Abstract: For step motors positioned in response to an external reference location, correction for potential one step misalignment is provided. The method and the apparatus of the invention provide a read/write memory, for storing therein a phase state of the step motor at a particular location, e.g. a home position. The home position may coincide with the external reference location or may be offset therefrom by some predetermined move of the step motor. During cold starts, where memory is not retained, the step motor is moved to its home position and then the phase state of the machine is saved. On subsequent warm starts, after the step motor is moved to the assumed home position, the step motor is controlled to assume the phase state that has been previously stored.

Abstract: A magnetic flux-shifting or magnetic latch valve includes a first flux path including a first permanent magnet having a large coercive force so that its polarity cannot readily be altered. It further includes a second flux path including a second permanent magnet having a small coercive force so that its polarity can be altered. A valve according to this invention further includes a d-c source and a winding energized by said d-c source for altering the polarity of said second magnet.The fluid valve includes a valve element and a valve seat cooperating with the valve element. The valve has two limit positions, i.e. fully open and fully closed. In the fully closed position the pole surfaces of magnetic flux paths have the same magnetic polarity and hence do not attract each other permitting gravity, spring or hydrostatic means to form a gap therebetween.

Abstract: A magnetic flux-shifting or magnetic latch valve includes a first flux path including a first permanent magnet having a large coercive force so that its polarity cannot readily be altered. It further includes a second flux path including a second permanent magnet having a small coercive force so that its polarity can be altered. A valve according to this invention further includes a d-c source and a winding energized by said d-c source for altering the polarity of said second magnet.The fluid valve includes a valve element and a valve seat cooperating with the valve element. The valve has two limit positions, i.e. fully open and fully closed. In the fully closed position the pole surfaces of magnetic flux paths have the same magnetic polarity and hence do not attract each other permitting gravity, spring or hydrostatic means to form a gap therebetween.