Patent ID: 6690536
Filing Date: 2004-02-10
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; (d) a fixed object; (e) a voice coil motor (VCM) for rotating the actuator arm about a pivot, the VCM comprising a coil comprising a VCM resistance R; (f) a back EMF voltage detector for measuring a back EMF voltage across the coil; (g) a current detector for detecting a current I flowing through the coil; (h) 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; (i) a voltage compensator for substantially canceling the IR voltage from the measured back EMF voltage to generate a compensated back EMF voltage; (j) 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; and (k) a voltage calibrator, responsive to the current I detected by the current detector, for calibrating the IR voltage detector by: generating a calibration command input applied to the control voltage generator to move the actuator arm until it presses against the fixed object; programming the IR voltage detector to detect an initial IR voltage; and adjusting the IR voltage detector to incrementally change the detected IR voltage until the current I detected by the current detector reaches a predetermined level.