JPH04201643A - Between-vehicle distance detecting alarm device - Google Patents

Abstract

PURPOSE:To normallize the alarm generation timing by calculating the safe between-vehicle distance, in consideration of the preceding vehicle speed, besides the own vehicle speed. CONSTITUTION:The distance D between an own vehicle 12 and a preceding vehicle 22 is obtained by a laser rader unit 1. The own vehicle speed Vf is detected by a car speed sensor. The speed Va of the preceding vehicle 22 is obtained through the calculation from the variation of the between-vehicle distance D per fine time. The brake distance L1 of the preceding vehicle 22 is obtained by L1=Va<2>/2alpha2 from the preceding vehicle speed Va and the deceleration speed alpha2. The idle traveling distance L2 of the own vehicle 12 is obtained by L2=(Td+Tx)Vf from the own vehicle speed Vf, idle traveling time Td, and the judgement time Tx. The brake distance L3 of the own vehicle 12 is obtained by L3=Vf<2>/2alpha1 from the own vehicle speed Vf and the deceleration speed alpha1. Accordingly, the condition of alarm generation is based on the time when the sum of the preceding vehicle brake distance L1 and the between-vehicle distance D becomes smaller than the sum of the own vehicle brake distance L3 and the own vehicle idle traveling distance L2.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention provides an inter-vehicle distance detection system that detects the inter-vehicle distance between your own troops and the vehicle in front, and issues an alarm when the distance becomes smaller than a safe inter-vehicle distance.・Regarding alarm devices.

<Conventional Technology> The majority of rear-end collisions involving trucks are caused by drivers falling asleep or driving distracted. Due to these circumstances, a following distance detection/warning device has been developed that detects the distance between the vehicle in front and the vehicle in front, and issues a warning to the driver when the distance becomes less than a certain distance. There is. The current outline of this device is to emit a laser beam in front of your own troops, receive the laser beam that is reflected by the rear flap of the vehicle in front, and calculate the inter-vehicle distance from that time. When the inter-vehicle distance falls below a predetermined distance, a buzzer inside the vehicle will sound.

<Problems to be Solved by the Invention> By the way, in the above-mentioned conventional device, the safe inter-vehicle distance, which triggers the generation of an alarm, is calculated by taking only the own speed into consideration.

However, in reality, even if the inter-vehicle distance is the same, the situation in which the warning is issued depends on the speed of the vehicle in front. In other words, depending on the speed of the vehicle in front, the warning may be generated too early and become annoying, or too late and may impair the driver's driving experience. For example, when the vehicle in front of the vehicle is stopped, the warning must be generated earlier than when the vehicle in front of the vehicle is moving.

Means for Solving the Problems> In order to solve the above problems, the present invention detects the time it takes for a laser beam emitted from the own vehicle to be reflected by the vehicle in front and returns, and calculates the inter-vehicle distance. The distance between vehicles is the braking distance of your vehicle,
In a following distance detection/warning device that issues an alarm when the following distance becomes smaller than a safe following distance determined based on the empty running distance, the safe following distance is determined by taking into account not only the speed of the own vehicle but also the speed of the vehicle in front. It was calculated using the following formula.

Function: This inter-vehicle distance detection/warning device calculates the safe inter-vehicle distance by taking into account the speed of the vehicle in front, so the timing of warning generation can be optimized.

<Embodiment> FIG. 1 shows the device configuration of an embodiment of the inter-vehicle distance detection/warning device according to the present invention, and FIG. 2 shows an outline of its mounting position relationship.

1 is a laser radar unit, which includes a light emitting section 2 and a light receiving section 3. The configuration of the laser radar unit 1 is shown in FIG.

The light emitting unit 2 includes a laser diode drive circuit 4, a laser diode 5, and a light emitting lens 6, and is configured to emit pulsed laser light at regular intervals. The light receiving section 3 includes a light receiving lens 7 that receives the laser light reflected by the front vehicle's steering flap, a photodiode 8, an amplifier 9, a signal processor 10, and the like. Based on the time difference Δt between the light emitted by the light emitting section 2 and the light received by the light receiving section 3, the inter-vehicle distance D (-x speed of light) is determined by the distance detection port-to-airway 11.

An inter-vehicle distance signal, which is a detection value of the laser radar unit 1, is input to a control unit 14 built into the lower side of the seat 13 of the truck 12.

The laser radar unit l is located on the bumper of the truck 12 as shown in FIG. In this embodiment, three light emitting sections 2 and three light receiving sections 3 are provided, and as shown in FIG. 4, three laser beams are mounted on the left, center, and right.

It is designed to emit 18b and 16C.

Reference numeral 17 denotes a vehicle speed sensor, which detects the vehicle speed from a rotating part of the transmission, etc. A detection signal from the vehicle speed sensor 17 is input to the control unit 14.

Reference numeral 18 denotes a steering sensor comprising a disk 19 provided on the steering column and a light emitting/light receiving section 20 for detecting the slit thereof, and a steering angle signal as a detection signal thereof is inputted to the control unit 14. There is.

Details of the steering sensor 18 are shown in FIGS. 7 and 8.

The disk 19 has slits 3 at regular intervals for angle detection.
One slit 32 for detecting the neutral position is provided inside the slit 32, and the position is shifted from the center between the slits 31. Light emitting section/light receiving section 20
There are two for detecting the slit 31 (20a, 20b).
, one (20c) for detecting the slit 32 is provided. Since the positional relationship of the slit 31 on both sides of the slit 32 is different, relative to the neutral position,
Whether the rotation is clockwise or counterclockwise is detected.

The neutral position is detected at a vehicle speed of 40km/h.
The time when the slit 32 is detected in the above manner is determined to be the neutral position, that is, the steering angle O0. Then, based on this position, detection is performed clockwise or counterclockwise several times depending on the detection amount of the slit 31.

A wiper switch 19 functions as an example of an environmental sensor, and its ON/OFF signals are input to the control unit 14. In other words, it is determined that it is raining when the wiper switch 19 is turned on.

Other environmental sensors 20 include a raindrop sensor, a road surface sensor (G sensor), a temperature sensor, a slip sensor, and the like. The rain sensor detects that it is raining, i.e. the road is wet, the road sensor detects whether the road is being steered or not, or other conditions, and the temperature sensor detects whether the road is steered or not. In combination with detection results from other sensors, the weather and road conditions, such as icy conditions, are detected. The slip sensor detects whether the road surface is prone to slipping, that is, whether the road is a low-μ road or a high-μ road, based on the rotational speed difference between the front wheels and the rear wheels.

The detection results are input to the control unit 14.

21 is a display unit built into the instrument panel in front of the driver's seat, which displays the following distance.
The system is equipped with a buzzer that issues a warning, and a lamp that flashes when the warning occurs to alert and even warn the driver.

Next, the calculation process leading to the generation of an alarm by the device of this embodiment will be explained.

The distance between the host vehicle 12 and the vehicle in front 22, that is, the inter-vehicle distance D
(m) is determined by the laser radar unit 1 as described above. The own vehicle speed Vf (m/s) is determined by the vehicle speed sensor 17.
Detected by The speed of the vehicle in front 22, Va (m/s), is calculated from the change in inter-vehicle distance 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 it takes for the driver to judge that it is dangerous and press the brake pedal, that is, the idle running time T d (s), the time that the driver judges that it is dangerous, that is, the judgment time T x (s), and the time for the driver to depress the brake pedal. Deceleration α.

(m/s") and the deceleration of the vehicle in front at (m/s") are stored in advance in the memory of the control unit 14. Deceleration α1. α is stored as a value assuming full braking, and is normally set as α1=α.

The braking distance of the front vehicle 22 is determined from the front vehicle speed Va and the deceleration α by L+=V a ”/2 α2.

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

The braking distance of the own vehicle 12 is the own vehicle speed Vf and the deceleration α,
It can be found from L, = V f'/2α1.

Therefore, the condition for generating an alarm is when the sum of the braking distance of the vehicle in front and the following distance becomes smaller than the sum of the automatic braking distance and the free running distance of the own troops. In other words, Va”/2a *+D< Vf”/2a,
+(Td+Tx)Vf Therefore, D< CTd+Tx)Vf+ (Vf''/2a, -
When Va''/2a=Ds (safe inter-vehicle distance), a warning is generated from the display unit 21 and the lamps are flashed.

As can be seen from this formula, since the speed of the vehicle in front 22 is taken into consideration when calculating the safe inter-vehicle distance Ds, it may be The optimal warning time is determined by whether or not the vehicle is stopped. When the vehicle in front 22 is stopped, Va=0 in the formula.

By the way, on wet or frozen roads in rainy weather, the deceleration of the vehicle is α3. α becomes smaller.

Therefore, when it is detected that the wiper switch 19 has been turned on, the control unit 14 changes the numerical value of the deceleration a++ α, and changes the alarm generation inter-vehicle distance. In other words, on a wet road surface, the safe inter-vehicle distance Ds is automatically changed, and the warning generation timing is brought forward. For example, the deceleration α on a dry road is 0.3G.
Depending on the road condition, the speed is changed from 0.2'G (for example, on a wet road) to 0.1G (for example, on an icy or snowy road).

Furthermore, when traveling along a highway circuit, each laser 16a is activated similarly to when traveling straight as shown in FIG.

If the detection area of the vehicle in front 22 by 16b and 16c is set aside, the guardrail flap will be detected, and the alarm will be issued frequently even though there is no need to issue an alarm. This actually distracts the driver's attention.

Therefore, in the travel circuit, the laser beam 16a.

16b and 16c change the area where it is detected whether or not there is a vehicle ahead (warning judgment area) to an area where the guardrail or flaper is not detected. That is, as shown in FIG. 6, each laser beam 16a is
.

16b, 16c alarm judgment area 5iSc.

It changes Sr. Note that the radius of road curvature R of the travel circuit 34 is determined from the steering angle by the steering sensor 18 described above, and based on this, the relationship between the radius of road curvature R determined in advance and the warning judgment area S (9th The alarm determination area of each laser beam 16a, '16b, and 16c is determined from the figure.

Next, the control unit 14 in the device of this embodiment
A specific example of control will be explained based on the flowchart of FIG.

First, initial values are set in step +1). In other words, the idle running time Td, the time of judgment ffTx, the deceleration α1 of the own vehicle 12 and the vehicle in front 22 when the brakes are fully applied. α, (α, = α,
) is set.

While the truck 12 is running, the following distance is calculated based on the above-mentioned calculation formula in step (2), and in step (3) the vehicle speed V is determined by the vehicle speed sensor 17.
f is detected, and in step (4), the speed Va of the front vehicle is determined from the change in the inter-vehicle distance and the own speed Vf, as described above.

Next, the environment, that is, the road surface condition is detected by the environment sensor 20 or the like (step (5)). For example, it is detected whether the wiper switch 19 is in the ON state.

Next, the deceleration of own troops and the vehicle in front α1. α is changed depending on the road surface condition (step (6)). Previous step (
If no environmental information is detected in step 5), the default deceleration α3. α, is adopted as is.

Next, in step (7), the host vehicle speed Vf, the front vehicle speed Va, the deceleration α1. α
A safe inter-vehicle distance Ds is calculated based on the following considerations. This safe inter-vehicle distance Ds takes into consideration the speed of the vehicle 22 in front and is appropriately modified according to the 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 determined whether the steering wheel is in a neutral position, that is, whether the vehicle is traveling straight or turning.

If the steering wheel is in the neutral position, step α
2, it is determined whether the current inter-vehicle distance is within the safe inter-vehicle distance Ds.

If the distance is within the safe inter-vehicle distance Ds, no warning is generated and only the inter-vehicle distance is displayed on the display unit 21.

If it is determined in step α2 that the inter-vehicle distance is smaller than the safe inter-vehicle distance Ds, then in step (13) the front vehicle speed Va and own vehicle speed Vf are compared. In this case, since the distance between vehicles is increasing, there is no need to issue a warning, and the process moves to step αυ.

If the distance Va of the vehicle in front is smaller than the own vehicle speed Vf, the vehicle is in the area where the warning should be issued and is gradually approaching, so a warning generation command is issued to the display unit 21 and the warning is issued. In addition, the following distance is also displayed.

On the other hand, if it is determined in step (8) above that the steering wheel is not in the neutral position, since the steering wheel is turning, each laser beam 16a is emitted based on the turning direction and steering angle.

Alarm judgment area SI of 16b and 16c! , Sc.

Sr is determined using the map 33 shown in FIG. In other words, as shown in Figure 6, the distance is limited and objects beyond that distance are not read. This operation is handled by not performing distance detection if the time it takes for the laser beam to return is longer than a certain time.

Next, the following distance and warning judgment area Sl.

Sc and Sr are compared (step αI), and if the inter-vehicle distance is larger than the warning judgment area Si Sc, Sr, the process moves to step αυ and no warning is generated.

Inter-vehicle distance is warning judgment area S II * S C, S
If it is smaller than r, it is determined in the next step Q2 whether the inter-vehicle distance is greater than the safe inter-vehicle distance Ds. Note that, in step α, the following distance and all warning judgment areas S1. To compare Sc and Sr,
This is to also detect vehicles cutting in.

After the step hits, comparison and judgment processing is performed in the same manner as described above.

The above calculations are repeated while the truck 12 is running.

Note that, as described above, the warning may or may not be issued depending on the comparison between the safe inter-vehicle distance Ds and the inter-vehicle distance, but it is also possible to issue the alarm in stages.

For example, when D<Ds, a buzzer will sound several times as the first warning (warning), and the second alarm will be given as D< TdVf+ (Vf'/ 2a + -Va"/
2a t)=Ds+, and in this case, the buzzer is made to sound continuously. This state does not require the driver's judgment, but rather requires the driver to step on the brakes immediately. If the warning is gradual, the driver will be able to respond quickly.

<Effects of the Invention> According to the inter-vehicle distance detection/warning device according to the present invention, the speed of the vehicle in front is also taken into account as a calculation element when calculating the safe distance between vehicles, so it is possible to calculate an appropriate distance according to the situation of the vehicle in front. The alarm generation timing can be obtained, and problems such as alarm delays or frequent alarms even when there is no dangerous situation can be solved.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the device configuration according to an embodiment of the present invention, Fig. 2 is an explanatory diagram of the general positional relationship of each component, Fig. 3 is an explanatory diagram of the laser radar unit, and Fig. 4 is a beam A plan view of the light starting state, FIG. 5 is an explanatory diagram of inter-vehicle distance, braking distance, etc., FIG. 6 is an explanatory diagram of how the warning judgment area is restricted when traveling on a turning path, and FIG. 7 is a perspective view of the steering sensor. FIG. 8 is an explanatory diagram of steering angle detection, FIG. 9 is a line diagram showing the relationship between the road radius of curvature and the warning judgment area, and FIG. 10 is a flowchart of one embodiment. In the drawing, 1 is a laser radar unit, 12 is the own vehicle, 14 is a control unit, 16a, 16b, 16c are light beams, 17 is a vehicle speed sensor, 18 is a steering sensor, 19 is a wiper switch, 20 is an environment sensor, 21 is a display unit.

Claims (1)

[Claims] The inter-vehicle distance is calculated by detecting the time it takes for the laser beam emitted by the own vehicle to reflect off the vehicle in front and return. In the following distance detection/warning device which issues an alarm when the distance becomes smaller than the following distance, the safe following distance is calculated by taking into account not only the speed of the own vehicle but also the speed of the vehicle in front. Inter-vehicle distance detection/warning device.