JPH06265637A - Vehicle mounted apparatus for measuring distance between cars - Google Patents

Abstract

PURPOSE:To detect the distance between cars efficiently by certainly identifying a preceding vehicle from another substance. CONSTITUTION:The distance data of a plurality of reflecting substances are inputted into an operating circuit 20 from an optical laser radar 10, which is scanned with a scanning device 22. In the operating circuit 20, the moving speed and the mutual interval of each reflecting substance are operated. A plurality of the reflecting substances, which have the approximately equal distances from own vehicle and approximately equal moving speed and have the mutual interval in the specified range, are judged that the substances belong to the same vehicle. The data are outputted into an alarm judging circuit 24. In the alarm judging circuit 24, the data are compared with the safe distance between the cars, which is computed based on the signal of a vehicle speed sensor 23. The alarm signal is outputted into an alarm device 25. Thus, the preceding vehicle is readily identified, the reliability of the obtained distance between the cars becomes high and the adequate alarming is performed.

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 measuring device for a vehicle, which uses a radar to determine the distance between the vehicle and another vehicle.

[0002]

2. Description of the Related Art A conventional vehicle-to-vehicle distance measuring device of this type is disclosed in, for example, Japanese Patent Laid-Open No. 58-203524.
In order to always maintain a safe inter-vehicle distance and ensure safe travel, an optical laser radar device is attached to a vehicle to detect the inter-vehicle distance between a preceding vehicle traveling ahead and the host vehicle. An optical laser scanning method for using the optical laser radar device mounted on a vehicle with high detection performance is disclosed in, for example, Japanese Patent Application Laid-Open No. 50-134589.

In this scanning method, a flat laser beam that spreads in the vertical direction is scanned in a predetermined search region θ in front of the vehicle at a predetermined cycle, and when a reflected pulse from the preceding vehicle is received, a fixed time has elapsed thereafter. By the way, the scanning direction of the laser beam is reversed. As a result, the actual scanning angle of the laser beam is narrowed, and the laser beam is scanned only in the vicinity of the preceding vehicle that has reflected the laser beam, thereby attempting to perform highly efficient inter-vehicle distance measurement with less wasted scanning time. It is a thing.

[0004]

However, on the road ahead of the vehicle, in addition to the preceding vehicle, there are many various objects such as roadside guardrails and traffic signs. Therefore, in the optical laser radar device by the scanning method as described above, while it is expected that the inter-vehicle distance can be detected in a short time, on the other hand, the reflection pulse from the object other than the preceding vehicle is changed to the reflection pulse from the target preceding vehicle. There is a risk of accidentally detecting it. When such an erroneous detection occurs, the laser beam will be scanned only near the object after that, and an erroneous measurement result with the obtained distance as the inter-vehicle distance to the preceding vehicle is output. There is a problem that becomes. Therefore, in view of the above-mentioned conventional problems, the present invention provides a vehicle-to-vehicle distance measuring apparatus capable of efficiently detecting and measuring the following distance from a preceding vehicle from another object. To aim.

[0005]

Therefore, the present invention is based on FIG.
As shown in FIG. 3, position detecting means 1 for transmitting electromagnetic waves, inputting the reflected waves to detect a plurality of reflecting objects at different positions with respect to the own vehicle, and outputting position data thereof, and a plurality of reflecting objects. A speed calculation means 2 for calculating each moving speed, a distance calculation means 3 for calculating a distance between the plurality of reflecting objects based on the position data, and a distance from the own vehicle among the plurality of reflecting objects are substantially equal to each other. Preceding vehicle discrimination means 4 for discriminating a preceding vehicle from reflecting objects having the same moving speed and substantially the same moving speed and having a distance between them in a predetermined range, and a distance from the position data of the reflecting object discriminated as the preceding vehicle. The output means 5 for outputting information is provided.

[0006]

The position detecting means 1 detects a plurality of reflecting objects from a plurality of reflected waves. Among these, those moving at a substantially equal distance and a constant speed with respect to the own vehicle and having a predetermined distance between the reflecting objects are discriminated and extracted by the preceding vehicle discrimination means 4 as belonging to the same vehicle. This allows the preceding vehicle to be easily identified and detected.

[0007]

FIG. 2 is a block diagram showing the configuration of an embodiment of the present invention. The optical laser radar device 10 is connected to an arithmetic circuit 20 that receives the output, and the arithmetic circuit 20 is connected to a scanning device 22 that controls scanning of the optical laser radar device 10 via a D / A converter 21. Also, the vehicle speed sensor 2
3 is connected to the arithmetic circuit 20. An alarm determination circuit 24 including an alarm device 25 is connected to the arithmetic circuit 20, and a signal from the vehicle speed sensor 23 is also input to the alarm determination circuit 24. The optical laser radar device 10 includes a clock generator 1
1, a light transmitter 12, a light receiver 13, an amplifier 14, and a distance detection circuit 15.

In the optical laser radar device 10, the clock generator 11 generates a clock signal at a constant time interval, and the light transmitter 12 is driven in synchronization with this clock signal to spread in the up and down direction. The laser light Lt is emitted toward the front of the vehicle. The reflected light Lr reflected by the emitted laser light hitting a reflecting object such as a preceding vehicle is
The light is received by the light receiver 13 having the light-receiving viewing angle Q ′, converted into an electric signal, amplified by the amplifier 14, and then the distance detection circuit 15
Is supplied to.

A clock signal is further input from the clock generator 11 to the distance detection circuit 15, and the distance detection circuit 15 starts from the time when this clock signal is input.
The distance S to the reflecting object is calculated by the following equation based on the optical propagation delay time Td up to the time point when the reflected photoelectric signal is input from the light receiver 13 via the amplifier 14. S = C × Td / 2 Here, C is the speed of light (3 × 10 ⁸ m / sec).

The arithmetic circuit 20 is not shown in detail, but is C
It is composed of a PU, a ROM, a RAM, an input / output interface, etc., and arithmetic processing is performed by a program stored in the ROM. The arithmetic circuit 20 outputs a scanning angle control signal as a digital signal for scanning the laser light emitted from the light transmitter 12 in the horizontal direction in the search area in front of the vehicle while changing the irradiation angle θ. This scanning angle control signal is converted into an analog signal via the D / A converter 21 and input to the scanning device 22.

The scanning device 22 controls and drives the light transmitter 12 in the range of the angle Q based on the scanning angle control signal from the arithmetic circuit 20. The angle Q of the search area is set between the swing angle θL to the left and θR to the right with respect to the longitudinal centerline of the vehicle. Therefore, the scanning angle of the light transmitter 12 is within the range of (-θL to θR). The light receiving viewing angle Q ′ of the light receiver 13 in the optical laser radar device is set to be the same as or slightly larger than the angle Q of the search area. A clock signal is input from the clock generator 11 of the optical laser radar device to the arithmetic circuit 20, and the timing of this scanning control is matched with the timing of the optical laser radar device 10.

3 and 4 are flowcharts showing the flow of processing in the arithmetic circuit 20 and the alarm judgment circuit 24. First, in step 101, a laser beam scanning angle is initialized. Here, the irradiation angle θ at the starting point is −θL (left end), the unit increase angle Δθ in scanning is + 0.1 °, and the maximum swing angle θB
Is set to θR (right end). As a result, the irradiation of the laser beam is started from the −θL direction, is oscillated while increasing by 0.1 °, and is scanned up to θR.

In the next step 102, the presence or absence of reflected light is confirmed. When there is a reflected light signal,
In steps 103 and 104, the distance obtained by the distance detection circuit 25 is input and stored in the RAM in the arithmetic circuit together with the irradiation angle, and the counter k is counted up, and then the routine proceeds to step 105. Also, step 102
If there is no reflected light signal, the process directly proceeds to step 105.

In step 105, the irradiation angle θ is θB (=
θR) is reached, and if it has not been reached yet, in step 113, the value of the irradiation angle θ is changed to Δθ.
(= 0.1 °) incrementing step 102
~ 104 are repeated. When θ = θB in the check in step 105, the process proceeds to step 106 and Δ
The sign of θ is checked. If Δθ is positive, step 1
07, and when Δθ is negative, the routine proceeds to step 108, where the Δθ and θB target values are inverted.
That is, in step 107, θB = θL, Δθ = −
Reset to 0.1 °, and in step 108, θB = θ
R, Δθ = + 0.1 ° is set.

After the inversion, in step 109, the value of the counter k is set to the total number of signals Nk, and the counter k is returned to the initial value. Next, at step 110, the vehicle speed is read from the vehicle speed sensor, and at step 111, the counter n is counted up. This counter n counts the number of scans in which one scan extends from one end to the other end of the scanning range. The value of the counter n is checked in step 112, and while n is 5 or less, the process returns to step 102 via step 113 and the above flow is repeated.

When the number of scans becomes larger than 5, the routine proceeds to step 114, n is cleared, and at step 115, counting up of the counter k is restarted. In step 116, the optical laser radar device 1
The position Pk (L, θ) of the reflecting object with respect to the own vehicle is sequentially extracted based on the data input from 0 and stored in the RAM, and in step 117, the velocity Vk of the reflecting object is calculated by the correction based on the own vehicle speed. To be done. Steps 101 to 1
16 constitutes the position detecting means of the invention, and step 117 constitutes the speed calculating means.

In the next step 118, the distance of the k-th reflecting object calculated this time and k-1 obtained last time are calculated.
From the distance of the th reflective object, its distance difference ΔL (= Lk −
Lk-1) is calculated, and in step 119, this ΔL is compared with a predetermined value LB1 set to a value close to zero.
If ΔL is LB1 or less, proceed to step 120,
Distances ΔPk, Pk−1 between the two objects are calculated and compared with a predetermined value LB2 in step 121. Predetermined value LB2
Is for determining whether or not it is within the range corresponding to the lateral width of the vehicle. For example, a reflector interval provided at the rear of the vehicle may be used, and is usually set within a range of about 1.3 to 1.5 m. Good. Step 120 constitutes the interval calculating means of the invention.

When .DELTA.Pk and Pk-1 are LB2 or less, the routine proceeds to 122, where the velocity difference .DELTA.V between the two objects is calculated by (Vk-Vk-1) using the velocity of the reflecting object. Then, in step 123, it is checked whether ΔV is larger or smaller than the predetermined value VB. The predetermined value VB is also set to a value close to zero, which is considered to be an error range. When ΔV is VB or less, in step 124, the two objects belong to the same vehicle, and Pk and Pk-1 are output to the alarm determination circuit as preceding vehicle data. Of the above, steps 118 to 119, 121, 122 to 123 constitute the preceding vehicle determination means of the invention, and step 124 constitutes the output means.

Then, in the warning judgment circuit 24, the safe inter-vehicle distance Ls is calculated in step 125 based on the own vehicle speed, and in step 126, the reflecting object, that is, the distance Lk to the preceding vehicle here is compared with Ls. . Lk is L
When it is smaller than s, the routine proceeds to step 127, where the warning judgment circuit outputs a warning command to the warning device 25. Also,
If Lk is greater than or equal to Ls, then step 12 is directly executed.
Go to 8. If ΔL> LB1 in step 119, ΔPk, Pk−1> LB2 in step 121, and ΔV> VB in step 123, the process also goes to step 128.

In step 128, the value of k is checked and step 1 is repeated until the total number of input signals Nk is reached.
The flow after 15 is repeated. When k reaches Nk, the process returns to step 101, a new scan is performed, and new data is fetched.

This embodiment is configured as described above, and in the optical laser radar device, the reflected light from a plurality of reflecting objects with respect to the transmitted laser light is received, and by using this, it is approximately equidistant to the host vehicle. By determining that vehicles moving at a speed and having a predetermined distance between the reflective objects belong to the same vehicle, the preceding vehicle is easily identified and detected. With this, the reliability of the obtained inter-vehicle distance is high,
Appropriate alerts will be given.

FIG. 5 is a block diagram showing the configuration of the second embodiment. In this embodiment, the reflector of the vehicle is reliably caught as a reflecting object by the intensity of the reflected light signal. A raindrop detection sensor 30 is connected to the arithmetic circuit 20 'together with the vehicle speed sensor 23. Thus, when the intensity of the reflected light signal changes due to the running environment such as rainy weather, the reference level for identifying the presence of the reflected light from the reflecting object, particularly the reflector of the vehicle, is changed in accordance with the environment. The other structure is the same as that of the previous embodiment shown in FIG.

The flow of processing in the arithmetic circuit 20 'and the alarm judgment circuit is shown in the flow charts of FIGS. Here, step 201 is provided between steps 101 and 102, and the signal from the raindrop detection sensor 30 is input as an environmental coefficient, and the object detection level in the subsequent stage is adjusted based on this. Thus, for example, when a signal indicating rainy weather is input, the object detection level is shifted to a lower direction. Further, a step 202 is provided between the steps 102 and 103, and among the input signals from the optical laser radar device, only those which satisfy the object detection level adjusted in the above step 201 are selected, and the inter-vehicle distance information is obtained. To be extracted. The object detection level is set to a value at which the reflected light from the reflector of the vehicle is reliably detected.
The rest of the flow is the same as in FIG.

According to this embodiment, the raindrop detection sensor is used to adjust the object detection level with respect to the reflected light signal intensity so that the reflected light from the vehicle reflector can be detected stably regardless of the weather condition. Therefore, the accuracy of detecting the preceding vehicle as a reflecting object is further improved.

FIG. 8 is a block diagram showing the configuration of the third embodiment. In this embodiment, the distance to the preceding vehicle is accurately grasped along the curve even while traveling on a curved road. That is, in addition to the vehicle speed sensor, the steering angle sensor 31 is connected to the arithmetic circuit 20 ″, and when traveling on a curved road, the arithmetic circuit 20 ″ calculates the radius of curvature of the curve from the speed and the steering angle of the host vehicle. The distance to the vehicle is corrected to a value that follows the curve.
The other structure is the same as that of the embodiment shown in FIG.

The flow of processing in the arithmetic circuit 20 "and the alarm judgment circuit is shown in the flow charts of FIGS. 9 and 10. Here, step 301 is provided after step 114, and the steering angle .lambda. Is read, and the next step 302
At, the radius of curvature R of the traveling road curve is calculated based on the yaw rate and the vehicle speed previously read.

Here, the yaw rate r is r = V1 * λ / {W *, where N is the steering gear ratio of the host vehicle, W is the wheel base, Ks is the stability factor as a vehicle characteristic, and V1 is the host vehicle speed. It is calculated by (1 + Ks * V1) * N}. Therefore, the radius of curvature is R = V1 / r = W * (1 + Ks * V1) * N / .lambda.

After this, the process proceeds to step 115 and subsequent steps, and if it is determined by the speed difference check in step 123 that a plurality of objects belong to the same vehicle, step 303
Proceed to. In step 303, it is checked whether the reflecting objects determined to belong to the same vehicle are located on the curve having the radius of curvature R obtained above. If the reflective object is located on the above curve,
In step 304, the distance Lk to the reflecting object is corrected, and the distance LC along the curve of the radius of curvature R is calculated.

That is, as shown in FIG. 11, when the vehicle A and the reflecting object B are on a curve with a radius of curvature R, the measured straight line distance Lk and the included angle α between them are: Lk = 2R * Since there is a relationship of sin (α / 2), the distance LC along the curve based on this
Is calculated as LC = α * R. Similarly, the speed V2 of the reflecting object along the curve or the relative speed V2-V1 with respect to the host vehicle traveling at the speed V1 is also obtained. After this, instead of step 124 in FIG.
These data including the above are output to the warning determination circuit 24 as vehicle data. When the reflecting object is not located on the curve with the radius of curvature R in the check in step 303,
Go to step 128. The rest of the flow is the same as in FIG.

According to this embodiment, since the radius of curvature of the curve of the traveling road is obtained by using the steering angle sensor and the distance to the preceding vehicle is corrected to a value along the curve, regardless of the change of the traveling road. This has the effect of always obtaining an accurate inter-vehicle distance without error.

[0031]

As described above, according to the present invention, a plurality of reflecting objects are detected by a so-called radar device that detects electromagnetic waves by transmitting the electromagnetic waves and inputting the reflected waves to detect the reflecting objects. Almost equal, moving speeds are almost equal,
In addition, since it is determined that a plurality of reflecting objects having an interval between each other within a predetermined range belong to the same vehicle and output the data as the data regarding the preceding vehicle, the preceding vehicle is easily identified and This has the effect of improving the reliability of distance measurement.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of the present invention.

FIG. 2 is a block diagram showing a configuration of a first exemplary embodiment of the invention.

FIG. 3 is a flowchart showing a flow of processing in the first embodiment.

FIG. 4 is a flowchart showing a processing flow in the first embodiment.

FIG. 5 is a block diagram showing a configuration of a second exemplary embodiment.

FIG. 6 is a flowchart showing the flow of processing in the second embodiment.

FIG. 7 is a flowchart showing a flow of processing in the second embodiment.

FIG. 8 is a block diagram showing a configuration of a third exemplary embodiment.

FIG. 9 is a flowchart showing the flow of processing in the third embodiment.

FIG. 10 is a flowchart showing the flow of processing in the third embodiment.

FIG. 11 is an explanatory diagram showing a relationship between a straight line distance and a curve distance.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Position detection means 2 Speed calculation means 3 Interval calculation means 4 Leading vehicle discrimination means 5 Output means 10 Optical laser radar device 11 Clock generator 12 Light transmitter 13 Light receiver 14 Amplifier 15 Distance detection circuit 20, 20 ', 20 "Calculation Circuit 21 D / A converter 22 Scanning device 23 Vehicle speed sensor 24 Alarm determination circuit 25 Alarm device 30 Raindrop detection sensor 31 Steering angle sensor Lt Laser light Lr Reflected light Q Search area angle Q'Light receiving viewing angle θ Irradiation angle

Claims (1)

[Claims] 1. A position detecting means for transmitting an electromagnetic wave, inputting a reflected wave thereof to detect a plurality of reflecting objects at different positions with respect to the vehicle, and outputting position data thereof, and a plurality of the reflecting objects. Speed calculating means for calculating each moving speed, distance calculating means for calculating an interval between the plurality of reflecting objects based on the position data, and distances from the own vehicle among the plurality of reflecting objects are substantially equal to each other. Distance information is obtained from preceding vehicle discrimination means for discriminating a reflecting vehicle whose moving speeds are substantially equal to each other and a distance between them is within a predetermined range as a preceding vehicle, and the position data of the reflecting object discriminated as the preceding vehicle. An inter-vehicle distance measuring device for a vehicle, comprising: output means for outputting.