Patent ID: 6636377
Filing Date: 2003-10-21
Classification: G11B

Abstract:
A method of tuning a servo control system in a disk drive having a disk with servo control information recorded thereon, a transducer for reading the servo control information, a servo control system that produces a control signal by combining (1) a feed-forward command effort signal uffwd and (2) a feedback command effort signal ufb derived from a difference between (i) a target position that is controllably varied during a seek with a PES reference signal r and (ii) an indicated position that includes an indicated PES signal y derived from the servo control information read by the transducer, and a voice coil motor (VCM) characterized by an actual frequency response G(z) for positioning the transducer in response to the control signal r wherein the feed-forward command effort signal uffwd and the PES reference signal r are designed to be compatible with one another on the basis of a modeled frequency response G0(z) such that the PES reference signal r and indicated PES signal y vary in unison during a seek when the servo control system uses the feed-forward command effort signal uffwd to position the transducer from an initial track position to a final target position, and wherein the actual frequency response G(z) is different than the modeled frequency response G0(z) such that the feed-forward command effort signal uffwd and the PES reference signal r are not compatible with one another, the method comprising the steps ofscaling the feed-forward command effort signal uffwd to substantially achieve a zero velocity condition at an end of a seek; scaling the feed-forward command effort signal uffwd to substantially achieve an on-target condition at the end of the seek; and modifying the PES reference signal r such that it substantially varies in unison with the indicated PES signal y during the seek.