Method for operating an electric power assisted steering system for a motor vehicle

1. A method for determining a desired preset value ( Y M SM ) for a motor torque of an electric servomotor in a power assisted steering system for a motor vehicle, the power assisted steering system having a control unit comprising a processor and having a steering column, the method comprising:

determining by the processor a motor torque pilot control component (M VSK ) based at least in part on a torsion bar torque (M DS ) detected at the steering column, the motor torque pilot control component (M VSK ) forming an open-loop controlled portion of said motor torque:

determining by the processor a motor torque closed-loop controller component (M RK ) which forms a closed-loop controlled portion of said motor torque, wherein a closed-loop control variable of said closed-loop controlled portion is said torsion bar torque (M DS );

functionally combining by the processor the two motor torque pilot control components (M VSK ) and the motor torque closed-loop controller component (M RK ); and

determining by the processor the desired preset value ( Y M SM ) for the motor torque (M SM ) of the servomotor (SM) from the functionally combined motor torque pilot control component (M VSK ) and the motor torque closed-loop controller component (M RK ).

2. The method for determining a desired preset value ( Y M SM ) as claimed in claim 1 ,

wherein the motor torque closed-loop controller component (M RK ) is determined by the processor as a function of a closed-loop control difference between the torsion bar torque (M DS ) as said closed-loop control variable and an application torsion bar torque (M DS, Appl ) as a reference variable.

3. The method as claimed in claim 1 , wherein the motor torque closed-loop controller component (M RK ) is determined by the processor as configured to provide closed-loop control.

4. The method as claimed in claim 3 , wherein the motor torque closed-loop controller component (M RK ) is limited to a steering-specific, maximum deliverable limiting value (+/−M RK,lim ).

5. The method as claimed in claim 3 , wherein the motor torque closed-loop controller component (M RK ) is limited as a function of the vehicle speed (V FZG ).

6. The method as claimed in claim 3 , wherein the closed-loop controller is embodied as a range-limited PID controller.

7. The method as claimed in claim 1 , wherein the motor torque pilot control component (M VSK ) is determined by the processor as a function of the torsion bar torque (M DS ) and a vehicle speed (VFZG) using an assistance characteristic curve.

8. The method as claimed in claim 1 , wherein the application torsion bar torque (MDS, Appl ) is determined by the processor using a determined toothed rack force (RFM-C, RFM-D) and/or further steering-specific or vehicle movement dynamics vehicle variables.

9. The method as claimed in claim 8 , wherein the application torsion bar torque (M DS, Appl ) is determined by the processor on the basis of different steering function components.

10. A nontransient computer-readable storage medium that store a computer program, said computer program when executed by a processor of a control unit of a power assisted steering system or power steering system, implementing a method comprising the steps of:

determining by the processor a motor torque pilot control component (M VSK ) based at least in part on a torsion bar torque (M DS ) detected at the steering column, the motor torque pilot control component (M VSK ) forming an open-loop controlled portion of said motor torque;

determining by the processor a motor torque closed-loop controller component (M RK ) which formed a closed-loop controlled portion of said motor torque, wherein a closed-loop control variable of said closed-loop controlled portion is said torsion bar torque (M DS );

functionally combining by the processor the motor torque pilot control component (M VSK ) and the motor torque closed-loop controller component (M RK ); and

determing by the processor the desired preset value ( Y M SM ) for the motor torque (M SM ) of the servomotor (SM) from the functionally combined motor torque pilot control component (M VSK ) and the motor torque closed-loop controller component (M RK ).

11. A control unit of a power assisted steering system or a power steering system for a motor vehicle having a steering column, the control unit comprising a processor, the processor during execution of a computer program embodying various configurations which lead to a determination of a desired preset value ( Y M SM ) for a motor torque of an electric servomotor in the power assisted steering system or the power steering system; and

wherein the processor has a first configuration among said various configurations to determine a motor torque pilot control component (M VSK ) of the motor torque based at least in part on a torsion bar torque (M DS ) detected at the steering column, the motor torque pilot control component (M VSK ) forming an open-loop controlled portion of said motor torque;

wherein the processor has a second configuration among said various configurations to determine a motor torque closed-loop controller component (M RK ) forming an open-loop controlled portion of said motor torque, wherein a closed-loop control variable of said closed-loop controlled portion is said torsion bar torque (M DS );

wherein the processor has a third configuration among said various configurations to functionally combine the motor torque pilot control component (M VSK ) and the motor torque closed-loop controller component (M RK ); and

wherein the processor has a fourth configuration among said various configurations to determine the desired preset value ( Y M SM ) for the motor torque (M SM ) of the servomotor (SM) from the functionally combined motor torque pilot control component (M VSK ) and the motor torque closed-loop controller component (M RK ).

12. The control unit of claim 11 in combination with said power assisted steering system or power steering system.

13. A method for determining a desired preset value ( Y M SM ) for a motor torque of an electric servomotor in a power assisted steering system for a motor vehicle, the power assisted steering system having a control unit comprising a processor, the method comprising:

determining by the processor a motor torque pilot control component (M VSK ) which forms an open-loop controlled portion;

determining by the processor a motor torque closed-loop controller component (M RK ) which forms a closed-loop controlled portion, wherein the closed-loop control variable is a torsion bar torque (M DS );

functionally combining by the processor the motor torque pilot control component and the motor torque closed-loop controller component; and

determining by the processor the desired preset value ( Y M SM ) for the motor torque (M SM ) of the servomotor (SM) from the functionally combined motor torque pilot control component and the motor torque closed-loop controller component.