Abstract: A data storage drive includes a servo loop for positioning a head over a disc. The servo loop includes a sensor, located in the head, that senses servo information located on the disc and produces a servo signal therefrom. The servo signal is combined with a reference signal to produce a raw position error signal (PES). The servo loop further also at least one phase-matching disturbance attenuation (PMDA) filter that receives the raw PES as an input and responsively outputs a vibration-cancellation signal, which, when combined with the raw PES, cancels vibration-induced disturbance from the raw PES, thereby producing a refined PES. A servo controller receives the refined PES and responsively produces a servo control signal. An actuator moves the head in response to receiving the servo control signal.

Abstract: A voice coil motor (VCM) is controlled by applying a bipolar square wave actuator current to the VCM and calibrating a back electromotive force (back-EMF) measurement on the VCM in response to the square wave actuator current. Back-EMF on the VCM is measured while an actuator arm coupled to the VCM is in motion, and the VCM is controlled to move the actuator arm in response to the measured back-EMF voltage.

Abstract: A system is capable of detecting a “large” shock. In contrast to just any shock, a large shock exceeds some threshold of magnitude or duration and may generate particles and/or the deposit of particles on a recording head, which can result in write errors. Responsive to detection of a large shock, the system can take corrective action, such as executing one or more corrective action seeks after detection of the large shock or executing a series of corrective actions seeks during a certain number of load operations after detection of the large shock. RAW verifications may be performed to confirm correct write operation of the recording head after such corrective action.

Abstract: A voice coil motor (VCM) is controlled by applying a bipolar square wave actuator current to the VCM and calibrating a back electromotive force (back-EMF) measurement on the VCM in response to the square wave actuator current. Back-EMF on the VCM is measured while an actuator arm coupled to the VCM is in motion, and the VCM is controlled to move the actuator arm in response to the measured back-EMF voltage.

Abstract: An anti-notch filter in a servo control loop is phase locked to a nonrepeatable runout component of a servo control loop signal. The phase locked anti-notch filter may thereby more effectively track time varying characteristics of the nonrepeatable runout component so that they can be at least partially reduced in the servo control loop signal.

Abstract: A notch filter in a servo control loop is phase locked to a nonrepeatable runout component of a servo control loop signal. The phase locked notch filter may thereby more effectively track time varying characteristics of the nonrepeatable runout component so that they can be at least partially reduced in the servo control loop signal.

Abstract: A Bemf detect circuit is configured for modeling Bemf error via calculation of time correlations associated with two or more different non-calibrated sense resistor gain values to derive a calibrated sense resistor gain value. A method is provided for calibrating a Bemf detector circuit by setting a sense resistor gain to a plurality of different gain values, observing Bemf sample values for each of the gain values, and deriving a calibrated gain value by non-iteratively modeling the relationship between the gain values and the associated Bemf sample values.

Abstract: A system is capable of detecting a “large” shock. In contrast to just any shock, a large shock exceeds some threshold of magnitude or duration and may generate particles and/or the deposit of particles on a recording head, which can result in write errors. Responsive to detection of a large shock, the system can take corrective action, such as executing one or more corrective action seeks after detection of the large shock or executing a series of corrective actions seeks during a certain number of load operations after detection of the large shock. RAW verifications may be performed to confirm correct write operation of the recording head after such corrective action.

Abstract: A Bemf detect circuit is configured for modeling Bemf error via calculation of time correlations associated with two or more different non-calibrated sense resistor gain values to derive a calibrated sense resistor gain value. A method is provided for calibrating a Bemf detector circuit by setting a sense resistor gain to a plurality of different gain values, observing Bemf sample values for each of the gain values, and deriving a calibrated gain value by non-iteratively modeling the relationship between the gain values and the associated Bemf sample values.

Abstract: A shared state controller is provided that optimizes for settle, rotational vibration, and track following. The shared state controller uses the same state update equation with different output equations for settle and track follow. Two or more different track follow output equations may also be used. Switching logic determines which output equation to use in the controller. The shared state controller switches between a settle controller and a track follow controller based on the state of the actuator. In addition, the shared state controller may also switch between two or more track follow controllers based upon other parameters.

Abstract: An apparatus and method for tracking radially-dependent repeatable run-out in a disc drive having a servo loop for positioning a head over a rotating disc is provided. The disc includes multiple tracks. Radially-dependent repeatable run-out control components for at least a subset of the multiple tracks are first determined. The subset of the multiple tracks being boundary tracks of established zones of a disc. Data representative of the radially-dependent repeatable run-out control components for the subset of the multiple tracks is then stored in a table. The stored data representative of the radially-dependent repeatable run-out control components is utilized to interpolate or extrapolate the radially-dependent repeatable run-out control components for tracks within a zone or outside of the zones for which data is known.

Abstract: Problems inherent in guiding a sensor via a piecewise-linear lateral parametric profile are generally avoided using at least one broadly curved, generally lateral profile (494). A sensor is configured to move in a nominally longitudinal direction relative to a frame of reference (110). A position scale is defined in a generally lateral direction relative to the longitudinal motion (115). Each broadly curved lateral profile is defined in terms of its corresponding position scale, the scale(s) and the profile(s) both being part of a parametric model that is available for use in guiding the sensor (145).

Abstract: Method and apparatus for more accurate track following. Control circuitry rotates a data storage surface containing thousands of annular tracks. A “measured” subset of the tracks is selected so as to be interspersed with an “unmeasured” subset. The calibration profile is derived based on position error signals each obtained by reading from the measured subset and not from the unmeasured subset. Data from the unmeasured subset of tracks is ignored, in generating and/or updating the profile.

Abstract: An apparatus and method for tracking radially-dependent repeatable run-out in a disc drive having a servo loop for positioning a head over a rotating disc is provided. The disc includes multiple tracks. Radially-dependent repeatable run-out control components for at least a subset of the multiple tracks are first determined. The subset of the multiple tracks being boundary tracks of established zones of a disc. Data representative of the radially-dependent repeatable run-out control components for the subset of the multiple tracks is then stored in a table. The stored data representative of the radially-dependent repeatable run-out control components is utilized to interpolate or extrapolate the radially-dependent repeatable run-out control components for tracks within a zone or outside of the zones for which data is known.

Abstract: Problems inherent in guiding a sensor via a piecewise-linear lateral parametric profile are generally avoided using at least one broadly curved, generally lateral profile (494). A sensor is configured to move in a nominally longitudinal direction relative to a frame of reference (110). A position scale is defined in a generally lateral direction relative to the longitudinal motion (115). Each broadly curved lateral profile is defined in terms of its corresponding position scale, the scale(s) and the profile(s) both being part of a parametric model that is available for use in guiding the sensor (145).

Abstract: Method and apparatus are disclosed allowing for velocity sensing using back EMF in a media drive. A back EMF sensing circuit is provided that generates a velocity signal proportional to the back EMF in the head arm actuator coil, which signal may be utilized to improve head positioning control capabilities.

Abstract: A method and apparatus are provided for closed loop control of head load velocity in rotating media mass storage applications. A novel pulsed current velocity controlled head load/unload circuit is provided that uses the back EMF analog signal to modulate pulse amplitude. A system is thus provided having amplitude modulation of a fixed period current pulse train via back EMF feedback, whereby there is no need to monitor back EMF via A/D conversion circuitry.

Abstract: Method and apparatus for more accurate track following. Control circuitry rotates a data storage surface containing thousands of annular tracks. A “measured” subset of the tracks is selected so as to be interspersed with an “unmeasured” subset. The calibration profile is derived based on position error signals each obtained by reading from the measured subset and not from the unmeasured subset. Data from the unmeasured subset of tracks is ignored, in generating and/or updating the profile.

Abstract: A method and apparatus for performing track follow and seeking at quarter track positions that uses a non-conventional ordering of the servo fields at the quarter track positions, wherein C−A or D−B is used to track follow at−¼ track positions and A—D or B—C is used to track follow at +¼ track positions, for even and odd tracks, respectively. A position error signal is derived from relative amplitudes of the servo bursts and the read/write head is positioned over the quarter track position in accordance with the position error signal. The servo bursts are read in a time-displaced manner and the position error signal is determined from the relative amplitudes of the servo bursts.

Abstract: Method and apparatus are disclosed allowing for velocity sensing using back EMF in a media drive. A back EMF sensing circuit is provided that generates a velocity signal proportional to the back EMF in the head arm actuator coil, which signal may be utilized to improve head positioning control capabilities.