STEER-BY-WIRE STEERING SYSTEM FOR A TWO-TRACK VEHICLE

Abstract

A steer-by-wire steering system for a vehicle, having a steering handle, a steering gear actuator mechanically decoupled from the steering handle, a steering sensor which detects a rotational position and/or a rotational movement of the steering handle as a steering command, an electronic control unit which, as a function of the detected steering command, activates the steering gear actuator to set a vehicle wheel steering angle (α), and a hand actuator activatable by the control unit, which generates different types of haptic feedback (R1, R2, R3) for the driver on the steering handle, namely a haptic steering feedback (R1) in which a steering counter torque is applied to the steering handle, a roadway feedback (R2), which correlates with a roadway-side disturbance excitation acting on the vehicle, and a warning feedback (R3), which informs the driver of a fault in the steer-by-wire steering system.

Claims

1. A steer-by-wire steering system for a vehicle, comprising: a steering handle, having a steering gear actuator mechanically decoupled from the steering handle, a steering sensor which detects a rotational position and/or a rotational movement of the steering handle as a steering command, an electronic control unit which, as a function of the detected steering command, activates the steering gear actuator to set a vehicle wheel steering angle (α), and a hand actuator activatable by the control unit, which generates haptic feedback (R1, R2, R3) for the driver on the steering handle, namely a haptic steering feedback (R1), in which a steering counter torque is applied to the steering handle, in particular in a steering process, a roadway feedback (R2), which correlates with a roadway-side disturbance excitation acting on the vehicle, and a warning feedback (R3), which informs the driver of a fault in the steer-by-wire steering system, wherein the control unit is associated with an evaluation unit, by which the haptic roadway feedback (R2) can at least be weakened or deactivated in the event of a steering system fault so that the perceptibility of the warning feedback (R3) is increased for the driver.

2. The steer-by-wire steering system according to claim 1, wherein a steering converter module is associated with the control unit which, in particular during a steering process, generates a steering counter torque signal (S.sub.L), by which the hand actuator is activatable to generate the steering feedback (R1) on the steering handle.

3. The steer-by-wire steering system according to claim 1, wherein a roadway converter module is associated with the control unit which generates a roadway signal (S.sub.F) based on the roadway-side disturbance excitation, by which the hand actuator is activatable to generate the roadway feedback (R2) on the steering handle.

4. The steer-by-wire steering system according to claim 1, wherein a diagnostic module is associated with the control unit which, in the event of a steering system fault, generates a warning signal (S.sub.W), by which the hand actuator is activatable to generate the warning feedback (R3) on the steering handle and/or by which an output unit is activatable to, in particular in addition to the warning feedback (R3), generate an acoustic and/or visual warning message on the output unit.

5. The steer-by-wire steering system according to claim 4, wherein by the diagnostic module for recognizing a steering system fault, at least one steering system parameter, in particular a steering system operating voltage level (U.sub.B), is detectable and comparable to a predefined steering system target parameter, in particular a steering system target operating voltage level (U.sub.SOLL), and that the warning signal (S.sub.W) can be generated by the diagnostic module in particular if the steering system target parameter is exceeded or not reached.

6. The steer-by-wire steering system according claim 1, wherein the haptic feedback (R1, R2, R3) which can be provided on the steering handle can be partially superimposed on one another.

7. The steer-by-wire steering system according to claim 1, wherein the haptic warning feedback (R3) is a steering handle vibration.

8. The steer-by-wire steering system according to claim 1, wherein a signal processing unit activatable by the evaluation unit is interconnected in the signal path from the roadway converter module to the hand actuator, and that in the event of a steering system fault, the signal processing unit is activatable by the evaluation unit so that signal transmission of the roadway signal (S.sub.F) to the hand actuator is blocked or a modified roadway signal (S.sub.F′) can be generated in the signal processing unit, by which a weakened roadway feedback (R2) is applicable to the steering handle.

9. The steer-by-wire steering system according to claim 1, wherein the weakened roadway feedback (R2) has a reduced amplitude and/or a reduced frequency in comparison to the roadway feedback (R2) in normal steering system operation.

10. A method for operating a steer-by-wire steering system according to claim 1.

11. The steer-by-wire steering system according to claim 2, wherein a roadway converter module is associated with the control unit which generates a roadway signal (S.sub.F) based on the roadway-side disturbance excitation, by which the hand actuator is activatable to generate the roadway feedback (R2) on the steering handle.

12. The steer-by-wire steering system according to claim 2, wherein a diagnostic module is associated with the control unit which, in the event of a steering system fault, generates a warning signal (S.sub.W), by which the hand actuator is activatable to generate the warning feedback (R3) on the steering handle and/or by which an output unit is activatable to, in particular in addition to the warning feedback (R3), generate an acoustic and/or visual warning message on the output unit.

13. The steer-by-wire steering system according to claim 3, wherein a diagnostic module is associated with the control unit which, in the event of a steering system fault, generates a warning signal (S.sub.W), by which the hand actuator is activatable to generate the warning feedback (R3) on the steering handle and/or by which an output unit is activatable to, in particular in addition to the warning feedback (R3), generate an acoustic and/or visual warning message on the output unit.

14. The steer-by-wire steering system according claim 2, wherein the haptic feedback (R1, R2, R3) which can be provided on the steering handle (5) can be partially superimposed on one another.

15. The steer-by-wire steering system according claim 3, wherein the haptic feedback (R1, R2, R3) which can be provided on the steering handle can be partially superimposed on one another.

16. The steer-by-wire steering system according claim 4, wherein the haptic feedback (R1, R2, R3) which can be provided on the steering handle can be partially superimposed on one another.

17. The steer-by-wire steering system according claim 5, wherein the haptic feedback (R1, R2, R3) which can be provided on the steering handle can be partially superimposed on one another.

18. The steer-by-wire steering system according to claim 2, wherein the haptic warning feedback (R3) is a steering handle vibration.

19. The steer-by-wire steering system according to claim 3, wherein the haptic warning feedback (R3) is a steering handle vibration.

20. The steer-by-wire steering system according to claim 4, wherein the haptic warning feedback (R3) is a steering handle vibration.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0017] An exemplary embodiment of the invention is described below on the basis of the figures.

[0018] In the figures:

[0019] FIG. 1 shows a schematic diagram of a steer-by-wire steering system in a two-track vehicle;

[0020] FIG. 2 shows a schematic block diagram of the mode of operation of the steer-by-wire steering system of FIG. 1, and

[0021] FIG. 3 shows a schematic block diagram of the mode of operation of a steer-by-wire steering system according to the prior art.

DETAILED DESCRIPTION

[0022] FIG. 1 shows the structure of a steer-by-wire steering system 1 provided in a two-track vehicle 3. The steer-by-wire steering system 1 has a steering wheel 5 as a steering handle, with which a steering sensor 7 and a hand actuator 9 are associated. The steering sensor 7 and the hand actuator 9 are in signal connection with a steering gear actuator 13 and a steering gear sensor system 15, which are associated with a steering gear 17, which has a drive connection to the front wheels 19 of the vehicle 3, with a control unit 11 interconnected.

[0023] To carry out a steering process, the steering sensor 7 detects a rotational position or a rotational movement of the steering wheel 5 and uses this to generate a steering command which is transmitted to the control unit 11. The control unit 11 controls the steering gear actuator 13 as a function of the steering command, whereupon a vehicle wheel steering angle α is set on the front wheels 19 by means of the steering gear 17.

[0024] To give the driver feedback about acting steering forces, roadway-side disturbance excitations, or the state of the steer-by-wire steering system 1, the control unit 11 activates the hand actuator 9, which acts as a force feedback unit, which thereupon generates corresponding haptic feedback on the steering wheel 5. The activation of the hand actuator 9 by the control unit 11 and its structure is described below with reference to FIGS. 2 and 3, wherein FIG. 3 is discussed first, which shows the control unit 11 according to the prior art.

[0025] A steering converter module 21, a roadway converter module 23, and a diagnostic module 25 are associated with the control unit 11 of FIG. 3, each of which is in signal connection with the hand actuator 9.

[0026] By means of the steering gear sensor system 15, a restoring force F.sub.R acting on the front wheels 19 is sensed as an example of a steering parameter and transmitted to the steering converter module 21. The steering converter module 21 generates a steering counter torque signal S.sub.L as a function of the restoring force, using which the hand actuator 9 is activated to apply a steering feedback R1 in the form of a steering counter torque to the steering wheel 5.

[0027] Roadway-side disturbance excitations acting on the front wheels 19 are detected by the steering gear sensor system 15 and transmitted to the roadway converter module 23. The roadway converter module 23 generates a roadway signal S.sub.F on the basis of the disturbance excitations, using which the hand actuator 9 is activated to generate a haptic roadway feedback R2 on the steering wheel 5 that correlates with the disturbance excitations.

[0028] The diagnostic module 25 determines whether there is a steering system fault in the steering system 1. For this purpose, the steering system operating voltage level U.sub.B is detected as a steering system parameter by means of a diagnostic sensor system (not shown) and transmitted to the diagnostic module 25. The diagnostic module 25 compares the steering system operating voltage level U.sub.B to a predefined steering system target operating voltage level U.sub.SOLL and generates a warning signal S.sub.W if there is a steering system fault, in which the steering system operating voltage level U.sub.B falls below the steering system target operating voltage level U.sub.SOLL. The warning signal S.sub.W is output to the hand actuator 9, which, based on the warning signal S.sub.W, generates the warning feedback R3 in the form of a steering wheel vibration on the steering wheel 5.

[0029] However, the steering feedback R1, the lane feedback R2, and the warning feedback R3 are partially superimposed, so that it can be assumed that the driver does not reliably perceive the warning feedback R3 in every driving state.

[0030] In a departure from the prior art and thus from the control unit 11 of FIG. 3, an evaluation unit 27 and a signal processing unit 29 are therefore additionally associated with the control unit 11 of FIG. 2, by means of which the roadway feedback R2 can be weakened or deactivated in the event of a steering system fault. By deactivating the roadway feedback R2 or by weakening the roadway feedback R2 in comparison to normal steering system operation without a steering system fault, there is no or only a slight overlap between the roadway feedback R2 and the warning feedback R3, so that the perceptibility of the warning feedback R3 is increased.

[0031] The evaluation unit 27 is in signal connection on the signal input side with the diagnostic module 25 and on the signal output side with the signal processing unit 29. The signal processing unit 29 is integrated into a signal path between the roadway converter module 23 and the hand actuator 9 and is interconnected between the roadway converter module 23 and the hand actuator. In the event of a steering system fault, i.e., when the warning signal S.sub.W is transmitted to the evaluation unit 27, the signal processing unit 29 is activated by the evaluation unit 27 in such a way that the signal transmission of the roadway signal S.sub.F is blocked in the signal processing unit 29 or instead a modified roadway signal S.sub.F′ is generated, by means of which a weakened roadway feedback R2 is applied to the steering wheel 5. The weakened roadway feedback R2 has a reduced amplitude level and a reduced frequency in comparison to the roadway feedback R2 in normal steering system operation.

LIST OF REFERENCE SIGNS:

[0032] 1 steer-by-wire steering system

[0033] 3 vehicle

[0034] 5 steering wheel

[0035] 7 steering sensor

[0036] 9 hand actuator

[0037] 11 control unit

[0038] 13 steering gear actuator

[0039] 15 steering gear sensor system

[0040] 17 steering gear

[0041] 19 front wheel

[0042] 21 steering converter module

[0043] 23 roadway converter module

[0044] 25 diagnostic module

[0045] 27 analysis unit

[0046] 29 signal processing unit

[0047] F.sub.R restoring force

[0048] S.sub.F roadway signal

[0049] S.sub.F′ modified roadway signal

[0050] S.sub.L steering counter torque signal

[0051] S.sub.W warning signal

[0052] R1 steering feedback

[0053] R2 roadway feedback

[0054] R3 warning feedback

[0055] U.sub.B steering system operating voltage level

[0056] U.sub.SOLL steering system target operating voltage level

[0057] α vehicle wheel steering angle