Limited rotation moving iron motor with novel velocity sensing and feedback

Claim 1

In combination, a limited rotation moving iron electromagnetic motor and a device for providing a voltage indicating the angular velocity of rotation of the armature of said motor, said motor comprising a rotatable armature of ferromagnetic material mounted for rotation about an axis, a stator adjacent to said armature, a stationary permanent magnet, and a stationary drive coil through which a drive current flows, and means for elastic angular restraint attached to said armature wherein said stator, magnet, armature, and drive coil are arranged to apply permanent magnet biasing flux and to apply magnetic flux produced by said drive current to rotate said armature from said neutral position in an amount and direction dependent upon the flow of said drive current and the stiffness of said elastic restraint, said device comprising: means for providing a first voltage dependent upon said angular velocity of said armature, the self-inductance of said drive coil, and said drive current, a compensation coil magnetically coupled through a gap to said drive coil and magnetically isolated from the effects of said rotating armature to provide a second voltage, said second voltage appearing across said compensation coil and being dependent upon mutual inductance between said compensation coil and said drive coil and upon said drive current, said second voltage being substantially unaffected by angular velocity of rotation of said armature due to said magnetic isolation of said compensation coil from the effects of said rotating armature, and combining means for proportionally combining said first and second voltages to provide said voltage indicating said angular velocity of rotation.

Claim 8

The apparatus of claims 1, 4 or 5 wherein said combining means includes a resistance network for proportionally combining said second voltage with said first voltage.

Claim 11

The apparatus of one of claims 1, 2, 3, 4, 5, 6, 8 or 9 wherein said stator is located adjacent to said armature and extends lengthwise of said armature along said axis of rotation of said armature, said permanent magnet extends lengthwise of said stator, said drive coil is wound on said stator extending lengthwise of said stator with the axis of said drive coil generally perpendicular to said axis of rotation, and said compensation coil is wound on a core separate from said stator, said compensation coil and core extending lengthwise of said drive coil and located adjacent to said drive coil on the side of said drive coil opposite said armature, with the axis of said compensation coil generally parallel to said drive coil axis, so that said drive coil and said stator magnetically isolate said compensation coil from the effects of said rotating armature.

Claim 12

The apparatus of one of claims 1-6, 8 or 9 wherein said stator is located adjacent to said armature and extends lengthwise of said armature along said axis of rotation of said armature, said permanent magnet extends lengthwise of said stator, said drive coil is wound on said stator extending lengthwise of said stator with the axis of said drive coil generally perpendicular to said axis of rotation, said compensation coil is wound on a core separate from said stator, said compensation coil and core being located closely adjacent to said drive coil at a longitudinal end of said stator, so that said drive coil and said stator magnetically isolate said compensation coil from the effects of said rotating armature.