JP2835765B2 - Automatic traveling device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an automatic traveling device that allows a vehicle to travel automatically while searching for a traveling road.

2. Description of the Related Art Recently, there has been developed an automatic traveling device that sets an optimal target route on a traveling route while searching for the traveling route by oneself and controls the traveling of the vehicle so that the vehicle travels on the target route. Have been.

Conventionally, in an automatic traveling apparatus of this type, an image capturing apparatus attached to a vehicle captures an image of a region in a traveling direction of the vehicle, and a continuous image such as a road edge is obtained based on image data obtained by sampling. A line segment is extracted, a travelable region in the traveling direction of the vehicle is recognized based on the extracted line segment, and a target route for vehicle travel is set in the recognized travelable region, and the current detection is performed. According to the running state of the vehicle, a control target amount required to join the vehicle to a target point set on the target route is predictively obtained by a predetermined calculation, and according to the obtained control target amount. The running control of the vehicle such that the vehicle follows the target route is sequentially performed at a predetermined control cycle (Japanese Patent Application No. 63-19 / 1988).
No. 9610).

In such an automatic traveling apparatus, a time required for processing from sampling of a captured image to recognizing a travelable area of the vehicle based on data of the sampled image (hereinafter, referred to as image processing time). However, a road edge used for recognizing a travelable area based on whether the area in the traveling direction of the vehicle imaged by the imaging device is complex, that is, whether the data amount of the sampling image is large, or from the image. And different image processing methods such as extraction of white lines on a road using color information.

In addition, when setting a target point on a target route, conventionally, in order to smoothly join the target point in accordance with the traveling speed of the vehicle, a predetermined prediction time is determined, and the prediction time and the current detection time are determined. The target point is set at a position ahead of the vehicle by a predetermined distance obtained from the vehicle speed.

As described above, conventionally, without considering the image processing time, a target point is set on the target route, and the traveling control of the vehicle such that the vehicle joins the target point is performed. If the image processing time as the pre-processing that is not directly related to the control becomes long, the followability to the target route is reduced, and the running of the vehicle when following the target route becomes unstable.

In addition, when performing the running control of the vehicle such that the vehicle merges with the target point on the target route, if the image processing time fluctuates, the actual vehicle position with respect to the target route becomes unstable, and the control amount changes. As the response gain changes, the running control of the vehicle becomes unstable if the image processing time becomes longer.

Objective The present invention has been made in consideration of the above points, and becomes indefinite for each control cycle, and takes into consideration the image processing time that accounts for a large proportion of the control cycle, and within the recognized travelable area. It is an object of the present invention to provide an automatic traveling device that can optimally perform control for traveling a vehicle following a set target route.

Configuration The present invention sets a target point on a target route to achieve the object, and when performing a traveling control of the vehicle by predictively obtaining a control target amount for merging the vehicle with the target point,
The position of the target point on the target route is variably set according to the image processing time from the sampling of the captured image to the recognition of the travelable area.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

In an automatic traveling apparatus according to the present invention, as shown in FIG. 1, an imaging unit 1 such as a video camera attached to a vehicle so as to be able to image an area in the traveling direction of the vehicle, and the imaging unit An image processing unit 2 that samples an image captured by the image processing unit 1 and processes data of the sampled image to extract a continuous line segment such as a road edge; and a road or the like according to the extracted continuous line segment. A travelable area recognizing section 3 for recognizing a travelable area of the vehicle, a target route setting section 4 for setting a target route for vehicle travel in the recognized travelable area, and a traveling speed v of the vehicle.
, A yaw rate sensor 7 for detecting a yaw rate あ る, which is an angular velocity change in the yaw direction along with the running of the vehicle, and a steering angle sensor 8 for detecting a steering angle δ of the vehicle.
Detects the running state of the vehicle at that time according to the output of each sensor, and determines the control target amount of the steering angle required for the vehicle to travel on the target route based on the detected running state of the vehicle. A control unit 5 for obtaining a predetermined arithmetic processing, performing centralized control of the entire automatic traveling apparatus, and measuring a required time (image processing time) from sampling of an image to recognition of a travelable area; And a steering control unit 9 and a steering drive unit 10 for steering the vehicle according to the obtained control target amount.

Actually, the image processing unit 2, the travelable area recognition unit 3, the target route setting unit 4, and the control unit 5 are replaced by a microcomputer. Further, the steering control unit 9 can be included in the computer.

As a video camera in the imaging unit 1, a camera using a telephoto lens or a wide-angle lens is provided in addition to a camera using a standard lens so that an appropriate image can be obtained according to a vehicle speed or a road condition during traveling. Are provided with a plurality of special video cameras such as an infrared camera and an ultra-sensitive camera, and under control of a computer, the plurality of video cameras are appropriately switched and used according to a vehicle speed, a state of a captured image, and the like. It has become.

It is also possible to arrange two video cameras having the same imaging characteristics in parallel to obtain an image by binocular stereovision.

The extraction of continuous line segments such as road edges in the image processing unit 2 is performed as follows.

First, a sampled image sent from the image pickup unit 1 is sampled, and the sampled input image is differentiated to perform image edge detection processing. The automatic threshold value setting circuit automatically sets an optimum threshold value according to the density of the input image at that time, and binarizes the edge image.

At that time, the binarization of the input image may be performed first, and then the differentiation processing for edge detection may be performed. Further, instead of performing binarization, multi-value conversion expressing the shading of an image may be performed.

Next, based on the edge-detected and binarized or multi-valued processed image, a line segment on the XY coordinate is defined as ρ-
By performing a Hough transformation process, which is a known method of performing coordinate transformation represented by a point on the θ coordinate, a continuous point sequence is combined, or an isolated point having no continuity is removed, For example, information on a continuous line segment of a road edge as shown in FIG. 2 is obtained.

Here, θ is the angle of the perpendicular drawn from the straight line on the XY coordinate to the origin of the coordinate, and ρ is the length of the perpendicular. For example, a line segment L on the XY coordinates shown in FIG.
Is represented as a point O1 on the ρ-θ coordinates as shown in FIG.

In this case, based on the binarized processed image, an edge tracking process may be performed to extract an edge portion of the image having continuity. In addition, a plurality of processes such as a Hough transform process and an edge tracing process for obtaining continuity of an image edge are performed in parallel, and a comprehensive judgment is made based on a result of each of the processes. Edge information can be obtained.
Further, if the processing for extracting the above-described continuous image edge is performed while growing the area of the input image as the vehicle travels, more accurate road edge information can be extracted. Become.

Since the image captured by the video camera in the imaging unit 1 is based on the perspective projection, the travelable area recognition unit 3 uses the perspective projection road image shown in FIG. 2 as shown in FIG. A projection conversion process, which is a known method for converting the image into a road edge image in which the influence of the perspective projection is eliminated, is performed.

The projection conversion characteristics are set in advance in the travelable area recognition unit 3 in accordance with the characteristics of the perspective projection of the video camera.

Then, based on the road edge image subjected to the projective transformation processing, for example, as shown in FIG. 4, the travelable area recognition unit 3 connects the continuous road edges E1 and E2 to the image pickup direction of the image pickup unit 1, that is, the vehicle 11. Of the vehicle on the XY coordinates when the traveling direction of the vehicle is the Y-axis direction.

In FIG. 4, the point P indicates the current position of the vehicle 11, and the center of the lower end of the imaging area of the imaging unit 1 by the video camera is set as the point P at the position of the origin on the XY coordinates. The mounting position of the video camera with respect to the vehicle is set in advance.

Then, in the control unit 5, a required time (image processing time) from sampling of the captured image to recognition of the travelable area RA is measured by an internal clock.

 FIG. 10 shows a flow of the image processing time measurement.

Next, when the road ahead of the vehicle, which is the driveable area recognized by the driveable area recognition unit 3, is recognized, the target route setting unit 4 becomes the optimal travel route of the vehicle on the recognized road. The target route is set as follows.

The target route is desirably set so as to be suitable for the running condition of the vehicle at that time, taking into account the road shape and the vehicle speed, as described later. It is uniformly recognized as follows depending on whether it is narrow or wide.

That is, when the target route setting unit 4 determines that the road width is a wide orbit having a certain width or more, for example, the fourth
As shown in the figure, in the case of a left-hand traffic road, a target route OC is set along the reference edge with a predetermined separation width w of, for example, about 1.5 m from the reference edge on the left side of the road.

When the target route setting unit 4 determines that the track is a narrow track with a road width smaller than a certain value, the target route is set at the center of the road, though not particularly shown.

Then, data of the position of the set target route on the XY coordinates is stored in the internal memory of the target route setting unit 4.

Note that the scale of the travelable area and the target route on the XY coordinates is determined by the magnification of the video camera in the imaging unit 1.

In FIG. 4, the trajectory from the point P to the point O indicates that the vehicle at the point P joins the target route OC by controlling the steering of the vehicle under the control of the control unit 5 as described later. It shows a traveling route up to the start. The point O is a target point at which the vehicle joins the target route OC at that time.

In the present invention, it is also possible to detect the running state of the vehicle and set an optimal target path of the vehicle on the road as described below according to the detected running state.

That is, the target route setting unit 4 reads, for example, the traveling speed of the vehicle detected by the vehicle speed sensor 6, and if the vehicle speed at that time is within a low speed range equal to or less than a preset threshold value, FIG. As shown in a), the target route OC is set so as to follow the shape of the road.

Similarly, if the vehicle speed at that time is within a high-speed range exceeding a preset threshold value, as shown in FIG.
When traveling on a winding road, a target route OC having a gentle curvature is set in the road so that the lateral acceleration acting on the vehicle is reduced as much as possible.

Next, when the target route on the road is set, the control unit 5 obtains the control target amount of the steering angle for joining the vehicle to the target route as follows.

According to the present invention, a future traveling route is predicted from the traveling state of the currently detected vehicle, and a deviation between the predicted route of the vehicle and the target route is used to calculate a steering angle for the vehicle to travel on the target route. A correction amount is obtained, and a control target amount is calculated from the steering angle correction amount.

Basically, based on the running speed of the current vehicle, the arrival point of the vehicle on the predicted route after a certain time is predicted, and the vehicle is moved to a position on the target route obtained by the running speed of the vehicle and the certain time. A target point to be merged is set, and a steering angle correction amount is obtained according to a deviation between the predicted arrival point and the target point.

At this time, in the present invention, in particular, the control unit 5
In consideration of the image processing time measured in, the target point on the target route is variably set together with the predicted arrival point on the predicted route.

Now, for example, as shown in FIG.
Let's consider a case in which is merged with the target route OC.

First, based on the current vehicle speed v (m / s) of the vehicle detected by the vehicle speed sensor 6, a predetermined time t of the vehicle at the point P is determined.
_m predetermined time in consideration of the image processing time t _B to (t _m + t _B) the distance on the Y-axis after seconds L (m) {L = ( t m + t B) ×
v｝ is obtained, and the deviation on the X axis between the target path OC and the point C separated by a distance L from the point P on the Y axis.
x _l, issued namely (t _m + t _B) seconds value instead of the usual proportional to the position of the target point O set on the target course OC after.

Similarly, the predicted path A of the vehicle based on the yaw rate Υ (rad / s) of the vehicle detected by the yaw rate sensor 7
C is calculated and the deviation x of the predicted route AC from the point C on the Y axis
_m, that is, a value proportional to the position of the arrival point M of the vehicle on the predicted path AC in (t _m + t _B) seconds after is obtained as follows.

Now, assuming that the radius of the arc drawn by the predicted route AC is R,
x _m is given by:

x _m = R− ｛R ² −L ² ｝ ^1/2 = R−R ｛1− (L / R) ² ｝ ^1/2 where R ≒ L, x _m ≒ R−R ｛1− ^{(L / R) 2/2} } = L 2 / 2R ... (1) in addition, since it is Υ = v / R ... (2 ), (1), (2) where, x _m = L ² · Υ / 2v (3) The sign of the yaw rate 例 え ば is, for example, a predicted path.
When AC turns left, it is defined as positive.

Then, a difference e (e = x _l −) between the obtained deviations x _l and x _m is obtained.
x _m ), the yaw rate ΔΥ of the vehicle to be corrected is determined according to the following equation.

ΔΥ = e × 2v / L ² (4) Next, the steering angle δ of the vehicle at the point P detected by the steering angle sensor 8 is taken in, and the steering angle control target for merging the vehicle with the target route OC is obtained. The quantity δ 'is determined as follows.

 Now, in the relationship shown in FIG. 7, when R≫1, δ ≒ l / R (5), and from equations (2) and (5), δ = (l / v) Υ (6) Is obtained. Here, 1 is a wheel base.

Therefore, from the relationship of the equation (6), the correction amount Δδ of the steering angle corresponding to the yaw rate ΔΥ to be corrected of the vehicle is given by the following equation.

Δδ = (l / v) ΔΥ (7) where l = l which is a general formula of the steering angle with respect to the vehicle speed v
In consideration of (1 + Kv ² ), from Expression (7), Δδ = ΔΥ ｛l (1 + Kv ² ) / v｝ (8)

K is a constant coefficient (stability factor) determined by vehicle characteristics such as tire characteristics and wheelbase.

Then, the control target amount δ ′ of the steering degree for merging the vehicle with the target route OC is obtained as δ ′ = δ + Δδ (9).

The steering control unit 9 issues a drive command to the steering drive unit 10 according to the control target amount δ ′ given from the control unit 5, whereby the steering drive unit 10 appropriately drives the steering to move the vehicle to the target route OC. Steer to join.

In the relationship shown in FIG. 6, when the distance L serving as a reference for setting the target point O on the target route OC is determined, the control unit 5
Under the control of, by appropriately adjusting the t _m time in accordance with the vehicle speed v detected by the vehicle speed sensor 6, it is possible to set the distance L variable.

That is, the lower the traveling speed v, the shorter the distance L is set, and the shorter the traveling route until the vehicle is merged with the target route OC of the vehicle at the point P, the shorter the target route OC of the vehicle.
Merge quickly. Further, the higher the traveling speed v, the longer the distance L is set, and the longer the traveling route until the vehicle at the point P joins the target route OC, the longer the traveling route is. Let it run slowly.

Further, when traveling on a winding road, the smaller the curvature is, the shorter the distance L is set, and the target route OC of the vehicle is set.
It is also possible to cause the merging to be performed quickly.

The above processing is repeatedly performed with a predetermined control cycle, and as the traveling of the vehicle progresses, the vehicle following the target route OC set in the travelable area sequentially recognized in each control cycle is determined. Travel control is continuously performed.

 FIG. 11 shows a control flow in the present invention.

Effect As described above, in the automatic traveling apparatus according to the present invention, the recognized traveling is performed while recognizing the travelable area based on the image obtained by capturing the traveling direction of the vehicle by the imaging device attached to the vehicle. A target route is set in the possible area, a target point is set on the target route, and a control target amount for joining the vehicle to the target point is obtained by a predetermined calculation to control the steering angle of the vehicle. When performing the control, the position of the target point on the target route is set variably according to the image processing time from sampling the captured image to recognizing the travelable area. In addition, it is possible to optimally perform the traveling control of the vehicle in consideration of the image processing time which accounts for a large proportion in the control cycle, and the followability of the vehicle traveling on the target route is good. As a result, the vehicle can be stably driven.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an automatic traveling apparatus according to the present invention. FIG. 2 is a view showing road segments obtained by performing data processing on an image taken by a video camera. FIG. 3 is a diagram showing an image obtained by projectively transforming the image of FIG. 2, FIG. 4 is a diagram showing an example of a target route set in a travelable area between recognized road edges, and FIG. FIGS. 7A and 7B show target routes set on the road at low and high speeds of the vehicle, respectively. FIG. 6 shows the relationship between the target route and the predicted route of the vehicle. Is a diagram showing the relationship between the steering angle of the vehicle and its turning radius, FIG. 8 is a diagram showing a line segment on the XY coordinate, and FIG. 9 is a graph showing ρ- Diagram showing a point on the θ coordinate, FIG. 10 is a diagram showing a flow of image processing time measurement,
FIG. 11 is a diagram showing a control flow in the present invention. DESCRIPTION OF SYMBOLS 1 ... Image pick-up part, 2 ... Image processing part, 3 ... Drivable area | region recognition part, 4 ... Target route setting part, 5 ... Control part, 6 ...
Vehicle speed sensor 7, yaw rate sensor 8, steering angle sensor 9, steering control unit 10, steering drive unit 11, vehicle, RA, travelable area, OC, target route, P … Vehicle position

Claims (3)

(57) [Claims] 1. A means for imaging a region in the traveling direction of a vehicle by an imaging device mounted on a vehicle, and a means for extracting a line segment by sampling the captured image and subjecting the sampled image to data processing. Means for recognizing a travelable area in the traveling direction of the vehicle based on the extracted line segment, means for setting a target route in the recognized travelable area, and means for detecting a traveling state of the vehicle Means for setting a target point on the target route and obtaining a control target amount necessary for merging the vehicle with the target point based on the detected traveling state of the vehicle; and the obtained control target. In an automatic traveling apparatus comprising means for controlling traveling of the vehicle according to the amount, the time required for image processing is measured and set on the target route according to the measured time. Automatic traveling apparatus characterized by the distance to the target point and so as to proportionally change that. 2. The automatic traveling apparatus according to claim 1, wherein the traveling state of the vehicle is a yaw rate and a vehicle speed. 3. The automatic traveling apparatus according to claim 1, wherein an object of traveling control of the vehicle is a steering angle.