Patent ID: 6795268
Filing Date: 2004-09-21
Classification: G11B

Abstract:
A disk drive comprising:(a) a disk; (b) a head; (c) an actuator arm for actuating the head radially over the disk during a seek operation; (d) a voice coil motor (VCM) for rotating the actuator arm about a pivot, the VCM comprising a coil comprising a VCM resistance R; (e) a back EMF voltage detector for measuring a back EMF voltage across the coil; (f) a current detector for detecting a current I flowing through the coil; (g) an IR voltage detector, responsive to the current I detected by the current detector, for detecting an IR voltage proportional to the current I times the VCM resistance R; (h) a voltage compensator for substantially canceling the IR voltage from the measured back EMF voltage to generate a compensated back EMF voltage; (i) a control voltage generator, responsive the compensated back EMF voltage, for generating a control voltage applied to the coil to generate the current I flowing through the coil; (j) a memory for storing a first compensated back EMF voltage generated at a first time period of the seek operation; (k) a current integrator for integrating the current I detected by the current detector from the first time period to a second time period of the seek operation, wherein the second time period occurs when the integration crosses zero; (l) a comparator for comparing the first compensated back EMF voltage stored in the memory to a second compensated back EMF voltage generated at the second time period of the seek operation; and (m) a calibrator, responsive to the comparator, for calibrating the IR voltage detector.