JP2923668B2 - 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 a target route on a traveling route while searching for a traveling route by oneself and controls a steering angle so that a vehicle travels following the target route. Is being developed.

2. Description of the Related Art Conventionally, in an automatic traveling device of this type, an image capturing device attached to a vehicle captures an image of a region in a traveling direction of the vehicle, and a road edge or the like is obtained based on image data obtained by sampling the captured image. The continuous line segment is extracted, the travelable area in the traveling direction of the vehicle is recognized based on the extracted line segment, and the target route of the vehicle travel is set in the recognized travelable area. The vehicle follows the target route according to the detected traveling state of the vehicle while detecting the current traveling state of the vehicle, such as the steering angle, the yaw rate (the change in the angular velocity in the yaw direction due to the traveling of the vehicle). The control target amount of the steering angle for traveling is obtained by a predetermined calculation, and the control of the steering angle of the vehicle is performed using the control target amount (Japanese Patent Application No.
63-199610).

Thus, in such an automatic traveling device, when setting a target route in a travelable area, the dynamic load of the vehicle such as a yaw rate is not taken into account at the time of traveling without any consideration.
For example, the target route is set uniformly in the center of the travelable area.

The present invention has been made in consideration of the above points, and when setting a target route in a travelable area, an optimal target route is set in consideration of a dynamic load of a vehicle, and the target route is followed. An object of the present invention is to provide an automatic traveling device that can stably drive a vehicle.

Configuration The present invention focuses on the yaw rate as the dynamic load of the vehicle to achieve the object, and initially sets the target route uniformly within the travelable area without considering the yaw rate when the vehicle is running. The yaw rate when assuming that the vehicle travels on the set target route is obtained by arithmetic processing, and the yaw rate is corrected so that the obtained yaw rate does not exceed a preset limit value within the travelable area. The target route initially set is corrected so as to conform to the corrected yaw rate. As a calculation process for obtaining the yaw rate applied to the vehicle, a conventionally known calculation method is widely applied.

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

In the automatic traveling apparatus according to the present invention, as shown in FIG. 1, an image pickup unit 1 is provided by a video camera or the like attached to a vehicle so as to be able to take an image of a region in a traveling direction of the vehicle, and the image pickup 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 unit 3 for recognizing a travelable area of the vehicle, a target route setting unit 4 for uniformly setting a target route for vehicle travel within the recognized travelable area, and detecting a travel speed v of the vehicle. The vehicle running state includes a vehicle speed sensor 6, a yaw rate sensor 7 that detects a yaw rate あ る, which is a change in angular velocity in the yaw direction, and a steering angle sensor 8 that detects a steering angle δ of the vehicle. Various sensors for outputting, and after correcting the target route so that the yaw rate of the vehicle when traveling on the target route does not exceed a preset limit value, is detected by each sensor. A control for obtaining a control target amount of a steering angle necessary for the vehicle to travel on the corrected target route based on a traveling state of the vehicle by a predetermined arithmetic processing, and performing a centralized control of the entire automatic traveling apparatus. It comprises a unit 5, a steering control unit 9 for steering the vehicle in accordance with the obtained control target amount, and a steering drive unit 10.

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. In addition, 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 this 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 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 representing a point on a −θ coordinate, a continuous point sequence is combined, or an isolated point without discontinuity 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 a perpendicular drawn from the straight line on the XY coordinate to the origin of the coordinate, and ρ is the vertical length. 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 perspective projection, the travelable area recognition unit 3 performs a projection conversion process that is a known method. That is, for example, an image of a road edge by perspective projection as shown in FIG. 2 is converted into an image of a road edge in which the influence of perspective projection is eliminated as shown in FIG.

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 image of the road edge subjected to the projective transformation processing, the travelable area recognition unit 3 connects the continuous road edges E1 and E2 between the continuous road edges E1 and E2 as shown in FIG. 11 is recognized as the vehicle travelable area RA on the XY coordinates when the traveling direction 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.

Next, when the road ahead of the vehicle, which is the drivable area recognized by the drivable area recognition unit 3, is recognized, the target route setting unit 4 sets the target route to be the running route of the vehicle on the recognized road. Is set as follows.

It is desirable that the target route be set so as to be suitable for the traveling condition of the vehicle at that time in consideration of the road condition and the vehicle speed, as will be described later. It is set uniformly 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 left reference edge 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 the vehicle 11 at the point P on 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 merging. The point O is a target point at which the vehicle joins the target route OC at that time.

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

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

Similarly, if the vehicle speed v at that time is within a high-speed range exceeding a preset threshold value, as shown in FIG. 5B, when traveling on a winding road, the lateral direction acting on the vehicle A target route OC having a gentle curvature such that the acceleration of the vehicle is reduced as much as possible is set in the road.

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

Here, a future traveling route is predicted from the currently detected traveling state of the vehicle, and a deviation of the predicted route of the vehicle from the target route is used to correct a steering angle for the vehicle to travel on the target route. An amount is obtained, and a control target amount is calculated from the steering angle correction amount.

Specifically, based on the current traveling speed of the 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 traveling 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.

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 of the vehicle detected by the vehicle speed sensor 6 (m / s), the distance on the Y-axis at a predetermined time t _m seconds after the vehicle 11 in the point P L (m) (L = t _m × _v )
Is obtained, and a deviation x _l on the X-axis between a point C separated by a distance L from the point P on the Y-axis and the target path OC,
That it is issued value instead of the usual proportional to the position of the target point O set on the target course OC at t _m seconds.

Similarly, the predicted path A of the vehicle based on the yaw rate Γ (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 route AC after t _m seconds 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) Further, since it is Γ = v / R ...... (2 ), (1), equation (2), x _m = L ²・ Γ / 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, the difference e (e = x _l of the deviation x _Omega and x _m which is the calculated
+ X _m ), the yaw rate ΔΓ to be corrected of the vehicle is determined according to the following equation.

ΔΓ = 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 is controlled to join the vehicle to the target route OC. The target amount 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) Γ ( 6) is obtained. Here, l is the wheelbase of the vehicle.

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

Δδ = (l / v) ΔΓ (7) Here, the general formula l (1+
Considering Kv ² ), equation (7) becomes Δδ = ΔΓ ｛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 tire angle for joining the vehicle to 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 ′ from the control unit 5,
The driving of the steering is appropriately performed by the steering driving unit 10, and the steering is performed such that the vehicle joins the target route OC.

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 at the point P joins the target route OC, the shorter the traveling route is.
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 merges with 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 vehicle travels, the vehicle follows the target route OC set in the travelable area sequentially recognized in each control cycle. The control of the steering angle for running the vehicle is continuously performed.

In addition, as means for determining a control target amount of a steering angle for causing the vehicle to travel following the target route OC, other means for determining a position deviation of the vehicle with respect to the target route and an angle deviation of the traveling direction of the vehicle with respect to the target route are included. A means for obtaining a steering angle control target amount such that both or one of them converges to zero, or a target value of a yaw rate or a lateral load necessary to cause the vehicle to travel following the target route OC is set to a predetermined value. It calculates by calculation, calculates the steering angle correction amount in accordance with the deviation between the calculated target value and the current yaw rate or lateral load detection value, and obtains the control target amount from the current steering angle. Means and the like are widely applied.

In the present invention, in such an automatic traveling device, the yaw rate of the vehicle when it is assumed that the vehicle travels on the target route OC set as described above at the currently detected vehicle speed v is calculated by a predetermined calculation. A means for determining, a means for setting a limit value of the yaw rate, and a means for correcting the target route OC so that the yaw rate obtained by the calculation does not exceed the limit value are employed.

Each of those means is specifically, in the control unit 5,
It is executed as follows.

Drivable area RA recognized by the above-described image processing
In practice, the target route OC set in is represented by a sequence of points positioned on XY coordinates, as shown in FIG.

The road edges E1, E on both sides in the travelable area RA
Although 2 is actually positioned on the XY coordinates by a point sequence, the road edges E1 and E2 are indicated by continuous lines for convenience.

First, as shown in FIG. 5, the control unit 5 performs the actual travel of the vehicle on the target route OC set uniformly in the travelable area RA without any consideration of the dynamic load applied to the vehicle. In order to perform the smoothing, a smoothing process for smoothing the curved portion of the target route OC is performed.

As the smoothing process, the positions of three to five points before and after each point on the target route OC are averaged.

FIG. 9 shows the smoothed target route OC '.
Is shown.

Note that this smoothing process is not always necessary when implementing the present invention.

Next, the control unit 5 sets a limit value ヨ ー_L of the yaw rate when the vehicle travels following the target route OC ′ from the recognized road surface state of the travelable area RA.

At this time, for example, the limit value _{ＬL of the} yaw rate coming to the vehicle is appropriately set according to the degree of wetness or dryness of the road surface.

The degree of wetness or dryness of the road surface may be determined, for example, according to the brightness of an image when the travelable area RA is captured by the video camera.

In addition, the maximum allowable value Γ _max of the yaw rate of the vehicle according to the degree of wetness or dryness of the road surface is actually measured in advance, a characteristic as shown in FIG. 10 is created, and data of the characteristic is registered in the memory. , detected the maximum allowable value of the yaw rate of the time according to the degree of wetting of the road from the memory, the read maximum allowable value the limit value gamma _L
You may make it set as.

Next, based on the position data (x _n , y _n ) of each point on the target route OC ′, the control unit 5 determines the angle θ _n (n = 1, 2, 3,...) Of the point sequence with respect to the Y-axis direction. ) Is calculated according to the following equation.

θ _n = tan ⁻¹ {(x _n −x _n−1 ) / (y _n −y _n−1 )} (10) Here, the current traveling direction of the vehicle 11 at the point P is represented by the Y axis. Direction.

Then, the control unit 5, the yaw rate gamma _n of the vehicle at each point on the assumption that the travel target course OC 'above with a vehicle speed v that is currently detected in the point P is calculated according to the following equation.

_{Ｎ n} (θ _n -θ _n-1 ) / Δt _n (11) Then, Δt _n is given by the following equation.

_{Δt n = l n / v ......} (12) Next, the control unit 5 determines whether the yaw rate gamma _n at each point on the target course OC 'exceeds the limit value gamma _L.

Then, as shown in FIG. 11, portions (indicated in the figure shaded) which gamma _n exceeds the gamma _n, as shown in FIG. 12, for each point in the over portion yaw rate Γ
The yaw rate of each point on the target route OC 'is corrected by averaging the yaw rate of each point before and after the vicinity of the over portion so that _n becomes equal to or less than the limit value _ＬL .

Finally, the control unit 5 calculates a corrected angle θ _n ′ at each point by integrating the corrected value of the yaw rate Γ _n ′ at each point of the target route OC ′ by Δt _n , and calculates the angle between the points. The position of each point on the target route OC 'is corrected so that the angle of the connecting line segment with respect to the Y-axis direction becomes the value of? _N '.

In FIG. 13 shows the target route OC 'yaw rate is modified so as not to exceed the limit value gamma _L at each point.

Here, the position data of each point in the corrected target route OC "on _{(x n ', y n'} ) is given by the following equation.

The steering angle control described above is performed on the corrected target route OC ″ so that the vehicle travels following the target route OC ″.

As described above, according to the present invention, prior to control of the steering angle at which the vehicle travels following the target route, the yaw rate of the vehicle when traveling on the target route is determined according to the road surface condition of the travelable area and the like. The restriction can be made as appropriate, and the vehicle can follow the target route stably in accordance with the actual traveling of the vehicle.

As described above, in the automatic traveling device according to the present invention, the travelable area of the vehicle is recognized from image data obtained by capturing an area in the traveling direction of the vehicle by the imaging device attached to the vehicle. When the target route is set within the travelable area and the vehicle is controlled to follow the target route, the yaw rate of the vehicle assuming that the vehicle runs on the target route at the currently detected vehicle speed Is calculated by the arithmetic processing, and the yaw rate is corrected so that the yaw rate calculated by the calculation does not exceed the preset limit value in the travelable area, and the yaw rate is adjusted to the corrected yaw rate. The target route is modified so that an optimal target route with a limited yaw rate of the vehicle is set, and the vehicle that follows the target route runs stably. It has an excellent advantage that it can be used.

[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 of 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 sequence of points on the target route set within the travelable area, and FIG. 9 is a sequence of points on the target route subjected to smoothing processing. Fig. 10 shows the vehicle's swing depending on the degree of wetness or dryness of the road surface. The characteristic diagram of the maximum allowable rate, 11
FIG. 12 is a diagram showing a yaw rate distribution characteristic at each point on the target route, FIG. 12 is a diagram showing a yaw rate distribution characteristic at each point on the target route restricted by the present invention, and FIG. FIG. 14 is a diagram showing a point sequence of the target route corrected so as not to exceed the value, FIG. 14 is a diagram showing a line segment on the XY coordinate, and FIG. 15 is a Hough transform of the line segment in FIG. FIG. 9 is a diagram showing points on the ρ-θ coordinates at the time. 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, OC ' …… Smoothing target route, OC ″…
… Modified target route, P …… Vehicle position

Claims (1)

(57) [Claims] 1. A travelable area of a vehicle is recognized from image data obtained by capturing an area in a traveling direction of a vehicle by an imaging device mounted on the vehicle, and a target route is set in the recognized travelable area. In an automatic traveling apparatus which sets and controls the steering of the vehicle so as to follow the target route, a means for detecting the vehicle speed and a case where it is assumed that the vehicle travels on the target route at the detected vehicle speed Means for determining the yaw rate of the vehicle by arithmetic processing, means for setting a limit value of the yaw rate, and means for correcting the yaw rate so that the yaw rate determined by the arithmetic does not exceed the limit value within the travelable area. Means for correcting the target route so as to conform to the corrected yaw rate.