Method for controlling an electromechanical actuator, and control device

1. A method for controlling an electromechanical actuator of a brake system for motor vehicles, comprising the steps of:

determining a first actuator speed setpoint value on the basis of a specified setpoint value of a controlled variable and a measured actual value of the controlled variable using a first controller, wherein the controlled variable comprises a system pressure or a brake application force,

determining a second actuator speed setpoint value on the basis of the specified setpoint value of the controlled variable and a specified relationship between the controlled variable and a position variable corresponding to a position of the electromechanical actuator;

determining an actuating variable for the electromechanical actuator on the basis of the first actuator speed setpoint value and the second actuator speed setpoint value, and

controlling the actuator to set the measured actual value of the controlled variable to the setpoint value of the controlled variable

determining a third actuator speed value by adding together the first and the second actuator speed setpoint value, and the third actuator speed setpoint value is fed, as an input variable, to a second controller.

2. The method as claimed in claim 1 further comprising determining an actuator position setpoint value by a specified relationship between the controlled variable and an actuator position or a variable corresponding to the actuator position.

3. The method as claimed in claim 2 , further comprising filtering the actuator position setpoint value and using the filtered actuator position setpoint value for determining the actuator position setpoint value.

4. The method as claimed in claim 2 further comprising determining the second actuator speed setpoint value from the actuator position setpoint value.

5. The method as claimed in claim 2 further comprising carrying out an increase limitation of the determined actuator position setpoint value, by a limitation of a change in actuator position setpoint values that are determined at different sampling times to a maximum position change per one sampling time of the first controller.

6. The method as claimed in claim 5 , further comprising determining a limited actuator position setpoint value or a limited change in the actuator position setpoint value in response to carrying out the increase limitation and determining a first actuator speed on the basis of the limited actuator position setpoint value or the limited change in the actuator position setpoint value.

7. The method according to claim 6 , further comprising weighing the first actuator speed by multiplication with a scaling factor and defining a weighted first actuator speed.

8. The method as claimed in claim 7 further comprising carrying out a speed limitation of the weighted first actuator speed, wherein, the speed limitation is carried out as a function of a direction of rotation of the actuator.

9. The method as claimed in claim 5 determining the second actuator speed setpoint value on the basis of the limited actuator position setpoint value or the limited change in the actuator position setpoint value or the determined first actuator speed of the second actuator speed setpoint value.

10. A control device for an electromechanical actuator of a brake system for motor vehicles, comprising:

a first controller to which a specified setpoint value of a controlled variable and a measured actual value of the controlled variable are fed as input variables, and which determines a first actuator speed setpoint value, wherein the controlled variable comprises a system pressure or a brake application force,

a second controller, connected downstream of the first controller, wherein a third actuator speed setpoint value is determined from the first actuator speed setpoint value and a second actuator speed setpoint value, by addition,

wherein the second actuator speed setpoint value is determined on the basis of the setpoint value of the controlled variable and a specified relationship between the controlled variable and a position variable corresponding to a position of the electromechanical actuator;

wherein the control device controls the actuator to set the measured actual value of the controlled variable to the setpoint value of the controlled variable.

11. The control device as claimed in claim 10 , further comprising a means for calculating an actuator position setpoint value from the setpoint value of the controlled variable by the specified relationship and for determining the second actuator speed setpoint value from the actuator position setpoint value.

12. The control device as claimed in claim 11 , further comprising a means for determining an increase limitation of the determined actuator position setpoint value and defining a limited actuator position setpoint value, and for limiting a change in the actuator position setpoint value to a maximum position change per one sampling time of the first controller and defining a limited change in the actuator position setpoint value.

13. The control device as claimed in claim 12 , further comprising a means for calculating a first actuator speed from the limited actuator position setpoint value or from the limited change in the actuator position setpoint value.

14. The control device as claimed in claim 13 , further comprising a means for multiplying the first actuator speed with a scaling factor or a means for limiting the first actuator speed.