JP2757595B2 - Steering control device for autonomous vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering control device for an automatic traveling vehicle that travels based on a road linear index detected by a camera or the like.

[0002]

2. Description of the Related Art A camera or the like is installed in a vehicle to image a white line or a road shoulder of a road as a road linear index. There is already an issue proposed by the present applicant. In this proposal, an autonomous traveling vehicle that automatically performs steering control on a complicated curved road based on the positions of white lines at a large number of measurement points in front of the vehicle and that automatically travels is shown.

[0003]

According to the above-mentioned proposal, it is possible to correctly travel at the center position of the lane on an S-shaped road or the like, as compared with a case based on single point information comprising a white line position at a fixed distance in front of the vehicle. However, since the road linear index is detected from a white line drawn on the road, it cannot be recognized due to the shadow of a building on the white line, for example. When the position of the white line is out of the field of view of the camera, information for control is lost, and it is difficult to maintain accuracy.

In order to complement this, it is conceivable to set the number of measurement points particularly large so as to reduce the influence of missing information of one or two points. Since it is uncertain where such a discontinuity in the road alignment index occurs, it must be set densely over a wide range. However, the information at these additionally increased measurement points is usually useless and unnecessary, and may cause the control device to require an unduly large memory capacity and may also reduce the processing speed.

Therefore, the present invention generates control information with high accuracy for each measurement point even if a road line index such as a white line is locally interrupted without extremely increasing the number of measurement points in an autonomous vehicle. An object of the present invention is to provide a steering control device that obtains a highly reliable steering control output.

[0006]

For this reason, the present invention is based on FIG.
As shown in FIG. 1, a road alignment index detecting unit 10 mounted on a vehicle, and a road alignment index detected by the detecting unit 10,
Measuring means 11 for determining positions at measurement points set at a plurality of distances ahead on the vehicle coordinate axis and outputting position information for each measurement point, and control formula calculating means 12 for calculating a steering angle using the position information as an input value. And a membership function setting means for giving a predetermined degree of reliability to the input values of at least the adjacent measurement points for each of the above measurement points; and a steering actuator is operated based on the output of the control expression calculation means. A steering driving unit 14, wherein the control formula calculating means 12 calculates the steering angle at one measurement point and includes the input value at another measurement point in accordance with the reliability.

[0007]

According to the steering control apparatus of the present invention, for each of a plurality of measurement points, the input value of the measurement point is input to the control equation relating to the measurement point, and the input value of another measurement point is input to the control equation. Is also calculated according to the reliability, and the steering angle at the measurement point is calculated. Therefore, even when the input value of one measurement point is not obtained, the steering angle applied to the one measurement point is calculated using the input values obtained at another measurement point adjacent to the measurement point. Therefore, highly accurate steering control is performed.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In an embodiment of the present invention, an automatic traveling vehicle 1
Is provided with a camera 3 at the front end of the vehicle body 2 for imaging a white line on a traveling road as shown in FIG.

As shown in FIG. 3, an image pickup section 101 including the camera 3, an image processing section 102 for processing an image pickup signal to detect a white line position at a preset measurement point, and a map information section A global driving control unit 104 connected to the control unit 103, a steering control unit 105, and a steering driving unit 14 are provided.

The map information section 103 stores map data on a route to be traveled, such as nodes and path information, and other information on maps. The global travel control unit 104 refers to the map information obtained by the map information unit 103 and, for example, as shown in FIG. 4, determines the travel reference line 21 of the vehicle on the determined travel road 20 on the left side of the road. Is determined to be the distance X from the white line 22 of FIG. This distance X can be made variable so that the vehicle can always travel in the center of the travel road even on a road where the road width changes.

In the steering control unit 105, the image processing unit 1
The steering angle of the vehicle steering wheel is determined based on the white line position information from 02 and the route information from the global traveling control unit 104, and the steering driving unit 14 operates the steering wheel actuator based on the steering angle. .

Next, control in this embodiment will be described with reference to FIG. First, in step 201, the imaging unit 1
01 captures a white line image with a camera on a traveling road ahead of the vehicle, and sends an image signal to the image processing unit 102. In step 202, the image processing unit 102 sets a specific position in front of the vehicle 1 in FIG. 4 (for example, a plurality of positions within a range of 5 m to 25 m in front of the vehicle) as a measurement point li (i = 1, 2, 3,..., N). The relative position xi (i) of the white line 22 with respect to the vehicle coordinate system
= 1, 2, 3,..., N) and outputs it as white line position information. Step 201 corresponds to the road alignment index detecting means of the present invention, and step 202 corresponds to the measuring means. FIG. 6 shows a road white line position ahead of the vehicle obtained as a result of the image processing.

Next, the steering control unit 105 calculates a steering angle as a control amount from the white line position information and the route information from the global traveling control unit 104. That is, each measurement point l
A control formula sli = Fli (xi) is set corresponding to i, and for example, a traveling reference line Xi (i) corresponding to each measurement point li
= 1, 2, 3,..., N)

(Equation 1) And is a function of the amount of displacement of the vehicle from the travel reference line 21.

[0014] First, in step 203, as the membership function setting means, for each measurement point, the reliability μli (j) (j = 1, j = 1) for the input value of each measurement point including the measurement point.
2, 3,..., N) are set. That is, here, sli
Has a certain degree of reliability. If this reliability is expressed by a membership function Mi (i = 1, 2, 3,..., N), the control equation of sli = Fli (xi) is conventionally expressed by the measurement point li as shown in FIG. Only for input values at
1.0, and the reliability is 0 with respect to other input values. On the other hand, as shown in FIG. 7A, the membership function Mi has a width W before and after the measurement point li. It is set so that the reliability is given to the input value of the measurement point.

According to the example of FIG. 7A, the measurement point l
A membership function M with a reliability of 1.0 for an input value of 1
1 gives a reliability of 0.5 to the input value of the measurement point l2.

Next, at step 204, the control formula of each measurement point is calculated by the weighting method of fuzzy logic.

(Equation 2) Is calculated.

If this is shown by specific numbers with reference to FIG. 7A, the control formula sl2 = Fl2 for the measurement point l2 will be described.
Regarding (x), its membership function M2 is
For the input value of 1, a reliability of 0.5, a reliability of 1.0 at the measurement point l2, and a reliability of 0.5 at the measurement point l3,

(Equation 3) Becomes

At this time, when data of any measurement point is not obtained, the term is omitted, and when the data is an abnormal value, the reliability is set to 0 and the term is removed. Similarly, Sl1, Sl3,... Are calculated.

The Sl1, Sl2, Sl3,... Corresponding to the measurement points thus obtained are averaged in step 205,

(Equation 4) As a result, the final steering angle S is obtained. Step 20
4 and step 205 constitute a control formula calculating means. Then, a signal of the steering angle S is obtained, and the steering drive unit 14 operates the actuator.

With the above configuration, for example, as shown in FIG. 8, the white line 22a at the measurement point l1
Even if the position shifts out of the field of view of the camera, according to FIG. 7A, the membership function M1 having a reliability of 1.0 for the input value of l1 is 0 for the input value of the measurement point l2. .5, the position information at other measurement points can be effectively utilized, and a highly accurate steering angle can be obtained.

The same applies to the case where the white line captured by the camera is interrupted due to the shadow of a standing tree or building, and FIG. 9 shows a case where the white line 22b at the measurement point l4 is not recognized. Does not occur, but the value of the control equation sl4 = F14 (x) for the measurement point l4 is obtained from the input values of the measurement points l3 and l5. That is, by substituting the x value of the measurement point l3 and the x value of l5 into the equation of Fl4, sl43 = Fl4 (x3
) And sl45 = Fl4 (x5) are calculated, and using these and the reliability of 0.5 for l3 and the reliability of 0.5 for l5, Sl4 = (0.5 * s143 + 0.5 * s).
l45) / (0.5 + 0.5).

As described above, in this embodiment, a plurality of measurement points of the white line 22 are set, the effective range of the input value of each measurement point is expanded by the membership function, and the control formula at each measurement point is changed to another. Calculated by adding the weighted value to the input value of the measurement point, even if the road white line at a certain measurement point goes out of the field of view of the camera or the white line is interrupted by the shade, the white line data of the other measurement point , The steering angle can be determined with high accuracy.

In the above embodiment, the control equation sli at each measurement point li is a function of the displacement (Xi-xi) of the vehicle from the travel reference line 21.

(Equation 5) Can be used as a function of the time series change of the white line position.

In FIG. 7A, the reliability is given only to the immediately adjacent measurement points. However, the reliability is given to the input values of a plurality of measurement points including the adjacent ones by increasing the width. It may be. At this time, the width W of the membership function
Can be changed according to the curvature of the road alignment represented by the white line 22. That is, when the curvature is small, the change of the white line position is not so large even if the interval between the measurement points is considerable, so that even if the width W is set large, there is no deviation in the interpolation result when white line information is lost. If there is a certain measurement point interval, the change in the position of the white line increases as the curvature increases, so that the membership width W can be reduced to maintain an arbitrary predetermined accuracy.

In the above embodiment, the white line 22 drawn on the left side of the road is used as the road linear index, but the white line 23 on the right side may be used instead, or the road 20 of the traveling path 20 obtained from the left and right white lines may be used. The control formula sli is set by adding the width to the control parameter, and more accurate automatic traveling can be obtained.

[0026]

As described above, the present invention has a membership function setting means for giving a predetermined reliability to the input values of at least adjacent measurement points for each of a plurality of measurement points. In calculating the steering angle at one measurement point, the input value at the other measurement point is included in accordance with the reliability, so that a road linear index such as a white line on the traveling road is calculated from the visual field of the detection unit. Even if the input value of one measurement point cannot be obtained because it is off or the road linear index is not recognized in the shade, the input value obtained at another measurement point adjacent to that measurement point is The steering angle at the one measurement point is calculated using the data, and data on each measurement point is not lost. Therefore, automatic traveling with high accuracy is always achieved even on a complicated curved road.

Also, since the input values of the other measurement points are included in the control formula for each measurement point and are interpolated with each other, the accuracy level conventionally requiring a large number of measurement points can be obtained with a smaller number of measurement points. The advantage is that the processing speed is high.

Further, when means for setting a travel reference line is provided, and the control formula calculating means calculates the steering angle based on the displacement deviation of the vehicle from the road linear index position and the travel reference line, Based on the reference line, it is possible to travel on an arbitrary traveling road, and the control formula can be simplified, thereby further improving the processing speed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of the present invention.

FIG. 2 is an explanatory diagram showing an external appearance of an automatic traveling vehicle.

FIG. 3 is a block diagram showing an embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a relationship between a vehicle and a traveling road.

FIG. 5 is a diagram showing a control flow in the embodiment.

FIG. 6 is an explanatory diagram of image data.

FIG. 7 is an explanatory diagram of a membership function.

FIG. 8 is an explanatory diagram of image data.

FIG. 9 is an explanatory diagram of image data.

[Explanation of symbols]

 Reference Signs List 3 camera 10 road linear index detecting means 11 measuring means 12 control formula calculating means 13 membership function setting means 14 steering drive unit 20 running path 21 running reference lines 22, 22a, 22b, 23 white line 101 imaging unit 102 image processing unit 103 map Information section 104 global traveling control section 105 steering control section Mi membership function μ reliability li measurement point

Claims (5)

(57) [Claims] 1. A road linear index detecting means mounted on a vehicle, and a position of a road linear index detected by the detecting means at measurement points set at a plurality of distances in front of a vehicle coordinate axis is determined. Measuring means for outputting position information for each measurement point, control expression calculating means for calculating a steering angle using the position information as an input value, and a predetermined value for each of the measurement points with respect to an input value of at least an adjacent measurement point. A membership function setting means for giving a degree of reliability; and a steering drive unit for operating a steering actuator based on an output of the control expression calculation means, wherein the control expression calculation means calculates a steering angle at one measurement point. , An input value for another measurement point is calculated according to the reliability. 2. The apparatus according to claim 1, wherein said road linear index detecting means has a camera for capturing an image of a white line on a traveling road, and said measuring means includes an image processing unit for measuring a position of said white line. A steering control device for an autonomous vehicle. 3. The control formula calculating means calculates a steering angle of the one measuring point by a weighting method in which an input value of each measuring point is multiplied by reliability.
The steering control device for an automatic traveling vehicle according to the above. 4. The automatic traveling vehicle according to claim 3, wherein the control formula calculating means outputs a sum average of the steering angles calculated for each of the plurality of measurement points. Steering control device. 5. A road linear index detecting means having a camera mounted on a vehicle and imaging a white line on a traveling road, and an image processing unit for measuring the position of the white line at measurement points set at a plurality of distances ahead on a vehicle coordinate axis. Measuring means, a reference line setting means for setting a traveling reference line on a traveling road, and an output of the measuring means and the reference line setting means as input values, and a steering angle based on a displacement deviation amount from the traveling reference line. Control formula calculating means for calculating, membership function setting means for giving a predetermined degree of reliability to the input value of at least each adjacent measuring point for each of the measuring points, and steering based on the output of the control formula calculating means A steering drive unit for operating the actuators of the plurality of measurement points, wherein the control formula calculation means transmits, for each of the plurality of measurement points, a steering angle applied to the measurement points to an input value of each measurement point. A steering control device for an automatic traveling vehicle, wherein a steering weight is calculated by a weighted weighting method multiplied by a degree of reliability, and the sum of the calculated steering angles is used as an output.