JPH06247244A - Inter-car distance alarm device - Google Patents

Abstract

PURPOSE:To enhance the alarm reliability refraining from re-emission of alarm in case the alarms emission is followed by non-sensing and then sensing is made again as long as the non-sensing time is below a certain value and the change amounts of the inter-car distance and relative speed are below the specified values gain. CONSTITUTION:A control unit 14 is fed with signals from an inter-car distance sensor 15 and a car speed sensor 16, calculates the smoothed inter-car distance and the relative speed of the car concerned with the foregoing car, determines the distance at which alarm is to be generated, and emits an alarm. If a momentary non-sensing state is generated by car motions up and down and to the left and right, followed by sensing of the foregoing car again, judgement is passed that the foregoing car is the same as before the non-sensing time as long as its duration is below a certain value and the change amounts of the inter-car distance and relative speed are below the respective specified values. The control means is constituted so that re-emission of alarm does not take place even though the foregoing car is within the distance to be alarmed, and thereby wasteful alarming is omitted.

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 warning device for detecting the inter-vehicle distance between an own vehicle and a front vehicle and issuing an alarm when the distance becomes a certain distance or less.

[0002]

2. Description of the Related Art The causes of rear-end collisions on highways are
The majority of drivers are drowsy driving and aimless driving.
Under such circumstances, a vehicle-to-vehicle distance warning device has been conventionally developed that detects the vehicle-to-vehicle distance between the own vehicle and the preceding vehicle and issues an alarm to the driver when the distance becomes a certain distance or less. There is. The outline of the conventional device is that laser light is emitted forward from the vehicle, and the laser light is reflected by the reflector on the rear surface of the front vehicle. The vehicle-to-vehicle distance is calculated from the vehicle-to-vehicle distance, and when the vehicle-to-vehicle distance becomes less than or equal to a predetermined distance, an alarm is issued by an alarm device in the vehicle compartment.

Normally, such an inter-vehicle distance warning device is designed to generate a warning in two stages. That is, when the inter-vehicle distance becomes less than a predetermined distance, a primary alarm is generated, and when the inter-vehicle distance is smaller, that is, when the own vehicle is closer to the preceding vehicle, a secondary alarm is issued to call attention to the driver. It has become.

[0004]

By the way, in the current traffic situation, it is not uncommon for the vehicle to continue traveling in an inter-vehicle distance state smaller than the primary alarm generation distance.

However, if the front vehicle cannot be detected due to the vertical movement of the vehicle, the positional relationship between the front vehicle and the host vehicle, or the like, while the vehicle is traveling within the warning distance, the inter-vehicle distance remains almost unchanged. However, an alarm will occur at the time of subsequent re-detection.

Such a situation may frequently occur depending on road conditions and the like. Such a situation is troublesome for the driver because the alarm is issued even if the inter-vehicle distance is almost unchanged, and the driver's alertness may be lowered.

As a technique for not issuing an alarm even when the inter-vehicle distance is within the alarm generation distance, for example, there is one disclosed in Japanese Utility Model Laid-Open No. 2-4367.
In this technique, for example, a safe inter-vehicle distance (second value) to a dangerous inter-vehicle distance after a lapse of a predetermined time after the safe inter-vehicle distance (first value) is changed to the safe inter-vehicle distance (second value). When (first value) is reached, an alarm is issued to warn the driver. Further, when a preceding vehicle starts after a predetermined time elapses after the vehicle is stopped due to a traffic jam or a signal, an alarm is issued to warn the driver. This is because it is considered that the driver is paying sufficient attention to the surroundings in the awake state of the driver who repeatedly performs the driving operation even when the own vehicle is close to the front vehicle. It was done. However, in the technique of this publication,
Even if the host vehicle gradually approaches the front vehicle and becomes a dangerous inter-vehicle distance, an alarm is not issued because the change from the first value to the second value has not occurred, and the front vehicle is suddenly braked. There is a drawback in that no alarm is issued at all, despite the inter-vehicle distance that may cause a rear-end collision when going.

[0008]

Means for Solving the Problems The present invention is to solve the above-mentioned problems, that is, in the case of re-detection after a momentary non-detection after detecting a vehicle in front and issuing an alarm, The purpose is to prevent the alarm from being issued under certain conditions, and the configuration detects the inter-vehicle distance between the vehicle in front and the own vehicle, and this inter-vehicle distance is smaller than the warning inter-vehicle distance previously obtained. In the inter-vehicle distance warning device that generates an alarm when the following occurs, the front vehicle is not detected after the front vehicle is detected and the inter-vehicle distance becomes smaller than the warning inter-vehicle distance to generate an alarm. , When the vehicle ahead is detected again, it is determined whether the vehicle ahead is the vehicle detected before the non-detection based on the non-detected time, the change amount of the inter-vehicle distance, and the change amount of the relative speed. , The vehicle that was previously detected The case is characterized in that constitute a control means so as not to generate an alarm.

[0009]

In this inter-vehicle distance warning device, an alarm is issued when the inter-vehicle distance between the vehicle ahead and the host vehicle becomes smaller than the predetermined inter-vehicle distance. When the front vehicle is not detected due to vertical movement of the vehicle, left / right displacement, etc., and when the front vehicle is detected again after that, the front vehicle is not detected for a predetermined time or less, and the change amount of the inter-vehicle distance is a predetermined value. Hereinafter, when the amount of change in the relative speed is less than or equal to the predetermined value, the warning is not issued again even within the warning inter-vehicle distance. If the inter-vehicle distance becomes narrower, an alarm that calls more attention is issued.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a general outline of an inter-vehicle distance warning device which is partly composed of an inter-vehicle distance display device according to the present invention is shown in FIG.
4 to FIG.

In FIG. 2, reference numeral 1 denotes a laser radar unit incorporated in a front bumper of a vehicle or the like, which includes a light emitting section 2 and a light receiving section 3 as shown in FIG. The light emitting section 2 is composed of a laser diode drive circuit 4, a laser diode 5, and a light emitting lens 6, and emits a laser beam 7 in a pulse shape at regular time intervals. The light receiving unit 3 includes a light receiving lens 9 that receives the laser beam reflected by the reflector 8a of the front vehicle 8, a photodiode 10, an amplifier 11, a signal processor 12, and the like. Based on the time difference Δt between the light emission by the light emitting unit 2 and the light reception by the light receiving unit 3, the distance detection circuit 13 determines the inter-vehicle distance D.
(= (Δt / 2) × light speed) is obtained. An inter-vehicle distance signal which is a detection value of the laser radar unit 1 is input to a control unit 14 which is a control means mounted on the vehicle.

As shown in FIG. 4, the control unit 14 receives signals from an inter-vehicle distance sensor 15 including the distance detecting circuit 13 and the like, a vehicle speed sensor 16 for detecting the vehicle speed of the host vehicle, and the like. In the control unit 14, first, the inter-vehicle distance from the inter-vehicle distance sensor 15 is subjected to inter-vehicle distance calculation such as smoothing and determination of correct distance, and the relative speed between the front vehicle and the host vehicle is calculated from the obtained inter-vehicle distance. Based on the relative speed and the signal from the vehicle speed sensor 16, the distance at which the alarm should be issued is obtained.

That is, as described above, the distance (vehicle distance D (m)) between the vehicle and the front vehicle 8 is obtained by the vehicle distance sensor 15, and the vehicle speed Vf (m / s) is the vehicle speed. Sensor 1
6, the speed Va (m / s) of the front vehicle 8 is calculated from the change in the inter-vehicle distance D per minute time. On the other hand, the time until the driver determines that the driver is dangerous and depresses the brake pedal, that is, the free running time Td (s), the time when the driver determines that the driver is dangerous, that is, the determination time Tx (s) and the deceleration α of the vehicle. ₁ (m / s ² ) and deceleration α of the front vehicle
₂ (m / s ² ) is stored in advance in the memory of the control unit 14. 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 8 is equal to the front vehicle speed V
From a and deceleration α _2, it can be obtained by L ₁ = Va ² / 2α ₂ . The free-running distance L ₂ of the vehicle is determined by the vehicle speed Vf and the free-running time T.
From d and the judgment time Tx, L ₂ = (Td + Tx) Vf can be obtained. The braking distance L ₃ of the own vehicle is obtained by L ₃ = Vf ² / 2α ₁ from the own vehicle speed Vf and the deceleration α ₁ .

Therefore, as a condition for issuing an alarm, the sum of the front vehicle braking distance L ₁ and the inter-vehicle distance D is the own vehicle braking distance L ₃
When the distance between the vehicle and the free running distance L _{2 of the} vehicle becomes smaller, the timing becomes smaller. 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 /
When 2α ₂ ) = Ds (safe inter-vehicle distance), it is determined that the alarm is to be issued.

The alarm is issued by the alarm generator 24. The alarm generator 24 includes an alarm lamp 24a and an alarm alarm 24.
It consists of b. The warning is given in two stages. For example, when became D <Ds, as described above with the primary ^{alarm, D <TdVf + (Vf 2} / 2α 1 -Va 2 / 2α 2) =
A secondary alarm is issued when Ds ₁ is closer. In the primary alarm, the alarm lamp 24a is turned on and the alarm sound is emitted only once. In the case of the secondary alarm, the alarm lamp 24a
Blink and make the alarm beep intermittently.

Further, an alarm output calculation of what kind of alarm should be issued from the obtained alarm generation distance and the own vehicle traveling distance obtained from the signal from the vehicle speed sensor 16 and whether or not the alarm itself should be generated The alarm is generated and the result is input to the alarm generator 24, and the alarm is generated or not generated. As shown in FIG. 2, the inter-vehicle distance indicator 25 displays the inter-vehicle distance.

Next, a specific example of the control contents according to the present invention for preventing the primary alarm from being generated when the preceding vehicle becomes undetected and the preceding vehicle is detected after the primary alarm is generated is shown in FIG. It will be described based on the flowchart of FIG. As described above, first, it is judged by the input from the inter-vehicle distance sensor 16 (step (1)) whether the inter-vehicle distance is detected (step (2)). For example, if there is a target (front vehicle or the like) ahead of the detectable distance by the laser radar unit 1, it is not detected (No), and if it is within that range, the front vehicle or the like is detected, that is, Yes. The inter-vehicle distance is detected, for example, every 100 ms (milliseconds).

If it is determined in step (2) that the vehicle is not detected, the previous inter-vehicle distance is replaced with infinity (step (23)), and the traveling distance is cleared (step (2
4)) and integrates the non-detection continuation timer (step (2
5)), and the alarm generation flag is set to 0 (step (2
6)). In this case, of course, no alarm is issued and the routine returns from this routine to start.

If it is judged Yes in step (2), that is, if the preceding vehicle is detected, then the absolute value of the difference between the inter-vehicle distance detected this time and the inter-vehicle distance detected last time is 5 m or less. It is judged (step (3)). That is, it is determined whether the preceding vehicle is continued and is normally detected.

If Yes in step (3), the inter-vehicle distance detected this time is replaced with the inter-vehicle distance detected previously (step (4)). In addition, the traveling distance during the detection is integrated (step (5)). When the traveling distance is 120 m or more, the detected target is determined to be the preceding vehicle (step (6)), and the preceding vehicle flag is set to 1 (step (7)). Further, the current inter-vehicle distance is stored as a value immediately before non-detection in preparation for non-detection (step (8)).

When it is determined No in step (3), the inter-vehicle distance detected this time is replaced with the previous inter-vehicle distance (step (27)), and the process proceeds to step (24) and thereafter.
That is, the traveling distance during the detection continuation is cleared, the non-detection distance is cleared (step (24)), the non-detection continuation timer is integrated (step (25)), and the alarm generation flag is set to 0 (step (26)). , Exit this routine.
It should be noted that the first time the previous vehicle is detected again (or a new vehicle) after the previous vehicle has not been detected, the previous inter-vehicle distance is infinite, so (current inter-vehicle distance-infinity = infinity), The determination result is No.

As described above, in preparation for non-detection, the inter-vehicle distance this time is stored as a value immediately before non-detection (step (8)), and then the relative speeds of the preceding vehicle and the host vehicle are calculated (step (9)). Then, the inter-vehicle distance for alarm generation is calculated (step (10)).

In the calculation of the warning inter-vehicle distance, the warning inter-vehicle distance (Din) (primary warning inter-vehicle distance) when initially determining that the warning is within the warning inter-vehicle distance area and the warning inter-vehicle distance outside the warning inter-vehicle distance area Two of the warning inter-vehicle distances (Dout) are calculated at the same time. By setting Dout = Din + predetermined value (for example, 3 m), a hysteresis is provided between Din and Dout, and the first warning (primary warning) is issued only when it is determined that the vehicle is within the warning inter-vehicle distance area. It is possible to reduce the occurrence of alarms when the host vehicle travels in front of and behind the preceding vehicle.

Next, the current inter-vehicle distance and the warning inter-vehicle distance are compared (step (11)). When making this determination, it is first determined whether or not the alarm generation flag is 0, and when the alarm generation flag is 0, the above-mentioned alarm inter-vehicle distance Din is adopted as the alarm inter-vehicle distance, and the alarm generation flag is not 0. Sometimes, the warning inter-vehicle distance Dout is adopted as the warning inter-vehicle distance. That is, the frequent occurrence of alarms due to the change in the inter-vehicle distance before and after the warning inter-vehicle distance is suppressed.

Here, when the inter-vehicle distance detected this time is not smaller than the warning inter-vehicle distance, that is, when it is determined to be No,
The alarm generation flag is set to 0 (step (28)), and this routine is exited.

If it is determined in step (11) that the inter-vehicle distance detected this time is smaller than the warning inter-vehicle distance, that is, Yes, it is next determined whether the warning generation flag is 0 (step (12)). If the alarm generation flag is not 0, it is not necessary to generate an alarm, so this routine is directly terminated.

At step (12), the warning flag is set to 0.
If it is determined that the following is true, then it is determined whether the previously detected inter-vehicle distance is shorter than the previous warning inter-vehicle distance (step (13)). In this determination, the absolute value of the difference between the inter-vehicle distance detected this time and the inter-vehicle distance detected last time is smaller than 5 m (determined in step (3)), and the state is 120
The target is continuously detected for m or more (determined in step (6)), and it is determined whether or not the alarm generation distance has not been reached since the continuous detection of the target was started.

Therefore, if the previous inter-vehicle distance is also larger than the previous warning inter-vehicle distance, that is, if No is determined,
The preceding vehicle flag is set to 0 (step (29)) and the later-described processing of setting an alarm generation flag to 1 (step (19)) is avoided, and processing for determining whether or not to generate an alarm is reached (step (20)). (21) (22)).

If it is determined Yes in step (13), it is then determined whether the integrated value of the non-detection continuation timer is smaller than a predetermined value (for example, 5 seconds) (step (1
4)). The non-detection continuation timer is as described above (in the case of non-detection, the integration is disclosed (steps (2) and (24)).

When the non-detection integrated value is less than 5 seconds, the absolute value of the difference between the inter-vehicle distance immediately before non-detection (taken in step (8)) and the current inter-vehicle distance is next. It is judged whether or not it is smaller than a predetermined value (for example, 5 m) (step (15)), and then whether or not the absolute value of the relative speed between the preceding vehicle and the own vehicle is smaller than a predetermined value (for example, 2 m / s). A judgment is made (step (16)). When the conditions of these steps (14), (15), and (16) are satisfied, that is, when it is determined to be Yes in each case, the vehicle may move up and down or the positional relationship between the preceding vehicle and the host vehicle may shift. It is determined that the preceding vehicle is not detected for a moment and the same preceding vehicle is detected thereafter.

Therefore, the non-detection continuation timer is cleared (step (17)), then it is judged whether or not the preceding vehicle flag is 1 (step (18)), and if the preceding vehicle flag is 1, the alarm generation flag is set. 1 (step (1
9)).

Next, it is judged whether the alarm generation flag is 0 (step (20)). When the alarm generation flag is set to 1 in the previous step, it is determined as No, no alarm is generated, and the routine exits. That is, the preceding vehicle is not detected for a moment due to the positional relationship between the preceding vehicle and the own vehicle, and when the same preceding vehicle is detected thereafter, the warning is not issued again. As a result, the generation of unnecessary alarms is suppressed.

In the above step (6), if the mileage does not exceed 120 m when the difference between the inter-vehicle distances is within 5 m, it is not judged as a preceding vehicle, and therefore steps (7) and (8) are executed. Then, the process goes to step (9) of calculating the relative speed. In this case, the preceding vehicle flag is 1
Therefore, if it is within the warning inter-vehicle distance, No is determined in step (18), and step (20)
Since the alarm generation flag is 0 here, the result is Yes.
Then, an alarm (primary alarm) is issued (step (21)).

Thereafter, the alarm generation flag is set to 1 (step (22)), and this routine is exited. Here, the alarm generation flag is set to 1 to stop the generation of the second and subsequent primary alarms.

When the host vehicle approaches the preceding vehicle and enters the secondary warning inter-vehicle distance, the secondary warning is issued.

[0037]

According to the inter-vehicle distance warning device of the present invention, there is a momentary non-detection state when the vehicle moves vertically and horizontally and the preceding vehicle cannot be continuously detected, for example, when traveling on a rough road. As a result, it can be determined that the vehicle was detected before non-detection, and the alarm will not be generated as a new vehicle by re-detection after a momentary non-detection. Improves reliability.

[Brief description of drawings]

FIG. 1 is a flowchart of control contents according to an embodiment of the present invention.

FIG. 2 is a conceptual diagram of an inter-vehicle distance warning device to which the present invention is applied.

FIG. 3 is an explanatory diagram of a laser radar unit in an inter-vehicle distance warning device.

FIG. 4 is a block diagram of a control unit in the inter-vehicle distance warning device.

[Explanation of symbols]

 1 Laser radar unit 2 Laser beam 8 Front vehicle 14 Control unit 24 Alarm generator 25 Inter-vehicle distance indicator

Claims (1)

[Claims] 1. An inter-vehicle distance warning device for detecting an inter-vehicle distance between a vehicle in front and an own vehicle, and issuing an alarm when the inter-vehicle distance becomes smaller than a predetermined warning inter-vehicle distance. When the vehicle in front of the vehicle is detected and the inter-vehicle distance becomes smaller than the warning inter-vehicle distance and an alarm is issued, the non-detection state of the vehicle in front occurs, and when the vehicle in front is detected again, Based on the amount of change in inter-vehicle distance and the amount of change in relative speed, determine whether the vehicle ahead is a vehicle that was detected before non-detection, and do not issue an alarm if it is the vehicle that was previously detected. An inter-vehicle distance warning device characterized in that the control means is configured in the.