JPH06109845A - Between-vehicles-distance alarm apparatus - Google Patents

Abstract

(57) [Summary] [Purpose] To perform an appropriate range cut. [Structure] An object for distance measurement is estimated from the characteristics on the waveform of an inter-vehicle distance signal, and the maximum detection distance of range cut processing is changed based on the estimation result.

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 which measures an inter-vehicle distance between an own vehicle and a front vehicle and issues an alarm when the distance becomes a predetermined distance or less. When measuring the vehicle-to-vehicle distance, it is estimated whether or not the object to be measured is a vehicle so that a warning may not be issued by mistakenly identifying a reflector or sign on the guardrail as a preceding vehicle, and depending on the estimation result. And a device for changing the maximum detection distance.

[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 these circumstances, we have developed a vehicle-to-vehicle distance detection / alarm system that detects the vehicle-to-vehicle distance between the vehicle and the front vehicle and alerts the driver when the distance falls below a certain distance. Has been done. The outline of the conventional one of this device is that a laser beam or the like is emitted forward from the own vehicle, and the laser beam or the like hits a reflector or the like on the rear surface of the front vehicle and is reflected, and the time is received. The inter-vehicle distance is calculated from the distance, and when the inter-vehicle distance becomes equal to or less than a predetermined distance, the buzzer in the vehicle interior is sounded.

In this case, if the distance between the guardrail reflector or the signs and the vehicle is measured, an alarm will be erroneously issued. Therefore, conventionally, an inter-vehicle distance warning device aimed at preventing this kind of false alarm has been disclosed in the following documents 1 and 2.
Is disclosed in. (1) Reference 1: “Toru Yasama et al.,“ A rear-end collision prevention warning device for heavy-duty trucks, Automotive Technology Papers, Vol. 43, No. 2, 19 ”
89 "(2) Document 2:" Kaikaihei 2-119799 "

In the above-mentioned documents 1 and 2, it is considered that the guardrail reflectors and the signs are stationary objects, and that the distance measurement data for them are generated at a constant interval, and "the stationary object at which the distance measurement data is generated at a constant interval". Under this condition, it is estimated whether the object to be measured is a guardrail reflector or a sign, and false alarms are prevented.

On the other hand, there is a range cut processing functioning as a filter for validating only a value equal to or less than the maximum detected distance among the detected inter-vehicle distances, and based on the steering wheel angle, or based on the steering wheel angle and the vehicle speed. By changing the maximum detection distance and using the inter-vehicle distance value range-cut by the maximum detection distance to determine whether or not an alarm should be issued, erroneous detection of road facilities (guardrails, guardrail reflectors, signs, etc.) and False alarms due to are being prevented in advance.

[0006]

The above-mentioned conventional estimation method has the following inconvenience because "the stationary object in which the distance measurement data occurs at regular intervals" is used as the estimation condition. (1) From the condition that "distance measurement data occurs at regular intervals", only those observed in pulse form at regular intervals on the waveform of the distance data, that is, guardrail reflectors and signs,
The target object cannot be identified. Therefore, rocks, forests, arrow blades, guardrails, etc. cannot be distinguished from the preceding vehicle. (2) The estimation cannot be performed unless it can be determined that the measurement object is stopped from the condition of “stopped object”. This is an important issue, and in order to determine the stop of an object from the output of a distance sensor that measures only general distance, it is necessary to take the time differential value of the distance measurement value, so accurate stop in a short time. It is difficult to make a decision. Therefore, it is almost impossible to estimate fast processing in near real time. Further, it cannot be estimated for an object that is not directly facing the course of the vehicle.

Further, in the above conventional range cut processing,
There are the following inconveniences. (1) If the curvature of the turning circle changes while traveling on a curved road,
It does not have an appropriate range cut. (2) There is no proper range cut near the exit of a curved road. (3) An accurate turning radius cannot be estimated only from the steering wheel angle and the vehicle speed.

An object of the present invention is to provide an inter-vehicle distance warning device that can solve the above problems.

[0009]

A method of estimating an object to be measured according to the present invention relates to an inter-vehicle distance sensor for detecting an inter-vehicle distance between a front vehicle and an own vehicle, and a distance signal output from the inter-vehicle distance sensor. In a vehicle-to-vehicle distance warning device having a controller that issues a warning when a value equal to or less than the maximum detection distance is valid and a valid distance signal value is smaller than a safe vehicle-to-vehicle distance, the controller is (1) falling of a ranging data waveform When the rising edge is detected within the first predetermined time after the falling edge, it is determined to be noise, and when the falling edge or the rising edge is detected within the second predetermined time after determining the noise, distance measurement is performed. If the object is estimated to be an object other than the vehicle, and if a fall or rise is detected within the third predetermined time after the object is estimated to be an object other than the vehicle, the distance measurement object is estimated to be an object other than the vehicle, Regardless of each of the above estimations, distance measuring object estimation means for estimating the distance measuring object as a vehicle when a rising edge is detected when the first predetermined time has elapsed after the falling edge, and (2) distance measuring object And a means for changing the maximum detection distance according to the estimation result of 1.

[0010]

The present invention was made by paying attention to the continuity of the distance measurement data waveform. The distance measurement data waveform falls when there is an object to be measured and rises when it disappears. The inter-vehicle distance signal is usually noise-removed by central filtering or the like, but if there is noise that cannot be completely removed, the width of the noise is narrow, so if it rises within the first predetermined time after the fall, noise will be generated. It can be determined that there is. When the measurement target is a vehicle, the width is wider than the noise, and therefore it can be estimated that the vehicle is a vehicle if it falls after the fourth predetermined time after the fall. Further, when the falling or rising is not detected within the third predetermined time, in other cases, it can be estimated as an object other than the vehicle. Therefore, when it is estimated that the vehicle is other than the vehicle, the maximum detection distance is set to be equal to or smaller than the current value to suppress the occurrence of false alarms. On the contrary, when the vehicle is estimated to be the vehicle, the maximum detection distance is set to be equal to or longer than the current one so that the alarm can be surely issued from the distance from the preceding vehicle.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the embodiments shown in the drawings. First, an example of an inter-vehicle distance warning device, which is a premise of this embodiment, will be described with reference to FIG. Reference numeral 1 denotes a laser radar unit as an inter-vehicle distance sensor incorporated in a front bumper of a vehicle, etc. As shown in FIG.
And a light emitting unit 3. 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 receives the laser beam reflected by the reflector 8a of the front vehicle 8, a light receiving lens 9, a photodiode 10, and an amplifier 1.
1, a signal processor 12 and the like. These light emitting parts 2
The inter-vehicle distance D (= Δt / 2) × speed of light) is obtained by the distance detection circuit 13 from the time difference Δt between the light emission by (1) and the light reception by the light receiving unit 3. The inter-vehicle distance signal which is the detection value of the laser radar unit 1 is input to the control unit 14 mounted on the vehicle.

Information such as the vehicle speed, the steering wheel angle, and the turn signal of the vehicle is also input to the control unit 14. A block diagram of sensors for that purpose is shown in FIG. As shown in this figure, an inter-vehicle distance sensor 15 including the above-described distance detection circuit 13, a vehicle speed sensor 16 for detecting the vehicle speed of the host vehicle, an accelerator opening sensor 17, a shift position detector 1
8, a stop lamp switch 19, a turn signal switch 20, and the like, and signals from these sensors 16 and the like are input to the control unit 14. Specifically, signals from the stop lamp switch 19, the turn signal switch 20, the inter-vehicle distance sensor 15, the vehicle speed sensor 16 and the like are input to the calculation unit 21 of the control unit 14, and the accelerator opening sensor 17 and the shift position detector 18 are provided. The detection signal is input to the comparator 22.

In the arithmetic unit 21, the sensors 15, 16 etc.
Based on the input signal of
A state in which an alarm should be issued, including a change in the large detection distance
Whether or not the rear-end collision delay time is calculated. Estimation method and
And the change of the maximum detection distance will be explained later, but as described above.
In addition, the distance between the own vehicle and the front vehicle 8 (inter-vehicle distance D (m)) is
The vehicle speed Vf (m
/ S) is detected by the vehicle speed sensor 16 and is the speed of the front vehicle 8.
The degree Va (m / s) is a change in the inter-vehicle distance D per minute time.
Is calculated by On the other hand, if the driver is
Time to judge and depress the brake pedal, that is, idle
Time Td (s), time when the driver judges that it is dangerous,
Judgment time Tx (s) and deceleration α of the host vehicle₁(M /
s²) And the deceleration α of the front vehicle₂(M / s²) Is in advance
It is stored in the memory of the console unit 14. Deceleration
α₁, Α₂Stores the value assuming full braking,
Usually α ₁= Α₂It is said that

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 generating an alarm, the sum of the front vehicle braking distance L ₁ and the inter-vehicle distance D is the automatic braking distance L _2.
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 Accordingly, D <(Td + Tx) Vf + Vf 2 / 2α 1 -Va 2/2
When α ₂ ) = Ds (safe inter-vehicle distance), it is determined that the alarm is to be issued.

In the present embodiment, the above calculation is not performed each time, and an alarm is issued based on the relationship between the vehicle speed Vf and the relative speed (speed difference between the preceding vehicle and the vehicle) dv as shown in FIG. The generation distance is obtained as a map 23 and is read. The result read from the map 23 is input to the alarm generator 24. The alarm generator 24 includes an alarm lamp 24a, an alarm alarm 24b, an inter-vehicle distance display panel 24c, etc. as shown in FIG.

The alarm is issued in two stages. For example, when became D <Ds, as described above with the primary ^{alarm, D <TdDf + (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, the rear-end collision delay time t is a time required for a rear-end collision to take several seconds in the current traveling state of the own vehicle, assuming that the traveling state of the front vehicle 8 is unchanged. Relative velocity). This collision delay time t
Is input to the comparator 22 and compared with a preset predetermined value (threshold value). FIG. 5 shows the threshold value. As described above, the detection signal of the accelerator opening sensor 17 is input to the comparator 22, and the driver's deceleration action is determined based on this signal. When it is determined that the vehicle is decelerating and the post-collision delay time has exceeded the threshold value, a shift command is issued to the controller 25 of the automatic transmission in order to shift down and apply engine braking as an aid to the deceleration. Will be issued. FIG. 1 shows the overdrive release mechanism 26.

Next, an embodiment of the method of estimating the measuring object will be described. As shown in FIG. 6, the calculator 21 detects the falling edge and the rising edge as the waveform edges of the inter-vehicle distance signal 27. For example, when the inter-vehicle distance decreases by 3 m or more in 0.1 seconds, it is defined as the falling edge, and when it increases by 3 m or more in the 0.1 seconds, it is defined as the rising edge. The calculation unit 21 has an alarm stop preparation timer and an alarm stop timer. If the vehicle rises within a first predetermined time after falling, for example, within 1.5 seconds, the inter-vehicle distance data is regarded as noise, and as shown in FIG. Then, the alarm stop preparation timer for a second predetermined time, for example, 5 seconds is activated. If a fall or rise is detected within this alarm stop preparation timer, it is estimated that the object to be measured is an object other than the vehicle and the alarm stop mode is entered, and the alarm stop timer for a third predetermined time, for example 10 seconds, is activated. To do. If a further fall or rise is detected during the operation of the alarm stop timer, it is presumed to be an object other than the vehicle, and the alarm stop timer is reset as in, ..., And the alarm stop time is automatically extended. However, even before this alarm stop timer has passed 10 seconds,
When the pulse width from the falling edge to the rising edge exceeds the fourth predetermined time, for example, 1.5 seconds, as shown in FIG.

Next, with reference to FIGS. 7 to 16, the estimation of the object to be measured will be described in detail. First, the inter-vehicle distance signal is subjected to noise removal by median filtering or the like, but it is necessary to distinguish noise that cannot be completely removed from normal signals. Generally, the noise of the inter-vehicle distance signal is as shown in FIG.
Since it is often detected as shown in (b), these are used as criteria. The overall processing flow for estimating the object to be measured is shown in FIG. 8, and includes detection / non-detection determination S1, waveform edge detection S2, noise determination S3, and detection state (noise determination value) output S5.

The determination of detection / non-detection is to determine whether the measured value of the inter-vehicle distance, that is, the inter-vehicle distance determination value is within the set maximum detection distance as shown in FIG.
If the maximum detection distance is exceeded in step 1, the failure detection flag is set (step S13), and if it is within the maximum detection distance, the failure detection flag is cleared (step S12). When the fail detection flag is set, the reception duration time counters 1 and 2
Are cleared together (steps S14 and S15).

As shown in FIG. 10, the determination of the waveform edge is to determine the trailing edge and the rising edge of the inter-vehicle distance signal waveform. In step S21, the inter-vehicle distance determination value is a predetermined time, for example, 0.1 seconds before. Predetermined value, for example 5m
If it has decreased more than this, it is determined to be a fall and the detection state value is set to 1 (step S22). NO in step S21
In the case of (negative), the process proceeds to step S23, and when the inter-vehicle distance determination value has increased by 5 m or more compared to a predetermined time, for example, 0.1 seconds ago, it is determined to be rising and the detection state value is set to 2 (step S24). ). If NO in step S23,
It is determined that there is no change in the waveform and the detection state value is set to 0 (step S25). When the detection state value is 1 or 2,
The reception duration counter 2 is cleared (step S2
6, S27).

As shown in FIGS. 11 to 14, the noise determination is to determine whether it is a noise or a vehicle based on the detection state value of the waveform and the presence / absence of a non-detection flag. In step S31, the waveform detection state value is 1 If it is a falling edge, the reception continuation time measurement flag is set in step S32 and then the process proceeds to step S33. If there is no rising edge or no change, the process directly proceeds to step S33. In step S33, it is determined whether or not the non-detection flag is cleared (within the maximum detection distance) and the reception duration time exceeds the noise determination pulse width, for example, 1.5 seconds. In the case of YES (affirmation), the measurement object is a vehicle, the reception duration measurement flag is cleared (step S34), the waveform edge detection wait timer is set to 0 (step S35), and the noise detection timer is set to 0 (step S35). S36), the noise detection flag is cleared (step S37), and the process proceeds to step S48 in FIG.

If NO in step S33, in step S38 of FIG. 12, it is determined whether the noise detection flag is cleared, the reception duration measurement flag is set, and the waveform detection state value is 2, that is, rising. To judge. YE
If S is noise, a noise detection flag is set (step S39), a waveform edge detection timer is set to a timer first initial value, for example, 5 seconds to prepare for alarm stop (step S40), and a reception duration measurement flag is set. It clears (step S41), and moves to step S48 of FIG.

If NO in step S38, it is determined in step S42 whether the noise detection flag is set and the detection state value of the waveform is not 0, that is, whether it is rising or falling. If YES, in step S43 of FIG. 13, it is determined whether or not the waveform edge detection waiting timer is greater than 0. If it is greater than 0, the alarm stop mode is entered, and the noise detection timer is set to the timer second initial value, for example, 10
Seconds (step S44), the waveform edge detection wait timer is set to 0 (step S45), the noise detection flag is cleared (step S46), the reception duration measurement flag is cleared (step S47), and the process proceeds to step S48. . The waveform edge detection wait timer is set to 0 in step S43.
If it is below, the process proceeds to step S48 through steps S46 and S47. Further, in step S42 of FIG.
Also in the case of O, the process proceeds to step S48.

In step S48, it is determined whether or not the value of the noise detection timer is larger than 0. If it is larger, the timer value is decreased and an alarm stop flag is set (steps S49 and S50). The stop flag is cleared (step S51), and the process proceeds to step S52 in FIG. In this step S52, it is judged whether or not the value of the waveform edge detection waiting timer is larger than 0, and if it is larger, the timer value is decreased (step S53). If it is 0, leave it as it is.

The noise judgment value is output by dividing the above noise judgment result into noise judgment values of 0 to 3 as shown in FIG. 15, and in step S61 of FIG. 15, the alarm stop flag is set. It is determined whether or not the vehicle is standing and the reception duration is within the threshold value of the noise determination pulse width, for example, within 1.5 seconds, the non-detection flag is cleared, and the inter-vehicle distance determination value is a predetermined value, for example, 10 m or more. To do. If this is YES, the inter-vehicle distance signal contains noise and is abnormal, so the noise determination value is set to 3 (step S
62), the reception duration counter 2 is cleared (step S63). If NO in step S61, the process proceeds to step S64 in FIG. 16, and it is determined whether or not the non-detection flag is set. If the non-detection flag is set, the inter-vehicle distance determination value exceeds the maximum detection distance. The object is in the non-detection state with respect to the object to be measured, and the noise judgment value is set to 2 (step S
65), and then the reception duration counters 1 and 2 are cleared (steps S66 and S67). If the non-detection flag is cleared, the object to be measured is a vehicle and is normal, so the noise determination value is set to 1 in step S68.

As a result of the above processing, the distance measurement data is shown in FIG.
In the case of the waveform shown in (a), noise determination values 0 to 3 are output in the state shown in FIG. As a result,
As shown in FIG. 8 (a), even an object that is not directly facing the course of the vehicle 28, for example, a guardrail 29 on a curve,
Since the waveform as shown in FIG. 6B is obtained, it is possible to estimate whether it is noise or a vehicle.

Next, the change of the maximum detection distance in the range cut processing will be described with reference to FIG. In this embodiment, the shaded portion in FIG. 17, that is, the noise determination value N _f
Is detected when the vehicle is 1 and when the noise determination value N _f is not 3 is the timing of changing the maximum detection distance.

In FIG. 19, in step S71, it is determined whether or not the inter-vehicle distance determination value, that is, the distance output of the inter-vehicle distance sensor is within the current maximum detection distance D _0. If YES, the process proceeds to next step S72. Then, it is determined whether or not the noise determination value N _f is 3. If N _f = 3, the result of estimation of the object to be measured is not a vehicle. Therefore, in step S73, the maximum detection distance D _{0 is set} to the distance measurement value (distance output value) D _t of the current inter-vehicle distance sensor or less. Change the setting to to suppress the occurrence of false alarms. If NO in step S72, there is a possibility of a vehicle, so the maximum detection distance D ₀ is held in step S74. Since usually the maximum detection distance D ₀ is in the last distance value D _t-1, will be held in D _t-1.

In the first step S71, NO, that is, distance measurement
Value is maximum detection distance D₀If it exceeds, step S
Noise judgment value N at 75_fIt is determined whether is 1. N_f
If = 1 then the result of estimation of the object to be measured is a vehicle,
In the next step S76, the maximum detection distance D₀The initial value
For example, if you reset the setting to 100m, you can be sure of the warning from the distance from the preceding vehicle.
I will be able to serve you. If NO in step S75
If there is a possibility other than the vehicle, first step S
Current maximum detection distance D at 77₀Whether is the initial value
If YES in the determination, D in step S78₀= Initial
Hold as is. If NO, step S79.
At maximum detection distance D₀This distance measurement value D _fOr later
Change the setting to a lower value to suppress false alarms.

[0032]

According to the present invention, the range-finding object is estimated from the waveform of the inter-vehicle distance data, and the maximum detection distance in the range-cut processing is changed from the estimation result, so that an appropriate range cut can be performed. it can. Further, since the steering wheel angle sensor does not depend on the steering wheel angle, the inter-vehicle distance warning device is simplified. Furthermore, the present invention can be applied to a plurality of inter-vehicle distance sensors or an inter-vehicle distance alarm device including inter-vehicle distance sensors having detection areas in a plurality of directions.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of an inter-vehicle distance warning device to which the present invention is applied.

FIG. 2 is an explanatory diagram of a laser radar unit.

FIG. 3 is a block diagram showing an outline of a control unit.

FIG. 4 is an inter-vehicle distance warning map for obtaining an alarm generation distance from a vehicle speed and a relative speed.

FIG. 5 is a diagram showing a threshold value of a rear-end collision delay time.

FIG. 6 is an explanatory diagram of an embodiment of estimation of a distance measurement object according to the present invention.

FIG. 7 is a diagram showing an example of a noise waveform.

FIG. 8 is a diagram showing an overall processing flow of noise determination.

FIG. 9 is a diagram showing a processing flow of detection / rejection detection.

FIG. 10 is a diagram showing a processing flow of waveform edge determination.

FIG. 11 is a diagram illustrating a processing flow of noise determination.

FIG. 12 is a diagram showing a processing flow of noise determination.

FIG. 13 is a diagram showing a processing flow of noise determination.

FIG. 14 is a diagram showing a processing flow of noise determination.

FIG. 15 is a diagram showing a processing flow of noise determination value output.

FIG. 16 is a diagram showing a processing flow of noise determination value output.

FIG. 17 is a diagram showing a correspondence relationship between waveforms and noise determination values.

FIG. 18 is a diagram showing an example of an object that is not on the route of the vehicle and its waveform.

FIG. 19 is a diagram showing a processing flow of an embodiment of changing the maximum detection distance in the present invention.

[Explanation of symbols]

 1 Laser radar unit 7 Laser beam 8 Front vehicle 14 Control unit 15 Inter-vehicle distance sensor

[Procedure amendment]

[Submission date] February 3, 1993

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FIG. 19 ─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] February 4, 1993

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[0009]

An inter-vehicle distance warning device according to the present invention
The inter-vehicle distance sensor that detects the inter-vehicle distance between the front vehicle and the host vehicle and the distance signal output from this inter-vehicle distance sensor that is equal to or less than the maximum detected distance are valid, and the effective distance signal value is the safe inter-vehicle distance. In an inter-vehicle distance alarm device having a controller that issues an alarm when the distance is smaller than the distance, the controller detects (1) a falling edge and a rising edge of a distance measurement data waveform, and raises the rising edge within a first predetermined time after the falling edge. If it is detected, it is determined to be noise, and if a fall or rise is detected within the second predetermined time after it is determined to be noise, it is estimated that the distance measurement object is an object other than the vehicle, and is estimated to be an object other than the vehicle. If a trailing edge or a trailing edge is detected within the third predetermined time, it is presumed that the object to be measured is an object other than the vehicle. If e has not detected the rising and range-finding object estimating means for estimating a distance measurement target and the vehicle,
(2) Means for changing the maximum detection distance according to the estimation result of the object to be measured.

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[0010]

The present invention was made by paying attention to the continuity of the distance measurement data waveform. The distance measurement data waveform falls when there is an object to be measured and rises when it disappears. The inter-vehicle distance signal is usually noise-removed by central filtering or the like, but if there is noise that cannot be completely removed, the width of the noise is narrow, so if it rises within the first predetermined time after the fall, noise will be generated. It can be determined that there is. If the measurement object is a vehicle, it is wider than noise, so after the fall, before the fourth predetermined time has elapsed.
If you do not stand up, you can presume that it is a vehicle. Also,
If no falling or rising is detected within the third predetermined time, it can be estimated as an object other than the vehicle in other cases. Therefore, when it is estimated that the vehicle is other than the vehicle, the maximum detection distance is set to be equal to or smaller than the current value to suppress the occurrence of false alarms. On the contrary, when the vehicle is estimated to be the vehicle, the maximum detection distance is set to be equal to or longer than the current one so that the alarm can be surely issued from the distance from the preceding vehicle.

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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
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 Accordingly, D <(Td + Tx) Vf + Vf 2 / 2α 1 -Va 2/2
When α ₂ ) = Ds (safe inter-vehicle distance), it is determined that the alarm is to be issued.

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In FIG. 19, in step S71, it is determined whether or not the inter-vehicle distance determination value, that is, the distance output of the inter-vehicle distance sensor is within the current maximum detection distance D _0. If YES, the process proceeds to next step S72. Then, it is determined whether or not the noise determination value N _f is 3. If N _f = 3, the result of estimation of the object to be measured is not a vehicle. Therefore, in step S73, the maximum detection distance D _{0 is set} to the distance measurement value (distance output value) D _t of the current inter-vehicle distance sensor or less. Change the setting to to suppress the occurrence of false alarms. If NO in step S72, there is a possibility of a vehicle, so the maximum detection distance D ₀ is held in step S74.

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If NO in the first step S71, that is, if the distance measurement value D _t exceeds the maximum detection distance D ₀ , it is determined in step S75 whether or not the noise determination value N _f is 1.
If N _f = 1 then the estimation result of the object to be measured is a vehicle, so in the next step S76 the maximum detection distance D ₀ is set back to the initial value, for example 100 m, and an alarm is issued reliably from the distance to the preceding vehicle. I will be able to serve you. NO in step S75
In the case of, there is a possibility other than the vehicle. Therefore, first in step S77, it is determined whether or not the current maximum detection distance D ₀ is the initial value. If YES, then in step S78 D ₀ =
Hold the initial value. If NO, step S
At 79, the maximum detection distance D ₀ is changed to the distance measurement value D _{f of} this time or a value less than this value to suppress the occurrence of false alarms.

Claims (1)

[Claims] 1. An inter-vehicle distance sensor for detecting an inter-vehicle distance between a front vehicle and an own vehicle, and a value equal to or less than a maximum detected distance is effective for a distance signal output from the inter-vehicle distance sensor, and an effective distance signal value is In an inter-vehicle distance warning device having a controller that issues an alarm when the distance is smaller than the safe inter-vehicle distance, the controller detects (1) a falling edge and a rising edge of a distance measurement data waveform,
If a rising edge is detected within the first predetermined time after the falling edge, it is determined to be noise, and if a falling edge or a rising edge is detected within the second predetermined time after it is determined to be noise, the distance measurement target is other than the vehicle. If the object is estimated to be an object other than the vehicle and a falling or rising edge is detected within the third predetermined time after that, it is estimated that the object to be measured is an object other than the vehicle. A distance-measuring-object estimating means for estimating the distance-measuring object as a vehicle when a rising edge is detected when the first predetermined time has elapsed after the falling edge, and (2) the maximum detection according to the estimation result of the distance-measuring object. An inter-vehicle distance warning device comprising means for changing the distance.