Abstract: The invention relates to a method for driving and measuring the position of an electromagnetic actuator that operates according to the voice coil principle. The coil thus moves within a magnetized gap relative to permanent magnet core. As the coil extends partially outside of the core, its inductance will change. The voice coil is connected to a controllable current source that can both generate and control an average current and an AC component through the voice coil. The frequency of the AC component is measured, and is a function of the instantaneous inductance of coil, which in turn is a function of the coil's position relative to the core. In an alternative embodiment, the phase shift between an AC current and an AC voltage through the coil is analyzed to determine the position of the coil, while simultaneously controlling the force.

Abstract: The invention relates to an electromagnetic actuator for a rapid linear motion with a limited length of stroke. The electromagnetic actuator includes a stationary arranged first coil (1, 6) and a second movable coil (2), with the winding of the stationary coil connected to controllable power source (7) and the winding of the movable coil is short-circuited without any galvanic connection to an external power source The ends of the winding of the movable coil of the electromagnetic actuator is short-circuited via a rectifier element (9), preferably a diode. The diode allows a current to be developed in one direction only in the winding of the second coil, said current being induced from an electromagnetic field generated by a current through the first coil. In this manner is a double-acting electromagnetic actuator with very low weight obtained, resulting in very rapid response and high reliability, due to the lack of any external electrical connections to the movable coil.