JP2919718B2 - Vehicle distance measuring device and vehicle equipped with it - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automobile distance measuring apparatus for measuring an inter-vehicle distance to a preceding vehicle, and more particularly to an automobile distance measuring apparatus suitable for accurately measuring a relatively long inter-vehicle distance by using image processing. It relates to a measuring device.

[0002]

2. Description of the Related Art Conventionally, as an apparatus of this type, there is one disclosed in Japanese Patent Application Laid-Open No. 3-195916. In this conventional apparatus, an optical image of an object is formed on the image sensor on the left and right by a pair of left and right optical systems, left and right image signals from the image sensor are compared, and a shift between both images is electrically detected. For an apparatus that measures the distance to an object based on the principle of triangulation, an image signal sampled at a predetermined time interval is compared between a certain time and the next time, and the best matching area is selected. Detects image signal deviation,
Finding the distance to the object.

[0003] Further, the inter-vehicle distance measuring device described in Japanese Patent Application Laid-Open No. 61-219825 captures an image of a rear vehicle with a camera in order to prevent the vehicle that is backing from colliding with the rear vehicle, and uses the rear of the image in the image. The distance between vehicles to the rear vehicle is calculated from the size of the license plate of the vehicle.

[0004]

Among the above-mentioned prior arts, those for measuring the distance to the object by the principle of triangulation require two or more optical systems, and furthermore, two or more optical systems. It is necessary to perform a considerable amount of processing in order to match the above image signals, and there is a problem that a processing device mounted on a vehicle becomes complicated and expensive.

In the prior art for calculating the inter-vehicle distance from the size of the license plate by calculation, only the extremely short inter-vehicle distance can be measured because the size of the license plate in the image becomes small. When this conventional technique is applied to the measurement of the inter-vehicle distance, there is a problem that an error increases . Therefore, the present invention cannot be applied particularly to the measurement of the inter-vehicle distance to a preceding vehicle on a highway where the inter-vehicle distance is several tens of meters or more.

It is an object of the present invention to provide a vehicle distance measuring device capable of measuring an inter-vehicle distance accurately over a relatively long distance.

[0007]

An object of the present invention is to provide an image pickup means for picking up an image of a reference sign for measuring an inter-vehicle distance and a preceding vehicle;
Preceding vehicle provided with a calculating means for calculating an inter-vehicle distance to said prior vehicle based on the known dimensions of the reference marker or lane width positioned, in combination with the above means, Nanbapu
Reference sign switch so that the rate can be used as a reference sign
Means for providing a step or changing the magnification of the imaging means
It is achieved by providing a.

[0008]

By using substantially the same size as a vehicle, for example, a lane width, as a reference mark, it is possible to accurately obtain the distance even if the distance between the vehicles is considerably large. For this reason, it is possible to calculate even at an inter-vehicle distance of, for example, 100 m like a highway. Furthermore, if the inter-vehicle distance can be accurately determined,
It is also possible to automatically control traveling while keeping the inter-vehicle distance constant. In addition to the above functions and effects,
Reference sign switching means so that the label can be used as a reference sign
Is provided, the inter-vehicle distance measuring means suitable for long distances
(Use of lane width) and inter-vehicle distance measuring means suitable for short distances
(Using a license plate)
it can. Also, means for changing the magnification of the imaging means is provided.
By installing, even when the distance between vehicles is long,
Also measures the distance between vehicles based on images of appropriate size.
Can be.

[0009]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory diagram of a measurement principle of a vehicle distance measuring device according to one embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a TV camera as an image pickup means, and an arithmetic processing device 2 as a distance measuring means takes in a video signal from the TV camera 1 and calculates an inter-vehicle distance L from the own vehicle 4 to the preceding vehicle 3. Then, the engine control unit of the own vehicle 4 is automatically controlled so that the inter-vehicle distance L is always constant, or an alarm is issued based on the relationship with the own vehicle speed detected by the speed sensor. Incidentally, the characteristics of the TV camera 1, the field of view 5, pseudo shown by the viewing angle theta _d.

FIG. 2 is a block diagram of a vehicle distance measuring apparatus according to one embodiment of the present invention. The video signal from the TV camera 1 is A / D converted by the A / D converter 8 and stored in the memory (R
AM) 9 is stored for one screen as a two-dimensional array of digital values. The recording method of the RAM 9 is a method in which a storage area is secured from a predetermined address by the number of pixels obtained by the A / D conversion, and the area is subdivided for each data in the horizontal direction. A of the video data
The / D conversion value is input, and is luminance information of each target point.

The arithmetic processing unit 2 includes ROMs 10 and 13,
It has CPUs 12 and 15 and RAMs 11 and 14,
M stores a program to be executed by the CPU, and RAM stores C
Various data associated with the PU operation processing is temporarily stored.
Reference numeral 16 denotes a waveform shaping circuit which shapes a signal from the vehicle speed sensor 17. The arithmetic processing unit 2 displays an actual inter-vehicle distance to a preceding vehicle and a safe inter-vehicle distance in accordance with the speed of the own vehicle on a display device 6 or sounds a buzzer sound for a certain time with an alarm device 7 to generate an alarm. Emits. In addition, for example, an auto speed control drive (A
The CPU 15 sends a distance measurement signal to the SCD) CPU,
Automatic control is performed so that the inter-vehicle distance to the preceding vehicle 3 is always kept constant or the inter-vehicle distance is equal to or longer than a safe inter-vehicle distance determined according to the speed of the own vehicle at that time.

In a vehicle equipped with various components shown in FIG. 2, when a vehicle key is turned on at the start of operation, power is supplied from a vehicle-mounted battery, and the electric system of each part is activated. In this operating state, the CPU 12 measures the inter-vehicle distance from the preceding vehicle. This measuring method will be described.

FIG. 3 is a flowchart showing an arithmetic processing procedure executed by the CPU 12. First, step 100
Then, the CPU 12 initializes a register, a counter, a latch circuit, and the like in the CPU 12 itself. In this embodiment, the measurement of the inter-vehicle distance is performed, for example, every 100 ms or 33 ms. Therefore, in the next step 101, it is determined whether or not the distance measurement execution time has come, and the process waits until the execution time comes. An internal timer is used for counting the execution time, and the calculation cycle from step 102 to step 113 is kept constant.

In step 102, the video data stored in the RAM 9 is loaded into the CPU. As the fetching order, the data in the horizontal direction from the data at address A to A +
Sequentially fetches data up to address n-1 and then A + n
The horizontal data is sequentially fetched again from the address data. In step 103, the captured video data is processed to generate, for example, binary image data from which an outline is extracted. Generally, there is a change in brightness (luminance) between the object and the background, and the contour of the object can be detected by differentiating the two-dimensional array of the luminance data two-dimensionally.

In step 104, a vehicle serving as an object, a center line serving as a reference sign, a vehicle body, a license plate, and the like are determined based on the binarized image data. In step 105, it is determined whether or not there is a preceding vehicle in the determined object. If there is no preceding vehicle, the preceding vehicle flag is cleared in step 106, and the process proceeds to step 114. If it is determined in step 105 that there is a preceding vehicle, the process proceeds to step 107, where a preceding vehicle flag is set. Subsequent step 10
In 8, it is determined whether the calculation of the inter-vehicle distance is possible based on the lane width. The determination method will be described with reference to FIG.

FIG. 5 shows the center line 18, the side line 19, and the preceding vehicle 3 determined from the binarized image data. In the object determined to be the preceding vehicle,
At the lowest position, a horizontal line 20 (in the illustrated example, a line connecting positions where both rear wheels of the preceding vehicle are in contact with the ground) is assumed.
When the horizontal line 20 intersects the center line 18 and the side line 19, the determination in step 108 is possible. In FIG. 5, the horizontal line 20 and the side line 1
9 does not intersect, so determination is impossible.

If it is determined in step 108 that the calculation is possible, in step 109
The length of the line segment intersecting 8, 19 is defined as the lane width, and
At 12, an inter-vehicle distance is calculated. If it is determined in step 108 that the calculation is impossible, in the present embodiment, the license plate of the preceding vehicle is determined in step 110, the license plate width is calculated in step 111, and the inter-vehicle distance is calculated in step 112, as in the prior art. Is calculated. In FIG. 5, it is needless to say that the line 19 may be extended on the screen and the lane width may be calculated using the intersection of the extended line and the horizontal line 20.

Here, the principle of calculating the inter-vehicle distance will be described with reference to FIG. When the input video data is projected onto a screen S at a certain distance R from the TV camera, the width h _d of the projection screen is different from that on the projection screen having a lane width H assumed at the last position of the preceding vehicle. Assuming that the length h and the angle therebetween are θ, the following relations of Expressions 1 and 2 are obtained.

[0019]

H / L = h / R

[0020]

R = (h _d / 2) / {2 · h · tan (θ _d / 2)} Rearranging both equations,

[0021]

L = (H · h _d ) / {2 · h · tan (θ _d / 2)}, and the inter-vehicle distance is obtained.

H is the lane width, but the width of the license plate may be used. Usually, the lane width is used, and when the width of the license plate approaches a sufficiently usable area, the inter-vehicle distance is calculated based on the width of the license plate.

In step 113, the relative speed with respect to the preceding vehicle is calculated from the inter-vehicle distance L. This relative speed calculation is performed using the difference between the previous inter-vehicle distance L0 and the current inter-vehicle distance L because the inter-vehicle distance detection is performed at a constant cycle. In step 104, the calculated information, that is, the preceding vehicle flag is set and reset, and when the preceding vehicle flag is set, the values of the following distance and the relative speed are set to C.
Transfer to PU15. Another CPU 15 included in the arithmetic processing device 2 inputs the preceding vehicle information calculated by the CPU 12, and performs display, warning, and information transfer to the ASCD. Hereinafter, the processing will be described.

FIG. 4 is a flow chart showing the operation procedure of the CPU 15. First, in step 200, the CP
Initialization of registers, counters, latch circuits, and the like inside U15 is performed, and in step 201, input processing of preceding vehicle information transferred from the CPU 12 is performed.

In the next step 202, the speed of the own vehicle is calculated. This speed calculation is performed by measuring the interval at which pulses are generated from the waveform shaping circuit 16. Step 2
At 03, it is determined whether or not the preceding vehicle flag is set based on information from the CPU 12. When it is determined that the preceding vehicle flag has been reset, step 208
Then, the display on the display 6 is deleted, and the process returns to step 201. When it is determined that the preceding vehicle flag is set, the process proceeds to step 204, where the safe inter-vehicle distance is calculated.

The safe inter-vehicle distance is calculated from the own vehicle speed calculated in step 202 and the relative speed with respect to the preceding vehicle calculated by the CPU 12. That is, the ROM 13 in the arithmetic processing device 2 stores in advance a characteristic map indicating the relationship between the own vehicle speed and the safe inter-vehicle distance.
The safe inter-vehicle distance is obtained from the own vehicle speed calculated in step 202 using the characteristic map, and the safe inter-vehicle distance is corrected based on the relative speed with respect to the preceding vehicle. This correction increases the safe inter-vehicle distance when the relative speed with the preceding vehicle is positive, that is, when the vehicle is away from the preceding vehicle, and increases when the relative speed with the preceding vehicle is negative, that is, when the vehicle approaches the preceding vehicle. This is done by shortening the distance.

Next, when the inter-vehicle distance from the preceding vehicle is within the safe inter-vehicle distance in step 205, the process proceeds to step 207, in which a buzzer is sounded for a predetermined time to give a warning. And
In step 206, the safe inter-vehicle distance and the inter-vehicle distance are displayed on the display, and the process returns to step 201. here,
The accuracy of the calculated inter-vehicle distance can be improved by increasing the magnification of the image.

FIGS. 6 and 7 are illustrations of lane width correction. As shown in FIG. 7, a part of the vehicle body is taken in the captured image. As shown in FIG. 6, when the actual width of the loaded vehicle and H _b, is counted and h _b is on the screen. The distance from the camera position to the vehicle body part entering into an image L _b, the distance from the camera position to the road position of the entering vehicle body portion and the same horizontal line in the image and L _0. When the actual width between the reference lane 18, 19 H0, the width at the screen of the lane width and h _0,

[0029]

H ₀ / H _b = (L _b × h ₀ ) / (L ₀ × h _b ) holds.

L _b and L ₀ are values that can be known in advance when the camera is set in the car, H _b is also the size of the body of the vehicle, and h ₀ and h _b are values that can be calculated on the screen. Therefore, the actual lane width H ₀ is obtained from the _{equation (} 4). This lane width correction task is not a task that must always be executed, and its priority can be lowered. Interrupt processing is performed at the time of merging, branching, or passing a sign position while the vehicle is running. This is a constant when the inter-vehicle distance is obtained by performing the filter processing. It should be noted that there is a section on the expressway where the inter-vehicle distance is checked, and the image screen of that section is shown in FIG. In such a place, the lane width is corrected, and the inter-vehicle distance calculated when the corrected value is used can be evaluated.

Next, measurement of the inter-vehicle distance when traveling on a curve will be described with reference to FIGS. The lane width on the screen when traveling on a curve is counted as h '(FIG. 9). On the other hand, on an actual road, as shown in FIG.
Is the lane width. In FIG. 10, the positional relationship between the front and rear two vehicles 3 and 4 and the relationship between the lane widths H and H ′ are as follows:

[0032]

H = H ′ · cos (2θ)

Here, the direction θ in which the preceding vehicle 3 can be seen from the own vehicle 4 is calculated by using the known dimensions of the vehicle in the drawing of FIG.

[0034]

H _b ′ = (t _b + t _b ′) · h ″ / (t ′ + t _b )

[0035]

[Equation 7] _{H b '= h b' ·} H b / h b

[0036]

[Equation 8] obtained by _{tanθ = H b '/ L b} . When traveling on a curve, these equations 6, 7,
8, the lane width is calculated, and the inter-vehicle distance is calculated using the calculated lane width.

Next, magnification switching will be described with reference to FIGS. The inter-vehicle distance is measured using a camera having two types of magnification modes, high magnification and low magnification. FIG.
Curves 111 (high magnification) and 112 (low magnification) shown therein are
It shows the relationship between the inter-vehicle distance and the lane width in the imaging screen at each magnification. Curves 121 (high magnification) and 122 (low magnification) shown in FIG. 12 show the relationship between the inter-vehicle distance at each magnification and the inter-vehicle distance measurement error of one dot on the imaging screen. Then, when the magnification of the camera changes from a short inter-vehicle distance to a long inter-vehicle distance, the inter-vehicle distance LL
To switch. When the inter-vehicle distance changes from long to short, the inter-vehicle distance L shorter than LL
Switch by S. The camera angle theta _d when the high magnification narrow field angle theta _d is widened at the time of low magnification.

The curves 111 and 112 are expressed by the following equation (9) obtained by transforming equation (3).

[0039]

H = (H · h _b ) / {2 tan (θ _d / 2) · L} The derivative of Equation 3 with h and Equation 9
Then, the following equation (10) is obtained.

[0040]

DH / dh = 2tan (θ _d / 2) · L ² / (H · h _d ) These are curves 121 and 122.

Normally, when there is no preceding vehicle, the magnification of the camera is set to a low mode. Measure the distance between vehicles. As a result, especially when a measurement result equal to or longer than the inter-vehicle distance LL is obtained at the time of merging or catching up with the preceding vehicle, the magnification is switched to a higher magnification.

When the inter-vehicle distance is reduced and the measured inter-vehicle distance becomes less than or equal to LS, the magnification is switched to a low magnification. If the inter-vehicle distance is near LE due to merging or the like at high magnification, the lane width cannot be measured on the screen. Therefore, at this time, the inter-vehicle distance is measured using the width of the license plate. For this measurement, LE
Check that the value is near. Here, when the inter-vehicle distance is calculated at the time of switching the magnification, tan
The value of (θ _d / 2) is changed in accordance with the time at which the magnification is switched. The calculated value is used as the inter-vehicle distance while comparing with the distance corresponding to the switching.

[0043]

According to the present invention, the inter-vehicle distance can be calculated by the four arithmetic operations by simple processing of image data by one camera, and inter-vehicle distance information can be obtained easily and accurately in all weather. There is an excellent effect.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a vehicle distance measuring method according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a vehicle distance measuring device according to one embodiment of the present invention.

FIG. 3 is a flowchart showing a distance measurement processing procedure executed by a CPU 12 shown in FIG. 2;

FIG. 4 is a flowchart showing an alarm processing procedure executed by a CPU 15 shown in FIG. 2;

FIG. 5 is an explanatory diagram of a method for determining whether or not the calculation of an inter-vehicle distance is possible based on a lane width.

FIG. 6 is an explanatory diagram for correcting a lane width by capturing an image of a part of a vehicle body.

FIG. 7 is a diagram showing a positional relationship between a camera and a vehicle body.

FIG. 8 is an imaging screen of an inter-vehicle distance confirmation sign.

FIG. 9 is an imaging screen when traveling on a curve.

FIG. 10 is an explanatory diagram of a positional relationship when traveling on a curve.

FIG. 11 is an explanatory diagram of a relationship between a distance and a lane width when the magnification is switched.

FIG. 12 is an explanatory diagram of a relationship between a distance and an error when a magnification is switched.

[Explanation of symbols]

1 ... TV camera, 2 ... arithmetic processing unit, 5 ... TV camera field of view, 6 ... display device, H ... lane width, L ... inter-vehicle distance.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-155908 (JP, A) JP-A-61-219825 (JP, A) JP-A-64-88210 (JP, A) JP-A-60-1985 235016 (JP, A) JP-A-4-12143 (JP, A) JP-A-6-229759 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01C 3 / 00-3 / 32 G01B 11/00-11/30

Claims (6)

(57) [Claims] 1. An image pickup means for picking up an image of a reference sign for measuring an inter-vehicle distance and a preceding vehicle, and a calculating means for calculating an inter-vehicle distance to the preceding vehicle based on a known size of the reference sign where the preceding vehicle is located. , For lane ahead, based on lane width
License plate for the preceding vehicle
And a reference sign switching means for use as a reference sign . 2. An image pickup means for picking up an image of a reference sign for measuring an inter-vehicle distance and a preceding vehicle, and a calculating means for calculating an inter-vehicle distance to the preceding vehicle based on a known lane width in which the preceding vehicle is located. And the magnification of the imaging means is set to the preceding vehicle.
Automotive distance measuring apparatus according to claim Rukoto provided with means for varying in accordance with the distance to the. 3. An image pickup means for picking up an image of a reference sign for measuring an inter-vehicle distance and a preceding vehicle, and a calculating means for calculating an inter-vehicle distance to the preceding vehicle based on a known size of the reference sign where the preceding vehicle is located. The size of the vehicle body imaged by the imaging means.
The lane width at the own vehicle position is calculated from the
An automobile distance measuring device comprising means for correcting a known size of a quasi-sign . 4. A reference sign for measuring an inter-vehicle distance and a preceding vehicle
Imaging means for imaging the vehicle, and the lane width where the preceding vehicle is located
An act of calculating the inter-vehicle distance to the preceding vehicle based on known dimensions
Calculation means and the size of the vehicle body imaged by the imaging means
The lane width at the own vehicle position is calculated from the
Means for correcting the known size of the sign . 5. A reference sign and a preceding vehicle for measuring a distance between vehicles.
And a reference sign at which the preceding vehicle is located
Calculate the inter-vehicle distance to the preceding vehicle based on the known dimensions of
Computing means, and the imaging means at the time of traveling on a curve
The direction of the preceding vehicle is determined from the image captured by
An automobile distance measuring device comprising means for correcting a distance. 6. A reference sign and a preceding vehicle for measuring a distance between vehicles.
Imaging means for imaging the vehicle, and the lane width where the preceding vehicle is located
An act of calculating the inter-vehicle distance to the preceding vehicle based on known dimensions
And a calculation unit, and automobile distance measuring apparatus comprising means for correcting the inter-vehicle distance with said direction seeking direction of the preceding vehicle from the image taken by the image pickup means during cornering.