JP3393427B2 - Curve radius estimation device and automatic steering control system with curve radius estimation device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a curve radius estimating device and an automatic steering control system using the curve radius estimating device, and particularly to a curve radius suitable for use when a vehicle travels on a curve having a bank. The present invention relates to an automatic steering control system with an estimating device and a curve radius estimating device.

[0002]

2. Description of the Related Art In recent years, various technologies for assisting a driver such as a navigator system have been developed for automobiles, and further, a technical development for automatic driving in which a driver operates automatically on behalf of the driver. Is being promoted. The driver's driving operation is to grasp the road condition and the traveling condition of the vehicle and control the vehicle speed or steer according to the grasped road condition and traveling condition. Various functions need to be computerized or mechanized.

For example, in order to automate the steering of a vehicle, a mechanical function (that is,
Needless to say, a steering actuator) is required, but various functions for controlling the operation of the steering actuator are also required. That is, as described above, it is necessary to have a function of grasping the road condition on which the vehicle is traveling, that is, the curve condition of the traveling route ahead, the traveling condition of the vehicle, that is, the relative position of the vehicle to the traveling route, the vehicle speed, etc. Further, it is necessary to have a function of setting a target steering angle according to the grasped road conditions and vehicle traveling conditions and controlling the operation of the steering actuator based on the target steering angle.

In particular, in order to grasp the curve condition of the road ahead, as shown in FIG. 4, for example, a television camera (generally a CCD camera) for taking a picture of the road ahead of the vehicle on the vehicle 1.
2 is installed, a guide line such as a white line on the road is recognized from the image information captured by the television camera 2, and a curve radius (or curvature) of the road can be obtained from the recognized guide line. ing.

In this case, as shown in FIG. 5, since the original image photographed by the television camera 2 is a perspective image, it is once converted into a planar view (top view) image, and then guide lines are matched with circles, for example. Alternatively, the curve radius is obtained by geometrically calculating from the angle between the vehicle direction and the tangent to the guide line. For example, in Japanese Unexamined Patent Publication No. Sho 63-314623, the method, that is, two points out of the guide lines ahead of the vehicle recognized from the converted plane image are selected, and the tangents to the guide lines are obtained at these two points. , A technique for detecting the curvature of the guide line based on the angle formed by these tangents and the vehicle traveling direction is disclosed.

Regarding the recognition of the guide line, since the brightness is generally higher than that of a normal road surface, for example, the road image is searched for the brightness in the scanning line direction, and the part having the high brightness is set as the guide line candidate point. The guide line can be recognized from the guide line recognition information and the guide line candidate point information obtained in (1). For example, in Japanese Patent Laid-Open No. 7-85249, a lightness change is searched in the lateral direction in a white line search area based on image information, a portion having a very small lightness change is determined to be a road portion, and the lightness change is determined. There is disclosed a technique of recognizing a portion adjacent to a road portion having a very small number and having a large change in brightness as a white line.

[0007]

By the way, when detecting a curve radius or curvature of a road such as a road, the original image (see FIG. 5) from the television camera 2 mounted on the vehicle is basically used. The original image is premised on that the camera is horizontal in the left-right direction. However, when the vehicle is traveling on a curve with a bank, for example, the vehicle itself tilts left and right, so that the TV camera 2 itself fixed to the vehicle tilts left and right, and the original image obtained from the TV camera 2 is also tilted. It tilts left and right and is no longer horizontal. Thus, when the original image is no longer horizontal in the left-right direction, the horizontal image based on this original image (see FIG. 5) is distorted, and the curve radius obtained from the guide line in this horizontal image is also increased. There will be an error.

For example, FIG. 6 is a diagram showing a difference in the appearance of a curved road having a certain curve radius and a flat road and a bank road. Here, the result obtained by calculation of the original image obtained from the TV camera 2 when the curve radius is 140 m and the bank angle is inclined to the right by 7 ° is shown. The solid line shows the case of a bank road. As shown in the figure, it can be seen that the bank road is photographed at a higher position on the screen as it goes farther (the end of the curve) than on a flat road.

The broken line and the solid line in FIG. 6 indicate the white lines on the left and right of the lane, and the running target line of the vehicle is located at the left and right center of these white lines. FIG. 7 shows a traveling target line of the vehicle by converting the original image as shown in FIG. 6 into a horizontal image. The broken line shows the case of a flat road and the solid line shows the case of a bank road. As shown in the figure, on the bank road, the curve radius is recognized as being larger than the actual curve (broken line) at a portion far from the host vehicle, and as being smaller than the actual curve (broken line) at a portion closer to the host vehicle. , The traveling target line originally on an arc becomes an elliptical shape.

As described above, on the bank road, the curve radius to be recognized varies depending on the distance from the host vehicle (forward watching distance). FIG. 8 shows the characteristics of the recognition curve radius with respect to the forward watching distance. In the figure, the broken line shows the true curve radius, the solid line shows the recognition curve radius obtained based on the original image in the calculated bank road, ×
The mark indicates the recognition curve radius obtained based on the actual image processing.

As shown in the figure, the radius of recognition curve on the bank road becomes larger than the true curve radius at a distance farther than this, centering on a certain forward gaze distance, and at a distance shorter than this distance, the recognition curve radius on the bank road. It can be seen that is smaller than the true curve radius. It should be noted that FIG. 8 relates to the case where the camera is installed at a general position (for example, the rear surface of the rearview mirror) in a general passenger car, and it is considered that such characteristics differ depending on the vehicle model and the installation position of the camera. It is considered that the same tendency as in FIG. 8 appears in both cases.

As described above, since the original image is not horizontal in the left-right direction on the bank road, an error occurs in the curve radius recognized based on the original image according to the forward gaze distance. On the basis of the curve radius thus recognized, there arises a problem that the traveling target line of the vehicle is not appropriate. The present invention was devised in view of the above-mentioned problems, and made it possible to more accurately recognize the curve radius even on a bank road so that, for example, the travel target line of the vehicle can be set appropriately.
An object of the present invention is to provide a curve radius estimating device and an automatic steering control system with a vehicle curve radius estimating device.

[0013]

Therefore, the curve radius estimating apparatus of the present invention according to claim 1 is provided in a vehicle, and an image pickup means for picking up an image of a traveling path ahead of the vehicle, and the image pickup means are provided. In a curve radius estimation device having radius estimation means for estimating a curve radius of the road ahead based on the image information of, the bank angle of the road surface on which the vehicle is traveling is estimated at the time of imaging by the imaging means. A bank angle estimating means; and a curve radius correcting means for correcting the curve radius of the forward traveling road estimated by the radius estimating means based on the bank angle estimated by the bank angle estimating means. I am trying.

According to a second aspect of the present invention, there is provided the apparatus for estimating a curve radius according to the first aspect, wherein the bank angle estimating means has a lateral acceleration produced in the vehicle, a yaw rate produced in the vehicle, and The bank angle is estimated based on the vehicle speed of the vehicle. A curve radius estimating device according to a third aspect of the present invention is the device according to the first or second aspect, wherein the curve radius correcting means presets a bank angle-curve based on a change characteristic of the image with respect to the bank angle. It is characterized in that the radius of the curve is corrected using a radius map.

A curve radius estimating apparatus according to a fourth aspect of the present invention is the apparatus according to any one of the first to third aspects,
The radius estimation means estimates the curve radius of the traveling road from the characteristic image of the traveling road appearing on the planar view image after converting the image into the planar view image. An automatic steering control system with a vehicle curve radius estimating device according to a fifth aspect of the present invention includes an image pickup means which is mounted on a vehicle and which picks up an image of a road ahead of the vehicle, and image information from the image pickup means. A curve radius estimating device having radius estimating means for estimating a curve radius of the forward traveling path based on the
Target steering angle calculation means for calculating a target steering angle based on the curve radius of the forward traveling road estimated by the curve radius estimation device, and the vehicle based on the target steering angle calculated by the target steering angle calculation means In the automatic steering control system with a curve radius estimating device, which comprises an automatic steering control means for controlling the steering actuator,
The bank angle estimating means for estimating the bank angle of the road surface on which the vehicle is traveling at the time of image capturing by the image capturing means, and the bank angle estimated by the radius estimating means based on the bank angle estimated by the bank angle estimating means. It is characterized in that it is provided with a curve radius correction means for correcting the curve radius of the traveling path.

An automatic steering control system with a vehicle curve radius estimating device according to a sixth aspect of the present invention is the system according to the fifth aspect, wherein the target steering angle calculating means has the bank estimated by the bank angle estimating means. A target steering angle correcting means for correcting the target steering angle based on the curve radius by the correction steering angle corresponding to the lateral force generated in the vehicle by the bank angle and gravity based on the angle is provided.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIGS. 1 to 3 show an automatic steering control system with a vehicle curve radius estimating device as one embodiment of the present invention. Is. As shown in FIG. 1, the present automatic steering control system is based on a perspective view image information from the television camera 2 and the television camera 2 as an imaging unit that obtains a perspective image (front camera image) by capturing an image of the front of the vehicle. A curve radius estimating device 4 having a radius estimating means (target R estimating means) 3 for estimating the curve radius of the road ahead.
And a target steering angle calculating means 5 for calculating a target steering angle based on the curve radius estimated by the curve radius estimating device 4,
The automatic steering control means 7 controls the steering actuator 6 mounted on the vehicle based on the target steering angle calculated by the target steering angle calculation means 5 to automatically steer the vehicle.

Of these, the curve radius estimating device 4 will be described. In the curve radius estimation device 4, as shown in FIG. 5, an original image which is a perspective image is obtained from the TV camera 2 (see FIG. 4) fixed to the vehicle 1, and the original image is once viewed in a plan view (top view). Then, the target R estimation means 3 uses a known method such as matching the guide lines with a circle or geometrically calculating from the angle between the vehicle direction and the tangent of the guide line. , Find the curve radius.

However, when the vehicle is traveling on a curve with a bank, the television camera 2 is also inclined to the left and right due to the inclination of the vehicle itself to the left and right, and the original image obtained from the television camera 2 is also inclined to the left and right directions (see FIG. 6). Distortion) occurs in the horizontal image based on this original image (see FIG. 7). Therefore, the estimated curve radius R also has an error according to the bank degree (bank angle), and the curve radius R obtained from only the original image by the TV camera 2 is an apparent R (curve radius). It is not a true curve radius R anymore.

Therefore, in the present curve radius estimating device 4,
A curve radius correction means 8 for correcting the curve radius obtained from the guide line (for example, a white line) in this horizontal image according to the bank angle of the curved road on which the vehicle capturing the original image is running [correction 1]]. Is provided. The curve radius correction means 8 is provided as a functional part of the target R estimation means 3, but for the curve radius correction, the bank angle of the road surface on which the vehicle is running must be recognized. Therefore, the curve radius estimating device 4 is provided with the following bank angle estimating means 9.

The bank angle estimating means 9 detects the lateral acceleration (lateral G sensor detection value) generated in the vehicle by the lateral acceleration sensor (lateral G sensor) 10, and the yaw rate (lateral yaw rate) generated in the vehicle by the yaw rate sensor 11. Yaw rate detection value)
And the vehicle speed V detected by the vehicle speed sensor 12,
The bank angle (the time at which the original image was captured by the camera 2 or a bank angle close to this) is estimated.

Here, the principle of estimating the bank angle will be described. The bank angle estimating means 9 estimates the bank angle from the balance of the forces of the vehicles running on the bank road. That is, gravitational acceleration g and centrifugal acceleration are applied to the vehicle traveling on the bank road, as shown in FIG. These accelerations can be divided into a component perpendicular to the road surface and a component parallel to the road surface.The component perpendicular to the road surface is canceled by the road surface reaction force, and the component parallel to the road surface is divided into the road surface of the centrifugal acceleration. The parallel component A and the component B of the gravitational acceleration g parallel to the road surface act in opposite directions, and a combination of these (AB) as in the following equation (1) corresponds to the lateral G sensor detection value. .

(Horizontal G sensor detection value) = A−B (1) The component A of the centrifugal acceleration parallel to the road surface is expressed by the following equation (2) using the vehicle speed V and the yaw rate detection value. Gravity acceleration g
The component B parallel to the road surface can be expressed by the following equation (3) from the gravitational acceleration g and the bank angle θ. A = V · (yaw rate detection value) (2) B = g · sin θ (3) From equations (1) to (3), θ can be expressed by the following equation (4). .

Sin θ = [V · (yaw rate detection value) − (transverse G sensor detection value)] / g (4) In the bank angle estimating means 9, the bank angle θ is set to the vehicle speed V in this way. And the yaw rate detection value and the lateral G sensor detection value. Then, in the curve radius correction means 8, for example, an estimation error characteristic of the curve radius R with respect to the forward gaze distance as shown in FIG. Curve radius error (that is, the curve radius correction amount corresponding to the bank angle) is mapped (this map is called the bank angle-curve radius map), and based on this map, the bank angle θ and the forward gaze distance are calculated. The curve radius correction amount is obtained, and the curve radius (apparent R) obtained from the image information is corrected by this curve radius correction amount to obtain the corrected curve radius (correction R).

In the target steering angle calculating means 5, the curve radius (correction R) thus estimated by the curve radius estimating device 4 is obtained.
The target steering angle calculation means 5 is provided with a target steering angle correction means 13 for correcting the target steering angle [correction 2]]. The target steering angle correction means 13 is intended to correct the steering effect due to the gravity of the vehicle on the bank road.

That is, for example, when there is a bank with a right curve as shown in FIG. 2, this bank is lowered to the right, and the vehicle receives a lateral force in the right direction, that is, a turning direction due to gravity on the bank road. Therefore, the steering angle corresponding to the lateral force by this bank angle (this is called the corrected steering angle),
It is necessary to subtract and correct the target steering angle. The corrected steering angle in this case is the stability factor SF and the wheel base W.
B, the gravity g applied to the vehicle, and the bank angle θ can be used to express as in the following expression (5).

Corrected steering angle = SF · WB · g · sin θ (5) Therefore, in the target steering angle calculation means 5, the target steering based on the curve radius (corrected R) is expressed by the following equation (6). Correct the corners. Target steering angle = (target steering angle based on correction R) − (corrected steering angle) (6) Since the curve radius estimation device as one embodiment of the present invention is configured as described above, the bank When the vehicle is traveling on a road, the curve radius estimating device 4 corrects the curve radius obtained from above the image by the curve radius correcting means 8 according to the bank angle of the curved road on which the vehicle is traveling [correction 1]].
As a result, the curve radius becomes highly accurate with the influence of the bank angle corrected.

In particular, the bank angle θ of the curved road is calculated by the bank angle estimating means 9 by using the relationship expressed by the above equation (4).
Since it can be calculated from the vehicle speed V, the yaw rate detection value, and the lateral G sensor detection value, the bank angle θ can be reliably and easily obtained. For example, FIG. 3 shows the lateral shift amount with respect to the steering wheel operation (steering wheel angle) in correspondence with the horizontal axis (time). As shown by the solid line, by performing correction according to the bank angle (bank correction), the broken line It can be seen that the lateral shift amount of the vehicle is significantly reduced as compared with the case where the bank correction as shown in (4) is not performed. It should be noted that the portion where the broken line indicating the lateral shift amount is linear is a region where the lateral shift amount is large and cannot be measured, and it can be seen that an extremely large lateral shift occurs if the bank correction is not performed.

Since the accuracy of the curve radius is improved, in the present automatic steering control system equipped with this vehicle curve radius estimation device, even when the target steering angle of the vehicle is obtained based on this curve radius, the target steering angle is also calculated. The corner accuracy is improved, and automatic steering can be performed more appropriately. Further, in this automatic steering control system, the target steering angle correction means 13 subtracts and corrects the target steering angle by the steering angle (corrected steering angle) corresponding to the lateral force due to the bank angle.
The steering effect due to the effect of gravity on the bank road is now eliminated, and in this respect as well, the accuracy of the target steering angle is increased,
The automatic steering can be performed more appropriately.

Incidentally, depending on the bank angle and the vehicle, the steering angle (corrected steering angle) corresponding to the lateral force is small, so it is possible to omit the correction by this corrected steering angle. Also,
The vehicle curve radius estimation device can be used not only in the automatic steering control system, but for example, a device that performs feedforward control of the active suspension based on the curve radius of the forward traveling road or the vehicle speed, or the forward traveling road. It can also be used as a device for issuing an alarm for prompting the driver to decelerate based on the curve radius and the vehicle speed.

[0031]

As described in detail above, according to the curve radius estimating apparatus of the present invention as set forth in claim 1, the curve radius correcting means estimates the radius based on the bank angle estimated by the bank angle estimating means. Since the curve radius of the forward traveling path estimated by the means is corrected, there is an advantage that the curve radius can be accurately obtained based on the image information even on the bank road.

According to the curve radius estimating apparatus of the present invention as defined in claim 2, since the bank angle can be estimated easily and surely by the bank angle estimating means, the curve radius can be surely corrected based on the bank angle. This contributes to accurate estimation of the curve radius. According to the curve radius estimating device of the present invention as defined in claim 3, the curve radius can be easily corrected by the curve radius correcting means.

According to the curve radius estimating apparatus of the present invention as defined in claim 4, the radius estimating means estimates the curve radius of the traveling road after converting the image into a plan view image, so that the curve radius can be easily estimated. Can be done. Further, according to the automatic steering control system with a vehicle curve radius estimating device according to claim 5, in the curve radius estimating device, the radius estimation is performed by the curve radius correcting device based on the bank angle estimated by the bank angle estimating device. Since the curve radius of the forward traveling road estimated by the means is corrected, the curve radius can be accurately obtained based on the image information even on the bank road. Therefore, based on this curve radius, the target steering angle can be accurately set. Can be calculated, and there is an advantage that the automatic steering control can be appropriately performed.

According to the automatic steering control system with the vehicle curve radius estimating device of the sixth aspect, the target steering angle is corrected by the correction steering angle corresponding to the lateral force generated in the vehicle by the bank angle and gravity. Therefore, the target steering angle can be calculated, and the automatic steering control can be performed more appropriately.

[Brief description of drawings]

FIG. 1 is a block diagram showing a curve radius estimation device and an automatic steering control system with a vehicle curve radius estimation device according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining bank angle estimation by the curve radius estimation device as one embodiment of the present invention.

FIG. 3 is a diagram showing an effect of curve radius correction by the curve radius estimation device as one embodiment of the present invention.

FIG. 4 is a schematic side view of a vehicle for explaining a conventional curve radius estimation device.

FIG. 5 is a diagram illustrating a conventional curve radius estimation device.

FIG. 6 is a diagram illustrating a problem of a conventional curve radius estimation device, and is a diagram corresponding to an original image of a camera.

FIG. 7 is a diagram for explaining the problem of the conventional curve radius estimation device, and a diagram corresponding to a top view (plan view) converted from the original image.

FIG. 8 is a diagram for explaining a problem of a conventional curve radius estimation device, and is a diagram showing a recognition characteristic of a curve radius on a bank road.

[Explanation of symbols]

1 car body 2 Television camera as an imaging means 3 Radius estimating means (target R estimating means) 4 Curve radius estimation device 5 Target steering angle calculation means 6 Steering actuator 7 Automatic steering control means 8 Curve radius correction means 9 Bank angle estimation means 10 Lateral acceleration sensor (lateral G sensor) 11 Yaw rate sensor 12 vehicle speed sensor 13 Target steering angle correction means

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-8-5388 (JP, A) JP-A-7-311895 (JP, A) JP-A-7-78258 (JP, A) JP-A-8- 219786 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01B 11/00-11/30 G08G 1/16 G01C 21/00

Claims (6)

(57) [Claims] 1. A vehicle equipped with imaging means for imaging a road ahead of the vehicle, and radius estimation means for estimating a curve radius of the road ahead based on image information from the imaging means. In a curve radius estimation device, a bank angle estimating means for estimating a bank angle of a road surface on which the vehicle is traveling at the time of image capturing by the image capturing means, and the radius estimation based on the bank angle estimated by the bank angle estimating means. A curve radius estimating device, comprising: a curve radius correcting means for correcting the curve radius of the forward traveling path estimated by the means. 2. The bank angle estimating means estimates the bank angle based on a lateral acceleration generated in the vehicle, a yaw rate generated in the vehicle, and a vehicle speed of the vehicle. The curve radius estimating device according to claim 1. 3. The curve radius correction means corrects the curve radius by using a bank angle-curve radius map preset based on a change characteristic of the image with respect to the bank angle. The curve radius estimation device according to item 1 or 2. 4. The radius estimating means converts the image into a planar view image and then estimates a curve radius of the traveling road from a characteristic image of the traveling road appearing on the planar view image. The curve radius estimating device according to any one of claims 1 to 3. 5. An image pickup means mounted on a vehicle for taking an image of a road ahead of the vehicle, and a radius estimating means for estimating a curve radius of the road ahead based on image information from the image pickup means. A curve radius estimating device provided, a target steering angle calculating means for calculating a target steering angle based on the curve radius of the forward traveling road estimated by the curve radius estimating device, and a target steering angle calculating means In an automatic steering control system with a curve radius estimating device, comprising: an automatic steering control means for controlling a steering actuator of the vehicle based on a target steering angle; Bank angle estimating means for estimating a bank angle of a road surface on which the vehicle is traveling, and the traveling estimated by the radius estimating means on the basis of the bank angle estimated by the bank angle estimating means. Automatic steering control system with a characterized in that it includes a curve radius correcting means for correcting the curve radius, the curve radius estimation device. 6. The target steering angle calculation means is based on the bank angle estimated by the bank angle estimation means, and is based on the curve radius based on the bank angle and a corrected steering angle corresponding to a lateral force generated in a vehicle by gravity. The automatic steering control system with a curve radius estimating device according to claim 5, further comprising target steering angle correcting means for correcting the target steering angle.