DETERMINING A STEERING REFERENCE STATE BY MEANS OF WHEEL SPEED VALUES

Abstract

A control unit and a method for determining a steering reference state for a vehicle. A first wheel speed value that is a wheel speed value for a wheel on the vehicle is obtained. At least one second wheel speed value that is a wheel speed value for another wheel on the vehicle is obtained. Using the first and second wheel speed value, a steering reference state is determined, corresponding to travel in a straight line by the vehicle.

Claims

1-9. (canceled)

10. A method for determining a steering reference state for a vehicle, comprising: obtaining, via a control unit, a first wheel speed value that is based on a wheel speed of a wheel on the vehicle; obtaining, via the control unit, at least one second wheel speed value based on a second wheel speed for another wheel on the vehicle; determining, via the control unit, whether a steering reference state exists that corresponds to travel in a straight line by the vehicle on the basis of the first and second wheel speed values; and transmitting a control signal if the steering reference state is determined to exist.

11. The method of claim 10, wherein determining the steering reference state exists comprises determining that a difference between the first and second wheel speed values is less than a predetermined threshold value.

12. The method of claim 10, further comprising determining an angle correction value on the basis of a current steering angle when the steering reference state is determined.

13. The method of claim 10, further comprising storing a current steering as the reference steering angle when the steering reference state is determined.

14. The method of claim 10, further comprising processing the steering reference state to determine plausibility on the basis of at least one state value for the vehicle.

15. The method of claim 10, wherein the state value comprises a yaw rate

16. The method of claim 10, wherein the first and second wheel speed values each indicate a wheel rotational rate for each respective wheel assigned thereto.

17. A system for determining a steering reference state for a vehicle, comprising: a first wheel sensor; a second wheel sensor; and a control unit, wherein the control unit is configured to obtain a first wheel speed value from the first wheel sensor that is based on a wheel speed of a wheel on the vehicle; obtain a second wheel speed value from the second wheel sensor based on a second wheel speed for another wheel on the vehicle; determine, whether a steering reference state exists that corresponds to travel in a straight line by the vehicle on the basis of the first and second wheel speed values; and transmit a control signal if the steering reference state is determined to exist.

18. The system of claim 17, wherein the control unit is configured to determine the steering reference state exists by determining that a difference between the first and second wheel speed values is less than a predetermined threshold value.

19. The system of claim 17, wherein the control unit is configured to determine an angle correction value on the basis of a current steering angle when the steering reference state is determined.

20. The system of claim 17, wherein the control unit is configured to store a current steering as the reference steering angle when the steering reference state is determined.

21. The system of claim 17, wherein the control unit is configured to process the steering reference state to determine plausibility on the basis of at least one state value for the vehicle.

22. The system of claim 17, wherein the state value comprises a yaw rate

23. The system of claim 17, wherein the first and second wheel speed values each indicate a wheel rotational rate for each respective wheel assigned thereto.

24. A method for determining a steering reference state for a vehicle, comprising: obtaining, via a control unit, a first wheel speed value that is based on a wheel speed of a wheel on the vehicle; obtaining, via the control unit, at least one second wheel speed value based on a second wheel speed for another wheel on the vehicle; determining, via the control unit, a steering reference state comprising a yaw rate that corresponds to travel in a straight line by the vehicle on the basis of the first and second wheel speed values; and transmitting a control signal if the steering reference state is determined to exist.

25. The method of claim 24, wherein determining the steering reference state exists comprises determining that a difference between the first and second wheel speed values is less than a predetermined threshold value.

26. The method of claim 24, further comprising determining an angle correction value on the basis of a current steering angle when the steering reference state is determined.

27. The method of claim 24, further comprising storing a current steering as the reference steering angle when the steering reference state is determined.

28. The method of claim 24, further comprising processing the steering reference state to determine plausibility on the basis of at least one state value for the vehicle.

29. The method of claim 24, wherein the first and second wheel speed values each indicate a wheel rotational rate for each respective wheel assigned thereto.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Exemplary embodiments of the present disclosure shall be explained below on the basis of the attached schematic drawings. Therein:

[0026] FIG. 1 shows a vehicle with a control unit according to a first exemplary embodiment of the present disclosure; and

[0027] FIG. 2 shows a flow chart for a method that is executed by the control unit in FIG. 1.

DETAILED DESCRIPTION

[0028] A vehicle 10 is shown in a simplified schematic top view in FIG. 1. A front axle 12 and rear axle 14 can be seen therein. Each axle 12, 14 has two wheels 16. These wheels 16 are on different sides of the vehicle on each axle, or at opposite ends of the respective axles 12, 14. There is also a steering element 18 in the form of a steering wheel. This is a component of the steering system 20. The steering system 20 comprises a highly schematically simplified steering gear 22. This can be designed according to the prior art, and comprise, e.g., a gear rack (not shown separately). A currently set steering angle of the steering system 20 can be determined with a steering angle measurement system 24. This can take place by determining a position of the gear rack in the manner known per se.

[0029] Wheel rotational rate sensors 26 are also shown on each of the wheels 16 on the front axle 12. In this example, only the front axle 12 can be steered, but not the rear axle 14.

[0030] The wheel rotational rate sensors 26 determine the wheel rotational rates in the form of the wheel speed values for each of the wheels 16 to which they are dedicated. The wheel rotational rate sensors 26 are connected to a communication bus 28, as is the steering angle measurement system 24 as well. A control unit 30 is also connected thereto, which is an ESC control unit in this example.

[0031] The ESC control unit obtains the wheel rotational rates from the two-wheel rotational rate sensors 26, as well as, preferably, a current steering angle measured by the steering angle measurement system 24.

[0032] The control unit 30 comprises a processor 32 and a memory 34. Information regarding an output, reference, or target steering angle can be stored in the memory 34, which corresponds to an assumed travel in a straight line by the vehicle 10. Due to the aforementioned asymmetry of the steering system 20 and any disruptions occurring when in operation (e.g., wear or deformation of individual links in the steering gear 22), the aforementioned target steering angle may not correspond to actual travel in a straight line by the vehicle 10.

[0033] The steering angle (reference steering angle) is therefore determined in the present case, when the vehicle is travelling in a straight line. The control unit 30 compares the wheel rotational rates obtained from the wheel rotational rate sensors 26 for this. If these rotational rates do not differ by more than a predetermined extent (i.e., the difference between them lies below a predetermined threshold value), it can be assumed that the vehicle is traveling in a straight line.

[0034] Other conditions can also be taken into account, such as concurrence over a longer period of time, or a minimum frequency of a corresponding concurrence that has been established.

[0035] A plausibility check of the aforementioned type can also be made. The plausibility check can also take a yaw rate into account, such that the frequency of the concurrence of the wheel rotational rates reaches a certain minimum value (in particular the absolute frequency), or should exhibit a certain relative relationship if there is not corresponding concurrence in comparison with other vehicle states (corresponding to a relative frequency of the preferably more frequently occurring state of the concurrence of the wheel rotational rates in relation to a significant difference therefrom).

[0036] This is based on the idea that the wheels 16 on the front axle 12 are on either the inside of the curve or the outside when travelling through a curve. These wheel rotational rates thus differ from one another when travelling through a curve (i.e., when not traveling in a straight line and/or during an active steering). When travelling in a straight line, these wheel rotational rates should be substantially the same. The plausibility check based on the aforementioned frequencies assumes that travel in a straight line is more frequent than travelling in a curve.

[0037] If the wheel rotational rates are determined to be the same by the control unit 30 or its processor 32, and, optionally, one of the aforementioned plausibility criteria are also satisfied, the current steering angle determined by the steering angle measurement system 24 can be stored as the reference steering angle in the memory 34. This corresponds to a zero setting for the steering system 20. Alternatively or additionally, the aforementioned angle correction value can be determined and stored as an offset value.

[0038] FIG. 2 shows the aforementioned method in the form of a flow chart. Wheel rotational rates are determined by the wheel rotational rate sensors 26, and output to the control unit 30 in step S1. The control unit then compares the wheel rotational rates in step S2. If these are not sufficiently the same (arrow N in FIG. 2), the method returns to step S1. If they are sufficiently equal (arrow Y in FIG. 2), the steering angle measured at that time by the steering angle measurement system 24 is set as the value for travel in a straight line. In particular, the aforementioned angle correction value is stored on the basis thereof.

[0039] The steering angle measurement system 24 measures another steering angle while the vehicle 10 is being operated in step S4. This is calculated using the angle correction value, in order to obtain an actual, effective, set steering angle, or a steering angle that is offset in relation to actual travel in a straight line.

LIST OF REFERENCE SYMBOLS

[0040] 10 vehicle

[0041] 12 front axle

[0042] 14 rear axle

[0043] 16 wheel

[0044] 18 steering wheel

[0045] 20 steering system

[0046] 22 steering gear

[0047] 24 steering angle measurement system

[0048] 26 wheel rotational rate sensor

[0049] 28 communication bus

[0050] 30 control unit

[0051] 32 processor

[0052] 34 memory