METHOD FOR DETERMINING A STEERING RETURN MOMENT REQUIREMENT, A STEERING SYSTEM, A COMPUTER PROGRAM PRODUCT, AND A STORAGE MEDIUM

Abstract

The present disclosure relates to a method for determining a steering return moment requirement of a steering device of a vehicle, to a steering system, to a computer program product, and to 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 configured to apply a steering moment to the steering device. The method comprises at least the step of determining the steering return moment requirement based on at least one rack force of the steering system. The steering return moment requirement forms at least a portion of a target steering moment which can be applied to the steering device by the at least one actuator.

Claims

1. A method for determining a steering return moment requirement of a steering device of a vehicle, wherein the steering device is part of a steering system of the vehicle and is coupled to at least one actuator which is configured to apply a steering moment to the steering device, the method having the step of: determining the steering return moment requirement based on at least one rack force of the steering system, wherein the steering return moment requirement forms at least a portion of a target steering moment with which the steering device can be acted upon by the at least one actuator.

2. The method according to claim 1, wherein the steering return moment requirement is further determined based at least on one of a vehicle speed, a steering position determined by the steering system of the vehicle, and a steering velocity determined by the steering system.

3. The method according to claim 1, wherein the steering return moment requirement is determined using a proportional control loop with a proportionality factor and a base target velocity, and wherein the rack force is taken into account both when determining the proportionality factor and when determining the base target velocity.

4. The method according to claim 3, the method further comprising at least the steps of: multiplying at least one first function value and one second function value in order to determine a product value, wherein the first function value is determined at least as a function of the rack force, and wherein the second function value is determined at least as a function of a vehicle speed and of a steering position determined by the steering system, subtracting a steering velocity determined by the steering position from the product value in order to determine the base target velocity of the proportional control loop, and multiplying the base target velocity by a third and a fourth function value, wherein the third function value is determined at least as a function of the rack force, and the fourth function value is determined at least as a function of the vehicle speed and of the steering position determined by the steering system.

5. The method according to claim 4, wherein at least one of the first to fourth function values is determined based on at least partially defined functions and/or by characteristic curves and/or by characteristic maps and/or by look-up tables.

6. The method according to claim 5, wherein the at least partially defined functions and/or characteristic curves and/or characteristic maps and/or look-up tables are variable as a function of a desired steering feel.

7. The method according to claim 1, wherein the rack force is provided based on one of a measurement, an estimation from a steering model, or a vehicle model.

8. The method according to, claim 1, wherein the method is computer-implemented.

9. A steering system for a vehicle, the steering system comprising at least one steering device, a rack, a control device and at least one actuator, wherein the control device is coupled to the actuator, wherein the control device is configured to determine a steering return moment requirement of the steering device according to the method according to claim 4, and wherein the steering return moment requirement forms at least a portion of a target steering moment with which the steering device can be acted upon by the at least one actuator.

10. The steering system according to claim 9, wherein the control device is configured to determine the steering return moment requirement, wherein the control device comprises at least one processor and is coupled to a storage device, wherein at least partially defined functions and/or characteristic curves and/or characteristic maps and/or look-up tables are stored in the storage device, such that at least one of the first to fourth function values can be determined by the control device based on data from the storage device, and wherein the processor is designed in such a way that it determines the steering return moment requirement.

11. The steering system according to claim 9, the steering system further comprising at least one sensor by which a rack force applied to the rack can be measured.

12. The steering system according to claim 9, wherein the steering system is a steering-by-wire steering system.

13. A computer program product, comprising instructions which, when the program is executed by a computer, cause the computer to determine the steering return moment requirement according to the method according to claim 1.

14. A computer-readable storage medium, comprising instructions which, when a program is executed by a computer, cause the computer to determine a steering return moment requirement based on at least one rack force of the steering system.

15. The method according to claim 2, wherein the steering return moment requirement is determined using a proportional control loop with a proportionality factor and a base target velocity, and wherein the rack force is taken into account both when determining the proportionality factor and when determining the base target velocity.

16. The method according to claim 15, the method further comprising at least the steps of: multiplying at least one first function value and one second function value in order to determine a product value, wherein the first function value is determined at least as a function of the rack force, and wherein the second function value is determined at least as a function of the vehicle speed (Vspd) and of the steering position (Pos) determined by the steering system (30), subtracting the steering velocity (Vel) determined by the steering position from the product value in order to determine the base target velocity of the proportional control loop, and multiplying the base target velocity by a third and a fourth function value, wherein the third function value is determined at least as a function of the rack force (RackF), and the fourth function value is determined at least as a function of the vehicle speed (Vspd) and of the steering position (30) determined by the steering system (Pos).

17. The method according to claim 16, wherein the rack force is provided based on one of a measurement, an estimation from a steering model, or a vehicle model.

18. The method according to claim 17, wherein the method is computer-implemented.

19. A steering system for a vehicle, the steering system comprising at least one steering device, a rack, a control device and at least one actuator, wherein the control device is coupled to the actuator, wherein the control device is configured to determine a steering return moment requirement of the steering device according to the method according to claim 1, and wherein the steering return moment requirement forms at least a portion of a target steering moment with which the steering device can be acted upon by the at least one actuator.

20. The steering system according to claim 9, wherein the steering system is an electromechanical steering system.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0067] The disclosure and further advantageous exemplary arrangements and developments thereof are described and explained in more detail below with reference to the examples shown in the drawings. The features found in the description and the drawings can be used individually or collectively in any combination according to the disclosure. In the drawings:

[0068] FIG. 1 is a simplified schematic illustration of the determination of a total steering moment requirement according to the prior art,

[0069] FIG. 2 is a simplified schematic illustration of a steering system,

[0070] FIG. 3 is a simplified schematic illustration of the determination of the steering return moment requirement according to an exemplary arrangement,

[0071] FIG. 4 is a simplified schematic illustration of the determination of the steering hysteresis requirement according to an exemplary arrangement, and

[0072] FIG. 5 is a simplified schematic illustration of the determination of the steering damping requirement according to an exemplary arrangement.

DETAILED DESCRIPTION

[0073] FIG. 2 is a simplified schematic illustration of a steering system 30. The steering system 30 comprises a steering device 32, in this case a steering wheel. The steering device 32 is coupled to an axle 34. An actuator 36, which interacts with the axle 34, is arranged on the axle. An actuating variable can be applied to the actuator 36 in order to exert a torque on the axle 34 as a function of the actuating variable, and thus to report a desired steering feel to the driver.

[0074] The steering device 32 and its axle 34 are mechanically separated from the rest of the steering system 30, of which the steerable wheels 40A, 40B are shown here by way of example.

[0075] The wheels 40A, 40B are each coupled to a wheel carrier 42A, 42B, each of which in turn is coupled to a tie rod 44A, 44B, A rack 46 is arranged between the tie rods 44A, 44B. The rack 46 provides a mechanical coupling for the wheels 40A, 40B so that they are always aligned parallel to one another.

[0076] An actuator 48 (pinion) is coupled to the rack 46 and can move the rack out of its central position in order to cause the wheels 40A, 403 to deflect relative to their normal position.

[0077] In addition, a sensor 50 is coupled to the rack 46, and measures the rack force. Alternatively, the detected values thereof can be used to infer the rack force. For example, in one exemplary arrangement, the sensor 50 can be a strain gauge.

[0078] There is also a second sensor 52. The second sensor 52 is configured to determine a relative position of the wheel carrier 42A with respect to its normal position. This relative position represents a steering position determined by the vehicle's steering system. The sensor 52 is also configured to measure the rotational speed of the wheel carrier 42A with respect to the center of rotation when the position of the wheel 40B changes. Of course, this does not mean the wheel rotation, but the steering rotation. This rotation speed represents a steering velocity determined by the vehicle's steering system.

[0079] The steering system further includes a control device 54 which has a processor. The control device 54 is coupled both to the actuator 36 and to the sensors 50, 52. The sensors 50, 52 transmit corresponding measured values for the rack force, the steering position, and the steering velocity to the control device 54. In addition, the control device 54 receives information about the vehicle speed. The vehicle speed can optionally also be determined by the sensor 52 or by further suitable devices.

[0080] The control device 54 is configured to determine at least a steering return moment requirement and/or a steering hysteresis requirement and/or a steering damping requirement based on the information received. Alternatively or cumulatively, the control device 54 can also determine a total target moment requirement from a desired combination of the individual moments.

[0081] The control device 54 can optionally be coupled to a storage device in which partially defined functions, characteristic values or reference tables can be stored to enable their use for the determination by the control device 54.

[0082] Optionally, the control device 54 can be configured to compare the determined steering moment requirement to an actual steering moment. An actuating variable for the actuator 36 can then be determined and transmitted to it in order to match the actual steering moment to the steering moment requirement. In any case, the determined steering moment requirement is the variable on which the control of the actuator 36 is based in order to convey the desired steering feel to the driver.

[0083] FIG. 8 shows a simplified schematic illustration of the determination of the steering return moment requirement according to an exemplary arrangement 60.

[0084] A first function value is determined in block 62 as a function of a steering position Pos determined by the steering system of the vehicle and the vehicle speed Vspd. A second function value is determined in block 64 as a function of the rack force RackF. The first and second function values are multiplied in block 66 to determine a product value. The steering velocity Vel determined by the steering system of the vehicle is then subtracted from the product value in block 68. In this way, a base target velocity is determined.

[0085] In block 70, a third function value is determined based on a steering position Pos determined internally by the steering system or externally in 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 a proportionality factor. The third and fourth function values are then multiplied in block 74 by the product value from block 68, that is to say the base target velocity. As a result, the steering return moment requirement can be determined in block 76.

[0086] The blocks 62, 64, 70, 72 can include functions and/or characteristic values and/or characteristic maps and/or reference tables that are at least partially defined in order to be able to adapt the values determined in each case to a desired driving experience.

[0087] FIG. 4 shows a simplified schematic illustration of the determination of the steering hysteresis requirement according to an exemplary arrangement 80.

[0088] In block 82, a first function value is determined as a function of the rack force RackF. In block 84, a second function value is determined based on the vehicle speed Vspd. The first and second function values are multiplied in block 86. As a result, an absolute limit value (limit) of the steering hysteresis requirement is determined.

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

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

[0091] The third and fourth function values are multiplied in block 94 in order to determine the absolute slope value (slope) of the steering hysteresis requirement.

[0092] As a result, the steering hysteresis requirement is determined both in the limit value and in the slope, such that the situation-dependent steering hysteresis requirement is determined in block 98.

[0093] The blocks 82, 84, 90, 92 can include functions and/or characteristic values and/or characteristic maps and/or reference tables that are at least partially defined in order to be able to adapt the values determined in each case to a desired driving experience.

[0094] FIG. 5 shows a simplified schematic illustration of the determination of the steering damping requirement according to an exemplary arrangement 100.

[0095] A first function value is determined in block 102 as a function of a vehicle speed Vspd, a steering position Pos determined by the steering system of the vehicle, and a steering velocity Vel determined by the steering system of the vehicle. Based on the rack force RackF, a second function value is determined in block 104. The first and second function values are multiplied in block 106 in order to determine the steering damping requirement in block 108.

[0096] The blocks 102, 108 can include functions and/or characteristic values and/or characteristic maps and/or reference tables that are at least partially defined in order to be able to adapt the values determined in each case to a desired driving experience.

[0097] The steering return moment requirement, the steering hysteresis requirement, and/or the steering damping requirement can advantageously be combined with one another in any combination by finding a total target moment requirement from these. The actuator 36 is then actuated on the basis of this total target moment requirement in order to create an optimal driving experience.

[0098] While the disclosure has been shown and described with respect to one or more implementations, those skilled in the art, upon reading and understanding this specification and the accompanying drawings, will identify equivalent changes and modifications. Furthermore, while a particular feature of the disclosure may have been disclosed in relation to only one of several implementations, that feature may be combined with one or more other features of the other implementations.