Seagate Technology Incorporated

Clyde Everett Goodner, Iii

Lealon Ray McKenzie

Hieu Van Nguyen

Roy Lynn Wood

Monty Aaron Forehand

Robert Dale Murphy

Randall D Hampshire

Philip Ray Woods

Jack W Flinsbaugh

David Charles Waugh

Ronald D Metzner

Gopinath K Bendigeri

Mark A Hickl

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

An apparatus and method are disclosed for minimizing damage to a disc drive during head switching operations. The disc drive comprises a plurality of magnetic recording surfaces to and from which data are transferred using read/write heads, each head utilizing the application of a bias current during operation. To switch from a presently selected head to a target head, the disc drive determines a first value indicative of the magnitude of a bias current for the presently selected head and a target bias current to be applied to the target head. When the second value is greater than the first value, the disc drive switches from the presently selected head to the target head and then applies the target bias current; conversely, when the first value is greater than the second value, the target bias current is applied to the presently selected head and then the disc drive switches from the presently selected head to the target head.

Head switching sequence in a disc drive employing head bias currents

A temperature sensing system for use in a computer disc drive comprises a themoelectric sensor having an output sensor voltage which is variable as a function of temperature, an interface circuit adapted to receive the output sensor voltage from the thermoelectric sensor and adapted to generate a scaled and level-shifted analog output voltage signal, and an analog-to-digital converter circuit adapted to receive the analog output signal voltage from the interface circuit and convert the analog output signal voltage into a digital signal which is compared to various defined thresholds.

Thermoelectric temperature sensing system in a computer hard 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.

Dynamic compensation of servo burst measurement offsets in a disc drive

A data storage system comprised of a plurality of disc drives which each comprise a plurality of data storage discs rotated by a polyphase motor. Each disc drive has a servo system for radially positioning transducer heads proximate the disc surfaces and generating an index signal for a selected orientation of the discs. A reference signal generator in each disc drive produces a reference signal at each of a succession of time intervals equal to the desired period of rotation of the discs and the disc drives are interconnected to enable each disc drive to sense a reference signal generated by any other disc drive. Each disc drive includes a microcomputer that is periodically interrupted and, during the interrupt, transmits the reference signal generated by the disc drive to the other disc drives in the absence of reception of a reference signal from another disc drive prior to the interrupt to provide a common reference signal for all of the disc drives. The speed of the motor of each disc drive is controlled in relation to the time interval between generation of the index signal in the disc drive and generation of the common reference signal. Alternatively, each disk drive can be operated independently to control the motor speed in relation to the time between successive index signals.

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Midwest City, OK, United States of America

Clyde Everett Goodner, Iii