GB2445866A

GB2445866A - Method for estimating a distance of a vehicle to an object, and driver assistance system

Info

Publication number: GB2445866A
Application number: GB0800851A
Authority: GB
Inventors: Mario Mueller; Andreas Simon
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2007-01-18
Filing date: 2008-01-17
Publication date: 2008-07-23
Anticipated expiration: 2028-01-17
Also published as: FR2911678A1; GB2445866B; DE102007002813A1; GB0800851D0

Abstract

A method and a driver assistance system for estimating a distance 41 of a vehicle 11 to an object 12, such as a preceding vehicle, in which the distance is estimated by means of elevations of a progression of a surface or road 17 on which the vehicle is moving. The system includes a camera 13 arranged to capture images of the road in front of the vehicle and an image processor 16 which locates an object in the vicinity of the vehicle. A control device 15 estimates the distance between the vehicle and the object, taking into account the gradient of the road between the vehicle and the object. The gradient may be determined from a digital map stored on a digital storage medium such as a CD-ROM device 24.

Description

Method for estimating a distance of a vehicle to an object and driver

assistance system The present invention relates to a method for estimating a distance of a vehicle to an object in the vehicle's envirornflent. Furthermore, the invention relates to a driver assistance system for a vehicle for estimating a distance of the vehicle to an object in the vehicle's environment.

Driver assistance systems serve to support a driver when driving a vehicle, to warn him of impending hazards and/or to initiate measures automatically to alleviate the consequences of any imminent collision. To do this, the driver assistance systems access data of a positioning system with which objects in the vehicle's environment, especially other traffic participants, can be detected.

Examples of such driver assistance systems are systems for lane departure warning, for instance, which alert the driver if he is about to leave the lane he is currently driving in without indicating, or systems that adjust the speed of one's own vehicle automatically so that a car detected travelling in front can be followed at a safe distance. Mono or stereo video systems, for example, can be used as positioning systems. In the mono video system, a single video camera is used, and in the stereo video system, two video cameras are used to cover the vehicle's environment. However, while in the stereo video system the distance from the vehicle to the object in the vehicle's environment can be determined directly, in particular by triangulation, the mono video system relies on a model assumption. In this model assumption it is normally established that a lower edge of the object detected by means of the mono video system, seen in a vertical direction, is in the same plane as the vehicle containing the mono video system. This assumption can lead to errors in estimating the distance between the vehicle and the object, as the object is not necessarily located together with the vehicle in this same vertical plane.

The object of the present invention is to facilitate an accurate estimate of a distance between a vehicle and an object located in the vehicle's environment.

This object is achieved on the method side by the technical doctrine of claim 1 and on the device side by the technical doctrine of claim 6. Advantageous configurations of the invention can be inferred from the dependent claims.

According to the invention, the distance between the vehicle and the object in the vehicle's environment is estimated by means of elevations of a progression of a surface on which the vehicle is moving. The driver assistance system according to the invention is formed correspondingly to estimate the distance by means of elevations of the progression of the surface on which the vehicle is moving. Due to the elevations, a curvature of the surface in a vertical direction can advantageously be taken into account when estimating the distance. The vertical curvature can have the effect that the object is positioned higher or lower in comparison with the vehicle, viewed in a vertical direction. This vertical deviation of the position of the object from the position of the vehicle is thus taken into account to estimate the distance. The actual distance can thereby be estimated substantially more accurately. This advantageously increases the safety of the occupants of the vehicle and can in some cases considerably reduce the risk of an accident, in particular by suitable initiation of counter-measures if the distance is too short. The elevations can advantageously be derived from an elevation profile of the surface. The surface is in particular a travel path of the vehicle, e.g. a road.

The progression of the surface corresponds advantageously to the progression that the surface has starting out from the vehicle in the direction of the object. The object can in particular be another vehicle travelling in front of the vehicle.

In one advantageous configuration of the invention, the elevations of the surface are taken from a digital map.

This is easily possible. On the digital map, the elevations are present electronically in the form of digital information. The digital map includes information, for example, such as is present on maps and/or Street maps.

In particular, the digital map includes information about surfaces of the landscapes and/or localities covered by the digital map. These surfaces are above all travel paths for vehicles, such as e.g. roads. Here the digital map contains height data on the progressions of the surfaces, in particular the travel paths. The digital map advantageously has elevation profiles of the surfaces.

Such a digital map can be used for example in a navigation system for vehicles. In this respect the use of the digital map is especially advantageous, as it can be used for two applications in the vehicle. The digital map can be realized for example as a data file or database.

Following retrieval of the information contained in the digital map, this information can be shown e.g. on a screen in the navigation system.

In a further, especially advantageous configuration, the digital map is stored on a digital storage medium. In this case, the elevations are read from the digital storage medium. For this purpose the driver assistance system according to the invention has a suitable reading device for reading the digital storage medium. The digital map can advantageously be retrieved especially easily on the digital storage medium and can be used very simply and practically. The digital storage medium can in particular be a so-called CD-ROM or a so-called DVD.

The distance is preferably estimated by means of the elevations of that progression of the surface which the surface has between roughly a position of the vehicle on the surface and a horizon. The distance can be estimated particularly accurately due to this. The horizon corresponds in this case in particular to an infinitely great distance from the vehicle.

It is particularly preferred for picture information about the environment of the vehicle to be acquired by a camera, in particular a single camera. This picture information acquired is then processed by a picture processing device.

Concerning the driver assistance system according to the invention, the camera and the picture processing device are parts of the driver assistance system. The use of the camera advantageously facilitates an accurate recording of the environment. The picture processing device can in particular process the picture information acquired to locate objects in the environment of the vehicle. To this end the picture processing device contains suitable algorithms. The use of just a single camera is advantageously especially cost-effective.

The invention and its advantages are explained in greater detail below with reference to embodiments and the enclosed drawing.

Fig. 1 shows a schematic representation of an embodiment of a driver assistance system according to the invention in a vehicle and Fig. 2 shows a schematic representation of a picture recording of a camera of the driver assistance system according to the invention according to figure 1.

In the figures, elements which are the same or have the same function are provided below with the same reference signs unless indicated otherwise.

Figure 1 shows a schematic representation of a side view of an embodiment of a driver assistance system 10 according to the invention in a motor vehicle 11. The driver assistance system 10 serves to estimate a distance of the motor vehicle 11 to an object 12, which is located in an environment of the motor vehicle 11. The object 12 can be another motor vehicle travelling in front of the motor vehicle 11, for example. The driver assistance system 10 contains a camera 13 for recording the environment of the motor vehicle 11. The camera 13 here is a digital video camera. The camera 13 takes pictures of the environment of the motor vehicle 11. The camera 13 is arranged in a front area of the motor vehicle 1]. and records the environment ahead of the motor vehicle 11 in the direction of a forward driving direction 14 of the motor vehicle 11. The motor vehicle 11 has a control device 15, which controls functions of the motor vehicle 11. The control device 15 can in particular control an adaptation of a driving speed of the motor vehicle 11 to the estimated distance to the object 12. The control device 15 contains inter alia a picture processing device 16 for processing picture information fed to it by the camera 13. The picture processing device 16 is connected to the camera 13 for this purpose. The picture information fed to the picture processing device 16 from the pictures recorded by the camera 13 is analysed by the picture processing device 16, in particular to locate objects such as the object 12 which are in the environment of the motor vehicle 11. The picture processing device 16 is likewise part of the driver assistance system 10.

The motor vehicle 11 drives in the present embodiment on a road 17, which has a particular progression, especially in the forward direction 14. The road 17 here represents a surface on which the motor vehicle 11 is moving. The road 17 has a certain elevation profile in a vertical direction 18 in its progression. Thus the vertical height of the road surface of the road 17 changes in the progression of the road 17. In figure 1, the road 17 has a level first road surface 19 running horizontally, on which the motor vehicle 11 is located in the driving situation shown. In the further progression of the road 17 in a forward direction 14, a second road surface 20 adjoins the first road surface 19, the vertical height of which second surface first rises linearly compared with the height of the first road surface 19, then drops away again with a curvature, in order eventually to attain the height of the first road surface 19 again. In the representation according to figure 1, in addition to the progression of the second road surface 20, an extension of the horizontal progression of the first road surface 19 is represented by a dotted line for visualization reasons. In the embodiment according to figure 1, the object 12 is located on the second road surface 20 at a point 21 of the second road surface 20 with the greatest height in a vertical direction 18. The point 21 is elevated by a vertical height 22 relative to the first road surface 19. A lower edge 23 of the object 12 is therefore elevated by the height 22 relative to the first road surface 19, and thus to the lowest points of the motor vehicle 11, i.e. the lowest points of the tyres of the motor vehicle 11.

The driver assistance system 10 contains a digital storage medium, which here is a CD-ROM 24. The CD-RON 24 contains a digital map with digital landscape and Street plans.

This digital map is filed on the CD-ROM 24 in the form of digital data, which are compiled in a database. The digital map contains progressions of roads in particular.

The digital map also contains according to the invention elevations of the progressions of the roads. These elevations can have an accuracy or interpolation point range of the elevation profile of approx. 1 m in the present embodiment. The digital map thus likewise contains height data about the progression of the road 17. The elevation profile of the road 17 is contained in the digital map with the above-mentioned accuracy. The driver assistance system 10 contains a reading device 25, with which the digital map stored on the CD-ROM 24 can be read.

In particular, the reading device 25 can read the elevations of the progression of the road 17. The information read from the digital map is transmitted to the control device 15, which uses the elevations of the progression of the road 17 that are read and transmitted to estimate the distance between the motor vehicle 11 and the object 12. The motor vehicle 11 also has a satellite-aided navigation system 26, which is integrated into the control device 15 and with which the position of the motor vehicle 11, in particular on the road 17, can be determined.

The camera 13 is fixedly installed in the motor vehicle 11.

It has a distinct position which is known to the control device 15 and is taken into account by this to estimate the distance. In the present embodiment, a height 27 in particular of the camera 13 in the motor vehicle 11 is known. This directly results in a height of the camera 13 relative to the road 17 on which the motor vehicle 11 is travelling. This height largely corresponds to the height 27. Furthermore, an orientation angle or angle of inclination 28 is known, by which the camera 13 is arranged inclined towards the horizontal in the motor vehicle 11.

These data give the position of the camera 13 with reference to the first road surface 19. Figure 1 illustrates a recording or mapping range of the camera 13, which range can be covered by the camera 13 when recording a picture of the environment of the motor vehicle 11. This recording or mapping range determines inter alia a picture upper edge line 29 and a picture lower edge line 30 of the picture taken by the camera 13 in its specific position.

In figure 1, furthermore, starting out from the camera 13, a line 31 running horizontally can be seen, which substantially represents the mapping of the horizon.

Starting out from the camera 13, a further line 32 runs to the lower edge 23 of the object 12 at the highest point 23.

of the second road surface 20 and intersects the extension.

represented by a dashed line, of the first road surface 19 running horizontally at a point of intersection 33.

Figure 2 shows a schematic representation of a recording of a picture 34 by the camera 13 of the driver assistance system 10 according to figure 1. The picture 34 reproduces an illustration of the recorded environment of the motor vehicle 11 projected into a plane. An upper edge 35 of the picture and a lower edge 36 of the picture, which delimit the picture 34 taken by the camera 13 at the top and bottom respectively, result from the picture upper edge line 29 and the picture lower edge line 30 according to figure 1.

Furthermore, the picture 34 is delimited laterally by two lateral edges 37 and 38. A horizontal picture line 39 of the picture 34 reproduces pixel picture information at the horizon. The horizontal picture line 39 results from the horizontal line 31 according to figure 1. An object line 40 of the picture 34 reproduces pixel picture information at the height of the lower edge 23 of the object 12. The object line 40 results from the further line 32 according to figure 1. The road 17, its centre line and its progression in a forward direction 14 as well as the object 12 are also shown in figure 2. The object 12 is determined by means of the picture processing device 16 from the picture information of the picture 34. For the sake of simplicity it can suffice here to locate the lower edge 23 of the object 12. The picture processing device 16 contains a suitable algorithm for this purpose with which the picture information of the picture 34 can be analysed.

Each line, i.e. pixel line, of the picture 34 corresponds to a certain distance of what is recorded and shown in the picture 34 from the camera 13, i.e. from the motor vehicle 11. The horizontal line 39 corresponds in this case to an infinitely great distance and the lower edge 36 of the picture to a smallest determinable distance from the motor vehicle 11. The other lines of the picture 34 correspond to distances lying in between. The control device 15 is formed so that it can infer spatial distances from the motor vehicle 11 from the vertical positions of the lines in the picture 34* The control device 15 can accordingly estimate the distance of the lower edge 23 of the object 12 from the motor vehicle 11 on the basis of the data supplied to it, e.g. regarding the position of the camera 13, by means of the vertical position of the object line 40, in particular in relation to the vertical position of the horizontal picture line 39. In this estimate, the elevation that indicates the height 22 of the point 21 at which the lower edge 23 of the object 12 is located on the second road surface 20 is taken into account according to the invention. The elevations of the elevation profile of the entire progression of the road 17 between approximately the position of the motor vehicle 11 and the horizon are used advantageously in the present embodiment to estimate the distance of the object 12 from the motor vehicle 11.

When estimating the distance, the assumption is made here that the position of the lower edge 23 of the object 12 reproduces the position of the object 12 at least approximately, so that reference is made to the lower edge 23 when determining the distance. The control device 15 thus estimates the distance between the motor vehicle 11 and the object 12, i.e. its lower edge 23, and in doing so ascertains an estimated distance 41.

To clarify the advantages of the present invention, figure 2 shows a distance estimating error 42, which would occur when estimating the distance between the motor vehicle 11 and the object 12 if the height data on the progression of the road 17 were not taken into consideration. In this case, as above, the assumption is made that the lower edge 23 of the object 12 is located on the road surface. The control device 15 would therefore assume in this case that the lower edge 23 of the object 12 is located at the intersection position 33. Starting out from this, the control device 15 would estimate a distance 43 of the motor vehicle 11 from the object 12. The difference between the distance 41 and the distance 43 is the distance estimating error 42. The control device 15 would thus estimate the distance 43 to be greater when estimating without taking account of the elevations than the distance 41 when the elevations are taken into account.

Taking the elevations into account is thus particularly advantageous in this case and increases the safety both of the occupants of the motor vehicle 11 and of the occupants of the other motor vehicle travelling in front, as represented by the object 12.

Claims

Claims 1. Method for estimating a distance (41) of a vehicle (11) to an

object (12) in the environment of the vehicle (11), characterized in that the distance (41) is estimated by means of elevations of a progression of a surface (17) on which the vehicle (11) is moving.
2. Method according to claim 1, characterized in that the elevations of the surface (17) are inferred from a digital map.
3. Method according to claim 2, characterized in that the digital map is stored on a digital storage medium (24) and the elevations are read from the digital storage medium (24).
4. Method according to one of the preceding claims, characterized in that the distance (41) is estimated by means of the elevations of that progression of the surface (17) which the surface (17) has between approximately a position of the vehicle (11) on the surface (17) and a horizon.
5. Method according to one of the preceding claims, characterized in that picture information about the environment of the vehicle (11) is acquired by a camera (13) and the picture information is processed by a picture processing device (16).
6. Driver assistance system for a vehicle (11) for estimating a distance (41) of the vehicle (11) to an object (12) in the environment of the vehicle (11), characterized in that the driver assistance system is formed to estimate the distance (41) by means of elevations of a progression of a surface (17) on which the vehicle (11) is moving.
7. Driver assistance system (10) according to claim 6, characterized in that it is formed to take the elevations of the surface (17) from a digital map.
8. Driver assistance system according to claim 7, characterized in that it has a reading device (25) for reading a digital storage medium (24) and the digital map is stored on such a digital storage medium (24).
9. Driver assistance system according to one of claims 6- 8, characterized in that the driver assistance system (10) is formed to estimate the distance (41) by means of the elevations of that progression of the surface (17) which the surface (17) has between approximately a position of the vehicle (11) on the surface (17) and a horizon.
10. Driver assistance system according to one of claims 6- 9, characterized in that a camera (13) for acquiring picture information on the environment of the vehicle (11) and a picture processing device (16) for processing the picture information are present.
11. Method substantially as herein before described, with reference to the accompanying drawings.
12. Driver assistance system substantially as herein before described, with reference to the accompanying drawings.