Abstract: Method and apparatus for reducing repeatable runout signals in a servo position error (SPE) signal of a disc drive actuator. During track following, a measurement estimate is obtained through the sampling and accumulating of data from the SPE over a mechanical revolution of the drive, the measurement estimate providing a characterization of the repeatable runout signal in the servo position error signal. A correction estimate is updated by the measurement estimate, and the correction estimate is added to the servo position error signal to provide an adjusted servo position error signal. The disc drive uses the adjusted servo position error signal to generate a correction signal for adjusting the position of the actuator. The measurement estimate is reset after each update of the correction estimate and a new measurement estimate is generated during each subsequent rotation of the disc drive during track following mode.

Abstract: A method for calibrating the position error signal in a servo system of a disc drive. The disc drive comprises a disc and an actuator adjacent the disc, the actuator including a head which is controllably positionable relative to data tracks on the surface of the disc using a servo position error signal generated using a scale factor generally indicative of the ratio of the width of the head to the width of the tracks on the disc. The head is positioned at the center of a selected track using an initial scale factor for the position error signal, the selected track having servo position fields comprising a plurality of burst patterns. The burst patterns include a first burst pattern extending radially from a first track boundary to a second track boundary of the selected track, a second burst pattern extending radially from the center of the selected track to the first track boundary and a third burst pattern extending radially from the center of the selected track to the second track boundary.

Abstract: A method and apparatus for testing for mechanical defects in a disc drive during manufacturing test is disclosed. Resonances in the disc drive are excited by injecting a sinusoidal test signal of known magnitude and frequency into an incoming servo position error (SPE) signal in the servo loop to provide a modified SPE. While the test signal is injected, the modified SPE is sampled and filtered to characterize the test frequency in the modified SPE which is compared to a resultant frequency characterized in the incoming SPE. The presence of resonances in the disc drive structure will result in an increase in the gain of the loop as indicated by the characterized resonant frequencies from the incoming and modified SPE. When the gain exceeds predetermined criteria, an error flag is set indicative of a failure condition for the disc drive, enabling the disc drive to be removed from test for subsequent remedial actions.