Method for pressing a workpiece with a predetermined pressing force

2:

• The method according to claim 1, wherein after detection of the pressing force increase, the electric motor (2) is braked to a predetermined minimal speed of rotation.

3:

• The method according to claim 2, wherein the electric motor (2) is operated at the minimal speed of rotation for a predetermined or predeterminable period of time, until vibrations that occur in the drive system due to the braking process from the reduced speed of rotation to the minimal speed of rotation have died out, to the greatest possible extent.

4:

• The method according to claim 1, wherein during forming of the workpiece (4), control of the electric motor (2) is set by the regulator (5) on the basis of the pressing force measured in the measuring unit (12).

5:

• The method according to claim 1, wherein the reduced speed of rotation amounts to between 0.1% and 100%, in particular between 0.5% and 99%, preferably between 50% and 80% of the maximal speed of rotation.

6:

• The method according to claim 1, wherein directly after detection of the pressing force increase, further control of the electric motor (2) is set by the regulator (5) on the basis of the pressing force, wherein after detection of the pressing force increase, the electric motor (2) is braked to a predetermined minimal speed of rotation, and in an initial period during the braking process, a pressing force based on a model calculation is superimposed on the pressing force detected in the measuring unit (12), and after the initial period, the pressing force detected by the measuring unit (12) serves as an input variable for the regulator (5).

7:

• The method according to claim 6, wherein in the model calculation, the mass inertia and/or the spring stiffness and/or the damping and the angular or linear accelerations of the individual components built into the drive train is/are taken into consideration.

8:

• The method according to claim 6, wherein the model calculation is adapted on the basis of the respectively previous cycles, in an iterative learning process, wherein for adaptation of the model calculation, the Time Progression of the measured value of the pressing force in the measuring unit (12), as well as of the motor moment and of the related angle of rotation of the drive shaft (8) in the electric motor (2) are used.

9:

• The method according to claim 6, wherein for superimposition of model calculation and pressing force detected in the measuring unit (12), an interference variable observer (19), in particular a Kalman filter is used.

10:

• The method according to claim 9, wherein superimposition between the actual force estimated in the interference variable observer (19) and the force detected in the measuring unit (14) is carried out.

11:

• The method according to claim 1, wherein a Piezo sensor is used as a measuring unit (12), which sensor is disposed in the region of the forming tool, so as to detect the pressing force.

12:

• The method according to claim 1, wherein directly after detection of the pressing force increase, further control of the electric motor (2) is set by the regulator (5) on the basis of a reference trajectory of the pressing force value, wherein the speed of rotation progression is calculated in a pre-controller, from the reference trajectory of the pressing force value.

13:

• The method according to claim 12, wherein in a first phase after detection of the pressing force increase, the pressing force value is estimated by means of an interference variable observer (19), and that in a second phase after detection of the pressing force increase, the pressing force is detected directly by the measuring unit (12), and serves as an input variable for the regulator (5).

14:

• The method according to claim 1, wherein the transition between different speeds of rotation of the individual method steps is set in such a manner that no sudden increases in acceleration occur.