Method for operating a driver assistance system for a motor vehicle

Abstract

Method for operating a driver assistance system (3) for a motor vehicle (1), wherein the driver assistance system (3) is configured to learn at least one driving trajectory in a learning mode (10) and to follow the at least one learned driving trajectory in a following mode (20), wherein in the learning mode (10) a limit steering wheel angle (15) is specified which is smaller than a maximum adjustable steering wheel angle (23) of a steering system (4) of the motor vehicle (1), characterized in that in the learning mode (10) and in the following mode (20) steering wheel angles (22) are adjustable up to the maximum adjustable steering wheel angle (23) and when the specified limit steering wheel angle (15) is reached a haptic warning message (16) is issued on the steering wheel (5) (S4).

Description

The invention relates to a method for operating a driver assistance system for a motor vehicle according to the preamble of claim 1.A motor vehicle may have a driver assistance system which is designed to learn at least one driving trajectory in a learning mode and to follow the at least one learned driving trajectory in a follow-up mode. Such a driver assistance system is, for example, a trained parking assistant for parking the motor vehicle in a parking area or a reversing assistant which can reverse a manually carried out forward drive at least partially automatically. In the following mode, the motor vehicle is operated fully automatically or at least partially automatically.Deviations between the learned driving trajectory and the followed driving trajectory should be kept as small as possible, in order to avoid collisions with obstacles in the surroundings of the motor vehicle, for example. However, a steering system of a motor vehicle can be designed as a front axle steering system. If this is the case, the motor vehicle travels with its front wheels along a different path during a reverse travel than during a forward travel, although the travel trajectories considered at a center of a rear axle of the motor vehicle coincide for the forward travel and the reverse travel, if appropriate. Due to this deviation of the paths, the front wheels may possibly collide with lateral obstacles during a reverse travel. In addition, a reverse travel may not be possible along the same travel trajectories as the forward travel if a steering wheel angle is turned at which the front axle steering system reaches a mechanical end stop of the steering system, for example. If, for example, a driver of the motor vehicle in the learning mode therefore drives at least for a route with a maximally adjustable steering wheel angle of a steering wheel of the motor vehicle, it is not possible in the follow-up mode to provide enough steering angle on this route to follow the learned driving trajectory precisely. The situation may then even occur in which the driver assistance system switches off automatically.DE 10 2020 211 260 A1 discloses a method of the generic type for operating a motor vehicle in which a maximally adjustable steering wheel angle is limited in a learning mode of the motor vehicle, wherein this steering wheel angle limitation can be variably defined depending on a driving situation.DE 10 2014 220 144 A1 discloses a likewise generic method for assisting a driver of a vehicle, in which a steering wheel angle of the vehicle that can be adjusted to the maximum by the driver is limited in a learning phase, such that the steering wheel angle can only have angle values that are smaller than a predefined steering wheel angle limit value. In an execution phase in which the trajectory learned in the learning phase is followed, the maximum possible steering wheel angle of the vehicle is not limited.Furthermore, DE 10 2017 200 215 A1 shows a reversing assistant and a method for determining a reversing trajectory for a driver assistance system.The absolute limitation of the maximally adjustable steering wheel angle described in the two first-mentioned publications can be perceived by the driver of the motor vehicle as greatly restricting him and consequently as disadvantageous. It is therefore expedient to prevent driving with the maximally adjustable steering wheel angle in an alternative manner in the teaching mode.It is the object of the invention to provide a solution by means of which an adjustment of a maximally adjustable steering wheel angle in a learning mode of a driver assistance system can be reliably counteracted.The object is achieved by the subject matters of the independent claims. Advantageous further developments are evident from the dependent claims.A first aspect of the invention relates to a method for operating a driver assistance system for a motor vehicle. The driver assistance system is designed to learn at least one driving trajectory in a learning mode, which can alternatively be referred to as a learning phase. This travel trajectory leads from a starting position to a target position spatially remote therefrom. The travel trajectory can describe, for example, a forward travel and / or a reverse travel of the motor vehicle between the starting position and the end position. The driver assistance system is also designed to follow the at least one learned driving trajectory in a follow-up mode, which can alternatively be referred to as an execution phase. This follow-up is performed at least partially automatically, in particular fully automatically. The driver assistance system is therefore designed to actuate a longitudinal and / or transverse guidance of the motor vehicle. The driver assistance system is, for example, a trained parking assistant and / or a reversing assistant. Alternative or additional driver assistance systems, which are designed to travel along a taught travel trajectory, are possible.In the learning mode, a limit steering wheel angle is predefined which is smaller than a maximally adjustable steering wheel angle of a steering wheel of the motor vehicle. When the predefined limit steering wheel angle is reached, a haptic notification is output on the steering wheel. The haptic notification is output by means of the steering wheel. It is therefore provided that a driver of the motor vehicle is informed by means of the haptic notification on the steering wheel that the limit steering wheel angle has been reached. This is intended to make it clear to the driver that, at a steering wheel angle which is at least as large as the limit steering wheel angle, a range of steering wheel angles is reached which is so large that, if appropriate, the following of the travel trajectory followed by the driver is not possible in the following mode. Therefore, steering wheel angles from the limit steering wheel angle should be avoided.Unlike in the prior art, only the haptic notification is output without then presetting an absolute limitation of the maximally adjustable steering wheel angle. It is thus possible for the driver to nevertheless set a steering wheel angle greater than the limit steering wheel angle, but the haptic notification has shown him, before he can do this, that such actuation of the steering of the motor vehicle may possibly impair the functionality of the driver assistance system. As a result, a steering wheel angle limiting function is implemented in a manner that is easily comprehensible to the driver, by means of which a steering wheel angle reserve is created, which in this case comprises the steering wheel angles between the limit steering wheel angle and the maximally adjustable steering wheel angle. The driver is haptically informed that he has now reached this steering wheel angle margin, so that he can, for example, avoid any further steering of the steering wheel as soon as he has registered the haptic notification. The haptic notification is particularly suitable here, since the driver always touches or encompasses the steering wheel during the setting of a steering wheel angle. The driver therefore always perceives the haptic notification during the steering of the motor vehicle and understands it more intuitively than, for example, a notification output optically and / or acoustically. This method according to the invention is therefore intuitively detectable and therefore comfortable for the driver. This reliably counteracts the setting of a maximally adjustable steering wheel angle in the learning mode of the driver assistance system.According to the invention, it is provided that in the learning mode and in the follow-up mode, steering wheel angles are adjustable up to the maximum adjustable steering wheel angle. The limit steering wheel angle thus does not provide an actual limitation of the possible steering wheel angles of the steering wheel, so that all steering wheel angles up to the maximally adjustable steering wheel angles can always be adjusted. If the driver wishes to set a steering wheel angle greater than the limit steering wheel angle, for example, since otherwise the target position cannot be reached, he can move over the haptic notification, in particular without artificially restricting the available range of steering wheel angles to him. This can be perceived by the driver as less threatening and therefore advantageous.One embodiment provides that when the limit steering wheel angle is reached, a counter-steering torque is built up as the haptic information message, which counter-steering torque counteracts a driver hand torque applied to the steering wheel. The counter steering torque is experienced by the driver as a resistance to the steering wheel movement performed by the driver. This resistance is thus detected haptically by the driver. In order to set a steering wheel angle greater than the limit steering wheel angle, the driver now has to apply more force, that is to say increase the driver hand torque exerted by him. The driver hand torque is a torque applied to the steering wheel by at least one hand of the driver when the driver rotates the steering wheel. However, it is preferably provided that the counter-steering torque can be overcome, so that it is entirely possible with a previously increased driver hand torque to achieve a steering wheel angle between the limit steering wheel angle and the maximally adjustable steering wheel angle. The driver is reliably haptically perceptiblely informed by the counter-steering torque that has been built up.In addition, a further embodiment provides that the counter-steering torque is built up only over a steering wheel angle range which is built up from the limit steering wheel angle to a further limit steering wheel angle which is greater than the limit steering wheel angle and less than the maximally adjustable steering wheel angle. The steering wheel angle range thus extends from the described limit steering wheel angle, at which the haptic notification is output, to the further limit steering wheel angle, but not to the maximally adjustable steering wheel angle. In particular, the counter-steering torque is increased within the steering wheel angle range from an initial counter-steering torque to a final counter-steering torque deviating therefrom. The counter-steering torque increases between the counter-steering wheel angle and the further counter-steering wheel angle. A value range is thus provided in which the counter-steering torque increases continuously, for example, until it has reached the final counter-steering torque. As soon as the final steering counter torque is reached, the driver must act on the steering wheel with a particularly large manual driver torque in order to achieve an increase in the steering wheel angle. Subsequently, one end of the built-up counter-steering torque can be provided, so that when the further limit steering wheel angle is exceeded, the counter-steering torque is reduced continuously or in a step-like manner, in particular in a single step. This has the effect that greater steering wheel angles than the further limit steering wheel angle up to the maximally adjustable steering wheel angle can be achieved without counter-steering torque or with a counter-steering torque which is smaller than the final counter-steering torque. A type of click frog effect thus takes place, which resembles a kickdown effect of an accelerator pedal in an automatic vehicle as a motor vehicle. This realizes a particularly clear haptic notification.The limit steering wheel angle can alternatively be referred to as the first limit steering wheel angle and the further limit steering wheel angle as the second limit steering wheel angle. Furthermore, an additional further limit steering wheel angle can be provided, which can be referred to as a third limit steering wheel angle. Between the further limit steering wheel angle (second limit steering wheel angle) and the additional further limit steering wheel angle (third limit steering wheel angle), the counter-steering torque can decrease, for example, from the final counter-steering torque up to a lower counter-steering torque, which is, for example, greater than, less than or equal to the initial counter-steering torque.A further exemplary embodiment provides that when the limit steering wheel angle is reached, a steering wheel vibration takes place as the haptic information. For this purpose, for example, a vibration element which is arranged in the steering wheel is activated, by means of which the steering wheel is set in vibration. The steering wheel is therefore set into vibration or oscillation, wherein the vibration or oscillation of the steering wheel only occurs when the driver has already rotated the steering wheel to such an extent that the current steering wheel angle is equal to or greater than the limit steering wheel angle. The steering wheel vibration is generated, for example, by means of an up and down swelling, sign-changing steering assistance torque which is applied to the steering wheel. The steering wheel vibration can be designed with a design and strength similar or the same as in a lane departure warning system, i.e. for example in a lane keeping assistant as a driver assistance system.The steering wheel vibration can, for example, continue until the maximum adjustable steering wheel angle is reached, that is to say can take place at all steering wheel angles between the limit steering wheel angle and the maximum adjustable steering wheel angle. Alternatively or additionally, a further limit steering wheel angle can be provided, wherein the steering wheel vibration takes place only in the steering wheel angle range between the limit steering wheel angle and the further limit steering wheel angle. The further steering wheel angle can be the same as the previously described further or second steering wheel angle. Steering wheel vibration is a reliable way of haptically alerting the driver that larger steering wheel angles are critical.In an embodiment which is not claimed, it is provided that, when the limit steering wheel angle is reached, a counter-steering torque is built up which counteracts a driver hand torque built up on the steering wheel in such a way that setting of steering wheel angles between the limit steering wheel angle and the maximum settable limit steering wheel angle is prevented. It is thus entirely possible that before reaching a mechanical end stop of the steering wheel, which is expected at 100 percent of the maximum possible steering angle, an artificial end stop is generated, which is reached at 95 percent of the maximum possible steering angle, for example. There, the counter-steering torque, which can also be referred to as electromechanical counter-steering torque, is built up, which counteracts the driver hand torque. Here, the steering counter torque completely counteracts the driver hand torque. As a result, a fictitious upstream end stop for the learning mode is generated. This is preferably not generated in the follow-up mode. This steering wheel angle reserve comprises, for example, 5 percent steering wheel angle, so that this 5 percent steering wheel angle cannot be set by the driver, regardless of which driver hand torque acts on the steering wheel. This ensures that the driver cannot press over the fictitious end stop at all.It is provided here that the counter-steering torque always completely counteracts the driver hand torque, that is to say that these two torques are of equal magnitude. This is a particularly powerful measure which acts on the steering system, but which is likewise detected haptically by the driver. The counter-steering torque and the suppression of the steering wheel angles between the limit steering wheel angle and the maximum adjustable limit steering wheel angle can be understood as an alternative or further haptic indication.A further embodiment comprises that the teaching mode is manually activatable. The limiting steering wheel angle is therefore specified only when the teaching mode is actually desired by the driver. For this purpose, an actuating element or operating element can be provided in the motor vehicle, such as a switch, a button, a rotary push switch and / or a button. Alternatively or additionally, the teaching mode can be activated by means of a voice control and thus by detecting a voice command by means of a microphone in the motor vehicle. Alternatively or additionally, the learning mode can be activated by means of a mobile terminal which is positioned in the motor vehicle and / or is assigned to the driver of the motor vehicle. This ensures that the haptic notification message is not always output by the steering wheel, but only in situations in which the driver explicitly desires this. This is particularly comfortable for the driver, since he is not restricted or impaired with respect to the steering wheel angle during other journeys which are not intended to be journeys in the learning mode.According to an additional specific embodiment, it is provided that a check is made as to whether the motor vehicle is in a driving situation in which a driving speed of the motor vehicle is lower than a driving speed limit value. Alternatively or additionally, it is checked whether it is in a driving situation in which a steering behavior of the driver is in a steering behavior range which is assigned to the learning mode of the driver assistance system. Only if this is the case, that is to say if the driving speed is less than the driving speed limit value and / or the steering behavior is in the steering behavior range, the learning mode is automatically activated in the motor vehicle. There can therefore be a driver assistance system with background training, in which the learning mode is activated automatically in specific situations, i.e. depending on the driving situation. The travel speed limit value is, for example, 30 kilometers per hour, 20 kilometers per hour or, in particular, 10 kilometers per hour. At travel speeds between greater than 0 kilometers per hour and less than the travel speed limit value, the travel situation can be recognized as being present. The driving situation is thus in a low-speed range. The steering behavior range is reached if the motor vehicle is steered multiple times in different directions within a predefined time window, wherein steering wheel angles of, for example, 90 percent and more of the maximally adjustable steering wheel angle are input in this case. This corresponds, for example, to a journey with a plurality of tight curves. The learning mode can therefore always be activated independently when the motor vehicle is driving in very narrow and changing curves in the low-speed range, in particular over a predefined minimum travel distance. This is because this indicates that, in the near future, for example, the driver assistance system, such as the trained parking assistant or the reversing assistant, could activate. The learning mode can therefore be activated preventively. This is particularly advantageous in the case of a reversing assistant in which the driver, for example at the beginning of his journey, was not yet clear that he is likely to require the reversing assistant.For the learning mode automatically activated depending on the driving situation, the first two described measures are particularly suitable, i.e. the haptic notification in the form of the counter-steering torque, which is built up up up to the further limit steering wheel angle, and / or in the form of the steering wheel vibration. The third described measure, in which the complete counteraction of the driver hand torque takes place, can furthermore be provided, wherein this is preferably predefined only when the teaching mode is activated manually. Additionally or alternatively, the first two described measures are suitable for manual activation.An additional embodiment includes that automatically activating the teaching mode is deactivatable by manually operating an operating element. Here, the same operating element or a different operating element can be operated as the operating element described above in the manual activation of the teaching mode. The actuating element can alternatively be referred to as an operating element.The described restriction of the teaching mode by outputting the haptic notification can consequently be deactivated. It can be provided, for example, in an operating menu in the motor vehicle that there is provided the option that the driver can select the haptic notification message that may interfere with him in the learning mode. This is particularly useful in order to avoid the driver nevertheless being disturbed in an undesired manner by the haptic notification and being nervous, for example. This ensures that the method described is perceived particularly comfortably.Depending on the current travel speed of the motor vehicle, it may be provided that, for example, in a first travel speed range up to a first travel speed limit value, the steering wheel vibration takes place as a haptic information message and only at relatively high travel speeds of the motor vehicle is the build-up of the counter-steering torque which is built up over the steering angle range, or vice versa. Alternatively or additionally, the haptic notification message may depend on a scenario or location. It can then be dependent, for example, on a road type and / or a traffic density. It can be provided that only in the manually activated learning mode is the setting of steering wheel angles between the limit steering wheel angle and the maximally settable steering wheel angle prevented as a haptic notification. The respective haptic notification message can be set manually by the driver in the motor vehicle and thus be predefined.For use cases or application situations which can arise in the method and which are not explicitly described here, provision can be made for an error message and / or a request for inputting a user feedback to be output and / or for a default setting and / or a predetermined initial state to be set according to the method.A further aspect of the invention relates to a motor vehicle. The motor vehicle is designed to carry out the method described above. The motor vehicle according to the invention is preferably designed as a motor vehicle, in particular as a passenger car or truck, or as a passenger bus or motorcycle.The motor vehicle may have a control device. The control device performs the described method. The control device is at least designed to actuate the steering system and thus a steering system of the motor vehicle.The invention also includes the control device for the motor vehicle. The control device can have a data processing device or a processor device which is configured to carry out an embodiment of the method according to the invention. For this purpose, the processor device can have at least one microprocessor and / or at least one microcontroller and / or at least one FPGA (field programmable gate array) and / or at least one DSP (digital signal processor). Furthermore, the processor device can have program code which is configured to carry out the embodiment of the method according to the invention when executed by the processor device. The program code can be stored in a data memory of the processor device. The processor device can be based on at least one circuit board and / or on at least one SoC (system on chip), for example.The invention also includes developments of the motor vehicle according to the invention, which have features as have already been described in connection with the developments of the method according to the invention.As a further solution, the invention comprises a computer-readable storage medium comprising program code which, when executed by a computer or a computer cluster, causes the latter to execute an embodiment of the method according to the invention. The storage medium may be provided at least partially as a non-volatile data memory (e.g. as a flash memory and / or as an SSD-solid state drive) and / or at least partially as a volatile data memory (e.g. as a RAM-random access memory). The storage medium can be arranged in the computer or computer network. However, the storage medium can also be operated, for example, as a so-called store server and / or cloud server on the Internet. The computer or computer network can provide a processor circuit with, for example, at least one microprocessor. The program code can be provided as binary code and / or as assembler code and / or as source code of a programming language (e.g. C) and / or as a program script (e.g. Python).The invention also includes the combinations of the features of the described embodiments. The invention therefore also comprises implementations which each have a combination of the features of a plurality of the described embodiments, provided that the embodiments have not been described as mutually exclusive.Exemplary embodiments of the invention are described below. The following shows: FIG. 1 shows a schematic illustration of a motor vehicle; FIG. 2 shows a schematic illustration of a signal flow graph of a method for operating a driver assistance system of a motor vehicle; FIG. 3 shows a schematic illustration of a first measure; FIG. 4 shows a schematic illustration of a second measure; and FIG. 5 shows a schematic illustration of a third measure.The exemplary embodiments explained below are preferred embodiments of the invention. In the exemplary embodiments, the described components of the embodiments each represent individual features of the invention that are to be considered independently of one another and that also develop the invention independently of one another. Therefore, the disclosure is intended to include combinations of the features of the embodiments other than those illustrated. Furthermore, the described embodiments can also be supplemented by further features of the invention that have already been described.In the figures, identical reference numerals designate functionally identical elements.FIG. 1 shows a motor vehicle 1 having a control device 2. The control device 2 is designed to provide and execute a driver assistance system 3. The motor vehicle 1 has a steering system 4, which can comprise a steering wheel 5 and a steering wheel actuator 6. The control device 2 can actuate the steering wheel actuator 6, with the result that the latter, for example, exerts a torque on the steering wheel 5 and / or vibrates the steering wheel 5.Here, a driver 7 steers the motor vehicle 1. The driver assistance system 3 is designed to train a driving trajectory. Driver assistance system 3 is therefore, for example, a trained parking assistant or a reversing assistant.FIG. 2 shows a method for operating the driver assistance system 3. the driver assistance system 3 is designed to learn at least one driving trajectory in a learning mode 10 and to track the at least one learned driving trajectory in a tracking mode 20. The follow-up is at least assisted, partially automatic and preferably fully automatic.The teaching mode 10 can be manually activatable, as can take place in a method step S 1. Alternatively or additionally, the learning mode 10 can be activated automatically in method steps S 2 and S 3. For this purpose, it can first be checked in method step S 2 whether motor vehicle 1 is in a driving situation in which a driving speed 11 of motor vehicle 1 is less than a driving speed limit value 12 and / or a steering behavior 13 of driver 7 is in a steering behavior range 14 which is assigned to learning mode 10 of driver assistance system 3.Only if this is the case is the learning mode 10 automatically activated in method step S 3. The travel speed limit value 12 is, for example, 30 kilometers per hour, 20 kilometers per hour or, in particular, 10 kilometers per hour. At the driving speed 11 between greater than 0 and less than this driving speed limit value 12, the driving situation can be detected. The driving situation is thus in a low-speed range. The steering behavior 13 lies in the steering behavior range 14 when, for example, tight curves and curves changing direction are provided and traversed over a longer distance. A curve is referred to herein as narrow, for example, when it requires a steering wheel angle 22 (see reference sign 22 in FIG. 3 ) of 90 to 100 percent of a maximum adjustable steering wheel angle 23 (see reference sign 23 in FIG. 3 ).It can be provided that the described automatic activation of the teaching mode 10 can be deactivated by manual actuation of an actuating element by the driver 7. Thus, for example, a menu option can be provided in which any automatic activation of the teaching mode 10 is prevented.In the learning mode 10, a limit steering wheel angle 15 is predefined which is smaller than the maximally adjustable steering wheel angle 23 of the steering wheel 5 of the motor vehicle 1. When the predefined limit steering wheel angle 15 is reached, a haptic notification 16 is output on the steering wheel 5 and thus by means of the steering wheel 5. This is effected in a method step S 4. It can be provided that in both the learning mode 10 and the follow-up mode 20, any steering wheel angles 22 up to the maximally adjustable steering wheel angle 23 can be adjusted. The limit steering wheel angle 15 is therefore only the steering wheel angle 22 at which the haptic notification 16 is output, but no actual limitation of the steering wheel angles 22 to a predefined range of steering wheel angles 22. In the follow-up mode 20, no specification of a limit steering wheel angle 15 or no output of the haptic notification 16 takes place.Three different haptic notification messages 16 may be possible, which are referred to below as first measure 17, second measure 18 and third measure 19.FIG. 3 shows the first measure 17. a steering wheel torque 21 is plotted here against the steering wheel angle 22. Three different curves are drawn here, namely a driver hand torque 25, a steering assistance torque 26 and a total steering wheel torque 27, which results from the sum of the driver hand torque 25 and the steering assistance torque 26. Furthermore, the maximally adjustable steering wheel angle 23 and an example of a limit steering wheel angle 15 are shown here. It becomes clear that when the limit steering wheel angle 15 is reached, a counter-steering torque 24 is built up as the haptic information 16, which counter-steering torque at least partially counteracts the driver hand torque 25 applied to the steering wheel 5. The counter-steering torque 24 is encompassed by the steering assist torque 26, which is built up, for example, by means of the steering wheel actuator 6.The counter-steering torque 24 is preferably built up only over a steering wheel angle range 29 which extends from the limit steering wheel angle 15 to a further limit steering wheel angle 28. The further limit steering wheel angle 28 is greater than the limit steering wheel angle 15 and less than the maximally adjustable steering wheel angle 23. the counter-steering torque 24 within this steering wheel angle range 29 preferably increases from an initial counter-steering torque up to a final counter-steering torque deviating therefrom. This is outlined here by the local increase in the steering assist torque 26.It can be provided that after reaching the final counter-steering torque, the counter-steering torque 24 decreases again and thus a so-called pop-up frog effect 30 occurs. A slight resistance is therefore exerted until the further limit steering wheel angle 28 is reached in order to inform the driver 7 that he approaches the maximum adjustable steering wheel angle 23 at an even greater manual driver torque 25 than before, which steering wheel angle should actually be avoided in the learning mode 10. However, as soon as the further limit steering wheel angle 28 is reached, the steering assist torque 26 decreases again here, such that the further steering wheel angles 22 can be adjusted up to the maximally adjustable steering wheel angle 23.FIG. 4 shows the second measure 18. a steering wheel vibration 31 is carried out here when the limit steering wheel angle 15 is reached as haptic information 16. For this purpose, up and down swelling, sign-changing steering assist torques 26 are generated here. This vibration effect informs the driver 7 of the reaching of the limit steering wheel angle 15. However, it can turn the steering wheel 5 further up to the maximally adjustable steering wheel angle 23.FIG. 5 shows the third measure 19, in which in the teaching mode 10 no steering wheel angles 22 are adjustable between the limit steering wheel angle 15 and the maximally adjustable steering wheel angle 23. Namely, when the limit steering wheel angle 15 is reached, a counter steering torque 24 is built up, which counteracts the manual driver torque 25 built up on the steering wheel 5 in such a way that an adjustment of steering wheel angles 22 between the limit steering wheel angle 15 and the maximally adjustable steering wheel angle 23 is completely prevented. The steering assist torque 26 then completely compensates for the driver hand torque 25.Overall, the examples show a method for maintaining a steering wheel angle reserve for driver assistance systems 3 which follow learned trajectories. The steering wheel angle reserve which is created as a result represents a steering wheel angle limiting function for the steering 4, which is conceivable, for example, for any steering-by-wire system. The first two measures 17, 18 are preferably implemented. It is preferably provided that in the case of the automatic activation of the teaching mode 10, only the first measure 17 and the second measure 18 are possible.Depending on the driving speed 11, it may be provided that, for example, the second measure 18 is activated in a first speed range up to a first driving speed limit value 12 and the first measure 17 or vice versa is only activated at relatively high driving speeds 11 of the motor vehicle 1. Alternatively or additionally, the actually carried out measure 17, 18, 19 can depend on a scenario or location. It can then be dependent, for example, on a road type and / or a traffic density. It can be provided that the third measure 19 can be activated only in the manually activated teaching mode 10. The respective measure 17, 18, 19 can be set manually by the driver 7 in the motor vehicle 1 and can thus be predefined.

Claims

Method for operating a driver assistance system (3) for a motor vehicle (1), wherein the driver assistance system (3) is designed to learn at least one driving trajectory in a learning mode (10) and to track the at least one learned driving trajectory in a follow-up mode (20), wherein a limit steering wheel angle (15) which is smaller than a maximum adjustable steering wheel angle (23) of a steering system (4) of the motor vehicle (1) is predefined in the learning mode (10), characterized in that in each case steering wheel angles (22) are adjustable up to the maximum adjustable steering wheel angle (23) in the learning mode (10) and in the follow-up mode (20), and a haptic notification message (16) is output (S4) on the steering wheel (5) when the predefined limit steering wheel angle (15) is reached.Method according to Claim 1, wherein, when the limit steering wheel angle (15) is reached, a counter-steering torque (24) is built up as the haptic information message (16), said counter-steering torque counteracting a driver hand torque (25) applied to the steering wheel (5).Method according to Claim 2, wherein the counter-steering torque (24) is built up only over a steering wheel angle range (29) which extends from the limit steering wheel angle (15) to a further limit steering wheel angle (28) which is greater than the limit steering wheel angle (15) and less than the maximally adjustable steering wheel angle (23), wherein in particular the counter-steering torque (24) increases within the steering wheel angle range (29) from an initial counter-steering torque to a final counter-steering torque which differs therefrom.Method according to Claim 1, wherein, when the limit steering wheel angle (15) is reached as the haptic notification (16), a steering wheel vibration (31) takes place.Method according to one of the preceding claims, wherein the learning mode (10) can be activated manually (S1).Method according to one of the preceding claims, wherein it is checked (S2) whether the motor vehicle (1) is in a driving situation in which a driving speed (11) is less than a driving speed limit value (12) and / or a steering behavior (13) lies in a steering behavior range (14) which is assigned to the learning mode (10) of the driver assistance system (3), wherein the learning mode (10) is automatically activated (S3) only if this is the case.The method of claim 6, wherein automatically activating the teaching mode (10) is deactivatable by manually operating an actuator.Motor vehicle (1) designed to carry out a method according to one of the preceding claims.

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