Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Reexamination Certificate
2000-06-08
2001-10-02
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
Reexamination Certificate
active
06297926
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 arising from an application for Device And Method For Compensating For Interhead Track Position Offset Due To The Offset Of Tracks On Disk Surfaces earlier filed in the Korean Industrial Property Office on Sep. 6, 1995 and there duly assigned Ser. No. 29235/1995.
BACKGROUND OF THE INVENTION
The present invention relates to a disk drive recording apparatus employing an embedded servo sector mode, and more particularly, to a device for a disk drive recording apparatus having at least one disk and a plurality of heads separated from each other on respective surfaces of the disk, for compensating for interhead track position offset caused by the offset of tracks on the disk surfaces in head switching and a method thereof.
A hard disk drive, which is widely used for auxiliary data storage in a computer system, magnetically records data transmitted from a host computer on a disk, and reproduces and outputs the magnetically recorded data. The data transmitted from the host computer is recorded on tracks that are concentrically arranged on the disk. The tracks are divided into data sections where actual data is recorded, and servo sections where servo information is recorded. The servo information includes a variety of information components (i.e., index, sector number, head number, burst signal, etc.), and is used for servo control of a magentic head (i.e., the head's position control and velocity control) while reading and writing data. The servo information is permanently recorded on the disk by a servo writer. Representative servo recording modes include a dedicated servo sector mode and an embedded servo sector mode. The dedicated servo sector mode is performed by selecting the most stable disk surfaces among the several disk surfaces used, so as to record servo information on the entire surface of the disk. The embedded servo sector mode, on the other hand, sets in an identical form a predetermined number of servo sections for the data sections on the overall disk surfaces that are used, and records the servo information.
In conventional disk drive recording apparatuses, one of the main objectives to achieve is to maximize the amount of data that is recorded on the disk; for instance, to increase the tracks per inch (TPI). A condition precedent for this objective is the reliability of servo control. However, mechanical deformations (e.g., thermal expansion, assembly error or external impacts) caused by high track density have a severe influence on the servo control so that the embedded servo sector mode is used more widely than the dedicated servo sector mode. This is because the embedded servo sector mode performs servo control using servo information read from the disk surfaces corresponding to the respective heads. Therefore, thermal offset between heads due to thermal expansion rarely occurs. Nonetheless, various offsets do occur in magnetic disk recording devices, and are a problem.
One prior art reference directed towards correcting offsets in a magnetic disk recording unit is U.S. Pat. No. 5,457,587 entitled Method And System For Correcting Offset Of Head Position Signal issued to Suzuki. In Suzuki '587, the offset of a head position signal is measured and corrected to avoid undesirable effects caused on tracks of a disk. While this reference provides an approach to correcting offsets in a magnetic disk recording unit, I note that it fails to address how to compensate for a track position offset when switching from one head positioned on one surface of a disk to another head positioned on the opposite surface of the disk.
Another prior art reference that discusses the correction of offsets in a magnetic disk recording unit is U.S. Pat. No. 5,185,681 entitled Thermal Offset Compensation For High Density Disk Drives issued to Volz et al. In Volz et al. '681, thermally induced offsets of data heads are compensated for to avoid errors when reading and writing data. While this reference discloses an approach for compensating for offsets in data beads that result from the thermal expansion of actuator arms, I note that it fails to address how to compensate for offsets in tracks that result, for example, from characteristics of a servo writer.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a device for a disk drive recording apparatus employing the embedded servo sector mode.
It is another object to provide a device for a disk drive recording apparatus for compensating for interhead track position offset caused by the offset of tracks on different disk surfaces in head switching, thereby enhancing servo control performance.
It is still another object to provide a method for a disk drive recording apparatus employing the embedded servo sector mode.
It is yet another object to provide a method for a disk drive recording apparatus for compensating for interhead track position offset caused by the offset of tracks on different disk surfaces in head switching, thereby enhancing servo control performance.
To achieve these and other objects, the present invention provides a device for compensating for interhead track position offset in a disk drive recording apparatus including at least one disk having concentrically arranged tracks with servo information periodically arranged on the tracks and a plurality of heads separated from each other and placed on respective surfaces of the disk. The device contemplates a servo sampling timing generator circuit for measuring interhead track position offset values representative of the interhead track position offset on the respective surfaces of the disk. A microcontroller calculates and stores an average value of the interhead track position offset values. The microcontroller compensates for the interhead track position offset, based on the average value, in head switching from the tracks on a selected surface of the disk to the tracks on an opposite surface of the disk.
The present invention further provides a method for compensating for interhead track position offset in a disk drive recording device having a plurality of heads and disks on which servo information for measuring interhead track position offset generated in head switching is recorded on a predetermined cylinder of the disks in an embedded servo sector mode. The method contemplates the steps of: searching the predetermined cylinder on which the servo information is recorded to locate a servo calibration track; setting one of the plurality of heads as a reference head and measuring track position offset values while switching from the reference head to a second one of the heads; calculating and storing an average value of the track position offset values; and compensating for the track position offset between the reference head and the second head by using the average value, and then performing head switching between the reference head and the second head.
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Yozo Hibino “Control Method for Magnetic Disk Device,”. Patent Abstracts of Japan, P1237. vol. 15, No. 316, p. 119 pf JP 3-113783, MAy 15, 1991 (Aug. 13, 1991).
Bushnell , Esq. Robert E.
Habermehl James L.
Hudspeth David
Samsung Electronics Co,. Ltd.
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