Seagate Technology Incorporated

John Christopher Morris

Reed David Hanson

Thomas C Zirps

Yi-Ping Hsin

Dustin Mark Cvancara

Timothy Francis Ellis

Raye Abdoulie Sosseh

Tao Zhang

Nathaniel Boyd Wilson

Kenneth A Haapala

John Stuart Wright

David Allen Sluzewski

Travis Eugene Ell

Brian Robert Pollock

Samir Mittal

Brian G Molloy

Randall D Hampshire

Roger Alan Resh

Evgeny R Kharisov

Donald W Janz

Josiah Natan Wernow

Brent Jay Harmer

Peter Michael Young

Kyle Kenneth Eddy

Priyadarshee Deeptarag Mathur

Mike E Baum

Zhang Tao

An apparatus includes a first controller, a second controller, and a coupling compensator. The first controller is configured to generate a first voice coil motor (VCM) control signal in response to a first position error signal. The second controller is configured to generate a second VCM control signal in response to a second position error signal. The coupling compensator is configured to generate a first feedforward correction signal in response to the first VCM control signal. The first feedforward correction signal modifies the second VCM control signal to generate a modified second VCM control signal.

Feedforward compensation for multi-actuator hard drives

A feedforward compensator for induced vibration is disclosed. Controlled motions in an actuator induce mechanical disturbances in a surrounding cabinet. The feedforward compensator allows such disturbances to be compensated for without the need of a vibration sensor. The compensator provides a feedforward compensation signal configured to compensate for a mechanical disturbance predicted to be induced by a controlled motion of the actuator, and applies the feedforward compensation signal to a signal that controls the motion of the actuator.

Feedforward compensator for induced vibration

The present invention recognizes that induced RRO is coherent, i.e., the RRO has a large degree of repeatability from track to track. The present invention is a zero acceleration profile (compensation) process that targets CRRO (Coherent RRO). A process of the present invention represents a considerable reduction in the factory calibration time compared to other compensation techniques currently used. The reduction in time is attributed to the fact that CRRO can be computed by averaging position error signals (PES) over multiple tracks as opposed to total RRO which is computed by averaging over multiple revolutions on the same track.

Written-in error compensation method for coherent repeatable runout

An apparatus and method of maintaining stability in a servo loop of a disc drive is provided. A dither signal (a single frequency sine wave or a multi-frequency signal) is injected into the servo loop. A servo loop gain error signal is obtained in response to the injected dither signal. A gain of the servo loop is adjusted as a function of the servo loop gain error signal in real-time.

Apparatus and method for maintaining stability in a disc drive servo loop

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. Data representative of the radially-dependent repeatable run-out control components for the subset of the multiple tracks is then stored. The stored data representative of the radially-dependent repeatable run-out control components is retrieved before settling on the target track, and subsequently used to follow the selected track.

Method and apparatus for tracking radially-dependent repeatable run-out

An apparatus and method for controlling a dynamic system is provided in which primary position control output signals are generated at a position measurement sampling frequency. Intermediate position control output signals are generated between the primary position control output signals as a function of the primary position control output signals.

Method and apparatus for reducing vibration in a dynamic system

A control system for a data storage device including a constraint or weight to control stroke utilization and/or closed loop response of the control system. In particular, in one embodiment described, the weight or constraint is used to limit stroke utilization for a microactuator having a smaller stroke than a primary actuator. As described, the constraint or weight is used in conjunction with a mathematical synthesis to synthesize a controller to optimize system performance.

Control system for a data storage device with constraint

An NRRO compensation circuit controls a head position in a disc drive. The circuit has a first frequency circuit providing a first output corresponding to NRRO and a first characteristic sensing circuit that senses the first output and that generates a first control output that adjusts a first NRRO compensation gain. A first control circuit included in the NRRO compensation circuit receives the first control output and the first NRRO compensation gain and provides a first NRRO compensator output.

Disc drive with compensation for non-repeatable runout

An equalization filter for counteracting the effects of unwanted resonance modes and noise in the VCM plant. The filter comprises a transfer function derived from a function of the actual VCM plant response and an ideal response, for which the servo controller is designed. The response of the combined equalization filter and the actual VCM plant response substantially adheres to the ideal response. The disc drive includes firmware operable to generate one or more equalization filters for each of one or more heads.

Automatic model regulation in a disc drive servo system using model reference inverse

An apparatus and method of tracking repeatable runout in a disc drive servo loop is provided in which a feedforward signal having harmonic components that are updated at a sample rate that is a fraction of a servo sector sample rate is employed during track following.

Fractional-rate feedforward RRO compensator

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 (). A sensor is configured to move in a nominally longitudinal direction relative to a frame of reference (). A position scale is defined in a generally lateral direction relative to the longitudinal motion (). 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 ().

Guiding a sensor using a broadly-curved lateral profile

A system and method for correcting repeatable runout errors during manufacture of a disc drive. The system includes a Kalman filter having a recursive learning gain input and includes a recursive learning Again-setting circuit coupled to the recursive learning gain input. The recursive learning gain is initially set based on an estimate of a ratio of non-repeatable run out error to an estimate of the repeatable run out error. On subsequent recursions, the recursive learning gain-setting is reduced.

Repeatable runout compensation in a disc drive

A method and apparatus position a plurality of data heads relative to a plurality of surfaces of at least one disc in a disc drive. One of the plurality of data heads corresponds to each of the plurality of surfaces. The data heads are provided for writing information to the surfaces and reading information from the surfaces. Each of the data heads may be simultaneously positioned relative to the corresponding surfaces using the embedded servo information. Information can be simultaneously transferred relative to the corresponding surfaces using the plurality of data heads. Uninterrupted sequential data transfers may also be executed without servo overhead. Further, an apparatus is provided for accomplishing such servo control, as is a method of accomplishing model-based servo control.

Microactuator servo system in a disc drive

A method and apparatus for compensating for repeatable run-out errors in a disc drive is disclosed. The compensation is created by determining transfer function values for a servo loop in the drive as well as a sequence of repeatable run-out values for a portion of a disc. The repeatable run-out values are divided by respective transfer function values to produce compensation values that are inverse transformed to produce time-domain compensation values. These time-domain compensation values are injected into the servo loop to compensate for repeatable run-out errors.

Compensation for repeatable run-out error

A disc drive including a rotatable data track, a dual-stage actuator with a primary actuator motor supporting an actuator arm, a read/write head supported by the actuator arm and communicating with a secondary actuator motor, and steps for controlling range of motion of the secondary actuator motor. The controlling steps include supplying and sustaining a bias signal to a single-sided unipolar device driver that then apply a bias voltage the secondary actuator motor to induce the secondary actuator motor to expand substantially one half of its expansion capabilities. And, confining correction signals provided by a control circuit of the disc drive, used in correcting mechanical position of the secondary actuator motor, to a voltage ranging substantially between a positive &ldquo;&plus;&rdquo; and negative &ldquo;&minus;&rdquo; voltage substantially equal to the applied bias voltage.

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Minneapolis, MN, United States of America

John Christopher Morris