JPH05174296A - Inter-vehicle distance detection and alarm device - Google Patents

Abstract

PURPOSE:To prevent an errneous alarm from being issued due to the detection of a guard rail and a vehicle on a neighboring lane on a general road by changing a detection area by a laser beam based on the speed of the vehicle. CONSTITUTION:Inter-vehicle distance between its own vehicle 12 and a preceding vehicle can be found by a laser radar unit 1. When the sum of the braking distance of the preceding vehicle and the intervehicle distance goes less than that of the braking distance of its own vehicle and the free running distance of its own vehicle, an alarm is issued from a buzzer assembled in a display unit 21. The speed of its own vehicle can be found by a vehicle speed sensor 17. A control unit 14 judges the speed of its own vehicle over 60km/h as running on a highway, and sets the detecting areas of laser beams 16a-16c at the speed for running on the highway. Also, when the speed of its own vehicle shows the speed less than 60km/h, the unit judges it as the running on the general road, and the detecting areas by the laser beams 16a-16c are narrowed to the one for running on the general road.

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 for detecting an inter-vehicle distance between an own vehicle and a front vehicle, and issuing an alarm when the distance falls below a certain distance.

[0002]

2. Description of the Related Art The causes of rear-end collisions caused by trucks are mainly
The majority of the drivers are dozing driving and aimless driving.
Under such circumstances, an inter-vehicle distance detection / warning device has now been developed that detects the inter-vehicle distance between the own 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 laser light is emitted forward from the own vehicle, the laser light hits the reflector on the rear surface of the front vehicle and is reflected, and from that time the inter-vehicle distance When the inter-vehicle distance becomes equal to or less than a predetermined distance, the buzzer in the vehicle interior is sounded.

[0003]

However, if the detection area by the laser light is fixed, for example, if the detection area is set so that it can sufficiently function on a highway, the guardrail or the vehicle in the adjacent lane will be set on the general road. It will be detected and a false alarm will occur. In addition, the inter-vehicle distance is displayed without the risk of a rear-end collision at low speed.

[0004]

In order to solve the above-mentioned problems, in the present invention, the time until the laser beam emitted from the own vehicle is reflected by the preceding vehicle and returns is obtained to obtain the inter-vehicle distance,
In the inter-vehicle distance detection / alarm device that issues an alarm when this inter-vehicle distance becomes smaller than the predetermined distance determined based on the braking distance and free running distance of the own vehicle, the laser light based on the speed of the own vehicle is used. It is characterized in that the detection area by is changed.

[0005]

According to the inter-vehicle distance detecting / warning device, since the detection area by the laser light changes based on the speed of the vehicle, that is, the detection area is large at high speed and small at low speed, so at high speed. It provides sufficient detection capability and eliminates the occurrence of false alarms by detecting unnecessary things at low speeds.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a device configuration of an embodiment of an inter-vehicle distance detecting / warning device according to the present invention, and FIG. 2 shows an outline of its mounting position relationship.

A laser radar unit 1 includes a light emitting portion 2 and a light receiving portion 3. The configuration of the laser radar unit 1 is shown in FIG. The light emitting unit 2 in the laser radar unit 1 is composed of a laser diode drive circuit 4, a laser diode 5, and a light emitting lens 6, and emits a laser beam in a pulse shape at regular time intervals. The light receiving unit 3 includes a light receiving lens 7 that receives the laser light reflected by the reflector of the front vehicle, a photodiode 8, an amplifier 9, a signal processor 10, and the like. These light emitting parts 2
From the time difference Δt between the light emission by the light receiving unit 3 and the light receiving by the light receiving unit 3, the distance detection circuit 11 detects the inter-vehicle distance D (= (Δt / 2) ×
Speed of light) is required.

The inter-vehicle distance signal, which is a detection value of the laser radar unit 1, is incorporated in the underside of the seat 13 of the truck 12 and is a control unit 14 as a control system.
Entered in.

The laser radar unit 1 is assembled in the bumper 15 of the 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 provided on the left, center, and right.
It emits a, 16b, and 16c. In the figure,
41 shows a road.

A vehicle speed sensor 17 detects the vehicle speed from the 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 disc 19 provided in the steering column and a light emitting / receiving portion 20 for detecting the slit thereof, and a steering angle signal which is a detection signal thereof is inputted to the control unit 14. There is.

Details of the steering sensor 18 are shown in FIGS. The disk 19 is provided with slits 31 for angle detection at regular intervals, and inside thereof, one slit 32 for neutral position detection is provided with the position shifted from the center between the slits 31. There are two light-emitting / light-receiving parts 20 for detecting the slit 31 (20
a, 20b), one for slit 32 detection (20
c) It is provided. Since the positional relationship between the slits 32 on both sides of the slit 32 is different, clockwise or counterclockwise rotation is detected with respect to the neutral position.

To detect the neutral position, the time when the vehicle speed is 40 km / h or more and the slit 32 is detected is determined to be the neutral position, that is, the steering angle is 0 °. Then, based on this position, the detection amount of the slit 31 is used to detect how many times clockwise or counterclockwise.

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

As the other environment sensor 24, a raindrop sensor, a road surface sensor (G sensor), a temperature sensor, a slip sensor, etc. are equipped. According to the raindrop sensor, it is detected that it is raining, that is, the road surface is wet,
The road surface sensor detects whether the road surface is a turning road or other conditions, and the temperature sensor detects weather and eventually road surface conditions such as a frozen state in combination with the detection results of other sensors. The slip sensor detects whether or not the road surface is likely to slip, that is, whether the road is a low μ road or a high μ road, based on the difference in rotational speed between the front wheels and the rear wheels. The detection result is input to the control unit 14.

Reference numeral 21 denotes a display unit incorporated in the instrument panel in front of the driver's seat, which is provided with a display unit for the inter-vehicle distance, a buzzer for issuing an alarm, a ramp for flashing when an alarm is issued, etc. to call attention to the driver, It also warns you.

Next, the calculation process leading to the alarm generation by the apparatus of this embodiment will be described. Own vehicle 1 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 calculated by a change in the inter-vehicle distance D per minute time. That is, the front vehicle speed Va is obtained from the relative speed between the own vehicle 12 and the front vehicle 22.

On the other hand, the time required for the driver to judge that the driver is in danger before stepping on the brake pedal, that is, the free running time Td (s), the time for the driver to judge that it is dangerous, that is, the judgment time Tx (s) and The vehicle deceleration α ₁ (m / s ² ) and the preceding vehicle deceleration α ₂ (m / s ² ) are stored in advance in the memory of the control unit 14. The decelerations α ₁ and α ₂ are stored as values assuming full braking, and normally α ₁ = α ₂ .

The braking distance L ₁ of the front vehicle 22 can be obtained from the front vehicle speed Va and the deceleration α _{2 according} to L ₁ = Va ² / 2α ₂ .

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

The braking distance L ₃ of the vehicle 12 is determined by the vehicle speed Vf.
And deceleration rate α ₁ , L ₃ = Vf ² / 2α ₁ .

Therefore, as a condition for generating the alarm, the sum of the front vehicle braking distance L ₁ and the inter-vehicle distance D is the automatic braking distance L ₃
And when it becomes smaller than the sum of the vehicle free running 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), the buzzer incorporated in the display unit 21 issues an alarm 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 consideration when calculating s, the front vehicle 2
The optimum alarm time is determined by whether the vehicle 2 is running at high speed or low speed, whether it is accelerating or decelerating, and whether it is stopped. When the front vehicle 22 is stopped, Va = 0 in the equation.

By the way, the vehicle decelerations α ₁ and α ₂ are small on a wet road surface or a frozen road surface in the case of rain.
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 to change the alarm generation inter-vehicle distance. That is, on a wet road surface or the like, the safe inter-vehicle distance Ds automatically changes, and the alarm generation time is advanced.
For example, if the deceleration rate α ₁ (= α ₂ ) on a dry road is about 0.3 G, depending on the road surface condition, 0.2 G (for example, a wet road surface) or 0.1 G (for example, a frozen road or snow) Change the way).

As shown in FIG. 4, the detection capability range of each laser beam 16a, 16b, 16c in the laser radar unit has the same length, but the right and left laser beams 16a, 16c detect the vehicle width or more. Because you don't have to
The detection area is within a certain range as shown in FIG.
The shaded area) is restricted. This is because the detection area by the central laser beam 16b is set to the performance area so that the detection function can be sufficiently exerted when traveling on an expressway, and the detection areas of the laser beams 16a and 16c on both sides thereof are set according to the road width. The laser light length is narrowed to a certain range.

However, as described above, the laser beams 16a,
If the detection areas of 16b and 16c are fixed in this way, a guardrail, a vehicle in an adjacent lane, and a front vehicle that is not likely to be hit by another vehicle will be detected on the general road. Therefore, at a certain vehicle speed, the laser light 16
The area to be detected is changed within the detection capability area of a, 16b, and 16c. For example, when the vehicle speed is 60 km / h or more, it is determined that the vehicle is traveling on an expressway, and the detection areas by the laser beams 16a, 16b, 16c are set as shown in FIG. 8A, and the vehicle speed is 60 km / h. If it is not more than h, it is determined that the vehicle is traveling on an ordinary road, and laser light 1
The detection areas of 6a, 16b and 16c are set as shown in FIG. 8 (B). That is, the laser beams 16a, 1
Anything within the detection capability range of 6b and 16c but outside the detection range is not detected as a front vehicle or the like.
In addition, in FIG. 8A and FIG. 8B, a portion shown in perspective is a detection region. In FIGS. 8A and 8B, distances are also shown as an example for easy understanding. Further, in the figure, 41a indicates an expressway and 41b indicates an ordinary road.

Further, it is necessary to change the detection area depending on the highway or the general road even at the time of turning. This is based on the graph as shown in FIG.
The detection areas of 6a, 16b and 16c are changed. This figure is for the case of turning right.

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

While the truck 12 is traveling, the inter-vehicle distance D is calculated in step (2) based on the above-mentioned calculation formula, and in step (3) the vehicle speed Vf is detected by the vehicle speed sensor 17, and in step (4) ), The front 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 , α _{2 of} the own vehicle and the preceding vehicle are changed according to the road surface condition (step (6)). If environmental information is not detected in the previous step (5), the default decelerations α ₁ and α ₂ are used as they are.

Next, in step (7), the safe inter-vehicle distance Ds is obtained from the vehicle speed Vf, the front vehicle speed Va, the decelerations α ₁ , α _2, etc. detected or calculated as described above. This safe inter-vehicle distance Ds is a value that is appropriately corrected in consideration of the speed of the front vehicle 22 and according to road surface conditions.

On the other hand, the steering angle is detected by the steering sensor 18 (step (8)), and then, in step (9), it is judged whether or not the vehicle speed Vf is 60 km / h or more.

When the vehicle speed Vf is 60 km / h or more, it is determined that the vehicle is traveling on a highway, and it is determined from the steering angle previously obtained whether the vehicle is in a straight traveling state, that is, whether the steering wheel is in the neutral position. (step 1
0)), in the straight traveling state, as shown in FIG. 8A, the detection regions (S) of the laser beams 16a, 16b, 16c are detected.
l, Sc, Sr) are set to those for highway driving (step (11)).

Next, in step (12), it is determined whether the current inter-vehicle distance D is within the safe inter-vehicle distance Ds. If it is within the safe inter-vehicle distance Ds, the process proceeds to step (13), no alarm is issued, and only the inter-vehicle distance is displayed on the display unit 21.

If it is determined in step (12) that the inter-vehicle distance D is smaller than the safe inter-vehicle distance Ds, then step (1)
In 4), the front vehicle speed Va and the own vehicle speed Vf are compared. When the front vehicle speed Va is high, the inter-vehicle distance D is increasing, and therefore it is not necessary to issue an alarm, and the process proceeds to step (13).

When the front vehicle speed Va is smaller than the own vehicle speed Vf, the vehicle is in an area to be warned and is gradually approaching. Therefore, the process proceeds to step (15) to generate an alarm and display unit 2
The inter-vehicle distance is displayed in 1.

When it is judged in the above step (10) that the laser is not neutral, that is, the vehicle is turning, the left, center and right lasers are set as shown in FIG. 12 based on the map shown in FIG. Detection area by the light 16a, 16b, 16c (Sl
, Sc, Sr) are set (step (16)). After this, move to step (12) and follow steps (12) to (15) below.
Is operated.

In step (9) above, when it is determined that the vehicle speed is not 60 km / h or more, it is determined that the vehicle is traveling on an ordinary road, and it is determined from the steering angle obtained earlier whether the vehicle is in a straight traveling state. (Step (17)) If the vehicle is in the straight traveling state, the laser beams 16a and 16a as shown in FIG.
The detection areas (Sl, Sc, Sr) by b and 16c are narrowed to those for traveling on general roads (step (18)). After that, the operations of steps (12) to (15) are performed. Therefore, when traveling on a general road, a guardrail or a vehicle in an adjacent lane is not detected, and frequent alarms can be prevented in a non-dangerous situation.

If it is determined in the above step (17) that the vehicle is not neutral, it means that the vehicle is turning on an ordinary road.
Based on the map as shown in FIG. 5, the detection areas of the left, center, and right laser beams 16a, 16b, 16c are narrowed to those for general roads (Sl, Sc, Sr) (steps).
(19)). After that, the process of comparing and judging in steps (12) to (15) is performed as described above. The above operation is repeated, and an appropriate alarm is issued according to the traveling road.

It should be noted that although the alarm may or may not be issued by comparing the safe inter-vehicle distance Ds and the inter-vehicle distance D as described above, it is also possible to issue this alarm in stages. .. For example, when D <Ds, the buzzer sounds a few times as the primary alarm (caution alarm), and the secondary alarm is D <Td Vf + (Vf ² / 2α
_{It is} assumed that _1- Va ² / 2α ₂ ) = Ds ₁ (warning distance between vehicles), and in this case, the buzzer sounds continuously. In this state, the driver's judgment is not required, and the brake must be immediately applied. If the warning is gradual, the driver can respond quickly.

The present invention is not limited to trucks, but may be buses,
The same applies to passenger cars and the like.

[0042]

According to the inter-vehicle distance detecting / warning device of the present invention, the detection area by the laser beam is changed according to the road, so that the guard rail, the vehicle in the adjacent lane, etc. can be used even when traveling on a general road. No detection is performed, and false alarms and alarms can be prevented from occurring without any danger.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram of a schematic positional relationship of each component.

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

FIG. 4 is a plan view of a laser beam starting state.

FIG. 5 is a perspective view of a steering sensor.

FIG. 6 is an explanatory diagram of steering angle detection.

FIG. 7 is an explanatory diagram of an inter-vehicle distance, a braking distance, and the like.

FIG. 8 is an explanatory diagram showing a state in which a detection area by laser light is changed between an expressway and a general road.

FIG. 9 is a diagram showing a relationship between a road curve radius and an alarm judgment area.

FIG. 10 is a flowchart of an example.

FIG. 11 is a flowchart of an example.

FIG. 12 is an explanatory diagram showing how the alarm determination area is changed in the circuit.

[Explanation of symbols]

 1 laser radar unit 12 own vehicle 14 control unit 16a, 16b, 16c laser light 17 vehicle speed sensor 18 steering sensor 21 display unit 22 front vehicle 24 environment sensor 41a highway 41b general road

Claims (1)

[Claims] 1. A vehicle-to-vehicle distance is obtained by detecting a time until a laser beam emitted from the vehicle is reflected by a vehicle in front and returning, and the vehicle-to-vehicle distance is calculated based on a braking distance and a free running distance of the vehicle. In the inter-vehicle distance detection / alarm device that issues an alarm when the distance becomes smaller than the predetermined distance specified in, the inter-vehicle distance is characterized in that the detection area by laser light is changed based on the speed of the own vehicle. Detection / alarm device.