Seagate Technology Incorporated

Lealon Ray McKenzie

Roy Lynn Wood

Robert Dale Murphy

Randall D Hampshire

D Brent Douglas

Nathaniel Boyd Wilson

Philip Ray Woods

Ryan T Ratliff

Dennis D Duffy

Otis L Funches

Clyde Everett Goodner, Iii

Stuart Kevin Francis

Nigel Frank Misso

Qiang Bi

John Edward Moon

Raye Abdoulie Sosseh

Evgeny R Kharisov

Michael Edward Baum

David Charles Waugh

Anish A Ukani

Sandeep Dominic Sequeira

Brian W Sudman

Daniel Eugene Hobson

Matthew McLeod Chadsey

Arthur J Clark

Zai Yu Nang

Seow Zhao Li

Fereidoon Heydari

Paul M Quinnett

Steve M Gaub

Certain exemplary aspects of the present disclosure are directed towards apparatuses and methods which mitigate the effect of speaker vibration on a disc drive. Audio associated with a speaker output is detected and triggers the generation of an output signal indicative of speaker vibration associated with such an audio output of a speaker. A magnetoresistive transducer of the disc drive is positioned relative to a storage medium based on the output signal, a target data storage location in the storage medium from which data is to be accessed via the positioning, and the position of the transducer. The output signal mitigates the effect of the speaker vibration on the transducer.

Disc drive speaker vibration mitigation

Various embodiments relate to selectively inhibiting output from a transducer in response to the rate of change of acceleration that is experienced by the transducer. The rate of change of an acceleration signal, which is indicative of transducer's acceleration, is detected. Output of a signal through the transducer is selectively inhibited in response to the detected rate of change of the acceleration signal. A related apparatus can include a circuit that detects the rate of change of an acceleration signal and generates a transducer output inhibit signal in response to the detected rate of change of the acceleration signal. The transducer writes data on a recordable media. The accelerometer generates an acceleration signal that is indicative of transducer vibration. The circuit selectively inhibits writing of data through the transducer in response to a rate of change of the acceleration signal.

Selectively inhibiting transducer output responsive to detected jerk

Method and apparatus for identifying a resonance by changing a spindle speed, which has the effect of changing a corresponding sampling rate and Nyquist frequency. The invention discriminates (1) between plausible frequencies of true resonance and/or (2) aliased resonance from non-aliased resonances. This is accomplished by monitoring whether and/or how a resonance shifts during this speed change. Methods of the present invention monitor resonances by deriving a resonance indicator such as an apparent frequency (below the Nyquist frequency), a gain or error magnitude (compared to a derived threshold at a calculated frequency of interest), or similar criteria tested by values conventionally illustrated on a Bode plot. The present invention further includes steps or structural features for configuring a controller to attenuate or similarly limit an unwanted frequency component of an actuator control signal. In this way, resonances in the actuator can be reduced, and servo speed and accuracy thereby enhanced.

Resonance identification by commanding a spindle speed change

A method and apparatus are disclosed for improving seek performance of a disc drive through adaptive servo gain adjustment. The disc drive comprises a head adjacent a rotatable disc and a servo circuit which controllably positions the head adjacent tracks defined on the disc. During a seek operation in which the servo circuit moves the head from an initial track to a destination track, the servo circuit accumulates a velocity error as a sum of a series of velocity errors each obtained as a difference between an actual velocity of the head and a corresponding desired velocity over a selected radial distance of the disc. The servo circuit additionally measures an elapsed time for the head to pass over a second selected radial distance of the disc as the head is decelerated toward the destination track. Thereafter, the servo circuit adjusts a gain of the servo circuit in relation to the accumulated velocity error and the measured elapsed time.

Adaptive servo gain adjustment to improve disc drive seek performance

One embodiment of the present invention is directed to a method of aligning servo wedges of a plurality of disc surfaces in a disc drive. This process of aligning servo wedges in a disc drive includes writing multiple servo wedges, one adjacent another, continuously across an entire circumference of each disc surface. Subsequently, one of the disc surfaces is designated the master surface. Every n servo wedge on the master surface is then designated as a master wedge, where n is a positive integer. Next, the servo wedges on the non-master surfaces which are most closely axially aligned with the master wedges are selected. Subsequently, all of the non-selected and non-master wedges are erased.

Method of aligning servo wedges in a disc drive

A method for minimizing once per revolution (OPT) positional errors in a single disk servo track writer (STW) comprises clamping a disc in the servo track writer; spinning the disc at a predetermined speed; determining an average OPR positional error; and adjusting a reference position for writing servo tracks on the disc to include the average OPR positional error. The apparatus includes a distance measuring device positioned adjacent the disc in the STW. Another method for reducing the effects of OPR positional error in a disc drive comprises positioning a disc on a drive motor spindle in a disc drive during assembly of the drive; spinning the disc at a predetermined speed; determining the position of maximum peak to peak OPR position error, and then readjusting the position of the disc on the spindle to minimize the error. The apparatus for this method includes a controller, a distance sensor, and a positioner for nudging the disc to an optimum position on the disc drive spindle.

Method and apparatus for minimizing once per revolution positional errors in a disc drive

A method for minimizing once per revolution (OPR) positional errors in a single disk servo track writer (STW) comprises clamping a disc having an outer edge in the servo track writer; spinning the disc in the servo track writer at a predetermined speed; measuring distance from the disc edge to a predetermined point to determine peak to peak once per revolution positional error; determining an average once per revolution positional error from the peak to peak once per revolution positional error; and setting a reference position for writing servo tracks on the disc equal to a predetermined track reference plus the average once per revolution positional error. The servo track writer apparatus comprises a spindle motor for supporting and rotating a disc and a distance sensor such as an interferometer mounted a preset distance from the edge of the disc for measuring the once per revolution outer diameter positional error.

Method and apparatus for minimizing once per revolution positional errors in single disc servo track writing

An inductive rotational accelerometer for assisting in servo control of a hard disc drive using a torsional mass-spring system in combination with an inductance sensitive circuit to detect and measure the rotational vibrations imposed on a hard disc drive. The inductive rotational accelerometer includes a frame member coupled to the disc drive, the frame member supporting a pin on which is disposed a rotational mass. The rotational mass supports conductive blocks which with the rotational mass and the frame member provide a path for inductance.

Rotational inductive accelerometer

An apparatus and method for minimizing the effects of rotational vibration upon a disc drive having a base deck supporting a rotatable disc and an actuator having a moveable data head. A fixed head is supported over the disc at a predetermined radius and transduces a circumferentially extending frequency pattern written to the disc at a constant frequency to generate a readback signal. A frequency modulation (FM) demodulator generates a rotational velocity signal indicative of application of rotational vibration to the base deck in relation to changes in frequency of the readback signal. A servo circuit controllably positions the moveable data head in response to the rotational velocity signal and servo information readback by the moveable data head. The servo circuit interrupts a data transfer operation between the moveable data head and a host device when a magnitude of the rotational velocity signal exceeds a predetermined threshold. The circumferentially extending frequency pattern is preferably used to clock the writing of the servo information during disc drive manufacturing.

Rotational vibration compensation using a fixed head and a constant frequency pattern

An apparatus and method for minimizing the effects of rotational vibration upon a disc drive having first and second heads supported adjacent first and second disc recording surfaces, respectively. A frequency modulation (FM) demodulator generates a rotational velocity signal indicative of application of rotational vibration to the base deck in relation to changes in frequency of a readback signal generated from a circumferentially extending frequency pattern written to the first disc recording surface at a constant frequency. A servo circuit controllably positions the first and second heads in response to servo information stored on the second disc recording surface and the rotational velocity signal from the FM demodulator. The servo circuit further interrupts a data transfer operation between the second disc recording surface and a host device when a magnitude of the rotational velocity signal exceeds a predetermined threshold.

Rotational vibration compensation using a dedicated surface with a constant frequency pattern

An apparatus and method for detecting rotational vibration applied to a disc drive having an actuator supporting a head adjacent a rotatable disc. A spindle motor has a set of driver coils which rotate the disc through electrical commutation, and a set of velocity sense coils which sense the rotational velocity of the motor in relation to voltages established across the sense coils. Rotational vibration is detected in relation to changes in the rotational velocity of the disc. A data transfer operation between the disc and a host device is interrupted when the magnitude of the rotational vibration exceeds an acceptable level. A servo circuit compensates for the application of rotational vibration to the disc drive by adjusting current applied to the actuator in relation to the changes in the rotational velocity of the disc.

Rotational vibration detection using spindle motor velocity sense coils

Apparatus and method for improved disc drive data storage capacity and seek performance. The disc drive includes a rotatable disc with a recording surface on which a plurality of tracks are defined and an actuator which supports a head adjacent the tracks. A servo circuit uses a velocity profile to position the head adjacent a destination track, with the servo circuit adaptively selecting the velocity profile in relation to the physical location of the destination track. The servo circuit preferably uses a reduced maximum velocity and a decreased deceleration rate when the deceleration track is adjacent an innermost or outermost diameter of the disc, thereby reducing the risk of damage as a result of contact between the actuator and a limit stop used to limit radial excursion of the head.

Adapting seek velocity profile to destination track location

An apparatus and method for detecting rotational vibration applied to a disc drive having a rotary actuator adjacent a rotatable disc. The actuator supports a head adjacent a recording surface of the disc and an actuator coil in a magnetic field of a magnetic circuit of a voice coil motor. A second, velocity sense coil is further coupled to the actuator and immersed in the magnetic field of the magnetic circuit, with the velocity sense coil being electrically isolated from the actuator coil. Rotational vibration is detected in relation to a sense voltage induced across the velocity sense coil as the magnetic circuit is moved relative to the velocity sense coil. A data transfer operation between the head and a host device is interrupted when the magnitude of the rotational vibration exceeds a specified magnitude. A servo circuit applies current to the actuator coil to position the head relative to the disc recording surface in relation to servo information transduced by the head, as well as in relation to the sensed voltage from the velocity sense coil.

Rotational vibration detection using a velocity sense coil

Method and apparatus for compensating for errors in the location of servo frames in a disc drive, the servo frames providing control inputs to a servo loop of the disc drive. Each servo frame includes an additional compensation field to which a compensation term is written, the compensation term indicative of the average radial error in the location of the servo frame. The compensation term is determined by measuring the radial distance between adjacent servo frames over a plurality of revolutions of the disc and averaging these measured radial distances. The compensation terms are thereafter used in conjunction with position information from the servo frames to control the position of the head. The compensation term facilitates the elimination of repeatable, random errors in the locations of the servo frames, causing the head to nominally follow a circular path about the disc, regardless of the errors in the locations of the servo frames.

Dynamic compensation of servo burst measurement offsets in a disc drive

Method and apparatus for dynamically compensating for servo burst measurement offsets in a disc drive. A first type of servo position error signal is used during a compensation routine to position a head adjacent a selected track on a disc, the first type of servo position error signal determined from servo burst signals read by the head from servo position fields on the disc. A second type of servo position error signal is also generated from the servo burst signals and the difference between selected values of the second type of servo position error signal is compared to an acceptance limit. Compensation terms are incrementally added to the servo burst signals used to generate the second type of servo position error signal until the difference is below the acceptance limits. Thereafter, the compensation terms are stored and retrieved during normal track following operations to generate a compensated servo position error signal.

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Edmond, OK, United States of America

Lealon Ray McKenzie