STEERING ASSEMBLY, VEHICLE AND METHOD FOR DETERMINING A STEERING TORQUE OF A STEERING SYSTEM

Abstract

The disclosure relates to a steering assembly for a drive-by-wire steering system of a vehicle having an input means for inputting a steering command, a steering shaft with a first region and a second region longitudinally spaced apart from the first region, and a sensor system for detecting a steering angle and/or a steering torque on the steering shaft. The sensor system comprises a first angular-position sensor and a second angular-position sensor. The first angular-position sensor is assigned to the first region and the second angular position sensor is assigned to the second region, so that it is possible to determine, by means of a difference of a first angle signal of the first angular-position sensor and a second angle signal of the second angular-position sensor, the steering torque on the steering shaft on which the steering torque is acting.

Claims

1. A steering assembly for a drive-by-wire steering system of a vehicle, the steering assembly comprising, an input means configured for inputting a steering command, a steering shaft having a first region and a second region spaced apart from the first region in a longitudinal direction of the steering shaft, and a sensor system configured for detecting at least one of a steering angle or a steering torque on the steering shaft, the sensor system comprising: a first angular-position sensor assigned to the first region, and a second angular-position sensor assigned to the second region, and wherein a difference of a first angle signal of the first angular-position sensor and a second angle signal of the second angular-position sensor determines a steering torque on the steering shaft.

2. The steering assembly according to claim 1, wherein the first angular-position sensor is assigned to a first measuring channel and the second angular-position sensor is assigned to a second measuring channel, so that redundant acquisition of the steering angle via the first measuring channel and the second measuring channel is possible.

3. The steering assembly according to claim 1, wherein the first angular-position sensor and the second angular-position sensor are galvanically separated from each other.

4. The steering assembly according to claim 1, wherein at least one of the first angular-position sensor or the second angular position sensor is configured as a magnetic sensor.

5. The steering assembly according to claim 1, wherein at least one of the first angular-position sensor or the second angular position sensor is configured as a sensor bearing, so that the respective first and second angular-position sensor receives the steering shaft in a mechanically rotatable manner.

6. A motor vehicle having a steering assembly according to claim 1.

7. A method for determining a steering torque of a drive-by-wire steering system of a vehicle, wherein the drive-by-wire steering system comprises a steering shaft having a first region and a second region, an input means configured for operating the drive-by-wire steering system, a first angular-position sensor assigned to the first region, and a second angular-position sensor assigned to the second region for detecting an angle signal on the steering shaft, the method comprising: measuring a first angle of the first region of the steering shaft via the first angular-position sensor and a second angle of the second region of the steering shaft via the second angular-position sensor, ascertaining a difference between the first angle and the second angle via a controller so that a difference angle is provided, determining the steering torque of the steering shaft via the controller and a mathematical function between the difference angle and the steering torque, the mathematical function corresponding to a mechanical torsional stiffness of the steering shaft.

8. The method according to claim 7, wherein a redundant steering angle is determined via the first angular-position sensor and the second angular-position sensor.

9. The steering assembly according to claim 1, wherein: the first angular-position sensor is arranged on the first region of the steering shaft, and the second angular-position sensor is arranged on the second region of the steering shaft.

10. The steering assembly according to claim 1, wherein at least one of the first angular-position sensor or the second angular-position sensor is configured as an optical sensor.

11. The steering assembly according to claim 1, wherein at least one of the first angular-position sensor or the second angular-position sensor is configured as a sensor bearing, and an inner ring of the sensor bearing is non-rotatably attached to the steering shaft.

12. The steering assembly according to claim 11, wherein the sensor bearing further comprises: an impeller configured to rotate together with the inner ring, and a magnetic sensor configured to detect a rotation of the impeller.

13. The steering assembly according to claim 1, wherein: the first angular-position sensor is configured as a first sensor bearing having a first impeller with a first number of blades, the second angular-position sensor is configured as a second sensor bearing having a second impeller with a second number of blades different than the first number of blades.

14. The steering assembly according to claim 1, further comprising a motor adjoined to the second region of the steering shaft, the motor configured to introduce torque into the steering shaft.

15. A method for determining a steering torque of a drive-by-wire steering system of a vehicle, the method comprising: measuring a first angle of a first region of a steering shaft via a first angular-position sensor, and a second angle of a second region of a steering shaft via a second angular-position sensor, the first region longitudinally spaced from the second region, determining a difference between the first angle and the second angle via a controller so that a difference angle is provided, and determining the steering torque of the steering shaft via the controller and a mathematical function between the difference angle and the steering torque.

16. The method according to claim 15, wherein the mathematical function corresponds to a mechanical torsional stiffness of the steering shaft.

17. The method according to claim 15, wherein the first angle is measured at an upper region of the steering shaft via the first angular-position sensor and the second angle is measured at a lower region of the steering shaft via the second angular-position sensor.

18. The method according to claim 15, wherein at least one of the first angular-position sensor or the second angular-position sensor is configured as a sensor bearing attached to the steering shaft.

19. The method according to claim 15, wherein the sensor bearing further comprises: an impeller configured to rotate together with the steering shaft, and a magnetic sensor configured to detect a rotation of the impeller.

20. The method according to claim 15, wherein the second region of the steering shaft is adjoined with a motor configured to introduce torque into the steering shaft.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The disclosure is explained in more detail below using exemplary embodiments. In the drawings:

[0045] FIG. 1 shows a schematic representation of a steering system in an isometric view;

[0046] FIG. 2 shows a schematic representation of the steering system of FIG. 1 in a side view;

[0047] FIG. 3 shows a schematic representation of a sensor bearing for the steering system in an isometric partial section;

[0048] FIG. 4 shows a diagram with sensor signals from different sensor bearings during a steering movement;

[0049] FIG. 5 shows a flow chart of a method for determining a steering torque; and

[0050] FIG. 6 shows a vehicle with a steering system.

DETAILED DESCRIPTION

[0051] A steering system 101 has a steering wheel 103 and a steering shaft 104 mechanically connected to the steering wheel. The steering shaft 104 is rotatably received in a sensor bearing 121 and a sensor bearing 123. In this regard, the sensor bearing 121 is arranged in an upper region 106 of the steering shaft 104 near the steering wheel 103. The sensor bearing 123 is arranged in a lower region 108 of the steering shaft 104.

[0052] A motor unit 125 adjoins the lower region 108 of the steering shaft 104, in which motor unit the steering shaft 104 is connected. By means of the motor unit 125, torque can be introduced in the steering shaft 104 and thus also in the steering wheel 103, so that steering forces can be simulated to an operator of the steering wheel 103.

[0053] The sensor bearing 121 as well as the sensor bearing 123 have both means for rotatably receiving the steering shaft 104 and means for measuring an angle of rotation. The structure of a sensor bearing is explained in more detail using the example of sensor bearing 121:

[0054] An impeller 307 is arranged within a housing 301 of the sensor bearing 121 and is mechanically connected to a rotatable inner ring 310. A magnetic sensor 305 is arranged within an end face 303 on an outer ring 304.

[0055] In this regard, the outer ring 304 is connected in a fixed manner to a surrounding assembly of the steering system 101, and the inner ring 310 non-rotatably receives the steering shaft 104.

[0056] By means of the magnetic sensor 305, the rotational movement of the impeller 307 can be detected in that a measurement signal of the magnetic sensor 305 is changed by the impeller 307. Thus, the magnetic sensor 305 can be used to detect a rotation of the inner ring 310 and thus of the steering shaft 104. The inner ring 310 is arranged on the steering shaft 104 in a non-rotatable manner. Analogously, an inner ring of the sensor bearing 123 is also arranged on the steering shaft 104 in a non-rotatable manner.

[0057] A sealing disc 309 is arranged opposite the impeller 307 and protects the sensor bearing 121 against the ingress of dust. Balls 311 are arranged in a groove 312 such that the inner ring 310 is rotatably guided relative to the outer ring 304 according to the principle of a deep groove ball bearing. In this regard, the balls 311 are held at an appropriate distance by a bearing cage 313. Grease contained in the sensor bearing 121 for lubricating the balls 311 is also protected and retained by the sealing disc 309. The sensor bearing 123 is constructed analogously, but with an impeller having a different number of blades compared to the impeller of the sensor bearing 121. This realizes the different angular resolution between the sensor bearing 121 and the sensor bearing 123.

[0058] Now, when an operator turns the steering wheel 103, for example in a vehicle 601, to give a steering input or steering command, the steering shaft 104 is twisted against a torque applied by the motor unit 125. Thus, the inner ring of the sensor bearing 121 and the sensor bearing 123 are twisted against one another to different extents. This results in a differential signal by means of which the steering torque on the steering wheel 103 can be determined in a control unit (not shown) by means of the torsional stiffness of the steering shaft 104. For this purpose, the torsional stiffness of the steering shaft 104 and a corresponding distance 109 of the first sensor bearing 121 with respect to the second sensor bearing 123 are taken into account.

[0059] A vehicle 601 is equipped with the steering system 101. This allows the steering torque to be determined while the vehicle 601 is in motion. In this regard, the steering system 101 is connected to further safety systems of the vehicle 601 (not shown). This also allows the steering angle to be ascertained redundantly by means of the sensor bearing 121 and the sensor bearing 123.

[0060] A diagram 401 shows corresponding signals of the sensor bearings 121 as well as 123 in an exemplary manner. The diagram 401 comprises a time axis 403 and a signal axis 405 (shown qualitatively). A sensor signal 421 corresponds to the signal of the magnetic sensor 305 within the sensor bearing 121, and a sensor signal 423 analogously corresponds to a signal of a magnetic sensor within the sensor bearing 123. The torsion of the steering shaft 104 and the resulting different angles on the sensor bearing 121 relative to the sensor bearing 123 then result in a time shift 414 between the respective sensor signals 421 and 423, which directly allows a conclusion to be drawn in regard to the currently applied steering torque on the steering wheel 103 and the steering shaft 104.

[0061] The sequence of a corresponding measurement method for determining a steering torque of a steering system is explained here once again:

[0062] Initially, a first angle signal, for example the angle signal of the sensor bearing 121, and a second angle signal, for example the angle signal of the sensor bearing 123, are measured 501, so that a first angular position and a second angular position are provided. Afterwards, a difference is ascertained 503 from these angle signals or angular positions, so that a difference angle can be ascertained. The steering torque is then determined 505 by means of a mathematical relationship between the ascertained difference angle and the length of the distance 109 as well as the stiffness of the steering shaft 104, so that the steering torque is thereby determined. In parallel, the steering angle of the steering system 101 is acquired redundantly by means of the sensor bearing 121 and the sensor bearing 123.

LIST OF REFERENCE SYMBOLS

[0063] 101 Steering system [0064] 103 Steering wheel [0065] 104 Steering shaft [0066] 106 Upper region [0067] 108 Lower region [0068] 109 Distance [0069] 121 Sensor bearing [0070] 123 Sensor bearing [0071] 125 Motor unit [0072] 301 Housing [0073] 303 End face [0074] 304 Outer ring [0075] 305 Magnetic sensor [0076] 307 Impeller [0077] 309 Sealing disc [0078] 310 Inner ring [0079] 311 Ball [0080] 312 Groove [0081] 313 Bearing cage [0082] 401 Diagram [0083] 403 Time axis [0084] 405 Signal axis [0085] 421 Sensor signal [0086] 423 Sensor signal [0087] 414 Time shift [0088] 501 Measuring [0089] 503 Ascertaining [0090] 505 Determining [0091] 601 Vehicle