Method and device for controlling an electrohydraulic brake system

1. A method for controlling an electrohydraulic brake system for motor vehicles, comprising at least one hydraulically actuatable wheel brake ( 9 ) which can be actuated by means of an electronically activatable pressure supply unit ( 16 ) which includes a cylinder-piston arrangement having a hydraulic pressure chamber ( 4 ), and a piston ( 3 ) which is displaceable by an electromechanical actuator ( 1 ), so that a predeterminable pressure reference value (P V,Soll ) is configured to be set in the hydraulic pressure chamber ( 4 ), an actuator position actual value (X Akt ) of a position of the pressure supply unit ( 16 ) being ascertained, a manipulated variable (ω Akt,Soll , M Akt,Soll ) for activating the actuator ( 1 ) generated by means of a control device( 40 ), a position control ( 50 ) of the actuator ( 1 ) being carried out in the control device ( 40 ) on the basis of the actuator position actual value (X Akt ) and of an actuator position reference value (X Mod,Soll ) and the actuator position reference value (X Mod,Soll ) being determined on the basis of the predetermined pressure reference value (P V,Soll ).

2. The method as claimed in claim 1 , further comprising in that the actuator position reference value (X Mod,Soll ) is determined from the pressure reference value (P V,Soll ) on the basis of a predetermined interrelationship between pressure in the pressure chamber and position ( 20 ) of the piston or of the actuator.

3. The method as claimed in claim 1 further comprising in that an actuator torque actual value (M Akt ) of the electromechanical actuator ( 1 ) is ascertained and that the actuator torque actual value (M Akt ) is used in determining the actuator position reference value (X Mod,Soll ).

4. The method as claimed in claim 3 , further comprising in that a correction (ΔX Korr ) of the actuator position reference value (X Mod,Soll ) is calculated exclusively from the pressure reference value (P V,Soll ) on the basis of the actuator torque actual value (M Akt ).

5. The method as claimed in claim 4 , further comprising in that an actuator torque reference value (M Mod,Soll ), which is utilized for the correction (ΔX Korr ) of the position reference value (X Mod,Soll ), is determined ( 67 ) from the pressure reference value (P V,Soll ).

6. The method as claimed in claim 4 further comprising in that the correction of the actuator position reference value (ΔX Korr ) is determined on the basis of the pressure reference value (P V,Soll ) of the actuator torque actual value (M Akt ) and of an actuator acceleration torque (M acc ).

7. The method as claimed in claim 6 , further comprising in that the correction of the actuator position reference value (ΔX Korr ) is added to the actuator position reference value (X Mod,Soll ) calculated from the pressure reference value (P V,Soll ), and in that a resulting actuator position value is supplied to the position control ( 50 ) as the actuator position reference value (X Mod,Soll ).

8. The method as claimed in claim 6 further comprising in that a difference from the actuator torque actual value (M Akt ) and the actuator acceleration torque (M acc ) is subtracted from an actuator torque reference value (M Mod,Soll ) calculated from the pressure reference value (P V,Soll ) and in that this difference (ΔM Prs ) is integrated to form the correction of the actuator position reference value (ΔX korr ).

9. A device for controlling an electrohydraulic brake system, comprising an electronically activatable pressure supply unit ( 16 ) having a pressure chamber ( 4 ) of which a predeterminable pressure reference value (PV,Soll) is configured to be set, comprising a means ( 17 ) for ascertaining an actuator position actual value (X Akt ) of a position of the pressure supply unit ( 16 ), a means for ascertaining an actuator torque actual value (M Akt ) of the electromechanical actuator ( 1 ), and a control device ( 40 ) which generates a manipulated variable (ω Akt,Soll , M Akt,Soll ) for activating the actuator ( 1 ), the control device ( 40 ) includes a position control device ( 50 , 30 ) to which the actuator position actual value (X Akt ) and an actuator position reference value (X Mod,Soll ) determined, on the basis of the predetermined pressure reference value (P V,Soll ) are supplied as input variables.

10. The device as claimed in claim 9 , further comprising in that the position control device ( 50 , 30 ) includes a position controller ( 30 ) with a subordinate speed controller ( 32 ).

11. The device as claimed in claim 9 further comprising in that the control device ( 40 ) includes a first functional module ( 20 , 65 ) in which a first of the actuator position reference value (X Mod,Soll ) is determined from the pressure reference value (P V,Soll ) on the basis of a predetermined interrelationship between pressure in the pressure chamber and a position ( 20 ) of the actuator, and in which a correction ( 65 ) of the first actuator position reference value (X Mod,Soll ) carried out on the basis of the actuator torque actual value (M Akt ).

12. The device as claimed in claim 11 further comprising in that the control device ( 40 ) includes a second functional module ( 60 ) inwhich a correction actuator position value (ΔX korr ) is determined on the basis of the pressure reference value (P V,Soll ), of the actuator torque actual value (M Akt ) and of an actuator acceleration torque (M acc ).

13. The method as claimed in claim wherein the method is carried out by providing a control device ( 40 ).

14. An electrohydraulic brake system for motor vehicles, comprising at least one hydraulically actuatable wheel brake ( 9 ) which can be actuated by means of the device in accordance with claim 9 .