Method for determining a roadway condition and vehicle having at least two wheel-selective steering actuators

Abstract

A method determines a roadway condition using steering actuators, wherein at least two steering actuators are arranged on each vehicle wheel. Measurement variables of the first and second steering actuators are sensed. The sensed measurement variables of the two steering actuators are compared with one another and, an inhomogeneity signal is determined from the deviation between the sensed measurement variables of the two steering actuators. If the inhomogeneity signal lies within a tolerance range, a homogeneous roadway condition exists. If the inhomogeneity signal lies outside the tolerance range, an inhomogeneous roadway condition exists.

Claims

1. A method for determining a roadway condition by means of steering actuators, wherein first and second steering actuators are arranged on respective vehicle wheels assigned to a same vehicle axle, the method comprising: sensing a measurement variable of the first steering actuator; sensing a measurement variable of the second steering actuator; comparing the sensed measurement variables of the two steering actuators; determining an inhomogeneity signal from the deviation between the sensed measurement variables of the two steering actuators, wherein an inhomogeneity signal value within a tolerance range represents a homogeneous roadway condition and an inhomogeneity signal value outside the tolerance range represents an inhomogeneous roadway condition.

2. The method according to claim 1, wherein the first and second steering actuators each comprises an electric motor and a mechanical transmission element, and wherein the measurement variable is sensed on the electric motor.

3. The method according to claim 1, wherein the measurement variable is sensed as an actuating torque or an electrical current.

4. The method according to claim 1, wherein the measurement variable is determined by means of a measuring device associated with the steering actuator.

5. The method according to claim 2, wherein the electric motor of the steering actuator is connected to a control unit.

6. The method according to claim 1, further comprising using the determined inhomogeneity signal in a vehicle control system to stabilize the vehicle wheels and thus a vehicle.

7. The method according to claim 6, wherein the determined inhomogeneity signal is used to determine a target drive torque, wherein the target drive torque is impressed upon at least one of the vehicle wheels by the vehicle control system.

8. The method according to claim 1, wherein the method is used in a wheel-selective vehicle steering system.

9. The method according to claim 8, wherein the wheel-selective vehicle steering system is a steer-by-wire system.

10. A vehicle having at least two vehicle wheels which are arranged on a same axle, wherein a steering actuator is arranged on each of the two vehicle wheels, and having a control unit which is coupled to the steering actuators, wherein the control unit is programmed to carry out a method for determining a roadway condition according to claim 1.

11. The method according to claim 6, wherein the determined inhomogeneity signal is used to determine a braking torque, wherein the braking torque is impressed upon at least one of the vehicle wheels by the vehicle control system.

12. The method according to claim 6, wherein the determined inhomogeneity signal is used to determine a target steering intervention, wherein the target steering intervention is impressed upon at least one of the vehicle wheels by the vehicle control system.

13. A vehicle comprising: first and second wheels; first and second steering actuators configured to steer the first and second wheels respectively; and a vehicle control system configured to sense a measurement variable on each of the first and second actuators, compare the measurement variables, and apply a stabilizing action to at least one of the two wheels in response to a difference between the measurement variables.

14. The vehicle of claim 13, wherein the measurement variable is a steering torque.

15. The vehicle of claim 13, wherein the measurement variable is an electric current.

16. The vehicle of claim 13, wherein the stabilizing action is a drive torque.

17. The vehicle of claim 13, wherein the stabilizing action is a braking torque.

18. The vehicle of claim 13, wherein the stabilizing action is a steering torque.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Further advantages, details, and developments will become apparent from the following description of a preferred embodiment, with reference to the accompanying drawings.

[0030] In the drawings:

[0031] FIG. 1 shows a schematic partial view of a vehicle wheel suspension system with a first embodiment of a wheel-selective steering actuator;

[0032] FIG. 2 shows a schematic partial view of a second embodiment of the wheel-selective steering actuator.

DETAILED DESCRIPTION

[0033] FIG. 1 shows a schematic partial view of a vehicle wheel suspension system with a first embodiment of a wheel-selective steering actuator or a wheel-selective vehicle steering system. The wheel-selective steering actuator can be used in a vehicle and is designed as a linear actuator. The steering actuator is arranged on a vehicle wheel 01 and comprises an electric motor 02, a rack 03 and a pinion 04, which is arranged between the rack 03 and the electric motor 02 and which serves as a connecting element. A control unit 06 is connected to the electric motor 02. The steering actuator is articulated to a reversing lever 07 by means of the rack 03. The reversing lever 07 engages the vehicle wheel 01 so that the steering actuator is connected to the vehicle wheel 01. The vehicle wheel suspension system also has a suspension arm 08, which is arranged on the vehicle wheel 01 and also forms the connection point to a vehicle body (not shown).

[0034] The wheel-selective steering actuator is designed to carry out the method for determining a roadway condition. At least two vehicle wheels 01 are arranged on a common vehicle axle (not shown), wherein a separate wheel-selective steering actuator is arranged on each vehicle wheel 01. The steering actuators are thus arranged on different sides of the vehicle (left, right).

[0035] The method provides that a measurement variable of the first steering actuator is determined in a first step and a measurement variable of the second steering actuator is determined in a further step. The measurement variables are sensed by means of a measuring device (not shown). The measuring device is arranged on the electric motor 02 or integrated thereinto. Alternatively, the measuring device can be arranged on the control unit 06 or integrated thereinto. Furthermore, the measuring device can also be integrated into the chassis. A motor current is sensed. In a further method step, the control unit 06 compares the sensed measurement variables from the two steering actuators. The control unit 06 determines an inhomogeneity signal from the deviation between the measurement variables, wherein an inhomogeneity signal lies within a tolerance range representing a homogeneous roadway condition and an inhomogeneity signal lies outside the tolerance range representing an inhomogeneous roadway condition. The determined inhomogeneity signal can be used to generate a compensation torque, for example a target drive torque and/or a braking torque and/or a target steering intervention, which can be used as an input variable in a vehicle control system or an assistance system. For example, a steering angle is set. The steering torque is determined using the sensed motor current as the measurement variable from the steering actuator. The steering torque can be calculated from the lateral force acting on the vehicle wheel 01 and the assigned lever arm by multiplication, wherein the lever arm is obtained from the addition of a tire caster with a structural caster. There is a functionally clear relationship between the motor current and the actuating force of the steering actuator.

[0036] FIG. 2 shows a schematic partial view of a second embodiment of the wheel-selective steering actuator. The wheel-selective steering actuator shown in FIG. 2 has the electric motor 02 or a modified electric motor with a transmission. The electric motor 02 is indirectly rotatably mounted on a roller bearing 09. The steering actuator also comprises the control unit 06, which is electrically connected to the electric motor 02. The electric motor 02 is mechanically and/or electrically coupled to the vehicle wheel 01 by means of a vehicle component 11 for setting a steering angle. The wheel-selective steering actuator is designed to carry out the method described in connection with FIG. 1 for determining a roadway condition. The steering torque is determined using the sensed motor current as the measurement variable from the steering actuator. In contrast to the determination of the steering torque described in FIG. 1, the steering torque to be determined in FIG. 2 corresponds to a motor torque. The motor torque can be calculated by multiplying the torque constant by the motor current.

LIST OF REFERENCE SYMBOLS

[0037] 01 Vehicle wheel
02 Electric motor

03 Rack

04 Pinion

[0038] 06 Control unit
07 Reversing lever

08 Suspension arm

[0039] 09 Roller bearing
11 Vehicle component