JPH0589400A - Obstacle detecting device - Google Patents

Abstract

PURPOSE:To inform a driver of whether a device is operated in a practical performance level or not by preparing plural kinds of thresholds for executing comparison with reflected light so as to judge the presence or absence of an obstacle and providing a changeover means for changing-over the thresholds in order. CONSTITUTION:A threshold generating circuit 22 generates a threshold signal by the constant voltage of a low level and high level in addition to the conventional threshold signal inside a distance detecting part 1. A threshold changeover circuit 23 is provided as the changeover means for controlling the selection and changeover of the three kinds of threshold signals which are outputted from the threshold generating circuit 22. An alarm informing part 4 is provided with a visibility display equipment 53 which informs the driver of whether an obstacle detecting device is in an NG state, in the caution state or in the OK state. Then, the threshold signals which are selected and changed-over in turn are compared with the waveform of reflected light so that visibility is judged by estimating the quantity of rain drops or fog from the waveform of reflected light of a laser beam by the rain drops or fog.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art As a conventional obstacle detecting device, there is one shown in FIG. 4, 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, 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.

A reference numeral 3 designates 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 information detected by the traveling state detection unit 2, causes an obstacle to the own vehicle. Calculate the relative speed with the object to judge whether the obstacle is a stop or a moving object, and set according to the individual speed, relative speed, and individual differences in free running time until the driver brakes. This is a signal processing unit that determines the possibility of a collision between the host vehicle and an obstacle according to the distance setting or the like.

4 is based on the information from the signal processing unit 3,
The alarm notification unit 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 receives the LD light emission signal shown in FIG.
To send to. The LD switching driver 12 receives the LD
5 (b), (c), based on the light emission signal (a),
The signal shown in (d) is transmitted, and the LD-L, LD-C, and LD-R of the LD array 13 serving as the light emitting means are sequentially caused to emit light.

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 collected by the light receiving lens 15 and 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. 5 (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 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. The object detection pulse signal is output.

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, and stops the 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 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 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 V _f from the vehicle speed sensor 31 of the traveling state detecting unit 2 at predetermined intervals. Are taken into the arithmetic circuit 41.

Then, in step ST12, the distance signal R is converted into a display signal and sent to the distance display 51 for display.
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 the 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 increasing, 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 /
When s ²⁾ that, to the difference between the preceding vehicle stopping distance V _a ² / 2α and vehicle stopping distance V _f ² / 2α, distance setting switch 42 time to follow a vehicle brake that is set by the T _The distance R shown in the equation 1, which is the _sum of the free running distance V _f · T _{d due} to _d , serves as a criterion for collision determination.

[0015]

[Equation 1]

Therefore, first, in step ST14, the relative speed (d / dt) R is compared with the vehicle speed V _f , 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 the 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 the danger. A warning for avoidance is issued.

On the other hand, as a result of the judgment in step ST14,
If − (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 made in accordance with 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 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 collision is determined by the equation 3, and if the equation 3 is satisfied, an alarm is issued. Emit.

[0022]

[Equation 3]

[0023]

However, in such a conventional obstacle detecting device, the obstacle is detected by comparing the reflected light with one kind of threshold value. In case of heavy rain or heavy fog, the laser beam is scattered or attenuated by raindrops or fog particles in the air and does not reach the specified distance. As a result, there is a problem that the danger warning is delayed and, for the driver who relies on this danger warning, it becomes extremely dangerous.

The present invention has been made by paying attention to such a problem, and the reflected light is compared with a plurality of kinds of threshold values to detect the visibility, and the device in use has a normal practical performance level. Whether it is operating or causing performance deterioration due to fog,
The purpose is to solve the above problems by informing the driver of whether it is not practical.

[0025]

An obstacle detection apparatus according to the present invention prepares a plurality of threshold values for judging the presence or absence of an obstacle by comparing the reflected light, and the threshold values are sequentially set. Switching means for switching is provided.

[0026]

The switching means according to the present invention sequentially switches a plurality of types of prepared threshold values and compares them with the waveform of the reflected light. From the shape of the waveform of the reflected light due to the raindrops of the laser beam or the fog particles, raindrops in the air and An obstacle detection device that can inform the driver whether the device in use is operating at the practical performance level or the performance is decreasing by estimating the amount of fog particles and determining the visibility To be realized.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing an embodiment of the present invention. First, the configuration will be described. Here, reference numerals 1 to 4 and 11 to 17, 1
9 to 21, 31, 41, 42, 51 and 52 are the same as those in the conventional example of FIG.

Further, unlike the conventional threshold value generating circuit 18, the threshold value generating circuit 22 in the distance detecting section 1 has a low level V ₁ and a high level V _{1 in addition} to the conventional threshold value signal.
_It also generates a threshold signal with a constant voltage of ₂ .

In the distance detecting section 1, there is further provided a threshold switching circuit 23 as switching means for controlling selection / switching of the three types of threshold signals output from the threshold generating circuit 22. ing.

Further, the alarm notifying unit 4 notifies the driver whether the obstacle detecting device is in the energy (NG) state, the caution (CA) state, or the OK (OK) state. A visibility indicator 53 is provided.

Next, the operation will be described. In the obstacle detection device of the present invention, the LD-L, LD-C, and LD-R of the LD array 13 are controlled by the amount of raindrops and the amount of fog particles in the air that affect visibility.
Before the laser beam emitted from the laser beam reaches the obstacle such as the preceding vehicle which is the target, it is reflected by raindrops or fog particles in the air, and the raindrops or fog in the air is reflected based on the shape of the received light waveform received by the PD 16. The amount of grains is estimated and the visibility is determined.

To this end, the threshold value generating circuit 22 is shown in FIG.
In addition to the conventional threshold value shown in (f), two kinds of threshold value signals are generated and sent to the comparator 19.
FIG. 2 shows the configurations of the threshold value generating circuit 22 and the threshold value switching circuit 23.

That is, the threshold value generating circuit 22 is a threshold value signal generated by a time constant circuit composed of a resistor R and a capacitor C,
The threshold signal generated by the battery V ₁ and the threshold signal generated by the battery V ₂ are selected / switched by opening / closing the switches SW _{1 to} SW ₃ and sent to the comparator 19.

At this time, the threshold switching circuit 23 outputs the LD light emission signal (a) output from the drive signal generating circuit 11 to 3
Counted by the bit counter, shifts the contents of the shift register in the shift pulse outputted every time becomes the count value is "3", the switch SW ₁ of the threshold generator circuit 22 to S
Drive signals are sent to W ₃ in order.

Now, assuming that only the drive signal given to the switch SW ₁ is at high level, the drive signals given to the other switches SW ₂ and SW ₃ are at low level, and only the switch SW ₁ is turned on. As a result, in the section (I) of the timing chart shown in FIG. 3, the threshold signal similar to the conventional one is output, and the comparator compares the threshold signal with the output signal (e) of the amplifier circuit 17 to detect an obstacle. Get the distance to.

As described above, the state of the shift register of the threshold value switching circuit 23 is kept at 3 by the 3-bit counter until the pulse of the LD light emission signal (a) reaches 3 times.
From the 4th pulse to the 6th pulse ((II) in Fig. 3)
In the section), only the drive signal to the switch SW ₂ is at the high level, and the rest are at the low level. Therefore, only the switch SW ₂ is turned on, and the threshold value generating circuit 22 outputs a threshold value signal having a constant level of V ₁ .

As a result, the distance (T _2L , T _2C , T _2R ) to the nearby reflector is detected regardless of the presence of the obstacle ahead. This distance becomes the distance to the road surface reflecting portion when the visibility is good according to the visibility, and when the visibility is poor, a distance shorter than the distance to the road reflecting portion is detected depending on the badness.

Next, from the 7th time to the 9th time of the LD light emission signal (a) (section (III) in FIG. 3), only the switch SW ₃ is turned on, and the threshold generation circuit 22 outputs the V
A threshold signal of V ₂ constant level higher than ₁ level is output. The received light signal larger than the V ₂ level does not reflect from the nearby road surface or a distant obstacle, and the output of the comparator 19 becomes the high level only when the visibility is poor due to the thick fog or rain in the vicinity. Distance to rain (T _3L , T
_3C , T _3R ) is measured.

Each distance data (T _1L , T _1C , T _1R , T _2L , T _2C , T _2R , T _3L , T _3C , measured by the counter 20)
T _3R ) is sent to the arithmetic circuit 41, and when the condition shown in Formula 4 is satisfied, the NG indicator of the visibility indicator 53 is turned on to inform the driver that the obstacle detection device cannot operate normally. I encourage you to be careful when driving.

[0040]

[Equation 4]

If any one of T _3L , T _3C , and T _{3R in} the equation 4 has ∞ data, it is regarded as reflection from a nearby obstacle, not due to fog, and the NG indicator is not turned on. ..

Next, when the above equation 4 is not satisfied and the following equation 5 is satisfied, the CA indicator of the visibility indicator 53 is turned on, and the detection performance of the fault detecting device is lowered from the normal state. The driver is advised that the vehicle may not operate normally and the driver should pay attention to driving.

[0043]

[Equation 5]

Here, T _u is the distance from the road surface to the reflecting portion, and is always the expression 6 when the visibility is good.

[0045]

[Equation 6]

Similarly, if any one of T _2L , T _2C , and T _2R measures a distance equal to T _c , it is regarded as reflection from a nearby obstacle and CA lighting is not performed. Then, when this expression 6 is satisfied, it is determined that the visibility is good, and the OK indicator of the visibility indicator 53 is turned on.

[0047]

As described above, according to the present invention, the structure emits a light beam forward from the light emitting means, and based on the reflected light, whether or not there is an obstacle ahead. If it is determined that there is an obstacle, in an obstacle detection device that outputs a detection signal, when determining the presence or absence of the obstacle, prepare a plurality of thresholds to be compared with the reflected light. Since the switching means for sequentially switching the plurality of types of threshold values is provided, when the detection performance of the obstacle detection device is deteriorated by heavy rain or heavy fog, the CA indicator and the NG indicator are turned on according to the degree. Then, by notifying the driver, "The device will notify you even if you can not see the obstacle,"
The effect that the driver's overconfidence in the device can be prevented is obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing an obstacle detection device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram showing details of a threshold value generation circuit and a threshold value switching circuit of the above embodiment.

FIG. 3 is a timing diagram showing a time relationship of signals of respective parts in the distance detection unit of the above embodiment.

FIG. 4 is a block diagram showing a conventional obstacle detection device.

FIG. 5 is a timing chart showing a time relationship of signals of respective parts in the distance detecting part.

FIG. 6 is a flowchart showing a flow of processing in the arithmetic circuit.

[Explanation of symbols]

 13 light emitting means (LD array) 19 comparator 22 threshold value generating circuit 23 switching means (threshold value switching circuit) 53 visibility indicator

Claims (1)

[Claims] 1. A light beam is emitted forward from a light emitting means, and it is determined whether or not there is an obstacle ahead based on the reflected light, and when it is determined that there is an obstacle, a detection signal is output. In an obstacle detection device that outputs, a plurality of threshold values to be compared with the reflected light when determining the presence or absence of the obstacle are prepared, and switching means for sequentially switching the plurality of types of threshold values is provided. An obstacle detection device characterized in that