Method for avoiding collision between vehicle and obstacle and driving assistance system

Abstract

The invention relates to a method for avoiding a collision of a vehicle (10) with an obstacle (11) using at least one ultrasonic sensor (12). In the method, reflection points (14) are determined during the movement of the vehicle (10), wherein the reflection points (14) represent locations at which signals of the ultrasonic sensor (12) are reflected. The reflection points (14) are combined into a continuous, linearly extending wall segment (20), wherein a wall segment (20) has two ends. Furthermore, it is determined whether the ends of the wall segment (20) are open or closed. The course adjacent to the open end (24) of the wall segment (20) is extrapolated and a virtual collision point (32) between the vehicle (10) and the extrapolated course of the wall segment (20) is determined. If a collision with the virtual collision point (32) is imminent, a braking intervention is initiated. Further aspects of the invention relate to a driver assistance system having at least one ultrasonic sensor (12), which is configured to carry out the method, and to a vehicle (10) having such a driver assistance system.

Description

Technical Field

[0001] The present invention relates to a method for avoiding a collision between a vehicle and an obstacle, wherein the distance between the vehicle and an obstacle in the vehicle's surroundings is determined by at least one ultrasonic sensor, in that the at least one ultrasonic sensor sends a signal and receives an echo of the signal reflected at the obstacle. The present invention also relates to a driver assistance system for avoiding a collision between a vehicle, the driver assistance system comprising at least one ultrasonic sensor for determining the distance between the vehicle and an obstacle in the vehicle's surroundings, and the driver assistance system is configured to implement the method. Background Art

[0002] In the automotive sector, various driver assistance systems are used that are intended to assist the driver when carrying out various driving maneuvers. For example, these include parking assistance systems that use sensors assigned to the vehicle to sense the surroundings, find possible parking spaces in the surroundings, and assist the driver when parking. Other driver assistance systems, for example, warn the driver of objects that are located in the blind spot. Some driver assistance systems include a braking function that brakes the vehicle before a collision occurs.

[0003] DE 10 2014 111 951 A1 discloses a method for warning a driver of a motor vehicle of the presence of an object in the surroundings. In this method, a minimum distance between the motor vehicle and the object is continuously determined, wherein a warning is output when the minimum distance falls below a predetermined limit value. In addition, a collision distance is continuously determined, which describes the distance between the motor vehicle and the object when the motor vehicle moves in the determined driving path.

[0004] DE 10 2013 021 827 A1 discloses a method for warning a driver of a motor vehicle of a collision risk. In this method, in addition to objects in the vehicle's driving path, objects in a warning area outside the driving path are also taken into account. For example, when driving in reverse, the warning area can be defined in the area of ​​the left front corner of the motor vehicle. In this way, for example, a collision with an elongated object located on the left side of the vehicle can be avoided, but the part of the elongated object that protrudes into the driving path is outside the detection range of the sensors of the motor vehicle.

[0005] A disadvantage of the prior art is that a collision with an object protruding into the driving path of the vehicle is usually detected very late, so that it is usually no longer possible to avoid the collision by braking. Summary of the invention

[0006] A method for avoiding a collision between a vehicle and an obstacle is proposed, wherein the distance between the vehicle and an obstacle in the vehicle's surroundings is determined by at least one ultrasonic sensor in that the at least one ultrasonic sensor sends a signal and in turn receives an echo of the signal reflected by the obstacle.

[0007] In the method, it is provided that in step a) of the method reflection points are determined during the movement of the vehicle, wherein the reflection points represent locations at which the signals of the ultrasonic sensor are reflected. In a subsequent step b) of the method, the determined reflection points are assigned to the object. In this case, the reflection points are particularly summarized as continuous, linearly extending wall segments, wherein a wall segment has two ends.

[0008] In the next step c) of the method it is determined whether one end of the wall segment is open or closed. If the reflection points adjoining one end follow a nonlinear trend or if no further reflection points converge with the corresponding end of the wall segment during further movement of the vehicle, the end of the wall segment is considered to be closed. Otherwise, the end of the wall segment is considered to be open.

[0009] In a subsequent step d) of the method, for wall objects having at least one open end, an extrapolation of the path following the open end is performed. In a subsequent step e) of the method, a virtual collision point between the vehicle and the extrapolated path of the wall segment is determined. In a subsequent step f) of the method, a braking intervention is performed if the vehicle is about to collide with the virtual collision point.

[0010] In order to determine the reflection points according to step a) of the method, for example, an ultrasonic sensor sends a signal and the sensor receives an ultrasonic echo reflected by an object in the surroundings. For each received ultrasonic echo, the distance of the object relative to the vehicle is determined based on the propagation time between the signal transmission and the echo reception. In addition to the determined distance or distance value, the distance determined for forming the reflection point is also assigned a time point and / or a reference to the distance traveled by the vehicle. In this way, the following trend can be generated from these reflection points: in this trend, a correlation between the measured distance and the time of measuring the distance and / or a correlation with the distance traveled by the vehicle is established.

[0011] If at least two ultrasonic sensors are used, whose detection ranges that can perceive the echoes of these objects overlap at least partially, then by measuring the distance to the object by means of the two ultrasonic sensors and by means of the subsequent least square method, not only the distance between the vehicle and the reflecting object can be determined, but also the relative position of the object or the reflection point relative to the vehicle can be determined. In this case, it is preferred that the time of receiving the echo and the position of the reflection point relative to the vehicle are assigned to the reflection point in order to form the trend of the reflection points.

[0012] In step b) of the method, the determined reflection points are grouped into objects. For this purpose, the course of the reflection points can be analyzed, for example, using a tracking filter, wherein reflection points that are closely adjacent to one another are grouped into one object. In order to combine the reflection points, it can be provided, for example, that a virtual surroundings map is created. In this surroundings map, a location is entered for each reflection point. In particular, the distances or positions recorded for a given reflection point relative to the vehicle and the corresponding vehicle position at the time of the measurement are used to create the surroundings map.

[0013] In the method, it is particularly provided that these reflection points are merged into a continuous, linearly extending wall segment. When using a tracking filter that summarizes these reflection points or the locations representing the reflection points into objects, objects with an elongated shape or objects whose merged reflection points are located on a line are regarded as such a wall segment. Each wall segment has a first end and a second end. A wall segment includes at least three reflection points, preferably, a wall segment has at least four reflection points, particularly preferably at least five reflection points.

[0014] The wall segments determined belong to an obstacle or object in the vehicle's surroundings, wherein the wall segment is always a linear extension of the object's contour. The object can be an elongated object, such as a guardrail, a wall or a fence. Or it can be a linear portion of the object's contour. For example, the contour of the vehicle contains such a segment: when the segment is scanned by the ultrasonic sensor, the segment appears linear and elongated. The object or obstacle is preferably stationary. However, the method can be applied to dynamic objects, i.e. moving objects.

[0015] In the further course of the method, a distinction is made between an open end and a closed end of a wall segment. In the case of a closed end of a wall segment, the end of the wall or the end of the object has been detected and the object cannot be extended further in this direction. In the case of an open end of a wall segment, only a part of the wall or the object is initially seen, and the complete extension of the object or the wall is still unknown. In order to distinguish between an open end and a closed end, it is determined whether the reflection point immediately following or adjacent to the corresponding end in the end region of the wall segment follows a nonlinear trend. This nonlinear trend indicates that the end of the linearly extending wall segment of the object has been reached and the contour of the object is bent. In particular, a nonlinear trend is a curved curve that bends away from the direction of movement of the vehicle, and this nonlinear trend indicates the edge of the object, which is the end of the linear wall segment.

[0016] In the case of elongated objects, such as guardrails, walls or fences, this nonlinear course cannot be observed in some cases. In this case, it is instead determined that, even when the vehicle moves further in its direction of travel, no further reflection points are determined, which can merge with the corresponding ends of the wall segment.

[0017] In all other cases it is assumed that the corresponding end of the wall segment is open.

[0018] If the wall segment has an open end, the method now determines whether a collision between the vehicle and one of the wall segments is imminent. To this end, the open ends of the wall segments are extended by extrapolation and a virtual collision point is checked between these extended wall segments and the travel path that represents the expected movement of the vehicle. The travel path is represented by two lines running parallel to each other, which delimit the area that the vehicle is expected to pass through as long as the current speed and direction are maintained. The travel path depends on the speed, viewing direction and size of the vehicle. If one of the extrapolated ends of the wall segment intersects the line delimiting the travel path, a virtual collision point is generated at this intersection.

[0019] If a virtual collision point is determined, a braking intervention is taken in the event of an imminent collision with the virtual collision point. In particular, a collision is imminent when the distance between the virtual collision point and the vehicle is below a warning distance. The warning distance can be varied depending on the vehicle speed and is preferably selected such that during the braking intervention, it is ensured that the vehicle is braked before reaching the virtual collision point even with a small vehicle deceleration.

[0020] Of course, in addition to the virtual collision point, other conditions for taking a brake intervention can also be defined. It is therefore preferably provided that a brake intervention is taken when a reflection point located in the driving path is identified and thus an obstacle is directly encountered in the driving path.

[0021] In the braking intervention according to step f), it is preferably provided that emergency braking is initiated with maximum deceleration if this is necessary to avoid the collision with the virtual collision point or to reduce damage that would occur in the event of a collision. If emergency braking is not yet necessary, it is preferred that comfortable vehicle braking is performed with a deceleration that is less than the maximum deceleration of the vehicle during the braking intervention. This deceleration, which is less than the maximum possible deceleration of the vehicle, achieves particularly comfortable braking, wherein the distance to the point at which emergency braking must be initiated is reduced and thus more time is available to find a potential closed end of the wall segment.

[0022] The deceleration selected for comfort braking is preferably selected such that the vehicle is braked to a standstill shortly before the virtual collision point.

[0023] Preferably, the method provides that after a braking intervention, the vehicle's surroundings are further observed, reflection points are determined and these are combined into wall segments. It is possible that, for a wall segment that previously had an open end, this end is detected and therefore now has a closed end. In this case, the previously determined virtual collision point disappears if necessary. In addition, in particular when the vehicle completes a steering movement, the virtual collision point is recalculated, whereby collision points may disappear if necessary and new collision points may be generated.

[0024] Preferably, the initiated comfort braking is terminated and the actuated brake is thus also released again when the virtual collision point responsible for the vehicle deceleration disappears.

[0025] The method is preferably carried out repeatedly with steps a) to f) of the method during the movement of the vehicle, so that the surroundings are continuously monitored, a new collision point is ascertained if necessary, and the ascertained virtual collision point disappears again if necessary.

[0026] Another aspect of the present invention is to provide a driver assistance system for avoiding a collision between a vehicle and an obstacle. The driver assistance system comprises at least one ultrasonic sensor for determining a distance between the vehicle and an obstacle in the vehicle's surroundings, and the driver assistance system is configured to implement the method described herein.

[0027] The driver assistance system preferably includes a control unit which is connected to at least one ultrasonic sensor and has a connection to a vehicle brake system. The control unit preferably carries out the method described here.

[0028] In a preferred embodiment, the driver assistance system has a plurality of ultrasonic sensors, wherein at least two ultrasonic sensors are particularly preferably arranged such that their detection ranges, which can detect objects in the vehicle's surroundings, overlap at least partially. In this overlapping area, when using these two ultrasonic sensors, not only can the distance between the object and the vehicle be determined, but also the position of the object or the reflection point on the object relative to the vehicle can be determined using the least squares method.

[0029] The invention also relates to a vehicle comprising a driver assistance system described here.

[0030] Advantages of the present invention:

[0031] With the proposed method, in many cases a possible collision of the vehicle with an object can already be determined, even though the vehicle's sensors have not yet detected an obstacle protruding into the vehicle's path of travel. This early detection of a possible collision is preferably used to initially brake the vehicle gently and comfortably for the passengers, since braking can already be initiated early due to the early detection of an impending collision. Full braking or emergency braking is only necessary if the distance to the obstacle decreases faster than initially expected, for example due to an incorrect steering movement by the driver.

[0032] Furthermore, a braking intervention which was initially carried out gently and comfortably can also be advantageously ended again, for example when it can be verified that a collision is not imminent at all due to the detection of the end of the wall segment, or an imminent collision can be avoided by a suitable steering movement of the driver. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 shows driving past a stationary obstacle, and

[0034] Figure 2 Indicates an impending collision with a stationary obstacle.

[0035] In the following description of exemplary embodiments of the present invention, identical elements are labeled with identical reference numerals, wherein a repeated description of these elements is omitted in individual cases. The contents of the present invention are only schematically illustrated in the drawings. DETAILED DESCRIPTION

[0036] exist Figure 1 1 shows a vehicle 10 having a driver assistance system according to the invention, which moves in a direction denoted by reference numeral 36. Based on the direction of movement 36, the speed and the size of vehicle 10, a driving corridor is determined, which is bounded by two boundary lines 30.

[0037] exist Figure 1In the exemplary embodiment shown in FIG. 1 , the vehicle 10 has six ultrasonic sensors 12 for monitoring the surroundings of the vehicle 10 . To this end, the ultrasonic sensors 12 each send an ultrasonic pulse and receive an ultrasonic echo reflected from an object. Figure 1 In FIG. 1 , an obstacle 11 is shown in the form of a stationary vehicle. The obstacle 11 is an object that reflects the signal sent by the ultrasonic sensor 12. For each reflected echo, the vehicle 10 or the driver assistance system assigned to the vehicle 10 determines a distance 18. If the ultrasonic sensors 12 are able to detect objects in a field of view that at least partially overlap, the exact position of the point that reflects the ultrasonic wave relative to the vehicle 10 can also be determined with the aid of the least squares method. For this purpose, the distance 18 measured by the two participating ultrasonic sensors 12 and the known distance between the two ultrasonic sensors 12 are required.

[0038] Based on the ascertained sensor data of ultrasonic sensor 12, a surroundings map is created, in which reflection points 14 are entered, which each represent the location where the corresponding ultrasonic signal was reflected by obstacle 11. If an exact determination of the position of reflection point 14 is not possible, for example because only a single ultrasonic sensor 12 receives the corresponding echo, a curve of reflection point 14 can be created, in which the ascertained distance 18 is plotted as a function of the measurement time and / or the distance traveled by vehicle 10.

[0039] Now, according to this trend or according to the created surroundings map, these reflection points 14 are grouped into objects, wherein these reflection points 14 are in particular combined into a continuous, linearly extending wall segment 20. In this case, reflection points 14 that are closely adjacent to each other in the surroundings map or in this trend are grouped into a wall segment 20. In this case, two reflection points 14 can be regarded as being closely adjacent to each other if the distance between them is less than a predefined threshold value.

[0040] The continuous, linearly extending wall section 20 produced by the combination of the reflection points 14 has two ends. Figure 1 In the example shown in , both ends are closed ends 26 , since the corresponding reflection points 14 following the closed ends 26 do not follow the rectilinear course of the remaining reflection points 14 of the wall segment 20 further away from the vehicle 10 .

[0041] Since the two ends of the wall section 20 are closed, no extrapolation is performed on the further course of the wall section 20. Since the two boundary lines 30 that delimit the driving path of the vehicle 10 also do not intersect the wall section 20, no collision point can be determined. This wall section is not exposed to a collision between the vehicle 10 and the obstacle 11.

[0042] exist Figure 2 Shown in Figure 1 The vehicle 10 moves in the direction marked by the reference numeral 36, wherein the driving path of the vehicle 10 is again limited by two boundary lines 30. Figure 1 In contrast to the situation shown in , vehicle 10 is no longer moving parallel to obstacle 11 , but rather is moving at an angle relative to the obstacle.

[0043] While vehicle 10 is moving, signals are continuously emitted by ultrasonic sensor 12 and echoes are received again, wherein a distance 18 is again assigned to each echo and reflection point 14 is determined.

[0044] As from Figure 2 As can be seen in the illustration of , the determined reflection points 14 are summarized into a wall section 20, which has a closed end 26. The closed end 26 is characterized in that the distance 18 of the reflection points 14 following the closed end 26 relative to the vehicle 10 increases, so that the position of the reflection points 14 adjacent to the closed end 26 does not follow a linear curve. The reflection points 14 adjacent to the closed end 26 are not located on a straight line through the reflection points 14 assigned to the wall section 20.

[0045] The other end of the wall segment 20 is an open end 24, since all the reflection points 14 determined so far in the vicinity of the open end are located on a straight line defined by all the reflection points 14 of the wall segment 20. Therefore, an extrapolation is performed, so that the further course of the wall segment 20 is estimated by the extrapolated straight line 28. Figure 2 In the illustration of FIG. 1 , the extrapolated straight line 28 intersects one of the boundary lines 30 that delimit the driving path of the vehicle 10 . A virtual collision point 32 is formed at the intersection. The distance between the vehicle 10 and the virtual collision point 32 is marked with the reference numeral 34 .

[0046] Based on the recognition of the virtual collision point 32, a braking intervention is performed, wherein the vehicle 10 is preferably braked gently and comfortably. For comfortable braking, the deceleration is selected so that the vehicle 10 stops shortly before the virtual collision point 32. If the driver of the vehicle 10 changes the direction of movement 36 of the vehicle 10 by a steering movement so that the virtual collision point 32 disappears, the braking intervention is terminated so that the driving of the vehicle 10 can continue without interruption.

[0047] Advantageously, virtual collision point 32 is detected before reflection point 14 located in the driving path of vehicle 10 is ascertained using ultrasonic sensor 12. This early detection of virtual collision point 32 allows braking intervention to be initiated earlier and thus braking to be performed with a small, comfortable deceleration.

[0048] If the angle between the vehicle 10 and the obstacle 11 is small, so that the virtual collision point 32 is further away from the obstacle 11 and is located outside it, the vehicle 10 determines further reflection points 14 using its ultrasonic sensor 12 during comfort braking and further combines them into a wall segment 20. If the end of the obstacle 11 is then reached during the further course, a nonlinear course of the reflection points 14 is determined with respect to the straight line through the reflection points 14 assigned to the wall segment 20. This is interpreted as a closed end 26 of the wall segment 20, so that the determination of the extrapolated straight line 28 is not performed, and thus the virtual collision point 32 also disappears. This means that in this case, the vehicle 10 initially brakes cautiously until the ultrasonic sensor 12 detects the end of the wall segment 20 as closed and thus the end of the obstacle 11. Since an impending collision can then be ruled out, the vehicle 10 continues its travel in this case without hindrance and the comfort braking ends.

[0049] The invention is not limited to the embodiments described herein and the aspects emphasized therein. Rather, many variations can be realized within the scope of the claims that are within the scope of the usual technical means of a person skilled in the art.

Claims

1. A method for avoiding a collision between a vehicle (10) and an obstacle (11), wherein: The method comprises determining a distance (18) between the vehicle (10) and an obstacle (11) in the surroundings of the vehicle (10) by means of at least one ultrasonic sensor (12), wherein the at least one ultrasonic sensor (12) transmits a signal and in turn receives an echo of the signal reflected by the obstacle (11), the method comprising the following steps: a) determining a reflection point (14) during movement of the vehicle (10), wherein the reflection point (14) represents a location where a signal of the ultrasonic sensor (12) is reflected; b) merging the reflection points (14) into a continuous, linearly extending wall segment (20), wherein a wall segment (20) has two ends; c) determining whether an end of the wall segment (20) is open or closed, wherein the end of the wall segment (20) is considered closed if the reflection points (14) adjacent to the corresponding end follow a non-linear trend or if no further reflection points (14) merge with the corresponding end of the wall segment (20) during further movement of the vehicle (10), and otherwise the end is open; d) extrapolating the course of the wall section (20) immediately following the open end (24); e) determining a virtual collision point (32) between the extrapolated course of the vehicle (10) and the wall segment (20), wherein the virtual collision point (32) is determined as the intersection point between a straight line (28) obtained by extrapolating the wall segment (20) and a boundary line (30) of the driving path of the vehicle (10); and f) If a collision with the virtual collision point (32) is imminent, a braking intervention is performed.

2. The method according to claim 1, characterized in that In step f), if emergency braking with maximum deceleration is necessary to avoid a collision with a virtual collision point (32) or to reduce damage, emergency braking with maximum deceleration is performed, or, if emergency braking is not yet required, comfort braking of the vehicle (10) is performed at a deceleration less than the maximum deceleration of the vehicle (10).

3. The method according to claim 2, characterized in that The deceleration for comfort braking is selected such that the vehicle (10) is braked to a standstill before reaching the virtual collision point (32).

4. The method according to claim 2 or 3, characterized in that: When the virtual collision point (32) responsible for the deceleration disappears, comfort braking is terminated and the brake is released again.

5. The method according to any one of claims 1 to 3, characterized in that The non-linear course according to step c) is a curved curve which curves away from the direction of movement (36) of the vehicle (10).

6. The method according to any one of claims 1 to 3, characterized in that The driving corridor is derived from the instantaneous driving direction, the instantaneous steering angle and the size of the vehicle (10).

7. The method according to any one of claims 1 to 3, characterized in that Steps a) to f) are repeated while the vehicle (10) is in motion.

8. A driving assistance system for avoiding a collision between a vehicle (10) and an obstacle (11), wherein: The driver assistance system comprises at least one ultrasonic sensor (12) for determining a distance (18) between the vehicle (10) and an obstacle (11) in the surroundings of the vehicle (10), and is designed to carry out a method according to any one of claims 1 to 7.

9. A vehicle (10) comprising a driving assistance system according to claim 8.

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