DE102018131898B4 - Method for determining a trajectory by tangentially applying Bézier curves to geometric structures; control unit; driver assistance system; computer program product and computer-readable medium - Google Patents

Abstract

Method for determining a trajectory (5) for steering a motor vehicle (1) during a driving maneuver in an area (U) surrounding the motor vehicle (1), comprising the steps: - determining a boundary (8) for a possible driving corridor of the motor vehicle (1) in a virtual maneuvering space (16), - determining a starting position (11) and an end position (12) for the motor vehicle (1) with respect to the driving maneuver in the virtual maneuvering space (16), - arranging a predefined geometric structure (9) in a predetermined relative position with respect to the boundary (8) in the virtual maneuvering space (16), - determining a tangent (10) to the geometric structure (9), - connecting a point of tangency (17) of the tangent (10) with both the starting position (11) and the end position (12) with a respective Bézier curve (6, 7), wherein the respective Bézier curves (6, 7) intersect at the point of tangency (17) run parallel to the tangent (10) and the respective Bézier curves (6, 7) together form the trajectory (5).

Description

The invention relates to a method for determining a trajectory for steering a motor vehicle during a driving maneuver in the vicinity of the motor vehicle. The invention also relates to a control unit for determining a trajectory and a driver assistance system for steering a motor vehicle. Further aspects of the invention relate to a computer program product and a computer-readable medium.

To control a motor vehicle, especially for autonomous control, it is known to first determine a trajectory for a future journey or maneuver. Specifically, the trajectory provides the path along which the vehicle is to move from a starting position to an end position. For example, the trajectory is determined or calculated based on the starting position, the end position, and boundaries in the vehicle's surroundings. Examples of such boundaries include other road users, such as other vehicles, cyclists, and pedestrians, as well as parked vehicles, lane markings, curbs, and/or any other objects. The maneuver itself could, for example, be a parking maneuver.

Determining a trajectory in the form of a Bézier curve is, for example, derived from the EP 2 091 803 B1 as from the US 2010/00 85 170 A1 This is well known. However, in many cases it is not possible to find a simple Bézier curve from the starting position to the end position. In this case, the combination of two or more Bézier curves is necessary. These multiple Bézier curves can each be referred to as Bézier segments.

The object of the present invention is to enable a more resource-efficient calculation of a trajectory using several Bézier curves.

This problem is solved according to the invention by the subject matter of the independent claims. Advantageous embodiments and expedient further developments are the subject matter of the dependent claims.

• - Bestimmen einer Begrenzung für einen möglichen Fahrkorridor des Kraftfahrzeugs in einem virtuellen Manöverraum,
• - Bestimmen einer Startposition sowie einer Endposition für das Kraftfahrzeug in Bezug auf das Fahrmanöver in dem virtuellen Manöverraum,
• - Anordnen einer vorgegebenen geometrischen Struktur in einer vorbestimmten Relativposition in Bezug auf die Begrenzung in dem virtuellen Manöverraum,
• - Bestimmen einer Tangente für die geometrische Struktur,
• - Verbinden eines Berührpunkts der Tangente sowohl mit der Startposition als auch der Endposition mit einer jeweiligen Bézierkurve, wobei die jeweiligen Bézierkurven in dem Berührpunkt beide parallel zu der Tangente verlaufen und die jeweiligen Bézierkurven gemeinsam die Trajektorie bilden.

A first aspect of the invention relates to a method for determining a trajectory for steering a motor vehicle during a driving maneuver, in particular a parking maneuver, in an area surrounding the motor vehicle, comprising the following steps:

• - Determining a boundary for a possible driving corridor of the motor vehicle in a virtual maneuvering area,
• - Determining a starting position and an end position for the motor vehicle in relation to the driving maneuver in the virtual maneuvering space,
• - Arranging a given geometric structure in a predetermined relative position with respect to the boundary in the virtual maneuvering space,
• - Determining a tangent to the geometric structure,
• - Connecting a point of tangency of the tangent with both the starting position and the end position with a respective Bézier curve, wherein the respective Bézier curves at the point of tangency both run parallel to the tangent and the respective Bézier curves together form the trajectory.

The potential driving corridor can, for example, be modeled on an area of the surrounding environment that the vehicle sweeps over during the maneuver. Additionally, the potential driving corridor can be larger than the area of the surrounding environment swept over by a predetermined safety margin. The potential driving corridor thus defines in which parts of the environment movement of the vehicle is possible at all. For example, it identifies areas of the surrounding environment that are inaccessible to the vehicle due to their boundaries. Naturally, more than one boundary, and in particular a multitude of boundaries, can be defined within the virtual maneuvering space.

The starting position of the vehicle can correspond to its position at the beginning of the driving maneuver. For example, the vehicle is in the starting position while the trajectory is being determined. In this case, the current position of the vehicle can be defined as the starting position. Alternatively, the starting position can be defined as a position the vehicle will occupy at a later time.

The final position can be a target position for the vehicle at the end of the driving maneuver. For example, the final position is a desired position for the vehicle, into which the vehicle is to be steered during the driving maneuver. If the driving maneuver is a parking maneuver, the final position can be... position be a parking position in a previously selected parking space or parking area.

The virtual maneuvering area can be a map of the surrounding area. For example, a digital map of the surrounding area is created. The boundaries, starting position, and/or end position can be entered into this map for later processing. Alternatively, the virtual maneuvering area can be a geometric model of the surrounding area.

The given geometric structure can be a primitive geometric structure. For example, the given geometric structure could be a basic geometric structure. Examples of such basic structures are circles and/or straight lines. The given geometric structure can be positioned in a predetermined relative position to the boundary within the virtual maneuvering space. Additionally, one or more parameters can be specified for the geometric structure. In the case of a circle, such a parameter could be, for example, the radius or the length of a circular arc. In the case of a straight line, the parameter could define the length of the straight line.

The tangent is then drawn to the geometric structure. The tangent shares a common point of contact with the geometric structure. At this point of contact, the tangent runs parallel to the geometric structure.

The tangent can now be used as a construction aid for determining the respective Bézier curves. Specifically, it is intended that a Bézier curve is drawn from the point of tangency to the starting position and another to the end position. In other words, a first Bézier curve is determined that connects the point of tangency to the starting position, and a second Bézier curve is determined that connects the point of tangency to the end position. Both the first and second Bézier curves are parallel to the tangent at the point of tangency. In other words, the two Bézier curves intersect the given geometric structure at the point of tangency. At this point of tangency, both Bézier curves run parallel to the tangent.

The geometric structure significantly simplifies the problem of determining a multi-part trajectory composed of several Bézier curves. The geometric structure, specifically the tangent and its point of tangency, provides constraints that facilitate the determination of the individual Bézier curves. This allows for a particularly resource-efficient trajectory determination.

The present procedure can also be carried out multiple times using different predefined geometric structures. In other words, in different iterations of the aforementioned procedure steps, different geometric structures are arranged in the virtual maneuvering space, a corresponding tangent is determined for each structure, and at least two Bézier curves are calculated based on the tangent and its point of tangency. Subsequently, the trajectory can be determined based on the geometric structure that is most suitable according to a predetermined criterion. For example, the different geometric structures with different parameters can be arranged in the virtual maneuvering space. These geometric structures could, for instance, be circular arcs of different lengths and/or radii. In this case, the respective points of tangency of the tangents of the different circular arcs can be connected to the starting and ending positions using corresponding Bézier curves. Based on the respective geometric structure, a candidate trajectory can then be determined. The most suitable trajectory is then selected from the candidates using a selection process. Criteria for this can include, for example, the curvature and the distance of the respective trajectory candidate from the boundary. The curvature of the trajectory determines the steering angle when following the trajectory. In this way, a particularly suitable trajectory can be determined in a resource-efficient manner.

According to a further development approach, determining the tangent involves defining several potential tangents to the geometric structure and selecting one of these as the tangent. For example, several potential tangents are determined such that they touch the geometric structure at predetermined distances from each other. Alternatively or additionally, the potential tangents can be determined such that they differ by a maximum predetermined angle. This ensures that the potential tangents are placed at a reasonable distance from each other. Finally, one of the several potential tangents is selected as the tangent. This can be done, for example, by mapping the respective points of contact of the potential tangents to the starting position and The final position is connected. This attempt to connect unsuitable tangents may fail. Specifically, one can try to connect each of the respective points of tangency of the multiple potential tangents to the starting position with a first Bézier curve and to the final position with a second Bézier curve. Subsequently, the potential tangential curve with the most advantageous profile of the respective Bézier curves, according to a predetermined criterion, is selected. The selection criteria can be the aforementioned criteria, namely curvature and/or distance to the boundary. While using multiple potential tangents slightly increases resource consumption, this method allows for the determination of an improved trajectory.

According to further training, the driving maneuver is a parking maneuver, and a corner of a parking space is defined as the boundary. In other words, the vehicle is parked within the parking space during the maneuver. This is done autonomously. For example, the parking space may be bounded on two or three sides by lane markings. Parking is performed from one of the open sides of the parking space. Specifically, the corner defined as the boundary adjoins this open side. The parking maneuver can be performed in reverse. In other words, the vehicle is steered backward along the trajectory from the starting position to the final position during the parking maneuver.

According to a further development, a circular arc with a predetermined radius is arranged around the boundary as the geometric structure. In other words, a circular arc with the predetermined radius is aligned with the boundary as the geometric structure. A point on the boundary can form the center point of the circular arc. The predetermined radius can, in particular, depend on the space required by the vehicle during the maneuver. Specifically, the predetermined radius corresponds at least to the width of the vehicle plus a predetermined value for the safety distance. In this way, the geometric structure ensures that a suitable trajectory is determined, which is collision-free with respect to the boundary.

In particular, the circular arc with a predetermined radius is positioned around the corner of the parking space when the driving maneuver is a parking maneuver. This ensures that the parking trajectory can be determined in a particularly advantageous way.

• - eine weitere vorgegebene geometrische Struktur in einer vorbestimmten Relativposition in Bezug auf die Endposition in dem virtuellen Manöverraum angeordnet wird, ein Stützpunkt für diese weitere geometrischen Struktur bestimmt wird, und die jeweilige Bézierkurve von der Endposition zum Berührpunkt der Tangente der geometrischen Struktur derart bestimmt wird, dass die entsprechende Bézierkurve in dem Stützpunkt der weiteren geometrischen Struktur parallel zur der weiteren geometrischen Struktur verläuft.

According to a further training course, it is planned that

• - another predefined geometric structure is arranged in a predetermined relative position with respect to the end position in the virtual maneuvering space, a support point for this further geometric structure is determined, and the respective Bézier curve from the end position to the point of tangency of the geometric structure is determined such that the corresponding Bézier curve at the support point of the further geometric structure runs parallel to the further geometric structure.

In other words, the first Bézier curve, i.e., the respective Bézier curve, runs from the end position to the point of tangency of the geometric structure of the boundary, from the support point of the further geometric structure to the point of tangency of the geometric structure. At the point of tangency, the corresponding (first) Bézier curve is parallel to the respective tangent. At the support point, the corresponding (first) Bézier curve runs parallel to the further geometric structure. The further given geometric structure could be, for example, a circular arc and/or a straight line. In the case of a circular arc, another tangent can be determined through the support point. The further tangent for the further geometric structure can be determined analogously to the tangent for the geometric structure. In particular, the further tangent for the further geometric structure can be selected based on several potential tangents. In this case, the corresponding (first) Bézier curve runs parallel to the further tangent at the support point. The additional geometric structure makes it particularly advantageous to ensure that the motor vehicle assumes a desired orientation with respect to the final position at the end of the driving maneuver.

• - eine weitere vorgegebene geometrische Struktur in einer vorbestimmten Relativposition in Bezug auf die Startposition in dem virtuellen Manöverraum angeordnet wird,
• - ein Stützpunkt für diese weitere geometrischen Struktur bestimmt wird, und
• - die jeweilige Bézierkurve von der Startposition zum Berührpunkt der Tangente der geometrischen Struktur der Begrenzung derart bestimmt wird, dass die entsprechende Bézierkurve in dem Stützpunkt der weiteren geometrischen Struktur parallel zur der weiteren geometrischen Struktur verläuft.

Alternatively or additionally, it is planned that

• - another predefined geometric structure is arranged in a predetermined relative position with respect to the starting position in the virtual maneuvering space,
• - a support point for this further geometric structure is determined, and
• - the respective Bézier curve is determined from the starting position to the point of tangency of the geometric structure of the boundary in such a way that the corresponding Bézier curve runs parallel to the further geometric structure at the support point of the further geometric structure.

In other words, the second Bézier curve, i.e., the respective Bézier curve, runs from the starting position to the point of tangency of the boundary's geometric structure, from the support point of the additional geometric structure to the point of tangency of the geometric structure. At the point of tangency, the corresponding (second) Bézier curve is parallel to the respective tangent. At the support point, the corresponding (second) Bézier curve runs parallel to the additional geometric structure. The additional given geometric structure could be, for example, a circular arc and/or a straight line. In the case of a circular arc, another tangent can be determined through the support point. The additional tangent for the additional geometric structure can be determined analogously to the tangent for the initial geometric structure. In particular, the additional tangent for the additional geometric structure can be selected based on several potential tangents. In this case, the corresponding (second) Bézier curve runs parallel to the additional tangent at the support point. The additional geometric structure makes it particularly advantageous to ensure that the motor vehicle assumes a desired orientation with respect to the final position at the end of the driving maneuver.

In other words, the first Bézier curve, that is, the Bézier curve from the starting position to the point of tangency of the boundary's geometric structure, can be determined such that it passes through the point of tangency of the other geometric structure as well as through the point of tangency of the geometric structure itself. Specifically, the first Bézier curve is parallel to the respective tangent at both points of tangency. In this way, the vehicle's orientation at the starting position can be taken into account when planning the trajectory.

Both of the aforementioned advanced training methods can, of course, be combined. In other words, further predefined geometric structures can be determined for both the starting and ending positions. In this case, a particularly suitable tangent for the driving maneuver can be determined.

According to a further development, it is provided that a steering angle of the motor vehicle is determined and a circular arc, the curvature of which is derived from the steering angle, is arranged as the further geometric structure for the starting position in the virtual maneuvering space.

In other words, the geometric structure allows the current steering angle of the vehicle in the starting position to be taken into account.

According to further training, a straight line is intended to serve as the additional geometric structure for the starting position and/or the end position within the virtual maneuvering space. If the aforementioned circular arc is used as the additional geometric structure for the starting position within the virtual maneuvering space, the straight line can, of course, optionally be used only for the end position. In the case of a straight line as the additional geometric structure, the tangent is not a tangent in the geometric sense. Nevertheless, one or more support points can be arranged on the additional geometric structure in a similar manner. At these support points, which are analogous to the points of tangency of the tangent, the respective Bézier curve can be connected to the point of contact of the geometric structure of the boundary. The respective Bézier curve then runs parallel to the straight line at the corresponding support point. The straight line allows the trajectory to be adapted even more precisely to the driving maneuver.

According to a further development approach, the trajectory is only checked for drivability, specifically regarding the maximum steering angle of the vehicle or its collision-free status, after it has been determined. Specifically, the tangent is first determined using the respective Bézier curves, and only then, for example, through a simulation of driving along the trajectory, is it checked whether the trajectory is collision-free and/or does not exceed the maximum steering angle of the vehicle. Drivability is considered given, for example, if the trajectory can be driven by the vehicle without collision and its maximum steering angle is not exceeded. Only if the trajectory is drivable can it subsequently be used for the control of the driving maneuver, particularly autonomously. By neglecting drivability during the trajectory determination process, the determination of the trajectory can be carried out in a particularly resource-efficient manner. Furthermore, drivability is highly likely to be achieved due to the predefined geometric structures.

According to a further training, it is planned that a limit point is determined up to which the trajectory is drivable, and a connecting trajectory is determined by repeating the steps described above, with the limit point forming the starting position for the connecting trajectory.

In other words, the previously determined trajectory is not completely discarded if its traversability is not fully guaranteed. On the contrary, the plan is to traverse the trajectory up to the boundary point. Subsequently, from the boundary point, the connecting trajectory is determined in the same way as the previous trajectory. This reduces the computation time required to calculate the entire trajectory, which comprises the trajectory up to the boundary point and the connecting trajectory, because the trajectory is at least partially reused. A complete recalculation is therefore unnecessary.

According to a further development, it is provided that the vehicle's direction of travel for the connecting trajectory is reversed compared to the previous trajectory. In other words, it is advantageously provided that the vehicle changes direction at the boundary point. For example, the vehicle travels backward (forward) on the trajectory. In this case, the connecting trajectory can then be traveled forward (backward). This allows for the initiation of a shunting maneuver. This improves the vehicle's agility on the trajectory and the connecting trajectory.

A second aspect of the invention relates to a control unit for determining a trajectory for steering a motor vehicle during a driving maneuver in an area surrounding the motor vehicle, comprising a computing unit which is designed to perform the inventive method for determining a trajectory.

The control unit may additionally include an input section that enables it to receive an image and/or a digital map of the surrounding area. For example, the input section may have an interface to a sensor device, such as a camera system, radar system, or lidar system, of the vehicle.

A third aspect of the invention relates to a driver assistance system for controlling a motor vehicle during a driving maneuver in the vicinity of the motor vehicle, comprising the aforementioned control unit. The driver assistance system may additionally include the aforementioned sensor device. Furthermore, the driver assistance system may optionally include a further control unit for controlling the movement of the motor vehicle. This further control unit may, for example, be configured to control the steering, brakes, and/or a power unit of the motor vehicle. The power unit may, for example, be an internal combustion engine or an electric motor.

The invention also includes a motor vehicle with the aforementioned driver assistance system. The motor vehicle may comprise the aforementioned engine. For example, the motor vehicle may be a car, in particular a passenger car or a truck. Depending on the type of engine, the motor vehicle may be an internal combustion engine vehicle, an electric vehicle, or a hybrid vehicle.

Another aspect of the invention relates to a computer program product with program code means stored in a computer-readable medium for carrying out the inventive method for determining a trajectory when the computer program product is executed on a processor of an electronic control unit. The computer program product according to the invention thus implements the inventive method.

Furthermore, the invention includes a computer-readable medium, in particular in the form of a computer-readable floppy disk, CD, DVD, memory card, USB storage device, or similar, in which program code means are stored to carry out the method for determining a trajectory, when the program code means are loaded into a memory of an electronic control unit and processed on a process of the electronic control unit.

Further features of the invention will become apparent from the claims, the figures, and the description of the figures. The features and combinations of features mentioned above in the description, as well as those subsequently mentioned in the description of the figures and/or shown in the figures alone, can be used not only in the combinations specified but also in other combinations without departing from the scope of the invention. Thus, embodiments that are not explicitly shown and explained in the figures but can be derived and generated from the explained embodiments by separate combinations of features are also to be considered as encompassed and disclosed by the invention. Embodiments and combinations of features are to be considered disclosed even if they do not exhibit all the features of an originally formulated independent claim. Furthermore, embodiments and combinations of features, particularly those described above, are to be considered disclosed if they go beyond or deviate from the combinations of features described in the cross-references of the claims.

• 1 in einer schematischen Vogelperspektive ein Kraftfahrzeug;
• 2 ein beispielhaftes Ablaufdiagramm einer Ausführungsform eines Verfahrens zum Bestimmen einer Trajektorie zum Steuern des Kraftfahrzeugs; sowie
• 3 bis 6 jeweils in einer schematischen Vogelperspektive das Bestimmen einer Trajektorie in einem Umgebungsbereich des Kraftfahrzeugs.

This shows:

• 1 a motor vehicle in a schematic bird's-eye view;
• 2 an exemplary flowchart of an embodiment of a method for determining a trajectory for steering the motor vehicle; and
• 3 until 6 Each diagram shows the determination of a trajectory in a surrounding area of the motor vehicle, presented in a schematic bird's-eye view.

1 Figure 1 shows a motor vehicle 1 equipped with a driver assistance system 4 for autonomously controlling the motor vehicle 1. The driver assistance system 4 enables the control of the motor vehicle during a driving maneuver within a surrounding area U of the motor vehicle 1. Specifically, the driving maneuver is a parking maneuver. For this purpose, the driver assistance system 4 has a control unit 2 for determining a trajectory 5. Additionally, the driver assistance system 4 includes a further control unit 3 for autonomously controlling the driving maneuver, in particular the parking maneuver, according to the trajectory 5. For example, the further control unit 3 is configured to control a steering function 25, a braking function 26, or a motor 27 of the motor vehicle 1. In other words, the further control unit 3 is configured to control driving functions of the motor vehicle 1. To determine the trajectory 5, the control unit 2 can receive a virtual map and/or an image of the surrounding area U from a sensor device of the motor vehicle 1. For example, the sensor setup can include cameras 21 and/or ultrasonic sensors 22.

2 Figure 1 shows an exemplary flowchart of a method for determining the trajectory 5 for controlling the motor vehicle 1. In step S1, a boundary 8 for a possible driving corridor of the motor vehicle 1 is determined in a virtual maneuvering space 16. In step S2, a starting position 11 and an end position 12 for the motor vehicle 1 with respect to the driving maneuver are determined in the virtual maneuvering space 16. In step S3, a predefined geometric structure 9 is positioned in a predetermined relative position with respect to a boundary 8 in the virtual maneuvering space 16. In step S5, a tangent 10 to the geometric structure 9 is determined. In the present embodiment, in step S4, a plurality of tangents 10 are applied to the geometric structure 9, and one is selected from the plurality of tangents 10. Finally, in step S5, a point of tangency 17 of the selected tangent 10 is connected to both the starting position 11 and the end position 12 by a Bézier curve 6, 7. At the point of tangency 17, the respective Bézier curves 6, 7 are both parallel to the corresponding tangent 10. Together, the two Bézier curves 6, 7 form the trajectory 5.

These steps are carried out by the 3 and 4 This is illustrated. In the present example, the driving maneuver is a parking maneuver. The vehicle 1 is parked in a parking space 19. The direction of the arrow, which visualizes the starting position 11 and the end position 12, indicates the orientation of the vehicle 1. Accordingly, this is a reverse parking maneuver. The boundary 8 is located in a corner of the parking space 19. This corner is directly adjacent to the side of the parking space 19, along which the vehicle 11 is steered into the parking space 19.

A circular arc with a predetermined radius is defined as geometric structure 9 around the boundary 8, i.e., the corner of parking space 19. The predetermined radius of the circular arc corresponds to at least the width of the vehicle 1 plus a safety margin. This ensures that the vehicle 1 could theoretically, or with a high degree of probability, drive around the boundary 8 along geometric structure 9. This results in a trajectory 5 that is actually passable by the vehicle 1, with a high degree of probability. As will be explained below, the passability is verified in a final step. Several tangents 10 are then determined for geometric structure 9. One of the tangents 10, or rather its foot 17, is selected as the support point for the trajectory 5. More on this below.

Another geometric structure 13 is arranged in a predetermined relative position with respect to the end position 12. In this case, the other geometric structure 13 is a straight line. Several support points 14 are arranged on the other geometric structure 13, analogous to the tangents 10. The support points 14 additionally specify the course of the geometric structure 13 at the corresponding support point 14. Of these support points 14, only one is selected to determine the trajectory 5.

A first Bézier curve 6 connects the point of tangency 17 and the starting point 11. A second Bézier curve 7 connects the selected support point 14 and the point of tangency 17. The trajectory 5 is provided by these two Bézier curves 6 and 7. Selecting one of the tangents 10 and/or one of the support points 14 can be achieved, for example, by determining a second Bézier curve 7 and a first Bézier curve 6 for each possible combination of tangents 10 and points of tangency 17. In this example, there are four potential tangents 10 and three potential support points 14. Therefore, in this example, it is necessary to determine four different first Bézier curves 6 for each of the potential tangents 10. Similarly, it is necessary to determine twelve different second Bézier curves 7 for the various possible combinations at potential tangents 10 and support points 14. Since both the first Bézier curve 6 and the second Bézier curve 7 are parallel to the selected tangential curve 10 at the point of tangency 17, further alignment of the two Bézier curves 6 and 7 is unnecessary. Finally, the most suitable Bézier curve 6 and 7 can be selected from the possible candidates. Suitability can be verified, for example, using predetermined criteria. These criteria could include a uniform curvature and/or a large distance from boundaries 8. In this way, the trajectory 5 can be determined.

Optionally, several candidates for trajectory 5 can be determined, with the geometric structure 9 being arranged in a different predefined relative position with respect to the boundary 8 in the virtual maneuvering space 16 for each candidate. For example, the circular arc, which in this example forms the geometric structure 9, is arranged around the boundary 8, i.e., the corner of parking space 19, at different radii. Subsequently, several trajectories 5 can be determined with the radius of the circular arc as a parameter. From these, the most suitable trajectory 5 can then be selected according to the aforementioned criteria.

The trajectory 5 is then checked for its drivability. In particular, it is checked whether the vehicle 1 can travel along trajectory 5 without collision and whether a maximum steering angle of the vehicle 1 is exceeded. In the example of 5 At limit point 15, the maximum steering angle of the motor vehicle 1 is exceeded. Therefore, trajectory 5 is only traversable up to limit point 15.

In 6 It is determined that trajectory 5 is only traversable without collision up to boundary point 15. If motor vehicle 1 were to follow trajectory 5 beyond boundary point 15, a collision with a boundary of parking space 19 would result.

To save further computing power, trajectory 5 is used in the examples from 5 and 6 not completely discarded. Instead, a subsequent trajectory is determined with boundary point 15 as its starting position. In other words, the subsequent trajectory 18 joins trajectory 5 at boundary point 15. The subsequent trajectory 18 can be determined using the same steps (S1 to S5) as trajectory 5. In the example according to 5 When transitioning to connecting trajectory 18, motor vehicle 1 maintains its direction of travel as it did in trajectory 5. In the example according to 6 The connecting trajectory 18 is travelled in the opposite direction compared to trajectory 5. Thus, the example according to 6 for a shunting maneuver.

By using the support points 14 and the tangents 10 or the point of tangency 17 to calculate trajectory 5 and Bézier curves 6 and 7, the required computation time can be reduced. Similarly, when trying out different possibilities for the relative position of the geometric structure 9 and/or different trajectories 10 and/or support points 14, the number of different possibilities can be reduced to a comparatively small number. Furthermore, checking the drivability of trajectory 5 can be omitted during its calculation, as the geometric structure 9 ensures a high probability of drivability. Should a final check of drivability after determining trajectory 5 reveal that it is only partially drivable, a connecting trajectory 18, which joins trajectory 5 at the boundary point 15, can be determined with minimal computational effort.

Claims (15)

Method for determining a trajectory (5) for steering a motor vehicle (1) during a driving maneuver in an area (U) surrounding the motor vehicle (1), comprising the steps: - Determining a boundary (8) for a possible - Determine the driving corridor of the motor vehicle (1) in a virtual maneuvering space (16), - Determine a starting position (11) and an end position (12) for the motor vehicle (1) with respect to the driving maneuver in the virtual maneuvering space (16), - Arrange a predefined geometric structure (9) in a predetermined relative position with respect to the boundary (8) in the virtual maneuvering space (16), - Determine a tangent (10) for the geometric structure (9), - Connect a point of tangency (17) of the tangent (10) with both the starting position (11) and the end position (12) with a respective Bézier curve (6, 7), wherein the respective Bézier curves (6, 7) at the point of tangency (17) are both parallel to the tangent (10) and the respective Bézier curves (6, 7) together form the trajectory (5). Procedure according to Claim 1 , characterized in that , for determining the tangent (10), several potential tangents (10) are applied to the geometric structure (9) and one of the potential tangents (10) is selected as the tangent (10). Method according to one of the preceding claims, characterized in that the driving maneuver is a parking maneuver and a corner of a parking space (19) is defined as the boundary (8). Method according to one of the preceding claims, characterized in that a circular arc with a predetermined radius is arranged around the boundary (8) as the geometric structure (9). Method according to one of the preceding claims, characterized in that - a further predetermined geometric structure (13) is arranged in a predetermined relative position with respect to the end position (12) in the virtual maneuvering space (16), - a support point (14) for this further structure (13) is determined, and - the respective Bézier curve (7) from the end position to the point of contact (17) of the tangent (10) of the geometric structure (9) is determined such that the corresponding Bézier curve (7) at the support point (14) of the further geometric structure (13) runs parallel to the further geometric structure (13). Method according to one of the preceding claims, characterized in that - a further predetermined geometric structure (13) is arranged in a predetermined relative position with respect to the starting position (11) in the virtual maneuvering space (16), - a support point for this further geometric structure is determined, and - the respective Bezier curve (6) is determined from the starting position to the point of contact of the tangent (10) of the geometric structure (9) of the boundary such that the corresponding Bézier curve (6) runs parallel to the further geometric structure at the support point (14). Procedure according to Claim 6 , characterized in that - a steering angle of the motor vehicle (1) is determined, and - a circular arc whose curvature is derived from the steering angle is arranged as the further geometric structure (13) for the starting position (11) in the virtual maneuvering space (16). Procedure according to one of the Claims 5 until 7 , characterized in that a respective straight line is arranged as the further geometric structure (13) for the starting position (11) and/or the end position (12) in the virtual maneuvering space (16). Method according to one of the preceding claims, characterized in that the trajectory (5) is checked for its drivability, in particular with regard to a maximum steering angle of the motor vehicle (1) or for its freedom from collision, only after it has been determined. Procedure according to Claim 9 , characterized in that - a limit point (15) is determined up to which the trajectory (5) is traversable, and - a connecting trajectory (18) is determined by repeating the steps of the Patent claim 1 is determined, with the boundary point (15) forming the starting position for the connecting trajectory (18). Procedure according to Claim 10 , characterized in that the direction of travel of the motor vehicle (1) for the connecting trajectory (18) is chosen in the opposite direction to the previous trajectory (5). Control unit (2) for determining a trajectory (5) for controlling a motor vehicle (1) during a driving maneuver in an area (U) surrounding the motor vehicle (1) with a computing unit which is configured to perform a method according to one of the preceding claims. Driver assistance system (4) for controlling a motor vehicle (1) during a driving maneuver in an area (U) surrounding the motor vehicle stuff (1) with a control unit (2) to Claim 12 . Computer program product with program code means stored in a computer-readable medium to perform the method for determining a trajectory (5) according to one of the preceding Claims 1 until 11 to be carried out when the computer program product is executed on a processor of an electronic control unit (2). Computer-readable medium, in particular in the form of a computer-readable floppy disk, CD, DVD, memory card, USB storage device, or similar, in which program code means are stored to carry out the method for determining a trajectory (5) according to any of the preceding Claims 1 until 11 to be carried out when the program code means are loaded into a memory of an electronic control unit (2) and processed on a processor of the electronic control unit (2).