A moving magnet actuator is a type of electromagnetic linear actuator. It typically consists of an arrangement of a permanent magnet and coil, arranged so that currents in the coil generate a pair of equal and opposite forces between the coil and magnet. The main difference between this and a voice coil actuator is that in a moving magnet actuator, the magnet is intended to move and the coil to stay still, as opposed to vice versa.
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Moving magnet actuator Wikipedia(Text) CC BY-SA