Bipolar motor control

Abstract

A disc drive system is disclosed including a data storage disc having a plurality of data storage tracks. Each track has a centerline, the centerlines of adjacent tracks being spaced by a fixed track space distance. The disc surface also includes wedge servo sectors; servo data in each sector includes first servo information stored at a position on one side of said data track centerline and one-half said track space distance from said centerline, and second servo information stored at the other side of said data track centerline and one-half of said track space distance from said centerline. Positionable accessing is provided for reading the servo data and for generating servo signals representing the first and second servo burst information, to positioning said transducer accurately. The stepper motor has a plurality of stator coils subject to selective simultaneous energization at nominal current with currents of selected polarities of all or all but one of said coils for defining a plurality of motor detent positions. The servo information is located at positions defined by said motor detent positions. The data track is reached by the transducer by applying approximately one-half of said energization current to the one non-energized coil to reach said motor detent servo track position, the motor detent position on the other side of said track centerline being reached by energization of all the coils with currents of selected polarities.