillator 15 ... Frequency analysis means 16 ... Display means 17 ... Control means 18 ... Driving means

Claims (3)

[Claims] 1. A transmitter that emits a pencil-shaped transmission beam, a receiver that receives a reflected beam emitted from the transmitter that is reflected by an obstacle in front, and a transmission beam that is transmitted from the transmitter. And an analyzing unit that analyzes information about an obstacle ahead based on a reflected beam received by a receiver, wherein at least one of the transmitter and the receiver has a predetermined left and right sides. An in-vehicle radar having scanning means for scanning within a range. 2. A scanning period in which the scanning unit scans at least one of the transmitter and the receiver within a predetermined left and right range, and a forward monitoring period in which the transmitter and the receiver are fixed forward. The vehicle-mounted radar according to claim 1, which is repeated at predetermined time intervals. 3. Whether the reflected beam intensity received by the receiver is below a threshold defined as a function of the inter-vehicle distance analyzed by the analyzing means, and the front analyzed by the analyzing means. Further comprises a judging means for judging whether or not the relative speed with respect to the obstacle is in the decreasing process, the judging means judges that the reflected beam intensity is equal to or less than a threshold value, and the relative speed is decreasing process. The in-vehicle radar according to claim 1 or 2, wherein the scanning by the scanning means is started when it is determined that the vehicle-mounted radar.