JPH0587920A - Preventing apparatus for rear-end collision of vehicle - Google Patents

Abstract

(57) [Abstract] [Purpose] A highly reliable rear-end collision prevention device is obtained by using a coded modulation radar device capable of obtaining highly accurate distance information. A clock circuit for generating a clock signal whose pulse width corresponds to the maximum detection distance, a coded pulse generator for generating a coded pulse based on the clock signal, and a transmission signal transmitted based on the coded pulse signal And a coded modulation radar device (inter-vehicle distance measuring device) 1 including a correlator that measures a correlation value between a received signal from a reflector and a calculator that calculates a distance corresponding to the correlator, and various types of vehicle speed sensors and the like. An information processing device 3 that calculates the possibility of a rear-end collision with an obstacle ahead in the traveling direction based on sensor information, and an alarm device 4 that issues an alarm based on the calculation result of the information processing device 3 are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention transmits a coded electromagnetic wave to an obstacle existing in front of a vehicle, expresses a propagation delay time of a transmission signal and a reception signal by a correlation value, and based on the correlation value. The present invention relates to a rear-end collision prevention device using a coded modulation radar device that measures a distance to an obstacle.

[0002]

2. Description of the Related Art There are two types of conventional rear-end collision prevention devices as safety devices for automobiles which use a pulse echo type radar and a random modulation radar. A pulse-echo radar device compares a high-power pulse emitted from a transmitter with a received pulse reflected from a reflector and measures the distance from the time difference. Further, the random modulation radar device transmits the m-sequence pulse signal, obtains the correlation value between the received signal and the transmitted signal, and measures the distance. The correlation in this case is expressed as the number of matching bits when the code sequences are compared bit by bit, minus the number of unmatching bits.

[0003]

However, the above-mentioned pulse echo type radar apparatus has problems that the cost is high because it requires a high-power transmission device, it is weak against interference, and it is weak against noise. In particular, when a laser is used as the medium, there is a big problem that the measuring distance is greatly reduced due to the influence of rain, fog, smoke, etc., and the function as a rear-end collision prevention device cannot be sufficiently fulfilled.

Further, in the above conventional random modulation radar device, since the pulse width of the m-sequence pulse signal determines the distance measurement resolution, that is, the deviation amount of 1 bit pulse width or less does not appear in the correlation value. Therefore, the distance resolution is low and it is not practical as a rear-end collision prevention device. Therefore, it is conceivable to use a very multi-stage phase shift signal in order to improve the accuracy, but a high-speed clock is required, and the processing for obtaining the correlation takes time, which makes the configuration complicated. was there.

An object of the present invention is to solve the above problem by expressing a deviation amount between pulse widths of one clock as a correlation value, and to use the correlation value and the output from another sensor in a dangerous state. An object of the present invention is to provide a rear-end collision prevention device capable of automatically issuing an alarm when it becomes.

[0006]

According to the present invention, there is provided a clock circuit for generating a clock signal whose pulse width corresponds to the maximum detection distance, and a coded pulse generator for generating a coded pulse based on the clock signal. A transmitter that transmits an electromagnetic wave corresponding to the coded pulse signal, a receiver that receives a reflected signal from a reflector, and a time shift amount of the transmission signal from the transmitter and the reception signal at the receiver are correlated. A coded modulation radar device including a correlator that measures as a value and a calculator that calculates a distance corresponding to the correlation value, distance information from the coded modulation radar device, and other sensor information such as a vehicle speed sensor. And an alarm device that issues an alarm based on the calculation result of the information processing device. And butterflies.

As the coded modulation radar device,
A clock circuit that generates a clock signal whose pulse width corresponds to the maximum detection distance, a coded pulse generator that generates a coded pulse based on the clock signal, and a transmission that transmits an electromagnetic wave corresponding to the coded pulse signal. , A receiver for receiving a reflected signal from a reflector, a phaser for phase-shifting the coded pulse from the coded pulse generator, each phase-shifted signal phase-shifted by the phaser, and the reception A correlator that measures the time shift amount of each received signal as a correlation value and a calculator that calculates a distance based on the correlation value are provided.

[0008]

A clock circuit that generates a clock signal whose pulse width corresponds to the maximum detection distance and a coded pulse generator that generates a coded pulse based on the clock signal are used. The applicant previously applied for a coded modulation radar device that calculates the distance to an obstacle ahead by using a correlator that obtains a time shift amount within the pulse width as a correlation value.
In this coded modulation radar device, as long as the time shift amount between the transmission signal and the reception signal is equal to or less than the pulse width of the clock signal, the distance to the obstacle can be calculated by taking the correlation, As compared with the conventional random modulation radar device described in 1 above, the distance can be measured with extremely high accuracy. In the present invention, the possibility of a rear-end collision with an obstacle ahead in the traveling direction is calculated based on the coded modulation radar device capable of highly accurate distance measurement and other sensor information such as a vehicle speed sensor. That is, the rear-end collision possibility is calculated by knowing the distance information and other information such as the vehicle speed.
A fuzzy calculation method or the like can be used for the calculation of the collision possibility. For example, generally, a vehicle speed of 100
It is said that it is good to have an inter-vehicle distance of 100 m at km / h and 80 m at 80 km / h. Therefore, by inputting inter-vehicle distance information and vehicle speed information to the information processing device, the condition is worse than this condition. It is possible to determine whether or not there is a high possibility of a rear-end collision by determining whether or not there is a possibility of a rear-end collision. Then, when it is dangerous based on the calculation result of the information processing device, the alarm device issues an alarm to the driver.

Further, the above-mentioned coded modulation radar device is provided with a phase shifter for phase shifting the coded pulse in order to improve noise resistance and to prevent interference with other coded modulation radar devices. It is also possible to obtain the amount of time shift between each phase-shifted signal phase-shifted by the device and the received signal as a correlation value.

[0010]

1 is a schematic block diagram of an embodiment of a rear-end collision prevention device of the present invention. Reference numeral 1 is an inter-vehicle distance measuring device composed of a coded modulation radar device. Reference numeral 2 is a sensor means for collecting various sensor information such as a vehicle speed sensor.
3 collects the inter-vehicle distance information obtained by the above-mentioned inter-vehicle distance measuring device 1 and the information from various sensors obtained by the sensor means 2, and can collide with an obstacle ahead in the traveling direction based on the information. This is an information processing device that calculates the sex. Also,
An alarm device 4 generates an alarm based on the calculation result of the information processing device 3.

The coded modulation radar device that constitutes the vehicle distance measuring device 1 has the structure shown in FIG. The clock circuit 10 includes a clock oscillator and other frequency dividers, and generates a clock signal whose pulse width corresponds to the maximum detection distance. The coded pulse generator 11 is composed of a shift register, and generates m-sequence coded pulses based on the clock signal. This encoded pulse is the laser drive circuit 12
The laser oscillator 13 is driven to emit a laser wave forward. The laser wave reflected by the obstacle in front is received by the receiver 14, amplified by the receiving amplifier 15 to an appropriate level, shaped into a waveform, and then sent to the correlator 16. The correlator 16 is a circuit that measures the correlation value of the time shift amount between the transmission signal generated by the coded pulse generator 11, that is, the coded pulse signal and the reception signal received by the receiver 14. The correlation value is sent to the calculation unit 17, where the distance corresponding to the correlation value is calculated.

As the transmission signal, for example, the one shown in FIG. 3 is used. As shown in the figure, one cycle of the m-sequence encoded pulse train is set to T, and the pulse width T _K of the clock signal for generating the pulse train is set to a length corresponding to the maximum detection distance. This T _K here is 1.25 μs,
That is, the length corresponding to the maximum detection distance of 200 m (reciprocating 400 m) is set. When such a transmission signal is used, the distance to the obstacle can be measured by using the pulse width T _K of the clock signal as the maximum distance and obtaining the correlation value with the reception signal having a time shift amount equal to or less than the distance. ..

FIG. 4 shows a method of measuring a correlation value when an obstacle exists 100 m ahead. The m-series coded pulse shown in the figure is composed of 15 bits per cycle by using a 4-bit shift register for the coded pulse generator. As shown in the figure, the correlator 16 creates an inverted signal of the received signal b. Then, after the transmission signal rises, the correlation between the transmission signal a and the reception signal b, that is, the exclusive NOR logic is taken here, and after the transmission signal a falls, the transmission signal a and the reception signal Correlation with the inverted signal c, that is, an exclusive NOR logic is taken. The result is d and e. Then, when d and e are combined, correlation value data of f is obtained. A correlation value can be obtained by integrating this correlation value data for one cycle. Since the correlation value is proportional to the distance, the calculation unit 17 can calculate the distance by knowing the correlation value.

With respect to the coded modulation radar device described above, in order to further improve noise resistance and make it less susceptible to the effects of rain, fog, etc., and to prevent interference with other coded modulation radar devices. Therefore, there is a method of providing a phase shifter that shifts the phase of a transmission signal (coded pulse signal). FIG. 5 shows this configuration. That is, a phase shifter 18 for phase-shifting a transmission signal (encoded pulse signal) transmitted from the coded pulse generator 11 is provided, and a plurality of phase shift signals phase-shifted by the phase shifter 18 and the receiver 14 receive The correlation values of the reflected signals (received signals) thus obtained are obtained by the correlator 16. Then, the distance to the obstacle corresponding to each correlation value is calculated. That is, when the correlator 16 obtains the correlation value between each phase shift signal and the received signal, A to E as shown in FIG. 6 (here, the correlation values between the five phase shift signals and the received signal are obtained). You can get a plot like. Therefore, in this case, a straight line connecting the points A and B and a straight line connecting the points C, D and E are drawn, and q of the intersection of the two straight lines is drawn.
A point is obtained, and a value on the X axis with a perpendicular line drawn from this position is obtained. This value is the distance to the front reflector (obstacle). According to such a method, there is an advantage that it is strong against noise and also strong against interference from other coded modulation radar devices. FIG. 7 shows a configuration diagram of the information processing device 3. In this example, in addition to the relative information detection device 20 to which the coded modulation radar device is connected on the input side, a vehicle information detection device 21, a road surface state detection device 22, and a road shape detection device 23 are provided. That is, the sensor means 2 includes a speed sensor, an acceleration sensor, a raindrop sensor, a solar radiation sensor, a stroke sensor, an inclination sensor, a steering angle sensor, a stroke sensor, and the like, and in the vehicle information detection device 21, the speed sensor, the acceleration sensor. The traveling state of the vehicle is detected from the vehicle, the road surface state detecting device 22 detects the road surface state of the road currently traveling, and the road shape detecting device 23 detects the inclination state and the curvature state of the traveling road. To be detected. The output of the above-described coded modulation radar device is connected to the relative information detecting device 20 by detecting the information on the obstacle in front, but is further provided with a camera or the like for detecting the state of the front by an image. In some cases, the front image processing result captured by the camera may be input.

The information group thus detected by the detection devices 20 to 23 is sent to the collision risk inference device 24 corresponding to the information processing device of the present invention. In this example, the collision risk inference device 24 is composed of a fuzzy inference device. The fuzzy knowledge 24a is designed in advance,
It is also possible to update by learning.

By using this knowledge, the inference unit 24b infers the degree of collision risk by receiving the above information.
As a result of the inference, when the dangerous level is reached, the information is sent to the alarm device 4, and the alarm device 4 warns the driver.

In the configuration shown in FIG. 7, the most important information for avoiding a rear-end collision with an obstacle in front is information from the coded modulation radar device. According to the present invention, since the coded modulation radar device can detect the distance information with extremely high performance, the reliability of the rear-end collision prevention system is also very high.

[0018]

Since the coded modulation radar device with extremely high accuracy is used, the reliability of the rear-end collision prevention function can be greatly improved.

[Brief description of drawings]

FIG. 1 shows a schematic configuration diagram of an embodiment of the present invention.

FIG. 2 shows a block diagram of a coded modulation radar device.

FIG. 3 is a diagram showing an example of encoded pulses.

FIG. 4 is a diagram showing a method of measuring a correlation in a correlator.

FIG. 5 is a block diagram showing another example of the coded modulation radar device.

FIG. 6 is a diagram for explaining the operation of the coded modulation radar device shown in FIG.

FIG. 7 is a more detailed block diagram of the rear-end collision prevention device according to the embodiment of the present invention.

[Explanation of symbols]

 1-Vehicle distance measuring device (coded modulation radar device) 2-Sensor means 3-Information processing device 4-Alarm device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shoji Kamata 10 Odoron-cho, Hanazono-cho, Ukyo-ku, Kyoto

Claims (2)

[Claims] 1. A clock circuit for generating a clock signal having a pulse width corresponding to a maximum detection distance, a coded pulse generator for generating a coded pulse based on the clock signal, and a coded pulse signal corresponding to the coded pulse signal. A transmitter that transmits an electromagnetic wave, and a receiver that receives a reflected signal from a reflector,
A coded modulation radar device including a correlator that measures a time shift amount of a transmission signal from the transmitter and a reception signal at the receiver as a correlation value, and a calculator that calculates a distance corresponding to the correlation value. An information processing device that calculates a rear-end collision possibility for an obstacle ahead in the traveling direction based on distance information from the coded modulation radar device and other sensor information such as a vehicle speed sensor; A rear-end collision prevention device, comprising: an alarm device that issues an alarm based on a result. 2. A clock circuit for generating a clock signal having a pulse width corresponding to a maximum detection distance, a coded pulse generator for generating a coded pulse based on the clock signal, and a coded pulse signal corresponding to the coded pulse signal. A transmitter that transmits an electromagnetic wave, and a receiver that receives a reflected signal from a reflector,
A phase shifter for phase shifting the coded pulse from the coded pulse generator, each phase shift signal phase-shifted by the phase shifter, and each time shift amount of the received signal at the receiver as each correlation value. A coded modulation radar device including a correlator to measure and a calculator that calculates a distance based on each correlation value, distance information from the coded modulation radar device, and other sensor information such as a vehicle speed sensor. A rear-end collision prevention device comprising: an information processing device that calculates a rear-end collision possibility for an obstacle in front of the traveling direction based on the above; and an alarm device that issues an alarm based on a calculation result of the information processing device. ..