JPH08254577A - Collision alarm device for vehicles - Google Patents

Abstract

PURPOSE: To assure minimum safe distance between vehicles and extend life of luminous element by prolonging the illumination interval of the luminous element in accordance with the lowering of speed of the car concerned. CONSTITUTION: An operation circuit 41 sends a distance detection command signal to a drive signal generation circuit 11, takes in a distance signal R to a preceding car from a counter 20 and a car velocity signal Vf of the present car from a car velocity sensor 31, and calculates the relative velocity (d/dt)R between the preceding car and the present car and the velocity Va of the preceding car. Then, the difference in stop distances VF<2> /2α, Va<2> /2α (where α is deceleration performance) between the preceding car and the present car is calculated and the collision is prenoticed based on the distance by adding set 42 free running distance Vf.Td (is the time to brake) of the car concerned. Altogether, when the preceding car is stop (Va=0) and Vf.Td+Vf<2> /2α>=R, when the preceding car is running and (d/dt)R >= predetermined speed C, and when (d/dt)R<C and Vf.Td>=R, alarm 52 functions. At this moment, the circuit 41 takes in the speed signal Vf and direct the circuit 11 to prolong the illumination interval of luminous elements LD-L, LD-C, LD-R in accordance with the lowering of the speed Vf.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle collision warning device for detecting a front target such as an obstacle in front of a vehicle to prevent a collision accident from occurring.

[0002]

2. Description of the Related Art As a conventional vehicle collision warning device, for example, there is one shown in FIG. 3 (Japanese Patent Laid-Open No. 6-30).
8238). In the figure, 1 is a distance detection unit that detects a distance between a vehicle and an obstacle using a laser beam (light beam) emitted from a laser diode (hereinafter, LD), and 2 is a vehicle speed. Is a traveling state detection unit that detects the traveling state of the host vehicle.

Reference numeral 3 issues a distance detection command to the distance detection unit 1, and based on the distance information returned in response thereto and the own vehicle speed detected by the traveling state detection unit 2, the own vehicle, By calculating the relative speed with the obstacle such as the vehicle in front and judging whether the obstacle is a stationary object or a moving object, the own vehicle speed, the relative speed,
The signal processing unit determines the possibility of collision between the host vehicle and an obstacle according to a distance setting or the like set according to individual differences in free running time until the driver brakes.

4 is based on the information from the signal processing unit 3,
This is an alarm notification unit that displays the distance between the host vehicle and the obstacle and issues an alarm when the signal processing unit 3 determines that there is a possibility of collision with the obstacle.

Next, the operation will be described. The traveling state detection unit 2 includes a vehicle speed sensor 31, and the signal processing unit 3 includes an arithmetic circuit 41 and a distance setting switch 42. Vehicle speed sensor 3
The vehicle speed signal of the host vehicle detected in 1 is sent to the arithmetic circuit 41. When the vehicle speed calculated based on the vehicle speed signal is 35 Km / h or more, the arithmetic circuit 41 sends the distance detection command signal to the distance detection unit 1. Is sent.

In the distance detecting section 1, a signal corresponding to the distance detection command signal is sent from the arithmetic circuit 41 to the drive signal generating circuit 11
The drive signal generating circuit 11 receives the L signal shown in FIG.
The D emission signal is sent to the LD switching driver 12. The LD switching driver 12 sends out the signals shown in FIGS. 4 (b), (c), and (d) based on the received LD light emission signal (a), and the LD-L of the LD array 13 as the light emitting means, LD
-C and LD-R are made to sequentially emit light with the same intensity at all times.

The laser beam from the LD-L of the LD array 13 is directed to the front left of the vehicle, the laser beam from the LD-C is directed to the front, and the laser beam from the LD-R is directed to the front right by the light projecting lens 14. Is emitted through LD-
The laser beam of C is used to detect an obstacle ahead, the laser beam of LD-L is used to detect an interrupting vehicle from the left lane, and the laser beam of LD-R is used to detect an interrupting vehicle from the right lane.

The reflected light from the obstacle is condensed by the light receiving lens 15 and is received by the photodiode (hereinafter referred to as PD) 16. This received light signal is sent to the amplifier circuit 17, which amplifies it and outputs the signal of FIG. 4 (e). In this signal, a reflection signal B from an obstacle and a reflection signal A from a short distance road surface are mixed.

The threshold value generation circuit 18 generates a threshold value signal shown in FIG. 4 (f) based on the LD light emission signal (a) output from the drive signal generation circuit 11, and the comparator 19
Output to. The comparator 19 compares the level of the output signal (e) of the amplifier circuit 17 with this threshold signal (f) to extract only the reflected signal from the obstacle, which is shown in FIG. 4 (g). Outputs an obstacle detection pulse signal.

As shown in FIG. 4 (h), the counter 20 outputs the reference pulse generating circuit 2 when the LD light emission signal (a) rises.
Start counting the clock pulse signal supplied from 1 and stop counting at the rising edge of the obstacle detection pulse signal (g) based on the reflection signal from the obstacle, from the count-up time and light speed to the obstacle The distance information of
It is sent to the arithmetic circuit 41 of the signal processing unit 3.

Next, a method of determining the possibility of collision in the arithmetic circuit 41 of the signal processing unit 3 will be described with reference to the flowchart shown in FIG. First, when the power is turned on,
Proceeding to the START step, C constituting the arithmetic circuit 41
Initialization of PU, RAM, etc. is performed. Next, in step ST11, a pulse having a predetermined pulse width is output to the drive signal generation circuit 11 in a predetermined cycle, and the next step ST1
2, a distance signal indicating information on the distance R to the obstacle from the counter 20 of the distance detecting unit 1 and a vehicle speed signal indicating information on the own vehicle speed Vf from the vehicle speed sensor 31 of the running state detecting unit 2 at predetermined intervals. It is taken into the arithmetic circuit 41.

Then, in step ST13, the distance signal R is converted into a display signal and sent to the distance display 51 for display.
Next, in step ST14, the inter-vehicle distance R is differentiated to determine the relative speed (d / dt) R between the obstacle such as the preceding vehicle and the host vehicle.
Is calculated using a calculation method such as the least squares method, and the vehicle speed Va of the preceding vehicle is relative to the own vehicle speed Vf (d / dt).
It is calculated by the sum with R.

In this calculation, (d / dt) R <0
In the case of (d / dt) R> 0, the distance is decreasing, and the distance is decreasing, and (d / dt) R = 0. In the case of, it shows that there is no change in the distance.

In determining the possibility of collision with an obstacle, the initial speed of the host vehicle is Vf (m / s), the initial speed of the obstacle (preceding vehicle) is Va (m / s), and both decelerations. The performance is α (m /
s ² ), the distance setting switch 4 is added to the difference between the stop distance Vf ² / 2α of the own vehicle and the stop distance Va ² / 2α of the preceding vehicle.
The distance R shown in Formula 1 to which the free running distance Vf · Td according to the time Td until the own vehicle brakes set in 2 is added
Is the criterion for collision judgment.

[0015]

[Equation 1]

Therefore, first, in step ST15, the relative speed (d / dt) R and the vehicle speed Vf are compared, and-(d /
dt) When R≈Vf, that is, when the obstacle is regarded as a road stop, the process proceeds to step ST16, and since Va = 0 in the mathematical formula 1, the risk of collision is calculated according to the driving law of the following mathematical formula 2. To judge.

[0017]

[Equation 2]

When Equation 2 is satisfied, there is a danger of collision with an obstacle, and the process proceeds to step ST19 to generate an alarm signal and send it to the alarm notification unit 4, and the alarm device 52 outputs the danger. A warning for avoidance is issued.

On the other hand, as a result of the judgment in step ST15,
When − (d / dt) R≈Vf is not true, the obstacle is a preceding vehicle traveling on the road ahead, and the danger judgment should be originally made according to Equation 1. However, the relative velocity (d /
Since the calculation error of dt) R may not be strict, the calculation error may give an erroneous alarm. Therefore, in the case of a preceding vehicle with an obstacle moving, the relative speed (d / d
t) First, it is determined whether R is equal to or higher than a predetermined speed C (m / sec).

As a result, when (d / dt) R ≧ C, the relative speed is fast and the vehicle is approaching rapidly. Therefore, the preceding vehicle is considered to be infinitely close to the stopped object, and the process proceeds to step ST16, With the same logic as the stop obstacle, the warning output judgment is performed by the discriminant of the mathematical expression 2.

Further, the determination result of step ST17 is (d
/ Dt) R <C, the relative speed is slow and it is considered that the vehicle is normally following the vehicle at a constant inter-vehicle distance.
Since the traveling vehicle speed Va is substantially the same, the mathematical formula 1 becomes a mathematical formula 3 shown below. In step ST18, the risk of collision is determined by this mathematical formula 3. Similarly, when the mathematical formula 3 is satisfied, in step ST19. Give an alarm.

[0022]

[Formula 3] Vf · Td ≧ R

[0023]

However, in such a conventional vehicle collision warning device, in order to reliably operate even when traveling in the rain or fog,
The light transmission output of the LD was set to the maximum or in the vicinity thereof regardless of the own vehicle speed. Therefore, there is a problem that the life of the LD is shortened.

It is an object of the present invention to provide a vehicle collision warning device capable of extending the life of the light emitting element.

[0025]

SUMMARY OF THE INVENTION In a vehicle collision warning device of the present invention, a light emitting element which intermittently emits a light beam toward a front target object through a light projecting lens, and the front target object are reflected. From the light receiving element that receives the light beam, and the light reception output from the light receiving element, calculate the speed of the own vehicle with respect to the front target and the inter-vehicle distance to the front target, and determine the risk of collision of the own vehicle based on that However, in a vehicle collision warning device including an information processing circuit that issues an alarm signal when it is determined that there is a risk of collision, the light emission interval of the light emitting element is increased as the vehicle speed decreases. To do.

[0026]

When the vehicle speed is low, the relative distance change (d /
Since dt) R is also small, the collision prediction accuracy is sufficiently high even if the light emission interval (interval distance sampling interval) is lengthened. By thus increasing the light emission interval, the life of the light emitting element is extended.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a flow chart showing the control contents of a vehicle collision warning device according to an embodiment, which corresponds to FIG. 5 of a conventional example. The hardware configuration of this vehicle collision warning device is the same as that shown in FIG.

In this embodiment, steps ST12 and ST
ST12a is added between 13 and. In this step 12a, the light emission intervals of LD-L, LD-C, and LD-R are made longer as the read vehicle speed Vf becomes smaller. That is, the ROM of the arithmetic circuit 41 stores a map corresponding to the relationship between the vehicle speed and the light emission interval shown in FIG. 2, and the light emission interval corresponding to the read Vf is shown in FIG. 4 (a). The LD light emission signal is output. Depending on this signal, LD-L, LD-C, and LD-R are shown in FIG.
Light is emitted as shown in (d), and thereafter collision prediction is performed in the same manner as in FIG.

Although the light emission interval is linearly lengthened in accordance with the decrease in vehicle speed in FIG. 2, it may be changed stepwise. Further, the light emission interval may be a constant long cycle when the vehicle speed is lower than the predetermined speed, and the light emission interval may be a constant short cycle when the vehicle speed is higher than the predetermined speed.

[0030]

According to the present invention, it is possible to prolong the life of the light emitting device while sufficiently ensuring the minimum safe inter-vehicle distance.

[Brief description of drawings]

FIG. 1 is a flowchart of a vehicle collision warning device according to an embodiment of the present invention.

FIG. 2 is a graph showing a vehicle speed and a light emission interval in the example.

FIG. 3 is a block diagram showing a conventional vehicle collision warning device.

FIG. 4 is a timing chart of a conventional vehicle collision warning device.

FIG. 5 is a flowchart of a conventional vehicle collision warning device.

[Explanation of symbols]

 1 Distance Detection Section 2 Running State Detection Section 3 Signal Processing Section 4 Alarm Notification Section 13 LD Array 14 Light Emitting Lens 15 Light Receiving Lens 16 Photodiode 17 Amplifying Circuit 41 Operation Circuit

Claims (1)

[Claims] 1. A light emitting element which intermittently emits a light beam toward a front target object through a light projecting lens, a light receiving element which receives the light beam reflected by the front target object, and a light receiving element from the light receiving element. When the speed of the own vehicle with respect to the front target and the distance between the front target and the front target are calculated from the received light output, and the risk of collision of the own vehicle is determined based on the calculated distance, and it is determined that there is a risk of collision. In a vehicle collision warning device including an information processing circuit for issuing an alarm signal to a vehicle, the vehicle collision warning device is characterized in that the light emission interval of the light emitting element is made longer as the vehicle speed becomes lower.