Method for operating a rear axle steering system of a vehicle and a vehicle

Abstract

The invention relates to a method for operating a rear axle steering system (10) of a vehicle (12), in particular a motor vehicle, with features of claim 1 and a vehicle, in particular a motor vehicle, with features of the dependent claim.

Description

The invention relates to a method for operating a rear axle steering system of a vehicle and to a vehicle with a rear axle steering system. A vehicle's rear-axle steering system is an electric steering system that translates steering movements at the rear axle. If the rear-axle steering system becomes blocked, for example by snow or ice, the function is usually deactivated, along with a corresponding driver warning. DE 10 2023 205 296 B3 discloses a method for operating a steer-by-wire steering system of a vehicle, DE 10 2018 124 244 A1 discloses a method for operating a rear-axle steering system of a two-track vehicle, DE 10 2017 206 701 A1 discloses a method for controlling a rear-wheel steering system, DE 10 2021 213 389 A1 discloses a method for controlling a steering system for a motor vehicle, and DE 10 2020 215 018 B3 discloses a method for operating a superimposed steering system of a motor vehicle. A disadvantage of this is that deactivating the rear-axle steering function can cause the vehicle to veer unintentionally. If the veer becomes too steep, the driver may be warned by a red warning light. The driver will then be instructed to stop the vehicle, potentially resulting in a breakdown. The vehicle may then need to be towed. It is therefore an object of the present invention to provide a method for operating a rear axle steering system of a vehicle and a vehicle, whereby the above disadvantages are eliminated. The above problem is solved by a method for operating the rear axle steering of a vehicle, in particular a motor vehicle, with the features of claim 1. The method comprises the steps: - Requesting the rear axle steering. - Adjusting the rear axle steering to a center position when a blockage of the rear axle steering is detected. If a blockage of the rear axle steering, caused by snow or ice, for example, is detected, the rear axle steering is adjusted or moved towards the center position. This prevents the rear axle steering from being deactivated. The risk of the vehicle becoming stranded can be avoided or at least reduced. This allows for increased availability of the rear axle steering in a blockage situation using simple means. Furthermore, the risk of the vehicle becoming unstable can be avoided or at least reduced. In this context, the term "center position" for the rear axle steering refers to a position in which the deflection of the rear axle steering, or the rear wheels of the vehicle, is 0°. In the center position of the rear axle steering, the rear wheels of the vehicle (or their respective axes of rotation) are aligned parallel to the longitudinal axis of the vehicle. In this context, a "broken-down vehicle" refers to a vehicle that, for example, due to a breakdown or technical defect, can no longer continue driving and is left stranded or lying on the side of the road. Rear-axle steering, in this context, refers to a vehicle steering system in which the vehicle's rear wheels actively or passively rotate at a specific angle to the vehicle's longitudinal axis – either in the same direction as the front wheels or in the opposite direction. This can improve the vehicle's driving stability, maneuverability, and comfort. In this context, requesting rear-axle steering refers to activating the rear-axle steering system. Specifically, a signal can be sent to the rear-axle steering system to switch it on or activate it. Requesting or activating rear-axle steering can also refer to adjusting or rotating the vehicle's rear wheels relative to its longitudinal axis. This can be achieved, for example, by initiating a steering movement of the front-axle steering system or by adjusting / rotating the vehicle's front wheels relative to its longitudinal axis. According to a further development of the procedure, a warning message can be issued if a blockage of the rear axle steering is detected. The warning message can be displayed while the rear axle steering is being adjusted to the center position. The warning message can be displayed, for example, in the cockpit or on the vehicle's on-board computer. This allows the driver of the vehicle to be informed or warned of a blockage of the rear axle steering using simple means. According to a further development of the procedure, the warning message can be a yellow warning message. A yellow warning message, in this context, refers to a notification, for example, in the vehicle's cockpit or on-board computer, indicating that something is not functioning optimally, but that there is no immediate emergency (red warning message). The vehicle can usually continue its journey with a yellow warning message. In particular, a yellow warning message does not require immediate action, unlike a red warning message (e.g., engine overheating, brake failure, oil pressure loss). With a red warning message, the journey should be stopped as soon as possible. This allows an early warning to be provided to the driver of the vehicle using simple means. According to a further development of the procedure, adjusting the rear axle steering to the center position can be implemented with a constant and predetermined adjustment speed. This allows for a safe adjustment of the rear axle steering to the center position, which is as imperceptible as possible for the driver, using simple means. According to a further development of the method, the adjustment speed can be predetermined such that the rear axle steering is moved to the center position within 3 seconds. In particular, the adjustment time (i.e., the time in which the rear axle steering is moved to the center position) can be a maximum of 3 seconds. This allows for safe and controllable adjustment of the rear axle steering at all times. According to a further development of the procedure, the rear axle steering can be released again if the rear axle steering is adjusted to the center position and the request for rear axle steering has been cancelled. This is particularly the case when the rear wheels and the front wheels of the vehicle are aligned parallel to the longitudinal axis (i.e., the vehicle is (again) being steered or driving straight ahead). In this context, "releasing the rear axle steering" means resuming the proper functioning of the rear axle steering. This allows the rear axle steering function to be restored using simple means. According to a further development of the procedure, the warning message can be cleared when the rear axle steering is enabled. In particular, the yellow warning message can be cleared when the rear axle steering is enabled. This allows the driver to be informed about the enabled rear axle steering using simple means. According to a further development of the procedure, rear-axle steering can be requested by front-axle steering. In other words, rear-axle steering can be requested by adjusting or rotating the vehicle's front wheels relative to the vehicle's longitudinal axis (e.g., by turning the steering wheel). This allows the requirement for rear axle steering to be implemented using simple means. According to a further development of the procedure, the actual position of the rear axle steering can be monitored. If the actual position deviates from a target position, a blockage of the rear axle steering can be detected. In this context, the actual position of the rear axle steering refers to the current position of the vehicle's rear wheels relative to the vehicle's longitudinal axis. The desired (requested) position of the rear axle steering refers to the desired position of the vehicle's rear wheels relative to the vehicle's longitudinal axis. This allows for the detection of a rear axle steering blockage using simple means. The above problem is solved by a vehicle, in particular a motor vehicle, with a rear-axle steering system having the features of the dependent claim. The vehicle includes a control unit. The control unit is configured to control the rear-axle steering system. The control unit is configured to perform a method for operating the rear-axle steering system as described above. Regarding the advantages achievable with the vehicle, reference is made to the relevant explanations concerning the procedure. The measures described in connection with the procedure and / or those explained below can be used for further vehicle development. Naturally, the features mentioned above and / or below can be used not only in the combination specified, but also in any combination with each other or individually. Further features, details and advantages of the invention will become apparent from the wording of the claims and from the following description of exemplary embodiments with reference to the drawings. Figure 1 shows, schematically, a diagram illustrating a method for operating a rear-axle steering system, and Figure 2 shows a vehicle with a rear-axle steering system. In the following description and in the figures, corresponding components and elements bear the same reference symbols. For clarity, not all reference symbols are shown in every figure. Fig. 1 schematically shows a diagram 24 illustrating a method for operating a rear axle steering system 10 of a vehicle 12, in particular a motor vehicle. In this diagram, the Y-axis of diagram 24 represents an adjustment position 26 in arbitrary units. The adjustment position 26 can, in particular, be specified as a steering angle (e.g., in degrees) with respect to a longitudinal axis 28 of the vehicle 12 (see Fig. 2). In this diagram, the X-axis of diagram 24 represents a time 30 in arbitrary units. The time 30 can, in particular, be specified in seconds. The procedure for operating the rear axle steering 10 of the vehicle 12 comprises the following steps: - Requesting the rear axle steering 10. - Adjusting the rear axle steering 10 to a center position 14 if a blockage of the rear axle steering 10 is detected. The rear axle steering 10 can be requested by a front axle steering 16 (see Fig. 2). If a blockage of the rear axle steering 10 is detected, a warning message can be issued. The warning message can be a yellow warning message. The actual position 18 of the rear axle steering 10 can be monitored. A blockage of the rear axle steering 10 can be detected if the actual position 18 deviates from a target position 20. The target position 20 of the rear axle steering 10 is shown in diagram 24 by means of a dashed line. The actual position 18 is shown in diagram 24 by means of a solid line. In this case, the actual position 18 deviates from the target position 20. This is indicated in Fig. 1 by a double arrow. Due to the deviation of the actual position 18 from the target position 20, a blockage of the rear axle steering 10 is detected at a first time point 32. Normally, the rear axle steering 10 would now be deactivated and, if necessary, a red warning message would be issued. This is indicated in diagram 24 by a dotted line running parallel to the x-axis. According to the procedure for operating the rear axle steering 10 of the vehicle 12, instead of deactivating the rear axle steering 10, the rear axle steering 10 is adjusted to the center position 14. In this case, the middle position 14 is reached at a second time point 34. Adjusting the rear axle steering 10 to the center position 14 can be implemented with a constant and predetermined adjustment speed. The adjustment speed can be preset such that the rear axle steering 10 is adjusted to the center position 14 within 3 seconds. This can result in a maximum adjustment time 36. The adjustment time 36 can be calculated as the difference between the second time point 34 and the first time point 32 (adjustment time 36 = second time point 34 - first time point 32). The rear axle steering 10 can be released again when the rear axle steering 10 is adjusted to the center position 14 and the request for the rear axle steering 10 has been cancelled. In this case, the center position 14 is reached at the second time point 34. The rear axle steering 10 remains in the center position 14. At a third time point 38, the requirement for the rear axle steering 10 is released. This can occur, for example, when the vehicle 12 is driving straight ahead again or when the front axle steering 16 is aligned parallel to the longitudinal axis 28 of the vehicle 12. After the rear axle steering 10 is released, the warning message, in particular the yellow warning message, can be cleared. This is the case here at or after the third point in time 38. Fig. 2 schematically shows a vehicle 12 with rear axle steering 10. A top view of the vehicle 12 is shown. The vehicle 12 can be any vehicle 12, in particular a motor vehicle, as described above. The vehicle 12 includes a control unit 22. The control unit 22 is configured to control the rear axle steering 10. The control unit 22 is configured to perform a method for operating the rear axle steering 10 as described above. This method may, in particular, be the method shown in Fig. 1. In the present case, the rear axle steering 10 comprises two rear wheels 40. The vehicle 12 in the present case comprises a front axle steering 16, which comprises two front wheels 42. The front axle steering system 16 can set a front axle steering angle 44 at the front wheels 42. This can be achieved, for example, by means of a steering movement (e.g., by turning the steering wheel of the vehicle 12). The front axle steering system 16 can transmit the front axle steering angle 44 to the control unit 22. The front axle steering angle 44 can refer to an angle between the longitudinal axis 28 or a parallel 46 to the longitudinal axis 28 and a running axis 48 of the front wheels 42 (or of the respective front wheel 42). The control unit 22 can receive the front axle steering angle 44 and calculate a target position 20 for the rear axle steering 10. The control unit 22 can send the target position 20 to the rear axle steering 10. The rear axle steering 10 can receive the target position 20 and adjust the rear wheels 40 accordingly. The adjustment of the rear wheels 40 is indicated in Fig. 2 by means of the dotted rear wheels 40. If a deviation of the actual position 18 from the target position 20 is detected (e.g., through an internal check), a blockage of the rear axle steering 10 is assumed. The rear axle steering 10 then adjusts to the center position 14 at the adjustment speed (see Fig. 1). The rear wheels 40 in the center position 14 are shown in Fig. 2 by means of solid lines. In the center position 14, the running axes 48 of the rear wheels 40 are each aligned parallel to the longitudinal direction 28 or to a parallel 46 to the longitudinal axis 28. In the center position 14, the rear axle steering angle 50 can be zero (0°). The rear axle steering angle 50 can refer to an angle between the longitudinal axis 28 or a parallel 46 to the longitudinal axis 28 and a running axis 48 of the rear wheels 40 (or of the respective rear wheel 40). In the present case, a running axis 48 of a rear wheel 40 or of a front wheel 42 is meant to be an axis oriented perpendicular to a rotation axis 52 of the rear wheel 40 or of the front wheel 42. After or when a blockage of the rear axle steering 10 is detected, a (especially yellow) warning lamp request can be sent to the control unit 22. The rear axle steering 10 can remain in the center position 14 until the value of the (requested) target position 20 reaches zero (0°). This is the case when the front wheels 42 are (again) aligned parallel to the longitudinal axis 28, i.e., until the front axle steering angle 44 is zero (0°). Once both the front axle steering angle (44) and the rear axle steering angle (50) are zero (0°), the rear axle steering (10) can be reactivated. The (yellow) warning light request can then be canceled. The availability of the rear axle steering (10) can thus be restored. All axis and / or angle specifications or relations refer to a top view of the vehicle 12, as shown in Fig. 2.

Claims

Method for operating a rear axle steering system (10) of a vehicle (12), in particular a motor vehicle, comprising the steps: - Requesting the rear axle steering system (10); - Adjusting the rear axle steering system (10) to a center position (14) when a blockage of the rear axle steering system (10) is detected due to external conditions, in particular snow or ice. Method according to claim 1, characterized in that a warning message is issued when a blockage of the rear axle steering (10) is detected. Method according to claim 2, characterized in that the warning message is a yellow warning message. Method according to one of the preceding claims, characterized in that the adjustment of the rear axle steering (10) to the center position (14) is implemented with a constant and predetermined adjustment speed. Method according to claim 4, characterized in that the adjustment speed is predetermined such that the rear axle steering (10) is adjusted to the center position (14) within 3 s. Method according to one of the preceding claims, characterized in that the rear axle steering (10) is released again when the rear axle steering (10) is adjusted to the center position (14) and the request for the rear axle steering (10) has been cancelled. Method according to claim 6 and 2 or 3, characterized in that the warning message, in particular the yellow warning message, is cancelled when the rear axle steering (10) is released. Method according to one of the preceding claims, characterized in that the request for the rear axle steering (10) is made by a front axle steering (16). Method according to one of the preceding claims, characterized in that an actual position (18) of the rear axle steering (10) is monitored and a blockage of the rear axle steering (10) is detected if the actual position (18) deviates from a target position (20). Vehicle (12), in particular motor vehicle, with a rear axle steering system (10), comprising a control device (22) for controlling the rear axle steering system (10), wherein the control device (22) is configured to perform a method for operating the rear axle steering system (10) according to one of the preceding claims.

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