JP3580152B2 - Inter-vehicle distance detection device - Google Patents

Description

【００１３】
候補点のうちでＳＳＤ値の最も小さい（相関が高い）窓に対応する点４６を移動先の点として決定する。ステップ３６では、それぞれの点が追尾に成功したか失敗したかを判定する。この判定部分はレーザレーダが正常に作動しているときのみ動作し、レーザレーダ不作動時には動作しない。図４（ｃ）に示すように、レーザレーダによる先行車存在範囲４５の範囲内にある点は追尾に成功したものとし、ステップ３４に戻って追尾を継続する。一方、範囲外にある点４７は追尾に失敗した点とし、ステップ３７にて新たな追尾点を作成し追尾をやり直す。そして最終的に全ての追尾点が先行車画像上に配置されるようにする。以上のような画像処理を行なった後、車間距離を算出する動作に移る。
【００１４】
車間距離の算出では、まずステップ３８にて、先行車画像上に配置された複数の追尾点の集団の重心を計算する。そしてステップ３９にて、この重心との関係を用いて追尾点位置の水平方向の分散σを算出する。追尾点の集団（ｎ個）の重心を（Ｘ，Ｙ）、追尾点の座標を（Ｘ_ｋ，Ｙ_ｋ）としたとき、ｎ個の追尾点の集団の水平方向の分散σは次の（数２）で求められる。
【００１５】
【数２】

【００１６】
図４（ａ）のように、先行車までの車間距離が小さくなったときは、先行車画像は画面中で大きくなり画像上の各追尾点の間隔が広がって、水平方向の各追尾点位置（Ｘ_ｋ）が重心位置（Ｘ）から離れるので分散σは大きくなる。逆に、図４（ｃ）のように、先行車までの車間距離が大きくなったときは、先行車画像は画面中で小さくなり画像上の各追尾点の間隔が狭まって、水平方向の各追尾点位置（Ｘ_ｋ）が重心位置（Ｘ）に近づくので分散σは小さくなる。ステップ４０では、この分散と車間距離との関係を用いて車間距離計測用係数ｈを算出する。即ち、ある時点においてレーザレーダ６で得られた先行車までの車間距離をＤとし分散をσとすると、車間距離計測用係数ｈは、ｈ＝Ｄ×σより算出される。算出された車間距離計測用係数ｈは、車間距離計算部２３に備えられた図示しない記録媒体に保持される。ステップ４１では、レーザレーダ６の不作動時において、この算出された車間距離計測用係数ｈおよびレーザレーダ不作動時点における分散σ_ｅを用いて、先行車までの車間距離Ｄ_ｅを計算し推定する。推定車間距離Ｄ_ｅは、Ｄ_ｅ＝ｈ／σ_ｅより算出される。この推定車間距離Ｄ_ｅの値に基づいて、制御信号生成部３は制御信号を出力し、ブレーキアクチュエータ７やスロットルアクチュエータ８を制御し、また推定車間距離の値を車両室内の操作・情報表示部９に表示する。
【００１７】
このように本実施例では、レーザレーダ６の不作動時において、その直前に得られたレーザレーダによる先行車までの車間距離および追尾点の集団の分散から車間距離を計算し推定しているので、先行車までの車間距離を精度良く推定することができる。また、１台のカメラで得られた先行車画像に複数の追尾点を付与し同時に追尾するので、追尾に失敗した点が何点かあっても車間距離算出の精度に影響が少ない。
【００１８】
【発明の効果】
本発明によれば、車間距離検出手段の不作動時に、１台の撮像手段を用いて先行車までの車間距離を精度良く検出可能な車間距離検出装置を提供できる。
【図面の簡単な説明】
【図１】本発明に係る車間距離検出装置を搭載した車両の模式図である。
【図２】本発明に係る車間距離検出装置の一実施例を示す図である。
【図３】本発明に係る車間距離検出装置の動作を示すフローチャートである。
【図４】（ａ）、（ｂ）、（ｃ）はそれぞれ追尾点を用いて先行車を追尾する方法を説明するための図である。
【符号の説明】
１ コントローラ
２ 車間距離推定手段
３ 制御信号生成部
４ 車両
５ カメラ
６ レーザレーダ
７ ブレーキアクチュエータ
８ スロットルアクチュエータ
９ 操作・情報表示部
１０ スイッチ
１１ Ｌ／Ｒ不作動検出部
２１ 画像入力部
２２ 画像処理部
２３ 車間距離計算部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an inter-vehicle distance detection device that detects an inter-vehicle distance to a preceding vehicle, and more particularly to an inter-vehicle distance detection device suitable for accurately detecting an inter-vehicle distance when approaching a preceding vehicle.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an automatic vehicle tracking system has been proposed so that a driver can easily drive with a safe inter-vehicle distance. This system, for example, automatically controls the throttle or brake to decelerate the vehicle when the vehicle approaches the preceding vehicle, and conversely, automatically controls the throttle to accelerate the vehicle when it moves away, The inter-vehicle distance to the preceding vehicle is maintained within a predetermined range. Therefore, this type of system is provided with an inter-vehicle distance detecting device for detecting an inter-vehicle distance to a preceding vehicle.
[0003]
As a device for detecting an inter-vehicle distance, there is, for example, an in-vehicle distance measuring device disclosed in JP-A-4-276585. This device uses a short-distance distance sensor and a long-distance distance sensor together. A CCD camera or ultrasonic radar device is used for the short-distance distance sensor, and a laser radar is used for the long-distance distance sensor. And radio wave radar. Then, in the measurement of the inter-vehicle distance to a preceding vehicle traveling a short distance, when there is almost no contrast of the preceding vehicle or when the ultrasonic wave is not reflected, the distance to the preceding vehicle can be measured by the short-distance ranging sensor. If the distance cannot be determined, the distance is calculated based on the distance to the object estimated from the vehicle speed and the distance output from the distance measuring sensor for long distance that is not originally used as the distance output, and the smaller distance is used. Then, the vehicle follows the preceding vehicle.
[0004]
[Problems to be solved by the invention]
In the prior art, two CCD cameras used as a distance measuring sensor for a short distance are installed at the front of a vehicle at predetermined intervals and vertically or horizontally, and a difference in the image forming positions of both CCD cameras is detected to perform triangulation. Is used to measure the inter-vehicle distance to the preceding vehicle. However, since this sensor has two CCD cameras, there is a problem that the cost of the sensor itself is high, and an installation space for two cameras is required. In addition, when this sensor is used for a long time, the separation distance between the two CCD cameras changes due to vibrations during running of the vehicle, and as a result, the accuracy of the inter-vehicle distance measurement using the principle of triangulation decreases. There is also a problem.
Therefore, without using such a plurality of CCD cameras, the accuracy of an inter-vehicle distance detection sensor such as a laser radar is improved, and the inter-vehicle distance from a long distance to a short distance is measured by the inter-vehicle distance detection sensor. It is possible. However, in this case, it is necessary to be able to detect the inter-vehicle distance even when the inter-vehicle distance detection sensor becomes inoperative for some reason. Therefore, it is required to provide a simple auxiliary means for detecting the following distance in preparation for such a case.
[0005]
Accordingly, it is an object of the present invention to provide an inter-vehicle distance detection device that can accurately detect an inter-vehicle distance to a preceding vehicle using one imaging unit when the inter-vehicle distance detection unit is not operated.
[0006]
[Means for Solving the Problems]
An inter-vehicle distance detection device according to the present invention inputs a preceding vehicle image obtained by an imaging unit such as a camera, and based on an inter-vehicle distance and a direction to a preceding vehicle separately obtained by an inter-vehicle distance detection unit such as a laser radar. Tracking points are respectively arranged at a plurality of places in the preceding vehicle image, an inter-vehicle distance measurement coefficient is calculated from the position information of the group of the tracking points and the inter-vehicle distance to the preceding vehicle, and the calculated inter-vehicle distance measurement coefficient and An inter-vehicle distance estimating unit configured to calculate an inter-vehicle distance from the position information of the group of tracking points at the present time. This is for estimating the inter-vehicle distance. Here, as the position information of the group of tracking points, for example, a variance value of the group of tracking points can be used. In this case, since there is a correlation between the inter-vehicle distance and the width of the preceding vehicle in the image, the variance can be calculated in the horizontal direction to simplify the calculation, and can be omitted in the vertical direction.
[0007]
In addition, when the inter-vehicle distance detecting means is not operated, for example, in a device using a laser radar as the inter-vehicle distance detecting means, when no output is obtained due to a failure of the laser radar itself, or when a preceding vehicle such as a large truck If the vehicle approaches and the laser light from the laser radar enters the lower part of the preceding vehicle and the reflected light cannot be obtained, sunlight or the laser light of another vehicle enters the laser radar, the detection accuracy decreases, and it temporarily operates. The case where the detection becomes impossible and the case where the subject of the distance detection is automatically or artificially switched from the laser radar to the camera are included. With the above-described configuration, when the inter-vehicle distance detecting means is not operated, the inter-vehicle distance from the position information of the group of tracking points to the preceding vehicle is calculated using the inter-vehicle distance measurement coefficient calculated and held immediately before. Can be accurately detected.
The inter-vehicle distance estimating means includes an image input unit for inputting a preceding vehicle image obtained by the imaging means, and an inter-vehicle distance D and a direction to the preceding vehicle obtained by the inter-vehicle distance detecting means. An image processing unit for arranging tracking points at a plurality of locations, position information of a group of tracking points obtained by tracking the tracking points at the plurality of locations in the preceding vehicle image, and, at this time, an inter-vehicle distance detecting means Calculation of the inter-vehicle distance measurement coefficient h from the inter-vehicle distance to the preceding vehicle obtained as described above, and calculation of the inter-vehicle distance D from the calculated inter-vehicle distance measurement coefficient h and the current position information of the group of tracking points. And a unit.
The inter-vehicle distance measurement coefficient h is a multiplication value (D) of a horizontal variance value σ of the group of tracking points obtained at a certain point in time and the inter-vehicle distance D to the preceding vehicle by the inter-vehicle distance detection means. × σ). The inter-vehicle distance estimating means divides the inter-vehicle distance measuring coefficient h obtained in advance by the horizontal variance σ _e of the group of the tracking points obtained at the present time when the inter-vehicle distance detecting means is not operating. Thus, the estimated value D _e (h / σ _e ) of the inter-vehicle distance from the preceding vehicle can be obtained.
Further, the inter-vehicle distance calculation unit, when performing tracking for the plurality of tracking points, sequentially selects the plurality of tracking points as a point of interest, sets a template around the point of interest, after a predetermined time, A window similar to that of the template is set in a range including the candidate point where the attention point is considered to have moved, and the difference between the brightness of the pixel in the template of the attention point and the brightness of the pixel in the window of the candidate point is set. However, the smallest tracking point can be set as the moved tracking point.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a schematic view of a vehicle equipped with an inter-vehicle distance detection device according to the present invention. As shown in the figure, the controller 1 includes an inter-vehicle distance estimating unit 2 and a control signal generating unit 3, and inputs image information of a preceding vehicle obtained by a camera 5 disposed in an upper front part of the vehicle 4. An inter-vehicle distance and a direction to a preceding vehicle obtained by an inter-vehicle distance detection sensor 6 disposed at a front end portion of the vehicle 4, for example, a laser radar or a radio radar (hereinafter, collectively referred to as a laser radar) are input. Normally, the controller 1 controls the brake actuator 7 and the throttle actuator 8 based on the following distance information to the preceding vehicle obtained by the laser radar 6. On the other hand, when the laser radar 6 is not operating, the controller 1 calculates based on the image information of the preceding vehicle obtained by the camera 5 and the inter-vehicle distance information to the preceding vehicle obtained when the laser radar 6 operates normally. The brake actuator 7 and the throttle actuator 8 are controlled according to the value of the inter-vehicle distance. The value of the inter-vehicle distance is displayed on the operation / information display unit 9 in the vehicle cabin.
[0009]
FIG. 2 is a diagram showing an embodiment of an inter-vehicle distance detection device according to the present invention. As shown in the figure, the inter-vehicle distance estimating means 2 uses the image input unit 21 for inputting the image information of the preceding vehicle obtained by the camera 5 and the inter-vehicle distance information to the preceding vehicle obtained by the laser radar 6. And an image processing unit 22 for arranging tracking points to be described later at a plurality of locations on the preceding vehicle image, and calculating an inter-vehicle distance measurement coefficient from the position information of a group of these tracking points and the above-described inter-vehicle distance information to the preceding vehicle. An inter-vehicle distance calculation unit 23 that calculates the inter-vehicle distance from the calculated inter-vehicle distance measurement coefficient and the position information of the group of tracking points at the current time. The switch 10 is connected to the control signal generator 3. One of the input terminals of the switch 10 is connected to the inter-vehicle distance estimating means 2 side, and the other is connected to the laser radar 6 side. The switch 10 is switched by an output from the laser radar (L / R) non-operation detecting unit 11.
[0010]
Normally, the switch 10 is connected to the laser radar 6 side. The control signal generation unit 3 inputs the inter-vehicle distance information to the preceding vehicle obtained by the laser radar 6 via the switch 10, and controls the brake actuator 7 and the throttle actuator 8, and sends the signal to the operation / information display unit 9. Generate the signal to be displayed. The laser radar non-operation detecting unit 11 monitors the inter-vehicle distance information obtained by the laser radar 6, and when the non-operation of the laser radar 6 is detected, switches the switch 10 from the laser radar 6 side to the inter-vehicle distance estimating means 2 side. . The detection of the inactivity of the laser radar 6 is performed, for example, when a unique value appears in the following distance information. Thereby, the control signal generation unit 3 inputs the calculated value of the following distance obtained by the following distance estimation means 2 through the switch 10, and controls the brake actuator 7 and the throttle actuator 8, and the operation / information display unit. 9 to generate a signal to be displayed.
[0011]
FIG. 3 is a flowchart showing the operation of the inter-vehicle distance detection device according to the present invention. As shown in the figure, in step 31, an image obtained by the camera 5 is input. In step 32, based on the inter-vehicle distance and direction to the preceding vehicle obtained by the laser radar (L / R) 6 as shown in FIG. decide. In Step 33, as shown in FIG. 4B, a plurality of tracking points are arranged in the existing range 48 of the preceding vehicle image 42. In step 34, these tracking points are sequentially selected as points of interest 43, and a template 44 for tracking the preceding vehicle is created. Here, the template 44 is a small window virtually provided around the tracking point. In step 35, the preceding vehicle is tracked using the template 44 as follows. That is, after a lapse of time dt from the time t, as shown in FIG. 4C, a plurality of small windows similar to the template are considered for a range including the candidate point where the point of interest is considered to have moved. The absolute value sum of the difference in brightness of the pixels in the window between the window of the candidate point and the window of the point of interest before movement is obtained. The absolute value sum (SSD: Sum of Squared Differences) are of interest coordinates _(x t, _{y t)} Brightness and _B of the (x _{t, y} t), the candidate points of the tracking coordinates _{(x t + dt, y t} + dt) Assuming that the brightness is B ( _{xt + dt} , yt _{+ dt} ) and the window is W, it can be obtained from the following (Equation 1).
[0012]
(Equation 1)

[0013]
The point 46 corresponding to the window having the smallest SSD value (high correlation) among the candidate points is determined as the destination point. In step 36, it is determined whether each point has succeeded or failed in tracking. This determination part operates only when the laser radar is operating normally, and does not operate when the laser radar is not operating. As shown in FIG. 4 (c), it is assumed that a point within the range 45 of the preceding vehicle by the laser radar has been successfully tracked, and the process returns to step 34 to continue the tracking. On the other hand, a point 47 outside the range is determined as a point at which tracking has failed, and a new tracking point is created in step 37 and the tracking is performed again. Finally, all the tracking points are arranged on the preceding vehicle image. After performing the image processing as described above, the operation proceeds to the operation for calculating the inter-vehicle distance.
[0014]
In calculating the inter-vehicle distance, first, in step 38, the center of gravity of a group of a plurality of tracking points arranged on the preceding vehicle image is calculated. In step 39, the horizontal variance σ of the tracking point position is calculated using the relationship with the center of gravity. Assuming that the center of gravity of the group of tracking points (n) is (X, Y) and the coordinates of the tracking points are (X _k , Y _k ), the horizontal variance σ of the group of n tracking points is Equation 2) is obtained.
[0015]
(Equation 2)

[0016]
As shown in FIG. 4A, when the inter-vehicle distance to the preceding vehicle decreases, the preceding vehicle image becomes larger in the screen, the interval between the tracking points on the image increases, and the position of each tracking point in the horizontal direction increases. Since (X _k ) is away from the position of the center of gravity (X), the variance σ increases. Conversely, as shown in FIG. 4C, when the inter-vehicle distance to the preceding vehicle increases, the preceding vehicle image becomes smaller on the screen, the interval between the tracking points on the image decreases, and the horizontal Since the tracking point position (X _k ) approaches the center of gravity position (X), the variance σ decreases. In step 40, the inter-vehicle distance measurement coefficient h is calculated using the relationship between the variance and the inter-vehicle distance. That is, assuming that the inter-vehicle distance to the preceding vehicle obtained by the laser radar 6 at a certain time is D and the variance is σ, the inter-vehicle distance measurement coefficient h is calculated from h = D × σ. The calculated inter-vehicle distance measurement coefficient h is stored in a recording medium (not shown) provided in the inter-vehicle distance calculation unit 23. In step 41, during non-operation of the laser radar 6, using a dispersion sigma _e in the calculated inter-vehicle distance measuring coefficient h and the laser radar inoperative time, the inter-vehicle distance D _e to the preceding vehicle calculated estimated . Estimated inter-vehicle distance _{D e is} calculated from _{D e} = h / _σ e. Based on the value of the estimated inter-vehicle distance D _e, the control signal generating unit 3 outputs a control signal to control the brake actuator 7 and the throttle actuator 8, also the operation-information display unit of a vehicle interior value of the estimated inter-vehicle distance 9 is displayed.
[0017]
As described above, in the present embodiment, when the laser radar 6 is not operating, the inter-vehicle distance is calculated and estimated from the inter-vehicle distance to the preceding vehicle and the dispersion of the group of tracking points by the laser radar obtained immediately before. In addition, it is possible to accurately estimate the inter-vehicle distance to the preceding vehicle. Further, since a plurality of tracking points are added to the preceding vehicle image obtained by one camera and tracking is performed at the same time, even if there are some points where tracking has failed, the accuracy of calculating the inter-vehicle distance is little affected.
[0018]
【The invention's effect】
According to the present invention, it is possible to provide an inter-vehicle distance detection device that can accurately detect the inter-vehicle distance to a preceding vehicle using one imaging unit when the inter-vehicle distance detection unit does not operate.
[Brief description of the drawings]
FIG. 1 is a schematic view of a vehicle equipped with an inter-vehicle distance detection device according to the present invention.
FIG. 2 is a diagram showing an embodiment of an inter-vehicle distance detection device according to the present invention.
FIG. 3 is a flowchart showing an operation of the inter-vehicle distance detection device according to the present invention.
FIGS. 4A, 4B, and 4C are diagrams illustrating a method of tracking a preceding vehicle using tracking points.
[Explanation of symbols]
Reference Signs List 1 controller 2 inter-vehicle distance estimating means 3 control signal generating unit 4 vehicle 5 camera 6 laser radar 7 brake actuator 8 throttle actuator 9 operation / information display unit 10 switch 11 L / R non-operation detecting unit 21 image input unit 22 image processing unit 23 Distance calculation unit

Claims (6)

An inter-vehicle distance detection device including an inter-vehicle distance detection unit that detects an inter-vehicle distance between the own vehicle and a preceding vehicle, and one imaging unit that images the preceding vehicle.
When the inter-vehicle distance detection unit is not operated , the vehicle includes an inter-vehicle distance estimation unit that estimates an inter-vehicle distance D to the preceding vehicle;
The inter-vehicle distance estimation means,
An image input unit for inputting a preceding vehicle image obtained by the imaging unit;
An image processing unit that arranges tracking points at a plurality of locations in the preceding vehicle image based on the following distance D and the direction to the preceding vehicle obtained by the following distance detection unit,
The position information of the group of the tracking points obtained by performing the tracking for the plurality of tracking points of the preceding vehicle image , and the inter-vehicle distance to the preceding vehicle obtained by the inter-vehicle distance detection means at this time. distance calculating a measurement factor h, characterized in that it is constituted by a vehicle distance calculating section that calculates the inter-vehicle distance D from the position information of the population of the tracking point in the calculated inter-vehicle distance measuring coefficient h and the present time to, inter-vehicle distance detection device. The inter-vehicle distance detection device according to claim 1, wherein a variance value of the tracking points is used as the position information of the group of the tracking points. The inter-vehicle distance detection device according to claim 2, wherein the variance value is a variance value σ of the group of the tracking points in a horizontal direction. The inter-vehicle distance measurement coefficient h is a multiplication value (D × σ) of a horizontal variance value σ of the group of tracking points obtained at a certain time and the inter-vehicle distance D to the preceding vehicle by the inter-vehicle distance detection means. 4. The inter-vehicle distance detecting device according to claim 3, wherein The inter-vehicle distance estimating means obtains the inter-vehicle distance measuring coefficient h obtained at the present time when the inter-vehicle distance detecting means does not operate, and obtains a horizontal variance σ of the group of the tracking points. _e Divided by the estimated distance D from the preceding vehicle _e The inter-vehicle distance detecting device according to claim 4, wherein The inter-vehicle distance calculating unit sequentially selects the plurality of tracking points as a point of interest when performing tracking on the plurality of tracking points, sets a template around the point of interest, and sets the template after a predetermined time. A window similar to the template is set in a range including the candidate point where the point is considered to have moved, and the difference between the brightness of the pixel in the template of the target point and the brightness of the pixel in the window of the candidate point is: The inter-vehicle distance detection device according to any one of claims 1 to 5, wherein the smallest one is set as the moved tracking point.

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