Limiting a Control Variable for a Motor of an Electric Power Steering System

Abstract

A method limits a control variable for a motor of an electric power steering system for a motor vehicle having automated lateral control. The method receives a setpoint steering angle, determines the control variable in accordance with the setpoint steering angle, receives an actual steering angle, determines a virtual torsion-bar torque in accordance with the setpoint steering angle and the actual steering angle, determines at least one limit value for the control variable in accordance with the virtual torsion-bar torque, and limits the control variable in accordance with the at least one limit value.

Claims

1.-9. (canceled)

10. A method for limiting a control variable for a motor of an electric power steering system for a motor vehicle with automated transverse guidance, the method comprising the steps of: receiving a setpoint steering angle; determining the control variable in accordance with the setpoint steering angle; receiving an actual steering angle; determining a virtual torsion-bar torque in accordance with the setpoint steering angle and the actual steering angle; determining at least one limiting value for the control variable in accordance with the virtual torsion-bar torque; and limiting the control variable in accordance with the at least one limiting value.

11. The method according to claim 10, wherein the control variable is a setpoint torque for the motor.

12. The method according to claim 10, wherein the control variable is a manual torque.

13. The method according to claim 10, wherein the determining of at least one limiting value for the control variable in accordance with the virtual torsion-bar torque comprises the steps of: determining an upper limiting value for the control variable in accordance with the virtual torsion-bar torque; and determining a lower limiting value for the control variable in accordance with the virtual torsion-bar torque.

14. The method according to claim 13, wherein a first upper limiting value and a first lower limiting value are determined for a first control variable, and a second upper limiting value and a second lower limiting value are determined for a second control variable such that the distance between the second upper limiting value and the second lower limiting value corresponds essentially to the distance between the first upper limiting value and the first lower limiting value.

15. The method according to claim 10, wherein the determining of a virtual torsion-bar torque in accordance with the setpoint steering angle and the actual steering angle is performed via a lookup table.

16. The method according to claim 10, wherein a first limiting value is determined for a first virtual torsion-bar torque, and a second limiting value, which is greater than the first limiting value, is determined for a second virtual torsion-bar torque, which is greater than the first virtual torsion-bar torque.

17. The method according to claim 10, wherein the setpoint steering angle is received from a driving system for automated driving with at least automated transverse guidance.

18. An apparatus for limiting a control variable for a motor of an electric power steering system for a motor vehicle with automated transverse guidance, comprising: a control unit configured so as to: receive a setpoint steering angle, determine the control variable in accordance with the setpoint steering angle, receive an actual steering angle, determine a virtual torsion-bar torque in accordance with the setpoint steering angle and the actual steering angle, determine at least one limiting value for the control variable in accordance with the virtual torsion-bar torque, and limit the control variable in accordance with the at least one limiting value.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0032] The single FIGURE 1 shows a method for limiting a control variable M, M′ for a motor EM of an electric power steering system for a motor vehicle with automated transverse guidance.

DETAILED DESCRIPTION OF THE DRAWING

[0033] Referring to FIGURE 1, a method is shown for limiting a control variable M, M′ for a motor EM of an electric power steering system for a motor vehicle with automated transverse guidance. The control variable is in this case, for example, a setpoint torque for the motor EM.

[0034] One step in this case is that of receiving a setpoint steering angle SLW, for example from a driving system FS for automated driving with at least automated transverse guidance.

[0035] A further step is that of determining the control variable M in accordance with the setpoint steering angle SLW. This step may be performed for example by means of a steering angle controller LWR.

[0036] A further step is that of receiving an actual steering angle ILW, for example from the motor EM of the electric power steering system.

[0037] A further step is that of determining a virtual torsion-bar torque in accordance with the setpoint steering angle SLW and the actual steering angle ILW, wherein the determining of the virtual torsion-bar torque is performed in accordance with the setpoint steering angle SLW and the actual steering angle ILW by means of a lookup table LUT.

[0038] A further step is that of determining at least one limiting value G for the control variable M, M′ in accordance with the virtual torsion-bar torque.

[0039] In particular, the determining of at least one limiting value G for the control variable M, M′ in accordance with the virtual torsion-bar torque comprises determining an upper limiting value for the control variable M, M′ in accordance with the virtual torsion-bar torque, and determining a lower limiting value for the control variable M, M′ in accordance with the virtual torsion-bar torque.

[0040] For example, in this case a first upper limiting value and a first lower limiting value are determined for a first control variable M, M′, and a second upper limiting value and a second lower limiting value are determined for a second control variable M, M′ in such a way that the distance between the second upper limiting value and the second lower limiting value corresponds essentially to the distance between the first upper limiting value and the first lower limiting value.

[0041] In particular, for a first and a second virtual torsion-bar torque, which follow one another in time, a first limiting value is determined for the first virtual torsion-bar torque, and a second limiting value, which is greater than the first limiting value, is determined for the second virtual torsion-bar torque, which is greater than the first virtual torsion-bar torque.

[0042] A further step of the method is that of limiting the control variable M, M′ in accordance with the at least one limiting value G.

[0043] The limiting may be performed for example by means of a limiter LM in such a way that the control variable M is passed on unchanged as the control variable M′ if the control variable M lies below the limiting value G. If the control variable M lies above the limiting value G, instead the limiting value G may be passed on as the control variable M′.