Abstract: A speed control system for an electronically commutated motor having stator windings, a rotor mounted for rotation relative to said windings, switches for individually energizing said windings, and phase steering means operable to close said switches to sequentially energize said windings. The control system includes means responsive to a rotational position of said rotor for initiating a speed measurement cycle, means for measuring rotor speed during each speed measurement cycle and for comparing the measured speed with a speed set-point, and means responsive to the rotor speed being less than said set-point for enabling said phase steering means to energize said windings.

Abstract: A disk assembly which is normally fixed on a disk drive, but which can be removed in the field from the disk drive spindle and replaced on the spindle with extreme precision so that pre-recorded tracks are concentric with the axis of the spindle within extremely small tolerances. The disk assembly includes a mounting ring which fits around the drive spindle, the ring having three resilient centering flexures extending slightly radially inwardly of the rest of the ring to engage the drive spindle, and all being outwardly deflected substantially the same amount to center the ring on the spindle.

Abstract: An opto-electronic transducer for determining position and/or velocity of one member with respect to another member is provided with light amplitude control. The transducer is comprised of a scale with a transmission grating on a first track and an indexing bar near each end of a second track adjacent the first, and a reticle with two sections of the same grating, one section being offset spatially one quarter cycle with respect to the other section for producing quadrature signals through two photosensors opposite the first track from which relative position and/or velocity between the reticle and the scale can be determined. A slit is provided in the reticle in order to provide information for determining position relative to the indexing bars. A single photosensor opposite the second track is used both to detect the indexing bars and to provide a feedback control signal to maintain the amplitude of light illuminating the scale and reticle constant.

Abstract: A synthesizer for multiphase waveforms is disclosed which is useful, for example, in open and closed loop control of a two-phase induction motor, such as for a magnetic recording disk spindle, utilizing a plurality of bistable elements, two for each phase, to control output power drivers. A single clock pulse counter is employed to time the setting and resetting of each bistable element according to some predetermined pattern controlled by combinational logic which presets the counter to proper values at appropriate times in response to external stimuli, such as speed feedback control and start-stop control.