JPH03233710A - Automatic traveling device - Google Patents

Abstract

PURPOSE:To ensure the stable run of a vehicle along a target route by setting a target point on the target route according to the distance obtained by multiplying a fixed estimated time by the velocity of the vehicle. CONSTITUTION:An image pickup part 1 containing a video camera, etc., is attached to a vehicle and image-pickups the areas spreading in the traveling direction of the vehicle. Then a vehicle velocity sensor 6 is added to detect the traveling velocity (v) of the vehicle together with an image processing part 2, a travelable area recognizing part 3, a target route setting part 4, and a control part 5 respectively in a microcomputer. Then a target point is set at a position on a target route preceding the vehicle by a distance obtained by multiplying a prescribed time by the velocity (v) detected by the sensor 6. Thus an optimum target point can always be set to the target route and the stable run of the vehicle is ensured along the target route.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to an automatic driving device that allows a vehicle to automatically travel while searching for a driving route.

Prior Art Recently, an automatic driving device has been developed that searches its own driving route, sets an optimal target route on the route, and controls the vehicle so that the vehicle travels on the target route. has been done.

Conventionally, in this type of automatic driving device, an imaging device attached to the vehicle captures an area in the direction of travel of the vehicle, and the road edge is determined based on image data obtained by sampling the captured image. Extract continuous line segments such as.

Based on the extracted line segment, the travelable area in the direction of travel of the vehicle is recognized, a target route for the vehicle is set within the recognized travelable area, and the currently detected steering angle of the vehicle is determined. , yaw rate (change in angular velocity in one direction due to vehicle travel), and other driving conditions of the vehicle. Obtained by the calculation.

In accordance with the obtained control target amount, the steering angle is controlled sequentially at a predetermined control period so that the vehicle follows the target route.
3-199610).

In addition, when setting a target point, the vehicle speed is detected, and the distance on the target route ahead of the vehicle is calculated by multiplying the detected vehicle speed by a preset time (hereinafter referred to as predicted time). I am trying to set a target point at the location.

However, in such an automatic driving device, the lower the vehicle speed, the shorter the distance for setting the target point on the target route, and the current position of the vehicle may deviate in the lateral direction with respect to the target route. If the distance is short, the target steering angle control amount will become large.

Therefore, if the vehicle speed becomes too low, the steering required to cause the vehicle to merge to the target point becomes abrupt, making the vehicle's running to follow the target route unstable.

In addition, as the vehicle speed increases, the distance required to set the target point on the target route becomes longer. Therefore, if the vehicle speed becomes too high, the distance at that time exceeds the drivable range recognized in the current control cycle. As a result, it becomes impossible to determine a target point for the target route set within the drivable area.

4 lights The present invention has been made in consideration of the above points.

When setting a target point at a position on a target route that follows a distance proportional to the vehicle speed and controlling the steering angle to merge the vehicle at that target point, the vehicle speed is too low and the steering angle is too sudden. Always set the optimal target point for the target route and follow the target route without causing a situation where the vehicle speed is too high and the target point cannot be set on the target route. An object of the present invention is to provide an automatic traveling device that allows a vehicle to run stably.

An embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

As shown in FIG. 1, the automatic traveling device according to the present invention includes an imaging unit 1 including a video camera or the like attached to the vehicle so as to be able to image an area in the direction of movement of the vehicle; an image processing unit 2 that samples an image captured by l and processes the data of the sampled image to extract continuous line segments such as road edges; A driveable area recognition unit 3 that recognizes a driveable area of a vehicle, such as a vehicle, a target route setting unit 4 that sets a target route for the vehicle within the recognized driveable area, and detects a vehicle running speed V. Vehicle speed sensor 6゜The yaw rate sensor 7 detects the yaw rate T, which is the change in angular velocity in one direction as the vehicle travels, and the steering angle sensor 8 detects the steering angle δ of the vehicle. Detecting the running state of the vehicle, and calculating a target steering angle control amount necessary for the vehicle to travel on the target route based on the detected running state of the vehicle, and using a predetermined calculation process;
It is composed of a control section 5 that performs centralized control of the entire automatic traveling system, and a steering control section 9 and a steering drive section IO that perform steering of the vehicle according to the determined control target amount.

Actually, there are 5 image processing units 2. The travelable area recognition section 3, target route setting section 4, and control section 5 are replaced by a microcomputer. It is also possible to include the steering control section 9 in the computer.

As a video camera in the imaging section I, II! ! In addition to semi-lenses, telephoto lenses and wide-angle lenses are installed to obtain images appropriate to the vehicle speed and road conditions, and for night use, infrared cameras and ultra-high-sensitivity cameras are also available. A plurality of special video cameras are provided, and under the control of a computer, the plurality of video cameras are appropriately switched and used according to the vehicle speed, the state of the captured image, etc.

Furthermore, it is also possible to arrange two video cameras with the same imaging characteristics in parallel to obtain binocular stereoscopic images.

Extraction of continuous line segments such as road edges in the image processing section 2 is performed as follows.

First, a captured image sent from the imaging unit 1 is sampled, and the sampled input image is subjected to differential processing to detect image edges. The automatic threshold setting circuit automatically sets the optimal threshold according to the degree of shading of the input image at that time, and binarizes the edge image.

In this case, the input image must be binarized first, and then
Differential processing may be performed for edge detection. Further, instead of performing binarization, multi-value conversion that expresses the shading of the image may be performed.

Next, based on the edge detected and binarized or multivalued processed image, the line segment on x-ys1g is converted to ρ-
By performing Hough transformation processing, which is a well-known method that performs gray coordinate transformation on points on the θ coordinate, it is possible to combine continuous point sequences and remove isolated points without continuity. For example, information on continuous line segments of road edges as shown in FIG. 2 is obtained.

Here, θ is the angle of a perpendicular drawn from a 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 on the X-Y coordinates shown in FIG. 13 appears as point 01 on the ρ-θ coordinates as shown in FIG. 14.

At this time, edge tracking processing may be performed based on the binarized processed image to extract edge portions of the image that have continuity.

In addition, l(ough
By performing a plurality of processes such as conversion processing and edge tracking processing in parallel, and making a comprehensive judgment based on the results of each process, it becomes possible to obtain road edge information with higher accuracy than in 2. Furthermore, if the above-mentioned process for extracting continuous image edges is performed while growing the region of the input image as the vehicle travels, it is possible to extract road edge information with higher accuracy. Become.

Since the image captured by the video camera in the imaging unit 1 is based on perspective projection, the driveable area recognition unit 3 converts the road edge image based on perspective projection as shown in FIG. 2 into the image as shown in FIG. 3. A projective transformation process is performed, which is a known method for converting into an image of road edges that eliminates the effects of perspective projection.

Note that the projective transformation characteristics are set in advance by the driveable area recognition unit 3↓; in accordance with the perspective projection characteristics of the video camera.

Then, the driveable area recognition unit 3 identifies continuous road edges El as shown in FIG.

It is easy to recognize the space between E2 as the drivable area RA of the vehicle in the X-Y coordinates when the traveling direction of the image part, image part, edge image direction, that is, the traveling direction of the vehicle is the Y-axis direction. The point indicates the current right position of the vehicle 11, and the video camera is set in advance with respect to the vehicle so that the center of the lower end of the imaging area by the video camera of the imaging unit l is located at the origin of the X-Y coordinate 1 as point P. Next, when the drivable area recognizing unit 3 recognizes the road in front of the vehicle, which is the drivable area, the target route setting unit 4 determines the location on the recognized road. A target route that is the optimal travel route for the vehicle is set as follows.

As will be explained later, it is desirable to set the target route in a way that is suitable for the vehicle's current driving conditions, taking into consideration the road shape and vehicle speed. It is uniformly set as follows depending on whether it is narrow or wide.

That is, when the target route setting unit 4 determines that the road is a wide track with a road width of a certain value or more.

For example, as shown in FIG. 4, in the case of a left-hand traffic road.

A target route OC is set along the reference edge on the left side of the road with a predetermined separation width W of about 1.5 m, for example.

Furthermore, if the target route setting unit 4 determines that the road is a narrow track with a width less than a certain level, the target route is set at the center of the road, although not particularly shown.

Then, data on the position of the set target route on the X-Y 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 x-y coordinates is determined by the magnification of the video camera in the imaging unit I.

In Figure 4, the trajectory from point P to point 0 is.

As will be described later, the vehicle is steered under the control of the control unit 5, thereby showing a travel route taken by the vehicle at point P until it merges with the target route OC. 0 points is ＼
This becomes the target point of the merging of the vehicle's target route OCA at that time.

It is also possible to detect the driving state of the vehicle and set an optimal target route for the vehicle on the road in accordance with the detected driving state as described below.

That is, in the target route setting section 4, for example.

The vehicle speed detected by the vehicle speed sensor 6 is read, and if the current vehicle speed is within the low speed range below a preset threshold, the road shape is changed as shown in FIG. 5(a). Set the target route OC to follow.

Similarly, if the vehicle speed at that time is within a high speed range exceeding a preset threshold, the vehicle is traveling on a winding road, as shown in FIG. 5(b).

A target route oc having a gentle curvature so that the lateral acceleration acting on the vehicle is reduced as much as possible is set within the road.

Next, once the target route on the road is set.

In the control unit 5, the control target amount of the steering angle for causing the vehicle to join the target route is determined as follows.

Here, the future travel route is predicted from the currently detected vehicle travel state, and based on the deviation between the vehicle's predicted route and the target route, the steering angle for the vehicle to travel on the target route is corrected. The control target amount is derived from the steering angle correction amount.

In this case, particularly in the present invention, the arrival point of the vehicle on the predicted route after a preset predicted time is determined from the currently detected vehicle speed, and the distance is calculated by multiplying the predicted time by the vehicle speed. A target point for merging the vehicle is set at a position on the target route ahead of the vehicle following the vehicle, and the amount of steering angle correction is determined according to the deviation between the target point and the predicted arrival point of the vehicle. .

Now, for example, as shown in FIG. 6, the vehicle 11 at point P
Let us consider the case where the route OC merges with the target route OC.

First, the distance 1-(m)(
L = tmXv) is calculated, and the distance ML from point P in the Y-axis direction is
The target point O is set at a position on the same X-axis as the target path OC on the same X-axis as the C position.

Then, a deviation XQ on the X-axis between the 0 points, that is, a value proportional to the position of the target point O set on the target path oC after tmm is calculated.

Similarly, the predicted route AC of the vehicle 11 is calculated based on the current yaw rate T (rad/s) detected by the yaw rate sensor 7, and the predicted route AC is calculated between the 0 point and the predicted route A.
The deviation xm on the X axis between C and C, that is, 1. A value proportional to the position of the arrival point M of the vehicle on the predicted route AC after n seconds is determined as follows.

Now, when the radius of the arc drawn by the predicted route AC is R,
xffl is given by the following equation.

X, n=R-(RJ-L")!'4=R-R(1-
(L/R)')' Here, if R is L, then XIT, :R-R(1-(L/R)'/2)=L'
/2R...(1) Also, since T = v/R... (2), from equations (1) and (2), xlT, =L' ・T/ 2 v ・−
(3) Note that the sign of the yaw rate T is positive when the predicted route AC curves to the left, for example.

Then, the difference e(e”X
Yaw rate ΔT of the vehicle to be corrected according to
is obtained according to the following formula.

ΔT=e The target amount δ' is determined as follows.

Now, with the relationship shown in Figure 7, When R>α.

δ==Q/R... (5) From equations (2) and (5), δ=(tragedy/v)T...(6) is obtained. Here, Q is the wheelbase.

Therefore, in view of the relationship in equation (6), the correction amount Δδ of the steering angle according to the yaw rate ΔT of the vehicle to be corrected is given by the quintic equation.

Δδ= (Q/v)ΔT (7) Here, the general formula for the steering angle with respect to the vehicle speed V is Q=Q(1+K
v'), from equation (7), Δδ=ΔT (Q(
1+Kv')/v)-(8).

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

Then, the control target amount δ' of the steering angle for causing the vehicle to join the target route ○C is obtained as δ'=δ+Δδ (9).

The steering control section 9 issues a drive command to the steering drive section 10 according to the control target amount δ' given from the control section 5, and the steering drive section 10 accordingly drives the steering wheel to move the vehicle toward the target path OC. Perform steering to merge.

The above processing is repeated at a predetermined control cycle, and as the vehicle progresses, the target route OC is set within the driveable area recognized sequentially at each control cycle. Driving control of the following vehicle is continuously performed.

The present invention relates to such an automatic traveling device.

In particular, when setting the target point ○ on the target route OC according to the distance obtained by multiplying the vehicle speed V by the predicted time tlTl, the distance lWL becomes extremely short because the vehicle speed V is too low, resulting in a sudden This may become a factor in steering, or the distance may become extremely long due to the vehicle speed V being too high, which may cause the target point to be set on the target route beyond the currently recognized drivable area RA. To prevent this from occurring, a certain limit is imposed on the distance setting when the vehicle speed V is too low or too high.

That is, as shown in FIG. 8, there is a positional deviation d in the lateral direction (X-axis direction) between the vehicle It at point P and the target route OC.
If the vehicle speed V is too low, the predicted time tl
The distance obtained by multiplying by Tl becomes extremely short, so the target route o is changed according to the distance ML.
The control target amount δ' of the steering angle when the vehicle 11 merges with the target point ○ set on C becomes large, and the steering at that time becomes abrupt.

Therefore, after the vehicle 11 merges with the target point O due to sudden steering, the vehicle 11 deviates from the target route ○C, and the vehicle 11
When the vehicle is driven to follow the target route ○C, the travel trajectory becomes zigzag, which is equivalent to a decrease in the control gain, and the vehicle travel becomes unstable.

Further, the control target amount δ' of the steering angle according to the distance JIL is.

The positional deviation d in the lateral direction between the vehicle 11 and the target route QC increases proportionally, and the greater the positional deviation d, the steeper the steering of the vehicle 11 to merge with the target point O becomes.

Therefore, in the present invention, as shown in FIG.
The minimum set value L ll1n (Lcinl
, Lmin2, Lmin3) are determined in advance, and restrictions are imposed on the distance setting when the vehicle speed V is too low.

Specifically, the distance setting is restricted as follows.

Now, for example, as shown in FIG. 10, the lateral positional deviation d (cll, d2
．． d3) as a parameter, the vehicle speed VL (
The minimum setting value La1n (Lmin+, Lmin2 e
The value of Lwin3) is registered in advance in the internal memory of the control unit 5.

The control unit 5 calculates the positional deviation d based on the positional data of the vehicle 11 and the target route OC on the X-Y coordinates,
The lower limit threshold VL is calculated according to the obtained d value, and when the currently detected vehicle speed V is too low and is below the lower limit threshold VL, the threshold value at that time is calculated. The minimum set value L min corresponding to the value VL is read out from the memory, and the distance ML for setting the target point ○ on the target route OC is the read minimum set value L wi
Make it equal to n.

As described above, according to the present invention, even if the vehicle speed V is too low, the vehicle can smoothly merge to the target point set on the target route OC without sudden steering, and the control gain can be increased. This makes it possible to make the vehicle run stably while following the target route ○C.

Furthermore, as shown in Fig. 11, if the vehicle speed V is too high, the distance obtained by multiplying it by the predicted time tlT+ becomes extremely long, so that the distance cannot be recognized in the current control cycle. It becomes impossible to set the target point ○ on the target route OC beyond the travelable area RA.

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

Specifically, the control unit 5 predetermines a maximum setting value Lmax equal to the length a in the Y-axis direction of the travelable area RA recognized during the current control cycle, and sets the currently detected vehicle speed V to When the preset upper limit threshold value vH is exceeded, a target point O' on the target route OC according to the maximum setting value Lmax is determined, and the target point 0'
The steering angle is controlled so as to cause the vehicle 11 to merge.

Furthermore, in the present invention, when the vehicle speed V is too high, instead of limiting the distance to the maximum set value L@ax as described above, as shown in FIG. Correspondingly, the virtual target point O# may be set at a position where the target route OC is extended.

Specifically, when the currently detected vehicle speed V exceeds a preset upper limit threshold V), the control unit 5 multiplies the vehicle speed V by the predicted time t, . Based on the distance determined by the above, the position xm of the virtual target point 0'' on the X-axis is determined using the following calculation formula.

xm=L This is the length of the end point of path ○C in the X-axis direction.

Then, in the same way as described above, the steering angle control target amount δ' that causes the vehicle ti to merge with the virtual target point ○" set on the X-Y coordinates is determined, and the steering angle control amount of the vehicle 11 is determined. will be held.

According to the present invention, even if the vehicle speed V is too high, the target point ○' or the virtual target point O'' is always set on the target route OC, and the vehicle 11 follows the target route ○C. It is possible to control the steering angle for driving the vehicle without interruption.

Therefore, there is no interruption in each control cycle.
Further, by controlling the steering angle with good connection between each control cycle, it becomes possible to stably drive the vehicle following the target route ○C.

Since the start of summer, the automatic driving device according to the present invention recognizes the drivable area based on image data obtained by capturing an area in the direction of travel of the vehicle with an imaging device attached to the vehicle, and recognizes the area in which the vehicle can travel. When setting a target route within the recognized drivable area and controlling the steering angle to merge the vehicle at the target point set on the target route,
A target point is set on the "target route" according to the distance obtained by multiplying the actual vehicle speed by a certain predicted time, and the above-mentioned method is set so that sudden steering will not be performed if the vehicle speed is too low. Limiting the distance to a preset minimum distance value, and limiting the distance to a preset maximum distance value or following the distance so that the vehicle does not exceed the drivable range when the vehicle speed is too high. A virtual target point is set at an extended position of the target route, and the target point is always set at the optimal position on the target route depending on the vehicle speed, stabilizing the running of the vehicle following the target route. It has the excellent advantage of being able to perform

[Brief explanation of drawings]

FIG. 1 is a block configuration diagram showing an embodiment of an automatic driving device according to the present invention, FIG. 2 is a diagram showing road line segments obtained by data processing an image captured by a video camera, and FIG. 3 is a diagram showing an image obtained by projective transformation of the image in FIG. Figures (a) and <b) are diagrams showing the target route set on the road when the vehicle is running at low speed and at high speed, respectively. Figure 6 is a diagram showing the relationship between the target route and the predicted route of the vehicle. Figure 7 is a diagram showing the relationship between the steering angle of the vehicle and its turning radius, Figure 8 is a diagram showing the traveling trajectory of the vehicle following the target route when the vehicle speed is too low, and Figure 9 is a diagram showing the lateral direction of the vehicle with respect to the target route. Fig. 10 shows the minimum distance value set corresponding to the vehicle speed when the lateral positional deviation of the vehicle with respect to the target route is taken as a parameter. Fig. 11 is a diagram showing how to set the distance to set the target point on the target route when the vehicle speed is too high, and Fig. 12 is a diagram showing the distance setting state for setting the target point on the target route when the vehicle speed is too high. Figure 13 is a diagram showing a line segment on the X-Y coordinates, and Figure 14 is a diagram showing a state in which the target and directness are set.
It is a diagram showing points on coordinates. l...Imaging unit 2...Image processing unit 3...Drivable area recognition unit 4...Target route setting unit 5...Control unit 6...Vehicle speed sensor 7...Yaw rate sensor
8... Rudder angle sensor 9... Steering control section l
O...Steering drive unit 11...Vehicle RA・
...Drivable area ○C...Target route P...Vehicle position [0,0'-...Target point O''...Virtual target point

Claims (1)

[Claims] 1. Vehicle travel on X-Y coordinates based on image data obtained by capturing an image of an area in the vehicle's traveling direction with an imaging device attached to the vehicle and sampling the captured image. The system recognizes the possible travel area, sets a target route within the recognized travelable area, sets a target point on the target route, and controls the steering angle to merge the vehicle at the target point. In this system, the target point is set at a position on the target route ahead of the vehicle that follows the distance obtained by multiplying the vehicle speed detected by the vehicle speed sensor by a preset time. Features an automatic driving device. 2. Predetermining in advance a lower limit threshold of vehicle speed according to the degree of lateral positional deviation of the vehicle with respect to the target route, and predetermining a minimum distance value corresponding to each of the threshold values,
The positional deviation is determined based on each positional data between the vehicle and the target route on the X-Y coordinates, and the vehicle speed detected by the vehicle speed sensor becomes less than a threshold value corresponding to the determined degree of positional deviation. 2. The automatic traveling device according to item 1 above, wherein the distance for setting a target point on the target route is limited to a minimum distance value corresponding to the threshold value. 3. A maximum distance value equal to the length of the currently recognized drivable area is predetermined, and an upper threshold value for vehicle speed is determined in advance, so that the vehicle speed detected by the vehicle speed sensor exceeds the upper threshold value. The automatic traveling device according to item 1, wherein the distance for setting the target point on the target route is limited to a maximum distance value when the target point is exceeded. 4. When the distance obtained by multiplying the vehicle speed detected by the vehicle speed sensor by a preset predicted time exceeds the length of the currently recognized drivable area, the target route is extended according to that distance. The automatic traveling system according to item 1 above, wherein a virtual target point is set at a location, and a steering angle for merging the vehicle at the virtual target point is controlled.