Abstract: Disclosed is a disk drive having a plant with a moveable transducer and a servo controller that more precisely controls the transducer during short to medium seeks by producing a multi-rate feed-forward command effort signal.

Abstract: A method in a magnetic storage disk drive for independently learning and thereafter canceling repeatable runout that is written to the servo fields of each servo track during the servo writing process. The method does not require a servo writer because the disk drive may independently detect the runout without spinning out of control in response to such runout by operating its servo control loop in a low bandwidth mode so that it is less responsive to the higher frequency components of the runout, and by removing the effect of the DC component of the runout or selected harmonics on each revolution.

Abstract: A method in a magnetic storage disk drive for independently learning and thereafter canceling repeatable runout that is written to the servo fields of each servo track during the servo writing process. The method does not require a servo writer because the disk drive may independently detect the runout without spinning out of control in response to such runout by operating its servo control loop in a low bandwidth mode so that it is less responsive to the higher frequency components of the runout, and by removing the effect of the DC component of the runout or selected harmonics on each revolution.The method takes several revolutions to "learn" the servo wedges of a current track by initializing a wedge runout value for each servo wedge and an average uncorrected runout value and then successively developing an interim wedge runout estimate for each servo wedge by adding a fractional portion .lambda. of a raw position error signal to a fractional portion (1-.lambda.

Abstract: The invention is a method of calibrating a position error signal (PES) to overcome the problem of a measured displacement or PES that varies as a non-linear function of real displacement when the read transducer is positioned to either side of a null position where the PES equals zero. The PES is notably nonlinear while reading servo burst information with a Magneto-Resistive (MR) head which has nonlinear magnetic characteristics. The method uniquely calibrates the measured PES to provide a corrected PES without requiring any knowledge of the actual displacement from the position where the measured PES equals 0. The calibration according to this method, therefore, may be performed at anytime without need for real displacement information from a servowriter or any sort of special calibration track.