Patent ID: 6046879
Filing Date: 2000-04-04
Classification: G11B

Abstract:
In a disc drive of the type including a disc and an actuator adjacent the disc, the actuator having a head and an actuator coil of a voice coil motor, the disc having a surface including a plurality of nominally concentric tracks, the tracks including servo burst patterns read by the head to provide servo burst signals having magnitudes indicative of the position of the head with respect to the servo burst patterns, the disc drive further including control circuitry for applying current to the actuator coil to position the head with respect to the tracks, a method for controlling the position of the head relative to a selected track, comprising the steps of:generating digital representations of a first servo position error signal from the magnitudes of the servo burst signals from selected servo burst patterns of the selected track, the digital representations of the first servo position error signal having a magnitude indicative of the radial position of the head with respect to the selected track;generating digital representations of a second servo position error signal from the magnitudes of the servo burst signals from the selected servo burst patterns of the selected track, the digital representations of the second servo position error signal having a magnitude indicative of the radial position of the head with respect to the selected track, wherein the magnitude of the digital representations of the second servo position error signal is different from the magnitude of the digital representations of the first servo position error signal over at least a portion of the width of the selected track;generating digital representations of a third servo position error signal in relation to a sum of a weight value a multiplied by the digital representations of the first servo position error signal and a second weight value (1-.alpha.) multiplied by the digital representations of the second servo position error signal, the third servo position error signal having a magnitude which is substantially linear across the width of the selected track;generating a correction signal from the magnitude of the digital representations of the third servo position error signal; andproviding the correction signal to the control circuitry to output current to the actuator coil to position the head with respect to the selected track.