Abstract: Linear direct drive motor includes a pair of axially spaced, relatively fixed stator poles and an armature mounted on a motor shaft for axial movement between the stator poles. The ends of the motor shaft are supported by centering springs which permit axial movement of the shaft and thus the armature relative to the stator poles. Positive stops are located between the stator and stator poles for preventing armature overtravel. Extending between the stator poles is a sleeve member which supports a ring magnet in radially spaced relation from the armature. Adjacent opposite ends of thee ring magnet are a plurality of layers of electrical coils, with the layers adjacent one end of the magnet being paired with different layers at the other end to provide redundant electrical channels and symmetric motion behavior.

Abstract: A direct drive valve and force motor assembly including interchangeable stator assembly and method for accurately setting the magnetic spring null of the motor with respect to the servo valve hydraulic null independent of the actual motor stator assembly, whereby the motor stator assembly may be configured as an interchangeable plug-in module with interface electrical connector. This is accomplished by using a simple fixture which simulates the motor stator assembly and senses rotor magnet position. The stator simulating fixture may be used to rotatably adjust the position of the rotor casing so that the magnetic spring null corresponds to the hydraulic valve null. Both the stator simulating fixture and motor stator assembly include an index pin engageable with a stator alignment keyway in the rotor casing for maintaining the desired orientation therebetween. Also, rotor over-travel stops keyed to the rotor casing may be centered during the nulling process.