JP2697442B2 - Inter-vehicle distance detection and alarm device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inter-vehicle distance detecting / warning device which detects the inter-vehicle distance between a host vehicle and a preceding vehicle, and issues an alarm when the distance falls below a predetermined distance.

[0002]

2. Description of the Related Art The causes of rear-end collisions mainly due to trucks are:
Drivers who fall asleep or drunk driving account for the majority.
Under these circumstances, an inter-vehicle distance detection / warning device has been developed which detects the inter-vehicle distance between the host vehicle and the preceding vehicle, and issues an alarm to the driver when the distance falls below a certain distance. ing. The outline of the current state of this device is that the laser beam is emitted forward from the own vehicle, the laser beam is reflected and hits the reflector on the rear surface of the front vehicle, and the laser beam is received. When the inter-vehicle distance becomes equal to or less than a predetermined distance, a buzzer in the vehicle cabin is sounded.

[0003]

However, even if the inter-vehicle distance between the preceding vehicle and the own vehicle is an area in which a warning is to be issued, when the speed difference between the preceding vehicle and the own vehicle is within a certain range, If you are in a so-called following running state, there is little danger,
On the contrary, if a warning is frequently generated in this state, it may be troublesome for the driver and may cause distraction.

[0004]

In order to solve the above-mentioned problems, according to the present invention, a time until a laser beam emitted from the own vehicle is reflected by a preceding vehicle and returns is determined to obtain an inter-vehicle distance.
When the inter-vehicle distance becomes smaller than a predetermined distance determined based on the own vehicle's braking distance or idle running distance, the inter-vehicle distance detection / alarm device which issues a primary alarm and further a secondary alarm, Even if the distance is a distance at which a primary warning should be generated, the primary warning is not generated or only a part is generated when the speed difference between the own vehicle and the preceding vehicle is within a certain range.

[0005]

According to the inter-vehicle distance detecting / warning device having the above-mentioned structure,
In the case of driving following the preceding vehicle while maintaining the primary warning area,
The alarm does not continue to occur.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an apparatus configuration of an embodiment of an inter-vehicle distance detecting / warning apparatus according to the present invention, and FIG.

Reference numeral 1 denotes a laser radar unit having a light emitting unit 2 and a light receiving unit 3. FIG. 3 shows the configuration of the laser radar unit 1. The light emitting section 2 of the laser radar unit 1 includes a laser diode drive circuit 4, a laser diode 5, and a light emitting lens 6, and emits laser light in a pulsed manner at regular intervals. The light receiving section 3 includes a light receiving lens 7, which receives laser light reflected by a reflector of a front vehicle, a photodiode 8, an amplifier 9, a signal processor 10, and the like. These light emitting units 2
The inter-vehicle distance D (= (Δt / 2) ×
Light speed) is required.

An inter-vehicle distance signal, which is a detection value of the laser radar unit 1, is transmitted to a control unit 14 as a control system incorporated below the seat 13 of the truck 12.
Is input to

The laser radar unit 1 is assembled in a bumper 15 of a truck 12 as shown in FIG.
In this embodiment, three light emitting units 2 and three light receiving units 3 are provided,
As shown in FIG. 4, three laser beams 16 are located on the left, center, and right.
a, 16b, and 16c.

Reference numeral 17 denotes a vehicle speed sensor which detects the vehicle speed from a rotating portion of the transmission or the like. The detection signal of the vehicle speed sensor 17 is input to the control unit 14. Reference numeral 18 denotes a steering sensor having a disk 19 provided on a steering column and a light emitting / receiving section 20 for detecting a slit of the disk. A steering angle signal as a detection signal is input to the control unit 14. I have.

Reference numeral 23 denotes a wiper switch that functions as an example of an environment sensor, and its ON and OFF signals are input to the control unit 14. That is, when the wiper switch 23 is turned on, it is determined that it is raining.

The other environmental sensors 24 include a raindrop sensor, a road surface sensor (G sensor), a temperature sensor, a slip sensor, and the like. According to the raindrop sensor, it is detected that it is rainy, that is, the road surface is in a wet state,
The road surface sensor detects whether the road surface is a bumpy road, or other conditions, and the temperature sensor detects the weather and thus the road surface conditions, for example, a frozen state, in combination with the detection results of other sensors. According to the slip sensor, it is detected from the rotational speed difference between the front wheels and the rear wheels whether or not the road surface is likely to slip, that is, whether it is a low μ road or a high μ road. The detection result is input to the control unit 14.

Reference numeral 21 denotes a display unit incorporated in an instrument panel in front of a driver's seat, which is provided with a display unit for an inter-vehicle distance, a buzzer that issues an alarm, a lamp that flashes when an alarm is generated, and the like, to call the driver's attention. It also warns you.

Next, a description will be given of a calculation process leading to the generation of an alarm by the apparatus of the embodiment. As shown in FIG.
The distance between the vehicle 2 and the front vehicle 22, that is, the inter-vehicle distance D (m) is obtained by the laser radar unit 1 as described above.
The vehicle speed Vf (m / s) is detected by the vehicle speed sensor 17. The speed Va (m / s) of the front vehicle 22 is obtained by calculation from a change in the inter-vehicle distance D per minute time. That is, the front vehicle speed Va is determined from the relative speed between the own vehicle 12 and the front vehicle 22.

On the other hand, the time until the driver determines that the vehicle is dangerous and steps on the brake pedal, that is, the idle running time Td (s), the time when the driver determines that the vehicle is dangerous, that is, the determination time Tx (s) and the self-time. The deceleration α ₁ (m / s ² ) of the vehicle and the deceleration α ₂ (m / s ² ) of the preceding vehicle are stored in the memory of the control unit 14 in advance. As the decelerations α ₁ and α ₂ , values assuming full braking are stored, and normally, α ₁ = α ₂ .

The braking distance L ₁ of the front vehicle 22 is determined from the preceding vehicle speed Va and the deceleration α ₂ by L ₁ = Va ² / 2α ₂ .

The idle running distance L ₂ of the own vehicle 12 is determined by the own vehicle speed Vf.
From the idle running time Td and the judgment time Tx, L ₂ = (Td +
Tx) Vf.

The braking distance L ₃ of the own vehicle 12 is equal to the own vehicle speed Vf.
And obtained from the deceleration alpha ₁ Metropolitan by ^{_{L 3 = Vf 2 / 2α 1}} .

Therefore, the condition for generating the alarm is that the sum of the preceding vehicle braking distance L ₁ and the inter-vehicle distance D is equal to the automatic braking distance L _3.
Triggered by the when and becomes smaller than the sum of the vehicle air-run distance L _2. That is, Va ² / 2α ₂ + D <Vf ² / 2α ₁ + (Td + Tx) Vf. Therefore, D <(Td + Tx) Vf + (Vf ² / 2α ₁ −Va ² / 2α ₂ )
= Ds (safe inter-vehicle distance), an alarm is issued from the display unit 21 and the lamp blinks.

As can be seen from this equation, the safe inter-vehicle distance D
Since the speed of the front vehicle 22 is taken into account in the calculation of s, the front vehicle 2
The optimum warning time is determined depending on whether the vehicle 2 is traveling at high speed or low speed, whether the vehicle is accelerating or decelerating, and whether the vehicle is stopped. When the front vehicle 22 is stopped, Va = 0 in the equation.

By the way, the decelerations α ₁ and α ₂ of the vehicle are small on a wet road surface or a frozen road surface in rainy weather.
Therefore, when it is detected that the wiper switch 23 is turned on, the control unit 14 changes the numerical values of the decelerations α ₁ and α ₂ and changes the inter-vehicle distance at which the alarm is generated. That is, on a wet road surface or the like, the safe inter-vehicle distance Ds automatically changes, and the warning issuance time is advanced.
For example, if the deceleration α ₁ (= α ₂ ) on a dry road is about 0.3 G, then 0.2 G (for example, a wet road) or 0.1 G (for example, a frozen road, Road).

When the inter-vehicle distance becomes smaller, it is more effective to warn the driver more strongly. Therefore, when D <Ds described above, a primary alarm area (caution alarm area) is used. The warning sound is generated intermittently and the distance D
Is D <(TαVf + (Vf ² / 2α ₁ −Va ² / 2α ₂ ) =
When it becomes Ds ₁ (warning inter-vehicle distance), it is defined as a secondary warning area (warning warning area), and in this area, a warning sound is generated continuously. In this state, the driver does not need to make a decision, but needs to immediately apply the brake.

However, when the vehicle travels at a fixed distance from the preceding vehicle, that is, when the vehicle travels in a so-called following manner, the vehicle sometimes travels while maintaining the distance in the primary warning area. Regardless, the caution alert will continue to be generated. This is annoying for drivers,
It can distract you from alertness. For this reason, in the present invention, in the following running state, the caution warning is generated only partially or not at all, and the secondary warning is generated as usual.

Whether the vehicle is in the normal running state is determined based on the speed difference between the host vehicle and the preceding vehicle, that is, the relative speed. Also in this case, since the speed difference that can be determined as the following running is different between the general road and the highway, the determination is made in consideration of the speed of the own vehicle as shown in FIG. 6 or FIG. The one shown in FIG. 6 determines whether the vehicle is running on a highway or a general road based on whether or not the vehicle speed is greater than 60 km / h. In the case of (1), it is determined that the vehicle is following the vehicle, and when traveling on a general road, the vehicle is determined to be following the vehicle if the speed increase is 10 km / h or less. FIG. 7 shows an example in which the magnitude of the speed difference is changed according to the own vehicle speed. In addition, the reason that the judgment speed difference is larger for ordinary roads is that
This is because there are many factors that cause speed changes on general roads.

Next, a specific control example by the control unit 14 in the apparatus of this embodiment will be described with reference to the flowchart of FIG. First, an initial value is set in step (1). That is, the idle running time Td and the judgment time T
x, decelerations α ₁ , α ₂ (α ₁ = α ₂ ) at the time of full braking of the own vehicle 12 and the front vehicle 22 are set.

While the truck 12 is running, the inter-vehicle distance D is calculated in step (2) based on the above formula, and in step (3), the vehicle speed Vf is detected by the vehicle speed sensor 17, and the vehicle speed Vf is detected in step (4). In), the preceding vehicle speed Va is obtained from the change in the inter-vehicle distance D and the own vehicle speed Vf as described above.

Next, the environment, that is, the road surface condition is detected by the environment sensor 24 and the like (step (5)). For example, it is detected whether the wiper switch 23 is in the ON state.

Next, the decelerations α ₁ and α _{2 of} the own vehicle and the preceding vehicle are changed according to the road surface condition (step (6)). If the environment information is not detected in the previous step (5), the default decelerations α ₁ and α ₂ are adopted as they are.

Next, in step (7), the vehicle speed Vf detected or calculated as described above, the preceding vehicle speed Va, the deceleration alpha _1, safe distance Ds from the alpha ₂ or the like is required. This safe inter-vehicle distance Ds is appropriately corrected in consideration of the speed of the preceding vehicle 22 and according to the road surface condition.

Next, the current inter-vehicle distance D is the safe inter-vehicle distance D.
It is determined whether it is not less than s (step (8)).
If it is equal to or longer than the safe inter-vehicle distance Ds, the process proceeds to step (9), and it is not necessary to generate an alarm, so that no alarm is generated and only the inter-vehicle distance is displayed on the display unit 21.

In step (8), the current inter-vehicle distance D
Is smaller than the safe inter-vehicle distance Ds, it is then determined whether or not the speed difference between the preceding vehicle 22 and the own vehicle 12 is 0 or more. If it is 0 or more, even if it is in the area to be warned, since it is in the state of being gradually separated, the process proceeds to step (9), and no warning is issued, and only the following distance is displayed.

If the speed difference between the preceding vehicle 22 and the own vehicle 12 is not equal to or greater than 0, it is then determined whether or not the own vehicle speed Vf is equal to or greater than 60 km / h (step (11)). In some cases, it is determined that the vehicle is traveling on a highway, and step (1)
2), for example, based on a map as shown in FIG.
It is determined whether it is greater than h. The speed difference is 5 km /
If h is smaller, that is, if NO is determined in step (12), since the vehicle is in the following running state, the primary warning is not generated and only the following distance is displayed (step (13)). However, even if the vehicle is following, the inter-vehicle distance D is in the warning / alarm area D.
if it becomes s ₁ below, to generate a second alarm to alert the driver that the vehicle distance becomes too small.

If it is determined in step (12) that the speed difference between the preceding vehicle 22 and the own vehicle 12 is equal to or greater than 5 km / h, the vehicle is not following, and the inter-vehicle distance D is equal to the safe inter-vehicle distance D as usual.
to generate primary alarm if it becomes s or less, to generate a secondary alarm when in a warning alarm region Ds ₁ or less (step (14)).

In step (11), the vehicle speed Vf is 60 km /
If it is not greater than h, it is determined that the vehicle is traveling on a general road, and then in step (15), it is determined whether the vehicle is following the general road. This determination is made based on, for example, a map as shown in FIG. 6 based on whether the increase in the speed of the own vehicle 12 with respect to the preceding vehicle 22 is greater than 10 km / h. It is determined that the state is the same, and in the same manner as described above, the primary alarm is not generated in step (13), but only the secondary alarm is generated. Step (15)
If it is determined that the vehicle is not following, the process proceeds to step (14), and a primary alarm and a secondary alarm are generated as usual.

As described above, since the primary alarm is not generated in the following running state, the state where the primary alarm is continuously generated during the following running can be avoided. In the following running state, a secondary alarm is generated immediately. However, since the vehicle is in the following running state, there is no problem in handling the brake operation.

FIG. 9 shows a flowchart of another control example. This is to cause the driver to pay attention by issuing an alarm as a primary alarm only in one cycle as a processing of the following running state in step (13), and other judgment and processing are shown in FIG. Same as the ones.

It should be noted that the determination of the follow-up running may not be based on the set values as shown in FIGS. 6 and 7, but may be determined based on a graph that is further divided into stages. Further, the present invention is not limited to trucks, but can be similarly applied to buses, passenger cars, and the like.

[0038]

According to the inter-vehicle distance detection / warning apparatus of the present invention, no warning is generated or only a predetermined cycle is generated in the primary warning area in the following running state. You won't be bothered. In the primary alarm area, the primary alarm
Whether to generate it or only a predetermined cycle
Than during the high-speed range of the speed difference between the travel of the vehicle in front and the rear car to determine, since the larger the person at the time of low and medium speed running, at the time of large low and medium speed running of the speed change, frequently that the alarm is emitted Without distraction, preventing distraction. In addition, since the secondary alarm is generated as usual in the secondary alarm area, there is no delay in responding to the brake operation.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an apparatus configuration according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a schematic positional relationship between components.

FIG. 3 is an explanatory diagram of a laser radar unit.

FIG. 4 is a plan view showing a state in which a laser beam starts.

FIG. 5 is an explanatory diagram of an inter-vehicle distance, a braking distance, and the like.

FIG. 6 is a graph for determining following running;

FIG. 7 is a graph of another example for determining the following running.

FIG. 8 is a flowchart of one embodiment.

FIG. 9 is a flowchart of another embodiment.

[Explanation of symbols]

 Reference Signs List 1 laser radar unit 12 own vehicle 14 control unit 16a, 16b, 16c laser beam 17 vehicle speed sensor 18 steering sensor 21 display unit 22 front vehicle 23 wiper switch 24 environment sensor

Continuation of front page (56) References JP-A-5-210799 (JP, A) JP-A-4-201643 (JP, A) JP-A-3-260900 (JP, A) JP-A-1-152282 (JP) U.S.A., U.S.A., No. 27, (1990, 6, 25), Nissan Motor, P.S. 157-164 Automotive Technology, Vo43, No. 2, (1989, 2, 1), Japan Society of Automotive Engineers, P.S. 65−73

Claims (1)

(57) [Claims] An inter-vehicle distance is determined by detecting a time until a laser beam emitted from the own vehicle is reflected by a preceding vehicle and returned, and the inter-vehicle distance is determined based on a braking distance and an idle running distance of the own vehicle. In the inter-vehicle distance detection / warning device which issues a primary alarm and further a secondary alarm when the distance becomes smaller than a predetermined distance set in, even if the inter-vehicle distance is a distance at which a primary alarm should be generated, the own vehicle When the speed difference between the vehicle and the preceding vehicle is within a certain range, a primary alarm is not generated or only a predetermined cycle is generated, so that the range of the speed difference is higher than when traveling at high speed.
An inter-vehicle distance detection / warning device characterized by having a larger size at low and medium speeds .