Dynamic magnetic information storage or retrieval – Monitoring or testing the progress of recording
Reexamination Certificate
2002-03-07
2004-06-29
Faber, Alan T. (Department: 2651)
Dynamic magnetic information storage or retrieval
Monitoring or testing the progress of recording
C360S075000
Reexamination Certificate
active
06757120
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to the data processing field, and more particularly, relates to a dynamic method and apparatus for controlling head fly characteristics in a disk drive.
DESCRIPTION OF THE RELATED ART
Computers often include auxiliary memory storage units having media on which data can be written and from which data can be read for later use. Disk drive units incorporating stacked, commonly rotated rigid magnetic disks are used for storage of data in magnetic form on the disk surfaces. Data is recorded in concentric, radially spaced data information tracks arrayed on the surfaces of the disks. Transducer heads driven in a path toward and away from the disk axis of rotation write data to the disks and read data from the disks. Data located on a particular track on a disk surface is read or written by properly positioning a data transducer head directly over the track. In order to maintain the head in proper position over the data track, servo systems typically are incorporated into disk drives.
During operation of a disk drive, various conditions can cause changes in flyheight, such as accumulation of contamination debris on a head or disk can cause low flying height. Protruding disk defects or asperities can occur during operation of the disk drive and cause physical head-to-disk contact. Various arrangements have been provided for measuring flying height changes of a transducer head relative to a disk surface of a rotating disk in a disk file.
For example, U.S. Pat. No. 5,168,413 issued Dec. 1, 1992 to Coker et al., and assigned to the present assignee, discloses a method and apparatus are provided for measuring flying height changes of a transducer head relative to a disk surface of a rotating disk in a disk file. A predetermined pattern is written on at least one predetermined region of the disk file. The predetermined region is normally not rewritten during operation of the disk file. At least one readback signal is sensed from at least one predetermined region of the disk surface. A plurality of sample values are identified corresponding to each readback signal. A change in the flying height is calculated utilizing the identified sample values. A frequency equalization number K can be utilized to calculate the magnitude and sign of the flying height change. Alternatively, real-time digital analysis of a predetermined pattern written on at least one predetermined region of the disk surface can be utilized to calculate the magnitude and sign of the flying height change.
U.S. Pat. No. 5,625,506 issued Apr. 29, 1997 to Dovek et al., and assigned to the present assignee, discloses a method and apparatus are provided for maintaining file readback performance compensating for readback errors caused by head/disk interaction used with a data detection channel in a direct access storage device. A readback signal is sensed from at least one disk surface and a data channel error rate is detected responsive to the readback signal. The detected data channel error rate is compared with a first predetermined threshold value and a gain of a phase lock loop (PLL) in the peak data detection channel is optimized responsive to an identified data channel error rate with a first predetermined threshold value. The PLL gain is adjusted until a lowest error rate is detected. A failure warning for the direct access storage device is provided to a user when the detected PLL gain is greater than a predefined loop gain value.
In a conventional disk drive, once a transducer head is manufactured an assembled in the drive, it is not possible to control the fly characteristics, such as flyheight and angles relative to the disk surface.
A need exists for an effective mechanism for controlling head fly characteristics in a disk drive.
SUMMARY OF THE INVENTION
A principal object of the present invention is to provide a dynamic method and apparatus for controlling head fly characteristics in a disk drive. Other important objects of the present invention are to provide such dynamic method and apparatus for controlling head fly characteristics in a disk drive substantially without negative effect; and that overcome some of the disadvantages of prior art arrangements.
In brief, a dynamic method and apparatus are provided for controlling head fly characteristics in a disk drive. A plurality of charge surfaces is provided with a transducer head slider assembly. At least one head fly characteristic is monitored during operation of the disk drive. An identified current head fly characteristic is compared with a predefined head fly characteristic to identify a difference value. A charge and potential of the plurality of charge surfaces are dynamically controlled responsive to the identified difference value.
In accordance with features of the present invention, dynamically controlling the charge and potential of the plurality of charge enables both dynamically controlling flyheight of the transducer head slider assembly and dynamically controlling angles of the transducer head slider assembly relative to an associated disk surface.
REFERENCES:
patent: 5168413 (1992-12-01), Coker et al.
patent: 5625506 (1997-04-01), Dovek et al.
patent: 6359746 (2002-03-01), Kakekado et al.
patent: 6366416 (2002-04-01), Meyer et al.
patent: 6700724 (2004-03-01), Riddering et al.
patent: 2002/0097517 (2002-07-01), Bonin et al.
Minoshima Yoichi
Yamaguchi Mario
Faber Alan T.
Hitachi Global Storage Technologies - Netherlands B.V.
Pennington Joan
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