Method for operating steering system, control unit for carrying out such method, steering system having such control unit, and motor vehicle having such steering system

Abstract

The invention relates to a method for operating a steering device (3) having at least one steering column (5) with an actuatable steering handle (7), a steering column sensor (9) associated with the steering column (5), an actuatable drive (11) and a displaceable rack (13), the rack (13) is or can be connected to at least one steerable wheel (17) of the motor vehicle (1) for steering the motor vehicle,-a drive parameter value (21) is determined on the basis of a predefined motor vehicle trajectory (29),-a steering column parameter value (19) is determined on the basis of a signal of the steering column sensor (9), a displacement speed (23) of the rack (13) is determined on the basis of the drive parameter value (21), the steering column parameter value (19) and a predeterminable speed threshold value (25), a first displacement speed (23.1) of the rack (13) and a first steering column parameter value (19.1) are detected at a first point in time, the first displacement speed (23.1) and the first steering column parameter value (19.1) are compared with each other, and the first displacement speed (23.1) and the first steering column parameter value (19.1) are determined at a second point in time. And changing or setting the predefinable speed threshold value (25) within a predetermined time period after the first time point on the basis of the comparison (27).

Description

Technical Field

[0001] The present invention relates to a method for operating a steering system having at least one steering column with an operable steering handle, a steering column sensor associated with the steering column, a controllable drive, and a displaceable rack. The rack is connected or connectable to at least one steerable wheel of a motor vehicle for steering the vehicle. Furthermore, both the steering column and the drive can be operatively connected to the rack for displacing the rack.

[0002] Furthermore, the present invention relates to a control unit for carrying out such a method, a steering system having such a control unit, and a motor vehicle having such a steering system. Background Art

[0003] It is known to use steering systems with controllable drive units in motor vehicles. In known steering systems, the motor torque of the drive unit and / or the force transmitted by the drive unit to the rack are limited in order to ensure the controllability of the motor vehicle in the event of a fault. Summary of the Invention

[0004] In driving situations where the driver does not have his hands on the steering wheel or only has a light grip on it, the steering system drive can cause oscillations in the signal of the steering column sensor. This is due to coordinated rotational fluctuations of the steering column and steering handle.

[0005] The method having the features of claim 1 has the advantage of limiting the displacement speed of the gear rack without the driver actively attempting to turn the steering column and steering handle. Advantageously, if the driver does not place their hands on the steering handle or only gently grips it within a predetermined time period, control of the vehicle is guaranteed within the predetermined time period. Furthermore, the method advantageously enables driver intervention detection. Drive parameter values ​​are determined based on a predetermined vehicle trajectory, and steering column parameter values ​​are determined based on signals from a steering column sensor. Furthermore, the displacement speed of the gear rack is determined based on the drive parameter values, the steering column parameter values, and a predefinable speed threshold. A first displacement speed of the gear rack and a first steering column parameter value are detected at a first time point. The first displacement speed and the first steering column parameter value are compared with each other, and based on the comparison, the predefinable speed threshold is changed or set within a predetermined time period after the first time point. In particular, the method is used to monitor the displacement speed of the gear rack.

[0006] In the context of this technical teaching, the setting of a value, in particular a predeterminable speed threshold value, includes the predetermining of an absolute value. In addition, the change of a value, in particular a predeterminable speed threshold value, includes the predetermining of an absolute value, the predetermining of a change value, and the cancellation of a value.

[0007] In the context of the present technical teaching, in particular, rotation of the steering column in a first rotational direction causes a displacement of the rack in a first translational direction, wherein the steering column parameter value has a positive sign. Furthermore, rotation of the steering column in a second rotational direction, which is opposite to the first rotational direction, causes a displacement of the rack in a second translational direction, which is opposite to the first translational direction, wherein the steering column parameter value has a negative sign. In particular, rotation of the steering column, in particular torsion, is detected by means of a steering column sensor. The steering column parameter value is preferably generated based on the detected rotation.

[0008] It is particularly preferred to provide that the predetermined time period is determined based on the fluctuation duration of the rotation fluctuation of the steering column. In particular, if the rack is displaced and the driver does not have his hands on the steering handle, the displacement of the rack will cause a rotation of the steering column and in particular a rotation fluctuation of the steering column. In particular, such a rotation fluctuation may cause the displacement speed and the steering column parameter value to have not only the same sign but also different signs during the fluctuation duration of the rotation fluctuation. In particular, if the signs are the same during the fluctuation duration, a driver intervention will be erroneously identified. In this way, an erroneous identification of a driver intervention is prevented in an advantageous manner. In particular, the fluctuation duration of the rotation fluctuation of the steering column T Depends on the first moment of inertia J1 of the steering column and the second moment of inertia J2 of the steering handle as well as the rotational stiffness D of the steering column and the steering column sensor r Furthermore, it is preferred that according to the equation: To calculate the duration of the fluctuation T Furthermore, friction and damping effects in particular lead to a reduction in the amplitude of the rotational fluctuations over time.

[0009] Particularly preferably, the first displacement speed and the first steering column parameter value are compared with each other only when the first displacement speed is greater than the limit speed. Advantageously, the predefinable speed threshold value is not changed or set at low displacement speeds, and in particular, at small changes in the displacement speed. In particular, the maximum permissible displacement speed of the gear rack is used as the predefinable speed threshold value.

[0010] According to a preferred development of the invention, if the first displacement speed and the first steering column parameter value have the same sign, a predefinable speed threshold value is increased or eliminated within a predetermined time period. This advantageously ensures that a second displacement speed that is greater than the first displacement speed can be selected.

[0011] In the context of the present technical teaching, in particular if the rack is displaced in the first translation direction, the displacement speed has a positive sign. Furthermore, if the rack is displaced in the second translation direction, the displacement speed has a negative sign.

[0012] If the steering column parameter value, in particular the first steering column parameter value, and the displacement speed, in particular the first displacement speed, have the same sign, it can be inferred that the steering system, in particular the steering handle, is being actively operated by the driver and is actively oversteering. This advantageously enables driver intervention detection. Therefore, a predefinable speed threshold is advantageously increased or eliminated in order to allow active oversteering by the driver.

[0013] If the steering column parameter value, in particular the first steering column parameter value, and the displacement velocity, in particular the first displacement velocity, have different signs, it can be inferred that the steering system, in particular the steering handle, is not being actively operated by the driver. Specifically, if the driver is not actively operating the steering system, in particular the steering handle, the steering column rotates, in particular twists, via the rack when the rack is displaced, thereby generating the steering column parameter value. However, when the rack is displaced in the first translational direction, the steering column rotates in the second rotational direction. Additionally, when the rack is displaced in the second translational direction, the steering column rotates in the first rotational direction. Therefore, when the steering column is not actively rotated by the driver, the displacement velocity, in particular the first displacement velocity, and the steering column parameter value, in particular the first steering column parameter value, have different signs. This advantageously indicates that the driver is not resting their hands on the steering handle or is only gripping it lightly. In the event of an erroneous recognition of driver intervention, a predefinable speed threshold value could be disadvantageously increased or eliminated, which could result in the vehicle no longer being controllable by the driver.

[0014] According to a preferred refinement of the present invention, the predetermined time period comprises a first time interval with a first maximum duration. Furthermore, if the first displacement velocity and the first steering column parameter value have different signs, the first time interval begins at a first point in time, and during the first time interval, a predefinable velocity threshold value is maintained, increased, or eliminated. In particular, the first maximum duration is the length of half the duration of a rotational fluctuation of the steering column. In particular, the displacement velocity and the steering column parameter value are compared during the first time interval, preferably multiple times, particularly preferably at regular time intervals.

[0015] Particularly preferably, the predetermined time period additionally includes a second time interval with a second maximum duration. Furthermore, it is provided that if the first displacement velocity and the first steering column parameter value have the same sign during the first time interval, the first time interval is prematurely ended and the second time interval is started, and that the predefinable speed threshold value is maintained or, in particular, not changed, during the second time interval. In particular, the second maximum duration is the length of half the duration of the steering column rotational fluctuation. In particular, if the first displacement velocity and the first steering column parameter value have the same sign when compared, in particular multiple times, during the first time interval, the first time interval is prematurely ended and the second time interval is started. This advantageously allows for the detection of rotational fluctuations of the steering system, in particular the steering handle, and prevents erroneous detection of driver intervention and the associated erroneous increase or cancellation of the predefinable speed threshold value.

[0016] According to a further development of the invention, the second time interval is only started if the first time interval has expired prematurely after a predetermined minimum duration. This advantageously prevents the second time interval from being incorrectly started in the event of brief fluctuations in the first displacement speed and / or the first steering column parameter value, and a desired driver intervention not being detected.

[0017] The control unit according to the invention having the features of claim 8 is designed specifically to carry out the method according to the invention when used in accordance with the intended purpose. In conjunction with the control unit, the advantages already explained in conjunction with the method for operating a steering system are achieved in particular.

[0018] A steering system having the features of claim 9 comprises a steering column with an operable steering handle, a steering column sensor associated with the steering column, a controllable drive, a toothed rack, and a controller according to the present invention. The toothed rack is connected or connectable to at least one steerable wheel of a motor vehicle for steering the motor vehicle. Furthermore, both the steering column and the drive are operatively connected to the toothed rack for displacement of the toothed rack. In conjunction with the steering system, the advantages already explained in conjunction with the method and the controller for operating the steering system are achieved.

[0019] The motor vehicle according to the invention has a steering system according to the invention having the features of claim 10. In connection with the motor vehicle, in particular, the advantages already explained in connection with the method for operating a steering system, the control unit, and the steering system result. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Further advantages and preferred features and feature combinations are particularly apparent from the preceding description and from the claims. The invention will now be explained in more detail with reference to the accompanying drawings. Figure 1shows a schematic diagram of an embodiment of a motor vehicle according to the invention, Figure 2 A flow chart of a first exemplary embodiment of a method for operating a steering device is shown, and Figure 3 A flow chart of a second exemplary embodiment of a method for operating a steering device is shown. DETAILED DESCRIPTION

[0021] Figure 1 A schematic diagram of an embodiment of a motor vehicle 1 having a steering device 3 is shown. The steering device 3 has a steering column 5 with a controllable steering handle 7, a steering column sensor 9 assigned to the steering column 5, a controllable drive 11, a rack 13 and a controller 15. The rack 13 is connected or can be connected to at least one steerable wheel 17 of the motor vehicle 1 for steering the motor vehicle. In addition, not only the steering column 5 but also the drive 11 are operatively connected to the rack 13 for displacement of the rack. In addition, the steering column sensor 9 is configured to detect a steering column parameter value 19. In addition, the controller 15 is operatively connected to the steering column sensor 9, the drive 11 and the rack 13 in a manner not explicitly shown and is configured for their corresponding control. In addition, the controller 15 is specifically configured to implement a method for operating the steering device 3 when used in accordance with the regulations. Figure 2 and Figure 3 Preferred embodiments of the method are explained in more detail in .

[0022] Figure 2 A flow chart of a first exemplary embodiment of a method for operating a steering device 3 is shown.

[0023] Identical and functionally identical elements are provided with the same reference symbols in all figures, so that reference is made to the preceding description in this respect.

[0024] In a first step S1, a drive parameter value 21 is determined based on a predetermined vehicle trajectory 29, and a steering column parameter value 19 is determined based on the signal of the steering column sensor 9. In one embodiment, the drive motor torque is used as the drive parameter value. Alternatively or additionally, the drive force acting on the gear rack is used as the drive parameter value.

[0025] In a second step S2 , a displacement speed 23 of the toothed rack 13 is determined as a function of the drive parameter value 21 , the steering column parameter value 19 and a predefinable speed threshold value 25 .

[0026] In a third step S3 , a first displacement speed 23 . 1 of the gear rack 13 and a first steering column parameter value 19 . 1 are detected at a first point in time.

[0027] In a fourth step S4 , the first displacement speed 23 . 1 and the first steering column parameter value 19 . 1 are compared with one another, resulting in a comparison 27 .

[0028] In a fifth step S5, the predefinable speed threshold value 25 is changed or set within a predetermined time period after the first time point based on the comparison 27. The predetermined time period is preferably determined based on the fluctuation duration of the rotation fluctuation of the steering column 5. Particularly preferably, the predetermined time period corresponds to the fluctuation duration of the rotation fluctuation of the steering column 5. T . In particular, by means of the equation: To determine the duration of the fluctuation T , wherein J1 represents the first moment of inertia of the steering column 5, J2 represents the second moment of inertia of the steering handle 7, and D r Indicates the rotational stiffness of the steering column and steering column sensor.

[0029] Figure 3 A flow chart of a second exemplary embodiment of a method for operating a steering device 3 is shown.

[0030] In a first step S1, a drive parameter value 21 is determined based on a predetermined vehicle trajectory 29, and a steering column parameter value 19 is determined based on the signal of the steering column sensor 9. In one embodiment, the drive motor torque is used as the drive parameter value. Alternatively or additionally, the drive force acting on the gear rack is used as the drive parameter value.

[0031] In a second step S2 , a displacement speed 23 of the toothed rack 13 is determined as a function of the drive parameter value 21 , the steering column parameter value 19 and a predefinable speed threshold value 25 .

[0032] In a third step S3 , a first displacement speed 23 . 1 of the gear rack 13 and a first steering column parameter value 19 . 1 are detected at a first point in time.

[0033] In a sixth step S6 , the first displacement speed 23 . 1 of the toothed rack 13 is compared with the limit speed 31 .

[0034] If the first displacement speed 23 . 1 is less than or equal to the limit speed 31 , the method is ended and / or restarted with the first step S1 .

[0035] If the first displacement speed 23 . 1 is greater than the limit speed 31 , then in a fourth step S4 the first displacement speed 23 . 1 and the first steering column parameter value 19 . 1 are compared with one another, resulting in a comparison 27 .

[0036] In the fifth step S5, similar to Figure 2As a function of the comparison 27 , a predefinable speed threshold value 25 is changed or set within a predetermined time period.

[0037] Figure 4 A flow chart of a third exemplary embodiment of a method for operating a steering device 3 is shown.

[0038] In a first step S1, a drive parameter value 21 is determined based on a predetermined vehicle trajectory 29, and a steering column parameter value 19 is determined based on the signal of the steering column sensor 9. In one embodiment, the drive motor torque is used as the drive parameter value. Alternatively or additionally, the drive force acting on the gear rack is used as the drive parameter value.

[0039] In a second step S2 , a displacement speed 23 of the toothed rack 13 is determined as a function of the drive parameter value 21 , the steering column parameter value 19 and a predefinable speed threshold value 25 .

[0040] In a third step S3 , a first displacement speed 23 . 1 of the gear rack 13 and a first steering column parameter value 19 . 1 are detected at a first point in time.

[0041] In a sixth step S6 , the first displacement speed 23 . 1 of the toothed rack 13 is compared with the limit speed 31 .

[0042] If the first displacement speed 23 . 1 is less than or equal to the limit speed 31 , the method is ended and / or restarted with the first step S1 .

[0043] If the first displacement speed 23 . 1 is greater than the limit speed 31 , then in a seventh step S7 , the signs of the first displacement speed 23 . 1 and the first steering column parameter value 19 . 1 are compared with one another.

[0044] If the first displacement speed 23 . 1 and the first steering column parameter value 19 . 1 have the same sign, in an eighth step S8 the predefinable speed threshold 25 is increased or reduced within a predetermined time period so that a displacement speed 23 greater than the first displacement speed 23 . 1 can be selected.

[0045] If the first displacement velocity 23.1 and the first steering column parameter value 19.1 have different signs, a first time interval of a predetermined time period of a first maximum duration is initiated in a ninth step S9. During the first time interval, the speed threshold value 25 is maintained, increased, or eliminated. Specifically, the first maximum duration is equal to the duration of half the rotational fluctuation of the steering column 5. Specifically, the displacement velocity 23 and the steering column parameter value 19 are compared during the first time interval, preferably multiple times, particularly preferably at regular intervals. If the first displacement velocity 23.1 and the first steering column parameter value 19.1 have the same sign during the first time interval, the first time interval is prematurely terminated. If the first time interval ends after the first maximum duration, the method is terminated and / or restarted with the first step S1. If the first time interval ends prematurely, a second time interval of a predetermined time period of a second maximum duration is initiated. During the second time interval, the predeterminable speed threshold value 25 is maintained or not changed. Specifically, the first maximum duration is equal to the duration of half the rotational fluctuation of the steering column 5. Particularly preferably, the second time interval is initiated only if the first time interval ends prematurely after a predetermined minimum duration.

Claims

1. A method for operating a steering device (3), comprising at least one steering column (5) with an actuable steering handle (7), a steering column sensor (9) assigned to the steering column (5), a controllable drive (11) and a displaceable rack (13), wherein: The rack (13) is connected or connectable to at least one steerable wheel (17) of the motor vehicle (1) for steering the motor vehicle, wherein: - determining a drive parameter value (21) based on a predetermined vehicle trajectory (29), wherein: - determining a steering column parameter value (19) based on the signal of the steering column sensor (9), wherein - determining the displacement speed (23) of the toothed rack (13) as a function of the drive parameter value (21), the steering column parameter value (19) and a predeterminable speed threshold value (25), wherein: - detecting a first displacement speed (23.1) of the rack (13) and a first steering column parameter value (19.1) at a first point in time, wherein: - comparing the first displacement speed (23.1) and the first steering column parameter value (19.1) with one another, and wherein, - changing or setting the predefinable speed threshold value (25) within a predetermined time period after the first point in time as a function of the comparison (27).

2. The method according to claim 1, characterized in that The predetermined time period is determined according to a fluctuation duration of the rotation fluctuation of the steering column (5).

3. The method according to any one of the preceding claims, characterized in that The first displacement speed (23.1) and the first steering column parameter value (19.1) are compared with each other only when the first displacement speed (23.1) is greater than a limit speed (31).

4. The method according to any one of the preceding claims, characterized in that If the first displacement speed (23.1) and the first steering column parameter value (19.1) have the same sign, the predeterminable speed threshold value (25) is increased or cancelled within the predetermined time period, so that a second displacement speed (23) greater than the first displacement speed (23.1) can be selected.

5. The method according to any one of the preceding claims, characterized in that The predetermined time period has a first time interval with a first maximum duration, the first time interval starting at the first time point if the first displacement speed (23.1) and the first steering column parameter value (19.1) have different signs, and the predeterminable speed threshold value (25) is maintained, increased or eliminated during the first time interval.

6. The method according to claim 5, characterized in that The predetermined time period additionally comprises a second time interval with a second maximum duration, the first time interval being prematurely ended and the second time interval being started if the first displacement speed (23.1) and the first steering column parameter value (19.1) have the same sign during the first time interval, and the predeterminable speed threshold value (25) is maintained during the second time interval.

7. The method according to claim 6, characterized in that The second time interval is only started if the first time interval ends prematurely after a predetermined minimum duration.

8. A control unit (15) which is specially designed to carry out the method according to any one of the preceding claims when used in accordance with the intended use.

9. A steering device (3) comprising: - a steering column (5) with a maneuverable steering handle (7); - a steering column sensor (9) assigned to the steering column (5); - a controllable drive device (11); - a rack (13), wherein The rack (13) is connected or connectable to at least one steerable wheel (17) of the motor vehicle (1) for steering the motor vehicle; and - A controller (15) according to claim 8.

10. A motor vehicle (1) having a steering device (3) according to claim 9.

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