JP2844236B2 - 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.

2. Description of the Related Art Conventionally, in an automatic traveling apparatus of this type, an image pickup device mounted on a vehicle captures an image of a region in a traveling direction of the vehicle, and a road edge is obtained based on image data obtained by sampling the captured image. After extracting a continuous line segment such as a line segment, based on the extracted line segment, a travelable area in the traveling direction of the vehicle is recognized, and a target route for vehicle travel is set in the recognized travelable area. In order to join the vehicle to the target point set on the target route according to the running state of the vehicle such as the currently detected steering angle and yaw rate of the vehicle (the change in the angular velocity in the yaw direction due to the running of the vehicle). A required steering angle control target amount is determined by a predetermined calculation, and a steering angle control that causes the vehicle to travel along a target route according to the determined control target amount is performed. And so as to sequentially performed with a control period (see Japanese Patent Application No. Sho 63-199610).

When the target point is set, the vehicle speed is detected, and the detected vehicle speed is multiplied by a preset time (hereinafter referred to as a predicted time). The target point is set.

However, in such an automatic traveling device, the lower the vehicle speed is, the shorter the distance for setting the target point on the target route is, and the current position of the vehicle is displaced in the lateral direction with respect to the target route. In such a case, if the distance is short, the control target amount of the steering angle increases.

Therefore, if the vehicle speed becomes too low, the steering at the time when the vehicle joins the target point becomes sharp, and the running of the vehicle for following the target route becomes unstable.

In addition, the higher the vehicle speed, the longer the distance for setting the target point on the target route. Therefore, if the vehicle speed is too high, the distance at that time exceeds the drivable area recognized in the current control cycle. As a result, it becomes impossible to set a target point for the target route set in the travelable area.

An object of the present invention is to set a target point at a position on a target path according to a distance proportionally obtained according to a vehicle speed and to merge a vehicle with the target point. When controlling the steering angle, the vehicle speed is too low to perform a sharp steering, or the vehicle speed is too high to set the target point on the target route, It is an object of the present invention to provide an automatic traveling apparatus in which an optimal target point is always set for the vehicle so that the vehicle following the target path can stably travel.

Configuration 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 according to the extracted continuous line segment. And the like, a travelable area recognizing unit 3 for recognizing a travelable area of the vehicle, a target route setting unit 4 for setting a target route for vehicle travel in the recognized travelable area, and detecting a traveling speed v of the vehicle. Sensors such as a vehicle speed sensor 6, a yaw rate sensor 7 for detecting a yaw rate あ る, which is a change in angular velocity 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. The running state of the vehicle at that time is detected according to the force, and a control target amount of the steering angle required for the vehicle to travel on the target route is calculated based on the detected running state of the vehicle in a predetermined calculation process. As well as
A control unit 5 for performing centralized control of the entire automatic traveling device
And a steering control section 9 and a steering drive section 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. 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 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-level representation may be performed in which the density of an image is expressed.

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, as shown in FIG. 2, information on a continuous line segment of a road edge 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 coordinate 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 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. It is recognized as the vehicle travelable area RA on the XY coordinates when the traveling direction of 11 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 becomes the optimum travel route of the vehicle speed 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 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 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 reduced 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.

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 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.

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. The amount is obtained, and the control target amount is calculated from the steering angle correction amount.

At this time, in the present invention, in particular, the vehicle arrival point of the vehicle on the predicted route after the preset predicted time is determined from the currently detected vehicle speed, and the distance calculated by multiplying the predicted time by the vehicle speed is calculated. Accordingly, a target point at which the vehicle merges is set at a position on the target route ahead of the vehicle, and a steering angle correction amount is obtained according to a deviation between the target point and a predicted arrival point of the vehicle.

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

First, an estimated time t set in advance to the current vehicle speed v (m / s) of the vehicle 11 detected by the vehicle speed sensor 6
_m distance by multiplying (in seconds) L (m) (L = t m ×
v) is obtained, a point C is determined at a position away from the point P by a distance L in the Y-axis direction, and the target point O is set at the same position on the target path OC on the X-axis as the point C.

Then, a value proportional to the deviation x ₁ on the X-axis between the points C and O, that is, the position of the target point O set on the target path OC after t _m seconds is obtained.

Similarly, the predicted route AC of the vehicle 11 is calculated based on the current yaw rate Υ (rad / s) detected by the yaw rate sensor 7, and the deviation x _m between the point C and the predicted route AC on the X axis is calculated. That is, a value proportional to the position of the arrival point M of the vehicle on the predicted route AC after _tm 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− (LR) ² ｝ ^1/2 where R こ こ L, x _m ≒ R−R ｛1− ( ^{L-R) 2/2}} = L 2 / 2R ...... (1) Further, since it is Υ = v / R ...... (2 ), (1), equation (2), 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
Considering (1 + Kv ² ), Δδ = ΔΥ ｛l (1 + Kv ² ) / v｝ (8) from equation (7).

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 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 ′ 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.

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

The present invention particularly relates to such an automatic traveling device,
When setting the target point O on the target route OC in accordance with the distance L obtained by multiplying the vehicle speed v by the predicted time t _m , the distance L becomes extremely short because the vehicle speed v is too low, and a sudden steering Or the distance L becomes extremely long because the vehicle speed v is too high, which makes it impossible to set a target point on the target path beyond the currently recognized travelable area RA. When the vehicle speed v is too low or too high, a certain restriction is imposed on the setting of the distance L so that there is no vehicle speed v.

That is, as shown in FIG. 8, when there is a lateral displacement (X-axis direction) between the vehicle 11 at the point P and the target route OC, if the vehicle speed v is too low, the predicted time t _m , the distance L obtained by multiplying by _m becomes extremely short. Therefore, the control target amount δ ′ of the steering angle when the vehicle 11 joins the target point O set on the target route OC according to the distance L becomes It becomes large, and the steering at that time becomes steep.

Therefore, the vehicle 11 deviates from the target route OC after being merged with the target point O by the sharp steering, and the traveling trajectory when the vehicle 11 travels following the target route OC becomes zigzag. This is the same as a decrease in the limit gain, and the running of the vehicle becomes unstable.

The control target amount δ ′ of the steering angle corresponding to the distance L is determined by the vehicle
It becomes proportionally larger according to the lateral displacement d between the target 11 and the target route OC. As the displacement d increases, the steering of the vehicle 11 to join the target point O becomes steeper.

Therefore, in the present invention, as shown in FIG.
Displacement d between the target and the target route OC (OC1, OC2, OC3) in the horizontal direction
Minimum setting value Lmin of distance L according to the size of (d1, d2, d3)
(Lmin ₁ , Lmin ₂ , Lmin ₃ ) are determined in advance, and a limit is imposed on the setting of the distance L when the vehicle speed v is too low.

The setting of the distance L is specifically limited as follows.

Now, for example, as shown in FIG. 10, a lateral displacement d (d1, d2, d3) between the vehicle 1 and the target route OC is used as a parameter, and a lower limit is set in accordance with the value of the displacement d. the value of the vehicle speed is set as a threshold _{v L (v L1, v L2} , v L3) minimum setting value corresponding to _{Lmin (Lmin 1, Lmin 2,} Lmin 3), in the internal advance in the memory of the controller 5 Register.

The control unit 5 controls the vehicle 11 and the target route on the XY coordinates.
Obtain the position deviation d on the basis of the position data of the OC, its the obtained d value out comparatively threshold v _L of lower limit in accordance with, the vehicle speed v that is currently detected is too low, it is a lower limit when equal to or less than the threshold value v _L, the minimum setting value Lmin corresponding to the threshold v _L at that time is read from the memory, the distance L for setting a target point O on the target course OC is the It is set to be equal to the read minimum setting value Lmin.

As described above, according to the present invention, even when the vehicle speed v is too low, it is possible to smoothly join the vehicle to the target point set on the target route OC without abrupt steering, thereby obtaining a control gain. As a result, the vehicle following the target route OC can stably travel.

Further, as shown in FIG. 11, when the vehicle speed v is too high, it becomes the distance L is extremely long, obtained by multiplying the estimated time t _m, therefore the distance L is recognized in the current control cycle Beyond the available travel area RA,
It becomes impossible to set the target point O on the target route OC.

Therefore, in the present invention, when the vehicle speed v is too high, a limit is imposed on the setting of the distance L at that time.

Specifically, in the control unit 5, a maximum set value Lmax equal to the length a in the Y-axis direction of the travelable area RA recognized in the current control cycle is predetermined, and the currently detected vehicle speed v is determined. when it exceeds the threshold value v _H is the upper limit that is set in advance, 'defines the its target point O' target point O on the target course OC in accordance with the maximum setting value Lmax so as to merge the vehicle 11 to the Control of the steering angle.

In the present invention, when the vehicle speed v is too high, instead of limiting the distance L to the maximum set value Lmax as described above,
As shown in the figure, the virtual target point O ″ may be set at a position where the target route OC is extended, corresponding to the distance L exceeding the travelable area RA.

Specifically, the control unit 5, when it exceeds the threshold value v _H is the upper limit that the vehicle speed v that is currently detected is preset, determined by multiplying the estimated time t _m at that time the vehicle speed v based on the used distance L, obtains the position x _m on the X axis of the virtual target point O "by the following arithmetic expression.

x _m = L × b / a (10) where a is the length in the Y-axis direction of the travelable area RA recognized in the current control cycle, and b is set in the travelable area RA. Is the length of the end point of the target route OC in the X-axis direction.

Then, in the same manner as described above, a steering angle control target amount δ ′ that allows the vehicle 11 to join the virtual target point O ″ set on the XY coordinates is obtained, and the steering angle control of the vehicle 11 is performed. Is performed.

Thus, according to the present invention, even when the vehicle speed v is too high, the target point O ′ or the virtual target point O ″ is always set on the target route OC, and the vehicle 11 follows the target route OC. The control of the steering angle for running can be performed without interruption.

Therefore, it is possible to stably drive the vehicle following the target route OC with control of the steering angle which is not interrupted in each control cycle and has a good connection between the control cycles.

Effects As described above, in the automatic traveling device according to the present invention, while recognizing a travelable region based on data of an image obtained by imaging an area in the traveling direction of the vehicle by an imaging device attached to the vehicle, Setting a target route in the recognized travelable area, when performing steering control to merge the vehicle to a target point determined on the target route, by detecting the motion state of the vehicle including at least the vehicle speed,
After setting the position of the target point on the target path based on the detected motion state, the position of the target point is set to the minimum distance value so that sudden steering is not performed when the vehicle speed is too low. Limit the position of the target point to the maximum distance value so as not to go beyond the travelable area when the vehicle speed is too high, or set the virtual target point at a position where the target route is extended. Therefore, there is an excellent advantage that the target point is always set at an optimum position on the target route according to the vehicle speed, and the vehicle can stably follow the target route.

[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 traveling locus of the vehicle following the target route when the vehicle speed is too low, and FIG. 9 is a lateral direction of the vehicle with respect to the target route. The figure showing the setting state of the minimum distance value according to the magnitude of the positional deviation of FIG. 10 is a characteristic diagram of the minimum distance value set corresponding to the vehicle speed when the lateral displacement of the vehicle with respect to the target route is set as a parameter, and FIG. 11 is a target point on the target route when the vehicle speed is too high. FIG. 12 is a diagram showing a state of setting a distance for setting a virtual target point on the extension of the target route when the vehicle speed is too high.
FIG. 14 is a diagram showing a line segment on the XY coordinate, and FIG. 14 is a diagram showing a point on the ρ-θ coordinate when the line segment in FIG. 13 is subjected to the Hough transform. 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 drive unit 10, steering drive unit 11, vehicle, RA, travelable area, OC, target route, P ... Vehicle position, O, O '... Target point, O "... Virtual target point

Claims (3)

(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 attached to the vehicle, and a target route is set in the recognized travelable area. After setting the target point on the target route, in an automatic traveling device that performs steering control to merge the vehicle to the target point, by detecting the motion state of the vehicle including at least the vehicle speed, A means for setting the position of a target point on the target route based on the detected motion state is provided, and a threshold value of the lower limit of the vehicle speed according to the degree of lateral displacement of the vehicle with respect to the target route is determined in advance. A minimum distance value corresponding to each of the threshold values is determined in advance, and the positional deviation is obtained based on each position data between the vehicle and the target route on the XY coordinates, and detected by a vehicle speed sensor. When the vehicle speed falls below a threshold value corresponding to the degree of the obtained positional deviation, the position of the target point set on the target route becomes the minimum distance value set according to the threshold value. An automatic traveling device characterized in that: 2. A travelable area of a vehicle is recognized from image data obtained by capturing an area in a traveling direction of the vehicle by an imaging device attached to the vehicle, and a target route is set in the recognized travelable area. After setting the target point on the target route, in an automatic traveling device that performs steering control to join the vehicle to the target point, by detecting the motion state of the vehicle including at least the vehicle speed, Means for setting the position of the target point on the target route based on the detected motion state is determined, a maximum distance value equal to the length of the currently recognized travelable area is predetermined, and the upper limit of the vehicle speed is set. The threshold value is set in advance so that when the vehicle speed detected by the vehicle speed sensor exceeds the upper limit threshold value, the position of the target point set on the target route is set to the maximum distance value. Automatic traveling device to. 3. A travelable area of a vehicle is recognized from image data obtained by capturing an area in a traveling direction of the vehicle by an imaging device attached to the vehicle, and a target route is set in the recognized travelable area. After the setting, a target point is set on the target route, and in an automatic traveling apparatus that performs steering control so that the vehicle merges with the target point, the motion state of the vehicle including at least the vehicle speed is detected. Means for setting the position of the target point on the target route based on the detected motion state, and the position of the target point set based on the motion state of the vehicle exceeds the currently recognized travelable area. An automatic traveling apparatus, wherein a virtual target point is set at a position where the target route is extended, and steering control is performed so that the vehicle merges with the virtual target point.