The present invention may be regarded as a disk drive comprising a disk, a
head, an actuator arm for actuating the head radially over the disk, and a
voice coil motor (VCM) for rotating the actuator arm about a pivot, the
VCM comprising a coil comprising a VCM resistance R. A back EMF voltage
detector measures a back EMF voltage across the coil, and a current
detector detects a current I flowing through the coil. An IR voltage
detector, responsive to the current I detected by the current detector,
detects an IR voltage proportional to the current I times the VCM
resistance R. A voltage compensator substantially cancels the IR voltage
from the measured back EMF voltage to generate a compensated back EMF
voltage. A control voltage generator, responsive the compensated back EMF
voltage, generates a control voltage applied to the coil to generate the
current I flowing through the coil. A stall detector compares the current
I detected by the current detector to a threshold, wherein a VCM stall
condition is detected if the current I exceeds the threshold for a
predetermined interval.
