JPH1172561A - Alarming device for distance between vehicles - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable reducing miss-detection of the distance between vehicles and issuing an alarm for distance between vehicles in a proper timing. SOLUTION: The alarming device for distance between vehicles emits a laser beam 3 forward in a plurality of steps by shifting the angle in constant steps of angle in horizontal direction until it becomes a specific scanning angle, receives a reflected light 6 returning after reflecting at the preceding car 4, measures the distance vehicles D to the preceding car based on the time from the emission of the laser beam to the reception of the reflected light, and calculates the distance between vehicles to be alarmed Ds based on the car velocity and the relative velocity Vr. When the distance between vehicles D is closer than a switching judgment distance (Ds+5)m calculated from the relative velocity Vr, the step angle ϕ of the laser beam is switched to a smaller angle than usual and it is scanned. If the measured distance between vehicles D is smaller than the distance between vehicles Ds, an alarm for distance between vehicles is outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an inter-vehicle distance alarm device.

[0002]

2. Description of the Related Art Conventionally, a laser beam is emitted forward toward the front of a vehicle, and reflected light reflected from a reflector at the rear of a front vehicle that transmits the front of the vehicle is received.
The inter-vehicle distance to the preceding vehicle is calculated based on the time difference from the light transmission timing to the light receiving timing, and the relative speed with the preceding vehicle is also calculated based on the time change of the measured inter-vehicle distance. An inter-vehicle distance warning device that outputs an inter-vehicle distance warning when the actual inter-vehicle distance is shorter than the inter-vehicle distance set in relation to the above and alerts the driver is known.

In such a conventional inter-vehicle distance warning device,
In order to reliably detect the front vehicle and estimate the road shape such as curves, by scanning the laser beam narrowed down finely by a fixed step angle in the horizontal direction,
It is configured to detect an area of a certain size.

[0004]

However, such a conventional inter-vehicle distance warning device has the following problems. That is, depending on the distance between the vehicle and the preceding vehicle and the width of the reflector of the preceding vehicle, there is a situation where only one laser beam among a number of laser beams radiated at a step angle is applied to the reflector. May occur. In such a situation, if the laser beam deviates from the reflector of the preceding vehicle due to vibration or the like, distance detection fails, and data on the distance between the vehicle and the preceding vehicle cannot be obtained.

In order to compensate for such a situation, the inter-vehicle distance is constantly measured by averaging a plurality of measurement results, instead of measuring the inter-vehicle distance by only one measurement result. However, as a result, there is a problem that the calculation processing time becomes long, and particularly when the vehicle approaches the preceding vehicle at a large relative speed where a slight delay is important, the output timing of the inter-vehicle distance warning is slightly delayed. .

The present invention has been made in view of such a conventional problem. When the relative speed to the preceding vehicle is large, when the vehicle approaches the warning inter-vehicle distance calculated from the relative speed and the own vehicle speed, By making the step angle at the time of laser beam scanning smaller than usual, it is possible to reliably irradiate the reflector of the front vehicle and receive the reflected light, and reduce the number of measurements and shorten the calculation processing time Accordingly, it is an object of the present invention to provide an inter-vehicle distance warning device that can always output an accurate inter-vehicle distance warning timing.

[0007]

According to a first aspect of the present invention, there is provided an inter-vehicle distance warning device which transmits a laser beam in a plurality of steps toward a predetermined scan angle while shifting a predetermined step angle toward the front of the vehicle. A light transmitting means for transmitting light, a light receiving means for receiving a reflected light in which a laser beam transmitted by the light transmitting means is reflected by a target ahead and returning, and a light transmitting timing to a light receiving timing of the laser beam. An inter-vehicle distance measurement unit that measures an inter-vehicle distance to a target ahead based on a time difference, and a relative that calculates a relative speed between the inter-vehicle distance measured by the inter-vehicle distance measurement unit with time based on a time change of the inter-vehicle distance. Speed calculating means, an own-vehicle speed, and a warning inter-vehicle distance calculating means for calculating a warning inter-vehicle distance that requires the output of the following distance warning based on the relative speed calculated by the relative speed calculating means; An inter-vehicle distance warning determining unit that compares the inter-vehicle distance measured by the inter-vehicle distance measuring unit with the inter-vehicle distance calculated by the alarm inter-vehicle distance calculating unit to determine whether or not to output an inter-vehicle distance alarm; Step angle changing means for changing the magnitude of the step angle in the light transmission direction, the inter-vehicle distance measured by the inter-vehicle distance measurement means, the alarm inter-vehicle distance calculated by the alarm inter-vehicle distance calculation means, and the relative speed calculation means And a step angle change determining means for giving a command to switch the magnitude of the step angle in the light transmitting direction of the light transmitting means to the step angle changing means based on the calculated relative speed.

[0008] In the inter-vehicle distance warning device according to the first aspect of the present invention,
The laser beam is transmitted in a plurality of steps toward the front of the host vehicle until a predetermined scan angle is reached, while shifting the laser beam by a constant step angle, and the reflected light reflected from the target in front is returned, and the laser beam is received. The inter-vehicle distance to the target ahead is measured based on the time difference between the light transmission timing and the reflected light reception timing. Further, based on the time change of the measured inter-vehicle distance, the relative speed with respect to the target ahead is calculated, and based on the own vehicle speed and the calculated relative speed, the warning inter-vehicle distance that requires the output of the inter-vehicle distance warning is calculated. calculate.

The measured inter-vehicle distance is compared with the warning inter-vehicle distance to determine whether or not the inter-vehicle distance alarm output is required. When the inter-vehicle distance alarm output is required, an alarm command is output, and a warning sound or display informs the driver. Give inter-vehicle distance warning.

In addition to the necessity of the output of the inter-vehicle distance warning, the step angle change determining means determines that the measured inter-vehicle distance is shorter than the switching determination distance calculated from the warning inter-vehicle distance and the relative speed to the preceding vehicle. When the command is present, a command to switch the step angle of the laser beam sending direction is given to the step angle changing means, and the step angle changing means switches the step angle of the laser beam sending means in the sending direction and shifts by the designated step angle. While scanning.

In this case, it is necessary to pay particular attention to the inter-vehicle distance, and in a situation in which the vehicle is approaching the warning vehicle at a high relative vehicle speed to near the warning inter-vehicle distance, the reflector of the preceding vehicle can be surely scanned by one scan at a time. And the distance between vehicles can be measured, and the inter-vehicle distance can be reliably measured without performing the averaging process or by reducing the number of scans for the averaging process as compared with the related art.

According to a second aspect of the present invention, in the inter-vehicle distance warning device according to the first aspect, the step angle changing means receives a command for switching a step angle of the light transmitting direction of the light transmitting means from the step angle change determining means. Sometimes, the magnitude of the step angle is changed while maintaining the total number of steps of the light transmitting means. Thus, even if the scan step angle of the laser beam is changed, once each time The determination of the output of the inter-vehicle distance warning is performed without changing the time required for scanning of the vehicle and without changing the time required for measuring the inter-vehicle distance with respect to the preceding vehicle.

According to a third aspect of the present invention, in the inter-vehicle distance warning apparatus according to the second aspect, the step angle change determining means gives the step angle changing means a command to switch a step angle of a light transmitting direction of the light transmitting means. The processing interval changing means for shortening the judgment processing cycle of the inter-vehicle distance alarm output when the vehicle is in a situation where attention must be paid particularly to the inter-vehicle distance, i.e., at a high relative vehicle speed. In a situation where the vehicle is approaching the vehicle in the vicinity of the distance, the output determination of the inter-vehicle distance warning is performed in a shorter time by shortening the inter-vehicle distance measurement cycle.

According to a fourth aspect of the present invention, in the inter-vehicle distance warning device according to the first to third aspects, the step angle change judging means sets the inter-vehicle distance when the relative speed calculated by the relative speed calculating means is equal to or more than a predetermined value. When the inter-vehicle distance measured by the measuring means is equal to or more than a first threshold value and equal to or less than a second threshold value, a command to narrow the step angle is given to the step angle changing means.

According to a fourth aspect of the present invention, there is provided an inter-vehicle distance warning device.
If the inter-vehicle distance is relatively long, or if the relative speed is relatively small, measure the inter-vehicle distance under the same conditions as before,
When the inter-vehicle distance approaches the alarm inter-vehicle distance and the relative speed increases, the process that reduces the scan step angle is performed, so that one laser beam is applied to the reflector of the preceding vehicle in one scan and the reflected light is reflected. To obtain the correct inter-vehicle distance data without averaging, or by averaging with fewer scans than before, An inter-vehicle distance warning is output at the correct timing.

[0016]

According to the first aspect of the present invention, in a situation in which attention must be paid to the inter-vehicle distance, that is, in a situation in which the vehicle is approaching the preceding vehicle up to the alarm inter-vehicle distance at a high relative vehicle speed, the vehicle may be operated once. The inter-vehicle distance can be reliably measured by capturing the reflector of the preceding vehicle with one scan, and the inter-vehicle distance can be reliably measured without performing the averaging process or by reducing the number of scans for the averaging process as compared with the related art.

According to the second aspect of the present invention, even if the scan step angle of the laser beam is changed, the time required for one scan at a time does not change, and the time required for measuring the inter-vehicle distance to the preceding vehicle does not change. In addition, the output determination of the inter-vehicle distance warning can be reliably performed by measuring the inter-vehicle distance once.

According to the third aspect of the present invention, especially in a situation where attention must be paid to the inter-vehicle distance, that is, in a situation in which the vehicle is approaching the preceding vehicle at a high relative vehicle speed and near the warning inter-vehicle distance, the inter-vehicle distance measurement cycle Makes it possible to determine the output of the following distance warning in a shorter time.

According to the fourth aspect of the present invention, when the inter-vehicle distance is long to some extent or when the relative speed is relatively small, the inter-vehicle distance is measured under the same conditions as in the past, and the inter-vehicle distance approaches the warning inter-vehicle distance. Also, when the relative speed is increased, by performing a process of reducing the scan step angle, a plurality of laser beams are applied to the reflector of the preceding vehicle in one scan so that the reflected light can be received,
The distance between vehicles is reliably measured for each scan, and the correct distance data is obtained without averaging or by averaging the number of scans less than before. An alarm can be output.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. As shown in FIG. 1, the inter-vehicle distance warning device of the present invention emits a laser beam 3 forward by a laser radar system 2 mounted on the front of a vehicle 1. When the front vehicle 4 is located at a distance D in front of the own vehicle 1, the laser beam 3 is reflected by the reflector 5 mounted on the rear of the front vehicle 4, and the reflected light 6 returns to the laser radar system 2. come. This is detected by the laser radar system 2, and the inter-vehicle distance D to the preceding vehicle 4 is calculated from the time difference t from the timing of emitting the laser beam 3 to the timing of receiving the reflected light 6 based on the following equation.

[0021]

D = (c × t) / 2 where c is the speed of light.

The laser radar system 2 has the configuration shown in FIG. The laser radar system 2 includes a control arithmetic processing circuit (comprising an MPU) 7, a laser light emitting diode (LED) 8, a light transmitting lens 9 for converging light emitted by the LED 8, and a mirror 10 for changing the light direction. A light-transmitting scan mirror 11 for emitting the laser beam 3 forward; a light-receiving scan mirror 12 integrated with the light-transmitting scan mirror 11 for receiving reflected light 6 from the front; Stepping motor 13 that can be stopped, and scan mirrors 11 and 12
, The scanning mirror 12 for receiving light
And a photodiode (PD) 16 for converging the reflected light 6 received by the light emitting device.

The control arithmetic processing circuit 7 outputs a drive signal for the LED 8 in response to an on / off signal from an ignition switch or the like, and the LED 8 emits light. After passing through the light transmitting lens 9, this light is reflected by the mirror 10 and the light transmitting scan mirror 11 and emitted forward as a pulsed laser beam 3. The control arithmetic processing circuit 7
The stepping motor 13 is synchronized with the drive signal of the ED 8.
, And the stepping motor 13 rotates by a predetermined step angle φ, and sends the scanning mirror 11 for transmitting light and the scanning mirror 1 for receiving light via the stay 14.
Move 2 As a result, the laser beam 3 scans forward while shifting in the horizontal direction by the step angle φ.

The laser beam 3 radiated forward is reflected when it hits the reflector 5 at the rear of the front vehicle 4 if present, and returns as reflected light 6. After being reflected, the light receiving lens 1
The light is condensed at 5 and detected at PD 16. Then, the control arithmetic processing circuit 7 detects a time difference t between the output timing of the drive signal to the LED 8 and the light receiving timing by the PD 16, and calculates the inter-vehicle distance D to the front vehicle 4 by the above equation (1).

When the inter-vehicle distance D is calculated in this manner,
The control arithmetic processing circuit 7 outputs the inter-vehicle distance D to a display device (not shown) for display. Also, the control operation processing circuit 7
Calculates the inter-vehicle distance change per unit time based on the inter-vehicle distance data measured at the time of the previous scan and the current inter-vehicle distance data as a relative speed Vr with respect to the preceding vehicle, and obtains a value from a vehicle speed sensor (not shown). Based on the given vehicle speed Vf and the relative speed Vr, a warning inter-vehicle distance Ds, which is a distance for warning a driver that the vehicle is approaching the front vehicle 4, is calculated based on the following equation (2). Then, the measured inter-vehicle distance D
And a warning inter-vehicle distance Ds. If D = Ds, a warning signal is transmitted to a display device or a buzzer (not shown). When the display device or the buzzer receives the inter-vehicle distance warning command, the display device or the buzzer warns the driver that the vehicle is approaching the preceding vehicle by blinking the display or warning sound.

The following formula 2 can be used as a calculation formula for calculating the warning inter-vehicle distance Ds.

[0027]

(Equation 2) Here, Ts is a margin time in consideration of a stepping change of a pedal, Vf is a vehicle speed, Vr is a relative speed, and α is a deceleration.

In equation (2), Ts = 1 second, α = 0.3G
(= Approximately 3 m / sq. Second), the warning inter-vehicle distance Ds
Is calculated as shown in FIG. For example, the vehicle speed V
When approaching at f = 100 km / h and relative speed Vr = 30 km / h, an inter-vehicle distance warning is output when the inter-vehicle distance D to the preceding vehicle becomes approximately 40 m.

The laser beam 3 is scanned while being shifted in the horizontal direction by a step angle φ.
As shown in the figure, the scan area 17 of the laser beam can be indicated by a scan angle θ centered on the laser radar system 2. The scan angle θ is determined by the step angle φ and the number of steps n. For example, if φ = 0.15 degrees and n = 80 steps, the scan angle θ = 12 degrees.

The length L of the arc corresponding to one step angle φ depends on the distance D from the laser radar system 2 and is obtained by the following equation (3).

[0031]

(Equation 3) FIG. 5 shows the result obtained by calculation of the arc size L in the case where the step angle φ is 0.15 degrees according to Expression 3. One step angle φ with increasing distance D
Is linearly increased. For example,
Own vehicle speed Vf = 100 km / h, relative speed Vr = 30 km
The arc size L at a distance of 40 m which is the warning inter-vehicle distance Ds at / h is about 10 cm. This indicates that if the width w of the reflector 5 of the front vehicle 4 is 10 cm or less, only one laser beam may hit the reflector 5 out of the 80 laser beams. That is, in the worst case, the distance data obtained by the reflection of the reflector 5 has only one data. In such a situation, if the vehicle vibrates due to the unevenness of the road surface, depending on the case, one scan may cause the front vehicle 4
May not be detected.

In order to avoid the above problem and always measure the inter-vehicle distance, a method of increasing the number of times of measurement and averaging a plurality of inter-vehicle distance data to compensate for a detection error has conventionally been adopted. However, when such a detection error occurs, the actual inter-vehicle distance at that time is not measured, and the current inter-vehicle distance is calculated by estimating the inter-vehicle distance up to the previous time. If such detection mistakes overlap at the moment when the relative speed suddenly increases, such as immediately after applying, it is expected that the actual inter-vehicle distance and the estimated inter-vehicle distance will greatly deviate, so it is necessary to wait until the next scan timing It is conceivable that an accurate inter-vehicle distance cannot be obtained, and the inter-vehicle distance becomes even closer during that time. Therefore, it is desirable to reduce the occurrence of detection errors and to reduce the processing time of the following distance and the relative speed in order to output the following distance warning at an appropriate timing.

To reduce detection errors, the step angle φ
And the number of laser beams hitting the reflector 5 of the front vehicle 4 may be increased. However, if the scan angle θ is kept normal and the step angle φ is reduced,
The number of steps n increases, and the time required for one scan increases. Further, if the number of steps n is kept normal and the step angle φ is made smaller, the scan angle θ becomes narrower, which affects the estimation of the curve shape of the road.

Therefore, in the present invention, when the inter-vehicle distance is relatively long and the relative speed is relatively small, the inter-vehicle distance is measured under the same conditions as in the past, and the inter-vehicle distance approaches the warning inter-vehicle distance, and the relative speed is reduced. When it becomes larger, a process for reducing the step angle φ is performed to solve these problems, and a plurality of laser beams are transmitted by one scan to the front vehicle 4.
To allow the reflected light to be received by the reflector 5 to reliably measure the inter-vehicle distance for each one-time scan, and to perform the averaging without the averaging process or the averaging of the number of scans less than in the past. Thus, correct inter-vehicle distance data can be obtained by the conversion process, and an inter-vehicle distance alarm can be output at an appropriate timing.

FIGS. 6A to 6D show the relationship between the inter-vehicle distance D to the front vehicle 4 and the scan angle θ in the inter-vehicle distance warning device of the present invention. First, FIG. 1A shows a state in which no vehicle exists in front of the host vehicle 1. In this state, a step angle φ = 0.
Scan is performed at 15 degrees with the number of steps n = 80. Therefore, the scan angle θ1 = 12 degrees.

Next, FIG. 2B shows that the own vehicle 1 has a speed of 100 km / km.
h and running at 70 km / h (relative speed 30 km / h
h) shows a state in which the vehicle is approaching the front vehicle 4 traveling. In this state, the front vehicle 4 is detected farther than the warning inter-vehicle distance Ds (for example, D1 = 80 m). At this time, the scan angle θ1 is 12 degrees as in the case of FIG. The reflector width w of the front vehicle 4 is 10c.
Assume m. In this case, a situation may occur where inter-vehicle distance data cannot be selected in one scan. Therefore, inter-vehicle distance measurement is performed a plurality of times and averaging processing is performed. For example, 1
Assuming that each scan takes 0.15 seconds and the number of measurements (scans) is four, the arithmetic processing time is 0.6 seconds.

Next, as shown in FIG.
While approaching the front vehicle 4 while maintaining 0 km / h and the relative speed of 30 km / h, the following distance D2 becomes the warning following distance Ds.
When the distance becomes 45 m, which is slightly larger than (= 40 m), the step angle φ is changed to a narrower angle, 0.05 degrees. However, the number of steps n in one scan is the same as normal, ie, 8
Keep at zero. As a result, the scan angle θ2 becomes 4 degrees.

In this case, the step angle φ is 1/3 of the normal
And the size L of the arc corresponding to one step is about 4 cm at a distance of 45 m. This length of L = 4 cm is less than half of the width w = 10 cm of the reflector 5 of the front wheel 4, so that at least two laser beams can be applied to the reflector 5 in one scan. As a result, even if the detection of one laser beam fails due to vibration or the like, the distance can be detected with at least one remaining laser beam. Therefore, in this embodiment, while maintaining the number of steps n = 80, the step angle φ is set to 0.05 degrees and the number of scans is reduced to two, so that the calculation processing time including the averaging processing is reduced to zero. 3 seconds.

Further, as shown in FIG. 4D, when the distance D3 becomes closer to or less than the warning distance Ds when the vehicle approaches the preceding vehicle 4 further, a warning command is output, and a warning sound or display is used to issue a warning between the vehicles. Output to warn the driver that they are too close to the vehicle in front.

The inter-vehicle distance warning causes the driver to loosen the accelerator or depress the brake pedal to increase the inter-vehicle distance. When the inter-vehicle distance D becomes longer than the warning inter-vehicle distance Ds, the inter-vehicle distance warning is stopped.

The timing for returning the step angle φ to the normal state is as follows: when the relative speed Vr is reduced to a predetermined value or less, when the inter-vehicle distance is reduced to such an extent that a plurality of lasers hit the reflector 5 of the front vehicle 4, Alternatively, the inter-vehicle distance D is equal to the aforementioned step angle switching distance (Ds + 5 in the present embodiment).
m) Set the time when it spreads out.

FIG. 7 shows an example in which the magnitude of the step angle φ is classified according to the combination of the inter-vehicle distance D and the relative speed Vr. When the relative speed Vr is small, there is no fear of sudden approach, so regardless of the size of the following distance D,
Always maintain the normal step angle φ = 0.15 degrees. When the relative speed Vr is large and there is a possibility of suddenly approaching the preceding vehicle 4, the inter-vehicle distance D is set to the alarm inter-vehicle distance Ds + 5m.
When the distance is larger than the normal step angle φ = 0.15 degrees, the inter-vehicle distance from the warning inter-vehicle distance Ds + 5 m to 20 m is switched to a step angle φ = 0.05 degree, which is finer than usual, and the inter-vehicle distance is further reduced. , 20
m, the normal step angle φ is returned to 0.15 degrees again. The reason for returning to the step angle φ = 0.15 degrees when the final inter-vehicle distance D becomes 20 m or less is that when the inter-vehicle distance is small, a plurality of laser beams can be applied to the reflector 5 of the front vehicle 4 even at a normal step angle. Because you can.

The condition of the inter-vehicle distance D changes depending on what is used in the formula for calculating the warning inter-vehicle distance Ds, how much the minimum value of the width w of the reflector 5 is assumed, and the like. The formula for calculating the warning inter-vehicle distance Ds is expressed by Equation 2, and it is assumed that the minimum value of the reflector width w is 10 cm. The inter-vehicle distance at which the step angle φ is changed is determined by adding 5 m as a margin to the warning inter-vehicle distance Ds. While this margin amount is almost the same as detecting the front vehicle 4 while the step angle φ is small, it is desirable to make the margin as short as possible in consideration of the influence on the road curve estimation performance and the like. In order not to delay the alarm timing, it is necessary to set the size to a certain level, and it is determined experimentally and empirically in consideration of these factors.

As a basis for determining the condition of the relative speed Vr, the calculation processing time in a normal state is considered. That is, when it is assumed that the step angle is not changed, the determination is made in consideration of the actual reduction in the inter-vehicle distance caused by the delay of the arithmetic processing time. For example, when the calculation processing time is 0.6 seconds as described above, the relative speed Vr = 20 k
At m / h, the inter-vehicle distance to the front vehicle 4 is reduced by about 3.3 m during this 0.6 second.

That is, there is a possibility that the warning is delayed by up to 0.6 seconds from the output timing of the optimum inter-vehicle distance warning,
In this case, the warning inter-vehicle distance Ds at the time when the warning is output
It is closer to the vehicle 3.3 m ahead than the vehicle.

Normally, since the warning inter-vehicle distance Ds is set with some allowance, the delay of the alarm output of 3.3 m does not cause a problem in driving, but here, as an example, the relative speed is set. Vr ≧ 20 km / h was determined when the relative speed was large.

The operation of the inter-vehicle distance alarm device of the present embodiment described above is as shown in the flowchart of FIG. When the apparatus is started when the power is turned on, the step angle φ = 0.15 degrees and the number of steps n = 80 are set as the initial settings, and thus the scan angle θ is set to 12 degrees. The averaging process is set (step S1). The inter-vehicle distance measurement is periodically repeated in this initial setting. First, the inter-vehicle distance D is measured (step S2), and the relative speed is calculated based on the change per unit time between the previous inter-vehicle distance measurement value and the current inter-vehicle distance measurement value. Vr
Is also calculated (step S3). Further, the own vehicle speed Vf is input, and the warning distance Ds is calculated by the calculation of Expression 2 based on the relative speed Vr and the own vehicle speed Vf (step S).
4).

Thereafter, it is determined whether or not the relative speed Vr is equal to or higher than 20 km / h (step S5). If it is determined that the vehicle is approaching rapidly, the inter-vehicle distance D becomes 20m ≦ D ≦ Ds + 5m.
(Step S6), and if it is in this range, the step angle φ is changed to 0.05 degrees, which is a smaller angle than usual, and the distance measurement results of two scans are averaged. To obtain the inter-vehicle distance D, and thereafter, repeat the inter-vehicle distance measurement (step S
7).

As described above, according to the inter-vehicle distance warning device of the above-described embodiment, when the relative speed with the preceding vehicle is large, the vehicle approaches to the vicinity of the warning inter-vehicle distance calculated from the relative speed and the own vehicle speed. In addition, by setting the step angle when scanning with a laser beam finer than usual, and shortening the calculation processing time, the inter-vehicle distance at the appropriate timing without greatly affecting the road curve shape estimation performance etc. An alarm can be output.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an inter-vehicle distance warning operation according to one embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a mechanical configuration of the embodiment.

FIG. 3 is a graph showing a relationship between the own vehicle speed and a warning inter-vehicle distance used in the embodiment.

FIG. 4 is an explanatory diagram showing a scan angle and a scan area of the laser radar system in the embodiment.

FIG. 5 is a graph showing a relationship between an arc size and a distance corresponding to one step angle of a laser beam in the embodiment.

FIG. 6 is an explanatory diagram showing an operation of the embodiment.

FIG. 7 is a table showing a switching standard of a step angle of a laser beam depending on a relative speed and an inter-vehicle distance adopted in the embodiment.

FIG. 8 is a flowchart of a step angle switching operation of the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Own vehicle 2 Laser radar system 3 Laser beam 4 Front vehicle 5 Reflector 6 Reflected light 7 Control arithmetic processing circuit 8 Laser light emitting diode 16 Photodiode

Claims (4)

[Claims] 1. A light transmitting means for transmitting a laser beam in a plurality of steps toward a predetermined scan angle while shifting the laser beam by a predetermined step angle toward the front of the vehicle, and a laser transmitted by the light transmitting means. A light-receiving means for receiving reflected light whose beam is reflected back to a target in front of the vehicle, and an inter-vehicle for measuring an inter-vehicle distance to a target in front based on a time difference from a transmission timing of the laser beam to a reception timing of the laser beam. Distance measuring means, relative speed calculating means for calculating a relative speed with respect to the target ahead based on a time change of the inter-vehicle distance measured by the inter-vehicle distance measuring means, calculation of the own vehicle speed, and the relative speed calculating means An inter-vehicle distance calculating unit that calculates an inter-vehicle distance that requires the output of an inter-vehicle distance alarm based on the relative speed to be calculated, and the inter-vehicle distance measured by the inter-vehicle distance measurement unit; Comparing the alarm vehicle distance calculated for broadcast vehicle distance calculating means,
An inter-vehicle distance alarm determination unit that determines whether or not an inter-vehicle distance alarm output is required; a step angle changing unit that changes a magnitude of a step angle in a light transmission direction of the light transmitting unit; and an inter-vehicle distance measured by the inter-vehicle distance measurement unit. And issuing a command to switch the magnitude of the step angle in the light transmitting direction of the light transmitting means based on the warning inter-vehicle distance calculated by the warning inter-vehicle distance calculating means and the relative speed calculated by the relative speed calculating means. An inter-vehicle distance alarm device comprising: a step angle change determining means provided to the angle changing means. 2. The step angle changing means holds the total number of steps of the light transmitting means when receiving a command to switch a step angle of a light transmitting direction of the light transmitting means from the step angle change determining means. 2. The inter-vehicle distance alarm device according to claim 1, wherein the magnitude of the step angle is changed as it is. 3. When the step angle change determining means gives a command to switch the step angle of the light transmitting direction of the light transmitting means to the step angle changing means, the determination processing cycle of the inter-vehicle distance warning output is shortened. 3. The inter-vehicle distance alarm device according to claim 2, further comprising an arithmetic processing cycle changing unit. 4. The inter-vehicle distance measured by the inter-vehicle distance measuring means is a first value when the relative speed calculated by the relative speed calculating means is equal to or greater than a predetermined value.
The inter-vehicle distance warning according to any one of claims 1 to 3, wherein a command to narrow the step angle is given to the step angle changing means when the distance is equal to or more than a threshold value and equal to or less than a second threshold value. apparatus.