Patent ID: 7561366

Claim:
A disk drive comprising: a head adapted to access a data storage disk; an actuator adapted to support the head and be driven by a voice coil motor; a detection circuit adapted to detect a first counter electromotive voltage generated by a first current caused to flow through the voice coil motor, with the actuator positioned in place, the detection circuit further adapted to detect a second counter electromotive voltage generated by a second current, different from the first current, caused to flow through the voice coil motor, with the actuator positioned in place, and the detection circuit further adapted to generate an output based on a circuit parameter; and a controller adapted to determine a correction factor applied to the output of the detection circuit using the first and second counter electromotive voltages, and to control the drive of the actuator using a value obtained by correcting an output of the detection circuit; wherein if the correction factor falls outside a reference limit, the controller determines a new circuit parameter for the detection circuit and a new correction factor appropriate to the new circuit parameter.