Method for operating a steering system and steering system

1. A method for operating a steering system of a motor vehicle having a power steering system, the method comprising:

introducing an assistance torque into a steering gear;

determining a driving situation;

reducing the assistance torque as a function of the driving situation;

introducing a first assistance torque in each case into the steering gear using a first actuator path and using a second actuator path in a normal operating mode;

determining a failure of the first actuator path;

reducing a second assistance torque in comparison with the first assistance torque; and

introducing the second assistance torque into the steering gear using the second actuator path during the failure of the first actuator path.

2. The method as claimed in claim 1 , further comprising:

determining a safety-critical driving situation; and

deactivating the reduction of the assistance torque as a function of the safety-critical driving situation.

3. The method as claimed in claim 2 , wherein the safety-critical driving situation is one of (i) a planned lane change and (ii) a steering speed exceeding a threshold value.

4. The method as claimed in claim 1 , further comprising:

determining a non-safety-critical driving situation; and

deactivating the reduction of the second assistance torque during the failure of the first actuator path and in the non-safety-critical driving situation.

5. The method as claimed in claim 4 , further comprising:

activating the reduction of the second assistance torque in comparison with the first assistance torque during the failure of the first actuator path in response to at least one of (i) a vehicle speed exceeding a threshold value and (ii) low steering dynamics being present.

6. The method as claimed in claim 4 , wherein the non-safety-critical driving situation is a parking situation.

7. The method as claimed in claim 1 , further comprising:

determining a safety-critical driving situation; and

deactivating the reduction of the second assistance torque during the failure of the first actuator path and in the safety-critical driving situation.

8. The method as claimed in claim 7 , wherein the safety-critical driving situation is one of (i) a planned lane change and (ii) high steering dynamics.

9. A non-transitory computer readable medium configured to store computer program for operating a steering system of a motor vehicle having a power steering system, the computer program being configured to, when executed on a digital computing device:

introduce an assistance torque into a steering gear; determine a driving situation; reduce the assistance torque as a function of the driving situation; introduce a first assistance torque in each case into the steering gear using a first actuator path and using a second actuator path in a normal operating mode; determine a failure of the first actuator path; reduce a second assistance torque in comparison with the first assistance torque; and introduce the second assistance torque into the steering gear using the second actuator path during the failure of the first actuator path.

10. The non-transitory computer readable medium as claimed in claim 9 , wherein the computer program is configured to be executed on a microprocessor of a control device configured to operate the steering system of the motor vehicle.

11. A steering system of a motor vehicle, the steering system comprising:

a power steering system, wherein an assistance torque is can be introduced into a steering gear, wherein a driving situation is determined and the assistance torque is reduced as a function of the driving situation, wherein a first assistance torque is introduced in each case into the steering gear using a first actuator path and using a second actuator path in a normal operating mode, wherein a failure of the first actuator path is determined, wherein a second assistance torque is reduced in comparison with the first assistance torque, and wherein the second assistance torque is introduced into the steering gear using the second actuator path during the failure of the first actuator path.

12. The steering system as claimed in claim 11 , further comprising:

a control device configured to:

introduce the assistance torque into the steering gear;

determine the driving situation;

reduce the assistance torque as the function of the driving situation;

introduce the first assistance torque in each case into the steering gear using the first actuator path and using the second actuator path in the normal operating mode;

determine the failure of the first actuator path;

reduce the second assistance torque in comparison with the first assistance torque; and

introduce the second assistance torque into the steering gear using the second actuator path during the failure of the first actuator path.