JP2844243B2 - 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.

In this type of automatic traveling device, an image pickup device mounted on a vehicle captures an image of a region in the traveling direction of the vehicle, samples the captured image, and processes the sampled image to perform data processing on the road edge. Extract continuous line segments such as, and based on the extracted line segments, recognize the travelable area in the traveling direction of the vehicle,
After setting a target route for vehicle travel in the recognized travelable area, a control target amount necessary for the vehicle to travel on the target route is determined based on the currently detected travel state of the vehicle. , And the vehicle is controlled so as to follow the target route according to the obtained control target amount (Japanese Patent Application No. Sho 63).
-199610).

In such an automatic traveling device, when performing traveling control of the vehicle so as to follow the target route, it is necessary to achieve coordination with the vehicle speed and to stabilize the traveling of the vehicle.

Objective The present invention has been made in consideration of the above points, and when performing traveling control of a vehicle to follow a target route set in a travelable area, when traveling on a curve portion in the target route, An automatic traveling apparatus that limits the vehicle speed to a maximum allowable speed determined from a value of a maximum allowable lateral load or a maximum allowable yaw rate that is set in advance according to the curvature of the curve portion and improves the stability of vehicle traveling. To provide.

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 1. An image processing unit 2 that performs data processing on an image captured by 1 to extract a continuous line segment such as a road edge, and recognizes a travelable area of a vehicle such as a road according to the extracted continuous line segment. A travelable area recognition unit 3, a target route setting unit 4 for setting a target route for vehicle travel in the recognized travelable area, a vehicle speed sensor 6 for detecting a travel speed v of the vehicle, a yaw accompanying the travel of the vehicle The running of the vehicle at that time is determined according to the output of each sensor such as a yaw rate sensor 7 for detecting a yaw rate で corresponding to a change in angular velocity in the direction and a steering angle sensor 8 for detecting a tire angle δ due to steering of the vehicle. A path control unit 5 for detecting a state and determining a steering control target amount required for the vehicle to travel on a target path based on the detected traveling state of the vehicle by a predetermined calculation process; A steering control unit 9 and a steering drive unit 10 for steering the vehicle according to the controlled target amount, and a maximum allowable speed of the vehicle traveling according to the curvature of the target route, and the vehicle speed does not exceed the maximum allowable speed. The vehicle speed control unit 11 controls the throttle 13 of the vehicle in accordance with a vehicle speed limit control command issued from the vehicle speed control unit 11 so as to drive the actuator 13 including a throttle motor and a brake solenoid valve. An actuator control unit 12 controls the degree and the brake pressure.

Actually, the image processing unit 2, the travelable area recognition unit 3, the target route setting unit 4, the route control unit 5, and the vehicle speed control unit 11 are replaced by a microcomputer. The computer also has a steering control unit 9, an actuator control unit
It is possible to include 12 as well.

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-high-sensitivity camera. Under the control of a computer, the plurality of video cameras are appropriately switched and used according to the state of a captured image at a vehicle speed 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 an image of a road edge in which the influence of 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 the fourteenth is the Y-axis direction.

In FIG. 4, the point P indicates the current position of the vehicle 14, and the center of the lower end of the imaging area of the video camera of the imaging unit 1 is set as the point P at the origin position 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 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 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 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 is controlled by the steering control of the vehicle under the control of the route control unit 5 so that the vehicle at the point P moves to the target route OC.
Shows a traveling route until the vehicle merges with the vehicle. The point O is the position where 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 a target route on the road is set, the route control unit 5 calculates a control target amount for causing the vehicle to join the target route by an arithmetic process as follows.

At this time, here, the control target is set to the steering angle of the vehicle,
A future traveling route is predicted from the traveling state of the currently detected vehicle, and a steering angle correction amount for the vehicle traveling on the target route is obtained from a deviation between the predicted route of the vehicle and the target route. The traveling control of the vehicle is performed according to the steering angle correction amount, with the steering angle correction amount as a control target amount.

Specifically, for example, a vehicle arrival position on the X axis at a certain distance in the Y axis direction when the current traveling direction is the Y axis direction is predicted from the traveling state of the vehicle, and the predicted position and the Y axis A steering angle correction amount corresponding to a deviation from a target position on the same X-axis on the target route at a certain distance in the direction is calculated.

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

First, the vehicle speed current vehicle speed v of the vehicle detected by the sensor 6 on the basis of the (m / s), the distance L (m) (L = v × t on Y axis after t _m seconds of the vehicle in the point P _m ) is determined, the deviation x _l, i.e. put out value instead of the usual proportional to the position on the target course OC at t _m seconds after between its Y C point and the target route away from the point P by a distance L on the axis OC It is.

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 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 − (v × t _m ) ² ｝ ^1/2 = R−R ｛1− (v × t _m / R ² ) ² ｝ ^1/2 where R≫v × t _{m When, x m ≒ R-R {} 1- (v × t m / R) 2/2} = v 2 × t m 2 / 2R = L 2 / 2R ... (1) the, Υ = v / R ... (2) Therefore, from Equations (1) and (2), x _m = L ² · Υ / 2v (3) Note that the sign of the yaw rate 例 え ば is, for example, a prediction 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 tire angle δ of the vehicle at the point P detected by the steering angle sensor 8 is acquired, and the vehicle is moved to the target route OC.
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, based on the relationship of equation (6), the correction amount Δδ of the tire angle corresponding to the yaw rate ΔΥ to be corrected of the vehicle
Is given by:

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 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 follows: δ ′ = δ + Δδ (9)

The steering control unit 9 outputs a drive command to the steering drive unit 10 in accordance with the control target amount δ ′ from the route control unit 5 and appropriately drives the steering by the steering drive unit 10 to move the vehicle to the target route OC. The steering that joins is performed.

The above processing is repeatedly performed in a predetermined control cycle in consideration of the time required for the processing in advance, and as the traveling of the vehicle progresses, it is set in the travelable area sequentially recognized in each control cycle. Target route OC
The running control of the vehicle that follows is continuously performed.

According to the present invention, in such an automatic traveling device, in particular, according to the vehicle characteristics such as the maximum allowable lateral load or the maximum allowable yaw rate of the vehicle, the vehicle is moved to the target route according to the curvature of the target route set in the travelable area. And means for determining the maximum permissible speed when the vehicle travels, and means for restricting the traveling speed of the vehicle so as to be equal to or less than the obtained maximum permissible speed.

Each of these means is specifically executed as follows.

First, the vehicle speed control unit 11 calculates the radius of curvature Rx of the target route on the basis of the data of the target route on the XY coordinates given from the target route setting unit 4, and calculates the vehicle radius registered in the internal memory in advance. Using the value of the maximum allowable lateral load Gmax as a characteristic, the curvature judgment Rx
The maximum allowable speed Vmax when passing through the target route is determined.

In addition, the maximum allowable yaw rate 車 両 max is registered in advance in the internal memory of the vehicle speed control unit 11 as the vehicle characteristic, and the maximum allowable yaw rate Υmax is calculated from the maximum allowable yaw rate Υmax by using the following calculation formula when the vehicle passes through the target path having the radius of curvature Rx. The speed Vmax may be obtained.

Υmax = Vmax / Rx (12) ∴Vmax = Rx · Υmax (13) The maximum allowable lateral load Gmax or the maximum allowable yaw rate Υmax of the vehicle depends on whether the road surface is wet or dry, as shown in FIG. It changes with the characteristics shown in FIG.

Therefore, in accordance with the characteristics shown in FIG. 8 or FIG. 9, each value of the maximum allowable lateral load Gmax or the maximum allowable yaw rate Υmax according to the degree of wetness or dryness of the road surface is previously obtained and registered in the memory, and The actual degree of wetness or dryness is detected, and a predetermined maximum allowable lateral load Gmax or maximum allowable yaw rate Υ is stored in the memory according to the detection result.
Read the value of max.

As a specific means for detecting the degree of wetness or dryness of the road surface, for example, as to determine the degree of wetness or dryness of the road surface according to the brightness of the image when the travelable area is captured by a video camera do it.

Then, the vehicle speed control unit 11 gives the actuator control unit 12 a control command for limiting the vehicle speed such that the running speed of the vehicle does not exceed the maximum allowable speed Vmax.

While reading the actual vehicle speed v detected by the vehicle speed sensor 6, the actuator control unit 12 appropriately drives the actuator 13 according to the vehicle speed limit control command so that the vehicle speed v does not exceed the maximum allowable speed Vmax. Thus, the throttle opening and the brake pressure of the vehicle are controlled.

 FIG. 12 shows a control flow in the present invention.

Effect As described above, in the automatic traveling device according to the present invention, the target route is set within the searched travelable region while searching for the travelable region in the traveling direction of the vehicle by the imaging device attached to the vehicle. When the vehicle is controlled to follow the target route, the vehicle speed is limited to a maximum allowable speed obtained from a value of a maximum allowable lateral load or a maximum allowable yaw rate set in advance according to the curvature of the target route. With such a configuration, there is an excellent advantage that a stable speed can be secured when traveling on a curved portion along the target route, and the stability of vehicle traveling can be improved.

[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 characteristic diagram of the maximum allowable lateral load of the vehicle depending on the degree of wetness or dryness of the road surface, and FIG. Characteristic diagram of maximum allowable yaw rate of vehicle according to degree, FIG. 10 shows XY Shows a line segment on the target, Figure 11 is a
FIG. 10 is a diagram showing points on the ρ-θ coordinates when the line segment in FIG. 10 is subjected to the Hough transform, and FIG. 12 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 ... Route control part, 6
………………………………………………………………………………………………………………………………………………………………………………………………………. , 14 …… Vehicle, RA… Drivable area, OC …… Target route

Claims (1)

(57) [Claims] 1. A means for taking an image of an area in the traveling direction of a vehicle by an imaging device attached to the vehicle, a means for extracting a continuous line segment by processing data of the taken image, and Means for recognizing a travelable area in the traveling direction of the vehicle based on the continuous line segment,
Means for setting a target route within the recognized travelable area; means for detecting the running state of the vehicle; and means necessary for the vehicle to travel on the target route based on the detected running state of the vehicle. In an automatic traveling apparatus comprising: means for obtaining a control target amount; and means for controlling the traveling of the vehicle according to the obtained control target amount, a value of a maximum allowable lateral load or a maximum allowable yaw rate corresponding to the curvature of the target path. Means for reading the maximum allowable speed when the vehicle travels on the target route by using the values read from the memory, and means for obtaining the maximum allowable speed. Means for limiting the running speed of the vehicle so that the speed is equal to or lower than the speed.