WO2012045323A1

WO2012045323A1 - Method and driver assistance system for warning a driver of a motor vehicle of the presence of an obstacle in an environment of the motor vehicle

Info

Publication number: WO2012045323A1
Application number: PCT/EP2010/006120
Authority: WO
Inventors: Myles Friel; Patrick Eoghan Denny
Original assignee: Connaught Electronics Ltd
Current assignee: Connaught Electronics Ltd
Priority date: 2010-10-07
Filing date: 2010-10-07
Publication date: 2012-04-12
Anticipated expiration: 2013-04-07

Abstract

A solution is to be demonstrated, how a driver of a motor vehicle (1) can be particularly reliably warned of obstacles (15) located in the environment of the vehicle (1), namely with the aid of a collision warning system (2). A method is provided, in which image data of the environment of the vehicle (1) is captured by a camera (5a to 5d). A relative position of the obstacle (15) with respect to the motor vehicle (1) is determined based on the image data. A steering angle (α) of the motor vehicle (1) is detected. The driver is warned if a predetermined warning criterion related to the relative position of the obstacle (15) and to the steering angle (α) is satisfied. A corresponding driver assistance system (2) is also provided, which is formed for performing the method.

Description

METHOD AND DRIVER ASSISTANCE SYSTEM FOR WARNING A DRIVER

OF A MOTOR VEHICLE OF THE PRESENCE OF AN OBSTACLE IN AN ENVIRONMENT OF THE MOTOR VEHICLE

The invention relates to a method for warning a driver of a motor vehicle of the presence of an obstacle in an environment of the motor vehicle. The driver is warned with the aid of a driver assistance system of the motor vehicle. In addition, the invention relates to a driver assistance system serving for performing such a method.

Presently, the interest is in a so-called collision warning system, by which the driver of a motor vehicle is warned if a collision between the motor vehicle and an object external to the vehicle - an obstacle - is imminent. Such driver assistance systems are already known from the prior art. The printed matter EP 1 660 362 B1 describes a system formed for calculating a - prospective - traveled way traveled by the motor vehicle in the future. It is differentiated between relevant obstacles inside the traveled way and non relevant obstacles outside of the prospective trajectory. The driver is only warned of relevant obstacles.

Also, from the printed matter EP 1 571 638 B1 , a system for warning the driver of objects is known, which are on a calculated prospective traveled way of the motor vehicle. It is determined whether or not the motor vehicle will pass by the obstacle without collision. The driver can pass by an obstacle in a very small distance without an annoying warning being output. The warning is only output if the obstacle is on the predicted traveled way and thus a collision is actually in danger of occurring.

Additionally, a collision warning system is known from the document DE 198 43 564 A1. A risk of collision of the motor vehicle with an object external to the vehicle is assessed based on an estimated distance as well as based on the current velocity of the motor vehicle. The warning signal is output if the estimated instantaneous distance is smaller than a preset limit value and the assessment reveals the presence of a risk of collision. For the assessment of the risk of collision, a time to collision is determined, that the motor vehicle requires for reaching the object. Based on this determined time, then, the risk of collision of the vehicle with the object is assessed. The printed matter EP 1 447 271 A2 describes a method for monitoring the vicinity of a motor vehicle. Collisions of the motor vehicle with obstacles are to be avoided. A range sensor measures a range between the motor vehicle and an obstacle and is attached to a lateral flank of the motor vehicle. Thus, by the range sensor, obstacles besides the motor vehicle can be detected. A steering angle sensor measures a steering angle of the motor vehicle. With the aid of a path sensor, a distance covered by the motor vehicle is detected. The respectively current position of an obstacle once detected by the range sensor can be assessed depending on the traveled distance of the motor vehicle. Thus, the respectively current position of the obstacle relative to the motor vehicle can even be calculated if the obstacle is no longer in the detection range of the range sensor. The range sensor is an ultrasonic sensor.

From the document US 2009/0322502 A1 , a device for detecting objects in the environment of a motor vehicle is known. An image of the environment is captured by a camera and is analyzed. Based on the image, objects located in the environment can be detected. For detecting an object, various regions of the captured image are

consecutively analyzed, namely in such an order, which is set according to predetermined criteria. First, a region of the image is analyzed, which faces the motor vehicle. This means that in the analysis of the image, it is begun with the side of the image facing the motor vehicle, and it is terminated on a side of the image facing away from the motor vehicle. The order of the analysis of various regions of the image can also be determined considering the side of the road, on which one is traveling, namely depending on whether the left-hand traffic or the right-hand traffic is provided. The order can also be set considering GPS data

A collision warning system is also known from the document WO 2010/006390 A1.

In the prior art, usually, distance sensors - like ultrasonic sensors - are used for collision warning systems. Such collision warning systems have the disadvantage that the respectively instantaneous relative position of an obstacle with respect to the motor vehicle cannot be determined with highest accuracy. With the aid of an ultrasonic sensor, the position of the obstacle can only be coarsely assessed or only a distance between the obstacle and the motor vehicle is measured. In such collision warning systems, situations can occur, in which the driver is warned due to a relatively small direct distance between the motor vehicle and the obstacle, although a collision is not in danger of occurring at the given steering angle. By this warning, the driver is then unnecessarily disturbed. An object of the invention is to demonstrate a solution, how the driver of a motor vehicle can particularly reliably be warned of obstacles in the environment by a driver assistance system of the motor vehicle.

According to the invention, this object is solved by a method having the features according to claim 1 as well as by a driver assistance system having the features according to claim 15. Advantageous embodiments of the invention are subject-matter of the dependent claims and of the description.

A method according to the invention serves for warning a driver of a motor vehicle of the presence of an obstacle in an environment of the motor vehicle. The driver is warned with the aid of a driver assistance system - like a collision warning system. Image data of the environment is captured by a camera of the driver assistance system. The driver assistance system then determines a relative position of the obstacle with respect to the motor vehicle based on the image data. The driver assistance system detects a steering angle of the motor vehicle, namely in particular a steering wheel angle. The driver is warned by the driver assistance system if a predetermined warning criterion related to the relative position of the obstacle and to the steering angle is satisfied.

Thus, the effect according to the invention is achieved in that the relative position of the obstacle with respect to the motor vehicle is determined based on image data of a camera on the one hand, and based on the current steering angle and the instantaneous position of the obstacle relative to the motor vehicle, it is determined whether or not a collision between the motor vehicle and the obstacle is in danger of occurring, on the other hand. The invention has various advantages: based on image data of the camera, the instantaneous position of the obstacle with respect to the motor vehicle can be determined with highest accuracy, and the obstacle can be tracked based on the image data by the driver assistance system. Thus, the driver can be reliably warned of obstacles in the environment. The invention also has the advantage that a camera of an optical vision system already present in the vehicle can also be used for the function of collision warning. Thus, an optical vision system can be combined with a collision warning system. Namely, modern vehicles often dispose of such optical vision systems, which comprise a plurality of cameras, which capture the entire environment around the motor vehicle. The image data of these cameras can now be taken for determining the respectively instantaneous relative position of an obstacle with respect to the motor vehicle. With the aid of image data, the relative position of the obstacle with respect to the motor vehicle can also be determined with high resolution, which is not possible by means of an ultrasonic sensor in the prior art. If the exact relative position of the obstacle with respect to the motor vehicle is known, thus, it can now be determined based on the current steering angle, whether or not a collision between the obstacle and the motor vehicle is imminent. This is particularly advantageous since the driver is only warned by the driver assistance system if a collision is actually in danger of occurring.

Principally, the relative position of the obstacle can be determined solely based on image data of at least one camera. Then, other sensors will not have to be employed, and the driver assistance system for example copes without distance sensors, as they are employed in the prior art. However, alternatively, it can also be provided that data of a sensor different from the camera is also used for determining the relative position of the obstacle, like a distance sensor, such as an ultrasonic sensor.

The driver is warned upon the warning criterion being fulfilled. This warning criterion can for example include the condition that the steering angle is in a predetermined range of values. This range of values can also depend on the relative position of the obstacle with respect to the motor vehicle. If the obstacle is for example on the side besides a lateral flank of the motor vehicle, thus, the warning criterion can include the condition that the steering angle exceeds a predetermined limit value, thus is in a range of values between the limit value and infinite. Then, this limit value can depend on the position of the obstacle relative to the motor vehicle, namely can depend on a direct distance between the obstacle and the lateral flank of the motor vehicle on the one hand and depend on the position of the obstacle in the vehicle longitudinal direction on the other hand. In contrast, if the obstacle is in front of the motor vehicle in the direction of travel, thus, the warning criterion can include the condition that the steering angle is below a predetermined limit value, thus in a range of values between zero and the limit value. If a correspondingly great steering angle is set by the driver here, the vehicle can drive around the obstacle, and the driver does no longer have to be warned. This embodiment also has the advantage that the driver is not unnecessarily warned by the driver assistance system and a warning signal is only output if it is really required.

The determination of the relative position of the obstacle with respect to the motor vehicle can include that a range of the obstacle from the motor vehicle is determined based on the image data. Then, the warning criterion can also include a condition related to this range. For example, the warning criterion can include the condition that the range between the obstacle and the motor vehicle falls below a predetermined limit value. The determination of the relative position of the obstacle can also include that an absolute position of the obstacle within a coordinate system of the motor vehicle is determined. Then, both the position of the obstacle in the vehicle longitudinal direction and the position of the obstacle in vehicle transverse direction are known, and the driver assistance system can determine whether or not a collision is imminent, based on the current steering angle.

In an embodiment, the obstacle in the environment of the motor vehicle is consecutively tracked by the driver assistance system based on the image data, and the warning criterion is consecutively verified. This means that the relative position of the obstacle with respect to the motor vehicle is consecutively or continuously determined based on the image data. Preferably, the obstacle is tracked during a period of time, during which it is in a detection range of the camera. In this embodiment, the driver assistance system can track the obstacle until the obstacle exits the detection range of the camera. In this manner, the environment of the motor vehicle is consecutively monitored, and the driver can be warned of a possible collision in time. The consecutive determination of the respectively instantaneous position of the obstacle and the consecutive verification of the warning criterion also provide for high safety.

It proves particularly advantageous if a prospective trajectory of the motor vehicle is determined depending on the steering angle. Then, the warning criterion can include the condition that the obstacle is on the prospective trajectory. Thus, the driver is warned if a collision between the motor vehicle and the obstacle is in danger of occurring. The prospective trajectory can be estimated depending on the current steering angle starting from the respectively instantaneous position of the motor vehicle for a predetermined length of distance. If the steering angle changes, thus, the trajectory can each be newly determined for the predetermined length of distance. Thus, the driver assistance system can verify whether or not the obstacle is on the prospective trajectory. If the obstacle is on the prospective trajectory, the driver can be warned.

In a preferred embodiment, it is provided that a height of the obstacle is determined based on the image data, and the warning criterion includes a condition related to the height of the obstacle. In other words, in verifying the warning criterion, the height of the obstacle can also be considered. The determination of the height of the obstacle is enabled by employment of the camera; the height cannot be determined with a simple distance sensor in the prior art. This embodiment is based on the fact that some obstacles - such as low curbs - can be driven over, whereas the driver should be warned in case of higher obstacles. Therefore, this embodiment has the advantage that the driver is not unnecessarily warned of low obstacles and thus can concentrate on the street situation in undisturbed manner.

The warning criterion can for example include the condition that the height of the obstacle exceeds a preset limit value. Thus, the driver is only warned if the height of the obstacle exceeds the limit value and therefore collision between the motor vehicle and the obstacle actually can occur. In case of lower obstacles such as curbs, the driver does not necessarily have to be warned. The limit value for the height can for example be in a range of values from 10 cm to 20 cm.

Preferably, image data at least of a region of the environment besides a lateral flank of the motor vehicle is captured by the camera such that an obstacle located besides the lateral flank is detected based on the image data. In this manner, it is succeeded in preventing a collision of the motor vehicle with the obstacle on the lateral flank. Namely, usually, it is the lateral flank of the motor vehicle, which cannot be monitored completely or only with high effort by the driver himself. Thus, obstacles are also detected, which are located in the region of the blind angle and therefore cannot be seen by the driver himself. The camera can for example be mounted on the lateral flank or even on an exterior mirror. However, additionally or alternatively, a camera can also be mounted on a front and/or a rear bumper in order to capture the region in front of and behind the motor vehicle, respectively. In total, several cameras can be employed, namely a camera on a left lateral flank and/or a camera on a left exterior mirror and/or a camera on a right lateral flank and/or a camera on a right exterior mirror and/or a camera on a front bumper and/or a camera on a rear bumper of the motor vehicle. In total, a 360° image of the environment around the motor vehicle can be captured by the cameras. The at least one camera can for example be a CMOS (Complementary Metal Oxide Semiconductor) camera or a CCD (Charge-Coupled Device) camera.

In an embodiment, various image regions of an image captured by the camera are analyzed consecutively in time in an order, which is set depending on the current steering angle, for detection of the obstacle. In contrast to the subject-matter according to the document US 2009/0322502 A1 , the determination of the order is effected considering the current steering angle of the motor vehicle in this embodiment. For example, if a 360° image of the environment around the motor vehicle is captured, thus, this image can first be analyzed on that side of the motor vehicle, in the direction of which the wheels of the motor vehicle are turned in. In this manner, obstacles can be detected based on the image data within shortest time, which are on the relevant side besides the motor vehicle. Obstacles constituting a potential risk can therefore quickly be detected. Also, the direction of motion of the vehicle can be considered while setting said order.

The warning of the driver is preferably effected with the aid of an optical display means such as a display of the motor vehicle, and/or with the aid of an acoustic output means, namely for example a loudspeaker or the like.

As already explained, for detection of the obstacle, image data of an optical vision system already present in the motor vehicle can be used. In an embodiment, an image of the motor vehicle and the obstacle located in the environment can be displayed on a display means of the motor vehicle - such as on a display. Principally, an image of the motor vehicle as well as of the entire environment around the motor vehicle can be displayed on the display means. This image can for example show the motor vehicle and the environment from a bird's eye view - a plan view of the motor vehicle and the environment can be displayed. The image of the motor vehicle can for example already be factory- stored in a memory of the driver assistance system, whereas the image of the

environment is preferably consecutively captured by the at least one camera and consecutively updated.

The warning of the driver can for example be such that after satisfaction of the warning criterion, the displayed image on the display means is varied in at least one feature. For example, the displayed image can be varied in coloring after satisfaction of the warning criterion. For example, the color of the displayed obstacle and/or the color of the motor vehicle can be varied. In this manner, the driver can particularly easily recognize on the display means whether or not a collision of the motor vehicle with the obstacle is in danger of occurring.

The obstacle can also be displayed on the display means with an enlarged scale with respect to the motor vehicle. In this manner, it is simulated to the driver that the distance from the obstacle to the motor vehicle is smaller than the actual distance. Thus, the risk of a collision is reduced to a minimum. Namely, the driver will drive his vehicle such that the motor vehicle presented in the image will not collide with the "falsified" presented obstacle, and therefore always remains in a certain distance to the obstacle.

Preferably, the motor vehicle is displayed fixedly or stationarily on the display means, even if the motor vehicle moves. In movement of the motor vehicle, preferably, only the image of the environment is updated and adapted on the display means. In the image displayed on the display means, a prospective trajectory of the motor vehicle can also be displayed, which is determined depending on the current steering angle. Additionally or alternatively, a path can also be displayed on the display means, which starts from the displayed obstacle and extends towards the motor vehicle against the direction of travel and against the trajectory of the motor vehicle. In this manner, it is succeeded in informing the driver about the prospective traveled way of the motor vehicle at the given steering angle, and the driver can optionally change the steering angle in order to drive around the obstacle without collision.

Preferably, a desired value for the steering angle, at which passing the obstacle without collision is allowed, is calculated by the driver assistance system depending on the current relative position of the obstacle with respect to the motor vehicle. Then, information on the desired value for the steering angle can be output. Thus, the driver is informed about the desired value of the steering angle and can adjust the actual steering angle in accordance with the desired value.

The driver can be informed about the desired value of the steering angle e.g. in the manner that a desired trajectory of the motor vehicle is also displayed in the image displayed on the display means, which results for the desired value of the steering angle. Then, the driver can directly see the desired trajectory on the display means and correspondingly adapt the actual - optionally also displayed - trajectory to the desired trajectory.

The functionality of warning the driver of the presence of an obstacle in the environment of the vehicle can also be combined with other vehicle functionalities or driver assistant systems, like an autonomous parking system, for example. In this embodiment, obstacles can be detected in the vehicle environment and the driver can be warned while the vehicle is being parked in a parking space autonomously. Also, the image data can be used for calculating a parking trajectory along which the vehicle can be parked in the parking space. So, the camera can also be used for other vehicle systems; for example, the camera can be used to navigate the vehicle safely, in particular to navigate the vehicle while parking in the parking space.

According to the invention, moreover, a driver assistance system for a motor vehicle is provided, namely in particular a collision warning system. The driver assistance system is formed for warning a driver of the motor vehicle of the presence of an obstacle in an environment of the motor vehicle. The driver assistance system includes a camera for capturing image data of the environment. It also comprises a control means determining a relative position of the obstacle with respect to the motor vehicle based on the image data. The control means also receives information on a steering angle of the motor vehicle. The control means causes a warning if a predetermined warning criterion related to the relative position of the obstacle and to the steering angle is satisfied.

According to the invention, a motor vehicle is also provided, which includes the driver assistance system according to the invention.

The preferred embodiments presented with reference to the method according to the invention and the advantages thereof correspondingly apply to the driver assistance system according to the invention as well as to the motor vehicle according to the invention.

Further features of the invention are apparent from the claims, the figures and the description of figures. All of the features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the description of figures and/or shown in the figures alone are usable not only in the respectively specified combination, but also in other combinations or even alone.

Now, the invention is explained in more detail based on individual preferred embodiments, as well as with reference to the attached drawings.

There show:

Fig. 1 in schematic illustration a plan view of a motor vehicle with a driver

assistance system according to an embodiment of the invention;

Fig. 2 in schematic illustration a plan view of a traffic situation, wherein a method according to an embodiment of the invention is explained in more detail; and

Fig. 3 in schematic illustration a display means of the driver assistance system with an image displayed thereon. A vehicle 1 , as it is represented in Fig. 1 , is a passenger car. The vehicle 1 includes a driver assistance system 2, which is a collision warning system. The driver assistance system 2 includes the following components: a display means 3, a control means 4 as well as four cameras 5a to 5d. The control means 4 drives the display means 3. The cameras 5a to 5d transmit captured image data to the control means 4, namely for example through an internal communication bus of the vehicle 1.

For example, the display means 3 can be an LCD display. However, it can also be a projector, with the aid of which images can be projected to a windshield 6 of the motor vehicle 1 - a so-called head-up display.

In addition, a vehicle image is stored in the control means 4 - and more precisely data representing an image of the vehicle 1. The vehicle image is stored in a memory 7.

The cameras 5a to 5d are disposed on an exterior surface of the vehicle 1. The number as well as the arrangement of the cameras 5a to 5d are only exemplarily illustrated in Fig. 1 ; according to the embodiment, the number of the cameras 5a to 5d as well as the arrangement thereof on the vehicle 1 can vary. In the embodiment, a first camera 5a is disposed on a front bumper of the vehicle 1 , while a second camera 5b is disposed on a rear bumper. A third camera 5c is attached to the left lateral flank; it can also be incorporated in a left exterior mirror 8. A fourth camera 5d is attached to the right lateral flank, namely in the region of a right exterior mirror 9. The fourth camera 5d can also be incorporated in the exterior mirror 9.

Basically, any type of cameras 5a to 5d can be used to capture the surroundings of the vehicle 1. For example, the cameras 5a to 5d each can have a wide capturing angle. They can thus be so-called fish-eye cameras. For example, the respective capturing angle can be in a range of values from 140° to 210°. However, the respective capturing angle can also be smaller: it can be in a range of values from 40° to 140°. Altogether, the respective capturing angle can be a value from a range of values from 40° to 210°. For instance, it can amount to 65° or 90° or 10° or 130° or 150° or 170° or 190° or 200°. Also, cameras 5a to 5d with different capturing angles can be used each to capture a part of the vehicle surroundings. As it is apparent from Fig. 1 , the first camera 5a captures a region 10 in front of the vehicle 1 , while the second camera 5b captures a region 11 behind the vehicle 1. Correspondingly, the third camera 5c captures a region 12 on the left besides the vehicle 1 ; the fourth camera 5d captures a region 13 on the right besides the vehicle 1. The cameras 5a to 5d can also capture substantially the entire environment around the motor vehicle 1 , namely a 360° image.

The control means 4 can process the image data captured by the cameras 5a to 5d. The control means can generate images based on the image data, which represent an illustration of a plan view of the environment of the vehicle 1 , namely of the capturing regions 10 to 13. The control means 4 thus can generate an environmental image from the image data, which shows a plan view of the capturing regions 10 to 13.

As already explained, a vehicle image of the vehicle 1 is stored in the memory 7. This vehicle image also shows the vehicle 1 from a bird's eye view; in other words, the vehicle image shows a plan view of the vehicle 1. The control means 4 can generate an image from the environmental image and the vehicle image such that both the environment of the vehicle 1 and the vehicle 1 itself are presented in a single image from a bird's eye view. The control means 4 can display this image on the display means 3. The image thus generated is continuously displayed on the display means 3. This means that the image continuously adapts itself to the environment of the vehicle 1. Namely, the image data is continuously captured by the cameras 5a to 5d. In the displayed image, the motor vehicle 1 is shown fixedly or stationarily, while the image of the environment is always updated and adapted. However, on the display means 3 also an image can be displayed that is not a plan view of the vehicle 1 and the vehicle environment. The image captured by the cameras 5a to 5d can be processed in different ways or even displayed without having been processed. For example, an image captured by any one of the cameras 5a to 5d (the rearview camera 5b, for instance) or any combination of images of different cameras 5a to 5d can be directly displayed on the display means 3. Also, an image can be displayed that shows only the vehicle environment without the vehicle itself. For example, the rear view image of the camera 5b can be displayed so that the driver is provided with an image of the area behind the vehicle 1. This can be very useful when driving backwards.

The control means 4 also serves for warning the driver of an imminent collision of the vehicle 1 with an object external to the vehicle, namely an obstacle. In the embodiment, the driver is warned of obstacles with the aid of the display means 3 as well as optionally with the aid of a loudspeaker. For this purpose, the control means 4 receives information on a steering angle a, which is a turning angle of a steering wheel 14. The steering angle a can for example be measured with the aid of a sensor and data concerning the steering angle a can be transmitted from this sensor to the control means 4 through a

communication bus.

With reference to Fig. 2, a method according to an embodiment of the invention is explained in more detail. The driver maneuvers the vehicle 1 ; the vehicle 1 is for example parked in a parking space not illustrated in Fig. 2. The control means 4 analyzes the image data of the environment of the vehicle 1 in order to detect obstacles optionally located in the environment. First, the control means 4 can analyze that side of the vehicle 1 in the extracted image of the environment, which is relevant with respect to the vehicle motion. Here, the control means 4 considers both the steering angle a as well as the current direction of motion of the vehicle 1. For example, if the vehicle 1 is driven forward, the control means 4 first analyzes that side of the vehicle 1 in the extracted image of the environment, to which the steerable wheels are turned in. If the vehicle 1 is driven backwards, the control means 4 can first analyze image data regarding the opposite side of the vehicle 1 and/or regarding the area behind the vehicle 1.

The control means 4 detects an obstacle 15, which is on the right besides the vehicle 1 , namely besides the right lateral flank. The obstacle 15 is recognized by the control means 4 based on image data having been captured by the fourth camera 5d. Based on this image data, the control means 4 determines the respectively instantaneous relative position of the obstacle 15 with respect to the motor vehicle 1 and determines based on this relative position as well as based on the steering angle a whether or not a critical situation is imminent.

The control means 4 first determines a direct distance 16 between the right lateral flank of the vehicle 1 and a critical point 17 of the obstacle 15 based on the image data. The control means 4 also determines the position of the obstacle 15 in the vehicle longitudinal direction 18. For example, the control means 4 can determine the position of the obstacle 15 in a coordinate system of the vehicle 1.

The control means 4 can also determine a height 19 of the obstacle 15 based on the image data.

Depending on the current steering angle a, the control means 4 also determines a prospective trajectory 20 of the vehicle 1 , namely a traveled way, which is prospectively traveled by the vehicle 1. The trajectory 20 is a strip immediately limited by two limiting lines 21 , 22. For determining the limiting lines 21 , 22, the outermost point of the vehicle 1 viewed in direction of travel on the left or right side is each considered. The limiting lines 21 , 22 also correspond to the respective paths that the outermost points of the vehicle 1 leave during travel. Thus, the width of the trajectory 20 is determined by the distance of the limiting line 21 , 22. Usually, the outermost points of the vehicle 1 are the curve- outward front edge of the vehicle 1 as well as the wheel well of the curve-inward rear wheel. The width of the trajectory 20 is also usually - namely in cornering - greater than the actual width of the vehicle 1. Only in straight-ahead traveling, the width of the trajectory 20 corresponds to the width of the vehicle 1.

The control means 4 warns the driver of the vehicle 1 if a predetermined warning criterion is satisfied, namely if a collision between the obstacle 15 and the vehicle 1 is in danger of occurring. This warning criterion can include various conditions, namely for example at least one of the following conditions:

- the condition that the obstacle 15 is at least in certain regions on the trajectory 20 and/or

- the condition that the steering angle a is in a predetermined range of values; this range of values varies depending on the current position of the obstacle 15 relative to the vehicle 1 ; and/or

- the condition that the height 19 of the obstacle 15 exceeds a predetermined limit value, namely for example 15 cm, and/or

- the condition that the direct distance 16 falls below a predetermined limit value, namely for example 20 cm.

If the warning criterion is satisfied, thus, the control means 4 warns the driver of the obstacle 15. This warning is effected e.g. with the aid of the display means 3. Fig. 3 shows an exemplary image 23 as it can be displayed on the display means 3. This image 23 shows a plan view of the vehicle 1 as well as the environment of the vehicle 1 including the obstacle 15. Here, the obstacle 15 can be presented with an enlarged scale with respect to the vehicle 1 , thereby providing an additional safety buffer to the driver. The displayed image 23 also shows the current prospective trajectory 20 with the limiting lines 21 , 22, which is determined by the control means 4 based on the steering angle a. The control means 4 also calculates a desired trajectory 24, which is immediately limited by two limiting lines 25, 26. This desired trajectory 24 results for a desired value of the steering angle a, which allows passing the obstacle 15 without collision. The desired value is calculated by the control means 4. Thus, both the prospective trajectory 20 and the desired trajectory 24 are displayed on the display means 3. The desired trajectory 24 can be presented with another coloring than the prospective trajectory 20. However, the image displayed on the display means 3 is not limited to a plan view image. For instance, a rear view image captured by the camera 5b (or any other camera) can be displayed on the display means 3. Then, the driver can also be warned of obstacles with the aid of the display means 3 and/or different pieces of information can be displayed together with the rear view image. In this case, the driver can be exiting a garage door or gate for example, and the control unit 4 can detect the sides of the door and - based on the steering angle a as well as the direction of motion - inform the driver that the current steering angle a will or will not be effective in avoiding the side of the garage door. The driver can then avoid the garage door even if an assist system based on ultrasonic sensors is continuously beeping due to the small distance between the vehicle 1 and the garage door.

Displaying the rear view image captured by the camera 5b can also be advantageous in situations in which a trailer is attached to the vehicle 1 and the driver is driving at an unsuitable steering angle a. In such situations, when a collision between the rear bumper of the vehicle 1 and the front side of the trailer can occur, the driver can also be warned by the control unit 4. In this case, the trailer is considered to be an obstacle external to the vehicle 1.

If the warning criterion is satisfied, thus, the control means 4 warns the driver. For example this can be in that the coloring of the image 23 is varied after satisfaction of the warning criterion; for example, the coloring of the obstacle 15 and/or of the vehicle 1 and/or of the prospective trajectory 20 can be varied. It is also possible to signal the satisfaction of the warning criterion to the driver in another manner, namely for example by flashing of the obstacle 15. Additionally or alternatively, an acoustic warning signal can also be output.

Claims

1. Method for warning a driver of a motor vehicle (1 ) of the presence of an obstacle

(15) in an environment (10, 11 , 12, 13) of the motor vehicle (1 ) with the aid of a driver assistance system (2) of the motor vehicle (1), comprising the steps of:

- capturing image data of the environment (10, 11 , 12, 13) by at least one camera (5a to 5d) of the driver assistance system (2) and determining a relative position of the obstacle (15) with respect to the motor vehicle (1) based on the image data,

- detecting a steering angle (a) of the motor vehicle (1 ) by the driver assistance system (2), and

- warning the driver by the driver assistance system (2) after satisfaction of a predetermined warning criterion related to the relative position of the obstacle (15) and to the steering angle (a).

2. Method according to claim 1 ,

characterized in that

the warning criterion includes the condition that the steering angle (a) is in a predetermined range of values, which depends on the relative position of the obstacle (15).

3. Method according to claim 1 or 2,

characterized in that

the determination of the relative position of the obstacle (15) includes that a range

(16) of the obstacle (15) from the motor vehicle (1) is determined based on the image data, wherein the warning criterion includes a condition related to this range (16).

4. Method according to anyone of the preceding claims,

characterized in that

the obstacle (15) in the environment (10, 11 , 12, 13) of the motor vehicle (1 ) is consecutively tracked by the driver assistance system (2) based on the image data and the warning criterion is consecutively verified.

5. Method according to anyone of the preceding claims,

characterized in that

a prospective trajectory (20) of the motor vehicle (1) is determined depending on the steering angle (a), and the warning criterion includes the condition that the obstacle (15) is on the prospective trajectory (20).

6. Method according to anyone of the preceding claims,

characterized in that

a height (19) of the obstacle (15) is determined based on the image data, and the warning criterion includes a condition related to the height (19) of the obstacle (15).

7. Method according to claim 6,

characterized in that

the warning criterion includes the condition that the height (19) of the obstacle (15) exceeds a preset limit value.

8. Method according to anyone of the preceding claims,

characterized in that

by the camera (5a to 5d), image data is captured at least of a region of the environment (10, 11 , 12, 13) besides a lateral flank of the motor vehicle (1), and an obstacle (15) located besides the lateral flank is detected based on the image data.

9. Method according to anyone of the preceding claims,

characterized in that

for detection of the obstacle (15), various image regions of an image captured by the camera (5a to 5d) are analyzed consecutively in time in an order, which is set depending on the current steering angle (a).

10. Method according to anyone of the preceding claims,

characterized in that

the warning of the driver is effected by the aid of an optical display means (3) and/or an acoustic output means.

11. Method according to anyone of the preceding claims,

characterized in that on a display means (3) of the motor vehicle (1), an image (23) of the motor vehicle (1) and of the obstacle (15) located in the environment (10, 11 , 12, 13) is displayed, and the warning of the driver includes that the displayed image (23) is varied in at least one feature, in particular is varied in a coloring, after satisfaction of the warning criterion.

12. Method according to claim 11 ,

characterized in that

a prospective trajectory (20) of the motor vehicle (1 ) is also displayed in the displayed image (23), which is determined depending on the current steering angle (a).

13. Method according to anyone of the preceding claims,

characterized in that

a desired value for the steering angle (a), at which passing the obstacle (15) without collision is allowed, is calculated by the driver assistance system (2) depending on the current relative position of the obstacle (15) with respect to the motor vehicle (1), and information on the desired value for the steering angle (a) is output.

14. Method according to claim 11 or 12 and 13,

characterized in that

a desired trajectory (24) of the motor vehicle (1) is also displayed in the displayed image (23), which results for the desired value of the steering angle (a).

15. Driver assistance system (2) for a motor vehicle (1 ), for warning a driver of the

motor vehicle (1 ) of the presence of an obstacle (15) in an environment (10, 11 , 12, 13) of the motor vehicle (1), including:

- a camera (5a to 5d) for capturing image data of the environment (10, 11 , 12, 13), and

- a control means (4), which is configured to determine a relative position of the obstacle (15) with respect to the motor vehicle (1) based on the image data, to receive information on a steering angle (a) of the motor vehicle (1 ), and to warn the driver after satisfaction of a predetermined warning criterion related to the relative position of the obstacle (15) and to the steering angle (a).