Patent ID: 7932684

Claim:
An apparatus, comprising: a linear motor comprising a stator and an armature that is movable relative to the stator over a travel distance; a first magnetic device coupled to the armature, the first magnetic device defining a sensing surface that comprises a plurality of magnetic poles that provide a magnetization state transition location there between; a magnetic pole sensor coupled to the stator adjacent the first magnetic device such that the first magnetic device moves past the magnetic pole sensor as the armature moves relative to the stator over the travel distance, the magnetic pole sensor sensing the adjacent poles of the first magnetic device; a second magnetic device coupled to the armature, the second magnetic device defining a sensing surface that comprises a plurality of adjacent alternating opposite magnetic poles that create a cyclically-varying magnetic field proximate its sensing surface; and a magnetic field angle sensor coupled to the stator adjacent the second magnetic device such that the cyclically-varying magnetic field of the second magnetic device moves past the magnetic field angle sensor as the armature moves relative to the stator, the magnetic field angle sensor sensing the angle of the magnetic fields of the second magnetic device and having an output that varies continuously relative to the magnetic field angle over at least a portion of one cycle of the cyclically-varying magnetic field.