JPH0853038A - Collision preventing device - Google Patents

Abstract

PURPOSE:To prevent the erroneous measurement due to the reception of the laser beam from an another vehicle by randomly generating the signals for driving a light emission element. CONSTITUTION:When the trigger signals having a constant cycle are supplied from a calculation circuit 41', a random number generating circuit 43 supplies the new trigger signals having a random delay time to a driving signal generating circuit 11, on the basis of the above-described trigger signals. When the laser beam is generated from a light emission element 13 by the output of the driving signal generating circuit 11, and a counter 20 counts the clock supplied from a standard pulse generating circuit 21. When the reflection light supplied from an oncoming vehicle is received by a light receiving element 16, the count by the counter 20 is suspended, and the distance up to the oncoming vehicle is calculated by a calculation circuit 41'. Since the laser beams supplied from the light emission element 13 are sent out at random time intervals, the probability of the erroneous calculation of the distance can be reduced, even if the laser beam emitted from the oncoming vehicle is received.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention, for example, emits a laser beam to the front of the vehicle to measure the distance between the vehicle and the front vehicle and issues an alarm when the vehicle approaches the front vehicle.
The present invention relates to a collision prevention device that prevents a collision with a vehicle ahead.

[0002]

2. Description of the Related Art As a conventional obstacle detecting device, there is one shown in FIG. 3, for example. In the figure, 1 is a distance detection unit that detects a distance between a vehicle and an obstacle by using a laser beam emitted from a laser diode (hereinafter referred to as LD), and 2 is a vehicle such as a vehicle speed. Is a running state detection unit that detects the running state of the vehicle.

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

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, the drive signal generating circuit 11 receives the distance detection command signal, and the drive signal generating circuit 11 sends an LD light emission signal having a constant frequency shown in FIG. The LD switching driver 12 is based on the received LD light emission signal (a), as shown in FIG.
The signals shown in (c) and (d) are transmitted, and the LD-L, LD-C, and LD-R of the LD array 13 as the light emitting means 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. 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 generation circuit 18 is based on the LD light emission signal (a) output from the drive signal generation circuit 11 and is shown in FIG.
The threshold signal shown in FIG.
Output to. The comparator 19 compares the level of the output signal (e) of the amplifier circuit 17 with this threshold value signal (f) to extract only the reflected signal from the obstacle, and the obstacle shown in FIG. Outputs the object detection pulse signal.

The counter 20 has an L level as shown in FIG.
At the rising edge of the D emission signal (a), the reference pulse generation circuit 21
Starts counting the clock pulse signal supplied from, stops counting at the rising edge of the obstacle detection pulse signal (g) based on the reflection signal from the obstacle, and counts from the count-up time and the speed of light to the obstacle. Seeking distance information,
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, S
Proceeding to the TART step, the CP forming the arithmetic circuit 41
U, RAM, etc. are initialized. Next, step S
At T11, a distance signal indicating the information of the distance R to the obstacle from the counter 20 of the distance detecting unit 1 and a vehicle speed signal indicating the information of the own vehicle speed V _f from the vehicle speed sensor 31 of the traveling state detecting unit 2 at a predetermined cycle. Are taken into the arithmetic circuit 41.

Then, in step ST12, the distance signal R is converted into a display signal, which is sent to the distance display 51 and displayed.
Next, in step ST13, 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 a least squares method, and the vehicle speed V _{a of the} preceding vehicle is relative to the own vehicle speed V _f and the relative speed (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 vehicle is V _f (m / s) and the initial speed of the obstacle (preceding vehicle) is V _a (m / s). Deceleration performance is α (m /
s ² ), the difference between the stop distance V _f ² / 2α of the host vehicle and the stop distance V _a ² / 2α of the preceding vehicle is set to the time T until the host vehicle sets the brake by the distance setting switch 42. _The distance R shown in the equation 1, which is the _sum of the free running distance V _f · T _{d due} to _d , becomes the reference for collision judgment.

[0015]

[Equation 1]

Therefore, first, in step ST14, the relative speed (d / dt) R and the vehicle speed _Vf are compared, and-(d /
dt) In the case of R≈V _f , that is, when the obstacle is regarded as a road stop, the process proceeds to step ST15, and since V _a = 0 in Formula 1, the collision law is calculated according to the following formula 2 Determine the risk.

[0017]

[Equation 2]

When the equation 2 is satisfied, there is a risk of collision with an obstacle, and the process proceeds to step ST18 to generate an alarm signal and send it to the alarm notifying unit 4, and the alarm device 52 causes a danger. A warning for avoidance is issued.

On the other hand, as a result of the judgment in step ST14,
When − (d / dt) R≈V _f is not satisfied, 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 accuracy of dt) R may not be strict, the calculation error may give an erroneous alarm. Therefore, in the case of a preceding vehicle in which an obstacle moves, the relative speed (d / d) is calculated in step ST16.
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 regarded as infinitely close to the stopped object, and the process proceeds to step ST15. With the same logic as that of the stop obstacle, the warning output judgment is performed by the discriminant of the equation 2.

Further, the determination result of step ST16 is (d
/ Dt) R <In the case of C, the slow relative speed, regarded as being the normal follow-up running at a constant inter-vehicle distance, vehicle speed V _f
Since the preceding vehicle speed V _a is almost equal, the equation 1 becomes the equation 3 shown below. In step ST17, the danger of a collision is determined by the equation 3, and if the equation 3 is satisfied similarly, in step ST18. Give an alarm.

[0022]

(Equation 3)

[0023]

However, when such a collision prevention device is attached to many vehicles, the probability of encountering a vehicle traveling in the opposite lane from the opposite direction increases, so that The light receiving element of the vehicle device receives the laser beam emitted from the device attached to the vehicle traveling in the opposite lane, and the inter-vehicle distance with the vehicle traveling ahead in the same lane cannot be accurately calculated. ,
There was a problem that the inter-vehicle distance warning could not be issued accurately.

For example, in detail, based on the drive signal of the apparatus of the oncoming vehicle generated at the timing shown by the broken line in the timing chart of FIG.
Consider a case where a laser beam is emitted as indicated by broken lines in (c) and (d), and at the same time, a similar laser beam is emitted from the light emitting element 13 of the vehicle at the same cycle timing.

At this time, if the laser beam emitted from the vehicle traveling in the opposite lane as shown in FIG. 4e is received before the reflected light is received by the light receiving element 16 (see FIG. 4e, a bump-shaped waveform c before each of the waveforms B, indicated by a broken line), a counter 20
Closes the gate at the light receiving timing (at the timing of the rising edge of the pulse shown by the broken line in FIG. 4g), the distance calculation is based on the time from the light emitting timing of the own vehicle to the timing of receiving the laser beam from the oncoming vehicle. There is a problem in that an incorrect distance calculation (FIG. 4i) is performed for the calculation.

The worst pattern occurs when vehicles equipped with devices having the same light emission period face each other, and between the devices detecting each other until the vehicles are considerably close to each other and out of the detection range. It has become possible to continuously calculate an incorrect distance and continue to give an alarm (see FIG. 4i).

The present invention has been made in view of these problems, and an object thereof is to reduce the probability of erroneous distance calculation and improve the reliability of the device.

[0028]

A collision prevention device according to the first aspect of the present invention provides a light emitting element, driving means for driving the light emitting element intermittently and irregularly, and a trigger signal to the driving means. A trigger signal generating means for supplying, a light receiving element for receiving the reflected light emitted from the light emitting element and reflected by a front object, and a distance for calculating a distance to the front object based on a light receiving signal from the light receiving element. It comprises a calculating means and an alarm means for generating an alarm signal when the distance calculated by the distance calculating means exceeds a predetermined value.

In the collision prevention device according to the second aspect of the present invention, the drive signal from the drive means is a random signal.

[0030]

In the collision prevention device according to the present invention, since the drive signal for driving the light emitting element is emitted irregularly (randomly), the laser beam from the device installed in another vehicle traveling in the opposite lane is continuously supplied. You can reduce the probability of receiving,
The reliability of distance calculation can be improved.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be described below with reference to FIG. In FIG. 1, the same components as those described with reference to FIG. 3 or equivalent components are designated by the same reference numerals, and the description thereof will be omitted. Only different components will be described below.

That is, in FIG. 1, 43 is a random number generating circuit (or an irregular signal generating circuit), which is an arithmetic circuit 41 '.
When a trigger signal having a constant frequency is supplied from the device, a new trigger signal having a random delay time based on the trigger signal, that is, a new trigger signal is output after the trigger signal is supplied from the arithmetic circuit 41 ′. The drive signal generating circuit 11 is supplied with a trigger signal which is randomly set with a variable time until it is performed. In addition, the random number generation circuit 43
Is supplied with a reset signal every time the arithmetic circuit 41 'calculates the distance.

Next, the operation of the above configuration will be described with reference to FIG. 2. As can be seen from FIG. 2A, the waveforms shown in FIG. The time axis of is only partially expanded and contracted, and the description is omitted because it is substantially the same.

On the other hand, the time interval at which the drive signal (FIG. 2a) is output, that is, the period T2, is set sufficiently longer than the time T1 from the light reception to the calculation of the distance (FIG. 2). In Fig. 2, the interval between the drive signals (pulses in Fig. 2a) is narrowed for the sake of explanation, but in practice, the pulse period is 1 with respect to the pulse width of the drive signal.
When the laser beam from the vehicle traveling in the opposite lane is mistaken for the actual reflected light and received, the next laser beam is emitted from the own vehicle. Because I do not know, even if the laser beam from the opposite lane direction is received, the counter 20 does not operate,
As a result, incorrect distances are not calculated.

[0035]

As described above, according to the present invention, even if a laser beam from an oncoming lane is received, it is possible to reduce the probability that the distance calculated by the laser beam will be erroneously calculated continuously. The effect is demonstrated.

[Brief description of drawings]

FIG. 1 is a circuit block diagram showing an embodiment of the present invention.

FIG. 2 is a waveform explanatory diagram for explaining the operation of FIG.

FIG. 3 is a circuit block diagram of a conventional device.

FIG. 4 is a waveform explanatory diagram for explaining the circuit of FIG.

5 is a flow chart diagram for performing distance calculation in the arithmetic circuit in FIG.

[Explanation of symbols]

 11 Drive Signal Generating Circuit 13 Light Emitting Element 16 Photosensitive Element 20 Counter 43 Random Number Generating Circuit 41, 41 'Arithmetic Circuit

Claims (2)

[Claims] 1. A light emitting element (13), driving means for driving the light emitting element intermittently and irregularly, trigger signal generating means for supplying a trigger signal to the driving means, and the light emitting element (5). ) And a light receiving element (16) for receiving the reflected light reflected by the front object, distance calculating means for calculating the distance to the front object based on a light reception signal from the light receiving element, and the distance calculation A collision prevention device, comprising: an alarm means for generating an alarm signal when the distance calculated by the means exceeds a predetermined value. 2. The drive signal output from the drive means is a random signal.
Anti-collision device.