Steer-by-wire steering system and method for operating a steer-by-wire steering system in a motor vehicle with an adjustable steering angle range

Abstract

The present invention relates to a method for operating a steer-by-wire steering system (1) in a motor vehicle, wherein the steer-by-wire steering system (1) comprises a steering handle (2) and a wheel steering actuator (3). For steering the motor vehicle, the steering handle (2) can be moved over an angular range (7, 70) with a starting position (4) in a first and a second direction (5, 6) with a first and a second virtual stop (8, 80; 9, 90), respectively. A steering angle (101) applied to the steering handle (2) is detected and converted by the wheel steering actuator (3) into a wheel steering angle of steerable wheels (18) of the motor vehicle.When the steering handle (2) is moved, a steering angle velocity (102) and a steering angle acceleration (103) are detected, and the initial position (4) is adjusted depending on the detected steering angle velocity (102) and the detected steering angle acceleration (103), whereby this adjustment influences a transmission ratio according to which the steering angle (101) is converted into a wheel steering angle of steerable wheels (18) of the motor vehicle. Furthermore, the invention relates to a steer-by-wire steering system (1) configured to be operated in a motor vehicle according to the aforementioned method, and to a motor vehicle with such a steer-by-wire steering system (1).

Description

The invention relates to a method for operating a steer-by-wire steering system in a motor vehicle, wherein the steer-by-wire steering system comprises a steering handle and a wheel steering actuator, and the steering handle can be moved over an angular range with a starting position in a first direction with a first virtual stop and in a second direction with a second virtual stop. A steering angle input into the steering handle is detected, and the wheel steering actuator converts the detected steering angle into a wheel steering angle of the steerable wheels of the motor vehicle. Furthermore, the invention relates to a steer-by-wire steering system for a motor vehicle, comprising a steering handle and a wheel steering actuator, wherein the steering handle can be moved to steer a motor vehicle over an angular range with a starting position in a first direction with a first virtual stop and in a second direction with a second virtual stop. The invention also relates to a motor vehicle with a steer-by-wire steering system. US Patent 10,906,581 B2 discloses a generic steer-by-wire steering system in which soft stops can be generated as virtual stops during operation of the steering system to alert a driver that a steering movement of a steerable wheel is blocked by an obstacle, such as a curb. To detect such a blockage, steering wheel speed and vehicle speed are used as input signals. The faster the steering wheel is moved, the greater the permissible tolerance range before a blockage of a steerable wheel is suspected. In the generic German patent DE 10 2021 206 791 B3, a steer-by-wire steering system is described, comprising sensors for detecting steering angle or torque, a feedback actuator for providing feedback to the driver, and a steering gear with two electric motors for moving a rack. If one of the electric motors fails or loses power, a software end stop provided via the feedback actuator for the steering mechanism is moved as a virtual stop, so that the steering ratio is maintained and the familiar steering feel is preserved. Furthermore, a steer-by-wire steering system and a method for operating a steer-by-wire steering system are known from DE 10 2024 128 642 A1, wherein it is provided that when a steering stop is reached by a steering handle, in addition to an applied steering angle, an applied steering torque is also recorded as a steering input. Furthermore, DE 10 2014 017 127 A1 discloses a steer-by-wire steering system in which an actuator acting on the steerable wheels is also part of an active vehicle dynamics control system, which can also be controlled by the vehicle dynamics control system independently of steering inputs from a driver. In vehicles with a steer-by-wire steering system, the virtual translation between a movement of the steering handle and the resulting wheel steering angle of the steered wheels can be very direct, especially if the steering wheel or other alternative steering input device has a limited range of motion. Therefore, if a driver of such a vehicle operates the steering handle at high steering speed and / or high steering acceleration, the wheel steering actuator unit responsible for adjusting the wheel steering angle may not be able to follow the steering angle specified by the driver via the steering handle. As a result, the vehicle's reactions may differ from the driver's expectations, which can reduce driving comfort. Against this background, it is an object of the present invention to improve the use of a steer-by-wire steering system in a motor vehicle, in particular in such a way that driving a motor vehicle with a steer-by-wire steering system can be made more comfortable and safer for a driver. To solve this problem, a method for operating a steer-by-wire steering system according to claim 1, as well as a steer-by-wire steering system and a motor vehicle with a steer-by-wire steering system according to the dependent claims, are proposed. Further advantageous embodiments of the invention are described in the dependent claims and the description and are illustrated in the figures. The proposed solution provides a method for operating a steer-by-wire steering system in a motor vehicle, wherein the steer-by-wire steering system comprises a steering handle and a wheel steering actuator, and the steering handle can be moved over an angular range with a starting position for the steering handle, which can in particular be a center position, in a first direction with a first virtual stop and in a second direction with a second virtual stop. In the method, a steering angle input to the steering handle is detected, in particular as a steering input, which is then converted by the wheel steering actuator into a wheel steering angle of the steerable wheels of the motor vehicle.The procedure further stipulates that when the steering handle is moved, a steering angle velocity and a steering angle acceleration are detected; that is, specifically the velocity and acceleration at which the steering handle is moved to input a steering angle. Depending on the detected steering angle velocity and acceleration, the initial position of the steering handle, and thus in particular the steering input, is adjusted. This adjustment of the initial position of the steering handle influences a transmission ratio according to which the steering angle is converted into a wheel steering angle of the vehicle's steerable wheels. The proposed method advantageously provides that the steering angle of a steerable wheel of a motor vehicle does not depend solely on a steering angle set via the steering handle, but includes a variable component. At high steering angle accelerations and high steering speeds, the angle-based component of the steering input is advantageously manipulated to produce a more indirect steering response. This advantageously prevents the wheel steering actuator unit responsible for setting the steering angle from failing to follow the steering angle specified by the driver via the steering handle. By avoiding such situations, the vehicle's handling is advantageously perceived as comfortable by the driver even at such high steering angle accelerations and high steering angle speeds.Since avoiding such situations also prevents the vehicle from behaving unexpectedly for the driver, safety while driving the vehicle is increased. The conversion of the detected steering angle into the wheel steering angle of steerable wheels by means of the wheel steering actuator unit is advantageously carried out according to a virtual transmission ratio, in particular a virtual adjustable transmission ratio, which advantageously specifies into which wheel steering angle a detected steering angle is converted. The virtual transmission ratio can depend in particular on the angular range over which the steering handle is adjustable in both directions. In particular, an advantageous embodiment of the method provides that the transmission ratio with which a steering angle entered into the steering handle is converted into a wheel steering angle of the steered wheels is influenced by adjusting the initial position of the steering handle such that the steering angle is converted into a wheel steering angle that is lower than with the unaffected transmission ratio. This advantageously makes the steering behavior temporarily less direct, and the wheel steering actuator is advantageously able to convert the steering angle into a corresponding wheel steering angle of the steered wheels. In other words, this prevents the steering angle from not being converted into a corresponding wheel steering angle. Specifically, it prevents the steering handle from reaching its limit while the steered wheels have not yet reached their maximum deflection. Furthermore, the angular range within which the steering handle can be adjusted in one direction from its starting position is temporarily increased. Advantageously, the virtual stops are also adjusted accordingly when the starting position is changed. In particular, according to one exemplary embodiment, it can be advantageously provided that at low steering angle speeds and low steering angle accelerations, the end stop of the angle range is reached at 100 degrees. However, if a driver steers more quickly, this exemplary embodiment can advantageously provide that the initial position, and thus the respective end stop, is shifted in the steering direction, so that, due to this shift in the initial position of the steering handle, the end stop is only reached at a steering angle of 110 degrees in this exemplary embodiment. This advantageously makes the steering ratio 10% less indirect in this exemplary embodiment, which advantageously prevents excessive vehicle movements caused by rapid and jerky steering movements by the driver.Advantageously, the end stops for adjustment are designed as software-based stops, particularly as virtual stops. The first and second stops are thus each virtual stops, specifically so-called soft stops, whereby the respective stop for influencing the transmission ratio is advantageously redefined, particularly according to a shift in the initial position of the steering handle. The position of the end stops can thus be easily adjusted, so that the range of motion of the steering handle can be advantageously extended by this adjustment in scenarios with high steering angle speed and / or high steering angle acceleration, thereby making the steering behavior more indirect.This is particularly advantageous if the steering handle is not designed as a conventional steering wheel, but as an alternative steering handle, in particular as a micro wheel, and especially advantageous if the absolute adjustment range up to an end stop is small compared to a conventional steering wheel, in particular if the total angular range between the two virtual stops is between 270° and 100°. According to a further advantageous embodiment, an adapted steering angle is determined based on the detected steering angle, depending on the detected steering angle speed and the detected steering angle acceleration, in particular a steering angle reduced compared to the detected steering angle. According to an advantageous embodiment of the method, a signed steering angle offset is determined for adjustment, in particular for adjusting the initial position and / or for adjusting the angle range and / or for adjusting the detected steering angle, based on the detected steering angle, the detected steering angle velocity and / or the detected steering angle acceleration. The steering angle offset can have a positive or a negative sign. In particular, a current initial position is adjusted by an absolute value of this steering angle offset depending on the direction of movement of the steering handle, whereby, advantageously, a reduced wheel steering angle of the steered wheels is requested based on the resulting adjustment of the transmission ratio.Advantageously, the angular range in which the steering handle can be moved is temporarily increased by adding this steering angle offset, in particular by shifting the initial position of the steering handle and, consequently, the virtual stops accordingly, especially in accordance with the signed steering angle offset. Particularly when the steering handle is a microwheel, which may be located in the area of ​​the center console, the resetting of the initial position of the steering handle is advantageously imperceptible. Furthermore, a virtual transmission ratio of the steer-by-wire steering system is temporarily increased so that a steering angle applied by a vehicle user to the steering handle, especially to the microwheel, is translated into a smaller wheel steering angle due to the adjustment with the steering angle offset than would be the case without such an adjustment. Advantageously, the initial position is shifted by the amount of the steering angle offset in the direction of adjustment corresponding to the steering direction of the detected steering angle. In particular, the steering angle offset shifts the initial position to the right or left, depending on its sign, advantageously making the steering response temporarily less direct. Due to this shift, the initial position can change during use, and in particular, the initial position at the end of vehicle use may differ from the initial position at the beginning. According to a further advantageous embodiment, the first virtual stop and the second virtual stop are shifted in the adjustment direction corresponding to the steering direction of the detected steering angle, in particular by the amount of the steering angle offset. Advantageously, the first virtual stop and the second virtual stop are shifted together with the initial position for the steering handle in the adjustment direction corresponding to the steering direction of the detected steering angle, in particular by the amount of the steering angle offset. Advantageously, the shifting of the stops temporarily increases the angular range for adjusting the steering handle, thus making the steering response more indirect. In particular, this further increases driving comfort for the vehicle user. It is further advantageous that a low steering angle velocity range and a high steering angle velocity range, as well as a low steering angle acceleration range and a high steering angle acceleration range, are specified. The steering angle offset is advantageously set to a value of zero when the detected steering angle velocity is in the low steering angle velocity range and the detected steering angle acceleration is in the low steering angle acceleration range. As a special embodiment, it can be provided that the low steering angle acceleration range and / or the low steering angle velocity range are defined by an interval [0], and thus, in this special case, the high steering angle acceleration range and / or the high steering angle velocity range begin directly. If the detected steering angle velocity is in the high steering angle velocity range and / or the detected steering angle acceleration is in the high steering angle acceleration range, the steering angle offset is advantageously set with an absolute value greater than zero.By providing different steering angle acceleration ranges and steering angle speed ranges, it is advantageously ensured that, during normal steering movements with low steering angle speed and low steering angle acceleration, a detected steering angle is not manipulated, and that a detected steering angle is converted into a steering angle of the steered wheels, particularly according to defined conditions, by means of the wheel steering actuator unit, and in particular always in the same way, whereby - as is known in the prior art - the virtual transmission ratio can be adjusted depending on the vehicle speed of the motor vehicle. If the steering angle offset is set to zero, particularly when the steering angle velocity and steering angle acceleration are low, i.e., when the steering angle velocity is in the low steering angle velocity range and the steering angle acceleration is in the low steering angle acceleration range, the gear ratio is advantageously set as a predefined standard gear ratio, which, however, can be variable depending on the current vehicle speed.During normal steering movements performed by a driver, the steering handle can advantageously be moved from a starting position through a defined angular range in a first direction up to the first virtual stop, and through a defined angular range in a second direction up to the second virtual stop. The steering angle set via the steering handle is advantageously converted into a wheel steering angle of the steered wheels according to a standard transmission ratio. Advantageously, a steering resistance torque is generated when the first virtual stop and when the second virtual stop are reached. This steering resistance torque advantageously prevents further adjustment of the steering handle beyond the defined angular range and thus beyond the first or second virtual stop, respectively. Another advantageous embodiment provides that the transmission ratio is influenced in such a way that a steering angle is converted into a reduced wheel steering angle, and / or that the angle range is increased when the steering angle offset is set with an absolute value greater than zero. The transmission ratio is thus advantageously adjusted so that a steering angle is converted into a reduced wheel steering angle, and / or that the angle range is increased when the steering angle offset is set with an absolute value greater than zero. Advantageously, this makes the steering response less direct and advantageously prevents the wheel steering actuator from failing to follow the steering angle specified by the driver via the steering handle. Advantageously, the transmission ratio is further influenced in such a way that the steering angle is converted into a smaller wheel steering angle the larger the absolute value with which the steering angle offset is set. Advantageously, this makes the handling of a motor vehicle safer because it prevents jerky steering movements, especially with alternative steering systems with small adjustment ranges, particularly a micro-wheel, from leading to large steering angles of the steered wheels. Furthermore, the angular range over which the steering handle can be moved to adjust the steering angle is advantageously increased the larger the absolute value with which the steering angle offset is set. Advantageously, the starting position of the steering handle is varied accordingly. Increasing the angular range advantageously makes the steering response less direct. According to an advantageous embodiment of the method, an absolute value of the detected steering angular velocity and an absolute value of the detected steering angular acceleration are determined. Advantageously, a first angular offset is assigned to the determined absolute value of the detected steering angular velocity. Advantageously, a second angular offset is assigned to the determined absolute value of the detected steering angular acceleration. The value for the steering angle offset is then advantageously calculated taking into account the first angular offset and the second angular offset, in particular from the sum of the first angular offset and the second angular offset. Advantageously, this method of determining the steering angle offset ensures that a steering angle offset greater than zero can also be determined solely by a high absolute value of the detected steering angular acceleration or by a high absolute value of the detected steering angular velocity.This advantageously further increases the safety when operating the steer-by-wire steering system in a motor vehicle. A further advantageous embodiment of the method provides that, after an adjustment of the detected steering angle, a further adjustment of the detected steering angle is performed with a delay, and, more advantageously, is not performed abruptly. This advantageously ensures that the steering behavior does not change suddenly and unexpectedly for a driver of a motor vehicle, particularly when briefly steering from one direction to the opposite direction. This further enhances the safety of operating the steer-by-wire steering system in a motor vehicle. The delayed adjustment can be achieved, in particular, by using a delay element. The steer-by-wire steering system for a motor vehicle proposed to solve the aforementioned problem comprises a steering handle and a wheel steering actuator. The steering handle is designed to steer a motor vehicle over an angular range with a starting position in a first direction with a first virtual stop, in particular up to a first defined soft stop, and in a second direction with a second virtual stop, in particular up to a second defined soft stop. Furthermore, the steer-by-wire steering system is advantageously designed to be operated in a motor vehicle according to a method developed according to the invention, wherein the aforementioned features of the method can be implemented, in particular, individually or in combination. In particular, the steer-by-wire steering system is designed to detect a steering angle input into the steering handle during operation in a motor vehicle, specifically to detect it as a steering input. The wheel steering actuator unit of the steer-by-wire steering system is also specifically designed to translate the detected steering angle, and in particular the detected steering input, into a wheel steering angle of the steerable wheels of the motor vehicle.Furthermore, the steer-by-wire steering system operated in a motor vehicle is advantageously designed to detect the steering angle velocity and acceleration of the steering handle when the handle is moved, and to adjust the detected steering angle and the initial position of the steering handle depending on the detected steering angle velocity and acceleration, and in particular to influence the transmission ratio according to which the steering angle is converted into a wheel steering angle of the steerable wheels of the motor vehicle. The proposed steer-by-wire steering system thus advantageously realizes the benefits associated with the description of the method proposed according to the invention.The proposed steer-by-wire steering system is in particular a steer-by-wire steering system of a motor vehicle, wherein a steer-by-wire steering system of a motor vehicle is in particular a motor vehicle steer-by-wire steering system. According to an advantageous embodiment of the steer-by-wire steering system, the steering handle is designed as an alternative steering handle, in particular as a microwheel. In particular, an advantageous embodiment of the steer-by-wire steering system provides that the steering handle of the steer-by-wire steering system is not designed as a conventional steering wheel. The motor vehicle proposed to solve the aforementioned problem further comprises a steer-by-wire steering system designed according to the invention. In particular, the motor vehicle is a two-track motor vehicle, and more specifically a passenger car (PKW: passenger vehicle). Further advantageous details, features, and design details of the invention are explained in more detail in connection with the exemplary embodiments illustrated in the figures (hereinafter referred to as Fig.: figure). Fig. 1 shows, in a simplified perspective view, an exemplary embodiment of a steer-by-wire steering system designed according to the invention; Fig. 2a, b shows, in a simplified schematic view, an exemplary adjustment of an initial position of the steering handle and, consequently, of the angular range over which the steering handle of the steer-by-wire steering system according to Fig. 1 can be adjusted, wherein the adjustment of the initial position is carried out within the framework of a method designed according to the invention; Fig. 3 shows a block diagram to illustrate the adjustments according to an exemplary embodiment of a method designed according to the invention; and Fig.4 A block diagram representation to illustrate a determination of a steering angle offset according to an embodiment of a method designed according to the invention. In the various figures, identical parts are usually marked with the same reference symbols and are therefore sometimes only explained in connection with one of the figures. Figure 1 shows a simplified embodiment of a steer-by-wire steering system 1 for a motor vehicle according to the invention. In this embodiment, the steer-by-wire steering system 1 comprises a steering handle 2 designed as a microwheel, by means of which a vehicle user can steer the vehicle. The steering handle 2, which is shown in an enlarged view in Figures 2a and 2b, can be arranged, in particular, in the area of ​​the center console of a motor vehicle. In this embodiment, the steering handle 2 of the steer-by-wire steering system 1 is designed to move, with the steerable wheels unsteered, from a starting position 4, as shown by way of example in Fig. 2a, over an angular range 7 in a first direction 5 to a first virtual stop 8 and in a second direction 6 to a second virtual stop 9. In this embodiment, the virtual stops 8, 9 are designed as soft stops and are provided by a feedback actuator 12 acting on the steering handle 2 by means of a correspondingly high steering resistance torque. However, according to an alternative embodiment, it is also possible to store the virtual stops 8, 9 in a control unit 13 assigned to the steer-by-wire steering system 1 solely for the purpose of operating the system, without the vehicle operator receiving a steering stop signal.Since this makes operation less intuitive for the vehicle user, such a design is particularly suitable when manual steering with this steering handle is rather the exception, especially because the vehicle drives predominantly autonomously, or when the steering handle is a backup for a main steering handle that may be stowed away in an autonomous driving mode. In the embodiment described with reference to Fig. 1, Fig. 2a, and Fig. 2b, a suitable steering resistance torque is generated at each of the virtual stops 8 and 9, preventing the steering handle 2 from moving beyond the respective stop 8 or 9. The angular range 7 and thus the adjustment path of the steering handle 2 between the first virtual stop 8 and the second virtual stop 9 is 100° in this embodiment, and thus, starting with an adjustment movement of the steering handle 2, in particular from the initial position 4 of the steering handle 2, 50° in the direction of the first stop 8 and 50° in the direction of the second stop 9. A control unit 13 of the steer-by-wire steering system 1 is configured to detect an adjustment movement performed by a vehicle user via the steering handle 2, wherein several steering parameters are associated with the adjustment movement, which are detected by sensors and transmitted to the control unit 13. In this exemplary embodiment, the detected steering parameters include, in particular, a steering angle 101 set via the steering handle 2, a steering angle velocity 102, which indicates the speed at which a steering angle 101 is set, and a steering angle acceleration 103, which indicates the acceleration with which a steering angle 101 is set. In this embodiment, a signal line 14 to a wheel steering actuator 3 of the steer-by-wire steering system 1 is provided to convert the detected steering angle 101, taking into account the detected steering angle velocity 102 and the detected steering angle acceleration 103, into a wheel steering angle of steerable wheels 18. The wheel steering actuator 3 is configured to convert a received steering input via a steering gear 17 into a wheel steering angle of steerable wheels 18 of the motor vehicle. In this embodiment, the wheel steering actuator 3 includes an electric motor 31. The electric motor 31 acts via a transmission belt 32 on a spindle drive 16, which is operatively connected to a connecting rod 15 designed as a rack. By appropriately controlling the electric motor 31, the spindle drive 16 is driven to convert a steering input into a steering movement of the steerable wheels 8.The wheel steering actuator 3 acts on the connecting rod 15 via the spindle drive 16, which is driven by the electric motor 31, thus initiating a steering movement of the steerable wheels 18 of the motor vehicle. In this embodiment, the steerable wheels 18 are connected to the connecting rod 15 in a known manner via tie rods 19. The tie rods 19 themselves are connected to each steered wheel 18 via steering knuckles in a known manner. In this embodiment, the steer-by-wire steering system 1 is designed to detect a steering angle 101 introduced into the steering handle 2 for the purpose of determining a steering input when operating in a motor vehicle, and to use the wheel steering actuator unit 3 to set a wheel steering angle of steerable wheels 18 of the motor vehicle according to a given transmission ratio, starting from the detected steering angle 101 and taking into account the further detected steering angle velocity 102 and steering angle acceleration 103.The steer-by-wire steering system 1 is further developed, in particular by using the control unit 13, to adjust the initial position 4 of the steering handle 2 depending on the detected steering angle velocity 102 and the detected steering angle acceleration 103, and thus a transmission ratio according to which the steering input applied to the steering handle 2, in particular the steering angle 101, is converted into a wheel steering angle of the steerable wheels 18 of the motor vehicle. The angular range 7 over which the steering handle 2 can be adjusted is also temporarily increased in this configuration. It is intended that, in the event of a high detected steering angle velocity 102 and / or a high detected steering angle acceleration 103, the initial position 4 of the steering handle 2 is shifted in the steering direction 109 and, accordingly, the virtual stops 8, 9 are moved. An example of this is shown in Fig. 2a, which illustrates a newly defined initial position 4' and newly defined virtual stops 80, 90.This means that in the case of fast and / or jerky steering movements, where there is a particular risk that the wheel steering actuator 3 might not be able to implement this steering movement according to a standard setting, the initial position 4 and the virtual stops 8, 9 in the steering direction 109 are shifted, and thereby the angle range 7 in the steering direction 109 is temporarily increased to a larger angle range 70 and the virtual transmission ratio, according to which the steering angle 101 is converted into a wheel steering angle of the steered wheels 18, is increased accordingly, so that the steering behavior of the motor vehicle becomes more indirect. In this embodiment, a signed steering angle offset 110 is determined based on the detected steering angle 101, the detected steering angle velocity 102, and the detected steering angle acceleration 103. The initial position 4 and the virtual stops 8 and 9 are shifted by this offset. The sign of the steering angle offset 110 depends on the steering direction 109. Specifically, the steering angle offset 110 has a negative sign for a steering movement 109 to the left, as shown in Fig. 2a, and a positive sign for a steering movement 109 to the right, as shown in Fig. 2b. In the exemplary case where the steering angle offset 110 is 5°, the shift of the second virtual stop 9 would temporarily result in an angle range 70 that is 5° larger for the current steering operation. Since the angle range from the original starting position 4 to the newly defined second virtual stop 9 is now 55° instead of 50° in the steering direction 109, the transmission ratio is also adjusted, and the detected steering angle 101 is converted into a correspondingly smaller wheel steering angle of the steered wheels 18. For a new steering maneuver starting from a straight-ahead driving position, the new initial position 4' and the angle range 7' apply, which, as at the beginning, again totals 100° in this embodiment, i.e., 50° each way from the initial position 4'. Advantageously, this change remains unnoticed by the vehicle operator. In Fig. 2b a corresponding adjustment of the initial position 4 and the virtual stops 8, 9 for a steering direction 109 to the right is sketched. An advantageous method for determining the steering angle offset 110 is explained below, also with reference to Fig. 4. With reference to Figures 3 and 4, an embodiment of a method for operating a steer-by-wire steering system in a motor vehicle, in particular a steer-by-wire steering system 1 as described with reference to Figures 1 and 2, is explained in more detail. The steer-by-wire steering system 1 comprises a steering handle 2 and a wheel steering actuator 3, wherein, for steering the motor vehicle, the steering handle 2 can be moved from a starting position 4 over an angular range 7 in a first direction 5 up to a first virtual stop 8 and in a second direction 6 up to a second virtual stop 9. A steering resistance torque is generated at each of the virtual stops 8, 9, in particular by using an electric motor. In the method, a steering angle 101 introduced into the steering handle 2 is detected.In addition, when the steering handle 2 is moved, a steering angle velocity 102 and a steering angle acceleration 103 are recorded, whereby the recorded steering angle 101 is adjusted depending on the level of the recorded steering angle velocity 102 and the recorded steering angle acceleration 103. In the embodiment shown in Fig. 3, a steering angle offset 110 is determined from the detected steering angle velocity 102 and the detected steering angle acceleration 103 using a first processing unit 105, which is in particular comprised of a control unit of the steer-by-wire steering system, especially the control unit 13 of the steer-by-wire steering system 1. The detected steering angle 101 is then adjusted by adding the steering angle offset 110 using a signal processing unit 106. In this embodiment, the signal processing unit 106 is configured as an adder with a positive input (+) and a negative input (-), wherein the detected steering angle 101 is applied to the positive input (+) and the steering angle offset 110 to the negative input (-).The resulting adjusted steering angle 111 is transmitted to a second computing unit 107 and to a third computing unit 108. The second processing unit 107 determines, taking into account a virtual transmission ratio 104, which describes the ratio of steering angle to the wheel steering angle to be converted, a request signal S3 for the wheel steering actuator unit 3 to set a wheel steering angle resulting from the steering angle 111, taking into account the transmission ratio 104. The transmission ratio 104 is also influenced by the adaptation of the detected steering angle 101 to the steering angle 111 and is correspondingly larger. Taking into account the adjusted steering angle 111, the third processing unit 108 shifts the initial position 4 of the steering handle 2 and the virtual stops 8, 9, as shown by way of example in Fig. 2a and Fig. 2b, so that initial position 4 becomes a new initial position 4', the first virtual stop 8 becomes a new first virtual stop 80, and the second virtual stop 9 becomes a new virtual stop 90. In doing so, the third processing unit 108 generates a signal S12 for a feedback actuator of the steer-by-wire steering system, in particular for the feedback actuator 12 of the steer-by-wire steering system 1, which now generates a steering resistance torque at the newly determined positions to realize the virtual stops 80, 90. Fig. 4 shows further details for determining the steering angle offset 110 according to an advantageous embodiment. It is provided that a low steering angle velocity range 112 and a high steering angle velocity range 122, as well as a low steering angle acceleration range 113 and a high steering angle acceleration range 123, are predefined. In the embodiment shown in Fig. 4, this predefinition is performed for the steering angle velocity ranges 112, 122 in the signal processing block 155 and for the steering angle acceleration ranges 113, 123 in the signal processing block 156. The steering angle offset 110 is set to a value of zero (steering angle offset = 0°) according to these predefinitions when the detected steering angle velocity 102 is in the low steering angle velocity range 112 and the detected steering angle acceleration 103 is in the low steering angle acceleration range 113.If, on the other hand, the detected steering angle velocity 102 is in the high steering angle velocity range 122 or the detected steering angle acceleration 103 is in the high steering angle acceleration range 123 or if both the steering angle velocity 102 and the steering angle acceleration 103 are in the high ranges 122, 123, then the steering angle offset 110 is set with a value greater than zero. If the steering angle offset 110 is set to zero (steering angle offset = 0°), which is the case when the steering angle velocity 102 and steering angle acceleration 103 are low when moving the steering handle 2, then the initial position 4, the detected steering angle 101, and the virtual stops 8, 9 remain unchanged. A predefined standard gear ratio is set as the transmission ratio 104, which, however, may be dependent on the vehicle speed. If the steering angle offset 110 changes from a steering angle offset of 0° to a value greater than zero, which occurs at high steering angle speed 102 and / or high steering angle acceleration 103, the transmission ratio 104 is adjusted such that a detected steering angle 101 is converted into a reduced wheel steering angle, and the angle range 7 is adjusted to a larger angle range 70 by adjusting the virtual stops 8, 9 and the initial position 4. Specifically, the transmission ratio 104 is adjusted such that the larger the value of the steering angle offset 110, the smaller the wheel steering angle that is converted into a detected steering angle 101.Furthermore, in this embodiment, it is particularly true that the angle range 7 is increased the larger the value with which the steering angle offset 110 is set. Specifically, in the embodiment shown in Fig. 4, an absolute value 132 of the detected steering angular velocity 102 and an absolute value 133 of the detected steering angular acceleration 103 are determined. For this purpose, the steering angular velocity 102 is fed to a signal processing block 151 to determine an absolute value of the detected steering angular velocity, and the steering angular acceleration 103 is fed to a signal processing block 152 to determine an absolute value of the detected steering angular acceleration. In parallel, the steering angular velocity 102 and the steering angular acceleration 103 are each fed to a further signal processing block 153, 154, in which a sign of the detected steering angular velocity 102 and the detected steering angular acceleration, respectively, is determined, in particular depending on the steering direction 109. The determined absolute value 132 of the detected steering angle velocity 102 is then assigned a first angular offset 142' in the signal processing block 155, and the determined absolute value 133 of the detected steering angle acceleration 103 is assigned a second angular offset 143' in the signal processing block 156. This assignment is advantageously carried out using corresponding lookup tables. In particular, it is provided that for absolute values ​​132 of the steering angle velocity 102 in the low steering angle velocity range 112, a first angular offset 142' with the value zero is set, and for absolute values ​​133 of the steering angle acceleration 103 in the low steering angle acceleration range 113, a second angular offset 143' with the value zero is set.If, on the other hand, the absolute values ​​132, 133 lie in the high steering angle velocity range 122 or the high steering angle acceleration range 123, respectively, correspondingly increasing angle offsets 142', 143' are set as the values ​​increase, in particular as illustrated by the curves in signal processing blocks 155, 156. In signal processing blocks 157, 158, the sign for the first angle offset 142' and the second angle offset 143' is then adjusted according to the results from signal processing blocks 153, 154. This results in the sign-adjusted first angle offset 142 and the sign-adjusted second angle offset 143, which are added together in signal processing block 159 to form a preliminary steering angle offset 110'. Furthermore, this embodiment includes an integrator acting as a delay element 161 and another signal processing block 160 for summation. The steering angle offset 110', which depends on the steering angle velocity and acceleration, is integrated, and the resulting value is added to the determined steering angle offset 110'. This maintains the steering angle offset 110, thus delaying any further adjustment of the steering angle offset 110. The steering angle offset 110 is then used, as already described, to influence the gear ratio 104. The embodiments shown in the figures and explained in connection with them serve to illustrate the invention and are not limiting to it. Reference symbol list 1 Steer-by-wire steering system 12 Feedback actuator 13 Control unit 14 Signal line 15 Connecting rod 16 Spindle drive 17 Steering gear 18 Steerable wheel 19 Tie rod 2 Steering handle 3 Wheel steering actuator unit 31 Electric motor of the wheel steering actuator unit (3) 32 Transmission belt 4 Initial position 4' Adjusted initial position 5 First adjustment direction of steering handle (2) 6 Second adjustment direction of steering handle (2) 7 Angle range 70 (Adjusted) angle range 8 First virtual stop 80 (Adjusted) first stop 9 Second virtual stop 90 (Adjusted) second stop 101 Steering angle 102 Steering angle speed 103 Steering angle acceleration 104 Gear ratio 105 First processing unit 106 Signal processing unit 107 Second processing unit 108 Third processing unit 109 Steering direction 110 Steering angle offset 111 (adjusted) steering angle 112 low steering angle speed range 113 low steering angle acceleration range 122 high steering angle speed range123 High steering angle acceleration range 132 Absolute value of the detected steering angle velocity 133 Absolute value of the detected steering angle acceleration 142' First angle offset (without adjusted sign) 143' Second angle offset (without adjusted sign) 142 First angle offset (with adjusted sign) 143 Second angle offset (with adjusted sign) 151 Signal processing block for determining an absolute value of the detected steering angle velocity 152 Signal processing block for determining an absolute value of the detected steering angle acceleration 153 Signal processing block for determining a sign of the detected steering angle velocity 154 Signal processing block for determining a sign of the detected steering angle acceleration 155 Signal processing block for assigning a first angle offset 156 Signal processing block for assigning a second angle offset 157 Signal processing block for adjusting the sign of the firstAngle offsets 158 Signal processing block for adjusting the sign of the second angle offset 159 Signal processing block for adding the first angle offset (142) and the second angle offset (143) 160 Signal processing block for adding 161 Delay element S3 Request signal to the wheel steering actuator unit (3) S12 Signal to the feedback actuator (12)

Claims

Method for operating a steer-by-wire steering system (1) in a motor vehicle, wherein the steer-by-wire steering system (1) comprises a steering handle (2) and a wheel steering actuator (3), wherein, for steering the motor vehicle, the steering handle (2) can be moved over an angular range (7, 70) with a starting position (4) in a first direction (5) with a first virtual stop (8, 80) and in a second direction (6) with a second virtual stop (9, 90), wherein a steering angle (101) applied to the steering handle (2) is detected, and the wheel steering actuator (3) converts the detected steering angle into a wheel steering angle of steerable wheels (18) of the motor vehicle, characterized in that, when the steering handle (2) is moved, a steering angle velocity (102) and a steering angle acceleration (103) are detected.and depending on the detected steering angle velocity (102) and the detected steering angle acceleration (103), the initial position (4) for the steering handle (2) is adjusted, whereby this adjustment of the initial position (4) influences a transmission ratio (104) according to which the steering angle (101) is converted into a wheel steering angle of steerable wheels (18) of the motor vehicle. Method according to claim 1, characterized in that the transmission ratio (104) is influenced by the adjustment in such a way that the steering angle (101) is converted into a wheel steering angle that is reduced compared to the unaffected transmission ratio. Method according to claim 1 or claim 2, characterized in that the angular range (7) is temporarily increased by the adjustment. Method according to one of the preceding claims, characterized in that, based on the detected steering angle (101), an adapted steering angle (111) is determined depending on the detected steering angle velocity (102) and the detected steering angle acceleration (103). Method according to one of the preceding claims, characterized in that a signed steering angle offset (110) is determined for the adjustment based on the detected steering angle (101), the detected steering angle velocity (102) and the detected steering angle acceleration (103). Method according to claim 5, characterized in that the initial position (4) is shifted by the amount of the steering angle offset (110) by the adjustment direction (5, 6) corresponding to the steering direction of the detected steering angle (101). Method according to claim 5 or claim 6, characterized in that the first virtual stop (8, 80) and the second virtual stop (9, 90) are moved in the adjustment direction (5, 6) corresponding to the steering direction of the detected steering angle (101) by the amount of the steering angle offset (110). A method according to any one of claims 5 to 7, characterized in that a low steering angle speed range (112) and a high steering angle speed range (122) as well as a low steering angle acceleration range (113) and a high steering angle acceleration range (123) are specified, wherein the steering angle offset (110) is set to a value of zero when the detected steering angle speed (102) is in the low steering angle speed range (112) and the detected steering angle acceleration (103) is in the low steering angle acceleration range (113), and the steering angle offset (110) is set to an absolute value greater than zero when the detected steering angle speed (102) is in the high steering angle speed range (122) and / or the detected steering angle acceleration (103) is in the high steering angle acceleration range (123). Method according to one of claims 5 to 8, characterized in that the transmission ratio (104) is further influenced in such a way that a detected steering angle (101) is converted into a smaller wheel steering angle the larger the absolute value with which the steering angle offset (110) is set. Method according to one of the preceding claims insofar as it relates back to claim 3 and claim 5, characterized in that the angle range (7) is increased the greater the absolute value with which the steering angle offset (110) is set. Method according to one of the preceding claims insofar as related to claim 5, characterized in that an absolute value (132) of the detected steering angle velocity and an absolute value (133) of the detected steering angle acceleration are determined, a first angular offset (142) is assigned to the determined absolute value (132) of the detected steering angle velocity and a second angular offset (143) is assigned to the determined absolute value (133) of the detected steering angle acceleration, wherein the value for the steering angle offset (110) is formed from the sum of the first angular offset (142) and the second angular offset (143). Method according to one of the preceding claims, characterized in that after a determination of the steering angle offset (110) a further adjustment of the steering angle offset (110) is carried out with a delay. Method according to one of the preceding claims, characterized in that a steering resistance torque is generated when the first virtual stop (8, 80) is reached and when the second virtual stop (9, 90) is reached. Steer-by-wire steering system (1) for a motor vehicle, wherein the steer-by-wire steering system (1) comprises a steering handle (2) and a wheel steering actuator (3), wherein the steering handle (2) can be moved to steer a motor vehicle over an angular range (7, 70) with an initial position (4) in a first direction (5) with a first virtual stop (8, 80) and in a second direction (6) with a second virtual stop (9, 90), characterized in that the steer-by-wire steering system (1) is designed to be operated in a motor vehicle according to one of the preceding claims. Steer-by-wire steering system (1) according to claim 14, characterized in that the steering handle (2) is a micro wheel. Motor vehicle with a steer-by-wire steering system (1) according to claim 14 or claim 15 .

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