JP2001183449A - Collision alarm - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a collision alarm, capable of carrying out measurement with high accuracy over the whole measuring range from a short distance to a long distance, by compensating the demerits by the merits of a pulse Doppler measuring system and FMCW measuring system between them having opposite characteristics. SOLUTION: In this collision alarm, a measuring pulse is outputted from an antenna, its reflection wave is received by an antenna, a distance to a forward object and a relative speed are obtained based on the received signal to judge a risk of collision, and an alarm is generated, as needed. The measurement pulse is set to two kinds of FMCW measurement system and pulse Doppler measurement system. When a vehicle runs at a high speed, the pulse Doppler measuring system is selected for the measuring pulse, and when the vehicle runs at a low speed, FMCW measuring system is selected for the measuring pulse, and signal processing is carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a collision warning device which measures the distance from a vehicle ahead or the like by using radio waves having a frequency in a millimeter wave band and issues a warning if necessary so as not to cause a collision.

[0002]

2. Description of the Related Art Conventionally, there are a pulse Doppler system and an FMCW system as this type, and these will be described first. First, a pulse Doppler system (for example, JP-A-4-323583 and JP-A-6-148317) will be schematically described with reference to FIG. When the power is turned on, the pulse Doppler pulse generation instruction circuit 1 sends the pulse
Is instructed to be a compression wave output waveform that is FM-modulated at 100 MHz into a waveform having a carrier wave as a carrier wave. It is not supplied to 5 but is supplied only to the antenna (primary radiator) 4 and is output from the antenna 4 forward. The radio wave emitted forward, when there is a reflector such as a vehicle ahead, is reflected by the reflector, received by the antenna 4, and supplied to the mixing circuit 5 by the circulator 3. In the mixing circuit 5, the reflected wave supplied from the circulator 3 and the waveform corresponding to the emitted radio wave supplied from the pulse generation circuit 2 are mixed, and the waveforms are subtracted. As a result, an extra waveform such as a carrier wave is removed, and only the measurement component related to the reflected object remains, and the component is supplied to the pulse Doppler signal processing circuit 7 via the output unit 6 and is a front reflected object. Then, an inter-vehicle distance to the preceding vehicle is calculated, and when it is determined that the calculated inter-vehicle distance is in the danger area based on the vehicle speed of the own vehicle, an alarm is issued.

Next, the FMCW method (for example, Japanese Patent Application Laid-Open
JP-A-86574, JP-A-10-232281) will be schematically described with reference to FIG. In general, the circuit configuration is basically the same as that of the pulse Doppler system described above, but different points are as follows. The FMCW pulse generation instructing circuit 8 transmits a 10 GHz carrier wave to the pulse generation circuit 9 by 76M.
An instruction is made to obtain an output waveform modulated by a triangular wave of Hz, and based on the instruction, the pulse is supplied from the pulse generation circuit 2 to the antenna 4 via the circulator 3, and is output from the antenna 4 forward. The radio waves emitted forward are
If there is a reflector such as a vehicle ahead, it is reflected by the reflector, received by the antenna 4, and supplied to the mixing circuit 5 by the circulator 3. In the mixing circuit 5,
The reflected wave supplied from the circulator 3 and the waveform corresponding to the emitted radio wave supplied from the pulse generation circuit 9 are mixed and supplied to the FMCW signal processing circuit 10 via the output unit 6. Similarly, the inter-vehicle distance to the preceding vehicle is calculated, and an alarm is issued when the calculated inter-vehicle distance is determined to be in the danger area based on the vehicle speed of the own vehicle.

[0004]

However, in the above-mentioned pulse Doppler measurement method, there is no problem except when the measurement distance is a short distance, but there is a large error in the measurement of the short distance. There was a feature on the measurement principle that it became. On the contrary, the FMCW measurement method has a contradictory feature that a large error is generated in a long-distance measurement, and that a measurement at a short distance can be performed with higher accuracy.

Therefore, the present invention has been made in view of the above-mentioned features, and complements each other's weak points between the pulse Doppler measurement method and the FMCW measurement method, which have contradictory features, with the advantages of each other, and as a whole, An object is to enable accurate measurement over a measurement range from a short distance to a long distance.

[0006]

According to the invention of this collision warning device, a measuring pulse is output as a radio wave from a primary radiator, and a reflected wave of the radio wave from a target ahead of the primary radiator is received by the primary radiator. A collision warning device that obtains a distance and a relative speed to the front target based on the received signal, determines a danger of a collision, and generates an alarm if necessary, wherein the measurement pulse is of an FMCW measurement type. And the pulse Doppler measurement method, and the measurement pulse is measured by the pulse Doppler measurement method when the vehicle is running at high speed, and by the FMPC measurement when the vehicle is running at low speed. This is a collision warning device characterized by selecting a system and performing signal processing.

[0007]

Embodiments of the present invention will be described below. Embodiment 1 FIG. Embodiment 1 FIG. Will be described with reference to FIG. In the figure, the same or equivalent components as those already described in FIG. 6 are denoted by the same reference numerals, and detailed description thereof will be omitted. Different parts, that is, the pulse generation circuit 14, the vehicle speed sensor 11, The circuit 12 and the changeover switch 13 will be described below.

When the pulse generating circuit 14 is switched to receive the support from the pulse Doppler pulse generation instructing circuit 1 based on a switching signal from a switching circuit 12 described later, a pulse Doppler pulse generating instruction is issued. Based on the output from the circuit 1, an output waveform is formed so as to be a compression wave that is FM-modulated at 100 MHz into a waveform having a carrier wave of 76 GHz. When the pulse generation circuit 14 is switched to receive the support from the FMCW pulse generation instructing circuit 8 based on a switching signal from a switching circuit 12 described later, a 10 GHz carrier wave is transmitted to the pulse generation circuit 14. Is formed into an output waveform modulated by a triangular wave of 76 MHz and output.

The switching circuit 12 receives a vehicle speed signal from the vehicle speed sensor 12 and, when the detected vehicle speed becomes higher than a predetermined vehicle speed, sends an FMCW signal to the pulse generation circuit 14.
The pulse generation instruction circuit 8 is switched so as to operate, and the changeover switch 13 is switched so that the output from the output unit 6 is supplied to the signal processing circuit 10 for FMCW.

The switching circuit 12 switches the pulse generation circuit 14 and the changeover switch 13 so that the pulse Doppler pulse generation instruction circuit 1 operates when the vehicle speed becomes lower than the predetermined vehicle speed.
3 is switched so that the output from the output unit 6 is supplied to the pulse Doppler signal processing circuit 7.

[0011]

As described above, according to the present invention, it is possible to generate an alarm over a range from a short distance to a long distance with a simple configuration.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a circuit block according to a first embodiment of the present invention.

FIG. 2 is a circuit block diagram of a collision warning device using a conventional pulse Doppler system.

FIG. 3 is a circuit block diagram of a collision warning device using a conventional FMCW method.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 pulse generation instruction circuit for pulse Doppler 2 pulse generation circuit 3 circulator 4 antenna 5 mixing circuit 6 output unit 7 signal processing circuit for pulse Doppler 8 pulse generation instruction circuit for FMCW 9 pulse generation circuit 10 signal processing circuit for FMCW 11 vehicle speed sensor 12 Switching circuit 13 Changeover switch 14 Pulse generation circuit

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Claims (1)

[Claims] 1. A measurement pulse is output as a radio wave from a primary radiator, and a reflected wave of the radio wave from a forward target is received by the primary radiator, and a distance to the forward target is determined based on a received signal. And the relative velocity, determine the danger of collision, and generate an alarm as necessary. In the collision alarm device, the measurement pulse is of two types: FMCW measurement type and pulse Doppler measurement type. And, when the own vehicle is traveling at high speed, the pulse Doppler measurement method is selected, and when the vehicle is traveling at low speed, the FMCW measurement method is selected and signal processing is performed. And collision warning device.