Position recognition in an electromagnetic actuator without sensors

A method for controlling an electromagnetic actuator comprising at least one armature (3), a first coil (1), a second coil (2) and one of a control electronics element and a power electronics element, the armature (3) being slidably mounted between the first coil (1) and the second coil (2), the first coil (1) having an input (4) and an output (7), both of which are connected to a first measurement amplifier (14), the second coil (2) having an input (11) and an output (13), both of which are connected to a second measurement amplifier (15), the first measurement amplifier (14) and the second measurement amplifier (15) being connected to a subtractor (16), which is connected to a logic unit (17), and the logic unit (17) being connected to the one of the control electronics element and the power electronics element, the method comprising the steps of:

• applying a sudden increase in voltage to the first coil (1) and the second coil (2);
• measuring, over time, a first voltage gradient (23) at the first coil (1) with a first measurement amplifier (14) and measuring a second voltage gradient (24) at the second coil (2) with a second measurement amplifier (15);
• transferring the first voltage gradient (23) and the second voltage gradient (24) to the subtractor (16) for computation of a third voltage gradient (25);
• and
• transferring the third voltage gradient (25) to the logic unit (17) for evaluation.