Method for determining a steering hysteresis demand, steering system and control unit

Abstract

The invention relates to a method for determining a steering hysteresis demand for a steering device of a vehicle, a steering system, a control unit and a computer readable storage medium. The steering device is part of a steering system of the vehicle and is coupled to at least one actuator. The actuator is arranged to apply a steering torque to the steering device. The method comprises at least a step of determining the steering hysteresis demand based on at least one rack force of the steering system. The steering hysteresis demand forms at least a part of a target steering torque which can be applied by the actuator to the steering device, the steering hysteresis demand is characterized by an absolute limit value and an absolute gradient value, both of which are determined taking into account said rack force, wherein at least a first function value is multiplied by a second function value in order to determine the absolute limit value of the steering hysteresis demand and a third function value is multiplied by a fourth function value in order to determine the absolute gradient value of the steering hysteresis demand.

Description

Technical Field

[0001] The present invention relates to a method for determining steering hysteresis demand, a steering system, a control unit, and a computer-readable storage medium. Background Technology

[0002] In the case of electromechanical steering systems or steer-by-wire systems, the mechanical connection between the steering mechanism (steering wheel, lever) and the wheels to be controlled can be eliminated. Although there is no mechanical connection, this type of steering system has actuators that interact with the steering mechanism to provide a natural steering feel to the vehicle user. The target steering torque requirement of the actuator is determined. This is compared with the actual steering torque applied to the steering mechanism, allowing the corresponding manipulation variable for the actuator to be determined via a control loop. Based on the manipulation variable, the actuator acts on the steering mechanism to adjust the actual steering torque to the target steering torque, which provides the driver with a natural steering feel.

[0003] Against this backdrop Figure 1 This is a partial excerpt from WO2019115563A1, which discloses a corresponding method 10 for determining the target steering torque requirement 22. A basic steering torque 12 is determined based on input variables of rack force (RackF) and vehicle speed (Vspd). Additionally, a restoring torque 14 is determined using input variables of steering wheel angle (Ipos), driving torque (Dmom), and vehicle speed (Vspd). Furthermore, a damping torque 16 is determined using input variables of steering wheel angular velocity (Ivel), driving torque (Dmom), and vehicle speed (Vspd). Additionally, a hysteresis torque 18 is determined based on input variables of driving torque (Dmom) and vehicle speed (Vspd). Other individual torques are also possible, but are irrelevant to this invention. Then, the individual torques 12, 14, 16, and 18 are combined to form a total torque 20 that determines the target steering torque requirement 22.

[0004] However, regarding the restoring torque 14, damping torque 16, and hysteresis torque 18, WO2019115563A1 discloses that, apart from vehicle speed, the input variables used are all variables directly related to the driver's input or the position or movement of the steering device (steering wheel, lever). However, the result is that those parameters affected by the control outcome happen to be used as input variables. This is because adjusting the actual steering torque to the target steering torque demand through the manipulation variables provided for the actuators affects the input variables used. In other words, changes during the coordination of steering feel affect the driver's torque feedback, and thus consequently affect driver-dependent functions, which, according to the prior art, are used as input variables to determine the individual torques 14, 16, and 18. As a result, the control mechanism includes inherent additional loops. Feeding back the control variables and using them as input signals is disadvantageous, at least in terms of control speed, delay, and the control stability attributable to this.

[0005] Furthermore, when the steering feel is readjusted or altered (non-linearly related), the steering torque varies with the vehicle's lateral acceleration and is therefore more difficult to predict. This is especially true because the steering torque always includes a damping component that is coordinated with the steering feel.

[0006] Additionally, inherent loops can cause a decrease in steering behavior, particularly at the center position of the steering system. This occurs when the estimated driving torque deviates from the actually applied torque. Such steering behavior is generally undesirable.

[0007] The existing methods require improvements regarding different vehicle parameters (e.g., the weight of the equipment). For example, a scaling factor is used to account for weight adjustment when determining the basic steering torque in order to provide the driver with a consistent steering feel. As a result, other functions using steering torque as an input variable must also be adjusted. This process involves considerable effort, is quite complex, and is often overlooked.

[0008] In a similar manner, according to existing technology, changes in road surface friction are considered indirectly only through the force feedback feature field in order to report friction changes to the driver. Summary of the Invention

[0009] Therefore, the object of the present invention is to provide a method for determining target steering torque requirements, in which these disadvantages can be eliminated or at least reduced.

[0010] This objective is achieved through the subject matter of an independent technical solution. Among other things, a method, a steering system, a computer program product (or control unit), and a storage medium are provided. Advantageous embodiments are given in the dependent technical solutions. Various aspects are explained with reference to the method, and the remaining aspects are explained with reference to the apparatus. However, these aspects may be appropriately interchanged.

[0011] According to a first aspect, a method is provided for determining the steering hysteresis requirement of a vehicle's steering system. The steering system is part of the vehicle's steering system and is coupled to at least one actuator. The actuator is configured to apply a steering torque to the steering system. The method includes the step of determining the steering hysteresis requirement based on at least one rack force of the steering system. A steering hysteresis demand forms at least a portion of a target steering torque, which can be applied to a steering device by at least one actuator, wherein the steering hysteresis demand is characterized by an absolute limit value and an absolute gradient value, and the rack force is considered when determining the absolute limit value and the absolute gradient value of the steering hysteresis demand; wherein the method further includes the steps of: multiplying at least a first function value by a second function value to determine the absolute limit value of the steering hysteresis demand, wherein the first function value is determined at least based on the rack force, and wherein the second function value is determined at least based on the vehicle speed; and multiplying a third function value by a fourth function value to determine the absolute gradient value of the steering hysteresis demand, wherein the third function value depends at least on the absolute limit value of the steering hysteresis demand, a steering position determined by the steering system, a steering speed determined by the steering system, and the steering hysteresis demand, and wherein the fourth function value is determined at least based on the vehicle speed.

[0012] The rack force has a substantially fixed relative ratio to the vehicle's lateral acceleration. As a result, the rack force is independent of the typically variable coordination or readjustment of steering feel, and the driver's steering feel can be adjusted via actuators coupled to the steering mechanism (steering wheel, lever). Therefore, the control loop uses the rack force without an additional inherent loop. The inherent loop provided in the prior art represents damping of the hysteresis behavior of torque. In contrast, the hysteresis of the rack force is lower and more consistent because the rack force does not include this coordination-related damping component. For this reason, it is advantageous that the determination of steering hysteresis requirements is more robust in terms of adjusting the driving feel, and on the other hand, control can be initiated more quickly due to the shorter settling time. Since the relative ratio of the rack force to lateral acceleration is substantially fixed, changes in road surface friction can also be directly considered using the rack force. Advantageously, the indirect consideration using characteristic fields, necessary in the prior art, can be avoided. Therefore, changes in friction are immediately taken into account without any time delay (without additional intermediate steps), wherein the determination of steering hysteresis requirements still has reduced complexity.

[0013] Steering lag requirements can also be determined based at least on vehicle speed, the steering position determined by the vehicle's steering system, and the steering speed determined by the steering system. This allows for a more precise determination of steering lag requirements.

[0014] The steering position determined by the vehicle's steering system can be, for example, the position of the steering mechanism, i.e., steering deflection. This position can also be wheel deflection based on the straight-ahead position. Furthermore, this position can be the lateral displacement of the rack relative to its normal position (center position), or the displacement of the tie rod relative to its normal position (center position). Information about the position can also be provided by a drive (e.g., a motor) within the steering system. The position can also be the angle of a joint associated with the steering system. Accordingly, this position is the position of a part of the steering system determined by the steering system, which, in the case of steering deflection, shifts relative to its normal position (straight-ahead position). Alternatively, the aforementioned position within the control unit can also be determined by a conversion based on a reference position (e.g., converting the motor position to the rack position).

[0015] The steering speed determined by the vehicle's steering system can be, for example, the speed of the steering mechanism, i.e., the rotational speed of the steering mechanism. However, this speed can also be the deflection rotational speed of the wheels (steering speed). Furthermore, this speed can also be the displacement speed of the rack relative to its normal position (center position), or the displacement speed of the tie rod relative to its normal position (center position). Information about the position can also be provided by a drive (e.g., a motor) within the steering system. Accordingly, this speed is the displacement speed, rotational speed, or steering speed of a part of the steering system determined by the steering system, which, in the event of steering deflection, shifts relative to its normal position (straight-ahead position). Typically, the aforementioned speeds are also determined within the control unit through a conversion based on a reference speed (e.g., motor speed converted to rack speed).

[0016] Alternatively or cumulatively, steering hysteresis demand can be characterized by absolute limit values ​​and absolute gradient values. Then, rack force can be considered when determining both the absolute limit values ​​and absolute gradient values ​​of the steering hysteresis demand. The rack force is advantageously used for both sub-parameters of the steering hysteresis demand, allowing for robust and rapid determination of hysteresis.

[0017] In addition, the method includes the step of multiplying at least the first function value by the second function value in order to determine the absolute limit of the hysteresis demand.

[0018] The first function value can be determined at least based on the rack force.

[0019] The second function value can be determined at least based on the vehicle speed.

[0020] In addition, the method includes the step of multiplying the third function value by the fourth function value in order to determine the absolute gradient value of the steering hysteresis demand.

[0021] The third function value can be determined at least based on the absolute limit of the steering hysteresis requirement, the steering position determined by the steering system, the steering speed determined by the steering system, and the steering hysteresis requirement.

[0022] The fourth function value can be determined at least based on the vehicle speed. As a result, the limit value and gradient value of the steering hysteresis demand can be accurately determined, allowing the overall steering hysteresis demand to be determined as needed.

[0023] At least one of the first to fourth function values ​​can be determined based on a function that is at least partially defined and / or through a characteristic curve and / or through a characteristic field and / or through a lookup table. As a result, the function values ​​can be predetermined based on test measurements and can be used in driving situations.

[0024] At least partially defined functions and / or characteristic curves and / or characteristic fields and / or lookup tables can vary according to the desired steering feel. In this way, for example, the determination of steering lag demand can be adapted to a desired driving style. According to existing techniques, functions, eigenvalues, or tables are also used to reference scaling factors to adapt the steering feel to the changing suspension loads that the steering system must withstand. In contrast, rack force dependence itself advantageously adjusts the steering lag demand for different suspension loads (vehicle parameters) for different vehicle configurations. Therefore, functions, eigenvalues, or tables have fewer variables and lower complexity, thus improving the accuracy of determination.

[0025] The rack force can be provided based on measurements, estimates from a steering model, or a vehicle model. In this regard, sensors can be provided to measure the applied rack force to provide the corresponding value. The rack force can also be determined in advance using a model and based on vehicle parameters and vehicle speed. This possibility is based on the essentially fixed relative ratio of the rack force to the vehicle's lateral acceleration. Furthermore, the rack force can be based on estimates, provided the corresponding steering system is based on steering-related variables. Of course, these methods can also be combined.

[0026] In particular, this method is implemented by a computer. The determination of steering hysteresis requirements can be correspondingly determined by the data processing unit, which offers advantages in terms of accuracy and speed. Furthermore, the determination within the vehicle supported by the data processing unit is easy to implement, for example, through a control device.

[0027] If the underlying steering system does not have a rack, but instead has a center rod arranged between the tie rods, the center rod force can be used instead of the rack force to determine the steering lag requirement. For this type of center rod, its relative ratio to the vehicle's lateral acceleration is also basically fixed.

[0028] According to a second aspect, a steering system for a vehicle is also provided. The steering system includes at least one steering element, a rack, a control unit, and at least one actuator. The control unit is coupled to the actuator. The control unit is configured to determine a steering hysteresis requirement of the steering element according to the method described herein. The steering hysteresis requirement forms at least a portion of a target steering torque that can be applied to the steering element by the at least one actuator, wherein the steering hysteresis requirement is characterized by an absolute limit value and an absolute gradient value, and the rack force is taken into account when determining both the absolute limit value and the absolute gradient value of the steering hysteresis requirement. The steering system can thus appropriately limit the steering hysteresis requirement and act appropriately on the steering element, thereby improving the driver's steering feel because the determination can be made faster and more accurately.

[0029] Alternatively or cumulatively, the control device may include at least one processor and may be coupled to a memory device. At least partially defined functions and / or characteristic curves and / or characteristic fields and / or lookup tables are stored in the memory device, such that the control device can determine at least one of a first to a fourth function value based on data from the memory device. Then, using the memory device, predetermined, measured, modeled, or estimated function values ​​for different configurations of steering feel can also be made available for processing by the control device.

[0030] Furthermore, the steering system may include at least one sensor through which the rack force applied to the rack can be measured. Therefore, advantageously, the rack force can be measured independently of time. The corresponding measurement value can then be made available to the control unit to determine the steering hysteresis requirement.

[0031] The steering system can be a steer-by-wire system or an electromechanical steering system. Therefore, determining the steering hysteresis requirement is particularly useful for steering systems where there is no mechanical connection between the steering mechanism and the steerable components used to directly change the direction of the vehicle.

[0032] All features explained in the second aspect can be converted to the first aspect individually or in (sub)combinations.

[0033] According to a third aspect, a control unit (or computer program product) is provided. The control unit (or computer program product) includes commands that, when executed by the control unit (or computer), cause the control unit (or computer) to determine a steering hysteresis demand according to the method described herein.

[0034] According to a fourth aspect, a computer-readable storage medium is provided. The storage medium includes commands that, when executed by a computer, cause the computer to determine steering hysteresis demand based on at least one rack force of the steering system.

[0035] All features explained in relation to the third and fourth aspects can be converted to the first and / or second aspects individually or in (sub)combinations, and can also be converted in the reverse direction.

[0036] The invention can also be improved in the following ways: the steering damping requirement and / or steering return torque requirement are also in the method, steering system, computer program product (or control unit) and storage medium, as will be explained below.

[0037] In this context, the total target torque requirement is determined as follows: it includes steering hysteresis requirements, steering damping requirements, and / or steering recovery torque requirements. A scaling factor may be considered. The individual target torque requirements within the total target torque requirement are determined at least based on rack forces, as described herein. The resulting advantages are cumulatively applied to the total target torque requirement.

[0038] According to an optional fifth aspect, the method according to the invention can therefore be supplemented by a method for determining the steering damping requirement of a vehicle steering system. This supplementary method comprises or includes the step of determining the steering damping requirement based on at least one rack force of the steering system. Thus, the steering damping requirement can form part of a target steering torque (total target torque requirement), which can be applied to the steering system by the at least one actuator.

[0039] Steering damping requirements can also be determined based at least on vehicle speed, steering position determined by the vehicle's steering system, and steering speed determined by the steering system. This allows for a more precise determination of steering damping requirements.

[0040] Alternatively or cumulatively, the method may also include at least the step of multiplying at least a first function value by a second function value in order to determine the steering damping requirement.

[0041] The first function value can be determined at least based on the rack force, and the second function value can be determined at least based on the vehicle speed, the steering position determined by the steering system, and the steering speed determined by the steering system. As a result, the steering damping requirement can be determined in a straightforward, demand-based manner.

[0042] At least one of the first to second function values ​​can be determined based on a function that is at least partially defined and / or through a characteristic curve and / or through a characteristic field and / or a lookup table. As a result, the function values ​​can be determined in advance based on test measurements and can be used in driving situations.

[0043] At least partially defined functions and / or characteristic curves and / or characteristic fields and / or lookup tables can vary according to the desired steering feel. In this way, for example, the determination of steering damping requirements can be adapted to a desired driving style. According to existing techniques, functions, eigenvalues, or tables are also used to reference scaling factors to adapt the steering feel to the changing suspension loads that the steering system must withstand. In contrast, rack force dependence itself advantageously adjusts the steering damping component for different suspension loads (vehicle parameters) of different vehicle configurations. Therefore, functions, eigenvalues, or tables have fewer variables and lower complexity, thus improving the accuracy of determination.

[0044] If the underlying steering system does not include a rack, but instead includes a center rod arranged between the tie rods, the center rod force can be used instead of the rack force to determine the steering damping requirements. For such a center rod, its relative ratio to the vehicle's lateral acceleration is also basically fixed.

[0045] According to an optional sixth aspect, the steering system according to the invention may have a control device configured to determine the steering damping requirement of the steering device according to the method described above. The steering damping requirement may form at least a portion of a target steering torque, which may be applied to the steering device by at least one actuator. The steering system thus allows the steering damping requirement to be appropriately determined and applied appropriately to the steering device, thereby improving the driver's steering feel because the determination can be faster and more precise.

[0046] If the steering system is a steer-by-wire or electromechanical steering system, the determination of steering damping requirements is particularly useful for steering systems where there is no mechanical connection between the steering mechanism and the steerable components used to directly change the direction of the vehicle.

[0047] All features explained in the sixth aspect can be transformed into the fifth aspect individually or in (sub)combinations.

[0048] According to an optional seventh aspect, the control unit (or computer program product) according to the invention may include commands that, when executed by the control unit (or computer), cause the control unit (or computer) to determine steering damping requirements according to the method described herein.

[0049] According to an optional eighth aspect, the computer-readable storage medium according to the invention may include instructions that, when executed by a computer, cause the computer to determine steering damping requirements based on at least one rack force of the steering system.

[0050] All features explained in the seventh and eighth aspects can be transformed into the fifth and / or sixth aspects individually or in (sub)combinations, and can also be transformed in the reverse direction.

[0051] According to an optional ninth aspect, the method according to the invention can also be combined with the determination of the steering return torque requirement of the vehicle steering system—it can be combined with or not combined with the methods described above for determining the steering damping requirement of the steering system. A supplementary method for determining the steering return torque requirement may include the step of determining the steering return torque requirement based on at least one rack force of the steering system. Therefore, the steering return torque requirement can form part of a target steering torque (total target torque requirement), which can be applied to the steering system by at least one actuator.

[0052] Alternatively or cumulatively, the steering return torque requirement can also be determined based at least on vehicle speed, steering position determined by the vehicle's steering system, and steering speed determined by the steering system. As a result, the steering return torque requirement can be determined more accurately.

[0053] The steering return torque requirement can be determined additionally or alternatively based on a proportional control loop with a scaling factor and a basic target speed.

[0054] Rack force can be considered when determining the scaling factor and the basic target speed. The proportional control loop allows for particularly rapid readjustment to determine the steering return torque requirement. The rack force is advantageously used for two sub-parameters of the proportional control loop, making the control loop robust and fast.

[0055] Alternatively or cumulatively, the determination may also include at least the step of multiplying at least a first function value by a second function value in order to determine the product value.

[0056] The first function value can be determined at least based on the rack force.

[0057] The second function value can be determined at least based on the vehicle speed and the steering position determined by the steering system.

[0058] Additionally, the method may include a step of subtracting the steering speed determined by the steering position from the product value in order to determine the basic target speed of the proportional control loop.

[0059] The method may also include the step of multiplying the basic target velocity by a third function value and a fourth function value.

[0060] The third and fourth function values ​​can be used together to represent the scaling factor.

[0061] The third function value can be determined at least based on the rack force. The fourth function value can be determined at least based on the vehicle speed and the steering position determined by the steering system. As a result, the scaling factor and the basic target speed can be accurately determined, thereby allowing the steering return torque requirement to be determined as needed.

[0062] At least one of the first to fourth function values ​​can be determined based on a function that is at least partially defined and / or through a characteristic curve and / or through a characteristic field and / or through a lookup table. As a result, the function values ​​can be determined in advance based on test measurements and can be used in driving situations.

[0063] The functions and / or characteristic curves and / or characteristic fields and / or lookup tables used to determine the steering return torque requirement, which are at least partially defined, can vary according to the desired steering feel. In this way, for example, the determination of the steering return torque requirement can be adapted to a desired driving style. According to existing techniques, functions, eigenvalues, or tables are also used to reference scaling factors to adapt the steering feel to the changing suspension loads that the steering system must withstand. In contrast, rack force dependence itself advantageously adjusts the active return component for different suspension loads (vehicle parameters) for different vehicle configurations. Therefore, functions, eigenvalues, or tables have fewer variables and lower complexity, thus improving the accuracy of the determination.

[0064] The rack force can be provided based on measured values, estimates based on a steering model, or a vehicle model. In this regard, sensors can be provided to measure the applied rack force to provide the corresponding value. The rack force can also be determined in advance using a model and based on vehicle parameters and vehicle speed. This possibility is based on the essentially fixed relative ratio of rack force to vehicle lateral acceleration. Furthermore, the rack force can be based on estimates, provided the corresponding steering system is based on steering-related variables, vehicle parameters, and vehicle speed. Of course, these methods can also be combined.

[0065] The method for determining the steering return torque requirement can also be implemented by a computer. The determination of the steering return torque requirement can be correspondingly handled by a data processing unit, which offers advantages in terms of accuracy and speed. If the underlying steering system does not include a rack but instead includes a center rod arranged between the tie rods, the center rod force can be used instead of the rack force to determine the steering return torque requirement. For such a center rod, its relative ratio to the vehicle's lateral acceleration is also essentially fixed.

[0066] According to an optional tenth aspect, the vehicle's steering system according to the invention can be configured to determine the steering return torque requirement of the steering device according to the method described above. The steering return torque requirement can form at least a portion of a target steering torque, which can be applied to the steering device by at least one actuator. The steering system thus allows the steering return torque requirement to be appropriately determined and applied appropriately to the steering device, thereby improving the driver's steering feel because the determination can be faster and more accurate.

[0067] As already mentioned, the control device may include at least one processor and may be coupled to a memory device. At least partially defined functions and / or characteristic curves and / or characteristic fields and / or lookup tables for determining the steering return torque requirement may be stored in the memory device, such that the control device can determine at least one of a first to a fourth function value based on data from the memory device. Then, using the memory device, predetermined, measured, modeled, or estimated function values ​​for different configurations of steering feel can also be made available for processing by the control device.

[0068] If the steering system includes at least one sensor that can measure the rack force applied to the rack, the corresponding measurement can be used by the control unit to determine the steering return torque requirement.

[0069] Therefore, determining the steering return torque requirement is particularly useful for steering systems where there is no mechanical connection between the steering mechanism and the steerable components used to directly change the direction of the vehicle.

[0070] All features explained in relation to the tenth aspect can be transformed into the ninth aspect individually or in (sub)combinations, and this transformation is mutual.

[0071] According to an optional eleventh aspect, the control unit (or computer program product) according to the invention may include instructions that, when executed by the control unit (or computer), cause the control unit (or computer) to determine the steering return torque requirement according to the method described herein.

[0072] According to an optional twelfth aspect, the computer-readable storage medium according to the invention may include instructions that, when executed by a computer, cause the computer to determine the steering return torque requirement based on at least one rack force of the steering system.

[0073] All features explained in relation to the eleventh and twelfth aspects can be transformed into the ninth and / or tenth aspects individually or in (sub)combinations, and can also be transformed in the reverse direction. Attached Figure Description

[0074] The invention and its further advantageous embodiments and improvements are described and explained in more detail below with reference to the examples shown in the accompanying drawings. According to the invention, the features seen in the specification and drawings can be used individually or in any combination. In the drawings: Figure 1 It is a simplified schematic representation of the total steering torque requirement determined based on existing technology; Figure 2 It is a simplified schematic representation of the steering system; Figure 3This is a simplified schematic representation of determining the steering return torque requirement according to one embodiment; Figure 4 This is a simplified schematic representation of determining steering hysteresis demand according to one embodiment; and Figure 5 This is a simplified schematic representation of determining steering damping requirements according to one embodiment. Detailed Implementation

[0075] Figure 2 This is a simplified schematic representation of the steering system 30. The steering system 30 includes a steering mechanism 32, in this case a steering wheel. The steering mechanism 32 is coupled to an axle 34. An actuator 36 that interacts with the axle 34 is arranged on the axle. A steering variable can be applied to the actuator 36 to apply a torque on the axle 34 according to the steering variable, and thus report the desired steering feel to the driver.

[0076] The steering mechanism 32 and its axle 34 are mechanically separated from the rest of the steering system 30, in which steerable wheels 40A and 40B are shown by way of example. Wheels 40A and 40B are each connected to wheel supports 42A and 42B, which in turn are connected to tie rods 44A and 44B in their respective cases. A rack 46 is arranged between tie rods 44A and 44B. The rack 46 provides a mechanical connection to wheels 40A and 40B, ensuring that the two wheels are always aligned parallel to each other.

[0077] Actuator 48 (pinion) is connected to rack 46 and can move rack out of its center position to deflect wheels 40A, 40B relative to their normal position.

[0078] The sensor 50, which measures the rack force, is also connected to the rack 46. For example, the sensor 50 could be a strain gauge.

[0079] A second sensor 52 is also present. The second sensor 52 is configured to determine the relative position of the wheel carrier 42A with respect to its normal position. This relative position represents the steering position determined by the vehicle's steering system. Sensor 52 is also configured to measure the rotational speed of the wheel carrier 42A relative to the center of rotation when the position of the wheel 40B changes. This does not refer to the rotation of the wheel itself, but rather to the steering rotation. This rotational speed represents the steering speed determined by the vehicle's steering system.

[0080] The steering system also includes a control unit 54 with a processor. The control unit 54 is coupled to the actuator 36 and also to sensors 50, 52. Sensors 50, 52 transmit corresponding measurements of rack force, steering position, and steering speed to the control unit 54. The control unit also receives information about the vehicle speed. The vehicle speed can also optionally be determined by sensor 52 or by other suitable means. The control unit 54 is configured to determine at least the steering return torque requirement and / or steering hysteresis requirement and / or steering damping requirement based on the received information. Alternatively or cumulatively, the control unit 54 can also determine the total target torque requirement based on the desired combination of individual torques.

[0081] The control device 54 may optionally be coupled to a memory device in which partially defined functions, feature values ​​or reference tables may be stored so that they can be used in the determinations made by the control device 54.

[0082] Optionally, control device 54 can be configured to compare a specific steering torque demand with the actual steering torque. A manipulation variable for actuator 36 can then be determined and transmitted to the actuator to match the actual steering torque with the steering torque demand. In any case, control of actuator 36 is based on the specific steering torque demand as a variable in order to transmit the desired steering feel to the driver.

[0083] Figure 3 This is a simplified schematic representation of the determination of steering return torque requirements according to an embodiment 60.

[0084] In block 62, a first function value is determined based on the steering position Pos and vehicle speed Vspd, as determined by the vehicle's steering system. In block 64, a second function value is determined based on the rack force RackF. In block 66, the first function value is multiplied by the second function value to determine the product. Then, in block 68, the steering speed Vel, determined by the vehicle's steering system, is subtracted from the product. In this way, the basic target speed is determined.

[0085] In block 70, a third function value is determined based on the steering position Pos, determined either inside the vehicle by the steering system or outside the vehicle, and the vehicle speed Vspd. In block 72, a fourth function value is determined based on the rack force RackF. The third and fourth function values ​​represent scaling factors. Then, in block 74, the third and fourth function values ​​are multiplied by the product value from block 68 (i.e., the basic target speed). As a result, the steering return torque requirement can be determined in block 76.

[0086] Blocks 62, 64, 70, and 72 may include at least partially defined functions and / or eigenvalues ​​and / or characteristic fields and / or reference tables, so as to enable the values ​​determined in their respective cases to be adapted to the desired driving feel.

[0087] Figure 4 This is a simplified schematic representation of the determination of steering hysteresis requirements according to Example 80.

[0088] In block 82, the first function value is determined based on the rack force RackF. In block 84, the second function value is determined based on the vehicle speed Vspd. In block 86, the first function value is multiplied by the second function value. As a result, the absolute limit of the steering hysteresis requirement is determined.

[0089] Additionally, in block 90, a third function value is determined based on the steering position Pos determined by the steering system, the steering speed Vel determined by the steering system, and a predetermined limit value. As an additional input variable for determining the third function value, block 90 includes a feedback loop so that the determined steering hysteresis requirement is also taken into account.

[0090] In block 92, the value of the fourth function is determined based on the rack force RackF.

[0091] In block 94, the third function value is multiplied by the fourth function value to determine the absolute gradient value (Slope) of the steering hysteresis demand.

[0092] As a result, the steering hysteresis requirement is determined by both the limit value and the gradient, thereby determining the situation-related steering hysteresis requirement in block 98.

[0093] Blocks 82, 84, 90, and 92 may include at least partially defined functions and / or eigenvalues ​​and / or characteristic fields and / or reference tables to enable the values ​​determined in their respective cases to be adapted to the desired driving experience.

[0094] Figure 5 This is a simplified schematic representation of the determination of steering damping requirements according to Example 100.

[0095] In block 102, a first function value is determined based on the vehicle speed Vspd, the steering position Pos determined by the vehicle's steering system, and the steering speed Vel determined by the vehicle's steering system. In block 104, a second function value is determined based on the rack force RackF. In block 106, the first function value is multiplied by the second function value to determine the steering damping requirement in block 108.

[0096] Blocks 102 and 108 may include at least partially defined functions and / or eigenvalues ​​and / or eigenfields and / or reference tables to enable the values ​​determined in their respective cases to be adapted to the desired driving feel.

[0097] While the invention has been shown and described with respect to one or more embodiments, those skilled in the art will discover equivalent variations and modifications upon reading and understanding this specification and the accompanying drawings. Furthermore, although a particular feature of this disclosure may be disclosed with respect to only one of several embodiments, that feature may be combined with one or more other features of other embodiments.

Claims

1. A method for determining the steering hysteresis requirement of a vehicle's steering system (32), wherein, The steering device (32) is part of the vehicle's steering system (30) and is coupled to at least one actuator (36), the actuator being configured to apply a steering torque to the steering device (32), the method comprising the following steps: The steering hysteresis requirement is determined based on at least one rack force (RackF) of the steering system (30), wherein the steering hysteresis requirement forms at least a portion of a target steering torque that can be applied to the steering device (32) by the at least one actuator (36), wherein the steering hysteresis requirement is characterized by an absolute limit and an absolute slope, and the rack force (RackF) is taken into account when determining the absolute limit and the absolute slope of the steering hysteresis requirement. The method further includes the following steps: At least a first function value is multiplied by a second function value to determine the absolute limit of the steering lag requirement, wherein the first function value is determined at least based on the rack force (RackF), and wherein the second function value is determined at least based on the vehicle speed (Vspd). The third function value is multiplied by the fourth function value to determine the absolute gradient value (Slope) of the steering lag requirement, wherein the third function value depends at least on the absolute limit value of the steering lag requirement, the steering position (Pos) determined by the steering system (30), the steering speed (Vel) determined by the steering system (30), and the steering lag requirement, and wherein the fourth function value is determined at least based on the vehicle speed (Vspd).

2. The method according to claim 1, wherein, At least one of the first to fourth function values ​​is determined based on at least partially defined functions and / or characteristic curves and / or characteristic fields and / or lookup tables.

3. The method according to claim 2, wherein, The at least partially defined functions and / or characteristic curves and / or characteristic fields and / or lookup tables can vary according to the desired sense of steering.

4. The method according to any one of claims 1 to 3, wherein, The rack force (RackF) is provided based on measurements, estimates from the steering model, or the vehicle model.

5. The method according to any one of claims 1 to 3, wherein, The method is implemented by a computer.

6. A steering system (30) for a vehicle, wherein, The steering system includes at least one steering device (32), a rack (46), a control device (54), and at least one actuator (36), wherein the control device (54) is coupled to the actuator (36). The control device (54) is configured to determine the steering lag requirement of the steering device (32) by the method according to any one of claims 1 to 5.

7. The steering system (30) according to claim 6, wherein, The control device (54) is configured to determine the steering hysteresis requirement according to the method, wherein the control device (54) includes at least one processor connected in parallel to a memory device, wherein at least partially defined functions and / or characteristic curves and / or characteristic fields and / or lookup tables are stored in the memory device, such that the control device (54) can determine at least one of a first function value to a fourth function value based on data from the memory device, and wherein the processor is designed to determine the steering hysteresis requirement according to the method.

8. The steering system (30) according to claim 6 or 7, wherein, The steering system also includes at least one sensor (50) that can measure the rack force (RackF) applied to the rack (46).

9. The steering system (30) according to claim 6 or 7, characterized in that, The steering system is a steer-by-wire steering system or an electromechanical steering system.

10. A control unit comprising a command that, when executed by the control unit, causes the control unit to determine the steering hysteresis demand using the method of any one of claims 1 to 5.

11. A computer-readable storage medium comprising a command that, when executed by a computer, causes the computer to determine steering hysteresis demand based on at least one rack force (RackF) of a steering system (30) according to any one of claims 1 to 5.

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